Events

  • seminar
    Date:
    30 May
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    Electrosome assembly: a first look at the structural principles underlying ion channel biogenesis

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Daniel Minor
    Departments of Biochemistry & Biophysics University of California San Francisco
  • seminar
    Date:
    30 May
    2023
    Tuesday
    Hours:
    11:00
    -
    12:00

    Homogeneous (De)hydrogenative Catalysis for a Circular Economy

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Amit Kumar
    School of Chemistry, University of St. Andrews, St. Andrews, KY169ST, UK

    Abstract

    The development of sustainable methods for the closed-loop production and recycling of plastics is an important challenge of current times. Reactions based on catalytic (de)hydrogenation are atom-economic, and sustainable routes for organic transformations.1 Using the following examples, this lecture will discuss the application of homogeneous (de)hydrogenative catalysis for the synthesis and degradation of polymers to enable a circular economy: (a) synthesis of polyamides/nylons from the ruthenium catalysed dehydrogenative coupling of diamines and diols and its reverse reaction i.e. hydrogenative depolymerisation of nylons,2 (b) synthesis of polyureas from the ruthenium/manganese catalysed dehydrogenative coupling of diamines3,4 and methanol, and its reverse reaction, i.e. hydrogenative depolymerisation of polyureas (Figure 1B)5, (c) Synthesis of polyethyleneimines from manganese catalysed coupling of ethylene glycol and ethylenediamine or the self-coupling of ethanolamine,6 and (d) Synthesis of polyureas and polyurethanes from the dehydrogenative coupling of diformamides and diamines/diols and its reverse reaction i.e. hydrogenative depolymerisation of polyureas and polyurethanes to diformamides and diamines/diols.7 Some applications of some of the polymers made using dehydrogenative processes in the field of batteries will also be discussed.8
  • colloquia
    Date:
    29 May
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Erwin Reisner

    Department of Chemistry, University of Cambridge
    Title: Solar Panels for Light-to-Chemical Conversion
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Solar panels are well known to produce electricity, but they are also in early-stage development for the production of sustainable fuels and chemicals. These panels mimic plant leaves in shape and function as demonstrated for overall solar water splitting to produce green H2 by the laboratories of Nocera and Domen.1,2 This presentation will give an overview of our recent progress to construct prototype solar panel devices for the conversion of carbon dioxide and solid waste streams into fuels and higher-value chemicals through molecular surface-engineering of solar panels with suitable catalysts. Specifically, a standalone ‘photoelectrochemical leaf’ based on an integrated lead halide perovskite-BiVO4 tandem light absorber architecture has been built for the solar CO2 reduction to produce syngas.3 Syngas is an energy-rich gas mixture containing CO and H2 and currently produced from fossil fuels. The renewable production of syngas may allow for the synthesis of renewable liquid oxygenates and hydrocarbon fuels. Recent advances in the manufacturing have enabled the reduction of material requirements to fabricate such devices and make the leaves sufficiently light weight to even float on water, thereby enabling application on open water sources.4 The tandem design also allows for the integration of biocatalysts and the selective and bias-free conversion of CO2-to-formate has been demonstrated using enzymes.5 The versatility of the integrated leaf architecture has been demonstrated by replacing the perovskite light absorber by BiOI for solar water and CO2 splitting to demonstrate week-long stability.6 An alternative solar carbon capture and utilisation technology is based on co-deposited semiconductor powders on a conducting substrate.2 Modification of these immobilized powders with a molecular catalyst provides us with a photocatalyst sheet that can cleanly produce formic acid from aqueous CO2.7 CO2-fixing bacteria grown on such a ‘photocatalyst sheet’ enable the production of multicarbon products through clean CO2-to-acetate conversion.8 The deposition of a single semiconductor material on glass gives panels for the sunlight-powered conversion plastic and biomass waste into H2 and organic products, thereby allowing for simultaneous waste remediation and fuel production.9 The concept and prospect behind these integrated systems for solar energy conversion,10 related approaches,11 and their relevance to secure and harness sustainable energy supplies in a fossil-fuel free economy will be discussed.
  • seminar
    Date:
    28 May
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Studying the role of fluids in the mantle through natural samples and experiments

    Location: Sussman Family Building for Environmental Sciences
    participants: Ronit Kesel
    Institute of Earth Sciences, The Hebrew University of Jerusalem

    Abstract

    Mantle fluids are the primary carriers of key volatile elements that make the Earth’s long-term planetary habitability possible. The interaction of such volatile-rich fluids with the mantle rocks, especially the sub-cratonic lithospheric mantle leads to alteration of the mantle as well as its melting. High-density fluids encased inside diamonds are the best natural representation of mantle fluid compositions, suggesting their compositions are saline, silicic or carbonatitic. However, the origin and role in the mantle as well as their role in altering the mantle are still unclear. In my research, we approach these questions by experimentally simulating the interaction of volatile-rich fluids with mantle rocks at known pressure and temperature relevant to the mantle. Examining different mixtures of volatiles (H2O and CO2) and mantle rocks (peridotite and eclogite), we attempt to understand the origin of each type of fluid found in diamonds as well as study the effect of such interaction on the mantle chemistry and mineralogy. Compiling many experimental studies reveals that fluids ranging from silicic to low-Mg carbonatitic are formed in systems of eclogite+H2O+CO2, the more CO2 in the system, the more carbonatitic the fluid is. Fluids ranging from low-Mg carbonatitic to high-Mg carbonatitic in nature are the results of the formation of fluids in the peridotite-H2O-CO2 system. The more CO2 in the system, the more high-Mg carbonatitic the fluid composition is. These results suggest that the various fluids found in the mantle result from changes in the bulk composition of the mantle rocks. The mantle rocks are significantly affected during percolation of such fluids through them. For example, experimentally interacting silicic fluid with peridotite demonstrated the formation of various metasomatic peridotites as a function of pressure and temperature, composing of amphibole and mica. The mineral assemblages, chemistry, and P-T conditions in the experiments are similar to those found in metasomatic xenoliths from Kimberly, South Africa, and surrounding localities.
  • seminar
    Date:
    23 May
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    Advances of Liquid Biopsy Diagnostics and Structural Models in the Development of Data-Driven AI in Future Hospitals

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Milana Frenkel-Morgenstern
    Azrieli Faculty of Medicine Bar-Ilan University
  • colloquia
    Date:
    22 May
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Eberhard K. U. Gross

    Fritz Haber Center for Molecular Dynamics, HUJI, Jerusalem
    Title: Ultrafast processes and the challenge of decoherence
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    A prominent goal of present-day condensed-matter physics is the design of electronic devices with ever faster switching times. As an example I will present the optically induced spin transfer between magnetic sublattices, the so-called OISTR effect, which allows the switching of magnetic textures on the scale of a femto-second or less. This effect was first predicted with real-time TDDFT and later confirmed in many experiments. To create from this effect a real-world device on has to face the problem of decoherence, i.e. the phenomenon that quantum systems tend to lose their quantumness due to interactions with the environment. For electrons, the principal source of decoherence is the non-adiabatic interaction with nuclear degrees of freedom, i.e. with an “environment” that cannot be removed. In fact, the paradigm of electronic-structure theory where electrons move in the static Coulomb potential of clamped nuclei, while useful in the ground state, is an idealization hardly ever satisfied in dynamical processes. Non-adiabaticity, i.e. effects of the coupled motion of electrons and nuclei beyond the Born-Oppenheimer approximation are found everywhere. In this lecture, the exact factorization will be presented as a universal approach to understand and, ultimately, control non-adiabatic effects, in particular decoherence, from an ab-initio perspective.
  • seminar
    Date:
    21 May
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Determining past lake temperatures in saline lake systems using fluid inclusions: an example from the Dead Sea

    Location: Sussman Family Building for Environmental Sciences
    participants: Niels Brall
    The Hebrew University of Jerusalem

    Abstract

    In recent decades, various temperature proxies have been developed and further established in the scientific community, at both low and high accuracy, however, not every method can be applied without restriction to all minerals or rocks. Evaporitic rocks, for example, are abundant chemical sediments at the Earth's surface that are deposited from supersaturated brines in marine, terrestrial, and lacustrine environments. Halite is the most abundant rock-forming mineral in this group, which during crystal formation entraps tiny water droplets (fluid inclusions, FIs) that store the chemical composition of the parent brine at a specific pressure-temperature dependent density. Such FIs are therefore excellent records of the original physicochemical conditions of the source brine. Brillouin spectroscopy (BS) is a novel laser-based technique that uses density fluctuations in FIs to directly measure entrapment temperatures and thus the initial brine temperature during crystal growth. In this seminar, the BS method will be introduced and two application cases will be presented using salt layers from the Dead Sea which were deposited during two interglacial periods. In addition to the basic principles, both the recommended sampling strategy and pitfalls along with associated limitations will be presented. The conclusion will be that the salt layers commonly deposited in the Dead Sea basin consist of two types that formed preferentially in summer (coarse-grained crystals) and winter (fine-grained crystals), which is mainly controlled by the degree of salt saturation of the lake water. Furthermore, it will be shown how (1) lake bottom temperatures have fluctuated seasonally (summer/winter), and that (2) paleo temperature trends can be reconstructed for an entire halite layer that was deposited during holomictic periods in the Dead Sea basin. This method is particularly promising for evaporites that formed near the surface if the material has not been affected by external processes such as tectonic burial/uplift, erosion, or mineral replacement.
  • seminar
    Date:
    21 May
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    “ Programmatic and Deep Learning Analysis Pipelines for 4D-STEM Materials Science Experiments”

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Colin Ophus
    Lawrence Berkeley National Laboratory, Berkeley

    Abstract

    Scanning transmission electron microscopy (STEM) is one of the most popular materials science methods to characterize the structure and chemistry of nanoscale samples, owing to its high resolution and many flexible operating modes. In a conventional STEM experiment, we focus the electron beam down to a probe from nanometer to sub-angstrom scale, and scan it over the sample surface while recording diffracted signals which are transmitted through the specimen. STEM can also record analytic signals such as x-rays generated by the electron beam to measure composition, or energy loss of the transmitted electrons to probe the electronic structure of samples. Conventional STEM imaging detectors experiments produce only a few intensity values at each probe position, but modern high-speed detectors allow us to measure a full 2D diffraction pattern, over a grid of 2D probe positions, forming a four dimensional (4D)-STEM dataset. These 4D-STEM datasets record information about the local phase, orientation, deformation, and other parameters, for both crystalline and amorphous materials. 4D-STEM datasets can contain millions of images and therefore require highly automated and robust software codes to extract the target properties. In this talk, I will introduce our open source py4DSTEM analysis toolkit, and show how we use these codes to perform data-intensive studies of material properties over functional length scales. I will also demonstrate some applications of modern machine learning tools, to perform measurements on electron diffraction patterns where property signals have been scrambled by multiple scattering of the electron beam.
  • seminar
    Date:
    15 May
    2023
    Monday
    Hours:
    11:00
    -
    12:00

    KENDREW LECTURE: Computational Structural Biology in the Era of Deep Learning

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. John Moult
    Institute of Bioscience and Biotechnology Research Department of Cell Biology and Molecular Genetics University of Maryland
  • seminar
    Date:
    14 May
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Projecting the impacts of climate change on human society

    Location: Sussman Family Building for Environmental Sciences
    participants: Ram Fishman
    Tel Aviv University
  • seminar
    Date:
    10 May
    2023
    Wednesday
    Hours:
    11:00
    -
    12:00

    "Simulations for materials in energy"

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Nuria Lopez
    Institute of Chemical Research of Catalonia (ICIQ)

    Abstract

    Finding new materials for the conversion of CO2 into useful products is a complex task. Simulations can provide mechanistic and stability insights trying to accelerate the process. In my talk I will present the different degrees of complexity that we try to address in the simulations and which are the major challenges in the field.
  • colloquia
    Date:
    8 May
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Hideki Kandori

    Department of Frontier Materials, Nagoya Institute of Technology, Japan
    Title: Animal and Microbial Rhodopsins
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Rhodopsins are photoreceptive membrane proteins containing a retinal chromophore in animals and microbes. Animal and microbial rhodopsins possess 11-cis and all-trans retinal, respectively, and undergo isomerization into all-trans and 13-cis retinal by light. While animal rhodopsins are G protein coupled receptors, the function of microbial rhodopsins is highly divergent, including light-driven ion pumps, light-gated ion channels, photosensors, and light-activated enzymes. Microbial rhodopsins have been the main tools in optogenetics. Function of rhodopsins starts in 10-15 sec, and activation of rhodopsins occurs in the protein environment that has been optimized during evolution (1015 sec). We thus need various methods to understand these events of 30 orders of magnitude in time. We have studied molecular mechanism of rhodopsins by use of spectroscopic methods. Using ultrafast spectroscopy, we showed the primary event in our vision being retinal photoisomerization. In rhodopsins, photoisomerization of retinal, the shape-changing reaction, occurs even at 77 K. Using low-temperature infrared spectroscopy, we detected protein-bound water molecules of rhodopsins before X-ray crystallography. Detailed vibrational analysis provided structural information such as our color discrimination mechanism. I will talk about our spectroscopic study of animal and microbial rhodopsins. Recent unexpected findings such as unusual isomerization pathways and temperature effects are also presented.
  • seminar
    Date:
    7 May
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Determining the age of the Kalahari Group, Southern Africa, using complex solutions for cosmogenic isotope concentrations

    Location: Sussman Family Building for Environmental Sciences
    participants: Ari Matmon
    The Hebrew university of Jerusalem
  • seminar
    Date:
    2 May
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    Conspiring with the Enemy: A Unique Mechanism in Class A JDPs Stabilizes Oncogenic p53 Mutants

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Guy Zoltsman
    Dept. of Chemical & Structural Biology Weizmann Institute
  • seminar
    Date:
    30 April
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Soft Matter and Biomaterials Seminar: Cytoskeletal dynamics generate active liquid-liquid phase separation.

    Location: Perlman Chemical Sciences Building
    participants: Dr. Alexandra Tayar
    Dept. Chemical and Biological Physics, WIS

    Abstract

    Liquid-Liquid phase separation (LLPS) has been of fundamental importance in the assembly of thermally driven materials and has recently emerged as an organizational principle for living systems. Biological phase separation is driven out of equilibrium through complex enzyme composition, chemical reactions, and mechanical activity, which reveals a gap in our understanding of this fundamental phenomenon. Here we study the impact of mechanical activity on LLPS. We design a DNA-based LLPS system coupled to flows through molecular motors and a cytoskeleton network. Active stress at an interface of a liquid droplet suppressed phase separation and stabilized a single-phase regime well beyond the equilibrium binodal curve. The phase diagram out of equilibrium revealed a 3-dimensional phase space that depends on temperature and local molecular activity. Similar dynamics and structures are observed in simulations, suggesting that suppression of liquid phase separation by active stress is a generic feature of liquid phase separation.
  • seminar
    Date:
    30 April
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Oceanic Internal Gravity Waves: sources, sinks, and interactions with the eddy field. 

    Location: Sussman Family Building for Environmental Sciences
    participants: Roy Barkan
    Tel Aviv University

    Abstract

    The global oceanic overturning circulation and the transport of heat and dissolved gases are strongly controlled by upper ocean turbulent mixing that is driven by the breaking of internal gravity waves (IWs). Understanding the life cycle of oceanic IWs, from generation to dissipation, is therefore crucial for improving the representation of ocean mixing in climate models, which do not resolve the IW field.  Oceanic IWs are observed to have a continuous energy distribution across spatial and temporal scales – an internal wave continuum – despite being forced primarily at near-inertial and tidal frequencies at large scales. The formation of the IW continuum and the associated energy transfer to dissipative scales have been traditionally attributed to wave-wave interactions and to Doppler shifting of wave frequencies by currents. Here, we provide evidence from realistic numerical simulations that oceanic eddies rapidly diffuse storm-forced wave energy across spatiotemporal scales, thereby playing a dominant role in the formation of the IW continuum and the corresponding spatiotemporal distribution of energy dissipation. We further demonstrate that winds can play an important role in damping oceanic IWs through current feedback.  This results in a substantial reduction in wind power input at near inertial frequencies and a net energy sink for internal tides.
  • seminar
    Date:
    27 April
    2023
    Thursday
    Hours:
    11:00
    -
    12:00

    Activation and arrest of thermal pressurization in localized faults

    Location: Sussman Family Building for Environmental Sciences
    participants: Nir Badt
    The University of Pennsylvania

    Abstract

    Thermal Pressurization (TP) is expected to be a dominant frictional weakening mechanism during earthquakes. However, due to experimental limitations there is a lack of direct evidence for the activation of TP in controlled laboratory conditions and most of our knowledge is derived from field studies and theoretical predictions. We present experiments performed by a rotary-shear apparatus where TP is activated in localized faults in Frederick diabase under constant normal stress of 50 MPa, confining pressure of 45 MPa and initial pore water pressure of 25 MPa. We show that by changing the permeability of the host rock we can control the shear stress drop during a TP event in the experimental fault. The TP events are short-lived in bare-surface faults as the opening of existing fractures around the fault plane drains the excess pore fluid. Wider, gouge-filled faults show more persistent frictional weakening, but at a slower rate, which is attributed to the compressibility of the gouge. In addition, we test the effects of transient fault dilation on the duration of a TP event through an expansion of the prevailing TP model, using a one-dimensional numerical simulation. We conclude that dynamic changes to the hydraulic diffusivity around the fault plane and persistent fault dilation, due to geometrical irregularities, are the most likely mechanisms to arrest TP during an earthquake.
  • seminar
    Date:
    24 April
    2023
    Monday
    Hours:
    14:00
    -
    15:00

    Approaching non-equilibrium: from machine learning to non-adiabatic dynamics

    Location: Perlman Chemical Sciences Building
    participants: Dr. Sergei Tretiak
    Theoretical Division & Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory

    Abstract

    Machine learning (ML) became a premier tool for modeling chemical processes and materials properties. For instance, ML interatomic potentials have become an efficient alternative to computationally expensive quantum chemistry simulations. In the case of reactive chemistry designing high-quality training data sets is crucial to overall model accuracy. To address this challenge, we develop a general reactive ML interatomic potential through unbiased active learning with an atomic configuration sampler inspired by nanoreactor molecular dynamics. The resulting model is then applied to study five distinct condensed-phase reactive chemistry systems: carbon solid-phase nucleation, graphene ring formation from acetylene, biofuel additives, combustion of methane and the spontaneous formation of glycine from early-earth small molecules. In all cases, the results closely match experiment and/or previous studies using traditional model chemistry methods. Altogether, explosive growth of user-friendly ML frameworks, designed for chemistry, demonstrates that the field is evolving towards physics-based models augmented by data science. I will also overview some applications of Non-adiabatic EXcited-state Molecular Dynamics (NEXMD) framework developed at several institutions. The NEXMD code is able to simulate tens of picoseconds photoinduced dynamics in large molecular systems. As an application, I will exemplify ultrafast coherent excitonic dynamics guided by intermolecular conical intersections. Here X-ray Raman signals are able to sensitively monitor the coherence evolution. The observed coherences have vibronic nature that survives multiple conical intersection passages for several hundred femtoseconds at room temperature. These spectroscopic signals are possible to measure at XFEL facilities and our modeling results allow us to understand and potentially manipulate excited state dynamics and energy transfer pathways toward optoelectronic applications. References: 1. N. Fedik, R. Zubatyuk, N. Lubbers, J. S. Smith, B. Nebgen, R. Messerly, Y. W. Li, M. Kulichenko, A. I. Boldyrev, K. Barros, O. Isayev, and S. Tretiak “Extending machine learning beyond interatomic potentials for predicting molecular properties” Nature Rev. Chem. 6, 653 (2022). 2. G. Zhou, N. Lubbers, K. Barros, S. Tretiak, B. Nebgen, “Deep Learning of Dynamically Responsive Chemical Hamiltonians with Semi-Empirical Quantum Mechanics,” Proc. Nat. Acad. Sci. USA, 119 e2120333119 (2022) 3. S. Zhang, M. Z. Makos, R. B. Jadrich, E. Kraka, B. T. Nebgen, S. Tretiak, O. Isayev, N. Lubbers, R. A. Messerly, and J. S. Smith “Exploring the frontiers of chemistry with a general reactive machine learning potential,” (2023) https://chemrxiv.org/engage/chemrxiv/article-details/6362d132ca86b84c77ce166c 4. A. De Sio, E. Sommer, X. T. Nguyen, L. Gross, D. Popović, B. Nebgen, S. Fernandez-Alberti, S. Pittalis, C. A. Rozzi, E. Molinari, E. Mena-Osteritz, P. Bäuerle, T. Frauenheim, S. Tretiak, C. Lienau, “Intermolecular conical intersections in molecular aggregates” Nature Nanotech. 16, 63 – 68 (2021). 5. V. M. Freixas, D. Keefer, S. Tretiak, S. Fernandez-Alberti, and S. Mukamel, “Ultrafast coherent photoexcited dynamics in a trimeric dendrimer probed by X-ray stimulated-Raman signals,” Chem. Sci., 13, 6373 – 6384 (2022).
  • colloquia
    Date:
    24 April
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Thomas R. Ward

    Department of Chemistry, University of Basel
    Title: Artificial Metalloenzymes for in vivo Catalysis: Challenges and Opportunities
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Artificial metalloenzymes (ArMs) have attracted increasing attention in the past two decades as attractive alternatives to either homogeneous catalysts or enzymes. Artificial metalloenzymes result from anchoring a catalytically competent abiotic metal cofactor within a host protein, Figure. The resulting ArMs combine attractive features of both homogeneous- and bio-catalysts. Importantly, they enable access to new-tonature reactions in a cellular environment. Relying on a supramolecular anchoring of an organometallic cofactor in various protein scaffolds, we have optimized the performance of ArMs for sixteen different reactions, Figure. Following a general introduction to the underlying principles of ArMs, this talk will highlight our recent progress in engineering and evolving such hybrid catalysts for olefin metathesis, C–H activation, hydroamination, and allylic substitution. A particular emphasis will be set on performing catalysis in a cellular environment.
  • seminar
    Date:
    18 April
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    Structural Biology Response to Biomedical Threats

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Wladek Minor
    Department of Molecular Physiology and Biological Physics University of Virginia
  • colloquia
    Date:
    17 April
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Alex Zunger

    Renewable and Sustainable Energy Institute (RASEI), University of Colorado, Boulder
    Title: Polymorphous networks of intrinsic local motifs in crystals
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Predicting properties of crystals and molecules via quantum theory of matter generally requires knowing (A) the nature of electronic interactions in the system, and (B) where atoms and various moments are (“structure”). Some of the historical failures to predict basic effects in ‘Quantum Materials’ were often tracked back to the need to improve our understanding of (A), such as accounting for ‘strong electron correlation’. Examples include Mott insulators; mass enhancement in superconductors; metal-insulator transitions in oxides, or even the quantitative underestimation of predicted band gaps of cubic Halide Perovskites. This talk explores a different resolution of the aforementioned conflicts with experiment in terms of hidden structure (B) above. This include configurations of magnetic moments or electric dipole moments, not only in the ordered ground states, but also in paramagnetic and paraelectric phases, and in nonmagnetic cubic phases of halide perovskites, all considered previously to be ‘featureless phases. Importantly, such ‘Quantum Texture’ can be predicted theoretically by minimization of the constrained internal energy, even before temperature sets in. It thus represents intrinsic tendencies to lower energy by breaking symmetry. Using such polymorphous networks in band theory explains Mott physics without correlation as well as Halide Perovskites before dynamics. This highlights the importance of experimental observation of distributions of local symmetries, distinct from the global average crystallographic symmetries.
  • seminar
    Date:
    16 April
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Protein Phase Transitions

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Tuomas Knowles
    Dept. of Chemistry, Cavendish Laboratory, University of Cambridge

    Abstract

    Proteins are the fundamental building blocks of life. They form high performance materials and carry out cellular functions. They are able to fulfil these roles by assembling together to form sophisticated structures and architectures, which in many cases extend to mesoscopic liquid or solid phases. This talk focuses on understanding the transitions between these phases, their fundamental material properties and the way that the modulate biological function and malfunction. I will then discuss two areas opened up by the control of protein assembly. I will first focus on the understanding of the mechanism of protein aggregation and the discovery of molecules that can ameliorate malfunctioning protein self-assembly in a range of age-associated disease states. I will then outline some of our efforts to control protein self-assembly to form silk-inspired sustainable materials
  • seminar
    Date:
    2 April
    2023
    Sunday
    Hours:
    14:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof Prineha Narang
    UCLA

    Abstract

    In this talk, I will present theoretical and computational chemistry approaches to describe excited-states in quantum matter, and predicting emergent states created by external drives. Understanding the role of such light-matter interactions in the regime of correlated electronic systems is of paramount importance to fields of study across chemical and condensed matter physics, and ultrafast dynamics1. The simultaneous contribution of processes that occur on many time and length-scales have remained elusive for state-of-the-art calculations and model Hamiltonian approaches alike, necessitating the development of new methods in computational chemistry. I will discuss our work at the intersection of ab initio cavity quantum-electrodynamics and electronic structure methods to treat electrons, photons and phonons on the same quantized footing, accessing new observables in strong light-matter coupling. Current approximations in the field almost exclusively focus on electronic excitations, neglecting electron-photon effects, for example, thereby limiting the applicability of conventional methods in the study of polaritonic systems, which requires understanding the coupled dynamics of electronic spins, nuclei, phonons and photons. With our approach we can access correlated electron-photon and photon-phonon dynamics2–7, essential to our latest work on driving quantum materials far out-of-equilibrium to control the coupled electronic and vibrational degrees-of-freedom 8–19. In the second part of my talk, I will demonstrate how the same approach can be generalized in the context of control of molecular quantum matter and quantum transduction. As a first example, I will discuss a cavity-mediated approach to break the inversion symmetry allowing for highly tunable even-order harmonic generation (e.g. second- and fourth-harmonic generation) naturally forbidden in such systems. This relies on a quantized treatment of the coupled light-matter system, similar to the driven case, where the molecular matter is confined within an electromagnetic environment and the incident (pump) field is treated as a quantized field in a coherent state. When the light-molecule system is strongly coupled, it leads to two important features: (i) a controllable strong-coupling-induced symmetry breaking, and (ii) a tunable and highly efficient nonlinear conversion efficiency of the harmonic generation processes 20–22. Both of these have implications for molecular quantum architectures. Being able to control molecules at a quantum level gives us access to degrees of freedom such as the vibrational or rotational degrees to the internal state structure. Finally, I will give an outlook on connecting ideas in cavity control of molecules with quantum information science.
  • seminar
    Date:
    2 April
    2023
    Sunday
    Hours:
    11:00

    Global warming accelerates soil heterotrophic respiration

    Location: Sussman Family Building for Environmental Sciences
    participants: Alon Nissan
    ETH Zurich

    Abstract

    Carbon efflux from soils is the largest terrestrial carbon source to the atmosphere, yet it remains one of the most uncertain fluxes in the Earth’s carbon budget. A dominant component of this flux is heterotrophic respiration, influenced by several environmental factors, most notably soil temperature and moisture. We developed a mechanistic model from micro to global scale to explore how changes in soil water content and temperature affect soil heterotrophic respiration. Simulations, laboratory measurements, and field observations validate the new approach. Estimates from the model show that heterotrophic respiration has been increasing since the 1980s at a rate of about 2% per decade globally. Using future projections of surface temperature and soil moisture, the model predicts a global increase of about 40% in heterotrophic respiration by the end of the century under the worst-case emission scenario, where the Arctic region is expected to experience a more than two-fold increase, driven primarily by declining soil moisture rather than temperature increase.  
  • seminar
    Date:
    2 April
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Fluorescent nucleosides, nucleotides and oligonucleotides

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Yitzhak Tor
    University of California San Diego
  • seminar
    Date:
    29 March
    2023
    Wednesday
    Hours:
    11:00
    -
    12:00

    Emerging research landscape of altermagnetism

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Tomas Jungwirth
    Institute of Physics, Czech Academy of Sciences, Czech Republic School of Physics and Astronomy, University of Nottingham, UK

    Abstract

    Magnetism is one of the largest, most fundamental, and technologically most relevant fields of condensed-matter physics. Traditionally, two elementary magnetic phases have been distinguished - ferromagnetism and antiferromagnetism. The spin polarization in the electronic band structure reflecting the magnetization in ferromagnetic crystals underpins the broad range of time-reversal symmetry-breaking responses in this extensively explored and exploited type of magnets. By comparison, antiferromagnets have vanishing net magnetization. Recently, there have been observations of materials in which strong time-reversal symmetry-breaking responses and spin-polarization phenomena, typical of ferromagnets, are accompanied by antiparallel magnetic crystal order with vanishing net magnetization, typical of antiferromagnets [1]. A classification and description based on spin-symmetry principles offers a resolution of this apparent contradiction by establishing a third distinct elementary magnetic phase, dubbed altermagnetism [2]. We will start the talk with an overview of the still emerging unique phenomenology of this unconventional d-wave (or higher even-parity wave) magnetic phase, and of the wide array of altermagnetic materials. We will then show how altermagnetism can facilitate a development of ultra-fast and low-dissipation spintronic information technologies, and can have impact on a range of other modern areas of condensed matter physics and nanoelectronics. References [1] L. Šmejkal, A. H. MacDonald, J. Sinova, S. Nakatsuji, T. Jungwirth, Nature Reviews Mater. 7, 482 (2022). [2] L. Šmejkal, J. Sinova & T. Jungwirth, Phys. Rev. X (Perspective) 12, 040501 (2022).
  • seminar
    Date:
    29 March
    2023
    Wednesday
    Hours:
    11:00
    -
    12:00

    Emerging research landscape of altermagnetism

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Tomas Jungwirth
    Institute of Physics, Czech Academy of Sciences

    Abstract

    Magnetism is one of the largest, most fundamental, and technologically most relevant fields of condensed-matter physics. Traditionally, two elementary magnetic phases have been distinguished - ferromagnetism and antiferromagnetism. The spin polarization in the electronic band structure reflecting the magnetization in ferromagnetic crystals underpins the broad range of time-reversal symmetry-breaking responses in this extensively explored and exploited type of magnets. By comparison, antiferromagnets have vanishing net magnetization. Recently, there have been observations of materials in which strong time-reversal symmetry-breaking responses and spin-polarization phenomena, typical of ferromagnets, are accompanied by antiparallel magnetic crystal order with vanishing net magnetization, typical of antiferromagnets [1]. A classification and description based on spin-symmetry principles offers a resolution of this apparent contradiction by establishing a third distinct elementary magnetic phase, dubbed altermagnetism [2]. We will start the talk with an overview of the still emerging unique phenomenology of this unconventional d-wave (or higher even-parity wave) magnetic phase, and of the wide array of altermagnetic materials. We will then show how altermagnetism can facilitate a development of ultra-fast and low-dissipation spintronic information technologies, and can have impact on a range of other modern areas of condensed matter physics and nanoelectronics. References [1] L. Šmejkal, A. H. MacDonald, J. Sinova, S. Nakatsuji, T. Jungwirth, Nature Reviews Mater. 7, 482 (2022). [2] L. Šmejkal, J. Sinova & T. Jungwirth, Phys. Rev. X (Perspective) 12, 040501 (2022).
  • seminar
    Date:
    28 March
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    Intestinal mucin is a chaperone of multivalent copper

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Nava Reznik
    Fass Lab Dept. of Chemical & Structural Biology Weizmann Institute
  • seminar
    Date:
    26 March
    2023
    Sunday
    Hours:
    11:00

    From Oceanic Blooms to Dust Events: Exploring the Activity and Survival Strategies of Bioaerosols

    Location: Sussman Family Building for Environmental Sciences
    participants: Naama Lang-Yona
    Technion, Haifa
  • seminar
    Date:
    23 March
    2023
    Thursday
    Hours:
    10:00
    -
    11:00

    Chemical and Biological Physics Guest Seminar

    Location: Perlman Chemical Sciences Building
    participants: Prof Maxim Sukharev
    Arizona State University

    Abstract

    Molecular plasmonics has been a hot topic for the past several years. At the heart of the primary interest in plasmonics is the strong electromagnetic field localization at resonant frequencies corresponding to surface plasmon-polariton modes. Thanks to riveting advancements in nanofabrication technologies, we have achieved nearly 1 nm spatial resolution (and in some cases even below that!) and are able to fabricate a wide variety of nanosystems ranging from nanoparticles of various shapes to metasurfaces comprised of periodic arrays of nanoparticles and/or nanoholes of any imaginable geometry. Such systems have recently emerged as new platforms for strong light-matter interactions. Combined with molecular ensembles, these constructs exhibit a remarkable set of optical phenomena ranging from the exciton-plasmon strong coupling to the second harmonic generation altered by molecular resonances. In this talk I will discuss both linear and nonlinear optical properties of plasmonic materials coupled to quantum emitters of various complexity. I will also introduce a newly developed computational approach that can be used to efficiently simulate a large number of complex molecules driven by electromagnetic radiation crafted at plasmonic interfaces.
  • colloquia
    Date:
    20 March
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Erez Braun

    Department of Physics, Technion
    Title: Animal morphogenesis as a dynamical phase transition
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    A remarkable hallmark of animal morphogenesis is the convergence of this dynamic process into a stereotypic viable organism. The current picture relies on biochemical patterning with a well-defined hierarchy of forward-driven processes. I will discuss the nature of developmental processes, arguing that morphogenesis is robust due to the synergistic dynamics of mechanical, biochemical and electrical processes. Hydra regeneration provides a unique experimental setup, allowing us to develop a physics framework for this pattern-formation process. We demonstrate that an external electric field can be tuned to drive morphogenesis in whole-body Hydra regeneration, backward and forward, around a critical point in a controlled manner. We show that calcium (Ca2+) fluctuations underlie Hydra morphogenesis. Utilizing an external electric field as a control, we study these fluctuations at the onset of morphogenesis showing their universal characteristics and their associations with the morphological dynamics. Our analysis shows that the Hydra's tissue resides near the onset of bistability and the external control modulates the dynamics near that onset. It paints a picture of morphogenesis analogous to a dynamical phase transition.
  • seminar
    Date:
    19 March
    2023
    Sunday
    Hours:
    11:00

    Groundwater-surface water interactions in coastal environments and the impact of hydrogeological changes.

