Network thermodynamics: a simulation and modeling method based on the extension of thermodynamic thinking into the realm of highly organized systems

Network thermodynamic analysis is applied to the diffusion of a single nonelectrolyte through a system having the configuration of an epithelial membrane. The example is used to illustrate the methods of nodal, loop, and cut set analysis of the steady state as well as time dependent states of any linear network. The extension to the nonlinear case is also discussed. A discussion of the relation between network thermodynamics and compartmental analysis and other approaches using kinetics is given. Two examples of additional mathematical constraints inherent in the network thermodynamic approach are also given. These are the nonadditive terms in hybrid multiport representations of coupled systems (e.g., Kedem-Katchalsky) and the principle of detailed balance applied to systems containing cycles.