Alexander Levine

Alexander Levine
Knudsen 3-144 1
310 206 4084 (Physics)
1 310 794 4436 (Chemistry)
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Alex Levine completed his Ph.D. in physics at UCLA in 1996. Following postdocs at Exxon Research & Engineering, UPENN, and UCSB, he joined the physics department of the University of Massachusetts, Amherst as an assistant professor. In 2005 he returned to UCLA where he is now a professor of Physics & Astronomy, Chemistry & Biochemistry, and the director of the Center for Biological Physics. His main research interests involve statistical physics, mechanics of disordered elastic systems, and the dynamical phase behavior of interacting neurons. His principal work in biological physics involves the mechanics of the cytoskeleton, hydrodynamics and transport in membranes, and theoretical neuroscience. 

1996 Ph.D., UCLA 1996-1998
Postdoctoral researcher, Exxon Research 1998-2001
Postdoctoral researcher, University of Pennsylvania 2001-2002
Postdoctoral researcher, UCSB 2002-2005 Assistant Professor, UMASS 2005-2008
Assistant Professor, UCLA 2008-2011
Associate Professor, UCLA 2011-present
Professor, UCLA.

Associated Research Nonlinear-dynamics theory of up-down transitions in neocortical neural networks
Abstract: The neurons of the neocortex show ∼1-Hz synchronized transitions between an active up state and a quiescent down state. The up-down state transitions are highly coherent over large sections of the cortex, yet they are accompanied by pronounced, incoherent noise. We propose a simple model for the up-down state oscillations that allows analysis by straightforward dynamical systems theory. An essential feature is a nonuniform network geometry composed of groups of excitatory and inhibitory neurons with strong coupling inside a group and weak coupling between groups. The enhanced deterministic noise of the up state appears as the natural result of the proximity of a partial synchronization transition. The synchronization transition takes place as a function of the long-range synaptic strength linking different groups of neurons.
JPEGs: levine_nonlineardynamics.jpg (319.59 KB)
Research category: Neuroscience, Nonequilibrium physics

High energy deformation of filaments with internal structure and localized torque-induced melting of DNA
Abstract: We develop a continuum elastic approach to examining the bending mechanics of semiflexible filaments with a local internal degree of freedom that couples to the bending modulus. We apply this model to study the nonlinear mechanics of a double stranded DNA oligomer (shorter than its thermal persistence length) whose free ends are linked by a single standed DNA chain. This construct, studied by Qu et al. [Europhys. Lett., 94, 18003, 2011], displays nonlinear strain softening associated with the local melting of the double stranded DNA under applied torque and serves as a model system with which to study the nonlinear elasticity of DNA under large energy deformations. We show that one can account quantitatively for the observed bending mechanics using an augmented worm-like chain model, the helix coil worm-like chain. We also predict that the highly bent and partially molten dsDNA should exhibit particularly large end-to-end fluctuations associated with the fluctuation of the length of the molten region, and propose appropriate experimental tests. We suggest that the augmented worm-like chain model discussed here is a useful analytic approach to the nonlinear mechanics of DNA or other biopolymer systems.
PDFs: MeltingElastica_v4.pdf (11.68 MB)
Binarys: High energy deformation of filaments with internal structure and localized torque-induced melting (238.11 KB)
Research category: Biological Macromolecules

One-dimensional deterministic transport in neurons measured by dispersion-relation phase spectroscopy, Ru Wang , Zhuo Wang, Joe Leigh, Nahil Sobh, Larry Millet, Martha U Gillette, Alex J Levine and Gabriel Popescu
Abstract: Professor Levine, working with experimental colleagues at the University of Illinois at Urbana-Champaign, explores the “traffic jams” in transport of vesicles down the narrow neural filaments, axons and and dendrites.
JPEGs: One-dimensional deterministic transport.jpg(1.04 MB)
PDFs: One-dimensional-deterministic-transport.pdf(7.20 MB)
Research category: Tissues and Organisms, Nonequilibrium physics, Experimental probes