    Location: Sussman Family Building for Environmental Sciences
    participants: Anner Paldor
    Tel Aviv University
  • seminar
    Date:
    16 March
    2023
    Thursday
    Hours:
    15:00
    -
    16:00

    Joint Chemical and Biological Physics and Molecular Chemistry and Materials Science Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof Michael Pittelkow
    University of Copenhagen, Denmark

    Abstract

    I will discuss the synthesis and properties of a range of aromatic-, anti-aromatic- and helical aromatic molecules.1 The talk will feature molecules with 'weird' magnetic properties, helical chirality and abnormal reactivity due to close proximity. I will discuss some of the unusual properties (and some of the very trivial and unsurprising properties) of these large well-defined conjugated molecules. I will describe the journey from fundamental studies of the acid-mediated oligomerization of simple 1,4-benzoquinones to the controlled synthesis of heterocyclic [8] circulenes (featuring an antiaromatic planar cyclooctatetraene) and even a larger planar [9] helicene. In the simplest picture two units of benzoquinone gives a dihydroxy-dibenzofuran + water, thus forming a new furan ring. This sets up a 1+1=3 ‘logic’ for elongation of the -system. The synthetic methodology has allowed us to prepare a range of fully conjugated helicenes, including the longest known optically resolved chiral [13] helicenes. The helicenes and circulenes have been explored in a range of properties including as the blue fluorescent component in OLEDs, as G-quadruplex binding ligands and in fundamental studies of antiaromaticity and chirality.
  • seminar
    Date:
    15 March
    2023
    Wednesday
    Hours:
    15:00
    -
    16:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof Per Hedegard
    Niels Bohr Institute, University of Copenhagen

    Abstract

    The so-called CISS phenomenon refers to the observation, that when electrons are transported through a chiral molecule, as e.g. a helix, then they will emerge spin polarized even though when entering they are not spin polarized. Often this effect is observed using magnetized leads. Remarkably, it seems that many experiments break the Onsager reciprocity principle. Onsager’s principle is very deep and depends on very few assumptions about the system - mainly about behavior under time reversal. I will present a possible solution to this conundrum
  • seminar
    Date:
    15 March
    2023
    Wednesday
    Hours:
    11:00
    -
    12:00

    Towards resolving dynamics of molecular machines using time-resolved cryo-EM

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Rouslan Efremov
    VIB-VUB Center for Structural Biology Belgium
  • seminar
    Date:
    14 March
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    Structure-based prediction of protein-protein and protein compound interactions on a proteome-wide scale

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Barry Honig
    Columbia University
  • colloquia
    Date:
    13 March
    2023
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. J.L. Billinge

    Applied Physics & Applied Mathematics, Columbia University
    Title: From saving pharmaceuticals to saving priceless historical artefacts via saving the planet: understanding nanostructure with x-rays and algorithms.
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Nanoparticles and nanostructures are at the heart of next generation technological solutions in sustainable energy, effective new pharmaceuticals and environmental remediation. A key to making progress is to be able to understand the nanoparticle structure, the arrangements of atoms in the nanoparticles and nanoscale structures. Also critical is understanding the distribution of the nanoparticles and how they change in time as devices run and reactions take place. We use advanced x-ray, neutron and electron scattering methods to get at this problem. I will talk about these methods and show some recent success-stories in the fields of sustainable energy, pharmaceuticals and cultural heritage preservation. However, I will also discuss the fundamental limitations on our ability to extract information from the data and how we are now turning to machine learnging and articifical intelligence techniques to give more insights.
  • seminar
    Date:
    12 March
    2023
    Sunday
    Hours:
    11:00

    TBA

    Location: Sussman Family Building for Environmental Sciences
    participants: Boswell Wing
    Colorado
  • seminar
    Date:
    12 March
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Soft Matter and Biomaterials: “The Secret Ultrafast Motions of Protein Nanomachines”

    Location: Perlman Chemical Sciences Building
    participants: Prof. Gilad Haran
    Dept. Chemical and Biological Physics, WIS

    Abstract

    Multiple proteins function as nanomachines, and carry out multiple specific tasks in the cell by alternating chemical steps with conformational transitions. Single-molecule FRET spectroscopy is a powerful tool for studying the internal motions of proteins. In recent years, we have been using this technique to study a range of protein machines, surprisingly finding in each case microsecond-time-scale internal dynamics. What is the role of these fast motions in the much-slower functional cycles of these machines?
  • colloquia
    Date:
    6 March
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Jacob Sagiv

    Dept. of Molecular Chemistry and Materials Science
    Title: Interfaces teach us New Lessons in Chemistry & Physics: Metal Organic Quasinanowires fabricated by Interfacial Electron Beam Lithography exhibit Puzzling Electrical Conduction
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    A 47 years-old story that started with the discovery of an ordered organosilane monolayer that assembles itself on various polar surfaces has evolved into an ongoing “research thriller” craving explanations for a series of unusual experimental findings. Using interfacial electron beam lithography – a novel approach to chemical surface patterning that allows fabrication of hybrid inorganic-organic monolayer structures spanning nano-to-macroscale dimensions, we fabricate metal (Ag)-monolayer quasinanowires on silicon with micrometer-centimeter lengths and planned layouts that exhibit puzzling electrical conduction. Depending on the composition and structure of the quasinanowire and the nature of the silicon support, the room-temperature resistivities of such surface entities may vary between that of a practical insulator to some extremely low values. These findings defy rationalization in terms of conventional electrical conduction mechanisms. Interfacial systems with characteristic structural features akin to those of our quasinanowires have, however, been proposed in both the exciton model of high-temperature superconductivity (Little, Ginzburg, 1964-70) and that of superconductivity by the pairing of spatially separated electrons and holes (Lozovik & Yudson, 1976). While gathering additional clues that might shed light on the mystery of our thriller, these theoretical predictions spur us to seek the shining light at the end of the tunnel...
  • seminar
    Date:
    5 March
    2023
    Sunday
    Hours:
    00:00

    TBA

    Location: Sussman Family Building for Environmental Sciences
    participants: Ann Pearson
  • seminar
    Date:
    28 February
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    Fast and Processive Artificial Molecular Motors and Rotors Made of DNA

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Eyal Nir
    Department of Chemistry Ben-Gurion University
  • seminar
    Date:
    28 February
    2023
    Tuesday
    Hours:
    11:00
    -
    12:00

    Intrinsically Chiral and Multimodal Click Chemistry

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Han Zuilhof
    Department of Organic Chemistry, Wageningen University, The Netherlands

    Abstract

    Click chemistry has revolutionized many facets of the molecular sciences, with the realization of reactions that are ‘‘modular, wide in scope, give very high yields, generate only inoffensive byproducts that can be removed by nonchromatographic methods and are stereospecific”. Yet surprisingly little attention has been given to the development of intrinsically chiral click reactions (potentially enantiospecific, rather than ‘only’ enantioselective due to chiral auxiliary groups), while the modularity of many click reactions is best compared to one-dimensional LEGO. Of course, much could be done within the constraints – hence forementioned revolution – but it drove attention towards an extension of available click chemistries. Kolb, H. C.; Finn, M.; Sharpless, K. B., Click chemistry: diverse chemical function from a few good reactions. Angew. Chem. Int. Ed. 2001, 40, 2004-2021. The talk will focus on the resulting investigations in the field of S(VI) exchange chemistry, with specific emphasis on two fields: a) the development of the intrinsically enantiospecific click reactions and their use to e.g. make synthetic polymers with 100% backbone chirality that combine stability & degradabbility, and b) the development of multimodular click chemistry and single-polymer studies by a combination of AFM, TEM, scanning Auger microscopy
  • colloquia
    Date:
    27 February
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Herbert Waldmann

    Max Planck Institute of Molecular Physiology
    Title: Pseudo Natural Products – Chemical Evolution of Natural Product Structure
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Natural products have provided inspiration for chemical biology and medicinal chemistry research. Their success raises the fundamental question whether the particular structural and biological properties of natural products can be translated to structurally less demanding compounds, readily accessible by chemical synthesis and yet still endowed with pronounced bioactivity. The lecture will describe a logic for the simplification of natural product structure by means of “Biology Oriented Synthesis” (BIOS) and its evolution into the “Pseudo Natural Product” (PNP) concept. Pseudo-natural products can be regarded as the human-made equivalent of natural product evolution, i.e. the chemical evolution of natural product structure. Application of natural product inspired compound collections designed and synthesized following these principles in cell-based phenotypic assays and subsequent identification of the cellular target proteins demonstrate that the BIOS and PNPs may enable innovation in both chemical biology and medicinal chemistry research.
  • seminar
    Date:
    26 February
    2023
    Sunday
    Hours:
    00:00

    TBA

    Location: Sussman Family Building for Environmental Sciences
    participants: Holly Michael
  • seminar
    Date:
    22 February
    2023
    Wednesday
    Hours:
    11:00
    -
    12:00

    Strong light-exciton interactions in 2D semiconductors

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Itai Epstein
    School of electrical engineering, TAU

    Abstract

    The remarkable properties of excitons in transition-metal-dichalcogenides (TMDs), together with the ability to readily control their charge carriers, have attracted a significant amount of interest in recent years. Despite the atomic dimensions of the hosting 2D semiconductors, TMD excitons exhibit strong interaction with light, both in absorption and photoemission processes, and practically dominate the optical response of these 2D materials. In this talk, I will introduce several approaches for achieving extremely strong light-exciton interactions. First, by optical and electrical manipulation of TMD excitons inside a van der Waals heterostructure cavity [1], second, via the formation of highly-confined, in-plane exciton polaritons [2], and third, through the realization of valley-polarized hyperbolic exciton polaritons [3]. These enhanced light–exciton interactions may provide a platform for studying excitonic phase-transitions, quantum nonlinearities and the enablement of new possibilities for 2D semiconductor-based optoelectronic devices. [1] I. Epstein et al, "Near-unity Light Absorption in a Monolayer WS2 Van der Waals Heterostructure Cavity", Nano letters 20 (5), 3545-3552 (2020). [2] I. Epstein et al, "Highly Confined In-plane Propagating Exciton-Polaritons on Monolayer Semiconductors", 2D Materials 7, 035031 (2020). [3] T. Eini, T. Asherov, Y. Mazor, and I. Epstein, "Valley-polarized Hyperbolic Exciton Polaritons in Multilayer 2D Semiconductors at Visible Frequencies", Phys. Rev. B 106, L201405 (2022).
  • seminar
    Date:
    19 February
    2023
    Sunday
    Hours:
    11:00

    flow, deformation and, reaction in porous media: the Coupling of Flow and Elastic Expansion in Porous Media

    Location: Sussman Family Building for Environmental Sciences
    participants: Yaniv Edery
  • seminar
    Date:
    19 February
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Soft Matter and Biomaterials Seminar

    Location: Perlman Chemical Sciences Building
    participants: Prof. Avi Schroeder
    Dept. Chemical Engineering, Technion

    Abstract

    Medicine is taking its first steps toward patient-specific cancer care. Nanoparticles have many potential benefits for treating cancer, including the ability to transport complex molecular cargoes, including siRNA and protein, as well as targeting specific cell populations. The talk will explain the fundamentals of nanotechnology, from ‘barcoded nanoparticles’ that target sites of cancer where they perform a programmed therapeutic task. Specifically, liposomes diagnose the tumor and metastasis for their sensitivity to different medications, providing patient-specific drug activity information that can be used to improve the medication choice. The talk will also describe how liposomes can be used for degrading the pancreatic stroma to allow subsequent drug penetration into pancreatic adenocarcinoma and how nanoparticle’ biodistribution and anti-cancer efficacy are impacted by the patient’s sex and, more specifically, the menstrual cycle. The evolution of drug delivery systems into synthetic cells, programmed nanoparticles that have an autonomous capacity to synthesize diagnostic and therapeutic proteins inside the body, and their promise for treating cancer and immunotherapy, will be discussed. References: 1) Theranostic barcoded nanoparticles for personalized cancer medicine, Yaari et al. Nature Communications, 2016, 7, 13325 2) Collagenase nanoparticles enhance the penetration of drugs into pancreatic tumors, Zinger et al., ACS Nano, 13 (10), 11008-11021, 2019 3) Targeting neurons in the tumor microenvironment with bupivacaine nanoparticles reduces breast cancer progression and metastases, Science Advances, Kaduri et al., 7 (41), eabj5435, 2021 4) Nanoparticles accumulate in the female reproductive system during ovulation affecting cancer treatment and fertility, Poley et al., ACS nano, 2022
  • seminar
    Date:
    14 February
    2023
    Tuesday
    Hours:
    11:00
    -
    12:00

    Photoinduced regioselective functionalization of arenes at proximal and distal sites

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Debabrata Maiti
    Department of Chemistry & IDP in Climate Studies, IIT Bombay

    Abstract

    Over years’ transition metal-catalyzed C-H activation has propelled the field of organic synthesis for the construction of structurally complex and diverse molecules in resource-economical fashion. In this context, non-directed C-H activation has gained unprecedented attention for attaining region-specific C-H functionalizations in a step-economic mode. Unlike traditional Fujiwara-Moritani reaction, this approach relies on ligand assistance and thus uses arene as the limiting reagent. However, all existing non-directed C-H functionalizations utilize high thermal energy to induce the functional group which eventually put the regioselectivity at stake. In addition, use of super stoichiometric costly silver salts to regenerate the catalyst produces unwanted metal waste. In aid of developing a more sustainable and environmentally benign approach, we have established a photoredox catalytic system by a merger of palladium/organo-photocatalyst(PC) which forges highly regeiospecific C-H olefination of diverse arenes and heteroarenes. Visible light nullifies the requirement of silver salts and thermal energy in executing “region-resolved” Fujiwara-Moritani reaction.
  • colloquia
    Date:
    13 February
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Jacob Sagiv

    Molecular Chemistry and Materials Science Department
    Title: TBD
    Location: Gerhard M.J. Schmidt Lecture Hall
  • seminar
    Date:
    12 February
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    “Life at Interfaces- Challenges and Opportunities in the Miniaturization of Bioinspired Robots”

    Location: Perlman Chemical Sciences Building
    participants: Dr. Bat-El Pinchasik
    School of Mechanical Engineering, Faculty of Engineering, TAU
  • seminar
    Date:
    7 February
    2023
    Tuesday
    Hours:
    11:00
    -
    12:00

    From Spin Materials to Electron Transfer Catalysis

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Swadhin K Mandal
    Department of Chemical Sciences, Indian Institute of Science Education and Research, Kolkata

    Abstract

    The major concerns about industrially used catalytic systems today are: i) the high cost of catalysts; ii) the toxicity of heavy transition metals; iii) difficulties in removing trace amounts of toxic-metal residues from the desired product; and, finally, iv) rare transition metal depletion, which does not meet the requirement of sustainable development. Developing environmentally friendly catalysts is an excellent option in this regard. Naturally, the most recent catalyst development trend heralded a new era of metal-free catalysis or catalysts based on earth-abundant, nontoxic, and low-cost metals. This talk will go over our recent advances [1-4] in using small molecules to systematically mimic transition metal-based catalysis. We designed electron transfer catalysis using the smallest polycyclic odd alternant hydrocarbon, phenalenyl (PLY)-based molecules, which was inspired by a completely different field of molecular spin materials [5]. This talk will focus on how to avoid transition metals when performing various cross-coupling catalysis.
  • seminar
    Date:
    5 February
    2023
    Sunday
    Hours:
    11:00

    Forecasting surface weather and storm tracks at one-month leads: role of the stratosphere and the Madden Julian Oscillation

    Location: Sussman Family Building for Environmental Sciences
    participants: Chaim Garfinkel
    The Hebrew University of Jerusalem

    Abstract

    The traditional approach to weather forecasting on one- to two-week timescales utilizes weather forecasting models, but on timescales longer than two weeks, the value of deterministic (or ensemble-based probabilistic) forecasts weakens. This is due to the presence of chaotic variability in the atmosphere. Yet certain modes of variability in the climate system have timescales longer than this two-week threshold, and the key to longer-scale prediction is to take advantage of these modes when they open up windows of opportunity. By understanding the impacts of these modes of variability on surface weather, the potential for improved forecasts on a monthly timescale can be demonstrated and eventually realized.  Two such classes of modes of variability are stratospheric variability (both in the tropical and polar stratosphere) and tropical tropospheric variability (e.g. the Madden-Julian Oscillation and El Nino). For example, both polar stratospheric sudden warmings and the Madden-Julian Oscillation have been shown to influence European and Mediterranean weather, but it is unclear (1) what mechanism(s) underlie these connections, (2) how far in advance the impacts can be predicted, (3) what governs the magnitude of the surface impact, and (4) how well models capture these connections. This talk will review progress made towards addressing these issues over the past several years in my group.
  • seminar
    Date:
    2 February
    2023
    Thursday
    Hours:
    14:00

    Silver mines, the rise of money and the advent of democracy

    Location: Sussman Family Building for Environmental Sciences
    participants: Prof. Francis Albarède
    École Normale Supérieure de Lyon, France

    Abstract

    Over the last 2½ millenia, the world economy depended on prevailing currencies: the Athenian owl (530- 168 BCE), the Roman denarius (211 BCE-250 AD), the Spanish piece-of-eight (16th to 18th C), and today the US dollar. These reference monies were accepted everywhere and all, at least in the beginning, were made of silver. What is so special about this metal? Silver is useless and rare, but still abundant enough to match the wealth of nations and of their long-distance trade. Silver ores are associated with rare and recent tectonic environments, the Mediterranean world, notably the periphery of the Aegean Sea and Southern Iberia, and the American cordillera, Peru and Mexico. In contrast, they were markedly scarce in South and East Asia. After the virtual destruction of soils by the Anatolian farmers at the end of the Bronze Age, the Near and Middle East societies depended almost exclusively on the agriculture of Egypt and Mesopotamia. The Late Bronze Age collapse (ca. 1200 BCE) corresponded to the migration of Greek people and resulted in the annihilation of all the empires outside of the flood plains. Silver by weight was nevertheless used to save populations from famine and trade wheat, barley and copper. Military innovations, hoplites and their phalanx, were, with silver mines, the main resources of the Greeks. Mercenaries received their wages in silver, notably through the tributes exacted in silver by the Achaemenid (Persion) kings. By minting silver, the returning Greek mercenaries emerged as strong middle classes . They soon claimed their share of the power, toppled the tyrants, and installed democracy in many poleis from Greece and Southern Italy. Modern economics teaches us that egalitarian distribution of wealth is unfortunately unstable and this case is well illustrated by Syracuse. At the beginning of the common era, the Roman Empire found itself the owner of centuries of silver extracted from Greece and from Iberia. This bullion was used to buy luxury products, frankincense from Arabia, spices and cotton from India, ivory and precious wood from Africa. Leakage of silver towards the Indian Ocean was so strong that coins were quickly debased by copper and by 250 AD most of the silver had been lost. The progressive replacement of silver by a bimetallic system, gold for the rich and bronze for the working class, progressively fractured the society and ushered the brutal Middle Age regimes. Silver famine had finally destroyed the democratic ideal of the Greeks. This is food for thought as disappearing mining resources may severely affect our current vision of societies.
  • seminar
    Date:
    1 February
    2023
    Wednesday
    Hours:
    11:00
    -
    12:00

    M.Sc thesis defense: “Fermi-polaron description of excitonic scattering processes in layered systems from first principles”

    Location: Perlman Chemical Sciences Building
    participants: Guy Voscoboynik
    M.Sc student of Dr. Sivan Refaely Abramson

    Abstract

    Layered materials exhibit unique charge and energy transfer characteristics, making them promising candidates for emerging photophysical and photochemical applications, and particularly in energy conversion and quantum information science. In two-dimensional systems, spatial confinement in a certain dimension causes reduced dielectric screening and enhanced Coulomb interaction compared to bulk materials. Upon light excitation, the relaxation processes of the charge and energy carriers, as well as their rearrangement in the lateral plane, allow for unique and structure-specific interaction dynamics of the electrons and holes in these systems and of their bound states - neutral and charged excitons. In particular, these dimensionality effects induce strong exciton-electron and exciton-hole interactions in doped or gated systems, where optical excitations coexist alongside electronic excitations. These interactions dominate the exciton decay and diffusion and introduce bound three-particle states in such systems. A many-particle theoretical picture of the formation and propagation of these states is crucial for proper tracking and understanding of the interaction pathways, crystal momentum effects, the involved particle-particle coupling and their relation to the underlying structure, dimensionality, and symmetry.
  • seminar
    Date:
    31 January
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    Chemical Evolution: From Origins of Life to Biotechnology

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Moran Frenkel-Pinter
    Institute of Chemistry The Hebrew University of Jerusalem
  • seminar
    Date:
    31 January
    2023
    Tuesday
    Hours:
    11:00

    Chemical and Biological Physics Guest Seminar

    Location: Perlman Chemical Sciences Building
    participants: Prof Tahei Tahara
    Molecular Spectroscopy Laboratory, Riken, Japan
  • colloquia
    Date:
    30 January
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Tahei Tahara

    Molecular Spectroscopy Laboratory, RIKEN, Japan
    Title: Microsecond Structural Dynamics of Protein, DNA and RNA Revealed by Two-Dimensional Fluorescence Lifetime Correlation Spectroscopy (2D FLCS)
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Single-molecule spectroscopy, combined with fluorescence resonance energy transfer, has been intensively utilized for studying the structural dynamics of protein, DNA, and RNA. However, observation of the dynamics on the microsecond timescale is challenging due to the low efficiency of collecting photons from a single molecule. To realize quantitative investigations of structural dynamics with a sub-microsecond time resolution, we developed new single-molecule spectroscopy, i.e., two-dimensional fluorescence lifetime correlation spectroscopy (2D FLCS). In this 2D FLCS, we use a high-repetition short pulse laser for photoexcitation and analyze the correlation of the fluorescence lifetime from the donor of a FRET pair. The obtained information is represented in the form of a 2D fluorescence lifetime correlation map using the inverse Laplace transform. 2D FLCS can visualize the structural dynamics of complex molecules in the equilibrium condition with a sub-microsecond resolution at the single-molecule level. In this presentation, I will talk about the principle of 2D FLCS and its application to the study of the structural dynamics of protein, DNA, and RNA, in particular, the most recent study on the folding/unfolding dynamics of an RNA riboswitch. Based on the observed microsecond folding dynamics, we proposed the molecular-level mechanism for transcription control by the riboswitch.
  • seminar
    Date:
    29 January
    2023
    Sunday
    Hours:
    11:00

    Insolation Forcing and Eastern Mediterranean aridity: Evidence from the Dead Sea and implications for climate projections

    Location: Sussman Family Building for Environmental Sciences
    participants: Yochanan Kushnir
    Lamont-Dohert Earth Observatory Columbia University

    Abstract

    The Mediterranean region stands out among other subtropical regions in its projected drying response to the global rise in atmospheric greenhouse gas concentrations. This drying trend has already emerged out of the normal, random climate variability in the sensitive Eastern Mediterranean (EM) region. To better understand the dynamical mechanisms responsible for this regional sensitivity, we turn to past protracted EM drying states during warm geological epochs. A unique view of the historical and pre-historical hydroclimate of the EM-Levant has been gleaned from the continued study of the sedimentary and geochemical record left by the lakes that filled the tectonic basin of the Dead Sea. We revisit the Late Quaternary sediment record retrieved during the 2010-2011 Dead Sea Deep Drilling Project (DSDDP). The sediments clearly indicate that the Levant was drier during past warm interglacials than during the adjacent glacials but nonetheless experienced large variations in the intensity of the regional aridity. During each interglacial, extended thick deposits of salts accumulated at the Lake bottom, during millennia of significant regional aridity and severely reduced Mediterranean rains. These dry states were interrupted by extended wet intervals, fed by rains that were supplied by a blend of tropical and Mediterranean moisture. To understand the underlying causes of the EM-Levant interglacial hydroclimate variations, we put the Dead Sea record in the context of the Northern Hemisphere orbital insolation variations and their impact on the global climate system. We show that the changes in EM hydroclimate portrayed by the DSDDP record during the interglacials, are entirely consistent with the response of the North Atlantic Ocean and the overlying atmosphere and surrounding land areas to the changes in the latitudinal insolation gradient, as determined by climate models and evident by surface temperature proxies. This perspective provides new information regarding the dynamical processes responsible for the ongoing, greenhouse gas forced, EM drying.
  • seminar
    Date:
    25 January
    2023
    Wednesday
    Hours:
    11:00
    -
    12:00

    "Molecules in a Quantum-Optical Flask"

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Tal Schwartz
    School of Chemistry, TAU

    Abstract

    "Molecules in a Quantum-Optical Flask" When confined to small dimensions, the interaction between light and matter can be enhanced up to the point where it overcomes all the incoherent, dissipative processes. In this "strong coupling" regime the photons and the material start to behave as a single entity, having its own quantum states and energy levels. In this talk I will discuss how such cavity-QED effects can be used in order to control material properties and molecular processes. This includes, for example, modifying photochemical reactions [1], enhancing excitonic transport up to ballistic motion close to the light-speed [2-3] and potentially tailoring the mesoscopic properties of organic crystals, by hybridizing intermolecular vibrations with electromagnetic THz fields [4-5]. 1. J. A. Hutchison, T. Schwartz, C. Genet, E. Devaux, and T. W. Ebbesen, "Modifying Chemical Landscapes by Coupling to Vacuum Fields," Angew. Chemie Int. Ed. 51, 1592 (2012). 2. G. G. Rozenman, K. Akulov, A. Golombek, and T. Schwartz, "Long-Range Transport of Organic Exciton-Polaritons Revealed by Ultrafast Microscopy," ACS Photonics 5, 105 (2018). 3. M. Balasubrahmaniyam, A. Simkovich, A. Golombek, G. Ankonina, and T. Schwartz, "Unveiling the mixed nature of polaritonic transport: From enhanced diffusion to ballistic motion approaching the speed of light," arXiv:2205.06683 (2022). 4. R. Damari, O. Weinberg, D. Krotkov, N. Demina, K. Akulov, A. Golombek, T. Schwartz, and S. Fleischer, "Strong coupling of collective intermolecular vibrations in organic materials at terahertz frequencies," Nat. Commun. 10, 3248 (2019). 5. M. Kaeek, R. Damari, M. Roth, S. Fleischer, and T. Schwartz, "Strong Coupling in a Self-Coupled Terahertz Photonic Crystal," ACS Photonics 8, 1881 (2021).
  • seminar
    Date:
    24 January
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    Intrinsically disordered proteins can also exhibit millisecond conformational dynamics

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Eitan Lerner
    The Alexander Silberman Institute of Life Sciences The Hebrew University
  • seminar
    Date:
    24 January
    2023
    Tuesday
    Hours:
    12:30
    -
    13:30

    Electro-freezing of Super-Cooled Water within Electrolytic Cells

    Location: Perlman Chemical Sciences Building
    participants: Danielle Amit Awaskar
    M.Sc student of Profs. Igor Lubomirsky and Meir Lahav

    Abstract

    Ice melts at 0 [˚C], however, water can be super-cooled homogeneously down to ~-40 [˚C] without freezing. The ability to control the temperature of freezing of super-cooled water is highly important in many scientific sub-fields. Freezing can be induced at higher temperatures by the application of electric fields (known as electro-freezing). Despite the importance of the process of electro-freezing, its mechanism at the molecular level is still not fully understood. Recently, icing experiments performed by our group have demonstrated that electro-freezing comprises of the interactions of an electric field with specific ions of trigonal planar configuration, creating arm-chair hexagons that mimic the hexagons of the crystal ice. In my research, I investigated the effect of electro-freezing of super-cooled water on silver and copper electrodes. I found that the mechanism of electro-freezing of super-cooled water as induced by the silver electrodes is very complex and irreproducible. In contrast, the high icing temperature (~-4 [˚C]) on the copper (111) face is induced primarily by a mechanism of epitaxy.
  • seminar
    Date:
    22 January
    2023
    Sunday
    Hours:
    12:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr Ilya Svetlizky
    Harvard University

    Abstract

    Plastic (irreversible) deformation of crystals requires disrupting the crystalline order, which happens through nucleation and motion of topological line defects called dislocations. Interactions between dislocations lead to the formation of complex networks that, in turn, dictate the mechanical response of the crystal. The severe difficulty in atomic systems to simultaneously resolve the emerging macroscopic deformation and the evolution of these networks impedes our understanding of crystal plasticity. To circumvent this difficulty, we explore crystal plasticity by using colloidal crystals; the micrometer size of the particles allows us to visualize the deformation process in real-time and on the single particle level. In this talk, I will focus on two classical problems: instability of epitaxial growth and strain hardening of single crystals. In direct analogy to epitaxially grown atomic thin films, we show that colloidal crystals grown on mismatched templates to a critical thickness relax the imposed strain by nucleation of dislocations. Our experiments reveal how interactions between dislocations lead to an unexpectedly sharp relaxation process. I will then show that colloidal crystals can be strain-hardened by plastic shear; the yield strength increases with the dislocation density in excellent accord with the classical Taylor equation, originally developed for atomic crystals. Our experiments reveal the underlying mechanism for Taylor hardening and the conditions under which this mechanism fails.
  • seminar
    Date:
    22 January
    2023
    Sunday
    Hours:
    11:00

    Persistent and concurrent weather extremes in present and future climates

    Location: Sussman Family Building for Environmental Sciences
    participants: Kai Kornhuber
    Columbia University

    Abstract

    Recent severe summertime weather extremes in the Northern hemisphere extratropics such as the extraordinary 2021 North American Heatwave and the record-breaking floods in central Europe were in part driven by persistent circulation patterns in the tropospheric Jetstream. To what degree such circulation patterns will modulate extreme weather risk in a warming world is still uncertain and remains a highly debated topic in climate science. I will present results from recent studies that investigate physics of extraordinary extremes, future changes in weather persistence diagnosed by a feature tracking algorithm and future risks from concurrent extremes and associated impacts on crop production based on latest GGCMI-runs. A special emphasis will be placed on benchmarking the skill of CMIP5 and CMIP6 models to reproduce atmosphere dynamical mechanisms and associated extreme weather against reanalysis data short bio: Kai Kornhuber is an adjunct Associate Research Scientist at the Lamont-Doherty Earth Observatory, Columbia University in New York and a Senior Fellow on Climate Risks at the German Council on Foreign Relations. His research is concerned with physical drivers of extreme weather and climate events and associated societal impacts and risks under current and future climatic conditions. He is Founding Member of the EarthNetwork on Sustainable and Resilient Living in an Era of Increasing Disasters at Columbia’s Climate School, Co-Chair of the Compound Events Working Group at Risk-Kan, Steering Committee member of the HiWeather Project and a Co- Pi of the Project PERSEVERE within the BMBF Consortium.
  • seminar
    Date:
    22 January
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    Molecular and Cellular Dynamics Probed by High Speed Scanning Probe Microscopy

    Location: Perlman Chemical Sciences Building
    participants: Prof. Georg Fantner
    EPFL, Lausanne, Switzerland
  • seminar
    Date:
    18 January
    2023
    Wednesday
    Hours:
    14:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr Hillel Ori
    Harvard University

    Abstract

    Interfaces between systems with different properties are a common feature of Nature. However, the physics of interactions across such interfaces is often neglected. In this talk, I will focus on the case of biological tissue-tissue interfaces and show they can exhibit emergent electrical excitability, a phenomenon that has not been explored before. Using cultured cells and optical tools, I have found that interfaces between tissues with dissimilar electrophysiological properties can behave differently compared to the tissues on either side. In particular, the interface between non-excitable tissues can become excitable. Excitability of cells therefore depends on their position, not just the proteins they express. Moreover, my simulations reveal that interface excitability is extremely robust to parametric variation. I will briefly discuss the roots of this difference in the structures of the underlying dynamical systems, and will show examples of other excitable systems that can exhibit interfacial excitation, such as predator-prey dynamics and oscillating chemical reactions.
  • seminar
    Date:
    17 January
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    Rational discovery of selective chemical probes of the polyamine deacetylase HDAC10

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Aubry Miller
    Cancer Drug Development German Cancer Research Center DKFZ, Germany
  • seminar
    Date:
    16 January
    2023
    Monday
    Hours:
    14:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr Ran Tivony
    University of Cambridge

    Abstract

    Cells carefully regulate the movement of solutes across their membrane using an intricate array of interconnected transport pathways. While beneficial for mediating essential cellular activities, the abundance of complex transport pathways severely limits the elucidation of particular translocation mechanisms in live-cell studies. We alleviate this impediment by taking a reductionist approach to incorporate specific transport pathways (e.g., transport proteins) in simplified artificial cell models, using giant unilamellar vesicles (GUVs) as a biologically-relevant chassis. To gain maximal control over the bioengineering process, we developed an integrated microfluidic platform capable of high-throughput production and purification of monodispersed GUV-based cell models. Using single-vesicle fluorescence analysis, we quantified the passive permeation rate of two biologically important electrolytes, protons (H+) and potassium ions (K+), and correlated their flux with electrochemical gradient buildup across the GUV lipid bilayer. Applying similar analysis principles, we also determined the H+/K+ selectively of two archetypal ion channels, gramicidin A and outer membrane porin F (OmpF). Altogether, our results provide an insight into the transport mechanism of ions across lipid bilayers and set a framework for elucidating protein-based transport in artificial cell models.
  • colloquia
    Date:
    16 January
    2023
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Stefano Sacanna

    Department of Chemistry, New York University
    Title: Harnessing Coulombic Forces to Guide Colloidal Self-Assembly
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    From snowflakes to nanoparticle superlattices, a menagerie of complex structures emerge from simple building blocks attracting each other with Coulombic forces. On the colloidal scale, however, this self-assembly feat is not easily accomplished. Although many colloids bear an innate surface charge, their strong electrostatic attraction is not directly suitable for crystallization. Instead, particles must be finely crafted to serve as self-assembling units. In this talk, I'll show the robust assembly of crystalline materials from common suspensions of oppositely charged colloids through a generic approach which we refer to as polymerattenuated Coulombic self-assembly. I will demonstrate that, when particles are held separated at specific distances by a neutral polymer spacer, the attractive overlap between oppositely charged electrical double layers can be systematically tuned, directing particles to disperse, crystallize, or become permanently fixed on demand.
  • seminar
    Date:
    15 January
    2023
    Sunday
    Hours:
    11:00

    TBA

    Location: Sussman Family Building for Environmental Sciences
    participants: Adi Torfstein
    Hebrew University of Jerusalem
  • seminar
    Date:
    15 January
    2023
    Sunday
    Hours:
    11:00
    -
    12:00

    “Spherical polyelectrolytes and their self-assembly into colloidal crystals”

    Location: Perlman Chemical Sciences Building
    participants: Prof. Rafal Klajn
    Dept. Molecular Chemistry and Materials Science

    Abstract

    Self-assembly of inorganic nanoparticles (NPs) into ordered structures has led to a wide range of materials with unique optical, electronic, and catalytic properties. Various interactions have been employed to direct the crystallization of NPs, including van der Waals forces, hydrogen bonding, and magnetic dipolar interactions. Among them, Coulombic interactions have remained largely unexplored, owing to the rapid charge exchange between spherical NPs bearing high densities of opposite charges (superionic NPs). In this talk, I will describe a new method to assemble superionic NPs under conditions that preserve their native surface charge density. Our methodology was used to assemble oppositely charged NPs (“spherical polyelectrolytes”) into highly ordered assemblies exhibiting previously unknown morphologies.
  • seminar
    Date:
    12 January
    2023
    Thursday
    Hours:
    14:00
    -
    15:00

    GPCR structure and dynamics - Insights from Rhodopsin

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Oliver P. Ernst
    University of Toronto Canada
  • seminar
    Date:
    8 January
    2023
    Sunday
    Hours:
    11:00

    TBA

    Location: Sussman Family Building for Environmental Sciences
    participants: Dan Rabinowitz
    Tel Aviv University
  • seminar
    Date:
    5 January
    2023
    Thursday
    Hours:
    11:00
    -
    12:00

    M.Sc thesis defense: “Chiral epitaxy”: enantioselective growth of chiral semiconductor nanostructures on chiral and asymmetric surfaces.

