Volume 32, Issue 4

We review recent efforts aimed at analyzing energy transduction processes in biological systems from the perspective of mesoscopic non-equilibrium thermodynamics. The inherent nonlinear nature of many of these systems, which undergo activated processes, has over the years impeded the use of classical non-equilibrium thermodynamics for their description, because this theory accounts only for the linear regime of these processes. The diffculty of putting non-equilibrium thermodynamics methods into a broader scope has recently been overcome. It has been shown that if one assumes local equilibrium at short time and length scales, in the mesoscale domain, the limitation of only providing linear laws can be removed and Arrhenius type nonlinear laws can be derived. The new theory proposed here provides a scenario under which transformations taking place in chemical and biological processes can be studied. We show in this paper how the theory can be applied to describe energy conversion processes in molecular motors and pumps and conclude that both systems can be studied by means of this common framework.

When an electrically charged system is subjected to the action of an electromagnetic field, it responds by generating an electrical current. In the case of amulticomponent plasma, other effects, the so-called cross effects, influence the flow of charge as well as the heat flow. In this paper we discuss these effects and their corresponding transport coeffcients in a fully ionized plasma using Boltzmann's equation. Applications to nonconfined plasmas, specially to those prevailing in astrophysical systems, are highlighted. Also, a detailed comparison is given with other available results.

In open systems, a number of nonequilibrium states that are stationary, oscillatory, or chaotic can coexist under given boundary conditions. These states are either stable or unstable. When a system is in an unstable state, it evolves to a coexistent stable state if subjected to appropriate perturbations. The present work is concerned with characterizing such spontaneous transitions from a thermodynamic viewpoint by focusing on thermodynamic forces and flows consisting of the rate of entropy production. It has been shown in a previous paper that the sum of products of the differences of these forces and flows between two nonequilibrium states is invariably nonpositive for a variety of open systems. It is here hypothesized on this basis that either the thermodynamic forces or the flows or both change in a way as to lower the entropy production for spontaneous transformations from unstable to stable states. This hypothesis is verified for flow reactors with diverse chemical schemes including cubic autocatalysis, the Brusselator, and the Oregonator. It may thus be concluded that spontaneous processes in open systems are marked by the moderation of thermodynamic forces or flows.

This study analyzes a complete set of balance equations for mesoscopic electromagnetic (EM) mixtures. Introducing the mesoscopic surface balance equation enables the formulation of the mesoscopic Maxwell's equations, which in turn lead to the macroscopic EM equations by the mesoscopic average. This study gives the mesoscopic EM body force, body couple, and energy supply and thoroughly discusses the EM contributions to the balance equations for linear momentum, angular momentum, and energy, from the mesoscopic quantities to their macroscopic counterparts. The EM mixture is applied to the derivation of the balance equations for an EM microcontinuum. In addition, the first-order moments for the mesoscopic Maxwell's equations are used to recover the equations in micromorphic electromagnetism.

This paper models a microcontinuum as a mixture with continuous diversity. Balance equations for a microcontinuous medium are discussed from the viewpoint of mesoscopic continuum mechanics. The macroscopic field quantities are redefined in terms of the mesoscopic averages rather than by taking spatial averages in a macroelement. The averages of the mesoscopic balance equations of mass, linear momentum, angular momentum, and energy produce their macroscopic counterparts. With the mixture formulation, the kinetic fluxes, which are missing in the derivations by other macroscopic approaches, are naturally incorporated into the stress tensor, couple stress tensor, and heat flux. For a microcontinuum, the balance equation of microinertia is the second-moment equation for the mesoscopic balance of mass. Introducing the mesoscopic distribution function can produce the explicit expression for the general macroscopic n -th moment equation.

It is shown that the vanishing of thermoelectric effects in superconductors is a simple consequence of the positive character of entropy production and of the Onsager relations, if the thermal conductivity of the superconducting sample is finite.