Coupling, kinetic

Maurits, N.M., Fraaije, J.G.E.M. Mesoscopic dynamics of copolymer melts from density dynamics to external potential dynamics using nonlocal kinetic coupling. J. Chem. Phys. 107 (1997) 5879-5889. 

Copper oxide, oxidation of CO over, 86 Coupled heterogeneous catalytic reactions, kinetics of, 1-49, see also Kinetics coupling through catalytic surface, 9-13 experimental studies, 22-49 apparatus and procedure, 25, 26 catalysts, 26-28... 

Nakabayashi S, Tamura M, Uosaki K. 1998. Kinetic coupling of formaldehyde oxidation and oxide formation on a platinum electrode. Bull Chem Soc Jpn 71 67-71. 

If the preceding requirements are fulfilled, then the DeNOx process (function 3) does not need a large amount of reductant, as it is very often claimed the stoichiometry of 2NO -t-C H CX, = N2 + xCO/CO, + v/2 H20 should be considered. Clearly, it is generally impossible to avoid the competition between the Oads left by NO and the Oads due to 02 dissociation, for the total Q II/l. oxidation on function 3 (this competition corresponds to a kinetic coupling of at least two catalytic cycles, through Oads [13]). Both of them contribute to the total oxidation of reductants. 

The general features discussed so far can explain the complexity of these reactions alone. However, thermodynamic and kinetic couplings between the redox steps, the complex equilibria of the metal ion and/or the proton transfer reactions of the substrate(s) lead to further complications and composite concentration dependencies of the reaction rate. The speciation in these systems is determined by the absolute concentrations and the concentration ratios of the reactants as well as by the pH which is often controlled separately using appropriately selected buffers. Perhaps, the most intriguing task is to identify the active form of the catalyst which can be a minor, undetectable species. When the protolytic and complex-formation reactions are relatively fast, they can be handled as rapidly established pre-equilibria (thermodynamic coupling), but in any other case kinetic coupling between the redox reactions and other steps needs to be considered in the interpretation of the kinetics and mechanism of the autoxidation process. This may require the use of comprehensive evaluation techniques. 

The quantity and quality of experimental information determined by the new techniques call for the use of comprehensive data treatment and evaluation methods. In earlier literature, quite often kinetic studies were simplified by using pseudo-first-order conditions, the steady-state approach or initial rate methods. In some cases, these simplifications were fully justified but sometimes the approximations led to distorted results. Autoxidation reactions are particularly vulnerable to this problem because of strong kinetic coupling between the individual steps and feed-back reactions. It was demonstrated in many cases, that these reactions are very sensitive to the conditions applied and their kinetic profiles and stoichiometries may be significantly altered by changing the pH, the absolute concentrations and concentration ratios of the reactants, and also by the presence of trace amounts of impurities which may act either as catalysts and/or inhibitors. 

In case of the asymmetric hydrogenation with Rh complexes this disturbance in the equilibrium establishment is shown in pressure-dependent e.e. values (see [21 b]). Djega-Mariadassou and Boudart [3] describe this phenomenon as kinetic coupling see also G. Djega-Mariadassou, Catal. Lett. 1994, 7. In this context, we point out that under kinetic coupling conditions it is principally not possible experimentally to determine a partial order of 1 with respect to hydrogen. 

The occurrence of kinetic instabilities as well as oscillatory and even chaotic temporal behavior of a catalytic reaction under steady-state flow conditions can be traced back to the nonlinear character of the differential equations describing the kinetics coupled to transport processes (diffusion and heat conductance). Studies with single crystal surfaces revealed the formation of a large wealth of concentration patterns of the adsorbates on mesoscopic (say pm) length scales which can be studied experimentally by suitable tools and theoretically within the framework of nonlinear dynamics. [31]... 

Kinetic coupling of GTP hydrolysis and microtubule self-assembly,... 

Switch segments of Ga proteins serve as critical determinants for catalytic and effector-binding activity, thereby providing a mechanism for kinetic coupling of GTP binding to effector activity and GTP hydrolysis to signal termination. 

Thermal aging has also been widely studied for its technological interest, but most of the studies are empirical or semiempirical (using, e.g., the Arrhenius law and an arbitrary end-life criteria, from mass-loss kinetic curves). Powerful conceptual tools (radical chain kinetics, coupled diffusion-reaction schemes, etc.) are available to avoid or, at least, to reduce significantly the empiric approaches. 

Kinetic coupling elements are absent if one uses Jacobi coordinates and the coupling between the various degrees of freedom is solely due to the potential V. 

The coupling between the adiabatic states is provided by the off-diagonal elements of the matrix representation of Tnu ( kinetic coupling) while the coupling between the diabatic states arises from the off-diagonal elements of the matrix representation of Hei (potential coupling). 

Yeung, A.T. (1994) Effects of electro-kinetic coupling on the measurement of hydraulic conductivity. In Hydraulic Conductivity and Waste Contaminant Transport in Soils, ASTM STP 1142 (D.E. Daniel and S.J. Trautwein, eds.). Am. Soc. for Testing Materials, Philadelphia... 

The experiments using these optical tools consistently supported the premise that synaptic vesicle exocytosis and endocytosis are tightly coupled processes. This largely kinetic coupling is also backed up by recent molecular evidence that proteins critical for exocytosis such as synaptotagmin and synaptobrevin, are also essential for triggering endocytosis (Poskanzer et al., 2003 Deak et al., 2004 Nicholson-Tomishima and Ryan, 2004). 

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