The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform
Phil Attard - One of the best experts on this subject based on the ideXlab platform.
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Statistical Mechanical Theory for steady state systems. VII. Nonlinear Theory.
The Journal of chemical physics, 2007Co-Authors: Phil AttardAbstract:The second entropy Theory for nonequilibrium thermodynamics is extended to the nonlinear regime and to systems of mixed parity (even and odd functions of molecular velocities). The steady state phase space probability density is given for systems of mixed parity. The nonlinear transport matrix is obtained and it is shown to yield the analog of the linear Onsager-Casimir reciprocal relations. Its asymmetric part contributes to the flux and to the production of second entropy. The nonlinear transport matrix is not simply expressible as a Green-Kubo fluctuation equilibrium time correlation function. However, here the first nonlinear correction to the transport coefficient is given explicitly as a type of the Green-Kubo equilibrium time correlation function. The Theory is illustrated by application to chemical kinetics.
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Statistical Mechanical Theory for steady-state systems. III. Heat flow in a Lennard-Jones fluid.
Journal of Chemical Physics, 2005Co-Authors: Phil AttardAbstract:A statistical Mechanical Theory for heat flow is developed based upon the second entropy for dynamical transitions between energy moment macrostates. The thermal conductivity, as obtained from a Green–Kubo integral of a time correlation function, is derived as an approximation from these more fundamental theories, and its short-time dependence is explored. A new expression for the thermal conductivity is derived and shown to converge to its asymptotic value faster than the traditional Green–Kubo expression. An ansatz for the steady-state probability distribution for heat flow down an imposed thermal gradient is tested with simulations of a Lennard-Jones fluid. It is found to be accurate in the high-density regime at not too short times, but not more generally. The probability distribution is implemented in Monte Carlo simulations, and a method for extracting the thermal conductivity is given.
Claudio Maggi - One of the best experts on this subject based on the ideXlab platform.
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towards a statistical Mechanical Theory of active fluids
Soft Matter, 2015Co-Authors: Umberto Marini Bettolo Marconi, Claudio MaggiAbstract:We present a stochastic description of a model of N mutually interacting active particles in the presence of external fields and characterize its steady state behavior in the absence of currents. To reproduce the effects of the experimentally observed persistence of the trajectories of the active particles we consider a Gaussian force having a non-vanishing correlation time τ, whose finiteness is a measure of the activity of the system. With these ingredients we show that it is possible to develop a statistical Mechanical approach similar to the one employed in the study of equilibrium liquids and to obtain the explicit form of the many-particle distribution function by means of the multidimensional unified colored noise approximation. Such a distribution plays a role analogous to the Gibbs distribution in equilibrium statistical mechanics and provides complete information about the microscopic state of the system. From here we develop a method to determine the one- and two-particle distribution functions in the spirit of the Born–Green–Yvon (BGY) equations of equilibrium statistical mechanics. The resulting equations which contain extra-correlations induced by the activity allow us to determine the stationary density profiles in the presence of external fields, the pair correlations and the pressure of active fluids. In the low density regime we obtained the effective pair potential ϕ(r) acting between two isolated particles separated by a distance, r, showing the existence of an effective attraction between them induced by activity. Based on these results, in the second half of the paper we propose a mean field Theory as an approach simpler than the BGY hierarchy and use it to derive a van der Waals expression of the equation of state.
H K Lonsdale - One of the best experts on this subject based on the ideXlab platform.
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statistical Mechanical Theory of membrane transport
Journal of Membrane Science, 1990Co-Authors: E A Mason, H K LonsdaleAbstract:Abstract This paper is concerned with reviewing a statistical-Mechanical Theory of membrane transport, its range of validity, and its relation to previous membrane transport theories. We begin by addressing the question “what good is a Theory?” and providing our answer thereto. The commercial membrane processes are then briefly surveyed. In the main body of the paper, the statistical-Mechanical Theory is applied to several processes (ultrafiltration, reverse osmosis, gas separations, dialysis, and electrodialysis), and simplified working equations are derived for each process. The central theme is that there is a unified statistical-Mechanical Theory of membrane transport, from which all previous theories can be derived.
Fumio Hirata - One of the best experts on this subject based on the ideXlab platform.
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water molecules in a protein cavity detected by a statistical Mechanical Theory
Journal of the American Chemical Society, 2005Co-Authors: Takashi Imai, Ryusuke Hiraoka, And Andriy Kovalenko, Fumio HirataAbstract:Four water molecules confined in a small cavity of hen egg-white lysozyme were detected by means of the three-dimensional (3D) RISM Theory, a statistical−Mechanical Theory of molecular solutions. This is the first theoretical realization of confined molecules in a protein without making nonsense tricks, such as placing the molecules in the space a priori. Possible impacts which the result may have on biochemistry and biophysics, including the molecular recognition, enzymatic reactions, etc., are discussed.
Umberto Marini Bettolo Marconi - One of the best experts on this subject based on the ideXlab platform.
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towards a statistical Mechanical Theory of active fluids
Soft Matter, 2015Co-Authors: Umberto Marini Bettolo Marconi, Claudio MaggiAbstract:We present a stochastic description of a model of N mutually interacting active particles in the presence of external fields and characterize its steady state behavior in the absence of currents. To reproduce the effects of the experimentally observed persistence of the trajectories of the active particles we consider a Gaussian force having a non-vanishing correlation time τ, whose finiteness is a measure of the activity of the system. With these ingredients we show that it is possible to develop a statistical Mechanical approach similar to the one employed in the study of equilibrium liquids and to obtain the explicit form of the many-particle distribution function by means of the multidimensional unified colored noise approximation. Such a distribution plays a role analogous to the Gibbs distribution in equilibrium statistical mechanics and provides complete information about the microscopic state of the system. From here we develop a method to determine the one- and two-particle distribution functions in the spirit of the Born–Green–Yvon (BGY) equations of equilibrium statistical mechanics. The resulting equations which contain extra-correlations induced by the activity allow us to determine the stationary density profiles in the presence of external fields, the pair correlations and the pressure of active fluids. In the low density regime we obtained the effective pair potential ϕ(r) acting between two isolated particles separated by a distance, r, showing the existence of an effective attraction between them induced by activity. Based on these results, in the second half of the paper we propose a mean field Theory as an approach simpler than the BGY hierarchy and use it to derive a van der Waals expression of the equation of state.