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Maya Levy Greenberg
    M.Sc student of Prof. Ernesto Joselevich

    Abstract

    Inorganic semiconductor nanomaterials have been under extensive research for the last few decades for their fascinating optical and electronic properties. Our group demonstrated the guided growth approach for planar semiconductor nanowires (NWs), by taking advantage of the epitaxial relations between the substrate and the inorganic overlayer. Epitaxy enables one to control crystallographic orientation, growth directions, and properties of the nanostructures. Among the inorganic semiconductors, the family of chiral inorganic semiconductor nanomaterials has recently become a focal point of many studies owing to their unique behavior in condensed matter physics and their potential in spintronics and circularly polarized optoelectronics for information technology. Despite the extensive studies on the enantioselective growth of chiral crystals induced by chiral molecules, “chiral epitaxy”, namely the enantioselective growth of chiral crystals by epitaxy on chiral crystal surfaces has not yet been demonstrated. Here, we explore the interaction between intrinsically chiral inorganic semiconductor nanomaterials and various chiral and asymmetric surfaces. In one chapter, we demonstrate the enantioselective guided growth of Te NWs on a chiral plane of ReSe2. In order to determine the handedness of the NWs and the substrate, we made special modifications to a known handedness-determination STEM method, which allowed us to analyze both Te and ReSe2 structures. To the best of our knowledge, this is not just the first guided growth of Te on ReSe2, but it is also the first demonstration of enantioselective crystallization of a chiral crystal induced by its epitaxial relations with a chiral surface of a different crystal. Namely, this is the first demonstration of chiral epitaxy. In the second chapter, we study the guided growth of the chiral wide-bandgap semiconductor α-TeO2 along the asymmetric nanogrooves of annealed M-plane sapphire (α-Al2O3). The NWs show both straight and helical morphologies depending on their crystallographic orientation. This is the first demonstration of the guided growth of TeO2 NWs. In addition, this system demonstrates the formation of helical nanostructures with coherent handedness, controlled by interaction with an asymmetric substrate. All the NWs were characterized with SEM, AFM, TEM, EDS, and Raman spectroscopy. Overall, this work presents a new approach for enantioselective growth of chiral nanocrystals based on epitaxy. This gas-phase process should be suitable for a wide range of inorganic nanomaterials, and compatible with fabrication processes for integration into functional devices.
  • seminar
    Date:
    3 January
    2023
    Tuesday
    Hours:
    14:00
    -
    15:00

    The Simple QTY Code for Protein Design

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Shuguang Zhang
    MIT Media Lab USA
  • seminar
    Date:
    2 January
    2023
    Monday
    Hours:
    13:00
    -
    14:00

    M.Sc thesis defense: “Probing the Composition and Structure of the Solid Electrolyte Interphase in Na Ion Anodes via DNP- Solid State NMR”

    Location: Helen and Milton A. Kimmelman Building
    participants: Yuval Steinberg
    M.Sc student of Dr. Michal Leskes

    Abstract

    The need for affordable large scale energy storage has risen dramatically with the increase in usage of renewable energy sources. In recent years, beyond Li batteries such as Na ion batteries (SIB), gained much interest due to limited Lithium resources. However, SIBs are still far from meeting the demands in terms of electrochemical performance, rendering research on SIBs very important. During battery cycling, chemical and electrochemical processes result in the formation of an interphase between the anode and electrolyte called the solid electrolyte interphase (SEI). The effect of the SEI on electrochemical performance cannot be overstated, as its composition and structure dictate interfacial ionic transport in the battery cell. Since the SEI is very thin (10-50 nm) and is composed of disordered, organic, and inorganic phases it is extremely difficult to characterize at the atomic-molecular level. In this seminar I will present methodology developed for probing the native SEI formed in SIBs by using nuclear magnetic resonance (NMR) and signal enhanced NMR by exogenous and endogenous dynamic nuclear polarization (DNP). Employing these techniques enabled us to gain information on the chemical composition of the SEI together with important insights into the SEI’s structural gradient formed with different Na electrolytes. Correlating the compositional and structural information acquired with the SEI’s function can assist in designing SIBs with improved performance and longer lifetime.
  • seminar
    Date:
    2 January
    2023
    Monday
    Hours:
    11:00
    -
    12:00

    Graphullerene: a new form of two-dimensional carbon

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Elena Meirzadeh
    Department of Chemistry, Columbia University

    Abstract

    The two natural allotropes of carbon, diamond and graphite, are extended networks of sp3- and sp2- hybridized carbon atoms, respectively. By mixing different hybridizations and geometries of carbon, one could conceptually construct countless synthetic allotropes. In this talk, I will introduce graphullerene, a new two-dimensional superatomic allotrope of carbon combining three- and four-coordinate carbon atoms. The constituent subunits of graphullerene are C60 fullerenes that are covalently interconnected within a molecular layer, forming graphene-like hexagonal sheets. The most remarkable thing about the synthesis of graphullerene is that the solid-state reaction produces large polyhedral crystals (hundreds of micrometers in lateral dimensions), rather than an amorphous or microcrystalline powder as one would typically expect from polymerization chemistry. Similar to graphite, the crystals can be mechanically exfoliated to produce molecularly thin flakes with clean interfaces—a critical requirement for the creation of heterostructures and optoelectronic devices. We find that polymerizing the fullerenes leads to a large change in the electronic structure of C60 and the vibrational scattering mechanisms affecting thermal transport. Furthermore, imaging few-layer graphullerene flakes using transmission electron microscopy and near-field nano-photoluminescence spectroscopy reveals the existence of moiré-like superlattices. The discovery of a superatomic cousin of graphene demonstrates that there is an entire family of higher and lower dimensional forms of carbon that may be chemically prepared from molecular precursors.
  • seminar
    Date:
    1 January
    2023
    Sunday
    Hours:
    11:00

    TBA

    Location: Sussman Family Building for Environmental Sciences
    participants: Yishai Weinstein
    Bar Ilan Univrsity
  • seminar
    Date:
    27 December
    2022
    Tuesday
    Hours:
    11:15
    -
    12:15

    “Intelligentsia of Nano-Architected Hierarchical Materials”

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Julia Greer
    California Institute of Technology

    Abstract

    Creation of reconfigurable and multi-functional materials can be achieved by incorporating architecture into material design. In our research, we design and fabricate three-dimensional (3D) nano-architected materials that can exhibit superior and often tunable thermal, photonic, electrochemical, biochemical, and mechanical properties at extremely low mass densities (lighter than aerogels), which renders them useful and enabling in technological applications. Dominant properties of such meta-materials are driven by their multi-scale nature: from characteristic material microstructure (atoms) to individual constituents (nanometers) to structural components (microns) to overall architectures (millimeters and above). Our research is focused on fabrication and synthesis of nano- and micro-architected materials using 3D lithography, nanofabrication, and additive manufacturing (AM) techniques, as well as on investigating their mechanical, biochemical, electrochemical, electromechanical, and thermal properties as a function of architecture, constituent materials, and microstructural detail. Additive manufacturing (AM) represents a set of processes that fabricate complex 3D structures using a layer-by-layer approach, with some advanced methods attaining nanometer resolution and the creation of unique, multifunctional materials and shapes derived from a photoinitiation-based chemical reaction of custom-synthesized resins and thermal post-processing. A type of AM, vat polymerization, has allowed for using hydrogels as precursors, and exploiting novel material properties, especially those that arise at the nano-scale and do not occur in conventional materials. The focus of this talk is on additive manufacturing via vat polymerization and function-containing chemical synthesis to create 3D nano- and micro-architected metals, ceramics, multifunctional metal oxides (nano-photonics, photocatalytic, piezoelectric, etc.), and metal-containing polymer complexes, etc., as well as demonstrate their potential in some real-use biomedical, protective, and sensing applications. I will describe how the choice of architecture, material, and external stimulus can elicit stimulus-responsive, reconfigurable, and multifunctional response
  • colloquia
    Date:
    26 December
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. David Andelman

    School of Physics, Tel Aviv University
    Title: One hundred years of electrified interfaces: What’s new with the theories of Debye and Onsager?
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    The Poisson-Boltzmann theory stems from the pioneering works of Debye and Onsager and is considered even today as the benchmark of ionic solutions and electrified interfaces. It has been instrumental during the last century in predicting charge distributions and interactions between charged surfaces, membranes, electrodes as well as macromolecules and colloids. The electrostatic model of charged fluids, on which the Poisson-Boltzmann description rests and its statistical mechanical consequences have been scrutinized in great detail. Much less, however, is understood about its probable shortcomings when dealing with various aspects of real physical, chemical, and biological systems. After reviewing the Poisson-Boltzmann theory, I will discuss several extensions and modifications to the seminal works of Debye and Onsager as applied to ions and macromolecules in confined geometries. These novel ideas include the effect of dipolar solvent molecules, finite size of ions, ionic specificity, surface tension, and conductivity of concentrated ionic solutions.
  • seminar
    Date:
    25 December
    2022
    Sunday
    Hours:
    11:00

    Lightning, Biology, and Evolution

    Location: Sussman Family Building for Environmental Sciences
    participants: Colin Price
    Tel Aviv University

    Abstract

    Most electrical activity in vertebrates and invertebrates occurs at extremely low frequencies (ELF), with characteristic maxima below 50 Hz. The origin of these frequency maxima is unknown and remains a mystery. We propose that over billions of years during the evolutionary history of living organisms on Earth, the natural electromagnetic resonant frequencies in the atmosphere, continuously generated by global lightning activity, provided the background electric fields for the development of cellular electrical activity. In some animals, the electrical spectrum is difficult to differentiate from the natural background atmospheric electric field produced by lightning. In this talk I will present evidence for the link between the natural ELF fields and those found in many living organisms, including humans.  Furthermore, recent experiments show links between the ELF fields and photosynthesis in plants.
  • seminar
    Date:
    25 December
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    RNA-Lipid Nanoparticles 2.0: From Gene Silencing to Genome Editing

    Location: Perlman Chemical Sciences Building
    participants: Prof. Dan Peer
    Laboratory of Precision NanoMedicine, Tel Aviv University

    Abstract

    Accumulating work points out relevant genes and signaling pathways hampered in human disorders as potential candidates for therapeutics. Developing nucleic acid-based tools to manipulate gene expression, such as siRNAs, mRNA and genome editing strategies, open up opportunities for personalized medicine. Yet, although major progress was achieved in developing RNA targeted delivery carriers, mainly by utilizing monoclonal antibodies (mAbs) for targeting, their clinical translation has not occurred. In part because of massive development and production requirements and high batch-to-batch variability of current technologies, which relies on chemical conjugation. Here we present a self-assembled modular platform that enables to construct theoretically unlimited repertoire of RNA targeted carriers. The platform self-assembly is based on a membrane-anchored lipoprotein, incorporated into RNA-loaded novel, unique lipid nanoparticles that interact with the antibody Fc domain. We show that a simple switch of 8 different mAbs, redirects specific uptake of siRNAs by diverse leukocyte subsets in vivo. The platform therapeutic potential is demonstrated in an inflammatory bowel disease model, by targeting colon macrophages to reduce inflammatory symptoms, and in Mantle Cell Lymphoma xenograft model, by targeting cancer cells to induce cell death and improve survival. In addition, I will discuss novel approach for delivering modified mRNA to specific cell types in vivo utilizing this platform. I will also share some data on mRNA vaccines for COVID19 and Finally, I will share new data showing very high efficiency genome editing in glioma and metastatic ovarian cancer. This modular delivery platform can serve as a milestone in turning precision medicine feasible.
  • seminar
    Date:
    21 December
    2022
    Wednesday
    Hours:
    15:00

    Chemical and Biological Physics Guest Seminar

    Location: Perlman Chemical Sciences Building
    participants: Prof David Petrosyan
    IESL, FORTH, Greece

    Abstract

    Atoms in the highly excited Rydberg states possess unique properties, including long lifetimes and huge dipole moments, which facilitate their use in various quantum technology applications. I will discuss recent progress in quantum simulations of many-body physics with strongly-interacting Rydberg atoms and coherent interfaces of Rydberg atoms with superconducting microwave resonators and optical photons, and present some of our results in this research.
  • seminar
    Date:
    20 December
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Extracellular Matrix Mechanics in Disease States

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Joshua M. Grolman
    Materials Science and Engineering Technion - Israel Institute of Technology
  • seminar
    Date:
    18 December
    2022
    Sunday
    Hours:
    14:00
    -
    15:00

    From atomic imaging and functionalizing of inorganic 2D materials to molecular imaging of organic 2D materials

    Location: Perlman Chemical Sciences Building
    participants: Prof. Ute Kaiser
    Ulm University, Materials Science Electron Microscopy

    Abstract

    In this lecture, the theoretical and technical base for atomic imaging of defects in inorganic 2D materials in the low-voltage transmission electron microscope SALVE will be discussed. Atomic defects can significantly change the properties of the material: Using 2D-TMDs and 2D-TMPTs and corresponding heterostructures, this is shown experimentally and verified by corresponding quantum mechanical calculations. We also use the electron beam for the targeted formation of new phases in the inorganic 2D matrix. Since the interaction cross-sections of electron beam and organic 2D materials differ strongly from the inorganic case, we explore highest-resolution imaging conditions for 2D polymers and various 2D MOFs and show that there is a trend towards lower voltage TEM as well. We may conclude that low-voltage TEM and low-dimensional materials are just made for each other.
  • seminar
    Date:
    18 December
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    Structure and Dynamics of Polyelectrolyte Complex Network under Electric Field

    Location: Perlman Chemical Sciences Building
    participants: Prof. Eyal Zussman
    Dept Mechanical Engineering, Technion

    Abstract

    Electrostatic interactions between polyelectrolyte (PE) charges and dissociated counterions provide PEs with intriguing properties and significantly determine their conformation and dynamics. This research shows how weak PE chains form a global network when they are oppositely charged and how strong electric fields lead to orientational order. The development of controlled drug release and responsive structures is demonstrated by the use of ordered PE with tunable intermolecular interactions.
  • seminar
    Date:
    14 December
    2022
    Wednesday
    Hours:
    11:00
    -
    12:00

    Engineering Imaging Technologies and Discovering Biomarkers to Characterize Disease States

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Barbara S. Smith
    School of Biological and Health Systems Engineering, Arizona State University

    Abstract

    Neurodegenerative diseases are often clinically, genetically, and pathologically heterogeneous. The clinical impact of understanding heterogeneity is perhaps best observed in cancer, where subtype-specificity within diagnoses, prognoses, and treatments have had a critical impact on clinical decision making and patient outcomes. A better understanding of how mechanisms are related to or drive heterogeneity within diseases such as Amyotrophic Lateral Sclerosis (ALS), will have a direct impact on patient outcomes, with a conscious effort to move towards precision medicine and targeted therapeutics for patients, which are urgently needed. For this reason, neuroscientists and oncologists have long aspired to achieve an understanding of the mechanisms governing pathophysiology. Our interdisciplinary work integrates technologies across a wide range of fields to surpass the current barriers in understanding disease pathophysiology. This talk will highlight a series of optical and photoacoustic imaging tools as well as multi-omics analysis that have been developed and studied in Dr. Smith’s lab to address the urgent need for non-invasive cancer detection and the characterization of neurological disorders. Through this work, we aim to develop translational technologies and methodologies to better characterize, understand, and detect disease pathogenesis, beyond current capabilities.
  • colloquia
    Date:
    12 December
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Stefan Stoll

    Department of Chemistry, University of Washington
    Title: Mapping protein conformations using EPR/DEER spectroscopy
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    For many proteins, flexibility and motion form the basis of their function. In our lab, we quantify the conformational landscapes of proteins and their changes upon interaction with external effectors. Using Double Electron-Electron Resonance (DEER) spectroscopy, a form of Electron Paramagnetic Resonance (EPR) spectroscopy, we directly measure absolute distances and distance distributions between pairs of spin labels within proteins. From the data, we build quantitative structural and energetic models of the protein's intrinsic flexibility, conformational substates, and the structural changes induced by ligands and binding partners. In this talk, I present some of our recent results on the allosteric regulation of ion channels, the function of de novo designed protein switches, and novel methods for measuring protein conformations directly in their native cellular environment.
  • colloquia
    Date:
    5 December
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Robert Guy Griffin

    Department of Chemistry Francis Bitter Magnet Laboratory, MIT
    Title: Atomic Resolution Structures of Amyloid Fibrils - Ab1-42 , Ab1-40 and b2-microglobulin
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Many peptides and proteins form amyloid fibrils whose detailed molecular structure is of considerable functional and pathological importance. For example, amyloid is closely associated with the neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases. We review the macroscopic properties of fibrils and outline approaches to determining their microscopic structure using magic angle spinning (MAS) NMR with 2D and 3D dipole recoupling experiments involving spectral assignments and distance measurements. Key to obtaining high resolution is measurement of a sufficient number of NMR structural restraints (13C-13C and 13C-15N distances per residue). In addition, we demonstrate the applicability of 1H detection and dynamic nuclear polarization (DNP) to amyloid structural studies. We discuss the structures of three different amyloids: (1) fibrils formed by Ab1-42, the toxic species in Alzheimer’s, using >500 distance constraints; (2) fibrils of Ab1-40, a second form of Ab with a different structure, and (3) a structure of fibrils forned by b2-microglobulin, the 99 amino acid protein associated with dialysis related amylosis, using ~1200 constraints. Contrary to conventional wisdom, the spectral data indicate that the molecules in the fibril are microscopically well ordered. In addition, the structures provide insight into the mechanism of interaction of the monoclonal antibody, Aducanumab, directed against Ab amyloid.
  • seminar
    Date:
    4 December
    2022
    Sunday
    Hours:
    15:00

    Origin of compact exoplanetary systems

    Location: Sussman Family Building for Environmental Sciences
    participants: Raluca Rufu SwRI, Boulder

    Abstract

    One of the most surprising discoveries in exoplanet science has been the existence of compact systems of Earth to super-Earth sized planets. These multi-planet systems have nearly circular, coplanar orbits located at distances of only ∼ 0.01 − 0.1 AU, a region devoid of planets in our Solar System. Although compact systems comprise a large fraction of known exoplanetary systems, their origin remains debated. Common to all prior models of compact system origin is the assumption that infall to the stellar disk ends before planets form. However, there is growing observational, theoretical, and meteoritical evidence of the early growth of mm-sized “pebbles” during the infall phase. We propose that accretion of compact systems occurs during stellar infall. As a cloud core collapses, solids are gradually accumulated in the disk, producing favorable conditions for the formation and survival of close-in planets. A key feature of this model is that the reduced gas-to-solids ratio in the planet accretion region can allow for the formation and survival of compact systems, even with Type-I migration. Accretion within infall-supplied disks has been studied in the context of gas planet satellite origin. Formation models predict that the total mass of the satellite system during this evolution maintains a nearly constant mass ratio ∼10^−4 compared to the host planet’s mass. The maximum mass ratio of compact exoplanetary systems compared to the stellar mass are similar to those of the giant satellite system, suggesting that accretion of compact systems may be similar to regular satellite formation.
  • seminar
    Date:
    1 December
    2022
    Thursday
    Hours:
    14:00
    -
    15:00

    “Investigating the Surface Dynamics of Ions at the Anode-Electrolyte Interface using NMR Spectroscopy”

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Shakked Schwartz
    M.Sc. student of Dr. Michal Leskes

    Abstract

    High-Performance, Rechargeable Li-ion Batteries (LIBs) are key to the global transition from fossil fuels to renewable energy sources. LIBs utilizing lithium metal as the anode are particularly exciting due to their exceptional energy density and redox potential, yet their advancement is hindered by growth of metallic filaments and unstable surface layers. Efficient cationic transport, which is crucial for battery performance, largely depends on the heterogeneous and disordered interphase formed between the anode and the electrolyte during cycling. Directly observing this interphase as well as the dynamic processes involving it is a great challenge. Here we present an approach to elucidate these dynamic processes and correlate them with the corresponding interfacial chemistry, focusing on the first step of cationic transport: surface adsorption. Employing Dark State Exchange Saturation Transfer (DEST) by 7Li NMR, we were able to detect the exchange of Li-ions between the homogenous electrolyte and the heterogeneous surface layer, highlighting the hidden interface between the liquid and solid environments. This enabled determination of the kinetic and energetic binding properties of different surface chemistries, advancing our understanding of cationic transport mechanisms in Li-ion batteries. 
  • seminar
    Date:
    30 November
    2022
    Wednesday
    Hours:
    14:00
    -
    15:00

    Chemical Biology Avenues to Illuminate Chromatin Modifications and Protein-protein Interactions

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Nir Hananya
    Department of Chemistry Princeton University
  • seminar
    Date:
    29 November
    2022
    Tuesday
    Hours:
    14:00

    Chemical and Biological Physics Guest seminar

    Location: Stone Administration Building
    participants: Prof Tommaso Bellini
    Universita degli Studi di Milano

    Abstract

    We introduce a variant of SELEX in-vitro selection to study the evolution of a population of oligonucleotides starting from a seed of random-sequence DNA 50mers (our evolving individuals) and introducing selectivity by an affinity capture gel formed by beads carrying DNA 20mers of fixed sequence that act as targets (our resources). We PCR amplify the captured strands and proceed to the next generation. Because of the simplicity of the process, we could investigate what plays the role of “fitness" in this synthetic evolution process. We find that, across generations, evolution is first driven by the need of binding to the capture gel, while, on a later stages it appear dominated by the emerging of motifs related to inter-individual interactions.
  • seminar
    Date:
    27 November
    2022
    Sunday
    Hours:
    11:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr Miri Adler
    Yale University

    Abstract

    Our organs and tissues are made of different cell types that communicate with each other in order to achieve joint functions. However, little is known about the universal principles of these interactions. For example, how do cell interactions maintain proper cellular composition, spatial organization and collective division of labor in tissues? And what is the role of these interactions in tissue-level diseases where the healthy balance in the tissue is disrupted such as excess scarring following injury known as fibrosis? In this talk, I will discuss my work in developing theoretical frameworks that explore the collective behavior of cells that emerges from cell-cell communication circuits. I will present work on the cell circuit that controls tissue repair following injury and how it may lead to fibrosis. I will discuss a new approach to explore how cell interactions can be used to provide symmetry breaking and optimal division of labor in tissues, and how this approach can help to interpret complex patterns in real data. I will introduce a new concept in complex networks – network hyper-motifs, where we explore how small recurring patterns (network motifs) are integrated within large networks, and how these larger patterns (hyper-motifs) can give rise to emergent dynamic properties. Finally, I will conclude with future directions that are aimed at revealing principles that unify our understanding of different tissues.
  • seminar
    Date:
    24 November
    2022
    Thursday
    Hours:
    14:00

    Chemical and Biological Chemistry Guest Seminar

    Location: Perlman Chemical Sciences Building
    participants: Dr Dan Gorbonos
    Max Planck Institute of animal behavior

    Abstract

    How animals navigate and perform directional decision making while migrating and foraging, is an open puzzle. We have recently proposed a spin-based model for this process, where each optional target that is presented to the animal is represented by a group of Ising spins, that have all-to-all connectivity, with ferromagnetic intra-group interactions. The inter-group interactions are in the form of a vector dot product, depending on the instantaneous relative, and deformed, angle between the targets. The deformation of the angle in these interactions enhances the effective angular differences for small angles, as was found by fitting data from several animal species. We expose here the rich variety of trajectories predicted by the mean-field solutions of the model, for systems of three and four targets. We find that depending on the arrangement of the targets the trajectories may have an infinite series of self-similar bifurcations, or have a space-filling property. The bifurcations along the trajectories occur on "bifurcation curves'', that determine the overall nature of the trajectories. The angular deformation that was found to fit experimental data, is shown to greatly simplify the trajectories. This work demonstrates the rich space of trajectories that emerge from the model.
  • seminar
    Date:
    24 November
    2022
    Thursday
    Hours:
    11:00
    -
    12:00

    M.Sc thesis defense: "Self-Integrating Memories Based on Guided Nanowires"

    Location: Helen and Milton A. Kimmelman Building
    participants: Omri Ron
    M.Sc student in Prof. Ernesto Joselevich's group

    Abstract

    Neuromorphic computing designs have an important role in the modern ‘big data’ era, as they are suitable for processing large amount of information in short time, eliminating the von Neumann (VN) bottleneck. The neuromorphic hardware, taking its inspiration from the human brain, is designed to be used for artificial intelligence tasks via physical neural networks, such as speech or image recognition, bioinformatics, visual art processing and much more. The memristor (memory + resistor), is one of the promising building blocks for this hardware, as it mimics the behavior of a human synapse, and can be used as an analog non-volatile memory. The memristor has been proven as a viable memory element and has been used for constructing resistive random access memory (RRAM) as a replacement for current VN hardware. However, the mechanism of operation and the conducting bridge formation mechanisms in electrochemical metallization memristors still require further investigation. A planar single-nanowire (NW) based memristor is a good solution for elucidating the mechanism of operation, thanks to the high localization of switching events, allowing in-situ investigation as well as post-process analysis. Our group, which has developed the guided-growth approach to grow guided planar NWs on different substrates, has used this method to integrate guided epitaxial NWs into functional devices such as field-effect transistors (FETs), photodetectors and even address decoders. However, the guided-growth approach has not been used for creating memristors up to date. In this work, I successfully synthesized guided NWs of two metal-oxides on flat and faceted sapphire substrates – ZnO and β-Ga2O3 were successfully grown in the VLS mechanism as surface guided NWs. I successfully grew planar guided β-Ga2O3 NWs on six different sapphire substrates, for the first time as far as we know. We characterized the newly grown β-Ga2O3 NWs with SEM, TEM, EDS and Raman spectroscopy. The monoclinic NWs grew along surprising directions on the flat sapphire surfaces and I demonstrated a new mode of growth – epitaxy favored growth on a faceted surface, when graphoepitaxy is also possible. I created electrochemical metallization memristors with the obtained NWs and successfully demonstrated the effect of resistive switching for β-Ga2O3 guided NW based devices. With the abovementioned achievements, we expanded the guided-growth approach on flat and faceted sapphire surfaces, and opened the opportunity for creating surface guided-NW based neuromorphic hardware.
  • seminar
    Date:
    23 November
    2022
    Wednesday
    Hours:
    11:00
    -
    12:00

    The Role of Active Encapsulation in Perovskite Solar Cells

    Location: Perlman Chemical Sciences Building
    participants: Prof. Shaibal Sarkar
    at Department of Energy Science and Engineering, IIT Bombay

    Abstract

    From a perovskite photovoltaic device standpoint, the Al2O3 ALD can be thought of as a thin film encapsulate to protect the underlined material from the extrinsic entities. However, as per the literature is concerned, the role of Al2O3 ALD in the perovskite photovoltaic devices is much beyond a mare passive component. This raises a severe ambiguity over the choice of surface (or interface) on which ALD needs to be done for optimized device performance, in terms of the device efficiency and stability. In my presentation, I would like to elucidate the characteristic differences between the surface limited and substrate enhanced ALD processes which is important to perovskite devices. The objective here is to discuss a unified correlation between the role of the Al2O3 ALD mechanism with the perovskite device performance by excluding popular overestimated assumption about the conformality on non-ideal surface, like perovskite or organic thin films. In addition, I would like to emphasize on the fact that how the ALD process can be used to passivate the buried interfacial defect and enhancing the VOC, PL and ELQE.
  • seminar
    Date:
    22 November
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Mechanism of virus capsid assembly and disassembly

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Uri Raviv
    Institute of Chemistry The Hebrew University of Jerusalem
  • seminar
    Date:
    22 November
    2022
    Tuesday
    Hours:
    11:00
    -
    12:00

    What is the Science behind Climate Change?

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Peter Rez
    Arizona State University Department of Physics

    Abstract

    Not a day goes by when we don’t hear about the “climate crisis”; some effects are well documented, like the rise in the average global temperature and the shrinking of the polar ice caps. Undoubtedly, carbon dioxide levels in the atmosphere have been increasing, but what does “science” say about the potential consequences? The combination of the atmosphere, oceans, cryosphere and biosphere is the ultimate non-linear coupled complex system. How well do we understand what might happen? In the first part of my talk, I shall review my exploration of the original literature to try and separate out speculation, hypothesis, results of computational models, and most significantly actual observations. In the second part of my talk, I shall discuss what will actually work to reduce carbon dioxide emissions (complete elimination or Net Zero is an impossibility). Although it has become fashionable for governments to impose mandates enshrined in laws, the only laws that matter are the laws of thermodynamics and Ohm’s law.
  • colloquia
    Date:
    21 November
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Luisa De Cola

    University of Strasbourg
    Title: Assembly or disassembly this is the question…
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Molecules that can undergo self-assembly are of great interest for the development of new materials, sensors, biolabels…. In some cases the assembly can lead to an enhancement of the emission, a change in the luminescence energy and even to unexpected biological phenomena. The talk will illustrate some of the recent results on the self-assembly of platinum complexes and their evolution in solution[1]. Some water soluble compounds where studied to follow the self-assembly even in vivo and the resulting reactivity/toxicity of such species. We employed transparent polyps, Hydra vulgaris and an extraordinary phenomenon was detected with one of the complex that showed a clear effect on pluripotent stem cell proliferation, especially at low doses. The stabilization of transient species, formed in the assembly process can be achieved using cage type structures can lead to their stabilization or even existence in solution, in a condition out of equilibrium. We recently demonstrated[2] that it is possible to entrap intermediate states of luminescent assemblies and prevent their thermodynamic evolution towards the equilibrium state. Such cages are also the carriers for important drugs do to their destruction inside cells. Their biodistribution is quite unique and they are able to escape macrophages uptake.[3] References [1] A. Aliprandi, M. Mauro, L. De Cola Nature Chem., 2016, 8, 10-15 [2] P. Picchetti, G. Moreno-Alcántar, L. Talamini, A. Mourgout, A. Aliprandi, L. De Cola J. Am. Chem. Soc. 2021, 143, 7681-7687. [3] P. Picchetti et al. ACS Nano 2021, 15, 9701–9716
  • seminar
    Date:
    20 November
    2022
    Sunday
    Hours:
    11:00

    TBA - M. Magaritz Memorial Lecture: Climate Intervention

    Location: Sussman Family Building for Environmental Sciences
    participants: David Fahey
  • seminar
    Date:
    16 November
    2022
    Wednesday
    Hours:
    11:00
    -
    12:00

    “Macrocyclic compounds for green energy device applications: recent progress on boron subnaphthalocyanines and associated hybrids”

    Location: Perlman Chemical Sciences Building
    participants: Prof. Timothy Bender
    Dept. of Chemical Engineering & Applied Chemistry, University of Toronto
  • seminar
    Date:
    15 November
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    "Synthetic Nucleic Acid Topology and Their Biological Applications”

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Yossi Weizmann
    Department of Chemistry Ben-Gurion University
  • seminar
    Date:
    15 November
    2022
    Tuesday
    Hours:
    11:00
    -
    12:00

    Redox reactivity of Ar2Ch2 (Ch = S, Se):from fundamentals to application in catalysis

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Inke Siewert
    Georg-August-Universität Göttingen, Germany

    Abstract

    Aromatic dichalcogenides exhibits a rich reductive and oxidative redox chemistry and the one and two electron reductions and oxidations of such Ar2Ch2 species appears at rather mild potentials. The successive 1e–-reductions often have very similar potentials as the one electron process results in the formation of an odd-electron bond, which stabilizes the radical anion, for example in hypothetical Ph2S2•− by about 30 kcal/mol. Inspired by the natural dithiol/disulfide 2H+/2e− couple, we investigated a 2,2′-bipyridine that is equipped with a disulfide/dithiolate unit in the backbone for storing multiple electrons and protons.[2] The synchronized transfer of electrons and protons is a critical step in many chemical and biological transformations. In particular, hydride and H atom transfer reactions are important in, for example, catalytic hydrogenation or small molecule activation reactions relevant to renewable energy storage. We examined in depth the fundamental 2e–, 2e–/2H+ and 1e–/H+ reactivity of the switch depending on the metalation. It appears that the Re compound overcomes the drawback of many metal-free hydride donors, which show a large gap between the first and second reduction process, and detrimental side reactions of the radical intermediate. Furthermore, we applied such Ar2Se2 in the anodic amination and esterification of nonactivated alkenes. Amination and esterfication reactions are of considerable importance since C–N and C–O bond motifs can be found in numerous organic compounds associated with biological, pharmaceutical, or material scientific applications. We developed versatile protocols for the electrochemical functionalization and a detailed kinetic and thermodynamic analysis gave valuable insights into the mechanism of the reaction as well as the impact of, e.g. solvent, additives, on the organocatalysis.
  • seminar
    Date:
    13 November
    2022
    Sunday
    Hours:
    14:00
    -
    15:00

    "Fgf8 dynamics and critical slowing down in somitogenesis"

    Location: Perlman Chemical Sciences Building
    participants: Prof. David Bensimon
    Chemistry and Biochemistry Department, UCLA

    Abstract

    Somitogenesis, the segmentation of the antero-posterior axis in vertebrates, is thought to result from the interactions between a genetic oscillator and a posterior-moving determination wavefront. I will introduce the current state of knowledge of that important stage in the development of vertebrate embryos. Surprisingly while the oscillator period is very sensitive to temperature changes, the size of the segments is not. I shall describe our results pertaining to the importance of the decrease in time of the Fgf8 gradient on the propagation of the wavefront and the observation that the somitogenetic period, embryo growth rate, PSM shortening rate and Fgf8 decay rate all slow down as 1/(T-Tc) with Tc=14.4°C, suggesting that critical slowing may affect the embryo metabolism resulting in a natural compensation of thermal effects on somite size.
  • seminar
    Date:
    13 November
    2022
    Sunday
    Hours:
    11:00

    Targeted observations of transient luminous events from the International Space Station during the ILAN-ES campaign

    Location: Sussman Family Building for Environmental Sciences
    participants: Yoav Yair
  • seminar
    Date:
    9 November
    2022
    Wednesday
    Hours:
    14:00
    -
    15:00

    Mechanistic impact of microsecond oligomerization on minutes/hours aggregation of huntingtin studied by NMR – relevance to potential treatment avenues for Huntington’s disease

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. G. Marius Clore
    NIH Bethesda, Maryland USA
  • seminar
    Date:
    8 November
    2022
    Tuesday
    Hours:
    09:30

    Climate change challenge and innovative approaches - from batteries to agriculture - towards a more sustainable future

    Location: Dolfi and Lola Ebner Auditorium
    participants: Steven Chu
    Stanford University
  • colloquia
    Date:
    7 November
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. R. Dean Astumian

    Department of Physics and Astronomy, University of Maine
    Title: Kinetic Asymmetry, the Neglected Ingredient in Chemical Coupling
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Chemical coupling plays the essential role in metabolism of providing a mechanism by which energy released in an exergonic chemical reaction (often ATP hydrolysis) can be used to drive a different reaction energetically uphill. Through evolution coupling has come to be used also to drive the creation of concentration gradients across membranes via membrane molecular pumps such as the Na+K+ ATPase, and to harness chemical energy to perform mechanical work via proteins known as molecular motors, the most paradigmatic of which is muscle, i.e. myosin moving along actin. Recent work on synthetic molecular machines has reinvigorated efforts, both experimental and theoretical, to better understand chemical coupling. The key idea involves a mechanism known as a Brownian motor where energy is used, not to cause forward motion but to prevent backward motion. These ratchet mechanisms, named after “Feynman’s ratchet”, and mathematically described by a non-equilibrium equality for a pumped chemical potential difference, have provided the intellectual basis for the design of synthetic molecular machines. Detailed investigations of these synthetic devices have provided several surprises regarding the mechanism by which external energy drives molecular machines, most especially highlighting the key role of kinetic asymmetry.
  • seminar
    Date:
    6 November
    2022
    Sunday
    Hours:
    14:00
    -
    15:00

    Zoom only: VISCOSITY OF DILUTE ELECTROLYTE SOLUTIONS

    Location: Perlman Chemical Sciences Building
    participants: Prof. Phillip Pincus
    Physics and Materials Departments University of California, Santa Barbara

    Abstract

    https://weizmann.zoom.us/j/97641167767?pwd=YURCbjI5VjdJZ2hmWXAwMTVCS1p3UT09 Nearly 100 years ago, Jones and Dole experimentally pointed out a puzzle associated with the incremental modification of the bulk viscosity of water induced by small concentrations of salt. The strange behavior relates to cation specificity. This puzzle remains unsolved. This talk will remind you about this problem and suggest a possible approach. I hope that I can engender some ideas from you.
  • seminar
    Date:
    6 November
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    Semiclassics: The true origins of the success of density functional theory

    Location: Perlman Chemical Sciences Building
    participants: Prof. Kieron Burke
    Department of Chemistry UC Irvine

