ENERGY AND ENTROPY BALANCES IN A COMBUSTION CHAMBER: ANALYTICAL SOLUTION.

An analytical solution of the energy and entropy balance equations for a combustible gas mixture contained in an open combustion chamber, for example of an internal combustion engine, is presented. The solution is free of major assumptions and is in a form suitable for incorporating any detailed models for the effects of wall heat transfer, wall thermal boundary layer, non-uniform temperature distributions in the burnt mixture, crevice regions, mass exchange through the boundaries of the chosen control volume and other similar effects. Explicit expressions for the instantaneous mass of burnt mixture and for the entropy generated by irreversibility are presented as functions of pressure and volume history of the combustion chamber and properties of the gas mixtures

CONSTRAINED-EQUILIBRIUM APPROACH TO NONEQUILIBRIUM DYNAMICS.

We review the constrained-equilibrium method for the description of the time-dependent behavior of dynamical systems in nonequilibrium states. The method is presented in a general mathematical framework that is relevant not only to thermodynamics and chemical kinetics, but also to economics, control theory and other sciences. We emphasize that a successful application of the method requires a deep understanding of the internal mechanisms governing the system dynamics and, in particular, their time scales and time invariants

Transition state theory can be used in studies of enzyme catalysis: lessons from simulations of tunnelling and dynamical effects in lipoxygenase and other systems

The idea that enzyme catalysis involves special factors such as coherent fluctuations, quantum mechanical tunnelling and non-equilibrium solvation (NES) effects has gained popularity in recent years. It has also been suggested that transition state theory (TST) cannot be used in studies of enzyme catalysis. The present work uses reliable state of the art simulation approaches to examine the above ideas. We start by demonstrating that we are able to simulate any of the present catalytic proposals using the empirical valence bond (EVB) potential energy surfaces, the dispersed polaron model and the quantized classical path (QCP) approach, as well as the approximate vibronic method. These approaches do not treat the catalytic effects by phenomenological treatments and thus can be considered as first principles approaches (at least their ability to compare enzymatic reaction to the corresponding solution reactions). This work will consider the lipoxygenase reaction, and to lesser extent other enzymes, for specific demonstration. It will be pointed out that our study of the lipoxygenase reaction reproduces the very large observed isotope effect and the observed rate constant while obtaining no catalytic contribution from nuclear quantum mechanical (NQM) effects. Furthermore, it will be clarified that our studies established that the NQM effect decreases rather than increases when the donor–acceptor distance is compressed. The consequences of these findings in terms of the temperature dependence of the kinetic isotope effect and in terms of different catalytic proposals will be discussed. This paper will also consider briefly the dynamical effects and conclude that such effects do not contribute in a significant way to enzyme catalysis. Furthermore, it will be pointed out that, in contrast to recent suggestions, NES effects are not dynamical effects and should therefore be part of the activation free energy rather than the transmission factor. In view of findings of the present work and our earlier works, it seems that TST provides a quantitative tool for studies of enzyme catalysis and that the key open questions are related to the nature of the factors that lead to transition state stabilization

Control of O-glycan branch formation. Molecular cloning and characterization of a novel thymus-associated core 2 beta1, 6-n-acetylglucosaminyltransferase.

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Discussion on "Foundations of the second law"

This article reports an open discussion that took place during the Keenan Symposium "Meeting the Entropy Challenge" (held in Cambridge, Massachusetts, on October 4, 2007) follow-ing the short presentations - each reported as a separate article in the present volume - by Seth Lloyd, Owen Maroney, Silviu Guiasu, Ping Ao, Jochen Gemmer, Bernard Guy, Gian Paolo Beretta, Speranta Gheorghiu-Svirschevski, and Dorion Sagan. All panelists and the audience were asked to address the following questions Why is the second law true? Is it an inviolable law of nature? If not, is it possible to develop a perpetual motion machine of the second kind? Are second law limitations objective or subjective, real or apparent, due to the nature of physical states or the representation and manipulation of information? Is entropy a physical property in the same sense as energy is universally understood to be an intrinsic property of matter? Does the second law conflict with quantum mechanics? Are the differences between mechanical and thermodynamic descriptions of physical phenomena reconcilable? Does the reversible law of motion of hamiltonian mechanics and quantum, mechanics conflict with the empirical observation of irreversible phenomena? © 2008 American Institute of Physics