Volume 35, Issue 4

In this paper a theory for magnetic relaxation phenomena developed in the framework of thermodynamics of irreversible processes (TIP) with internal variables by G. A. Kluitenberg (G.A.K.) and the author is reviewed. Analogies and correlations with thermodynamic theories with internal variables for mechanical distortional phenomena and dielectric relaxation phenomena, derived, respectively, by G. A. K., and by G. A. K. and the author, following the same procedure, are put forward as evidence. It is assumed that if n different types of irreversible microscopic phenomena give rise to magnetic relaxation, it is possible to describe these microscopic phenomena splitting the total specific magnetization in n + 1 parts and introducing n of these partial specific magnetizations as internal variables in the thermodynamic state space. The phenomenological equations are formulated in the anisotropic and isotropic cases. Finally, linearizing the equations of state, generalizations of the Snoek equation for magnetic relaxation phenomena are obtained by eliminating the internal variables. Some results obtained in the paper are new.

The aim of this contribution is to review the application of thermodynamics to live cultures of microbial and other cells and to explore to what extent this may be put to practical use. A major focus is on energy dissipation effects in industrially relevant cultures, both in terms of heat and Gibbs energy dissipation. The experimental techniques for calorimetric measurements in live cultures are reviewed and their use for monitoring and control is discussed. A detailed analysis of the dissipation of Gibbs energy in chemotrophic growth shows that it reflects the entropy production by metabolic processes in the cells and thus also the driving force for growth and metabolism. By splitting metabolism conceptually up into catabolism and biosynthesis, it can be shown that this driving force decreases as the growth yield increases. This relationship is demonstrated by using experimental measurements on a variety of microbial strains. On the basis of these data, several literature correlations were tested as tools for biomass yield prediction. The prediction of other culture performance characteristics, including product yields for biorefinery planning, energy yields for biofuel manufacture, maximum growth rates, maintenance requirements, and threshold concentrations is also briefly reviewed.