    Abstract

    The successes and failures of approximate density functionals are due to their connection with semiclassical expansions. In the semiclassical limit, relative errors in local density approximations vanish. Carefully derived corrections to that limit have been shown to be far more accurate than our usual DFT approximations. I will discuss important new results in our 20-year-long quest to derive density functional approximations as expansions in hbar. These include both a new correction to the expansion of the exchange energy of atoms and an orbital-free calculation with sub-milli-Hartree accuracy. [1] Semiclassical Origins of Density Functionals Elliott, Peter, Lee, Donghyung, Cangi, Attila and Kieron Burke, Phys. Rev. Lett. 100, 256406 (2008). [2] Leading correction to the local density approximation for exchange in large-Z atoms Nathan Argaman, Jeremy Redd, Antonio C. Cancio, and Kieron Burke, Phys. Rev. Lett. 129, 153001 (2022). [3] Orbital-free functional with sub-milliHartree accuracy, Pavel Okun and Kieron Burke, in preparation.
  • seminar
    Date:
    25 October
    2022
    Tuesday
    Hours:
    10:00
    -
    11:00

    PRIMO - A TOOL TO ENGINEER CELLULAR MICROENVIRONMENTS

  • conference
    Date:
    15 September
    2022
    Thursday
    Hours:
    08:30
    -
    18:30

    EPScon 2022

    Location: The David Lopatie Conference Centre
  • seminar
    Date:
    14 September
    2022
    Wednesday
    Hours:
    11:00
    -
    12:00

    TBA

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. John A. Tainer
    Department of Molecular and Cellular Oncology Division of Basic Science Research The University of Texas MD Anderson Cancer Center Houston, TX
  • conference
    Date:
    11 September
    -
    12 September
    2022
    Sunday
    -
    Monday
    Hours:
    08:00

    School on Biological Physics of Cells (PhysCell2022)

    Location: Gerhard M.J. Schmidt Lecture Hall
  • seminar
    Date:
    28 August
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    “Chemistry of layered materials: graphene and beyond”

    Location: Perlman Chemical Sciences Building
    participants: Prof. Zdenek Sofer
    University of Chemistry and Technology, Prague
  • seminar
    Date:
    23 August
    2022
    Tuesday
    Hours:
    11:00
    -
    12:00

    "Ultrafast charge transfer in heterostructures of two-dimensional materials"

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Giulio Cerullo
    Department of Physics, Politecnico di Milano

    Abstract

    Heterostructures (HS) of two-dimensional materials offer unlimited possibilities to design new materials for applications to optoelectronics and photonics. In such HS the electronic structure of the individual layers is well retained because of the weak interlayer van der Waals coupling. Nevertheless, new physical properties and functionalities arise beyond those of their constituent blocks, depending on the type and the stacking sequence of layers. In this presentation we use high time resolution ultrafast transient absorption (TA) and two-dimensional electronic spectroscopy (2DES) to resolve the interlayer charge scattering processes in HS. We first study a WSe2/MoSe2 HS, which displays type II band alignment with a staggered gap, where the valence band maximum and the conduction band minimum are in the same layer. By two-colour pump-probe spectroscopy, we selectively photogenerate intralayer excitons in MoSe2 and observe hole injection in WSe2 on the sub-picosecond timescale, leading to the formation of interlayer excitons (ILX). The temperature dependence of the build-up and decay of interlayer excitons provide insights into the layer coupling mechanisms [1]. By tuning into the ILX emission band, we observe a signal which grows in on a 400 fs timescale, significantly slower than the interlayer charge transfer process. This suggests that photoexcited carriers are not instantaneously converted into the ILX following interlayer scattering, but that rather an intermediate scattering processes take place We then perform 2DES, a method with both high frequency and temporal resolution, on a large-area WS2/MoS2 HS where we unambiguously time resolve both interlayer hole and electron transfer with 34 ± 14 and 69 ± 9 fs time constants, respectively [2]. We simultaneously resolve additional optoelectronic processes including band gap renormalization and intralayer exciton coupling. Finally, we investigate a graphene/WS2 HS where, for excitation well below the bandgap of WS2, we observe the characteristic signal of the A and B excitons of WS2, indicating ultrafast charge transfer from graphene to the semiconductor [3]. The nonlinear excitation fluence dependence of the TA signal reveals that the underlying mechanism is hot electron/hole transfer, whereby a tail the hot Fermi-Dirac carrier distribution in graphene tunnels through the Schottky barrier. Hot electron transfer is promising for the development of broadband and efficient low-dimensional photodetectors. [1] Z. Wang et al., Nano Lett. 21, 2165–2173 (2021). [2] V. Policht et al., Nano Lett. 21, 4738–4743 (2021). [3] C. Trovatello et al., npj 2D Mater Appl 6, 24 (2022).
  • seminar
    Date:
    22 August
    2022
    Monday
    Hours:
    14:00
    -
    15:00

    CANCELED: Chemistry of layered materials: graphene and beyond

    Location: Perlman Chemical Sciences Building
    participants: Prof. Zdenek Sofer
    Univesity of Chemistry and Technology, Prague

    Abstract

    Canceled
  • seminar
    Date:
    17 August
    2022
    Wednesday
    Hours:
    11:00
    -
    12:00

    “Molecular Dopants and other Tools to Control Metal Halide Perovskite Systems”

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Antoine Kahn
    School of Engineering and Applied Science, Princeton
  • seminar
    Date:
    4 August
    2022
    Thursday
    Hours:
    11:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Alexey Chernikov
    TU Dresden (Technische Universitat Dresden)

    Abstract

    Coexistence of optical and electrical excitations in semiconductors has a long history of research. This scenario typically involves simultaneous presence of Coulomb-bound electron-hole pairs, known as excitons, and free charge carriers. Conceptually similar to related phenomena in the ultra cold atom gases, exciton-carrier mixtures strongly influence the properties of excited semiconductors and their response to external fields. It involves the formation of bound three-particle states known as charged excitons or trions, Fermi polarons, renormalization and screening effects, as well as the Mott-transition in the high-density regime. These phenomena offer fertile ground to merge the realms of optics and transport, motivated by the availability of excitations that are both electrically tunable and couple strongly to light. Van der Waals monolayer semiconductors and layered metal-halide perovskites recently emerged as particularly suitable platforms to study exciton-carrier mixtures due to exceptionally strong Coulomb interactions on the order of many 100’s of meV. In this talk, I will discuss a number of intriguing phenomena associated with coupling of excitons to free charge carriers in these systems. I will present experimental evidence for dressing of excited exciton states by continuously tunable Fermi sea. These quasiparticles are reminiscent of two-electron excitations of the negatively charged hydrogen ion and are subject to autoionization - a unique scattering pathway available for excited states. I will further illustrate the impact of free carriers on the exciton transport revealing non-monotonous density dependence and highly efficient propagation of charged exciton complexes. Finally, I will demonstrate electrically tunable trions in hybrid organic-inorganic semiconductors. These three-particle complexes feature unusually large binding energies combined with substantial mobility at elevated temperatures.
  • seminar
    Date:
    3 August
    2022
    Wednesday
    Hours:
    11:00
    -
    12:00

    Metal Catalyzed Carbonylation Reactions

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Howard Alper
    University of Ottawa

    Abstract

    Transition metal catalyzed carbonylation reactions of a wide range of organic compounds provide entry to some molecules of value to the pharmaceutical, commodity, and petrochemical industries. Examples to be presented include the preparation of indolizine derivatives by palladium-catalyzed oxidative alkoxycarbonylation, the synthesis of N-fused heterocycles via dearomatic carbonylation, the highly regioselective and chemoselective carbonylation of bifunctional organic reactants with haloarenes, styrenes, and alkynes. These transformations were successfully applied to the synthesis of natural products including Avenanthramide A
  • seminar
    Date:
    26 July
    2022
    Tuesday
    Hours:
    11:00
    -
    12:00

    Heterogeneity of electrocatalysts: Insights from molecular electrochemistry

    Location: Perlman Chemical Sciences Building
    participants: Prof. Lior Sepunaru
    Department of Chemistry & Biochemistry, University of California Santa Barbara

    Abstract

    Catalysis is a general process that speeds up the reaction rate without altering the process thermodynamics. It is often essential to study the kinetics of the reaction to infer the mechanism of catalysis, an insight that can help in catalyst design. However, bulk catalysis, and specifically electrocatalysis, cannot capture the inherent heterogeneity of seemingly identical catalysts. This talk aims to provide basic principles behind electrocatalysis and introduce a new way to study electrocatalysts at the single entity level. Together, we will review the latest progress in the field and conclude with future directions that can be applied to the vast majority of catalysts ranging from organic, bio, and inorganic materials.
  • seminar
    Date:
    20 July
    2022
    Wednesday
    Hours:
    14:00
    -
    15:00

    Ph.D thesis: Pushing the envelope of high field DNP-NMR methodology towards functional materials

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Asya Svirinovsky
    ph.D candidate under the supervision of Dr. Michal Leskes

    Abstract

    Functional materials are the main building blocks of advanced technologies based on energy storage and conversion systems essential for our modern life including batteries, solar cells, and heterogeneous catalysis. Improvements in materials performance and development of new materials rely on our ability to obtain structure-function correlation as well as understand degradation processes when the materials are integrated into a device. To this end, advanced analytical tools that can provide information at the atomic level are essential. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy is well suited for this task, especially when equipped with high sensitivity by Magic Angle Spinning - Dynamic Nuclear Polarization (MAS-DNP). However, to date, the majority of materials studied by MAS-DNP were non-reactive and non-conductive materials with DNP from exogenous sources of polarization such as nitroxide radicals. This approach cannot be simply extended to functional materials as the properties that stem from the material’s functionality in the device, including electrical conductivity, chemical reactivity and defects, often pose challenges in the study of the materials by DNP. In this talk I will frame the challenges associated with the application of MAS-DNP to functional materials and describe approaches to address them. Results will be presented from three ubiquitous material systems spanning a range of applications: carbon allotropes, transition metal dichalcogenides (TMDs) and metallic microstructures. We systematically investigated the deleterious effect of materials’ conductivity and formulated means to reduce the effect. We explored the feasibility of utilizing inherent unpaired electrons for endogenous DNP and applied it to probe buried phases in all-solid-state lithium-metal battery and the surface chemistry in carbons. I will show that wealth of information achieved by DNP on various functional materials, can place DNP-NMR as a preferable tool for materials scientists. Our findings are expected to apply to many other systems where functional materials are dominant, making DNP a more general technique.
  • seminar
    Date:
    20 July
    2022
    Wednesday
    Hours:
    11:00
    -
    12:00

    "Adventures in Colloidal Nanocrystal Surface Chemistry"

    Location: Perlman Chemical Sciences Building
    participants: Prof. Richard L. Brutchey
    Department of Chemistry, University of Southern California, Los Angeles

    Abstract

    Colloidal nanocrystals possess high surface area-to-volume ratios; as a result, many nanocrystal properties are heavily influenced by their surfaces. At these surfaces exist a complex interface between the inorganic solid (governed by the crystal structure and particle morphology) and organic ligands. The organic ligands play a key role in controlling nucleation and growth, passivating under-coordinated surface sites, and providing steric stabilization for solvent dispersibility. Depending on the particular application of the nanocrystal, the native organic ligands may then need to be removed or exchanged. We use a complement of NMR spectroscopic techniques to understand the nature of the nanocrystal surface and ligand binding. Then, using principles of inorganic coordination chemistry, we rationally enact ligand exchange reactions on these surfaces to maximize nanocrystal functionality. This talk will briefly discuss the surface chemistry of three different platforms. (1) I will discuss how we experimentally developed an atomistic picture of perovskite nanocrystal surface termination, and then used that information to better understand how common surface treatments can “heal” halide perovskite nanocrystal surfaces. (2) I will discuss how different -donating, L-type ligands were installed on the surface of metal phosphide nanocrystals, and how they affected the hydrogen evolving ability of these electrocatalysts. (3) I will discuss a new strategy for thermally activating metal carbide nanocrystal CO2 reduction catalysts using labile ligands that decompose at significantly lower temperatures than the native ligands. This circumvents issues commonly encountered with high-temperature thermolysis (coking) or acid treatments (etching, poisoning) that are used to activate nanocrystal catalysts.
  • seminar
    Date:
    19 July
    2022
    Tuesday
    Hours:
    12:45
    -
    13:45

    Observing disordered protein ensembles inside the cell

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Shahar Sukenik
    Dept. of Chemistry and Chemical Biology University of California
  • seminar
    Date:
    6 July
    2022
    Wednesday
    Hours:
    11:00
    -
    12:00

    “Aspects of solar cell operation and reliability in High and low dimensions”

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Jean Francois Guillemoles
    Director of CNRS, Institut Photovoltaïque d'Ile-de-France (IPVF) , Paris

    Abstract

    The development of advanced photovoltaic devices, including those that might overcome the single junction efficiency limit, as well as the development of new materials, all rely on advanced characterization methods. Among all the existing methods optically based ones are very well adapted to quantitatively probe optoelectronic properties at any stage. We here present the use of multidimensional imaging techniques that record spatially, spectrally and time resolved luminescence images. We will discuss the benefits (and challenges) of looking into energy conversion systems from high dimensions perspective and those of dimensional reduction for improved intelligibility through some examples, mostly drawn from halide perovskite materials and device. These examples will help visit questions related to efficient transport and conversion in solar cells, as well as questions related to chemical and operational stability of the devices.
  • colloquia
    Date:
    4 July
    2022
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Joerg Enderlein

    Biophysics, Georg-August-University Göttingen
    Title: Advanced Concepts of Super-Resolution Fluorescence Microscopy
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    With the advent of super-resolution microscopy, the last ~25 years have seen a revolution in optical microscopy, pushing the spatial resolution capabilities of optical microscopy towards length scales that were typically accessible only by electron microscopy. In my presentation, I will give a short overview of the different principal approaches to super-resolution microscopy. I will briefly discuss the concepts of Structured Illumination Microscopy (SIM), Stimulated Emission Depletion (STED) microscopy, and Single Molecule Localization Microscopy (SMLM). Then, I will focus on two specific techniques where our group has contributed most. The first is Image Scanning Microscopy or ISM [1-3]. This technique uses a simple combination of confocal microscopy with wide-field image detection for doubling the resolution of conventional microscopy. I will explain the physical principals behind ISM, and the various kinds of its implementation. Meanwhile, ISM has found broad and wide applications and lies behind state-of-the-art commercial systems such as the extremely successful AiryScan microscope from Carl Zeiss Jena. The second method is Super-resolution Optical Fluctuation Imaging (SOFI), which uses the stochastic blinking of emitters for overcoming the classical diffraction limit of resolution, similar to single-molecule localization microscopy, but with much relaxed demands on blinking behavior and label density [4]. The third method is Metal-Induced Energy Transfer imaging or MIET imaging [5-6]. It addresses the axial resolution in microscopy, which is particularly important for resolving three-dimensional structures. MIET is based on the intricate electrodynamic interaction of fluorescent emitters with metallic nanostructures. I will present the basic principles and several applications of this technique.
  • seminar
    Date:
    30 June
    2022
    Thursday
    Hours:
    11:00
    -
    12:00

    What you always wanted to know about nanoparticles, proteins and biomaterials, but never dared to ask

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Dr. Klaus D. Jandt
    Otto Schott Institute of Materials Research (OSIM) Friedrich Schiller University, Jena

    Abstract

    This lecture presents an overview on major research work of the Fellow’s group in the areas of polymer nanoparticles for drug delivery, control of protein adsorption on materials surfaces and protein nanofibers. In addition, the new excellence graduate school (Research Training Group) RTG 2723: Materials‐Microbe‐Microenvironments: Antimicrobial biomaterials with tailored structures and properties (M‐M‐M) funded by the German Science Foundation will be introduced. Polymer nanoparticles (PNP) became recently exceedingly popular through novel vaccination technologies but have also major potential for fighting inflammation and cancer. These drug release properties of the PNP depend on their structure. Yet, the literature reports little about the structure and the properties of most PNPs, except the chemical composition. The PNP’s crystallinity, thermal and mechanical properties are frequently ignored, even though they may play a key role in the drug delivery properties of the PNPs. Protein adsorption on biomaterials is the first process after implantation and determines much of the fate of the biomaterial, such as cell adhesion, blood coagulation or infection at the implant site. Despite decades of research, only rules of thumb exist to predict protein adsorption behavior. We present nanotechnological approaches to control protein adsorption using nanostructured semicrystalline polymers and crystal facets of TiO2. Selfassembled protein nanofibers consisting of one or more proteins, potentially allow to tailor the properties of biomaterials interfaces and to create bone mimetic structures. Finally, the new DFG‐RTG 2723: Materials‐Microbe‐Microenvironments: Antimicrobial biomaterials with tailored structures and properties (M‐M‐M) in Jena will be introduced. The aim of the RTG is to provide excellent training for approximately 40 international doctoral researchers in antimicrobial biomaterials in interdisciplinary tandem projects, connecting materials science and medical science. The RTG pursues a new strategy by developing antibiotic free biomaterials, where the antimicrobial action is based mainly on physical principles. The new RTG offers ample opportunity for fruitful cooperation and exchange with leading research institutions in Israel.
  • seminar
    Date:
    29 June
    2022
    Wednesday
    Hours:
    11:00
    -
    12:00

    Molecular design of solid catalysts

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Alexander Katz
    University of California, Berkeley

    Abstract

    This colloquium will be divided into two applications parts, dealing with synthesis of supported molecular catalysts and solid catalysts for photoprotection. In the first of these areas, we describe a mechanical approach for stabilizing supported weakly interacting active sites (i.e. those that interact non-covalently with the support) against aggregation and coalescence. We use silica as a prototypical example of a support, and an iridium pair-site catalyst incorporating bridging calixarene ligands as an active site. Atomic-resolution imaging of the Ir centers before and after ethylene-hydrogenation catalysis show the metals resisted aggregation and deactivation, remaining atomically dispersed and accessible for catalysis. When active sites are located at unconfined environments, the rate constants for ethylene hydrogenation are markedly lower compared with confining external-surface pockets [1], in line with prior observations of similar effects in olefin epoxidation catalysis [2,3]. Altogether, these examples represent new opportunities for enhancing reactivity on surfaces by synthetically controlling mechanical features of active site catalyst environments. In the second of these areas, reactive oxygen species (ROS) are associated with several human health pathologies and are invoked in the degradation of natural ecosystems as well as building materials that are used in modern infrastructure (e.g., paints and coatings, polymers, etc). Natural antioxidants such as vitamin E function as stoichiometric reductants (i.e. reaction with ROS synthesizes rancid oils). While enzymes such as superoxide dismutase working in tandem with catalase decompose decompose ROS to H2O and O2 through H2O2 as an intermediate, these enzymes are fragile and costly. Other non-stoichiometric commercial antioxidants that degrade ROS include hindered amine light stabilizers (HALS). Here, we demonstrate that cerium carbonate acts as a degradation catalyst for photogenerated ROS, and describe the performance and characterization of this new catalyst using X-ray photoelectron spectroscopy, and in comparison with HALS and stoichiometric reductants. Our results demonstrate catalytic antioxidant activity of cerium carbonate when dispersed in polymethylmethacrylate polymer. FTIR data demonstrate that a dispersion of 2 wt. % cerium carbonate within the polymer essentially stops degradation by photogenerated ROS, which otherwise cause oxidation of the polymer backbone, in the control polymer lacking cerium carbonate. Experiments with methylene blue dye in aqueous solution demonstrate that cerium carbonate decreases the rate of ROS degradation of dye, in the presence of UV irradiation and air by 16 fold. These effects become even more pronounced (over 600 fold decrease in rate of ROS dye degradation) when cerium carbonate is paired with a photoactive metal oxide. The mechanism involved in this latter case crudely mimics the enzyme tandem sequence referred to above. [1] C. Schöttle, E. Guan, A. Okrut, N. A. Grosso-Giordano, A. Palermo, A. Solovyov, B. C. Gates, A. Katz*, Journal of the American Chemical Society, J. Am. Chem. Soc. 2019, 141, 4010-4015. [2] N. A. Grosso-Giordano, C. Schroeder, A. Okrut, A. Solovyov, C. Schottle, W. Chasse, N. Marinkoyic, H. Koller, S. I. Zones, A. Katz, Journal of the American Chemical Society 2018, 140, 4956-4960. [3] N. A. Grosso-Giordano, A. S. Hoffman, A. Boubnov, D. W. Small, S. R. Bare, S. I. Zones, A. Katz, Journal of the American Chemical Society 2019, 141, 7090-7106. [4] M. K. Mishra, J. Callejas, M. Pacholski, J. Ciston, A. Okrut, A. Van Dyk, D. Barton, J. C. Bohling, A. Katz, ACS Applied Nano Materials 2021, 4, 11, 11590-11600.
  • seminar
    Date:
    28 June
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    New methods to extract knowledge on epistasis from experimental evolutionary landscapes

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Dmitry Ivankov
    Center for Molecular and Cellular Biology Skoltech University Russia
  • seminar
    Date:
    21 June
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    The love of fluorescent molecules for noble metals: Metal-induced modulation of single molecule fluorescence

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Joerg Enderlein
    Georg-August-University Goettingen, Germany
  • colloquia
    Date:
    20 June
    2022
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Uri Banin

    Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem
    Title: Coupled Colloidal Quantum Dot Molecules
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Colloidal semiconductor Quantum Dots (CQDs) containing hundreds to thousands of atoms have reached an exquisite level of control, alongside gaining fundamental understanding of their size, composition and surface-controlled properties, leading to their technological applications in displays and in bioimaging. Inspired by molecular chemistry, deeming CQDs as artificial atom building blocks, how plentiful would be the selection of composition, properties and functionalities of the analogous artificial molecules? Herein we introduce the utilization of CQDs as basic elements in nanocrystal chemistry for construction of coupled colloidal nanocrystals molecules. Focusing on the simplest form of homodimer quantum dots (QDs), analogous to homonuclear diatomic molecules, we introduce a facile and powerful synthesis strategy with precise control over the composition and size of the barrier in between the artificial atoms to allow for tuning the electronic coupling characteristics and their optical properties. This sets the stage for nanocrystals chemistry to yield a diverse selection of coupled CQD molecules utilizing the rich collection of artificial atom core/shell CQD building blocks. Such CQD molecules are of relevance for numerous applications including in displays, photodetection, biological tagging, electric field sensing and quantum technologies.
  • seminar
    Date:
    19 June
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    Impacts of the June 2021 Heat Dome on Pacific Northwest (USA) Trees and Forests

    Location: Sussman Family Building for Environmental Sciences
    participants: Chris Still
    Oregon State University

    Abstract

    Most of the Pacific Northwest (PNW, USA) and British Columbia experienced extraordinarily high air temperatures during an extreme heat wave event (“heat dome”) in late June of 2021. In many locations, alltime record high air temperatures (Tair) exceeding 40-45 °C were observed. In this talk I will present evidence of the widespread impacts of this extreme heat event. These impacts include foliar damage observed in many locations of this region, along with some tree mortality. Additionally, I will present data from dendrometers and eddy covariance towers in contrasting forest types highlighting the impacts on tree growth and ecosystem-atmosphere CO2, H2O, and energy fluxes. Better understanding the environmental drivers, biophysical and physiological mechanisms, and ecological consequences of heat damage incurred by forests is of broad relevance and societal importance.
  • seminar
    Date:
    15 June
    2022
    Wednesday
    Hours:
    10:00
    -
    11:00

    Zoom M.Sc thesis defense: The Investigation of Low-Temperature Proton Conduction in Rare- Earth- Hydroxides

    participants: Tahel Malka
    under the supervision of Prof. Igor Lubomirsky

    Abstract

    https://weizmann.zoom.us/j/95467631640?pwd=MHZBNThNQlRUeU1CM29kQXZZcGxOdz09 password:864419 Solid oxide fuel cells (SOFCs), especially proton conducting (PC)-based, and electrolyzes (SOEs), operating above 250°C, demonstrate rapid electrode kinetics, but are limited in their long term stability due to thermal stresses related to on/off cycling. Thermal stress could be reduced dramatically, for PC-SOFCs devices operating in the temperature range of 150-250°C, which would still benefit from fast electrode kinetics and would not require Pt-containing catalytic electrodes. However, a proton-conducting ceramic electrolyte, operating below 250°C hasn’t been identified yet. In this work I investigated the synthesis, preparation protocols and properties of La(OH)_3 and La_2 Ce_2 O_7 (LCO50) powder and ceramics to explore their suitability as proton conductors. Preparation of appropriate pellet samples of La(OH)_3 from the synthesized powder requires (i) elimination of the presence of carbonate oxides followed by (ii) hydration of the remaining La2O3 in boiling deionized water. Room temperature compaction of these powders into solid pellet samples requires prolonged dwell uniaxial pressure. Although the primarily protonic conductivity of the compacted sample reached only 3·10-11 S/cm at 90°C and is insufficient for practical applications; the grain boundaries are apparently not blocking, making it attractive to look for dopants that may potentially enhance the low temperature conductivity. Nominally anhydrous LCO50 has an unexpectedly high conductivity 10-11 S/cm at 110 °C, which is probably due to oxygen vacancies. LCO50 undergoes hydration with a large lattice expansion, which combined with low hydration enthalpy (5.2 kJ/mol) restricted compact crack-free sample. Hydration of LCO50 by 7.5% of the maximum possible showed to have non-blocking grain boundaries, and increases the conductivity by an order of magnitude, which has to be attributed to protonic conduction. Findings describe in this work, point that both investigated materials are promising candidates for further studies as proton conductors.
  • seminar
    Date:
    14 June
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Deep Learning Methods Reveal Structural Mechanisms of Protein-DNA Readout

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Remo Rohs
    The Department of Quantitative and Computational Biology University of Southern California
  • seminar
    Date:
    12 June
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    Biogeochemical cycling in subsurface systems

    Location: Sussman Family Building for Environmental Sciences
    participants: Dr. Maya Engel
    SLAC National Lab Stanford University

    Abstract

    Subsurface systems, such as alluvial aquifers and soils, store and govern the quality of groundwater by sustaining a unique balance of biogeochemical and hydrological processes. The complex characteristics of subsurface systems are demonstrated in both spatial and compositional sediment heterogeneities that ultimately control the rate and extent of elemental cycling. Different redox environments commonly form within the subsurface and may largely influence these cycles. Heavy metals, occurring naturally (geogenic) or as anthropogenic contaminants, are particularly sensitive to varying redox conditions, even if they are not directly redox active. In this seminar, I will show how sediment hotspots and interfaces influence elemental cycling, contaminant attenuation, and groundwater quality. I will present examples of how an alluvial aquifer system exhibiting redox heterogeneities may influence heavy metal mobility by preferential retention in fine-grained sediment lenses embedded within the coarse aquifer. Several mechanisms contribute to the retention in fine-grained sediments, and we also observe a significant impact of nitrate-rich conditions on the extent and phases of metal retention. Further, I will share our findings on the dynamic and unique composition of iron-rich colloids, detected in reducing zones of a floodplain subsurface. Our results demonstrate the presence of partially oxidized iron rich colloids in otherwise reducing conditions, thanks to a protective organic-silicon coating. The lifecycle and composition of these colloids may have direct effects on element cycling as they may serve as vectors for the transport of nutrients and organic matter into groundwater and surface water recipients. Lastly, I will present my future research visions, in a lab devoted to the study of biogeochemical heterogeneity and coupled elemental cycling under dynamic conditions.
  • seminar
    Date:
    7 June
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    On discovery and sensitivity in (photo)catalysis

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Frank Glorius
    University of Münster, Germany

    Abstract

    Catalysis is a key technology, since it allows for increased levels of selectivity and efficacy of chemical transformations. While significant progress can be made by rational design or engineered step-by-step improvements, many pressing challenges in the field require the discovery of new and formerly unexpected results. Arguably, the question “How to discover?” is at the heart of the scientific process. In this talk, (smart) screening strategies for accelerated discovery and improved reproducibility will be presented, together with new photocatalytic transformations. In addition, two other exciting areas will be addressed: N-heterocyclic carbenes (NHCs) are powerful ligands in catalysis due to their strong electron-donating properties and their ability to form very stable bonds to transition metals. In addition, they can stabilize and modify nanoparticles or flat metals surfaces, outperforming established phosphine or thiol ligands regarding structural flexibility, electron-donating properties and stability. Current research is highly interdisciplinary and focusses on the basic understanding of the binding mode, mobility and the elucidation of the impact on the surface properties. Exciting applications in materials science, heterogeneous catalysts and beyond are within reach. Biological membranes and their constituents are some of the most important and fundamental building blocks of life. However, their exact role in many essential cellular processes as well as in the development of diseases such as cancer or Alzheimer's is still not very well understood. Thus, we design, synthesize and evaluate imidazolium-based lipid analogs that can integrate into biological membranes and can be used as probes for live cell imaging or to manipulate membranes.
  • seminar
    Date:
    7 June
    2022
    Tuesday
    Hours:
    11:00
    -
    12:00

    RNA and Protein: A Match made in the Hadean

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Loren D. Williams
    Center for the Origins of Life School of Chemistry and Biochemistry Georgia Tech, Atlanta
  • colloquia
    Date:
    6 June
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Harry Anderson

    Department of Chemistry, University of Oxford
    Title: Synthesis of Molecular Wire Nanorings: Light Harvesting & Charge Delocalization
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Template-directed synthesis can be used to create π-conjugated porphyrin nanorings that are as big as proteins, with diameters ranging from 2 nm to more than 20 nm. These nanorings mimic the ultra-fast energy migration of photosynthetic light-harvesting chlorophyll arrays. They are highly redox active and they display global aromaticity in some oxidation states. For example, the 12-porphyrin nanoring is globally aromatic in its 6+ oxidation state with a Hückel circuit of 4n + 2 = 162 π electrons (diameter 5 nm). This is the largest aromatic circuit yet reported. The aromatic and antiaromatic ring currents confirm that there is long-range charge delocalization. Recent work on these systems will be presented.
  • seminar
    Date:
    2 June
    2022
    Thursday
    Hours:
    14:00
    -
    15:00

    Emerging paradigms in G protein coupled receptors (GPCRs) signaling and their implications for drug discovery

    Location: Nella and Leon Benoziyo Building for Biological Sciences
    participants: Prof. Michel Bouvier
    Institute for Research in Immunology and Cancer (IRIC) of the Université de Montréal (UdeM)
  • seminar
    Date:
    31 May
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Integrated microfluidic tools for improving biological research and medical diagnostics

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Doron Gerber
    Faculty of Life Science Bar-Ilan University
  • seminar
    Date:
    30 May
    2022
    Monday
    Hours:
    11:00
    -
    12:00

    Neutralizing antibodies against pathogenic viruses

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: KENDREW LECTURE: Prof. Pamela Bjorkman
    California Institute of Technology
  • seminar
    Date:
    29 May
    2022
    Sunday
    Hours:
    11:00

    LESSONS FROM THE DEAD SEA, THE CLOSEST MODERN ANALOG FOR DEEP EVAPORITIC BASINS

    participants: Nadav Lensky
    Geological survey of Israel

    Abstract

    Thick halite sequences are common in the Earth’s geologic record; they were accumulated in deep perennial hypersaline water bodies, saturated to halite and subjected to negative water balance. For decades, evaporites research gained insights from exploring modern shallow hypersaline environments, including the relations between the hydroclimatic forcing and the deposited halite layers. However, there is a knowledge gap in understanding limnological controls on accreted halite sequences in deep water bodies. Such water bodies rarely exist today on Earth, but were common through Earth geological history. The Dead Sea is currently the closest and probably the only modern analog for such environments. Recently, based on direct field measurements, laboratory experiments, direct numerical simulations, and sedimentological investigation, we have shown that there are fundamental differences between deposition at deep basins versus shallow basins, specifically in the seasonal to multi-annual scales and variations of halite solubility with depth. We have found that during the dry summer the epilimnion is warmer, saltier and undersaturated to halite, and that double diffusion flux delivers dissolved salt from the epilimnion into the hypolimnion, resulting in the continuously supersaturated hypolimnion and seasonally undersaturated epilimnion. Thus the stratified structure of the lake’s water column results in focusing of halite deposits into the deep parts of the basin and thinned deposits, or entirely dissolved, in the marginal parts. We further explore the role of laterally variable hydroclimatic conditions to the spatiotemporal dynamics of evaporitic deposits in a deep hypersaline waterbody. We focus on the role of diluted buoyant plume, overlaying part of the Dead Sea surface that laterally spreads from freshwater inflow. The lateral surface salinity variations results in lateral variations in evaporation, double diffusion fluxes, and hence evaporitic layer thickness. These can contribute to the study of the depositional environments of halite units throughout the geological record, following the concept of “the present as key to the past”. At the end of the talk, I will share some management ideas regarding the future of the Dead Sea.
  • seminar
    Date:
    26 May
    2022
    Thursday
    Hours:
    11:30
    -
    12:30

    Chaperoning protein aggregation diseases

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Stefan Rudiger
    Bijvoet Center for Biomolecular Research Utrecht University
  • seminar
    Date:
    26 May
    2022
    Thursday
    Hours:
    11:00
    -
    12:00

    “Modeling Photo and Bias Induced Electron transfer and transport. An ab-initio perspective on kinetics”

    Location: Perlman Chemical Sciences Building
    participants: Prof. Barry Dunietz
    Dept. Chemistry and Biochemistry, Kent State University, OH

    Abstract

    Charge transfer and transport processes through molecular interfaces are ubiquitous and of a crucial role in determining functionality of biological systems and in enabling energy conversion applications. We study computationally such processes to understand structure-function relationships at the molecular level. We will discuss studies in the following two primary fields: (1) Photovoltaic and charge transfer properties of organic semiconductors materials. (2) Charge transport through voltage-biased molecular scale bridges. Importantly we establish predictive computational scheme that addresses key challenges. Our studies are employed in conjunction with experimental efforts to design materials and applications that control and tune relevant physical properties
  • seminar
    Date:
    24 May
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Real-time monitoring of replication fork progression in single live cells

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Amir Aharoni
    Dept. of Life Sciences Ben-Gurion University
  • colloquia
    Date:
    23 May
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Dr. Nir London

    Department of Chemical & Structural Biology, WIS
    Title: Covalent Binders: From Discovery to Function
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Small molecule inhibitors and drugs that are able to form a covalent bond with their protein target have several advantages over traditional binders. While they were avoided for a long time due to concerns of specificity, in recent years they are attracting significant interest as underscored by FDA approvals of rationally designed covalent drugs, such as Ibrutinib and Afatinib. In the past few years my research team has been focused on technology development for the field of Covalent Ligand Discovery. These include: covalent virtual screening, empirical covalent fragment screening, the first reported reversible covalent targeted degraders (PROTACs), and most recently the discovery of new chemistry that enables the design of superior covalent binders. These technologies enabled the discovery of novel, potent inhibitors for several challenging targets. These inhibitors, in turn, have shed new light on the target’s biological function and represent potential therapeutic leads. I will describe our journey from the original goal of mere ‘discovery’ of covalent binders to the current challenge of functionalizing covalent binders for various applications.
  • seminar
    Date:
    22 May
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof Dave Waldeck
    University of Pittsburgh
  • seminar
    Date:
    22 May
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof Dave Waldeck
    University of Pittsburgh
  • seminar
    Date:
    19 May
    2022
    Thursday
    Hours:
    15:00
    -
    16:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Latha Venkataraman
    Columbia University

    Abstract

    Over the past decade, there has been tremendous progress in the measurement, modeling and understanding of structure-function relationships in single molecule circuits. Experimental techniques for reliable and reproducible single molecule junction measurements have led, in part, to this progress. In particular, the scanning tunneling microscope-based break-junction technique has enabled rapid, sequential measurement of large numbers of nanoscale junctions allowing a statistical analysis to readily distinguish reproducible characteristics. Although the break-junction technique is mostly used to measure electronic properties of single-molecule circuits, in this talk, I will demonstrate its versatile uses to understand both physical and chemical phenomena with single-molecule precision. I will discuss some recent experimental and analysis aimed at understanding quantum interference in single-molecule junctions. I will then show an example where molecular structure can be designed to utilize interference effects to create a highly non-linear device. Finally, I will discuss some new areas of research aiming to demonstrate that electric fields can catalyze chemical reactions.
  • seminar
    Date:
    18 May
    2022
    Wednesday
    Hours:
    14:00

