Integrated Calendar

DNA damages compromise the ability of the genome to function. Cells from all organisms have mechanisms to recognize DNA damage, initiate a signaling response, and recruit repair enzymes. Complete failure of these mechanisms leads to cell death. Incorrect or inefficient repair leads to mutations and cancer. Our work focuses on damages that distort the DNA helix, specifically the carcinogenic dimers induced by ultraviolet (UV) radiation, and the bulky DNA adducts induced by cigarette smoke and by the chemotherapy drug cisplatin. These types of damages are especially deleterious as they block RNA and DNA polymerases. We apply genomic methods to map DNA damages and their repair at high resolution in human genomes. In parallel, we study the effects of damage on gene expression and chromatin accessibility. Both chromatin structure and transcription influence the sensitivity to damage and the efficiency of repair. At the same time, damages elicit changes in chromatin accessibility and a dramatic gene expression shutdown. In my talk, I will give an overview of ongoing research projects in our lab that study the cellular responses to UV-, smoking- and cisplatin-induced damages, and are central to understanding both the carcinogenic process and the mechanisms of chemotherapy resistance.

In this talk, I will explain the challenges that arise from the task of maintaining a large database in a remote and untrusted storage. The technical part of the talk will describe a new and tight logarithmic lower bound for memory checkers, an algorithmic tool used to enforce the integrity of the remote server.

A major goal of cognitive neuroscience is to clarify the functions of central brain regions. Over the past decade, the high-level functional architecture of a region in the middle of the insect brain––the central complex––has come into focus. I will start by briefly summarizing our understanding of the central complex as a microcomputer that calculates the values of angles and two-dimensional vectors important for guiding navigational behavior. I will then describe some recent findings on this brain region, revealing (1) how neuronal calcium spikes, mediated by T-type calcium channels, augment spatial-vector calculations and (2) how an angular goal signal is converted into a locomotor steering signal. These results provide inspiration for better understanding the roles of calcium spikes and goal signals in mammalian brains.

In joint works with Kevin Yang, we consider a stochastic Laplacian growth model, that can be viewed as a continuum version of origin-excited random walks. Here, we grow the (d 1)-dimensional manifold M(t) according to a reflecting Brownian motion (RBM) on M(t), stopped at level sets of its boundary local time. An averaging principle for the RBM characterizes the scaling limit for the leading order behavior of the interface (namely, the boundary of M(t)). This limit is given by a locally well-posed, geometric flow-type PDE, whose blow-up times correspond to changes in the diffeomorphism class of the growing set. 

Smoothing the interface as we inflate M(t), yields an SPDE for the large-scale fluctuations of an associated height function.

This SPDE is a regularized KPZ-type equation, modulated by a Dirichlet-to-Neumann operator. For d=1 we can further remove the regularization, so the fluctuations of M(t) now have a double-scaling limit given by a singular KPZ-type equation. 

The talk is based on Nicolas Bergeron’s book, Sections 5.1–5.2.

Let C be an error-correcting code over a large alphabet q of block length n, and assume that a possibly corrupted codeword c is distributively stored among n servers where the ith entry is being held by the ith server. Suppose that every pair of servers publicly announce whether the corresponding coordinates are ``consistent'' with some legal codeword or ``conflicted''. What type of information about c can be inferred from this consistency graph? Can we check whether errors occurred and if so, can we find the error locations and effectively decode? We initiate the study of conflict-checkable and conflict-decodable codes and prove the following main results:

(1) (Almost-MDS conflict-checkable codes:) For every distance d = n-d 0.99. Interestingly, the code is non-linear, and we give some evidence that suggests that this is inherent. Combinatorially, this yields an n-partite graph over [q]^n that contains q^k cliques of size n whose pairwise intersection is at most n-d

While colloidal quantum dots (CQDs) are already an important building block in electro-optical devices, in the realm of quantum science and technology, they are often considered inferior with respect to emitters such as solid-state defects and epitaxial quantum dots. Despite their single-photon emission [1], demonstrations of quantum coherence and control are largely still lacking. The main obstacle towards these is spectral diffusion – stochastic fluctuations in the energy of photons emitted from an individual CQD even at cryogenic temperatures. In this talk, I will present our recent work providing, for the first time, direct and definitive proof that these fluctuations arise from stochastic electric fields in the particle’s nano environment [2]. However, the high sensitivity of CQDs to electric fields, through the quantum-confined Stark effect, can also be perceived as a feature, rather than a bug. I will present future concepts for coherent control of a single photon’s temporal wavefunction through an electric bias. Relying on tools from the terahertz and femtosecond-laser toolboxes [3,4], spectroscopy and control at fast-to-ultrafast (millisecond-to-femtosecond) timescales, will play a detrimental role in fulfilling the unique potential that CQDs hold in the field of quantum optics,.
[1] R. Tenne, U. Rossman, B. Rephael, Y. Israel, A. Krupinski-Ptaszek, R. Lapkiewicz, Y. Silberberg, and D. Oron, Super-Resolution Enhancement by Quantum Image Scanning Microscopy, Nature Photonics 13, 116 (2019).
[2] F. Conradt, V. Bezold, V. Wiechert, S. Huber, S. Mecking, A. Leitenstorfer, and R. Tenne, Electric-Field Fluctuations as the Cause of Spectral Instabilities in Colloidal Quantum Dots, Nano Lett. 23, 9753 (2023).
[3] P. Henzler et al., Femtosecond Transfer and Manipulation of Persistent Hot-Trion Coherence in a Single CdSe/ZnSe Quantum Dot, Physical Review Letters 126, 067402 (2021).
[4] P. Fischer, G. Fitzky, D. Bossini, A. Leitenstorfer, and R. Tenne, Quantitative Analysis of Free-Electron Dynamics in InSb by Terahertz Shockwave Spectroscopy, Physical Review B 106, 205201 (2022).