Physics Colloquium - Fall 2016

Speaker: Ksenia A. Terekhova, Structural Biology, Stanford Medicine

Abstract: Topoisomerase I and III are enzymes capable of changing DNA topology by resolving negative supercoils and catenate/decatenate DNA molecules with single-stranded DNA regions. To elucidate the mechanistic differences between these two, related topoisomerases, we conducted single-molecule relaxation and decatenation studies on various types of DNA substrates. The determined kinetic characteristics of topoisomerase I and III point out the origin of their distinct behavior.

Speaker: Krishna Myneni, U.S. Army Aviation and Missile Research Development, and Engineering Center Redstone Arsenal, AL

Abstract: I will discuss our basic and applied research program in atomic physics at the U.S. Army AMRDEC, and its use of precision spectroscopy for measurements of laser-atom interactions and atomic structure, as well as for application to sensor technologies of interest to us. In basic research, we perform precision spectroscopy to validate analytically-solvable models of hyperfine-resolved pump- probe spectra of alkali atoms in the weak pump-weak probe regime. We also perform basic and applied research in utilizing fast-light phenomena for optical cavity scale-factor enhancement in gyroscopes, and in using light-pulse atom interferometry for inertial sensing at useful measurement rates.

Speaker: Charles Keeton, Department of Physics and Astronomy, Rutgers, the State University of New Jersey

Abstract: Studying galaxy formation in the young universe is one of the frontiers of observational cosmology. Recent surveys have detected very distant galaxies, but only with large investments of telescope time. Massive clusters of galaxies can bend and focus light, acting as "cosmic telescopes" that magnify faint galaxies and make them easier to detect. I will describe a comprehensive theoretical and observational project to identify outstanding cosmic telescopes and build three-dimensional mass models to account for the light bending so we can infer the intrinsic properties of gravitationally lensed sources.