    Chemical and Biological Physics Special Seminar

    Location: Perlman Chemical Sciences Building
    participants: Dmitrii E. Makarov
    Department of Chemistry and Oden Institute for Computational Engineering and Sciences University of Texas at Austin

    Abstract

    The mathematical analogy between information and thermodynamical entropy has recently led to promising developments in chemistry and physics, and information theory tools are increasingly important in chemical and biological data analysis. In this talk I will describe a few of our ideas at the intersection of physical chemistry, information theory, and computer science, with the focus on single-molecule data analysis. Single-molecule experimental studies have opened a new window into the elementary biochemical steps, function of molecular machines, and cellular phenomena. The information contained in single-molecule trajectories is however often underutilized in that oversimplified models such as one-dimensional diffusion or one-dimensional random walk are used to interpret experimental data. I will show that much finer details of single-molecule dynamics, such as conformational memory and static disorder, can be deduced from an analysis that is similar to Shannon’s analysis of printed English; in particular, this method relates conformational memory to the information-theoretical compressibility of single-molecule signals.
  • seminar
    Date:
    17 May
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    A Link Between Mitochondrial Metabolism and Ca2+ Signaling or How Coffee Enhances Learning

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Israel Sekler
    The Dept. of Physiology and Cell Biology Faculty of Health Sciences Ben-Gurion University of the Negev
  • seminar
    Date:
    17 May
    2022
    Tuesday
    Hours:
    11:00

    TBA

    participants: Avishai Abu
    The Hebrew University of Jerusalem
  • seminar
    Date:
    16 May
    2022
    Monday
    Hours:
    11:00
    -
    12:00

    Atomically Precise Chemical, Physical, Electronic, and Spin Contacts

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Paul S. Weiss
    California NanoSystems Institute and Departments of Chemistry & Biochemistry, Bioengineering, and Materials Science & Engineering, UCLA, Los Angeles, CA 90095, USA

    Abstract

    One of the key advances in nanoscience and nanotechnology has been our increasing ability to reach the limits of atomically precise structures. By having developed the “eyes” to see, to record spectra, and to measure function at the nanoscale, we have been able to fabricate structures with precision as well as to understand the important and intrinsic heterogeneity of function found in these assemblies. The physical, electronic, mechanical, and chemical connections that materials make to one another and to the outside world are critical. Just as the properties and applications of conventional semiconductor devices depend on these contacts, so do nanomaterials, many nanoscale measurements, and devices of the future. We discuss the important roles that these contacts can play in preserving key transport and other properties. Initial nanoscale connections and measurements guide the path to future opportunities and challenges ahead. Band alignment and minimally disruptive connections are both targets and can be characterized in both experiment and theory. I discuss our initial forays into this area in a number of materials systems.
  • colloquia
    Date:
    16 May
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Paul S. Weiss

    University of California, Los Angeles
    Title: Annual G.M.J. SCHMIDT MEMORIAL LECTURE
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

  • seminar
    Date:
    15 May
    2022
    Sunday
    Hours:
    12:00
    -
    13:00

    Designing multifunctional molecular crystalline materials

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Luca Catalano
    Laboratory of Polymer Chemistry, Université libre de Bruxelles

    Abstract

    Molecular crystals are supramolecules “par excellence"1 as they are macroscopic objects composed by millions of molecules periodically disposed and held together by non-covalent interactions with specific physico-chemical properties dictated by their architectures. This offers a vibrant solid-state chemistry playground to build organic solids with tailored functionalities, such as novel luminescent materials,2 solid-state molecular machines,3 and multicomponent crystals with complex topologies.4 The inherent dynamic nature of the weak intermolecular forces that are driving organic crystals self-assembly is also conferring adaptive responsiveness, e.g., mechanical reconfiguration and shape-memory effect, to this class of materials making them ideal building blocks for the design and synthesis of multifunctional crystalline systems that can be exploited as actuators, flexible single-crystalline optoelectronic devices, and self-healing materials.5
  • colloquia
    Date:
    9 May
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Rein V. Ulijn

    Advanced Science Research Center, City University of New York
    Title: Repurposing the chemistry of life for nanotechnology
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    We are interested in how functionality emerges from interactions between biomolecules, and subsequently how these functions can be incorporated into materials.1 Instead of using sequences known in biological systems, we use unbiased computational2 and experimental3 approaches to search and map the peptide sequence space for specific interactions and functions, with a focus on side chain, instead of backbone interactions. The talk will explore how to program molecular order and disorder through side chain interactions in short peptides4, and how the conformations adopted by these peptides can be exploited to regulate interfacial assembly properties, and liquid-liquid phase separation. We will discuss chemo-mechanical peptide-crystals with connected soft and stiff domains, that change their properties upon changes in hydration states.5 The last part of the talk will focus on our progress in holistic study of mixtures of molecules that individually are simple and non-functional, but as components of complex interacting systems, however, they give rise to self-organization patterns that are dictated by the environmental conditions.6 Collectively, we expect to identify insights that allow the repurposing of nature's molecules to design new functions that currently are not known in biology.
  • seminar
    Date:
    8 May
    2022
    Sunday
    Hours:
    11:00

    TBA

    participants: Nili Harnik
    Tel Aviv University
  • seminar
    Date:
    3 May
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Beyond NGS: Single-molecule epigenomics

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Yuval Ebenstein
    School of Chemistry Tel-Aviv University
  • seminar
    Date:
    3 May
    2022
    Tuesday
    Hours:
    11:00

    TBA

    participants: Mathew Henry
  • colloquia
    Date:
    2 May
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Dr. Hagen Hofmann

    Department of Chemical & Structural Biology, WIS
    Title: Probing Biomolecular Dynamics with Single-Molecule Spectroscopy
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Explaining organisms in terms of the jiggling and wiggling of atoms is a central goal in molecular biology. Yet, the dynamics of proteins with their sophisticated three-dimensional architectures exceeds the capabilities of
analytical theories. On the other
hand, intrinsically
disordered proteins are often well described by polymer theories of different flavors. However, these theories do not apply to proteins in which disorder and order mix. Combining structural biology with polymer theory is therefore required to understand such biomolecules. I will discuss how optical single-molecule spectroscopy allows us to probe the dynamics of (partially) disordered proteins and complexes from nanoseconds to milliseconds. I will show how many weak protein-protein interactions can cause rugged energy landscapes that slow-down dynamics by orders of magnitude. In the second part, I will discuss how we envision to bridge scales between molecules and cells at the example of a cellular phenotype switch that requires a dynamic interplay between proteins and DNA. While single-molecule tools to probe the kinetics of biomolecules are well developed, similar approaches to study the dynamics of cellular processes such as gene expression are scarce. In the final part of my talk I will therefore present a new approach to tackle this problem using single-particle tracking
  • seminar
    Date:
    28 April
    2022
    Thursday
    Hours:
    11:00
    -
    12:00

    “Spin-orbit coupling and Kondo resonance in Co adatom on Cu(100) surface: DFT+ED study”

    Location: Perlman Chemical Sciences Building
    participants: Prof. Alexander B. Shick
    Institute of Physics, the Czech Academy of Science, Prague

    Abstract

    The studies of magnetic atoms adsorbed on non-magnetic surfaces provide a fundamental insights into the quantum many-body phenomena at the nanoscale. They imprint non-trivial signatures in STM measurements, and can serve as a prototype for potential applications in quantum information technology. Our work aims at the investigation of the electronic structure, spin and orbital magnetic character for the Co adatom on the top of Cu(100) surface. We make use of DFT combined with exact diagonalization of the multi-orbital Anderson impurity model, including the spin-orbit coupling. For the Co atom d-shell occupation nd=8, a singlet many-body ground state and Kondo resonance are found, when the spin-orbit coupling is included in the calculations. The differential conductance is evaluated in a good agreement with the STM measurements. This comparison is the most direct way to demonstrate the validity of our theoretical approximation. Our results illustrate the very essential role which the spin-orbit coupling is playing in a formation of Kondo singlet for the multi-orbital impurity in low dimensions.
  • seminar
    Date:
    26 April
    2022
    Tuesday
    Hours:
    11:00

    TBA

    participants: Georg Wohlfahrt
    University of Innsbruck Department of Ecology
  • seminar
    Date:
    26 April
    2022
    Tuesday
    Hours:
    11:00
    -
    12:00

    Self-assembling structure and function using equilibrium and non-equilibrium statistical mechanics

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr, Matan Ya Ben Zion
    School of Physics, TAU

    Abstract

    Self-assembly and self-organization are two big challenges in the natural sciences. What are the rules governing the emergence of greater structures from unassuming elements? Does statistical-mechanics restrict their complexity? Biochemical processes can shape highly specific structures and function on the macro-scale using only molecular information. Although stereochemistry has been a central focus of molecular sciences since Pasteur, its synthetic province has been restricted to the nanometric scale. In my talk, I will describe how to propagate molecular information to self-assemble free-form architectures on the micron-scale and beyond. These architectures are a thousand times greater than their constituent molecules yet have a preprogrammed geometry and chirality. I will then show how to animate such synthetic microstructures into bacteria-like micro-swimmers. Previous artificial microswimmers relied on an external chemical fuel to drive their propulsion which restricted their operational concentration as they competed locally over fuel. I will demonstrate how to use material science and physical chemistry to self-assemble fuel-free micro-swimmers that are driven solely by light. The fuel independence allows the swimmers to stay active even at high densities, where they form turbulent flow structures (previously seen in living fluids), and cooperate to perform a greater task.
  • colloquia
    Date:
    25 April
    2022
    Monday
    Hours:
    11:00
    -
    12:15

    Dr. Amnon Bar-Shir

    Department of Department of Molecular Chemistry and Materials Science, WIS
    Title: Magnetic Resonance “Colors”: Design and Implementation in Materials and Life Sciences
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Luminescent materials with their rich color palettes have revolutionized both science and technology through the ability to distinguish between spectrally resolved colors for a wide range of applications from sensing to molecular steganography through high-end electronics and biomedical imaging. Yet, light-based colors suffer from limitations, such as strong scattering and absorbance in opaque media, restricted spectral resolution, photo-bleaching, intolerance for color-palette extendibility and more. Amongst the diverse capabilities and many advantages of Nuclear Magnetic Resonance (spectroscopy and imaging) several are unique, e.g., the sensitivity of the chemical shifts to the chemical environment, the penetrateability of MR signals across opaque objects and the ability to produce three dimensional images of studied subjects. Here, I discuss our recent developments of molecular probes that are capable to generate artificial MR-based colors. To this end, we use synthetic chemistry, nanofabrication, and protein engineering approaches to generate novel molecular formulations (small molecules, nanocrystals (NCs), supramolecular assemblies and proteins) as MRI sensors with unique, advantageous properties (sensitivity, specificity, orthogonality, etc.). I will also discuss how the very same molecular probes can be used to better understand fundamental scientific questions in supramolecular chemistry (e.g., kinetic features of dynamically exchanging molecular systems) and materials science (e.g., understanding and controlling NCs’ formation pathways).
  • seminar
    Date:
    14 April
    2022
    Thursday
    Hours:
    13:30
    -
    14:30

    Probing single protein substrates within the chaperones ClpB and GroEL-ES

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Sander Tans
    Dept. of Bionanoscience Delft University of Technology The Netherlands
  • seminar
    Date:
    12 April
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Disaggregation of amyloid fibres by the human HSP70 chaperone machinery

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Anne Wentink
    Institute of Chemistry Leiden University Netherlands
  • seminar
    Date:
    12 April
    2022
    Tuesday
    Hours:
    11:00
    -
    13:00

    Ph.D thesis: “Structure and properties of naturally occurring materials from first principles.”

    Location: Perlman Chemical Sciences Building
    participants: Margarita Shepelenko
    under the supevision of Prof. Leeor Kronik
  • seminar
    Date:
    5 April
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    The Impact of DNA damages on Protein-DNA Interactions

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Ariel Afek
    Dept. of Chemical and Structural Biology Weizmann Institute
  • conference
    Date:
    29 March
    -
    31 March
    2022
    Tuesday
    -
    Thursday
    Hours:
    08:00

    The links between Plant Hydraulics and Ecosystem Hydrology

  • colloquia
    Date:
    28 March
    2022
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Doron Shabat

    School of Chemistry, Tel-Aviv University
    Title: Chemistry Colloquium
    Location: Gerhard M.J. Schmidt Lecture Hall
  • seminar
    Date:
    27 March
    2022
    Sunday
    Hours:
    11:00

    Decadal Climate Predictions Using Sequential Learning Algorithms

    participants: Golan Bel
    Ben-Gurion University of the Negev

    Abstract

    Decadal Climate Predictions Using Sequential Learning Algorithms Ensembles of climate models are commonly used to improve climate predictions and assess the uncertainties associated with them. Weighting the models according to their performances holds the promise of further improving their predictions. Using an ensemble of climate model simulations from the CMIP5 decadal experiments, we quantified the total uncertainty associated with these predictions and the relative importance of model and internal uncertainties. Sequential learning algorithms (SLAs) were used to reduce the forecast errors and reduce the model uncertainties. The reliability of the SLA predictions was also tested, and the advantages and limitations of the different performance measures are discussed. The spatial distribution of the SLAs performance showed that they are skillful and better than the other forecasting methods over large continuous regions. This finding suggests that, despite the fact that each of the ensemble models is not skillful, the models were able to capture some physical processes that resulted in deviations from the climatology and that the SLAs enabled the extraction of this additional information. If time permits I will also present a method for estimating the uncertainties associated with ensemble predictions and demonstrate the resulting improved reliability. References: 1. Improvement of climate predictions and reduction of their uncertainties using learning algorithms, Atmospheric Chemistry and Physics 15, 8631-8641 (2015). 2. Decadal climate predictions using sequential learning algorithms, Journal of Climate 29, 3787-3809 (2016). 3. The contribution of internal and model variabilities to the uncertainty in CMIP5 decadal climate predictions, Climate Dynamics 49, 3221 (2017). 4. Quantifying the uncertainties in an ensemble of decadal climate predictions. Journal of Geophysical Research: Atmospheres 122, 13,191–13,200 (2017). 5. Learning algorithms allow for improved reliability and accuracy of global mean surface temperature projections. Nature Communications 11, 451 (2020).
  • seminar
    Date:
    20 March
    2022
    Sunday
    Hours:
    11:00

    Four disruptive technologies that are revolutionizing sensing of the oceans

    Location: Sussman Family Building for Environmental Sciences
    participants: Emmanuel Boss

    Abstract

    The maker movement (cheap electronics + sharing), automated microscopy, autonomous platforms and small footprint satellites have been revolutionizing oceanography, opening a variety of new avenues for research and requiring a different education model. In this talk I will summarize a few activities my lab has been involved in that are associated with these disruptive technologies and why I am very optimistic for the future of our field in the coming years.
  • conference
    Date:
    15 March
    2022
    Tuesday
    Hours:
    11:30
    -
    15:30

    Faculty Day

    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Program Faculty Day 2022

  • colloquia
    Date:
    14 March
    2022
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Yuval Garini

    Faculty of Biomedical Engineering, Technion
    Title: The multi-scale structure of chromatin in the nucleus
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    The DNA in a human cell which is ~2 meters long is packed in a ~10 μm radius nucleus. It is immersed in a condensed soup of proteins, RNA and enzymes and it is highly dynamic, while it must stay organized to prevent chromosome entanglement and for ensuring proper genome expression. Studying this nanometer – micrometer scale structure requires to use both high spatial and temporal resolutions and we combine comprehensive live-cell and molecular methods. I will discuss the latest findings on the chromatin organization, the role of lamin A that we found to be of major importance and the functionality of the structure, both for physical properties, and for its functionality on gene expression.
  • seminar
    Date:
    14 March
    2022
    Monday
    Hours:
    10:00
    -
    11:00

    Ph.D thesis defense: Zoom: "Polymer beads as interfacial obstacles in fibre-reinforced composites"

    participants: Carol Rodricks
    under the supervision of Prof. Daniel Wagner

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/93495966390?pwd=T3hDNXY1WFh6bFpIbDh3OEFxZlcwZz09 The fibre-matrix interface plays a vital role in the overall mechanical behaviour of a fibre-reinforced composite, but the classical approach to improving the interface through chemical sizing is limited by material properties. Achieving a simultaneous improvement in strength and toughness in a composite is a particular challenge since these properties are mutually exclusive, and the chemical modification of the interface often results in one property being improved at the expense of the other. In contrast, the geometrical modification of the fibre-matrix interface to allow for mechanisms such as mechanical interlocking of components is a promising approach to resolving this challenge. This study explores a novel type of topographical obstacle – polymer droplets at the fibre-matrix interface. Discrete epoxy droplets are deposited onto glass fibres and embedded in an epoxy matrix to form model composites. The effect of the interfacial epoxy droplets is investigated using single fibre experiments.
  • seminar
    Date:
    8 March
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Chromatin Transactions, One Molecule at a Time

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Ariel Kaplan
    Faculty of Biology Technion
  • seminar
    Date:
    8 March
    2022
    Tuesday
    Hours:
    11:00

    Stratosphere-troposphere coupling: from wave-mean flow feedbacks to sub-seasonal predictability

    participants: Thomas Birner

    Abstract

    It is by now well established that certain stratospheric flow configurations may alter tropospheric dynamical variability. Such flow configurations include the aftermath of sudden stratospheric warming events (SSWs) or strong polar vortex events (SPVs). Although the detailed mechanisms behind this stratosphere-troposphere coupling remain elusive, most aspects of it are well-known. For example, the coupling involves feedbacks between upward propagating planetary waves of tropospheric origin and the mean flow, the tropospheric response involves synoptic-scale eddy feedbacks, SSWs tend to project onto negative anomalies of the Arctic and North-Atlantic Oscillation (AO, NAO), whereas SPVs tend to project onto positive anomalies of the AO and NAO. Here I will highlight some recent results on 1) the potential role of a planetary wave source near the tropopause in troposphere-stratosphere coupling, 2) the stratospheric influence on the evolution of baroclinically unstable waves during their non-linear decay phase, 3) the improved quantification of the stratospheric modulation of AO extremes from extended-range ensemble forecasts.
  • seminar
    Date:
    8 March
    2022
    Tuesday
    Hours:
    10:00
    -
    11:00

    M.Sc thesis defense: "Data-Driven Force Fields for Large Scale Molecular Dynamics Simulations of Halide Perovskites"

    Location: Perlman Chemical Sciences Building
    participants: Oz Yosef Mendelsohn

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/99290579488?pwd=cUIyV05SMUQ0VDErNUtma1RTL3BIQT09 In the last decade, halide perovskites (HaPs) have developed as promising new materials for a wide range of optoelectronic applications, notably solar energy conversion. Although their technology has advanced rapidly towards high solar energy conversion efficiency and advantageous optoelectronic properties, many of their properties are still largely unknown from a basic scientific standpoint. Due to the highly dynamical nature of HaPs, one of the main avenues for basic science research is the use of molecular dynamics (MD) simulations, which provide a full atomistic picture of those materials. One of the main limiting factors for such analysis is the time scale of the MD simulation. Because of the complexity of the HaP system, classical force field approaches do not yield satisfactory results and the most widely used force calculation approach is based on first-principles, namely on density functional theory (DFT). In recent years, a new type of force calculation approach has emerged, which is machine learned force fields (MLFF). These methods are based on machine learning (ML) algorithms. Their wide spread use is enabled by the ever-increasing computational power and by the availability of large-scale shared repositories of scientific data. Here, we have applied one MLFF algorithm, known as domain machine learning (GDML). After training a MLFF based on the GDML model, we observed that the MLFF fails in a dynamical setting while still showing low testing error. This has been found to be due to lack of full coverage of the simulation phase space. To address this issue, we have suggested the hybrid temperature ensemble (HTE) approach, where we create rare events that are training samples on the edge of the phase space. We achieve this by combing MD trajectories from a range of temperatures to a single dataset. The MLFF model, trained on the HTE dataset, showed increasing accuracy during the training process, while being dynamically stable for a long duration of MD simulation. The trained MLFF model also exhibited high accuracy for long-term simulations, showing remaining errors of the same magnitude of inherent errors in DFT calculation.
  • colloquia
    Date:
    7 March
    2022
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Daniel Harries

    Institute of Chemistry, Hebrew University of Jerusalem
    Title: How to stabilize dry proteins and other macromolecules
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    Considerable efforts are devoted by living creatures to stabilization and preservation of dry proteins and other macromolecules. These efforts are echoed by attempts directed toward development of new, greener, and more effective preservation technologies, including attempts to extend food shelf life and to ehnace organ storage. I will describe our work to unravel the solvation and stabilization molecular mechanisms in two examples: imbedding proteins in a glassy matrix of sugar, and macromolecular solvation in deep eutectic solvents that are (almost) non-aqueous yet biologically compatible.
  • seminar
    Date:
    1 March
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Reversible amyloids, condensates, autoinhibition and membrane interactions of human ALIX

    participants: Dr. Lalit Deshmukh
    Dept. of Chemistry and Biochemistry University of California San Diego, USA
  • seminar
    Date:
    27 February
    2022
    Sunday
    Hours:
    11:00

    Sediment geochemistry in large lakes, and what it can tell us about the ancient oceans

    participants: Sergei Katsev
    University of Minnesota, Duluth

    Abstract

    The Great Lakes of the Earth are freshwater seas, and many of the geochemical processes that take place in their bottom sediments parallel those that happen in marine environments. The conditions, however, are different enough to significantly modify the geochemical cycles of key elements. By analyzing those differences, we can not only understand the functioning of the planet's largest freshwater ecosystems, but can also gain insight into the elemental cycling (C, N, P, S...) in the oceans during the past geological epochs.
  • seminar
    Date:
    27 February
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    "Electrified Addition and Subtraction of H2 to Simplify Synthesis"

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Samer Gnaim
    Beckman Center for Chemical Sciences The Scripps Research Institute

    Abstract

    Methodologies that rely on the addition and removal of molecular hydrogen from organic compounds are one of the most oft-employed transformations in modern organic chemistry, representing a highly relevant tactic in synthesis. Despite their overall simplicity, organic chemists are still pursuing sustainable and scalable processes for such transformations. In this regard, electrochemical techniques have long been heralded for their innate sustainability as efficient methods to perform redox reactions. In our first report, we discovered a new oxidative electrochemical process for the a,b-desaturation of carbonyl functionalities. The described desaturation method introduces a direct pathway to desaturated ketones, esters, lactams and aldehydes simply from the corresponding enol silanes/phosphates, and electricity as the primary reagent. This electrochemically driven desaturation exhibits high functional group tolerance, is easily scalable (1–100 g), and can be predictably implemented into synthetic pathways using experimentally or computationally derived NMR shifts. Our second report demonstrated the reductive electrochemical cobalt-hydride generation for synthetic organic applications inspired by the well-established cobalt-catalyzed hydrogen evolution chemistry. We have developed a silane- and peroxide-free electrochemical cobalthydride generation for formal hydrogen atom transfer reactions reliant on the combination of a simple proton source and electricity as the hydride surrogate. Thus, a versatile range of tunable reactivities involving alkenes and alkynes can be realized with unmatched efficiency and chemoselectivity, such as isomerization, selective E/Z alkyne reduction, hydroarylation, hydropyridination, strained ring expansion, and hydro-Giese.
  • seminar
    Date:
    22 February
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Bringing Nucleic Acid Structures to Life through Structural Dynamics

    participants: Prof. Hashim Al-Hashimi
    Department of Biochemistry Duke University School of Medicine Durham, NC, USA
  • colloquia
    Date:
    21 February
    2022
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Efrat Lifshitz

    Schulich Faculty of Chemistry, Technion
    Title: Magnetic-optical coupling in 2D semiconductors
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    The dual coupling between intrinsic magnetism and electronic properties garners enormous attention nowadays, due to their influence on quantum technologies. The talk will elaborate on the mentioned topic in van der Waals transition metal tri-chalcogenides and two-dimensional (2D) perovskites, possessing one or more of the following magnetic properties: A long-range magnetic order (ferromagnetism, anti-ferromagnetism), an interfacial/structure driven Rashba spin-orbit, Overhauser magnetic polaron effects. The lamellar metal phosphor tri-chalcogenides (MPX3; M=metal, X=chalcogenide) possess a honeycomb arrangement of metal ions within a single layer, producing a ferromagnetic or anti-ferromagnetic arrangement, with a consequence influence on magneto-optical properties. The talk will display magneto-optical measurements, exposing routes for the long-range magnetism and the existence of valley degree of freedom in a few MPX3 (M= Mn, Fe). The results suggest that magnetism protects the spin helicity of each valley however, the coupling to anti-ferromagnetism lifts the valleys' energy degeneracy. 2D perovskite structures (e.g., (PEA)2PbI4) are composed of alternating organic-inorganic constituents. The talk will describe the most recent work, exposing the co-existence of a Rashba and the Overhauser effects, in a structure with an inversion of symmetry. The unexpected effect is explained theoretically by the breakage of symmetry through the exchange between structural configurations.
  • seminar
    Date:
    20 February
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    Reduced Rainfall in Future Heavy Precipitation Events Related to Contracted Rain Area Despite Increased Rain Rate

    Location: Sussman Family Building for Environmental Sciences
    participants: Moshe (Koko) Armon
    The Hebrew University
  • seminar
    Date:
    15 February
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Visualizing supercoiled DNA structure and interactions with base-pair resolution

    participants: Dr. Alice L.B. Pyne
    Dept. of Materials Science and Engineering University of Sheffield, UK
  • seminar
    Date:
    13 February
    2022
    Sunday
    Hours:
    16:00
    -
    17:00

    Ph.D thesis defense:" Advancing the optimally-tuned range-separated hybrid approach"

    participants: Georgia Prokopiou
    Ph.D student under the supervision of Prof. Leeor Kronik

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/95952232097?pwd=OW9SL2JlNkNYQVJ1cW5FT05HcEh2QT09 The optimally-tuned range separated hybrid (OT-RSH) functional is a non-empirical method within density functional theory, which is known to yield accurate fundamental gaps for a variety of systems. Here we extend its applicability to magnetic resonance parameters, enhance its accuracy by designing OT-RSH based double-hybrid functionals, and increase its precision for solid-state calculations by designing and generating RSH pseudopotentials.
  • seminar
    Date:
    13 February
    2022
    Sunday
    Hours:
    11:00

    Distributed views across media: From space to ocean-depths

    participants: Yoav Schechner
    Technion

    Abstract

    By economy of scale, imaging sensors can now be deployed densely and operated in a coordinated manner at large numbers in space, air, underwater and on the ground. Such distributed imaging systems enable multi-view setups across heterogeneous media of importance to geoscience. These create new observation modes. One outcome is 4D volumetric spatiotemporal recovery of scatterers in the atmosphere, specifically cloud content (the core of the CloudCT space mission). This is in addition to computed tomography of underwater sediment suspension and atmospheric turbulence distributions. We describe several such systems - demonstrated in the field, including both distributed imaging and the basis of the algorithms to analyze the data.
  • seminar
    Date:
    8 February
    2022
    Tuesday
    Hours:
    11:00

    Amplified warming of extreme temperatures over tropical land

    participants: Michael P. Byrne
    Lecturer in Earth & Environmental Sciences – University of St Andrews Marie Skłodowska-Curie Research Fellow – University of Oxford

    Abstract

    Extreme temperatures have warmed substantially over recent decades and are expected to continue warming in response to future climate change. Warming of extreme temperatures is projected to be amplified over land, with severe implications for human health, wildfire risk and food production. Using simulations from coupled climate models, I show that hot days over tropical land warm substantially more than the average day. For example, warming of the hottest 5% of land days is a factor of 1.2 larger than the time-mean warming averaged across models. The climate-change response of extreme temperatures over tropical land is interpreted using a theory based on convective coupling and the weak temperature gradient approximation. According to the theory, warming is amplified for hot land days because those days are dry: this is termed the “drier get hotter” mechanism. Changes in near-surface relative humidity further increase tropical land warming, with decreases in land relative humidity particularly important. The theory advances physical understanding of the tropical climate and highlights climatological land-surface dryness as a key factor determining how extreme temperatures respond to climate change.
  • colloquia
    Date:
    7 February
    2022
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Uri Banin

    Institute of Chemistry, Hebrew University of Jerusalem
    Title: Chemistry Colloquium (hybrid)
    Location: Gerhard M.J. Schmidt Lecture Hall
  • seminar
    Date:
    7 February
    2022
    Monday
    Hours:
    11:00
    -
    12:00

    Zoom: "Templating Silk Self-assembly with Metal Nanoparticles"

    participants: Daniel Hervitz
    M.Sc student under the supervision of Dr. Ulyana Shimanovich

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/97777492731?pwd=YXZDR0lqYUtMbHVidUlIWkl2TGxjdz09 Protein-metal interactions play an important regulatory role in the modulation of protein folding and in enabling the “correct” biological function. In material science, protein self-assembly and metal-protein interaction have been utilized for the generation of multifunctional supramolecular structures beneficial for bio-oriented applications, including biosensing, drug delivery, antibacterial activity, and many more. Even though, the nature and the mechanisms of metal-protein interaction have been extensively studied and utilized for the functionalization of protein-based materials, mainly with metal-based nanoparticles, our understanding of how metals shape protein folds, the inter-and intramolecular interactions, the associative behavior, and evolve material characteristics of protein constructs, is limited. To address these highly challenging scientific questions, I have explored the self-assembling behavior of silk fibroin protein and its’ interaction with metal nanoparticles for the formation of multifunctional composites. The central goal of my research was to explore the full potential of metal nanoparticles (NP), in particular, copper oxide (CuO) to modify the self-assembly pathway of fiber-forming protein- silk fibroin. CuO NP has been chosen as a candidate for this study, due to its versatile properties and bio-relevant functionalities applicable for sensing, antibacterial function, and capability to regulate cellular activity. Thus, to address this challenge I first focused on the understanding of metal NP-induced structural transformations in natively folded protein and on probing whether these structural changes can be artificially imposed on the assembled, β-sheet rich protein complexes. My experimental results showed that CuO NPs are indeed capable of template the assembly of natively folded silk fibroin, on the one hand, and on the other hand, exhibited variations in NPs-silk fiber interaction when added at the post-synthetic stage. Yet, the fundamental questions of how RSF-CuO NPs self-assembly occurs remain to be addressed. The exploration of biomaterial applications for silks is only a relatively recent advance; therefore, the future for this family of structural proteins appears promising.
  • seminar
    Date:
    6 February
    2022
    Sunday
    Hours:
    12:00
    -
    13:00

    Zoom: "A Faster Path to Solar Fuels: New Approaches for Highly Efficient Materials for Photoelectrochemical Energy Conversion

    participants: Dr. Ronen Gottesman
    Institute for Solar Fuels, Helmholtz Center for Materials and Energy, Berlin

    Abstract

    Zoom: https://weizmann.zoom.us/j/95703489711?pwd=Tyt5cU1tV2YrMFhYUytBU001bm4yQT09 Viable, global-scale photoelectrochemical energy conversion of cheap, abundant resources such as water into chemical fuels (“solar fuels”) depends on the progress of semiconducting light-absorbers with good carrier transport properties, suitable band edge positions, and stability in direct-semiconductor/electrolyte junctions. Investigations concentrated mainly on metal-oxides that offer good chemical stability yet suffer from poor charge transport than non-oxide semiconductors (e.g., Si, GaAs). Fortunately, only a fraction of the possible ternary and quaternary combinations (together ~ 105 – 106 combinations) were studied, making it likely that the best materials are still awaiting discovery. Unfortunately, designing controlled synthesis routes of single-phase oxides with low defects concentration will become more difficult as the number of elements increases; and 2) there are currently no robust and proven strategies for identifying promising multi-elemental systems. These challenges demand initial focusing on synthesis parameters of novel non-equilibrium synthesis approaches rather than chemical composition parameters by high-throughput combinatorial investigations of synthesis-parameter spaces. This would open new avenues for stabilizing metastable materials, discovering new chemical spaces, and obtaining light-absorbers with enhanced properties to study their physical working mechanisms in photoelectrochemical energy conversion. I will introduce an approach to exploring non-equilibrium synthesis-parameter spaces by forming gradients in synthesis-parameters without modifying composition-parameters, utilizing two non-equilibrium synthesis components: pulsed laser deposition and rapid radiative-heating. Their combination enables reproducible, high-throughput combinatorial synthesis, resulting in high-resolution observation and analysis. Even minor changes in synthesis can impact significantly material properties, physical working mechanisms, and performances, as demonstrated by studies of the relationship between synthesis conditions, crystal structures of α-SnWO4, and properties over a range of thicknesses of CuBi2O4, both emerging light-absorbers for photoelectrochemical water-splitting that were used as model multinary oxides.
  • seminar
    Date:
    6 February
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    TEST TEST TEST

    participants: Dr. Test
    Test Univ
  • seminar
    Date:
    1 February
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Precise Patterning in the Mammalian Inner Ear

    participants: Prof. David Sprinzak
    School of Neurobiology, Biochemistry and Biophysics, Faculty of Life Sciences, TAU
  • seminar
    Date:
    1 February
    2022
    Tuesday
    Hours:
    11:00

    M. Magaritz Memorial Lecture: The storyline approach to the construction of useable climate information at the local scale.

    participants: Ted Shepherd
    Department of Meteorology University of Reading
  • seminar
    Date:
    30 January
    2022
    Sunday
    Hours:
    13:00
    -
    14:00

    Zoom: M.Sc thesis defense: "Investigation of the ceramic – polymer interface in composite solid electrolyte by Nuclear Magnetic Resonance Spectroscopy"

    participants: Chen Oppenheim
    M.Sc student of Dr. Michal Leskes

    Abstract

    https://weizmann.zoom.us/j/97328767376?pwd=MkZoQ0hmbVVRank0bzkxbGpqSUdYUT09 passcode: 891716 Lithium-ion batteries with liquid electrolytes are commonly employed for powering portable electronic devices. To expand the range of applications where Li ions batteries can be used (e.g., electric transportation), solid electrolytes are considered as a safer alternative to the liquid electrolytes and they may enable use of lithium metal anodes. In this study we focused on composite solid electrolytes which are based on solid polymer (Polyethylene Oxide) and ceramic particles (Li1.5Al0.5Ge1.5P3O12, LAGP). Previous studies revealed that the highest ionic conduction path in the composites is through the interface polymer - ceramic interface. However, the chemical nature of the interface and the reason for its higher conductivity remains unclear. We aim to gain molecular - atomic level insight into the nature of the polymer - ceramic interface from solid state NMR spectroscopy. Here, I will present the development of a solid - state NMR approach that can potentially be used to selectively probe the interface. To gain sensitivity and selectivity Dynamic Nuclear Polarization (DNP), a process in which high polarization from unpaired electrons is transferred to surrounding nuclear spins will be employed. Several metal ion dopants were tested for their DNP performance in LAGP powder, and Mn2+ ions were further examined in their efficacy in the composite electrolyte. The approach was tested for selectively enhancing the NMR signal of the PEO - LAGP interface. Electrochemical characterization and in - depth solid state NMR studies provided insight into the performance of the composite and degradation processes in the composite.
  • seminar
    Date:
    26 January
    2022
    Wednesday
    Hours:
    11:30
    -
    12:30

