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Recent documents in Papers in Analytical Chemistryen-usThu, 03 Jul 2014 18:39:18 PDT3600Exergy use in bioenergetics
http://digitalcommons.unl.edu/chemenganalytical/4
http://digitalcommons.unl.edu/chemenganalytical/4Wed, 17 Jan 2007 13:34:36 PST
Every developed and adapted biological system extracts useful energy from outside, converts, stores it, and uses for muscular contraction, substrate transport, protein synthesis, and other energy utilizing processes. This energy management in a living cell is called the bioenergetics, and the useful energy is the exergy, which is destroyed in every irreversible process because of the entropy production. The converted exergy is the adenosine triphosphate (ATP) produced through the oxidative phosphorylation coupled to respiration in which the exergy originates from oxidation of reducing equivalents of nutrients. A living cell uses the ATP for all the energy demanding activities; it has to maintain nonvanishing thermodynamic forces, such as electrochemical potential gradient, and hence is an open, nonequilibrium system, which manages the exergy destruction and power production to adapt the fluctuations in energy demand and production within mitochondria. A simplified example presented here shows that the use of exergy analysis is helpful for understanding and analysing oxidative phosphorylation in bioenergetics.
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Dr.Y. DemirelSimultaneous Correlation of Excess Gibbs Energy and Enthalpy of Mixing by the UNIQUAC Equation
http://digitalcommons.unl.edu/chemenganalytical/3
http://digitalcommons.unl.edu/chemenganalytical/3Tue, 16 Jan 2007 12:50:16 PST
Using data for excess Gibbs energy gh. and enthalpy of mixing hE, temperature dependent parameters of the UNlQUAC equation have been estimated for twenty four systems of binary mixtures. Fifteen of them include data for gh and hE at more than one isotherm. These parameters are later tested in predicting the gh and hE data simultaneously and representing the effect of temperature on such data. The UNIQUAC equation with temperature dependent parameters represents larger values of maximum heat of mixing than does the UNlQUAC equation with the parameters independent of temperature.
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Dr.YASAR DEMIREL et al.Non-isothermal reaction-diffusion systems with thermodynamically coupled heat and mass transfer
http://digitalcommons.unl.edu/chemenganalytical/2
http://digitalcommons.unl.edu/chemenganalytical/2Tue, 12 Sep 2006 11:29:59 PDT
Non-isothermal reaction-diffusion (RD) systems control the behavior of many transport and rate processes in physical, chemical, and biological systems. A considerable work has been published on mathematically coupled nonlinear differential equations of RD systems by neglecting the possible thermodynamic couplings among heat and mass fluxes, and reaction velocities. Here, the thermodynamic coupling refers that a flux occurs without its primary thermodynamic driving force, which may be gradient of temperature, or chemical potential, or reaction affinity. This study presents the modeling equations of non-isothermal RD systems with coupled heat and mass fluxes excluding the coupling of chemical reactions using the linear non-equilibrium thermodynamic approach. For a slab catalyst pellet, it shows the dynamic behavior of composition and temperature profiles obtained from the numerical solutions of non-linear partial differential equations by Mathematica for two industrial reaction systems of synthesis of vinyl chloride and dissociation of N2O.
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Dr Y. Demirel