ABSTRACT
The process of reaching complete equilibrium is treated by nonequilibrium thermodynamics as occurring over a sequence of partial equilibrium states. The entropy of the coarse-grained distribution in the state of thermodynamic equilibrium is greater than in its initial state. In general, equilibration takes place in stages and is characterized by several stochastization times with vastly different orders of magnitude. The state of partial equilibrium, that is, a nonequilibrium thermodynamic state, is uniquely specified by the values of appropriate thermodynamic variables. In particular, they determine the probability density for the system. All processes of nonequilibrium thermodynamics that proceed at finite speeds, including all biochemical processes, are associated with energy dissipation and hence are irreversible. The energy dissipated in a nonequilibrium process going through states of partial equilibrium is related to a lack of balance between internal and external thermodynamic forces acting on the system.