    M.Sc thesis defense: Characterization of anisotropic strain in anelstic materials by Raman spectroscopy

    participants: Daniel Freidson
    Prof. Igor Lubomirsky's group

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/96430042316?pwd=cjJwdFUrSEE5VnU4eVNuY08wZ1F3QT09 Raman spectroscopy is used as a primary non-destructive tool for characterization of strain in thin films. It is based on the concept of the mode Grüneisen parameter, which is the ratio between the relative change in the energy of a given vibrational mode and the relative change in the unit cell volume. It has been recently reported (Kraynis et al.) that under biaxial strain, doped CeO2-films exhibit values of the mode Grüneisen parameter, which are up to 40% smaller than the bulk literature value. Doped CeO2-films are strongly anelastic, posing a question on the relation between Raman scattering frequency and anelastic strain. This work describes the way to separate anelastic and elastic contributions to the Grüneisen parameter of doped ceria thin films and show that this concept remains applicable, if only the elastic part of the strain must be taken into account. As a reference, I deposited a purely elastic yittria thin film by sputter deposition and calculated its Grüneisen parameter in a similar way. The experimental and literature values of the yittria Grüneisen parameter were found compatible, confirming that for purely elastic strain, Grüneisen parameter concept is fully applicable.
  • seminar
    Date:
    25 January
    2022
    Tuesday
    Hours:
    13:30
    -
    14:30

    M.Sc thesis defense: "Examination of Interfacial Lithium Ion Transport through Computational and Experimental Techniques"

    participants: David Columbus
    Dr. Michal Leskes's group
  • seminar
    Date:
    23 January
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    Stormy weather: past and future hazards from a weather system perspective

    participants: Jennifer Catto
    University of Exeter

    Abstract

    Natural hazards such as extreme wind, rainfall and ocean waves can have severe impacts on built and natural environments, contributing to the occurrence of disastrous events in some cases. These hazards are often caused by weather systems such as cyclones, fronts and thunderstorms. We have used a number of objective techniques to identify these weather system types, in order to understand the links between the weather systems and hazards in observations. We have then used this understanding to evaluate climate models and to better understand the response of the weather systems and the high impact hazards to a warmer climate.
  • seminar
    Date:
    18 January
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    A Single Molecule View of Signaling Complexes in Health and Disease

    participants: Prof. Eilon Sherman
    Racah Institute of Physics The Hebrew University
  • seminar
    Date:
    16 January
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    Direct Imaging of Planet Formation

    participants: Sivan Ginzburg
    California Institute of Technology

    Abstract

    The vast majority of detected planets are observed indirectly, using their small perturbation on the light emitted by the host stars. In recent years, however, the world's largest ground based telescopes have succeeded in directly imaging the light coming from some planets themselves. I will present our comprehensive theory for the mass, luminosity, and spin of gas giant planets during their final stages of formation - when they simultaneously contract and accrete gas from a disk. I will apply this theory to the luminosity and spectrum obtained by the novel direct-imaging technique, highlighting the recently discovered PDS 70 system, where two planets were directly observed during formation for the first time.
  • seminar
    Date:
    11 January
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    Matchmaking Taste Receptors and Their Ligands

    participants: Prof. Masha Niv
    The Institute of Biochemistry, Food Science and Nutrition Faculty of Agriculture, Food and Environment The Hebrew University
  • seminar
    Date:
    11 January
    2022
    Tuesday
    Hours:
    11:00

    Three arguments for increasing weather persistence in boreal summer – and why we should care.

    participants: Dim Coumou

    Abstract

    Persistent summer weather can have significant socio-economic impacts. Prolonged hot-dry conditions may lead to crop yield losses, while consecutive rainy days (e.g. associated with stalling cyclones) can cause flooding. Both observational and climate model analyses indicate that global warming weakens the hemispheric-wide circulation in boreal summer, yet it is still largely unclear what this weakening implies for the persistence of regional weather conditions. Here, I present multiple lines of evidence supporting that weather persistence in summer has been increasing over the last 40 years over most mid-latitude regions and will continue to do so under future global warming. Methodologically, we use a persistence metric rooted in dynamical systems theory, which does not require partitioning instantaneous atmospheric states in an arbitrary number of clusters. This makes it ideally suited to detect subtle changes in atmospheric motions including weather-persistence. I discuss relevant recent literature and argue that there is now substantial evidence for increasing weather persistence over mid-latitude regions, providing enhanced extreme weather risks for society.
  • seminar
    Date:
    11 January
    2022
    Tuesday
    Hours:
    11:00
    -
    12:00

    "Experimental Data-driven Paradigms for Unfolding Complexity in Chemical Systems"

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Yevgeny Rakita Shlafstein
    Columbia University: Data Science Institute with Applied Physics and Applied Mathematics Johns Hopkins University: Materials Science and Engineering

    Abstract

    With the growing complexity of functional materials and chemical systems, we often nd ourselves limited in our ability to fully represent the set of descriptors of a chemical system. In complex chemical systems, nding a complete crystallographic model that folds all the interatomic correlations using a small set of structural descriptors may not always be feasible or practical. Alternatively, one can take a data-driven approach and measure the relative changes in structural or chemical features (e.g, structural correlations, oxidation states). An experimental data-driven approach does not require complete models and enjoys the rapidly evolving machine-learning tool-set, which excel at classifying relational datasets and, if also labelled by an observed property, can provide predictive power that links system's descriptors with observed properties. I will focus on two types of complexities: (1) Hierarchical complexity, in which di erent types of structural or chemical correlations change change with the probed correlation length. For example, in ferroic materials di erent prop- erties (e.g., mechanical, dielectric, optoelectronic) may depend di erently on short- and long- range structural correlations. In multi-component alloys local chemical correlations (random- distribution, ordering, clustering) can a ect corrosion and plasticity, but altogether show a single average structural phase. Since selected materials' properties depend on correlations at a speci c hierarchical level, it is important to be able to isolate those from one another. (2) Evolutionary complexity, where the order changes over space and/or time. Nucleation, crys- tal growth, intercalation - are examples for processes that involve evolutionary complexity and can also be found in batteries, heterogeneous catalysis and photovoltaics. Isolating and track- ing order-related correlations in heterogeneous kinetically-stabilized or dynamically changing systems is, therefore, important for their more complete understanding, design and control. Total scattering and Pair Distribution Function (PDF) analysis are key methods for unfolding structural correlations at di erent correlation lengths. Using 4D-STEM to generate nm-resolution spatially-resolved electron-PDF data taken from hot-rolled Ni-laminated bulk-metallic-glass [1], I demonstrate how both hierarchical and evolutionary complexity can be uncovered and studied. Par- tially assisted with a machine-learning classi cation toolbox, we show how di erent aspects of the structural and chemical order, such as chemical-short-range-order, can be directly visualized as a function of position. In a di erent example [2] I show how an evolutionary complex systems can be manipulated to achieve a desired chemical state. In this example we demonstrate an active reaction control of Cu redox state from real-time feedback from in-situ synchrotron measurements. While complexity can lead to a lack of control over a chemical system, it is essentially adding tuning-knobs that, once isolated, understood and controlled, can unlock new materials with desired functionalities. [1] Y. Rakita, et al., Mapping Structural Heterogeneity at the Nanoscale with Scanning Nano-structure Electron Mi- croscopy (SNEM), arXiv:2110.03589 (2021). [2] Y. Rakita, et al., Active reaction control of Cu redox state based on real-time feedback from in situ synchrotron measurements, JACS 142, 18758 (2020). DOI: 10.1021/jacs.0c09418. 1
  • seminar
    Date:
    4 January
    2022
    Tuesday
    Hours:
    14:00
    -
    15:00

    The σ₂ receptor: From a pharmacological curiosity to structure-based drug discovery

    participants: Dr. Assaf Alon
    Harvard Medical School
  • seminar
    Date:
    2 January
    2022
    Sunday
    Hours:
    11:00
    -
    12:00

    "Nanostructured functional materials as electrocatalysts for sustainable resources"

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Hannah-Noa Barad
    Max Planck Institute for Intelligent Systems, Stuttgart

    Abstract

    baradhn@is.mpg.de In the quest for improving sustainability of earth’s resources, discovery of new catalysts is a press-ing issue. There are several reasons for that, among which are: First, presently the most efficient and stable catalysts for the chemical processes that we use to transform raw resources into products with the desired functions (materials or energy type), contain expensive and non-abundant elements such as Pt, Ir, and Ru. This explains the efforts to find abundant, accessible, low-cost, stable alternatives that will yield functionality comparable to exist-ing catalysts. For example, for water splitting, many new materials with different compositions have shown promising results as catalysts. However, they are mostly prepared by wet chemical synthesis, which results in chemical waste and can be too slow for industrial use. Second, the morphology of the materials is important, because it affects their catalytic properties as higher surface areas yield more catalytic active sites, surface energetics change, leading to improved reaction rates, and other differences that affect catalytic activity. These reasons emphasize the motivation to accelerate the process of finding new materials with varying nanostructures and optimized functionality, by sys-tematic exploration of several parameter spaces. Glancing angle deposition (GLAD) is a physical vapor deposition (PVD) shadow growth technique where the substrate is positioned at an oblique angle to the vapor source and can be manipulated with regard to substrate tilt angle and rotation, during the deposition. The thin films obtained by GLAD have unique nano-structures, which depend on ballistic shadowing of the substrate, and are formed as nano-structured films, leading to 3D nano-fabrication. I will present the first original results I obtained of using GLAD to form different types of material compositions and nanostructures as functional catalysts for sustainable resources. Nano-scale mor-phology and material composition are varied simultaneously using an adapted shadow growth GLAD system,[1] which eliminates the commonly used wet chemical steps for nanostructure synthe-sis. In a well-controlled one-step growth, I quickly and directly attain a large number of different nano-columnar structures, including nanorods, nano-barcodes, and nano-zigzags, with varying ma-terial compositions, on a single large-area substrate. GLAD also serves to form nanoporous ultra-thin mesh structures, in a novel dry synthesis method.[2] Both nanostructure types were studied for their electrocatalytic performance in the O2 evolution as well as CH3OH oxidation reactions and show high activity and stability. The insights I gained, show a dependence of catalytic activity on composition and nanostructuring, which the standard experimental techniques cannot achieve or explore, thus illustrating the importance and impact that GLAD has, and will have, on developing sustainable catalysts. [1] H.-N. Barad, M. Alarcón-Correa, G. Salinas, E. Oren, F. Peter, A. Kuhn, P. Fischer, Mater. To-day 2021, In Press, DOI 10.1016/j.mattod.2021.06.001. [2] H. Kwon, H.-N. Barad, A. R. S. Olaya, M. Alarcon-Correa, K. Hahn, G. Richter, G. Wittstock, P. Fischer, ArXiv211105608 Phys. 2021.
  • seminar
    Date:
    27 December
    2021
    Monday
    Hours:
    10:00
    -
    11:00

    Ph.D thesis: (Zoom)- "Electro(chemo)mechanical properties of non-stoichiometric oxides

    participants: Evgenyi Makagon

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/91582672181?pwd=WFR1NVhKZGtra2w1WG9CcGFLSGU0Zz09 Non-stoichiometric oxides are a group of materials that are extremely popular in the energy storage and conversion industry. Their functionality relies heavily on point defects and their various properties show significant dependency on point defect type and concentration. This work deals with three such properties: mechanical, electromechanical and electro-chemo-mechanical while looking into two case study materials: 1. Acceptor-doped proton conducting BaZrO3, a promising electrolyte for protonic ceramic fuel cells as it combines high bulk proton conductivity with good chemical stability. The protonic conductivity is achieved by dissociative water incorporation into oxygen vacancies formed by acceptor dopants on Zr4+ sites. Doping was found to cause linear decrease in elastic modulus with increasing dopant concentration while the size of the dopant was proved to be a key factor. Water incorporation into the vacancies decreases the moduli even further. An unexpectedly large strain electrostriction coefficient of ≈ 5·10-16 m2/V2 was observed which makes BaZrO3 the first non-classical electrostrictor with a perovskite structure. The electromechanical response was observed to follow elastic moduli trend with respect to dopant size, giving a clear indication that electrostrictive response is related to point defect induced lattice distortions. 2. Acceptor doped oxygen conducting CeO2. The first known all solid-state electro-chemo-mechanical actuators operating at room temperature were demonstrated. These devices are based on nanocrystalline (Ti-oxide/Ce0.8Gd0.2O1.9) and (V-oxide/Ce0.8Gd0.2O1.9) composite layers. Under applied bias these composites undergo an electrochemical reaction generating change in specific volume and, thereby, mechanical work. The nanocrystalline composites are the key part of these devices and they are specifically designed to provide the fastest oxygen ion diffusion coefficient observed in a solid at room temperature. This achievement paves a way to a new field of studies: all solid-state chemotronics. The findings presented in this work link together three properties of non-stoichiometric ion conducting oxides: elastic deformation, electromechanical response and solid-state electrochemistry.
  • seminar
    Date:
    26 December
    2021
    Sunday
    Hours:
    11:00

    The impact of friction on the stability of ice sheets

    participants: Roiy Sayag

    Abstract

    Ice sheets can dramatically impact the state of climate. This is due to their capacity to modify the planetary energy balance through variations in the ice cover and mass. A major question is how rapidly could such modification occur and to what extent ? This question can be addressed by investigating phenomena that involve relatively large mass flux of ice into the ocean, such as ice calving and rifting, ice streams, and melting. Many of these processes involve interactions between the ice sheet and the underlying bedrock or ocean. We model ice sheets as buoyancy-driven flows of nonlinear (non Newtonian) fluid and explore the resulted flow dynamics and stability due to different friction conditions along the base of the ice. I will show results from scaled laboratory experiments and theoretical modelling of several flows under different friction conditions that evolve patterns reminiscent to those that emerge in glacier ice flows. Specifically, the basal friction that we consider ranges from no-slip conditions, in which radially symmetric flows are stable, to free-slip conditions, in which such flows are unstable, developing patterns reminiscent to ice rifts and ice bergs. Under mixed conditions of friction, an initially radially symmetric flow can be either stable, or develop patterns reminiscent to ice streams. Our insights may have implications to predicting ice flow on Earth and possibly on other planetary objects.
  • seminar
    Date:
    22 December
    2021
    Wednesday
    Hours:
    15:00
    -
    16:00

    M.Sc thesis: "Computational approach to excited state dynamics at the interfaces of layered transition-metal dichalcogenide heterostructures"

    Location: The David Lopatie Hall of Graduate Studies
    participants: Amir Kleiner

    Abstract

    Single layers of transition metal dichalcogenides are semiconducting 2D materials which present unique electronic, excitonic and spin properties. Heterostructures composed of these materials show highly intriguing excited-state phenomena, along with a large degree of atomistic and structural tunability stemming from the underlying quantum selection rules dominating these phenomena. A predictive understanding of the effect of structural complexity on the nature of excited-state properties and interaction dynamics is crucial in order to design efficient devices for various applications, within the fields of photovoltaics, photocatalytics, optoelectronics, spintronics, and material-based quantum computing. In this research, we propose a study of the electronic and excitonic properties in heterostructures based on layered transition metal dichalcogenides and the role of structural complexities in their time-resolved relaxation mechanisms. For this, we will analyze decay processes induced by excitonic interactions with lattice vibrations, as well as other excitons and charged particles in the crystals. We will utilize predictive, Green’s-function based ab-initio methods implemented through advanced software and apply highly advanced computations using high-performance computing clusters worldwide. We will develop computational models based on these predictive approaches and on our findings to study the underlying mechanisms dominating the involved excitation processes and the light-matter interactions leading to them. Our research will be constantly driven and validated by collaborations with relevant experimental research.
  • seminar
    Date:
    21 December
    2021
    Tuesday
    Hours:
    14:00
    -
    15:00

    Ubiquitin-proteasome System Contribution to Hypoxia-induced Mitochondria Quality Control

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Michael Glickman
    Faculty of Biology, Technion
  • colloquia
    Date:
    20 December
    2021
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Leah Edelstein-Keshet

    Department of Mathematics, University of British Columbia, Canada
    Title: From cell circuits to collective cell behaviour
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    In order for our body to heal and repair injury, cell sheets must move together to seal a gap. To overcome infection, white blood cells need to track down and destroy pathogens. Such processes can only work if cells can "sense" their environment and "decide" to move in the right direction, or else, to coordinate with neighbouring cells. This requires tight control of adhesion between cells, as well as the speed and direction of cell migration. In this talk, I will describe mathematical and computational research on cell migration, both in normal and abnormal (cancer) cells. I will focus mainly on recent "multi-scale" modeling, where we combine our understanding of the "molecular machinery" inside cells, with information about how cells interact with one another. We use this approach to investigate the behaviour of groups of cells. Combining mathematics and computational methods, we can get some insights on cell organization in development and in wound healing, as well as what could go wrong in disease such as cancer.
  • seminar
    Date:
    19 December
    2021
    Sunday
    Hours:
    11:00

    Lessons from the past: Climate variability in the Levantine corridor during the Pliocene-Pleistocene transition

    participants: Nicolas Waldman

    Abstract

    The study of past warm climates with high atmospheric CO2 concentrations provides important tools for understanding present trends and developing mitigation strategies for future scenarios. The Pliocene is the last long lasting warm interval characterized by similar global climate circulation patterns and continental settings as today. Reconstructing Pliocene climate change from well-dated geological archives provides valuable insights into the climate forcing and pathways that modulated the transfer of heat and humidity and disentangle regional impacts without anthropogenic influence. To address this challenge, the current presentation shows initial results from a comprehensive study that amalgamates high-resolution multi-proxy analyses from both marine and lacustrine records from the Levant region aiming to provide an important reference for future climate and environment change scenarios under high atmospheric CO2 concentrations.
  • seminar
    Date:
    14 December
    2021
    Tuesday
    Hours:
    15:00
    -
    16:00

    Zoom: Embarking on a Thermal Journey in Low Dimensions with a 21st Century Thermometer: Graphene Nonlocal Noise

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Jonah Waissman
    Dept. Physics and Applied Physics, Harvard University

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/95894806650?pwd=c21JSFRhcUZaalROaUlBWnh4T25yZz09 Low-dimensional materials, such as 2D monolayers, 1D nanowires, and 0D quantum dots and molecules, are rich with new phenomena. The reduced dimensionality, strong interactions, and topological effects lead to new emergent degrees of freedom of fundamental interest and promise for future applications, such as energy-efficient computation and quantum information. Thermal transport, which is sensitive to all energy-carrying degrees of freedom and their interactions, provides a discriminating probe to study these materials and identify their emergent excitations. However, thermal measurement in low dimensions is dominated by the lattice, requiring an approach to isolate the electronic contribution. In this talk, I will discuss how the measurement of nonlocal voltage fluctuations in a multiterminal device can reveal the electronic heat transported across a low-dimensional bridge. We use 2D graphene as an electronic noise thermometer, demonstrating quantitative electronic thermal conductance measurement over a wide temperature range in an array of dimensionalities: 2D graphene, 1D nanotubes, 0D localized electron chains, and 3D, microscale bulk materials. I will discuss ongoing work revealing electron hydrodynamics, interaction-mediated plasmon hopping, spin waves in a magnetic insulator, and a crossover from phonon to spin transport in a bulk spin liquid candidate material.
  • seminar
    Date:
    14 December
    2021
    Tuesday
    Hours:
    14:00
    -
    15:00

    From Molecules to Organs: Bayesian Metamodeling Across Representations and Scales

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Barak Raveh
    School of Computer Science and Engineering The Hebrew University of Jerusalem
  • conference
    Date:
    9 December
    2021
    Thursday
    Hours:
    08:00

    MicroEco2 Microbial Ecology Symposium for Young Researchers

    Location: The David Lopatie Conference Centre
  • seminar
    Date:
    7 December
    2021
    Tuesday
    Hours:
    14:00
    -
    15:00

    Protein Solubility and Aggregation: Mechanisms and Design

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Elizabeth Meiering
    Department of Chemistry University of Waterloo, Canada
  • seminar
    Date:
    7 December
    2021
    Tuesday
    Hours:
    11:00
    -
    12:00

    Dispersion vs. Steric Hindrance: Reinvestigating Classic Steric Factors

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Ephrath Solel
    Institute of Organic Chemistry, Justus Liebig University

    Abstract

    London dispersion (LD) interactions, the attractive part of the van-der-Waals interaction1,2 hold somewhat of a unique position in the chemical world. Although their role in influencing macroscopic phenomena (such as the higher boiling points of larger alkanes) is well recognized, they are usually overlooked when discussing molecular phenomena. Substituents in reactions are generally considered as a source of “steric hindrance” and not as “steric attractors”, better termed dispersion energy donors (DEDs). As such, their influence on reaction outcomes was quantified and presented by classic steric factors such as the A-value. We have shown, using computational quantum mechanical tools, that these well recognized steric factors have also an attractive LD component that balance part of the steric repulsion. By focusing on the LD component we can explain various non-intuitive trends between substituents, such as the inconsistency between the size of the halogens and their A-values.3 In addition, a systematic analysis of both the steric and dispersion interactions of the same molecules allows us to quantify the relative weights of the two effects and form a new DED scale.4 Such corrected steric and LD factors could later be applied to explore the role of LD interactions also in other reactions. Our computations show that LD interactions have a significant influence on the overall relative stabilities and energetics in cyclohexane chair conformers, and also in related concerted reactions, and must not be ignored in reaction design.    Bibliography (1) Eisenschitz, R.; London, F. Z. Phys. 1930, 60, 491–527. (2) London, F. Trans. Faraday Soc. 1937, 33, 8–26. (3) Solel, E.; Ruth, M.; Schreiner, P. R. London Dispersion Helps Refine Steric A-Values: The Halogens. J. Org. Chem. 2021, 86 (11), 7701–7713. (4) Solel, E.; Ruth, M.; Schreiner, P. R. London Dispersion Helps Refine Steric A‑Values: Dispersion Energy Donor Scales. J. Am. Chem. Soc. 2021, Accepted.
  • colloquia
    Date:
    6 December
    2021
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Tsvi Tlusty

    Department of Physics, National University in Ulsan, South Korea
    Title: Protein as amorphous evolving matter

    Abstract

    Protein is matter of dual nature. As a physical object, a protein molecule is a folded chain of amino acids with diverse biochemistry. But it is also a point along an evolutionary trajectory determined by the protein’s function within a hierarchy of interwoven interaction networks of the cell, the organism, and the population. Thus, a theory of proteins needs to unify both aspects, the biophysical and the evolutionary. In this talk, a physical approach to the protein problem will be described, focusing on how cooperative interactions among the amino acids shape the evolution of the protein. This view of protein as evolvable matter will be used to examine basic questions about its fitness landscape and gene-to-function map.
  • seminar
    Date:
    5 December
    2021
    Sunday
    Hours:
    11:00

    Transient response of the tropical rain belt to volcanic eruptions

    participants: Ori Adam
  • seminar
    Date:
    30 November
    2021
    Tuesday
    Hours:
    14:00
    -
    15:00

    Folding and Quality Control of Membrane Proteins

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Nir Fluman
    Dept. of Biomolecular Sciences Weizmann Institute of Science
  • seminar
    Date:
    29 November
    2021
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Israel Rubinstein 2nd Memorial Lecture- "From Materials Electrolyte Innovations to New Sustainable Battery Chemistries

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Jean-Marie Tarascon
    College de France, Paris; Director of the French Research Network on Electrochemical Energy Storage
  • seminar
    Date:
    21 November
    2021
    Sunday
    Hours:
    11:00

    TBA

    participants: Raluca Rufu
  • seminar
    Date:
    16 November
    2021
    Tuesday
    Hours:
    11:00

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Eyal Karzbrun
    U. California, Santa Barbara

    Abstract

    Our organs exhibit complex and precise shapes which emerge during embryonic development. While biology has focused on a genetic study of organ formation, we have a limited understanding of the mesoscale mechanical forces which shape organs. A central question is how the physical form of an organ self-organizes from the collective activity of its constituents - thousands of fluctuating microscopic biological cells. Establishing a physical framework for understanding organ shape across scales requires a tight interplay between experiment and theory. However, organ development occurs within the embryo, an extraordinarily complex and coupled system with limited experimental access. To address this challenge, we developed a minimal quantitative system to study the dynamics of organ shape formation in a dish. By combining materials science with stem-cell research tools, we recreated the formation of the human neural tube - the first milestone in brain development. Experiments and vertex-model simulations reveal that a wetting transition can explain the complex dynamics of neural tube formation. Our approach paves the way for a predictive understanding of human organ formation in health and disease.
  • seminar
    Date:
    14 November
    2021
    Sunday
    Hours:
    11:15

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Alexandra Tayar
    U. California, Santa Barbara

    Abstract

    Non-equilibrium thermodynamics is a contemporary research subject that crosses fields from stellar evolution, nonlinear turbulence to biological organisms. Active matter is a subclass of non-equilibrium materials, where symmetry is broken locally and energy is consumed at the constituent level. The scale of the energy input is elementary in revealing new rich non-equilibrium physics. Currently, there is no unifying thermodynamical framework to describe non-equilibrium systems and energy propagation across scales. Therefore, it is instrumental to develop new programmable active systems that allow for a quantitative parameter space study. Biological building blocks offer reproducibility, uniformity, monodispersity, programmability at the molecular scale, and high efficiency of energy consumption. Using these design principles, we assembled new men made DNA-based active systems that exhibit spontaneous flows of materials and self-organization at the mesoscale. We study the phase behavior of soft materials in particular liquid phase separation in a non-equilibrium environment. Unexpectedly, we found that the coexistence region of phase separation shifts due to the non-equilibrium nature of the environment in low-shear regime that cannot be explained by existing theoretical frameworks. We further study the propagation of active forces across length scales, measuring molecular arrangement and mechanical loads that power active turbulent like dynamic. The unique capabilities of the developed system provide insight into possible mechanisms by which nanometer-sized molecular machines drive macroscale chaotic flows.
  • seminar
    Date:
    14 November
    2021
    Sunday
    Hours:
    11:00

    A Simple Model For Interpreting Temperature Variability And Its Higher-Order Changes

    participants: Talia Tamarin
  • seminar
    Date:
    10 November
    2021
    Wednesday
    Hours:
    11:00
    -
    12:00

    Ph.D thesis defense: “Structural and optoelectronic properties of surface-guided halide perovskite nanowires”

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Ella Sanders
    Dept. Molecular Chemistry and Materials Science

    Abstract

    Metal halide perovskites (MHPs) have re-emerged as exceptional semiconductor materials for photovoltaics and optoelectronics, gaining tremendous attention in the fields of materials and energy harvesting over the past decade. Their unique properties, alongside their relatively cheap and easy production, make them excellent candidates as materials for the next-generation optoelectronic technologies. Besides their technological advantage, their soft ionic lattice and anharmonic potential, that are part of the underlying reasons for their unusual and outstanding performance, challenge the well-established models of classical semiconductor physics and provoke many scientific research opportunities and questions. In order to intrinsically study these outstanding behaviors, a simple system is requires, diminishing complexities that can arise when examining the popularly studied polycrystalline thin films that contain multiple defects, mainly grain boundaries. Over the past decade, our group has been developing and mastering the surface-guided growth of horizontal semiconductor NWs, which can be employed to grow arrays of epitaxial single crystal MHP NWs. These NWs offer a unique opportunity as a simple model-system for investigating the intrinsic properties of MHPs, due to their single crystal nature and quasi one-dimensional structure. These are especially suitable for the investigation of how lattice strain affects the materials’ properties, considering their inherent heteroepitaxial strain. The aim of this PhD work was to gain insight on the growth of surface-guided CsPbBr3 NWs, as a representative of the MHP family, and study the effect of epitaxial strain on their structure and properties. To achieve this goal, we first developed the crystal growth of the surface-guided CsPbBr3 NWs on sapphire, by a few different vapor-phase methods. We inspected their growth in situ using simple optical microscopy to try to learn how these unique materials grow. These were followed by integration of the NWs into nanodevices in order to examine their optoelectronic properties, with a special emphasis on the influence of strain on their performance. We finally exemplified a high-throughput study using an automated optical system that can probe many NWs in a short amount of time, to develop a charge-carrier behavior model based on a large amount of data. Studying the epitaxially strained surface-guided CsPbBr3 NWs provides important insight into the crystal growth and optoelectronic properties of MHPs
  • colloquia
    Date:
    8 November
    2021
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. David Tannor

    Department of Chemical and Biological Physics, WIS
    Title: Two Hundred Years after Hamilton: Exploring New Formulations of Classical and Quantum Mechanics

    Abstract

    This talk has three parts. The first part is an introduction to Hamilton’s two monumental papers from 1834-1835, which introduced the Hamilton-Jacobi equation, Hamilton’s equations of motion and the principle of least action. These three formulations of classical mechanics became the three forerunners of quantum mechanics; but ironically none of them is what Hamilton was looking for -- he was looking for a “magical” function, the principal function S(q_1,q_2,t) from which the entire trajectory history can be obtained just by differentiation (no integration). In the second part of the talk I argue that Hamilton’s principal function is almost certainly more magical than even Hamilton realized. Astonishingly, all of the above formulations of classical mechanics can be derived just from assuming that S(q_1,q_2,t) is additive, with no input of physics. The third part of the talk will present a new formulation of quantum mechanics in which the Hamilton-Jacobi equation is extended to complex-valued trajectories, allowing the treatment of classically allowed processes, classically forbidden process and arbitrary time-dependent external fields within a single, coherent framework. The approach is illustrated for barrier tunneling, wavepacket revivals, nonadiabatic dynamics, optical excitation using shaped laser pulses and high harmonic generation with strong field attosecond pulses.
  • seminar
    Date:
    7 November
    2021
    Sunday
    Hours:
    11:00

    On the tropospheric response to transient stratospheric momentum torques

    participants: Idan White
  • seminar
    Date:
    2 November
    2021
    Tuesday
    Hours:
    14:00
    -
    15:00

    Why Chirality Is Essential for Life

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Ron Naaman
    Department of Chemical and Biological Physics Weizmann Institute
  • seminar
    Date:
    31 October
    2021
    Sunday
    Hours:
    11:00

    Promenades through Nobels' landscapes: From disorder & fluctuations to organization in Earth’s climate and other complex systems

    participants: Michael David Chekroun
    Department of Earth and Planetary Sciences Weizmann Institute of Science
  • colloquia
    Date:
    25 October
    2021
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Yossi Paltiel

    Applied Physics Department and the Center for Nano science and Nanotechnology, Hebrew University
    Title: Photosynthetic energy transfer at the quantum/classical border
  • seminar
    Date:
    24 October
    2021
    Sunday
    Hours:
    15:00

    Chemical and Biological Physics PhD Seminar

    participants: Alon Luski
    PhD with Prof Ed Narevicius
  • seminar
    Date:
    17 October
    2021
    Sunday
    Hours:
    11:00

    TBA

    participants: Yossi Ashkenazy
    Department of Solar Energy & Environmental Physics The Jacob Blaustein Institutes for Desert Research Ben-Gurion University of the Negev
  • seminar
    Date:
    13 October
    2021
    Wednesday
    Hours:
    14:00
    -
    15:30

    Chemical and Biological Physics Guest Seminar

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof Yossi Paltiel
    Applied Physics Department and the Center for Nano science and Nanotechnology, Hebrew University, Jerusalem

    Abstract

    Using the chiral induced spin selectivity (CISS) effect we were able to induce local spin impurities on magnetic and superconducting material. Dynamic control of spin impurities was also achieved. The CISS is an electronic phenomenon in which electron transmission through chiral molecules depends on the direction of the electron spin. Thus charge displacement and transmission in chiral molecules generates a spin-polarized electron distribution. This effect; is metastable and may generate local magnetic defect that can be enhanced or removed by electric dipole. Also selective process may organize the molecules adsorption. In my talk I will show that when chiral molecules are adsorbed on the surface of thin ferromagnetic film, they induce magnetization perpendicular to the surface, without the application of current or external magnetic field. On s wave superconductors that are not magnetic, chiral molecules generate states that are similar to magnetic impurities, as well as change the order parameter of the superconductor. This metastable breaking of time reversal symmetry enables to: 1. achieve magnetic mapping with nanoscale resolution. 2. develop magnetic materials controlled at the nanoscale. 3. develop chiral gated controlled devices.
  • colloquia
    Date:
    11 October
    2021
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Nicholas A. Kotov

    University of Michigan
    Title: Emergence of Complexity in Chiral Nanostructures
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    The structural complexity of composite biomaterials and biomineralized particles arises from the hierarchical ordering of inorganic building blocks over multiple scales. While empirical observations of complex nanoassemblies are abundant, physicochemical mechanisms leading to their geometrical complexity are still puzzling, especially for non-uniformly sized components. These mechanisms are discussed in this talk taking an example of hierarchically organized particles with twisted spikes and other morphologies from polydisperse Au-Cys nanoplatelets [1]. The complexity of these supraparticles is higher than biological counterparts or other complex particles as enumerated by graph theory (GT). Complexity Index (CI) and other GT parameters are applied to a variety of different nanoscale materials to assess their structural organization. As the result of this analysis, we determined that intricate organization Au-Cys supraparticles emerges from competing chirality-dependent assembly restrictions that render assembly pathways primarily dependent on nanoparticle symmetry rather than size. These findings open a pathway to a large family of colloids with complex architectures and unusual chiroptical and chemical properties. The GT-based design principles for complex chiral nanoassemblies are extended to engineer drug discovery platforms for Alzheimer syndrome [3], materials for chiral photonics, vaccines, and antivirals. Developed GT methods were applied to the design of complex biomimetic composites for energy and robotics applications [2,4] will be shown as a nucleus for discussions. References [1] W. Jiang, Z.-B. et al, Emergence of Complexity in Hierarchically Organized Chiral Particles, Science, 2020, 368, 6491, 642-648. [2] Wang, M.; Vecchio, D.; et al Biomorphic Structural Batteries for Robotics. Sci. Robot. 2020, 5 (45), eaba1912. https://doi.org/10.1126/scirobotics.aba1912. [3] Jun Lu, et al, Enhanced optical asymmetry in supramolecular chiroplasmonic assemblies with long-range order, Science, 2021, 371, 6536, 1368 [4] D. Vecchio et al, Structural Analysis of Nanoscale Network Materials Using Graph Theory, ACS Nano 2021, 15, 8, 12847–12859.
  • seminar
    Date:
    4 October
    2021
    Monday
    Hours:
    18:00
    -
    19:00

    Protein Folding and Dynamics webinar

    participants: Peter Wright
    The Scripps Research Institute
  • seminar
    Date:
    27 July
    2021
    Tuesday
    Hours:
    14:00
    -
    15:30

    "IDP-membrane interactions in neurodegeneration and neuronal function”

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. David Eliezer
    Weill Cornell Medicine Graduate School of Medical Sciences, NY, USA
  • seminar
    Date:
    25 July
    2021
    Sunday
    Hours:
    10:00
    -
    11:00

    A few lessons that nanoparticles can teach us about non-equilibrium properties of crystallization

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Assaf Ben Moshe
    Dept Molecular Chemistry and Materials Science, WIS

    Abstract

    The fact that many crystals are not in equilibrium is quite obvious and not very surprising. Yet, this often complicates our attempts to understand some of their most fundamental properties, such as for instance, their overall morphology. To further add to this complexity, non-equilibrium properties are nowadays studied in crystals made out of building blocks that consume energy and actively propel (i.e., active matter). Despite some complications that exist when trying to make analogies between the behavior of bulk crystals and their nanoscale analogs, the latter offer many advantages when studying kinetic aspects of crystal formation, in both “conventional” as well as “active” crystals. In my talk I will present two different cases where nanocrystals are used in order to shed light on some of these aspects. The first story dates all the way back to the 19th century and the seminal work by Louis Pasteur on crystals that exhibit chiral macroscopic shapes when made out of chiral building blocks. Using a model system of tellurium nanocrystals, I was able to show that the reason for chiral shape formation in crystals composed of chiral building blocks might not always be as trivial as expected. In the second part of the talk, I will present the first steps I took on an ongoing journey to understand the diffusion of extremely small (sub 10 nm) chemically propelled nanocrystals. This is meant to pave the way to ultimately use them as building blocks for non-equilibrium active crystalline matter.
  • colloquia
    Date:
    19 July
    2021
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Andrew M. Rappe

