Integrated Calendar

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.

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.

Many plant foods contain oxalate C2O4(-2) that reaches the colon when we eat plant foods.
When oxalate reaches high concentrations it can crystalize together with Ca+2 to form kidney stones. Humans don’t have enzymes to degrade oxalate, but microbes do. Therefore oxalate-degrading probiotics are a potential treatment for hyperoxaluria.
Since clinical trials with oxalate-degrading microbes, like Oxalobacter Formigenes, could not show oxalate reduction, additional microbes that can degrade oxalate are of high interest, especially those that can perform in the human gut.
In my talk I will describe how we harnessed lab evolution to develop novel gut microbes that can degrade oxalate. We obtained E. coli isolates from the stool of human volunteers and evolved them to metabolize oxalate in an anaerobic chamber.
While no E. coli is known to utilize oxalate, our isolates evolved robust growth on oxalate as a sole source of carbon and energy. In my talk I will present findings on the genetic and molecular mechanism underlying this evolution.

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.

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.

We are studying the mechanistic basis of epigenetic regulation in the Polycomb system, a vital epigenetic silencing pathway that is widely conserved from flies to plants to humans. We use the process of vernalization in plants in our experiments, which involves memory of winter cold to permit flowering only when winter has passed via quantitative epigenetic silencing of the floral repressor FLC. Utilising this system has numerous advantages, including slow dynamics and the ability to read out mitotic heritability of expression states through clonal cell files in the roots. Using mathematical modelling and experiments (including ChIP and fluorescent reporter imaging), we have shown that FLC cold-induced silencing is essentially an all-or-nothing (bistable) digital process. The quantitative nature of vernalization is generated by digital chromatin-mediated FLC silencing in a subpopulation of cells whose number increases with the duration of cold. We have further shown that Polycomb-based epigenetic memory is indeed stored locally in the chromatin (in cis) via a dual fluorescent labelling approach. I will also discuss how further predictions from the modelling, including opposing chromatin modification states and extra protein memory storage elements, are being investigated. I will also discuss the mechanisms by which long term fluctuating temperature signals are sensed before being converted into digital chromatin states for long term memory storage.