Integrated Calendar

Dr. Michael Marty is an Associate Professor in the Department of Chemistry and Biochemistry at The University of Arizona. His research applies nanodiscs with mass spectrometry to study interactions of membrane proteins with and within lipid bilayers. This “choose your own adventure” talk will cover lipidomic analysis of the monolayer of lipids surrounding membrane proteins, lipid-dependent oligomerization of amyloid proteins and viral ion channels, and/or detailed biophysical characterization of lipid binding to specific sites on membrane proteins with native mass spectrometry.

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. 

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.