    University of Pennsylvania
    Title: Developing first-principles methods to study force- and stress-enabled mechanochemistry
    Location: Gerhard M.J. Schmidt Lecture Hall

    Abstract

    A wide variety of chemical transformations can be induced by the application of force or stress to reactive systems. In some cases, these reactions are undesired, including some tribochemical (friction-induced) reactions and bond-breaking in polymers under stress. A large and growing set of examples shows that mechanochemistry can be harnessed for useful chemical transformations, making the case for mechanochemistry as a general-purpose tool to advance chemical innovation. In order to realize this vision, we require greater understanding of how force and stress can be focused on particular bonds and reaction coordinates, and how this enhances chemical reactivity and selectivity. In this talk, I will outline strategies for applying stress to quantum-mechanical models of reactive chemical systems and for understanding the resulting mechanochemical reaction pathways. I will also describe the development of interatomic potential models that can enable larger-scale models of mechanochemical and piezoelectric effects in molecules, 2D materials, and polar solids.
  • seminar
    Date:
    6 July
    2021
    Tuesday
    Hours:
    11:00
    -
    12:00

    Intermolecular Interactions: Surfaces, Molecules and Molecular Solids

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Dr. A. Daniel Boese
    University of Graz, Graz, Austria
  • seminar
    Date:
    6 July
    2021
    Tuesday
    Hours:
    10:00
    -
    11:00

    Halite deposition in the Dead Sea: Direct observations and lessons for thick halite sequences in the geological record

    participants: Ido Sirota
    Institute of Earth Sciences The Hebrew University of Jerusalem

    Abstract

    Layered halite sequences were deposited in deep hypersaline basins throughout the geological record. These sequences are of research interest for hydrocarbon extraction, mineral exploration, tectonics and structural geology and paleoclimate research. Modern analogs and the processes leading to deposition of thick halite sequences were studied only through analyses of the common modern, shallow environments, which are fundamentally different in their nature from halite-depositing, deep waterbodies. Thus, the spatiotemporal evolution of halite sequences remained ambiguous. I will present, first, a study of the active precipitation of halite layers from the only modern analog in the world for deep, halite-precipitating basin; the hypersaline Dead Sea. Then the implications of these results to the geological record will be emphasized. Novel in situ observations in the Dead Sea link seasonal hydroclimatic conditions, thermohaline stratification, halite saturation, and the characteristics of the actively forming halite layers. The main findings of this study are: (a) Halite deposition dynamics is directly related to the development of the thermohaline stratification and it is primarily temperature controlled; it is counter-intuitive to the common approach that focus on the role of the hydrological budget in the study of hypersaline environments. (b) A pronounced depth dependency of the degree of halite saturation and halite deposition. (c) A well-defined seasonality of halite deposition on the deep lakefloor. (d) Preferential halite accumulation at the deep, hypolimnetic lake floor (>25m depth) due to intensive halite dissolution at the shallow epilimnetic lakefloor, and its re-deposition at depth, in a process termed “halite focusing”. (e) Halite accumulates at high rates in the deep lakefloor, doubling (or even more) the expected thickness without halite focusing. (f) Freshwater inflows further amplify halite thickness at the drier parts of the lake. These findings provide insights and quantify the processes required for reconstructing past hypersaline environments from halite sequences, in the Dead Sea and worldwide.
  • seminar
    Date:
    29 June
    2021
    Tuesday
    Hours:
    10:00
    -
    11:00

    Inferring Mars' Surface Winds by Analyzing the Global Distribution of Barchan Dunes using a Convolutional Neural Network

    participants: Lior Rubanenko
    Department of Geological Sciences Stanford University

    Abstract

    Sand seas on Mars are riddled with eolian landforms created by accumulating sand particles. When the sand supply is limited and the wind is approximately unidirectional, these landforms take the shape of crescentic barchan dunes, whose slip-faces are approximately perpendicular to the dominant wind direction, and their horns are oriented downwind. The morphology of barchan dunes is thus routinely used to infer wind conditions on Mars by manually analyzing aerial or satellite imagery. Despite the effectiveness of this technique on a local scale, employing it on a global scale remained challenging thusfar - as manually outlining individual dunes globally is impractical, and automatic detection methods have been largely ineffective at accurately segmenting dunes in images. Here we use Mask R-CNN, an instance segmentation convolutional neural network, to detect and outline dunes globally on Mars in images obtained by the Mars Reconnaissance Orbiter Context Camera (MRO CTX). We measure the morphometrics of dunes from their detected outlines, and infer the direction of the winds that formed them. By comparing the global wind distribution we derived to a global climate model, we study Mars' past and recent climate, and constrain global sand mobility thresholds which offer insight into the erosion and dust lifting capabilities of the atmosphere of the Red Planet.
  • seminar
    Date:
    27 June
    2021
    Sunday
    Hours:
    14:00
    -
    15:00

    Phosphine Carboxylate - a Water Sensitive Compound Prepared in Aqueous Solution”

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Dr. Roy Emanuel Shreiber
    Dept. Molecular Chemistry and Materials Science, WIS

    Abstract

    Phosphine carboxylate, H2PCO2-, was prepared and isolated for the first time. This heavier analogue of carbamate was found to be a carbon dioxide adduct on the edge of stability. The mechanism of phosphine carboxylate formation was found to proceed by a chain reaction that alternates between the acidified HPCO and the newly found cyclic hemi-acidified H(PCO)2-. This mechanism sheds light on the electrophilic reactivity of PCO- and similar molecules as well as their acid-base reactivity. Acidification of phosphine carboxylate forms phosphine carboxylic acid, an analogue of carbamic and carbonic acids that has surprising kinetic stability. Nucleophilic reactivity of phosphine carboxylate forms stabilized organic-soluble esters that may be used as building blocks in organic synthesis
  • seminar
    Date:
    20 June
    2021
    Sunday
    Hours:
    11:00
    -
    12:00

    Hybrid Talk: “POLYSACCHARIDE HYDROGELS CROSS-LINKED VIA PEPTIDE-DENDRIMERS”

    Location: Gerhard M.J. Schmidt Lecture Hall
    participants: Prof. Ronit Bitton
    Dept. Chemical Engineering, BGU
  • seminar
    Date:
    25 May
    2021
    Tuesday
    Hours:
    10:00

    TBA

    participants: Elan Levy
  • seminar
    Date:
    20 May
    2021
    Thursday
    Hours:
    14:00
    -
    15:00

    M.Sc thesis defense: “Preparation of multifunctional protein- polysaccharide fibrillar thin films with tunable mechanical and electrical properties”

    participants: Asaf Rosenberg
    Dept Molecular Chemistry and Materials Science, under the supevision of

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/96221353497?pwd=OWppT1ExY1Ewcm8zSGt4MzcvNWNiUT09 The central aim of the research is to understand how the molecular and nanoscale interactions between two natural biopolymers, fiber-forming protein-silk and conductive polysaccharide-pectin, shaping the physical properties of macro-scale composite material.
  • seminar
    Date:
    18 May
    2021
    Tuesday
    Hours:
    15:00
    -
    16:00

    Stir and mix: studying upper ocean dynamics from theory to application

    participants: Abigail Bodner
    Environmental and Society Brown University

    Abstract

    Near the ocean surface, mixing and turbulence modulate the transfer of heat, momentum, carbon and other properties, between the atmosphere and ocean interior. Accurate representation of these processes in General Circulation Models (GCMs) is crucial for simulating atmosphere-ocean interactions. However, all of these processes, generally known as boundary layer turbulence and submesoscale mixing, are on scales smaller than the grid used in GCMs, even at the highest possible resolution. Current submesoscale parameterizations represent the bulk of mixing developed across submesoscale fronts– the sharp interface between waters of different densities– but it has been shown to be too simplistic and unfitting in many circumstances. The presence of turbulence has been missing from these dynamics, and in this talk I will discuss the long-lasting problem of how to correctly include them. 
Building toward a more complete understanding of these processes, a theoretical approach of perturbation analysis is used to include the effects of turbulence as a correction to classic frontogenesis (frontal sharpening) theory. This approach is next extended into a more realistic environment, using a suite of high resolution, turbulence resolving, numerical simulations. It is found that a variety of turbulent processes resulting from winds, waves, convection, and instabilities affect the formation of fronts. Furthermore, this analysis exposes severe limitations in existing techniques to predict potential vorticity dynamics in highly turbulent regimes. Lastly, I will discuss modifying the submesoscale parameterization in GCMs to represent the complex interactions with boundary layer turbulence.
  • seminar
    Date:
    6 May
    2021
    Thursday
    Hours:
    09:15
    -
    10:15

    Zoom Lecture: “NMR of RNA: dynamics or in-cells”

    participants: Prof. Katja Petzold
    Dept. of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm

    Abstract

    Zoom Lecture: https://weizmann.zoom.us/j/98819686427?pwd=algvMEJUNHdvaFppNS9xVzlTUkhYQT09 Passcode: 551107 Many functions of RNA depend on rearrangements in secondary structure that are triggered by external factors, such as protein or small molecule binding. These transitions can feature on one hand localized structural changes in base-pairs or can be presented by a change in chemical identity of e.g. a nucleo-base tautomer. We use and develop R1ρ-relaxation-dispersion NMR methods for characterizing transient structures of RNA that exist in low abundance (populations <10%) and that are sampled on timescales spanning three orders of magnitude (µs to s). The characterization of three different types of transient structures is going to be presented. 1) The HIV-1 dimerization initiation site (DIS) undergoes large secondary structure rearrangements that provide the basis for a molecular zipper, which can be crucial for genome packaging (Nature 2012). 2) The GU wobble base-pair undergoes a change from standard wobble GU geometry to appear like a Watson-Crick base-pair stabilized by Keto-Enol tautomerization (Nature 2015). 3) a microRNA – mRNA complex changes conformation to activate the RISC complex (Nature 2020). I will furthermore give an outlook on recent efforts to measure in-cell NMR of nucleic acids in functional complexes and ribosome dynamics. www.petzoldlab.com
  • seminar
    Date:
    4 May
    2021
    Tuesday
    Hours:
    10:00

    What causes the leakiness of the North Atlantic Deep Western Boundary Current?

    participants: Aviv Solodoch
    Department of Atmospheric and Oceanic Sciences UCLA

    Abstract

    The Atlantic Meridional Overturning Circulation (AMOC) is a circulation pattern of great climatic importance. Its northward heat flux at the upper water column moderates European winter climate, and its descending branch captures atmospheric CO2 into the deep ocean, hence buffering the anthropogenically induced rise in global temperature. The Deep Western Boundary Current (DWBC) has classically been considered to be the main AMOC conduit southward at depth. However, tracer data have shown in recent decades that the DWBC "leaks" most of its material to the ocean interior in a small region of the North Atlantic, and that this leaked material continues southward in different, complex routes. These pathways and their causes are still little-explored and not well understood. In this talk I will present analysis of the DWBC leakiness properties and dynamics, based on existing datasets of passively drifting floats, a new high resolution regional numerical model, and theoretical analysis. Several alternative mechanisms of leakiness are considered, and a novel finding is that a leading cause for the leakiness is inertial separation of the current from the seafloor, near underwater capes. The role of eddies and their interaction with the separation process is investigated as well. Implications for the robustness of the deep AMOC pathways are discussed.
  • colloquia
    Date:
    3 May
    2021
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Oren Tal

    Department of Chemical & Biological Physics, WIS
    Title: Magnetic control over chemical bonds in atomic-wires and molecular junctions

    Abstract

    Controlling the properties of chemical bonds by an external stimulus is a central goal in chemistry. At the level of individual bonds, such control was achieved using light, current, electrochemical potential and electric field. In my talk, I will show that the size and direction of applied magnetic fields can affect bond stability, interatomic distance, and bond-formation probability. This behavior is demonstrated in a variety of atomic wires and single-molecule junctions. The revealed magneto-structural phenomena show that the influence of magnetic interactions on chemical bonds can be dramatic in nanoscale systems.
  • seminar
    Date:
    27 April
    2021
    Tuesday
    Hours:
    10:00
    -
    11:00

    Deposition of Gypsum Deltas at the Holocene Dead Sea by outsalting and paleoclimatic insights

    participants: Nurit Weber
    Department of Earth and Planetary Sciences Weizmann Institute of Sciences

    Abstract

    The rapid retreat of the Dead Sea during the past decades led the exposure of unique structures of massive gypsum and aragonite crusts: large capes pointing towards the open lake (termed here “gypsum deltas”) and numerous small gypsum mounds scattered on the lake’s exposed shores. Geological field relations, 14C and 34S measurements and thermodynamic calculations provide evidence that the gypsum deltas and the mounds were formed during time-intervals of low lake stands (~420±10 m below mean sea level), when sulfate-rich Ca-chloride brines discharged from the coastal aquifer via saline springs, mixed with the Dead Sea brine and precipitated the gypsum. This mixing process describes a mechanism of “gypsum outsalting”, which is completely different from the conventional view of gypsum as a product of evaporative deposition. Condition for enhanced saline springs discharge and “gypsum outsalting” occurred in the mid to late Holocene period (~ 6.6 to 0.6 ka), and were mainly intensive at the latest stages of regional aridity cycles when lake level was still low and the Dead Sea salinity was at its highest. The ages of formation of the gypsum structures coincide with times of North Atlantic cooling events and grand solar minima suggesting a direct impact of the latter on the Dead Sea hydrology and high sensitivity of the regional hydrology (controlling lake level) to global solar-related events. The frequency of appearance of the gypsum structures seems to follow the Hallstat Cycle that approached minimum at ~3000 2000 years ago.
  • seminar
    Date:
    26 April
    2021
    Monday
    Hours:
    14:00

    Physics-guided machine-learning parameterizations of subgrid processes for climate modeling

    participants: Janni Yuval
    Earth, Atmospheric and Planetary Sciences MIT school of Science

    Abstract

    Global climate models represent small-scale processes, such as clouds and convection, using subgrid models known as parameterizations. Traditional parameterizations are usually based on simplified physical models, and inaccuracies in these parameterizations are a main cause for the large uncertainty in climate projections. One alternative to traditional parameterizations is to use machine learning to learn new parameterizations which are data driven. However, machine-learning parameterizations might violate physical principles and often lead to instabilities when coupled to an atmospheric model. I will show how machine learning algorithms, such as neural networks and random forests, can be used to learn new parameterizations from the output of a three-dimensional high-resolution atmospheric model, while obeying physical constraints such as energy conservation. Implementing these parameterizations in the atmospheric model at coarse resolution leads to stable simulations that replicate the climate of the high-resolution simulation, and capture important statistics such as precipitation extremes. I will also discuss how machine-learning parameterizations can give further insights into the parameterization problem. Specifically, I will show that failures of machine-learning parameterizations can be used to better understand the relationship between large-scale fields and subgrid processes.
  • seminar
    Date:
    25 April
    2021
    Sunday
    Hours:
    11:00
    -
    12:00

    “Elastic-mediated interactions between cells”

    participants: Prof. Shelly Tzlil
    Faculty of Mechanical Engineering, Technion

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/97324532197?pwd=MGoxSGhJODNWQ2ZGT1p4elJjMG9lZz09 Cell-cell communication is essential for growth, development and function. Cells can communicate mechanically by responding to mechanical deformations generated by their neighbors in the extracellular matrix (ECM). The ECM is a non-linear viscoelastic material and therefore mechanical communication is expected to be frequency-dependent. In my talk, I will describe our work on the characteristics and implications of mechanical communication over the ECM.
  • seminar
    Date:
    20 April
    2021
    Tuesday
    Hours:
    00:00

    The hydrological paradox - why the whole is less than the sum of its parts?

    participants: Erwin Zehe
    KIT

    Abstract

    Hydrological systems are inherently non-linear and exhibit an enormous structural and functional heterogeneity. Strikingly, we can nevertheless successfully simulate stream flow generation and the water balance of river catchments with rather simple models that are largely incompatible with the frequently reported subscale process heterogeneity and non-linearity. Here we argue that subscale structural heterogeneity and randomness must not prevent the emergence of functional simplicity. On the contrary, we found simplicity to emerge at rather small scales, reflecting self-organization in hydrological functioning not despite but due to subscale small-scale heterogeneity and the dissipative nature of hydrological process. While we acknowledge that hydrological landscapes are heterogeneous, they are by no means a random product. Catchments exhibit a considerable spatial organisation, which manifests through structured patterns of topography, soil, vegetation, self-similar surface and subsurface drainage networks and most prominently through ubiquitous preferential flow phenomena. While this organized “catchment from” does strongly determine present storage, cycling and release of water, energy and chemical species, this catchment form has in turn been shaped by of water, energy, and nutrients of the past. Is this “co-evolution” just chance or manifested self-organization? This question has been inspiring many scientists to search for thermodynamic principles that link form and function in the Earth system. Here we will present evidence that a thermodynamic and information theoretic perspective opens up new avenues for (i) diagnosing and explaining self-organization in hydrological dynamics, (i) upscaling of constituting relations and (i) using thermodynamic optimality for hydrological predictions.
  • seminar
    Date:
    13 April
    2021
    Tuesday
    Hours:
    16:00
    -
    17:00

    Larger tsunamis from megathrust earthquakes where slab dip is reduced

    participants: Bar Oryan
    Lamont Doherty Earth Observatory Columbia University

    Abstract

    A subset of megathrust earthquakes produce anomalously large tsunamis for their magnitude. All of these recorded ‘tsunami earthquakes’ in the past 50 years had extensional aftershocks in the upper plate. These include the two largest and most destructive earthquakes of that period, the 2004 Sumatra–Andaman and the 2011 Tohoku events. Evidence from the region of Tohoku indicates that normal fault slip in the upper plate during the earthquake may have contributed to the tsunami size. Here we present a numerical model that shows how a reduction of the dip of a subducting slab, on a timescale of millions of years, can result in an extensional fault failure above a megathrust earthquake on timescales of seconds to months. Slab dip reduction bends the upper plate so that the shallow part fails in extension when a megathrust rupture relieves compressional stress. This results in a distribution of extensional aftershocks comparable to that seen above the Tohoku megathrust. Volcanic arc migra- tion and uplift data for Tohoku and several other tsunami earthquakes is consistent with slab dip reduction. The collection of more such data might identify other areas of tsunami hazard related to slab dip reduction.
  • seminar
    Date:
    11 April
    2021
    Sunday
    Hours:
    11:00
    -
    12:00

    “Engineering personalized tissue implants: From 3D printing to bionic organs”

    participants: Prof. Tal Dvir
    Faculty of Life Sciences, TAU

    Abstract

    Zoom LInk: https://weizmann.zoom.us/j/95962123886?pwd=ZWV6WkwxKzlNU00zRU1ER3JIWkg4Zz09 In this talk I will describe cutting-edge bio and nanotechnologies for engineering functional tissues and organs, focusing on the design of new biomaterials mimicking the natural microenvironment, or releasing biofactors to promote stem cell recruitment and tissue protection. In addition, I will discuss the development of patient-specific materials and 3D-printing of personalized vascularized tissues and organs. Finally, I will show a new direction in tissue engineering, where, micro and nanoelectronics are integrated within engineered tissues to form cyborg tissues and bionic organs.
  • seminar
    Date:
    6 April
    2021
    Tuesday
    Hours:
    00:00

    Advances of remote sensing in agriculture and forestry for climate change adaptation

    participants: Tarin Paz-Kagan
    Volcani Institute

    Abstract

    Forests and agricultural orchards are becoming increasingly susceptible to drought, ‎insect ‎‎outbreaks, and disease due to climate change worldwide. Thus, forest ‎and ‎agricultural systems management needs to be proactively targeted to improve their ‎resilience to anthropogenic and ‎climate change. The potential of remote sensing ‎data for ‎agriculture and forestry has long been recognized. The global coverage and repositories of different ‎types ‎of satellite data extending integrating with developing UAVs and ‎sensor ‎capabilities provide a unique database, which allows us to develop, test, and ‎implement ‎innovative measures to adapt agriculture and forest to the foreseen climate ‎scenarios. ‎However, there is still a considerable gap between data and information. ‎Remote sensing ‎applications integrated with innovative artificial intelligence techniques ‎could make ‎fundamental discoveries for sustainable environmental management. Thus, ‎the seminar ‎aims to present advanced remote-sensing applications for agriculture and ‎forest to climate ‎change adaptation. Four case studies will be presented, including (1) ‎mapping woody ‎species distribution and richness along the climatic gradient; (2) ‎developing canopy ‎geometry traits to characterize and monitor tree structure using LiDAR ‎applications; and (3) ‎Incorporation winter tree physiology in deciduous orchard into ‎forecast- models of bloom ‎and yield, and (4) leaf to landscape approach to study ‎forest responses to drought.
  • colloquia
    Date:
    5 April
    2021
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Panče Naumov

    Division of Science and Mathematics, New York University Abu Dhabi (NYUAD)
    Title: The 2021 Gerhard M. J. Schmidt Memorial Lecture
  • colloquia
    Date:
    22 March
    2021
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Sarel Fleishman

    Department of Biomolecular Sciences, WIS
    Title: Computational protein design: basic research and applications

    Abstract

    Until very recently, the accuracy of protein-design calculations was considered too low to enable the design of large proteins of complex fold. As a result, enzyme and binder optimization has relied on random or semi-rational mutagenesis and high-throughput screening. Our lab is developing a unique approach that combines structural bioinformatics analyses with atomistic design calculations to dramatically increase the accuracy of design calculations. Using this strategy, we have developed several general and completely automated methods for optimizing protein stability and activity. I will briefly discuss the fundamentals of this strategy and show case studies of large and complex proteins that we and our collaborators have optimized. Our lab’s long-term and still-unmet research goal is to enable the completely automated design of any biomolecular activity, and I will focus on our current research directions including the design of new enzymes and binders.
  • seminar
    Date:
    16 March
    2021
    Tuesday
    Hours:
    10:00
    -
    11:00

    Supported Nanocomposites for Water Decontamination

    participants: Ines Zucker
    Tel Aviv University

    Abstract

    Contamination of drinking water sources by a variety of organic and inorganic compounds demands more efficacious and reliable treatment technologies. However, conventional water treatment technologies remain chemically demanding, energy intensive, and ineffective in removing key trace contaminants. As such, nanotechnology-based approaches have been increasingly explored to enhance or replace traditional remediation methods because of the high reactivity and tunable-properties of nanomaterials. In her talk, Dr. Zucker will provide an overview on the current status of nano-enabled water decontamination, including promising opportunities and barriers for implementation. Specifically, the application of molybdenum disulfide (MoS2) for heavy metal removal will be extensively discussed as a case study, where material properties, removal mechanisms, and large-scale applications are optimized.
  • seminar
    Date:
    14 March
    2021
    Sunday
    Hours:
    11:00
    -
    12:00

    Nucleation fronts initiate frictional motion

    participants: Prof. Jay Fineberg

    Abstract

    Zoom LInk: https://weizmann.zoom.us/j/97917323609?pwd=OGpCVzNKWGlCSS9lbTIyS0FtN1lHUT09 Recent experiments have demonstrated that rapid rupture fronts, akin to earthquakes, mediate the transition to frictional motion. Moreover, once these dynamic rupture fronts ("laboratory earthquakes" ) are created, their singular form, dynamics and arrest are well-described by fracture mechanics. Ruptures, however, need to be created within initially rough frictional interfaces, before they are able to propagate. This is the reason that ``static friction coefficients” are not well-defined; frictional ruptures can nucleate for a wide range of applied forces. A critical open question is, therefore, how the nucleation of rupture fronts actually takes place. We experimentally demonstrate that rupture front nucleation is prefaced by slow nucleation fronts. These nucleation fronts, which are self-similar, are not described by fracture mechanics. They emerge from initially rough frictional interfaces at a well-defined stress threshold, evolve at characteristic velocity and time scales governed by stress levels, and propagate within a frictional interface to form the initial rupture from which fracture mechanics take over. These results are of fundamental importance to questions ranging from earthquake nucleation and prediction to processes governing material failure.
  • colloquia
    Date:
    8 March
    2021
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Koby Levy

    Department of Structural Biology
    Title: Proteins mobility, affinity & stability for optimized function

    Abstract

    Proteins, which are at the heart of many biological processes, are involved in a variety of self-assembly processes that are controlled by various chemical and physical interactions. Quantifying the driving forces that govern these processes and particularly the trade-offs between them is essential to obtaining a more complete understanding of protein dynamics and function. In my lecture, I will discuss the molecular determinants that govern linear diffusion of proteins along DNA or along microtubules. These and other cellular processes, such as protein folding, are subject to conflicting forces some of which are regulated by post-translational modifications. Understanding the trade-offs between the stability, affinity and mobility is not only essential to decipher transport processes in the cell but also for formulating concepts for their engineering. I will discuss the power of computational models in formulating fundamental biomolecular concepts and in predicting novel principles of cellular function or for its optimization.
  • seminar
    Date:
    4 March
    2021
    Thursday
    Hours:
    09:30
    -
    10:30

    “Beyond mapping: perturbation as the key to understanding function”

    participants: Dr. Michal Ramot
    Dept Neurobiology, WIS

    Abstract

    Zoom link: https://weizmann.zoom.us/j/94322871667?pwd=NXkvODRXWVZlbW9hSEtScHN1M0F4dz09 passcode: 870711 Neuroimaging has allowed us to map the correlations between brain activation, and external stimuli or behaviour. Yet these correlations can only hint at the function of the brain regions involved. In order to more casually investigate these relationships between brain and behaviour, we must perturb the brain, and see what changes this brings about in behaviour. I will provide a framework for doing so through covert neurofeedback. This technique allows us to perturb brain networks by reinforcing desired network states directly, through a reward orthogonal to the networks being trained. Yet a prerequisite for such a test of function and causality, is a strong hypothesis regarding the purported link between a specific network and behaviour. We must therefore also develop better behavioural tools, in order to establish such links.
  • seminar
    Date:
    2 March
    2021
    Tuesday
    Hours:
    16:00
    -
    17:00

    TBA

    participants: Kevin Uno
    Lamont-Doherty Earth Observatory Columbia University
  • seminar
    Date:
    28 February
    2021
    Sunday
    Hours:
    11:00
    -
    12:00

    Modeling formation of caveolar superstructures

    participants: Prof.Michael Koslov
    Department of Physiology and Pharmacology, TAU

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/92668474661?pwd=d01aQVZkWnhiT0NRQlFkVE5XeWRjdz09 Caveolae, the flask-shaped pits covered by caveolin-cavin coats, are abundant features of the plasma membrane of many cells. Besides appearing as single membrane indentations, caveolae are organized as superstructures in the form of rosette-like clusters. Here we propose that clustering of caveolae is driven by forces originating from the elastic energy of membrane bending deformations and membrane tension. We substantiate this mechanism by computational modeling, which recovers the unique shapes observed for the most ubiquitous caveolar clusters consisting of two, three, four and five caveolae.
  • colloquia
    Date:
    22 February
    2021
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Michal Sharon

    Department of Biomolecular Sciences
    Title: Rapid mass spectrometry investigation of overproduced proteins from crude samples

    Abstract

    Analysis of intact proteins by native mass spectrometry has emerged as a powerful tool for obtaining insight into subunit diversity, post-translational modifications, stoichiometry, structural arrangement, stability, and overall architecture. Typically, such an analysis is performed following protein purification procedures, which are time consuming, costly, and labor intensive. As this technology continues to move forward, advances in sample handling and instrumentation have enabled the investigation of intact proteins in crude samples, offering rapid analysis and improved conservation of the biological context. This emerging approach is expected to impact many scientific fields, including biotechnology, pharmaceuticals, and clinical sciences. In my talk I will discuss the information that can be retrieved by such experiments as well as the applicability of the method by presenting the characterization of engineered proteins, drug binding, antibody specificity and protein-protein interactions.
  • seminar
    Date:
    18 February
    2021
    Thursday
    Hours:
    09:30
    -
    10:30

    Room Temperature 13C-DNP in Diamond Powder

    participants: Dr. Daphna Shimon
    Institute of Chemistry, HUJI

    Abstract

    Zoom Link: Zoom: https://weizmann.zoom.us/j/91742036303?pwd=cWJuOFBEZUpYU3p6bHBjUEduRllxdz09 Passcode: 771770 Electron and nuclear spins in diamond have long coherence and relaxation times at room temperature, making them a promising platform for applications such as biomedical and molecular imaging and nanoscale magnetic field sensing. While the optically-active nitrogen-vacancy (NV) defect has received a great deal of attention, the substitutional nitrogen (or P1) center also exhibits long coherence and relaxation times. These P1 centers are typically present at significantly larger concentrations (about an order magnitude larger) than NVs, allowing us to explore the role of P1-P1 interactions in mediating DNP. The system can, in principle, show DNP via the solid effect (SE), cross effect (CE) and Overhauser effect (OE) depending on the P1 concentration and the field. Here, we show enhancement of natural abundance 13C nuclei found within the diamond, using the unpaired electron of the P1 center (concentration 110-130 ppm) in particles with a 15-25 μm diameter, under static conditions at room temperature and 3.4 T. We discuss the DNP spectrum, the active DNP mechanisms and what we can learn about the diamond powder from DNP.
  • seminar
    Date:
    16 February
    2021
    Tuesday
    Hours:
    10:00

    Styles and rates of landscape evolution away from tectonic-plate boundaries: examples from southern Africa

    participants: Shlomy Vainer
  • seminar
    Date:
    15 February
    2021
    Monday
    Hours:
    14:30
    -
    15:30

    Ph.D thesis defense: Tuning the shape memory effect in polyurethanes by amorphous and crystalline mechanisms"

    participants: Asaf Nisenbaum

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/92088510918?pwd=bW11Rk1TKzEzeFdES3NJS1VCaTE4Zz09
  • seminar
    Date:
    14 February
    2021
    Sunday
    Hours:
    11:00
    -
    12:00

    “Transcription Factors Binding and the Regulation of Gene Expression: Lessons from Single-Molecule Experiments”

    participants: Prof. Ariel Kaplan
    Faculty of Biomedical Engineering, Technion

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/94661424796?pwd=U0Z1YjdsbGUrV29STEZlMVhweUtXUT09 All our cells contain the same genetic information, encoded in the sequence of nucleotides that compose our DNA. The identity of different cells, and their response to different stimuli, is therefore controlled by processes regulating which subset of genes is “expressed” at a specific cell and a specific time. The first step in gene expression regulation is the binding of a special family of proteins, called transcription factors, to specific sequences in regulatory regions in the DNA. Packaging of the DNA into the dense structure of chromatin, and chemical modifications of the DNA, provide the cell with the possibility of dynamically modulating expression but add additional layers of complexity to the process in ways that are not fully understood. In my talk, I will report on our work using single-molecule optical tweezers assays to study how the thermodynamics and kinetics of transcription factor binding are modulated by these different layers of information. .
  • colloquia
    Date:
    8 February
    2021
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Boris Rybtchinski

    Department of Molecular Chemistry & Materials Science
    Title: Crystallization Mechanisms: Classical, Nonclassical, and Beyond

    Abstract

    Understanding how order evolves during crystallization represents a long-standing challenge. We will describe our recent studies on crystallization of organic molecules and proteins by cryo-TEM imaging and cryo-STEM tomography. They reveal mechanisms, in which order evolution proceeds via diverse pathways, including various intermediate states. Based on these findings, we suggest a general outlook on molecular crystallization.
  • seminar
    Date:
    2 February
    2021
    Tuesday
    Hours:
    10:00

    Adventures in the Critical Zone: from carbon fluxes to wildfires

    participants: Antonello Provenzale

    Abstract

    The Hadley circulation is a key element of the climate system. It is traditionally defined as the zonally averaged meridional circulation in the tropics, therefore treated as a zonally symmetric phenomenon. However, differences in temperature between land and sea cause zonal asymmetries on Earth, dramatically affecting the circulation. This longitudinal dependence of the meridional circulation evokes questions about where and when the actual large scale tropical circulation occurs. Here, we look into the connection between the longitudinally dependent meridional circulation, and the actual large scale transport of air in the tropics using a coupled Eulerian and Lagrangian approach. Decomposing the velocity field into rotational and divergent components, we identify how each component affects the actual circulation. We propose an alternative definition for the circulation, that describes the actual path of air parcels in the tropics, as a tropical atmospheric conveyor belt. We further investigate this definition, analyzing the circulation under climate change and its effect on precipitation changes. We show that in order to predict future climate, the regionality and three-dimensionality of the large-scale tropical circulation must be taken into account. We find that the changes in the circulation vary significantly over longitude, and are overlooked when analyzing the zonally averaged meridional circulation. The circulation is strengthening and expanding in the center of the Pacific, a region where the circulation barely existed in past. On the other hand, the circulation is weakening in the Indo-Pacific region, where it was the most significant in the past. These differences appear as a shift in the region of ascent of the conveyor belt, that is revealed when analyzing the decomposed vertical wind. The pattern of weakening of the ascent in the Indo-Pacific and strengthening in the center of the Pacific explains the projected changes in precipitation. The Indo-Pacific region is drying, while the precipitation in the center of the Pacific is intensifying.
  • seminar
    Date:
    31 January
    2021
    Sunday
    Hours:
    14:00
    -
    15:00

    Simulating Chemistry from Atoms to Devices: Next-Generation Reactive Molecular Dynamics

    participants: Dr. David Furman
    Dept. Chemistry, University of Cambridge

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/97142508810?pwd=S2Voc3BMYnh6RmFTYUxLbUFjQXRGZz09 Until recently, computational studies of chemical reactivity were exclusively dealt with using quantum mechanical approaches, which severely limited the system's size and accessible time scales for simulation. To bypass the need to solve Schrodinger's equation, and facilitate large-scale simulations for up to millions of atoms, both accurate and efficient models of the chemical bond have to be constructed. I will present recent advances in the field of modeling chemical reactions in large-scale, complex systems (i.e. "dirty chemistry"), with a particular focus on ReaxFF reactive molecular dynamics. Prominent applications from recent years will be highlighted, including: (a) discovery of the underlying operation principles of a novel laser-based mass-spectrometry technique, and (b) prediction of the surprising chemistry that leads to the formation of several key precursors to biomolecules of life upon the collapse of a "primordial bubble". Finally, I will present a new ReaxFF formulation that opens exciting new avenues for orders of magnitude more accurate simulations for long time scales.
  • seminar
    Date:
    31 January
    2021
    Sunday
    Hours:
    11:00
    -
    12:00

    Live imaging of chromatin distribution reveals novel principles of nuclear architecture and chromatin compartmentalization”.

    participants: Prof. Talila Volk
    Dept. Molecular Genetics, WIS

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/91657907719?pwd=M2F2WlRKWGRuUHlxN0tNWFhZVUVzZz09 The genetic material of live organisms is packed and stored within the nucleus. It contains DNA wrapped around the nucleosomes, which then organized into chromatin fibers that partition into distinct compartments, which eventually fill the entire nucleus. Chromatin three dimensional topology is essential for proper accessibility of transcription factors, which control tissue-specific gene expression programs. Whereas chromatin partition into specific domains has been described in cells in culture conditions, information regarding chromatin 3 dimensional distribution in tissues within live organisms is still missing. We have imaged the chromatin in muscle fibers of live, intact Drosophila larvae, and revealed its 3 dimensional structure. Our results demonstrate novel 3 dimensional architecture of the chromatin which is evolutionary conserved, and has important implications on the regulation of gene expression.
  • seminar
    Date:
    28 January
    2021
    Thursday
    Hours:
    09:30
    -
    10:30

