Events Archive

Nov
09
2011
Protein Association in Dilute and Crowded Solutions
Most biological processes are mediated by mediated by protein association, and often are under kinetic rather than thermodynamic control. We have developed the transient-complex theory for protein association, which presents a framework for elucidating the mechanisms of protein association and for predicting the association rates. The transient complex refers to an intermediate along the association process, in which the two associating molecules have near-native separation and relative...
Nov
08
2011
"Simulation and Modeling of Ion Channel Functional Mechanisms and Transport"
Ion channels play vital cellular functions.  How an external simulation (e.g., cross-membrane voltage, binding of a ligand, or decrease in external pH) triggers the opening of an ion channel is at the core of its functional mechanism.  We have used molecular dynamics simulations and other computational techniques to develop models for the functional mechanisms of several ion channels, including a nicotinic acetylcholine receptor, an AMPA-subtype glutamate receptor, and the M2 proton channel of the influenza virus.  A very useful way to validate these mechanistic models is to compare changes in residue solvent...
Nov
07
2011
On the Hamilton-Jacobi variational formulation of the Vlasov equation
The Vlasov-Poisson and Vlasov-Maxwell equations possess various variational formulations or action principles. I will discuss a particular variational principle that is based on a Hamiltonian-Jacobi formulation of Vlasov theory, a formulation that is not widely known. I will show how this formulation can be reduced for describing the Vlasov-Poisson system. The resulting system is of Hamilton-Jacobi form, but with nonlinear global coupling to the Poisson equation. A description of phase (function)space geometry and relation to Hamilton-Jacobi PDE methods and weak KAM will be given.   H. Ye and P. J. Morrison Phys. Fluids 4B, 771 (1992). D. Pfirsch, Z. Naturforsch....
Nov
03
2011
Sailing the surfactant sea: Membrane hydrodynamics, geometry, and red blood cells
Nov
02
2011
"Networks of neurons create complex dynamics: Statistical physics and a simple model for the control of breathing"
Oct
31
2011
Nobel Laureate Albert Fert
Winner of the Nobel Prize in Physics in 2007, Fert speaks about his work in spintronics.
Oct
31
2011
"Spintronics: Electrons, Spins, Computers and Telephones"
Albert Fert, Nobel Prize in Physics 2007 Joint colloquium between the School of Physics and MRSEC Spintronics exploits the influence of the electron spin orientation on electronic transport. It is mainly known for the “giant magnetoresistance” (GMR) and the large increase of the hard disc capacity obtained with read heads based on the GMR, but it has...
Oct
28
2011
Hybrid quantum computing
A quantum computer uses superposition states to accomplish tasks (e.g., database search and factoring of integers) more efficiently than any known classical computing strategy. In conventional registers for quantum information processing, quantum bits are associated with individual two-level quantum systems. Separate addressing and interaction with these systems permit one-bit gates, while an interaction between systems is neededto accomplish two-bit gates. The seminar will review recent theoretical proposals to implement quantum computing in collective excitation degrees of freedom in ensembles ofidentical quantum systems. In these proposals one does not address...
Oct
26
2011
"What are theory and experiment in climate research?"
Computational models of the Earth system lie at the heart of modern climate science. Concerns about their predictions have been illegitimately used to undercut the case that the climate is changing and this has put dynamical modelling in an awkward position. I will discuss ways that we, as a community, can contribute by highlighting some of the major outstanding questions that drive climate science, and I will outline their mathematical dimensions. I will put a particular focus on the issue of simultaneously handling the information coming from data and models, and argue that this balancing act will impact the way in...
Oct
25
2011
"Mechanics of Swimming Microorganisms"
At the small scale of a cell swimming in water, inertial effects are unimportant. Therefore, the motion of the fluid is governed by Stokes equations, which are linear. Nevertheless, there are many situations in which nonlinear effects are important. In this talk I will describe two such situations. The first is swimming in a viscoelastic material, which is motivated by the fact that many microorganisms move in non-Newtonian media such as mucus. I will present a simple model that shows how fading memory affects swimming speed. We will also present experimental results for a helix swimming in a viscoelastic fluid. The second situation I will consider is the...

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