לוח שנה משולב

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.

 Vision is an active sense in which an animal's gaze and pupil shape the content of the retinal image. In the first part of my talk, I will discuss how the viewing strategies of mice align with the neural architecture of their visual system to accomplish an essential visual task: predation. In the second part of my talk, I will compare the hunting behavior of mice to that of a specialized predator, similar in size but distant in evolution, and present our initial insights into the organization of visual information in this animal. Finally, I will present ongoing work indicating that the pupillary reflex arc implements a more complex stimulus-response function than previously thought. I will discuss the underlying neural mechanisms and potential purpose and show conservation from mice to humans. 

Let f be a stationary Gaussian process on R with compactly supported spectral measure. The expected number of zeroes is computed by the celebrated Kac-Rice formula, and much is known about their typical behavior. In this talk we are interested in their large deviations: What is the probability to see many more zeroes (overcrowding) or many less zeroes (undercrowding) than expected in a long interval?

We show that overcrowding and undercrowding probabilities exhibit a phase transition between exponential and Gaussian behavior.
The critical points of the transition are determined by the support of the spectrum.
This result complements previous bounds given by Basu-Dembo-F.-Zeitouni and by Priya.

Based on ongoing joint work with Ohad Feldheim and Lakshmi Priya.

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.

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.

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.