    “Low-field MRI: new perspectives”

    participants: Prof. Najat Salameh

    Abstract

    Zoom: Link: https://weizmann.zoom.us/j/98957854014?pwd=ZTEyazd6cThxUE90L3ZJbkdkbkFWQT09 passcode: 159170 Magnetic Resonance Imaging (MRI) is a non-ionizing, non-invasive imaging modality that has become key in modern medicine. Its high value resides in a broad range of soft tissue contrasts or biomarkers that can be tuned to enable the identification and follow-up of many pathophysiological or metabolic processes. Such developments were made possible thanks to almost forty years of hardware and software development, yet access to MRI nowadays remains exclusive, bound to radiology suites in hospitals, and restricted to less than half of the world population. This limited accessibility is mostly due to its one-fits-all design and its prerequisites for intense magnetic field strength that impact cost, siting infrastructure, and clinical compatibility. One way to improve accessibility in MRI is to lower the magnetic field strength that will naturally influence cost, siting, and compatibility. Further, lowering the field strength can translate in smaller footprint designs which geometry and contrast could purposely be tuned to certain targeted applications. Indeed, relaxation mechanisms are known to change with the surrounding magnetic field, with larger T1 dispersion at low field that have for the most part been unexplored. Although very promising, many challenges arise linked to the lower intrinsic nuclear spin polarization inherent to low field technologies, calling for original and innovative approaches to reach clinical relevance. During this seminar, Prof. Najat Salameh will describe those challenges and possible solutions by presenting the current landscape of low field imaging and recent progress made at the Center for Adaptable MRI Technology, Basel University.
  • seminar
    Date:
    26 January
    2021
    Tuesday
    Hours:
    11:00

    Marine electrical imaging reveals novel freshwater transport mechanism in Hawaiʻi

    participants: Eric Attias
    Hawaiʻi Institute of Geophysics and Planetology University of Hawaiʻi

    Abstract

    Conventional hydrogeologic models employed to compute ocean island sustainable yields and aquifer storage neglect the nearshore and onshore submarine environment’s complexity. However, the onshore aquifer at the island of Hawaiʻi exhibits a significant volumetric discrepancy between high-elevation freshwater recharge and coastal discharge. This study presents a novel transport mechanism of freshwater moving from onshore to onshore via a multilayer formation of water-saturated layered basalts with interbedded low-permeability layers of ash/soil, as revealed by marine-controlled source electromagnetic (CSEM) imaging. We propose that this newly discovered transport mechanism of fresh water may be the governing mechanism in other volcanic islands. Additionally, our water column CSEM imaging detects multiple vertical freshwater plumes extending from the seafloor to the ocean surface. These findings provide valuable information to elucidate hydrogeologic and oceanographic rocesses affecting biogeochemical cycles in coastal waters worldwide.
  • colloquia
    Date:
    25 January
    2021
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Roy Bar-Ziv

    Department of Chemical & Biological Physics, WIS
    Title: Toward autonomous “artificial cells"

    Abstract

    We study the assembly of programmable quasi-2D DNA compartments as “artificial cells” from the individual cellular level to multicellular communication. We will describe recent progress toward autonomous synthesis and assembly of cellular machines, synchrony, pattern formation, fuzzy decision-making, memory transactions, and electric field manipulation of gene expression.
  • seminar
    Date:
    19 January
    2021
    Tuesday
    Hours:
    18:00
    -
    19:00

    New perspectives on interlayer excitons in two-dimensional heterostructures

    participants: Dr. Ouri Karni

    Abstract

    Zoom: https://weizmann.zoom.us/j/96278790117?pwd=T1ZjaHlxQjlEQkFIbE12UDJCazNwZz09 Two-dimensional layered (van-der-Waals) heterostructures, made by stacking different monolayers of semiconducting transition-metal dichalcogenides, have been drawing much attention as versatile platforms for studying fundamental solid-state phenomena and for designing opto-electronic devices. Interlayer excitons, electron-hole pairs that bind to each other across the interlayer spacing in these heterostructures, hold promise as key tools for probing the interlayer interface structure, and for exploring many-body interactions(1). With long lifetimes, spin polarization, and electric tunability, interlayer excitons are also promising as flexible information carriers(2, 3). However, they were mostly studied through the scope of their visible light emission, missing essential properties such as their momentum-space image or their absorption strength, necessary for rigorous study of their many-body interactions and potential applications. In this talk I will present our recent studies aimed at measuring such unknown interlayer exciton properties and their dependence on the heterostructure. I will show a new interlayer exciton in WSe2/MoS2 heterostructures which we discovered based on its light emission in infra-red wavelengths, rather than in the visible range(4). I will demonstrate its properties as inferred from its optical interrogation. Then, I will present the quantitative measurement of the elusive optical absorption spectrum of interlayer excitons using electric-field modulation spectroscopy, essential for coherent coupling of light to those excitons(5). Finally, I will reveal how time- and angle-resolved photoemission spectroscopy is used to image the interlayer exciton in momentum-space, yielding its size and binding energy, so far inaccessible through optics(5).
  • seminar
    Date:
    19 January
    2021
    Tuesday
    Hours:
    11:00

    In situ identification of 48-56.0 million old proteins in chert with unusually high stiffness

    participants: Filipe Natalio
    Scientific Archaeology Unit Weizmann Institute of Science
  • seminar
    Date:
    17 January
    2021
    Sunday
    Hours:
    11:00
    -
    12:00

    Quantitative Prediction of Nanoparticle Assembly for Personalized Nanomedicine

    participants: Prof. Yosi Shamay
    Dept Biomedical Engineering, Technion

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/92447973616?pwd=UWJkRWdraGFVQjdPb3ByWis1bDk2Zz09 Development of targeted nanoparticle for personalized cancer therapeutics often requires complex synthetic schemes involving both supramolecular self-assembly and multiple chemical modifications. These processes are generally difficult to predict, execute, and control. I will describe a new method to accurately and quantitatively predict self-assembly of kinase inhibitors drug molecules into nanoparticles based on their molecular structures. The drugs assemble with the aid of new kind of excipient comprised of highly conjugated sulfated molecule into particles with ultra-high drug loadings of up to 90%. Using quantitative structure-nanoparticle assembly prediction (QSNAP) calculations and machine learning, a new algorithm was developed as highly predictive indicators of both nano-self assembly and nanoparticle size with unprecedented accuracy.
  • seminar
    Date:
    14 January
    2021
    Thursday
    Hours:
    09:30
    -
    10:30

    ‘Identification of Dynamic Components in the Liquid-Liquid Phase Separation of CPEB4 by EPR Spectroscopy’

    participants: Dr. Manas Seal
    Dept Chemical and Biological Physics, WIS

    Abstract

    Link: https://weizmann.zoom.us/j/96046369379?pwd=emp0U0wwcmpNQlhsMisrNmp0bjRDdz09 Passcode: 693143 The molecular mechanisms and associated structures and dynamics of liquid-liquid phase separation (LLPS) proteins that form membrane-less organelles in cells have attracted considerable interest in recent years. EPR spectroscopy along with site directed spin labelling (SDSL) using nitroxide spin labels is a well-established technique to study dynamics of proteins. In this seminar I will discuss the dynamic properties of the spin labelled low complexity N-terminal domain of cytoplasmic polyadenylation element binding-4 protein (CPEB4NTD) in its LLPS and non-LLPS states. We found the coexistence of three CPEB4NTD populations with distinct spin label rotational correlation times before and after LLPS. We identified population I as the predominant protein species in the dilute phase, with fast motions that agree with expected dynamic properties of monomeric CPEB4NTD. We assigned population III to a compact ensemble that undergo slow motions, and population II to a looser ensemble experiencing intermediate motions. LLPS, which took place with increasing temperature is associated with increased population of II at the expense of III, while population I remains constant. At the end based on these findings, I will present a three-component equilibrium model that postulates the existence of LLPS-competent CPEB4NTD species (II and III) prior to macroscopic phase separation.
  • seminar
    Date:
    6 January
    2021
    Wednesday
    Hours:
    14:30
    -
    15:30

    M.Sc thesis defense: Band gaps of crystalline solids from a Wannier-localized, optimally tuned screened range-separated hybrid functional

    participants: Guy Ohad

    Abstract

    https://weizmann.zoom.us/j/93597285944?pwd=S0FJdHJ6eVpFTGJ3dHJHa3c1amJyUT09 Abstract: A long-standing challenge within density functional theory (DFT) is the development of functionals that accurately predict the band gap and electronic structure of crystalline solids. A promising candidate for this task is the screened range-separated hybrid (SRSH) functional, which has been shown to yield accurate results for finite systems when one of the parameters in the functional, the range-separation parameter, is selected a priori. In the bulk limit, however, this parameter cannot be selected non-empirically based on the ionization potential theorem, owing to the delocalized electronic orbitals. Recently, we have developed a new method for the non-empirical tuning of the range-separation parameter, that is based on the removal of an electron in a state that corresponds to a Wannier function. We have applied the method to a set of systems ranging from narrow band gap semiconductors to large band gap insulators, obtaining fundamental band gaps in excellent agreement with experiment.
  • seminar
    Date:
    5 January
    2021
    Tuesday
    Hours:
    11:00

    Nanoinclusions in diamonds: trapped fluids and solid molecular N2 and CO2

    participants: Oded Navon
    Institute of Earth Sciences The Hebrew University of Jerusalem

    Abstract

    Diamonds are perfect boxes for delivering samples of fluids and volatile species from the mantle to the surface. While mineral inclusions are often a few >30 micrometer in size and allow easy analysis, fluid inclusions are mostly <1 micrometer. Still, careful analysis allowed us to define carbonatitic, saline and silicic melts in the inclusions. Recently, transmission electron microscopy allowed us to look into even smaller inclusions, 10-30 nm in size where we found solid molecular nitrogen and solid molecular CO2. Contrary to the melts that are low volume mantle melts, the N2 and CO2 are interpreted as exsolutions of N and O atoms that were taken as single atoms in the diamond matrix and later migrated and joined to form tiny octahedrons full of N2 and CO2. Geologically, the solids are an oddity of nature, but the melts can play an important roll in the extraction of trace elements from the mantle and into the crust.
  • seminar
    Date:
    3 January
    2021
    Sunday
    Hours:
    11:00
    -
    12:00

    PCR-free sensing of Covid-19, metastatic mRNA biomarkers and towards single-cell proteomic

    participants: Prof. Amit Meller
    Department of Biomedical Engineering, Technion

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/98521602060?pwd=T1B1TEJqcXEwUW50QzBEaXd3RS9XZz09 SARS-CoV-2 outbreak of the coronavirus disease (COVID-19) has underlined the acute need for extremely sensitive, accurate, fast, point-of-care mRNA quantification sensors. Here I will show how solid-state nanopores can be used to digitally count target mRNA molecules from both biological and clinical Covid-19 samples surpassing the accuracy and gold-standard” RT-qPCR. Additionally, we applied our method for the sensing of cancer metastatic mRNA biomarkers MACC1 and S100A4 at early stage of the diseases, suggesting a potential use of the method in early precision medicine diagnostics. Moving beyond nucleic acids, I will discuss our on-going efforts towards the use of plasmonic nanopore devices for the single protein molecules identification based on partial labelling of only two or three amino acids. This research opens up vast directions for single-cell proteomics of even rarely expressed proteins.
  • seminar
    Date:
    31 December
    2020
    Thursday
    Hours:
    09:30
    -
    10:30

    1H LF NMR Sensor Application for Monitoring of PUFA-rich Healthy Food Autoxidation

    participants: Prof. Zeev Wiesman
    Department of Biotechnology Engineering Ben Gurion University of the Negev

    Abstract

    Abstract: The present seminar will review our work in 1H LF NMR energy relaxation time technology and its application in chemical and morphological characterization and monitoring of oxidation of polyunsaturated fatty acids (PUFA) found in many important commercial products such as edible oils, foods, and biological systems. PUFA’s aggregates are related simultaneously with material’s functionality and degradation. The multiple double bonds and allylic carbons characteristics of the PUFA’s molecular structure are responsible for its oxidation susceptibility and can result in the degrade of the product’s functionality and formation of toxic substances. Wherein individual PUFA molecules have specific structures their material functionality and stability against oxidation are strongly depended on their aggregate structures such as in oils or within aqueous emulsions and specific arrangements within these structures with other components such as antioxidants is an important material parameter. The oxidation degree of PUFA’s rich materials can be measured via different methods such as volumetric, spectroscopic and chromatographic technologies. The traditional technologies based on titrimetric techniques have many drawbacks. These methods need strict time regimes during individual stages of analyzes, control of the intensity of the agitation and control of reaction components including light and atmospheric oxygen exposure. Other disadvantage of these traditional methodologies is the requirement of a large amount of solvents, being environmental unfriendly. In order to overcome the disadvantages of the traditional technologies used to monitor oxidation we are suggesting the use 1H LF NMR relaxation. This technology does not require organic solvents, complex samples preparation and the sample is preserved after analysis. The 1H LF NMR generates 2D T1 (spin-lattice) vs. T2 (spin-spin) energy relaxation time domain that is able together with self-diffusion test to characterize chemical and morphologically complex aggregate materials such as PUFA in liquid or solid assembly or in presence of interfacial forces of water. In addition, these spectra can efficiently monitor oxidation and assess antioxidants efficacy. We demonstrate the work we have done to date on the 1H LF NMR data processing optimization and the application of this technology in the characterization and monitoring of oxidation on oils on fatty acids saturated, monounsaturated and polyunsaturated. This sensor application is of relevant contributions for diverse fields such as food industries, pharmaceuticals, cosmetics and biofuels. The seminar is divided into three parts: a) Optimization of the ILT data processing technology of 1H LF NMR energy relaxation time. This study showed the efficiency of the regularization parameters for data reconstruction, and a relative high accuracy of the primal dual convex objectives (PDCO) solutions in comparison to the graphic results of real data. b) Developing of intelligent NMR relaxation sensor applications of fatty acids (FA) with saturated chains, MUFA and PUFA-rich oils for their chemical and physical/morphological characterization and monitoring of their autoxidation. Detailed fingerprinting chemical and morphological maps were generated for saturated FAs, MUFAs, PUFAs and their oxidation polymerized final products. It was possible to propose peak assignments to the various spin-lattice (T1) and spin –spin (T2) energy relaxation time proton populations (TD) based on the molecular segmental motions of the different fatty acids chemical and structural segments (e.g., glycerol; double bonds; aliphatic chains; and tails) to generate an explicatory dictionary of T1 and T2 values with chemical and physical/morphological structures and their changes due to oxidation. c) Developing of intelligent 1H LF NMR energy relaxation time domain sensor application for PUFA-rich oil-in-water emulsions characterization and monitoring autoxidation. Emulsions based on linseeds, very rich in α-linolenic acid PUFA (18:3) and structural oleosin protein and other emulsification agents naturally producing nano-scale oxidation stable oil bodies, were formed from linseed in water. The linseed emulsions enriched with PUFA-rich fish oil were analyzed under thermal oxidation conditions, using 1H LF NMR T1-T2 energy relaxation time reconstruction for determining the oil bodies composition and structure and oxidative stability.
  • colloquia
    Date:
    28 December
    2020
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Dan Oron

    Dept. of Materials and Interfaces, WIS
    Title: From design to optical properties in colloidal semiconductor nanocrystals

    Abstract

    Colloidal semiconductor nanocrystals have turned over the past three decades from a scientific curiosity to a component in numerous commercial products, particularly in displays, lighting and light detection. On the one hand these are complex chemically synthesized entities, and on the other they behave, in many senses, as ‘giant’ artificial atoms. The interplay between these two enables us to imbue them with unique optical properties by design of their internal structure. I will go over some of our recent efforts in utilizing designer nanocrystals for various applications, including luminescence upconversion (the conversion of two low energy photons into a single high energy photon), electric field sensing and optical gain. Finally, I will discuss opportunities for the development of colloidal sources of non-classical states of light and our recent advances in quantum spectroscopy, enabling to study the optical and electronic properties of single quantum dots with unprecedented precision.
  • seminar
    Date:
    27 December
    2020
    Sunday
    Hours:
    11:00

    A coupled Eulerian-Lagrangian analysis of the large-scale tropical atmospheric circulation and its implication for climate change

    participants: Dana Reiter
    Department of Earth and Planetary Sciences Weizmann Institute of Science

    Abstract

    The Hadley circulation is a key element of the climate system. It is traditionally defined as the zonally averaged meridional circulation in the tropics, therefore treated as a zonally symmetric phenomenon. However, differences in temperature between land and sea cause zonal asymmetries on Earth, dramatically affecting the circulation. This longitudinal dependence of the meridional circulation evokes questions about where and when the actual large scale tropical circulation occurs. Here, we look into the connection between the longitudinally dependent meridional circulation, and the actual large scale transport of air in the tropics using a coupled Eulerian and Lagrangian approach. Decomposing the velocity field into rotational and divergent components, we identify how each component affects the actual circulation. We propose an alternative definition for the circulation, that describes the actual path of air parcels in the tropics, as a tropical atmospheric conveyor belt. We further investigate this definition, analyzing the circulation under climate change and its effect on precipitation changes. We show that in order to predict future climate, the regionality and three-dimensionality of the large-scale tropical circulation must be taken into account. We find that the changes in the circulation vary significantly over longitude, and are overlooked when analyzing the zonally averaged meridional circulation. The circulation is strengthening and expanding in the center of the Pacific, a region where the circulation barely existed in past. On the other hand, the circulation is weakening in the Indo-Pacific region, where it was the most significant in the past. These differences appear as a shift in the region of ascent of the conveyor belt, that is revealed when analyzing the decomposed vertical wind. The pattern of weakening of the ascent in the Indo-Pacific and strengthening in the center of the Pacific explains the projected changes in precipitation. The Indo-Pacific region is drying, while the precipitation in the center of the Pacific is intensifying.
  • seminar
    Date:
    22 December
    2020
    Tuesday
    Hours:
    11:00

    Reducing the Uncertainty of Extreme Weather and Climate Predictions

    Location: Sussman Family Building for Environmental Sciences
    participants: Assaf Hochman
    Department of Tropospheric Research, Institute of Meteorology and Climate Research Karlsruhe Institute of Technology, Eggenstein - Leopoldshafen

    Abstract

    Weather and climate extremes such as cold spells, heat waves, heavy precipitation or windstorms have long been considered challenging to adequately predict a few days in advance. Even at shorter time scales, it is sometimes difficult to estimate the magnitude and impact area accurately. Therefore, they have been selected as one of the grand challenges by the World Climate Research Program. Several studies suggest that extreme temperatures or heavy precipitation events may become more frequent and more intense with climate change, making this topic even more pertinent. The ability to predict the development of any dynamical system (a system that evolves in time), depends on: 1) its persistence, meaning that a persistent system will be easier to predict and 2) the number of options the system can develop into/from, meaning that systems with a small number of options will be easier to predict. Recent advances in dynamical systems theory allow to efficiently compute these metrics from model data. Our earlier findings show that the dynamical systems metrics can serve as an extremely informative qualitative method for evaluating the predictability and dynamics of synoptic systems over the Eastern Mediterranean. The talk will discuss this novel dynamic approach and its recent applications in extreme weather forecasting, as well as in climate model projections over the Eastern Mediterranean.
  • seminar
    Date:
    20 December
    2020
    Sunday
    Hours:
    11:00
    -
    12:00

    Zoom Lecture: The extracellular matrix in bacterial biofilms. From peptides and proteins to whole biofilms

    participants: Dr. Liraz Chai
    Institute of Chemistry, HUJI

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/98510631069?pwd=QzVFbzNxMHZETWwrM0xjbVBmV3FDdz09 Biofilms are aggregates of cells that form on surfaces and interfaces. A major characteristic of biofilms is the self-secretion of an extracellular matrix, that is composed of biopolymers, mainly proteins, polysaccharides, and nucleic acids. Using a variety of biophysical methods, we study the basic interactions between matrix components that lead to the formation of a 3D network. In this talk I will describe our recent findings, going all the way from peptides through full-length proteins to whole biofilms.
  • seminar
    Date:
    17 December
    2020
    Thursday
    Hours:
    09:30
    -
    10:30

    The hyperpolarized brain: What can we add to cerebral metabolism with hyperpolarized MR probes?

    participants: Dr. Mor Mishkovsky
    Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne (EPFL)
  • colloquia
    Date:
    14 December
    2020
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Dan Tawfik

    Department of Biomolecular Sciences, WIS
    Title: Protein evolution – from so simple a beginning

    Abstract

    The size, structural complexity, and functional perfection of proteins, raise a question for which we so far have no answer: How did the very first protein(s) evolve? Protein synthesis depends on dozens of highly sophisticated proteins thus presenting a chicken-egg dilemma. The most common explanation is that proteins emerged from short and simple polypeptides, that further expanded in length and complexity to give proteins as we know them today. Can we reconstruct such early polypeptide ancestors? Can a short polypeptide confer biochemical functions that are reminiscent of modern proteins? And can such polypeptides be evolutionary linked to their modern descents? I will discuss our most recent findings with respect to the polypeptide precursors of nucleotide binding proteins, and the emergence of the first cationic amino acid.
  • seminar
    Date:
    8 December
    2020
    Tuesday
    Hours:
    10:00

    Seismic sensing with optical fibers – principles and applications

    participants: Ariel Lellouch
    Stanford University

    Abstract

    During the last decade, seismic sensing with optical fibers has become a reality. By analyzing the effect of seismic deformation on the fiber’s optical response, state-of-the-art Distributed Acoustic Sensing (DAS) now offers a 1-meter sensor resolution for tens of kilometers of fiber. In other words, a single DAS system can record up to 40,000 data channels at once – two orders of magnitude more than the entire earthquake-monitoring seismic network in Israel. In this talk, I will first introduce the underlying operating principles of DAS acquisition. These measurements are very different from conventional seismic sensors and need to be analyzed accordingly. Subsequently, most of the talk will revolve around DAS applications in various scenarios. We utilize the ambient seismic field, recorded on a standard telecommunication fiber deployed around the Stanford campus, to analyze subsurface properties. The same fiber can also be used to measure changes in traffic patterns due to the COVID-19 lockdown. With downhole DAS arrays deployed in deep vertical wells, we can study previously undetected low-magnitude earthquakes. Finally, we utilize DAS data recorded inside an unconventional gas field to unveil reservoir properties with unprecedented resolution.
  • seminar
    Date:
    6 December
    2020
    Sunday
    Hours:
    11:00
    -
    12:00

    Zoom lecture: Nanoscale Optical Imaging Of Individual And Densely Packed Microgel Colloids

    participants: Prof. Frank Scheffold
    Department of Physics, University of Fribourg

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/95267372668?pwd=dEhvRlA3SGtvVTQ1QnVmZ3JJdTZEQT09 Thermosensitive microgels are widely studied hybrid systems combining properties of polymers and colloidal particles uniquely. This study explores the frequency-dependent linear viscoelastic properties of dense suspensions of micron-sized microgels in conjunction with an analysis of the local particle structure and morphology-based on superresolution microscopy. By identifying the dominating mechanisms that control the elastic and dissipative response, we can explain these widely studied soft particle assemblies' rheology. Interestingly, our results suggest that the polymer brush-like corona's lubrification reduces friction between the microgel contacts.
  • seminar
    Date:
    2 December
    2020
    Wednesday
    Hours:
    15:00
    -
    16:00

    The impact of non-canonical DNA structures on protein-DNA interactions

    participants: Dr. Ariel Afek
    Duke Center for Genomic and Computational Biology Duke University NC, USA
  • colloquia
    Date:
    30 November
    2020
    Monday
    Hours:
    11:00
    -
    12:00

    Prof. Sam Safran

    Department of Chemical and Biological Physics - WIS
    Title: How cells determine their volume

    Abstract

    Living cells regulate their volume using a diverse set of mechanisms, to maintain their structural and functional integrity. The most widely-used mechanism to control cell volume is active ion transport. Experiments on adhered cells surprisingly revealed that their volume is significantly reduced as their basal area is increased1. We have developed a physical theory2 which considers both electrostatics and cell activity to predict a generic relation for how adhered cells regulate their volume in response to changes in their area, in agreement with the observations. Those measurements also show that the nuclear volume scales with the cell volume. Recently, the Volk group3 using intact-organism imaging, discovered that changes in nuclear volume dramatically varies the spatial organization of chromatin (DNA and associated proteins); this may have important consequences for gene expression. A simple polymeric model4 that includes the competition of chromatin self-attraction and interactions with the nuclear membrane, predicts transitions in the chromatin organization relative to the nucleus from peripheral to central to conventional, as the nuclear volume is reduced, as measured in the experiments of the Volk group.
  • seminar
    Date:
    24 November
    2020
    Tuesday
    Hours:
    11:00

    What caused megadroughts in North and South America?

    Location: Sussman Family Building for Environmental Sciences
    participants: Nathan Steiger
    Hebrew University of Jerusalem
  • seminar
    Date:
    23 November
    2020
    Monday
    Hours:
    16:00

    Putting Proteins Together: Reconstitution of Mechanisms Driving Cilia Motility and Fertilization

    participants: Dr. Iris Grossman-Haham
    Dept. of Cellular and Molecular Pharmacology University of California, San Francisco
  • seminar
    Date:
    23 November
    2020
    Monday
    Hours:
    14:00
    -
    15:30

    Zoom: MSc thesis defense: Guided CdTe Nanowires: Synthesis, Structure, Optoelectronics and Bandgap Narrowing

    participants: Yarden Daniel
    Supervision of Prof. Ernesto Joselevich

    Abstract

    https://weizmann.zoom.us/j/99592122461?pwd=MjM4ZDN0ZDFVeGZOYkdqQi9CUy9uUT09 Semiconductor nanowires (NWs) are quasi 1D nanostructures, exhibiting distinctive physical properties suitable for efficient bottom-up design of nanodevices. A challenging limiting step of their integration into planar functional systems is the difficulty to align them on horizontal surfaces. One simple and elegant way to avoid post growth assembly of NWs is to grow them horizontally in the first place. Over the past decade, our group has established the surface guided growth of horizontal semiconductor NWs aligned by crystalline substrates with controlled crystallographic orientations, directions and position. As the NWs are comprised of different semiconductors, they are optically active is different spectral regimes including the UV and visible range. However, optical activity in the pivotal infrared (IR) regime is not yet exhibited for guided NWs and a systematic exploration of it can pave the way for effective devices for telecommunication and night vision technologies. CdTe, a narrow band-gap II-VI semiconductor (~1.5 eV), is an attractive candidate owing to its promising optical and electrical properties, making it an attractive material for solar cells and near IR (NIR) photodetectors. Its alloys with mercury, known as MCT (HgxCd1-xTe) are already central components of efficient IR photodetectors due to continuous bandgap narrowing with growing percentage of mercury. In this work, we present the vapor-liquid-solid (VLS) growth and self-alignment of surface guided CdTe NWs with a wurtzite crystal structure on flat and faceted sapphire substrate (α-Al2O3). The NWs were integrated into fast IR photodetectors showing high on/off ratio of up to ~104 and, to the best of our knowledge, the shortest response times (~100 ms) to IR irradiation with respect to other CdTe based photodetectors. Attempts to create HgxCd1-xTe through cation exchange show initial conversion (~2%) of the crystal, though with significant bandgap narrowing of ~ 55 meV. These findings pave the way for simple and elegant fabrication of CdTe NWs’ based NIR nano-photodetectors, which can be expended to a wide range of Mid-IR and Far-IR photodetectors with small size through bandgap engineering.
  • seminar
    Date:
    22 November
    2020
    Sunday
    Hours:
    11:00
    -
    12:00

    Zoom Lecture: Aggregation in intrinsically disordered proteins and associative polymers"

    participants: Prof. Yitzhak Rabin, BIU
    Bar Ilan University

    Abstract

    We model intrinsically disordered proteins (IDPs) as associative polymers (APs). We study the kinetics of gelation in solutions of amphiphilic polymers that contain strongly associating stickers connected by long soluble chain segments. We explore the relation between primary sequence and droplet morphology in APs in poor solvent. We find that gelation of APs can be suppressed by grafting them to surfaces, a possible way to control aggregation of IDPs. Zoom Link: https://weizmann.zoom.us/j/99868477151?pwd=U3hFTWhjZ05nT3Ryd1ZHOXJ6Z3Y1Zz09
  • seminar
    Date:
    17 November
    2020
    Tuesday
    Hours:
    16:15

    Insights on Processes in Polar Supercooled Cloud Lifecycles from Observations and Cloud Resolving Model Simulations

    participants: Israel Silber
    Department of Meteorology and Atmospheric Science Pennsylvania State University

    Abstract

    Supercooled clouds substantially impact polar surface energy budgets but large-scale models often underestimate their occurrence, which motivates accurately establishing metrics of basic processes. A polar stratiform cloud’s lifecycle is determined by a set of complex interactions and feedbacks between different micro-physical and macro-physical processes, some of which are not fully understood or quantified, leading to uncertainty in climate predictions. These polar clouds are commonly presupposed as being turbulent as a result of intense cloud-top longwave radiative cooling, while experiencing desiccation dominated by precipitating ice. In this talk, I examine some of these underlying assumptions and provide applicable guidance for large-scale model evaluation. I first present observations of persistent formation of drizzle drops at cloud temperatures below -25 °C detected over McMurdo Station, Antarctica. These supercooled drizzle observations supported by large-eddy simulations (LES) used to examine the cloud’s formation and evolution under initially stable, nonturbulent conditions, suggest that drizzle can be common over polar regions and serve as the main cloud moisture sink even well below the freezing temperature. A persistent nonturbulent cloud state suggested by the LES leads to the examination of nonturbulent cloud occurrence in observational datasets from Arctic and Antarctic ground-based sites. Such stable, nonturbulent conditions, surmised to preferentially occur early in cloud lifecycles, are estimated to prevail in a quarter of cloud occurrences over these polar sites. I use LES sensitivity tests to examine how short to intermediate period gravity waves, which are supported by such stable conditions, may catalyze turbulence formation when aerosol particles available for activation are sufficiently small. The observational datasets are also utilized to examine ice precipitation processes, and show that the vast majority of polar supercooled clouds are at least weakly precipitating ice at the cloud base even when they are not seeded from above, consistent with commonly observed supercooled cloud longevity. These results indicate that supercooled cloud layers are a sustained source of ice precipitation, and suggest that ground-based statistics offer valuable guidance for large-scale models. Finally, as an example of how some of these observational and modeling results may be used to evaluate the representations of polar clouds in large-scale models, I briefly describe using the GISS E3 climate model in single-column model (SCM) mode applied to the supercooled drizzle case study.
  • seminar
    Date:
    14 October
    2020
    Wednesday
    Hours:
    15:00
    -
    16:00

    Zoom Ph.D defense: “A First Principles Perspective on Stability, Dynamics, and Defect Chemistry in Halide Perovskites”

    participants: Ayala Cohen
    Dept. Materials and Interfaces, under the supervision of Prof. Leeor Kronik

    Abstract

    Zoom Link: https://weizmann.zoom.us/j/93181739182?pwd=YTd0K1drTmZSdnB0bElFZVI4K0NXdz09
  • seminar
    Date:
    10 September
    2020
    Thursday
    Hours:
    09:00

    Why are there colors in the ocean?

    participants: Derya Akkaynak
    Harbor Branch Oceanographic Institution Florida Atlantic University
  • seminar
    Date:
    23 August
    2020
    Sunday
    Hours:
    14:00
    -
    15:00

    Structure Sensitivity in Catalysis

    participants: Dr. Charlotte Vogt
    Niels Stensen Post-Doctoral Fellow at HUJI and the Weizmann Institute for Science

    Abstract

    Some fundamental concepts of catalysis are as of yet not fully explained but are of paramount importance for the development of improved supported metal catalysts for chemical industries and environmental remediation. Structure (in)sensitivity is such a fundamental physical concept in catalysis, which relates the rate of a catalytic reaction per unit surface area to the size of a nanoparticle. If this rate per unit surface area changes with catalyst particle size, a reaction is termed structure sensitive. Conversely if it does not - a reaction is termed structure insensitive. Historically, many fundamental physical concepts explaining the behavior of metal nanoparticular catalysts have been formulated by studying single crystal facets with surface science techniques which has left a considerable gap in our basic knowledge of catalysts at work. By using and developing state-of-the-art operando (micro)spectroscopic techniques, inter alia operando high-temperature high-pressure FT-IR, in-situ high-resolution STEM, and quick-X-ray absorption spectroscopy (quick-XAS) with millisecond time resolution, over the last few years I have been exploring the fundamental physical concepts behind fundamental structure-activity relationships of catalytic reactions by studying non-model catalysts at work. For example, by applying these methods to study a structure sensitive reaction (carbon dioxide hydrogenation) to a structure insensitive one (ethene hydrogenation) we show that the same geometric and electronic effects that we find to explain structure sensitivity make it unlikely for structure insensitivity to exist (while we do observe it empirically). However, interestingly, in the case of the structure insensitive ethene hydrogenation reaction, such size-dependent nanoparticle restructuring effects as the decrease of the reversibility of adsorbate-induced restructuring and the increase of carbon diffusion with increasing particle size are observed by quick-XAS (see Figure 1). While for the structure sensitive CO2 hydrogenation no such perturbation was observed. We further show that this particle size dependent restructuring induced by ethene hydrogenation can make a structure sensitive reaction structure insensitive. Hence, we may postulate that structure insensitive reactions should rather be termed apparently structure insensitive, which changes our fundamental understanding of the age-old empirical observation of structure insensitivity.
  • colloquia
    Date:
    3 August
    2020
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Meir Lahav

    Weizmann Institute of Science, Department of Materials and Interfaces
    Title: Virtual Chemistry Colloquium
  • colloquia
    Date:
    20 July
    2020
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Prof. Gershom (Jan M.L.) Martin

    Weizmann Institute of Science Department of Organic Chemistry
    Title: Chemistry Colloquium
  • colloquia
    Date:
    6 July
    2020
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Brian Berkowitz

    WIS Earth and Planetary Sciences
    Title: Chemistry Colloquium
  • colloquia
    Date:
    22 June
    2020
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Lucio Frydman

    WIS Department of Chemical and Biological Physics
    Title: Chemistry Colloquium
  • seminar
    Date:
    14 June
    2020
    Sunday
    Hours:
    11:00
    -
    12:00

    Zoom Lecture: Designing In Situ Architectures in 3D Cell-Laden Hydrogels

    participants: Prof. Dror Seliktar
    Faculty of Biomedical Engineering, Technion Institute of Technology

    Abstract

    One of the key advantages in using light-sensitive hydrogel biomaterials is the ability to spatially structure cell scaffolds with three-dimensional mechanical cues that guide cellular morphogenesis. However, this has proven difficult because of the high toxicity associated with the cross-linking interactions. To overcome this challenge, we developed a new paradigm in micro-patterning using a reversible temperature-induced phase transition from liquid to solid vis-à-vis lower critical solubility temperature (LCST). This facilitates reduced transport kinetics of the polymer chains in solution, thus enabling crosslinking that is truly compatible with cell-laden 3D culture. Cellularized constructs were patterned to reveal a difference in morphogenesis between chemically crosslinked “stiffer” and physically crosslinked “softer” regions. Emphasizing the importance of mechanical heterogeneity in cellular morphogenesis, the results validate cutting-edge technology that can provide scientists with a robust set of tools for engineering cell and tissue growth in three dimensions.
  • colloquia
    Date:
    8 June
    2020
    Monday
    Hours:
    11:00
    -
    12:15

    Prof. Nir Gov

    Department of Chemical and Biological Physics
    Title: Chemistry Colloquium
  • seminar
    Date:
    7 June
    2020
    Sunday
    Hours:
    11:00
    -
    12:00

    Maritime silver trade in the Levant during the Iron Age and its effect on human pollution

    Location: Sussman Family Building for Environmental Scien