Integrated Calendar

Chirality or handedness is one of the deepest and most persistent mysteries in the sciences, from the molecular asymmetry of life’s building blocks to the emergence of homochirality in early prebiotic systems. Why is chirality “contagious, ” as when a tiny fraction of chiral dopant induces cholesteric twist in an achiral nematic? What mechanisms can spontaneously break mirror symmetry in systems composed entirely of achiral molecules? These questions lie at the intersection of physics, chemistry, and the origins of life. Using the tools of statistical physics, we explore a mechanism that focuses on the role of intramolecular degrees of freedom, in which achiral molecules switch between degenerate configurations of opposite handedness. Theoretical analysis predicts a phase diagram featuring a spatially segregated cholesteric phase with alternating domains of left- and right-handed chiral twist, alongside racemic nematic and isotropic phases. Our model also demonstrates how chiral molecular fluctuations influence the helical twisting power of dopants in the nematic phase. Monte Carlo simulations validate the predicted phase diagram and reveal pattern formation and coarsening in the segregated cholesteric phase. These results suggest that molecular fluctuations between degenerate chiral configurations may be a common mechanism driving cooperative chiral order in soft materials composed of achiral molecules.FOR THE LATEST UPDATES AND CONTENT ON SOFT MATTER AND BIOLOGICAL PHYSICS AT THE WEIZMANN, VISIT OUR WEBSITE: https://www.bio  

Financial systems are becoming increasingly digital and decentralized, demanding a practical fusion of distributed systems security and economic theory. A key enabler of this change, blockchain technology, promises more private and egalitarian economic mechanisms, built by facilitating consensus between pseudonymous actors. However, the theoretical security of these systems may mask significant real-world risks. In this talk, I will present recent advances in bridging this gap between theory and practice. First, I will discuss the resolution of a decade-old puzzle: the lack of observed attacks on major consensus mechanisms. I will then distill the lessons learnt into a holistic approach to designing robust mechanisms for distributed pseudonymous systems and demonstrate its adoption in practice using several lines of work.

MXenes are the fastest-growing family of two-dimensional (2D) materials. Unlike most other 2D materials, they lack bulk analogues when restacked because of their unique structure and surface terminations. They represent a new class of 2D transition-metal carbides/nitrides, not merely exfoliated van der Waals solids. They have a general formula Mn+1XnTx, where M is a transition metal, X is carbon and/or nitrogen, T represents surface terminations (O, OH, halogen, chalcogen, etc.), and n = 2—5. About 50 stoichiometric MXene compositions and dozens of solid solutions on M and X sites have already been reported. Given the infinite number of possible solid-solution compositions and combinations of surface terminations, MXenes offer an opportunity for computationally driven atomistic design of inorganic 2D structures with unique properties. MXenes exhibit electronic, optical, mechanical, and electrochemical properties that clearly distinguish them from other materials. Moreover, these properties are tunable by design and can be modulated using an ionotronic approach, leading to breakthroughs in fields ranging from optoelectronics and communication to electrochemical energy storage, catalysis, sensing, and medicine. In this talk, I’ll discuss methods for MXene synthesis and processing, the effects of MXene chemistry on their properties, and provide examples of important applications where MXenes outperform other materials. 

Most efficient chemical processes used in industry rely on heterogeneous catalysis. While the search for more sustainable processes and the changes in environmental policies impose the continuous development of more efficient catalysts, we have currently little understanding of the structure of the actives in these processes. Hence, due to their inherent complexity, heterogeneous catalysts have been mostly developed empirically.Here, we will show how constructing active sites, one atom at a time on surfaces, enables molecular-level understanding and implementation of rational approaches for the improvement of catalytic processes. We will first illustrate how this approach enables to generate selective single-site catalysts. We will next show how from these isolated (single) sites, one can generate and understand far more complex systems such as supported nanoparticles, where interfaces, alloying… play a critical role. This lecture will be developed around these themes and will show how the development of advanced characterization tools augmented by computational approaches can provide useful information to bridge the gap between fundamental and applied (industrial) catalysis.