Events Archive

Nov
17
2011
Deriving reduced models for plasma physics via Dirac’s theory of constrained Hamiltonian systems
We present a Hamiltonian derivation of a class of reduced models in plasma physics obtained by imposing dynamical constraints on a parent Hamiltonian model. We will consider MHD equations and Maxwell-Vlasov equations as parent models. It is shown that the Poisson bracket associated with these reduced models is the Dirac bracket obtained from the Poisson bracket of the parent model.
Nov
16
2011
Mechanics Matters… For Biological Processes on the Nanoscale
A cell is not just a small test tube in which biochemical reactions take place, but it also has a complex and highly dynamic mechanical structure. I will discuss the underlying physical principles that govern cellular mechanics on the nanoscale, and explore how DNA mechanics, on its own and within the context of a heavily crowded, constrained and perpetually fluctuating cellular environment, affects biological function. For example, forces of less than hundred femtonewtons can mechanically switch genes on and off by preventing the formation of regulatory DNA-protein complexes. Special emphasis will be placed on the role of intracellular fluctuations and...
Nov
10
2011
NASA’s Kepler Mission: A Search for Habitable Planets
The Kepler Mission, NASA Discovery mission #10, is specifically designed to survey a portion of our region of the Milky Way galaxy to discover dozens of Earth-size planets in or near the habitable zone and determine how many of the billions of stars in our galaxy have such planets. Results from this mission will allow us to place our solar system within the continuum of planetary systems in the Galaxy.
Nov
10
2011
"Nonlinear and Neural Dynamics in Josephson Networks"
Superconducting Josephson Junctions are one of the most active areas of research in Condensed Matter Physics today.  One unique aspect of Josephson Junctions is the nonlinear relation between the phase of the wave function and the supercurrent flowing though the junction.  This manifests itself in a nonlinear, pendulum-like equation for the dynamics of the phase when the junction is placed in circuit.  Josephson junctions can be fabricated with adjustable parameters, measured in a straightforward fashion, and easily scaled to large network sizes.  In addition, a large Josephson junction circuit measured over a long time contains dynamics...
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.

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