לוח שנה משולב

The most obvious and distinctive feature of an amorphous solid is its heterogeneous microscopic structure. A central issue is how such disorder governs the elastic properties of an amorphous solid so that it has different behavior from its crystalline counterpart. I will show how such disorder on the microscale determines the elastic properties on long length scales. This theoretical approach ultimately allows us to control a material’s elastic properties and to understand how a material ages and stores memories.

I start by studying the change in an amorphous solid’s elastic properties upon the removal of a single bond. I show that the change in moduli, which has a broad and universal shape, is uncorrelated for different imposed strains. Thus, by selectively removing a small number of bonds, the precise global and local elastic behavior of the solid can be controlled. This in turn suggests that small changes in bond properties, which occur naturally as a solid ages, can dramatically alter the solid’s elastic response; the history of imposed strains is encoded in the non-linear response and the aging process, usually considered to be detrimental, can be harnessed to design materials with novel desired properties.

The magnetoelectric effect in solids refers to the induction of magnetization with the application of an electric field or the induction of an electric polarization with the application of a magnetic field. Multiferroics are a special class of magnetoelectric materials with the coexistence of spontaneous magnetic and polar orders. In the past few decades, multiferroics are at the forefront of contemporary condensed matter physics. These materials have the potential for many practical applications including transducers and sensors for magnetic fields, spintronics, and four state logic energy-efficient memory devices. Geometrically frustrated magnets are promising materials where exotic arrangements of spins lead to the discovery of many interesting multiferroic properties. The low-dimensional geometrically frustrated magnets are natural playgrounds for various exotic spin arrangements. These systems can have varieties of spin arrangements like spin chains, ribbons, ladders, Kagome layers, and staircase-like spin patterns etc. In low-dimensional magnetic systems, the presence of complex interplay among the nearest and next-nearest atomic interactions, and large spin-orbit coupling leads to the generation of many complex magnetic and electric ground states. In my talk, I will present findings of magnetoelectricity in some geometrically frustrated metal oxides.

Following a review of G-CLEF – a first light High-R spectrograph for the Giant Magellan Telescope, I will present a concept extreme high resolution spectrograph optimized for molecular oxygen detection, a prominent biomarker in Earth atmosphere, using the transmission spectroscopy method. The instrument is based on the transmission properties of Fabry Perot Interferometers, and despite its modest dimensions is capable of achieving spectral resolution and sampling frequency in excess of R~300,000. I will discuss design parameters and the unique aspects that needs to be taken into account in the design of an FPI based instrument, and conclude with MC simulation results demonstrating the advantages of such a novel instrument.

Protein self-assembly into functional complexes underlies biological function. In this talk, I will describe our efforts at understanding filamentous protein self-assembly from a biophysical point of view. The talk will cover both the mechanisms of formation of pathological amyloid fibrils, associated with neurodegenerative disorders in humans, as well as functional roles for protein fibrils in new materials.