Mechanical coupling

Stanton, R.V., Heutsough, D.S., Merz, K.M. Jr An Examination of a Density Functional-Molecular Mechanical Coupled Potential. J. Comput. Chem. 16 (1995) 113-128. 

The gas turbine in the simple cycle mode consists of a compressor (axial or centrifugal) that compresses the air, a combustor that heats the air at constant pressure and a turbine that expands the high pressure and high temperature combustion gases and produces power to run the compressor and through a mechanical coupling to the driven equipment. The power required to compress the gases varies from about 40-60 percent of the total power produced by the turbine. 

A unique electrical-to-mechanical coupling effect called piezoelectric rate coupling has been predicted to occur in the neighborhood of a shock in... 

Stirring was attempted during the ARC tests, but the iron powder interfered with the mechanically coupled stirrer [4],... 

The mechanism of the coupling between ATP hydrolysis and Ca transport is determined by the spatial relationship of the phosphorylation and ATP binding domains of the Ca -ATPase to the Ca channel involved in the translocation of calcium. Two alternative coupling mechanisms have been proposed, based on two rather different hypothetical models of the structure of the Ca -ATPase. In the conformational coupling mechanism the energy transfer between ATP hydrolysis and transport involves a mechanical coupling over long distances between... 

CUORICINO crystals are grouped in elementary modules of four elements (see Fig. 15.7) held between two copper frames joined by copper columns. PIPE pieces are inserted between the copper and TeOz, as a heat impedance and to clamp the crystals. There is a 6 mm gap between crystals with no material in between. The four detectors are mechanically coupled some of the PTFE blocks and springs act simultaneously on two crystals. 

In the second mechanism, coupling of two moles of isoprene on Pd° forms a dimethyloctadienediylpalladium complex (104) which is then reduced by formic acid with evolution of carbon dioxide ... 

The reaction is considered to proceed via a silyl anion mechanism, although the possibility of a radical-based mechanism has also been discussed.115,125 In order to clarify the mechanism, coupling experiments on a 1 1 mixture of chlorotrimethylsilane, 27 (reduction potential <—3.0 V),126 and chlorotriphenylsilane, 28 (reduction potential vs. standard calomel electrode (SCE) < —3.0 V),120 were performed, in which the mixed coupling product 1,1,1-trimethyl-2,2,2-triphenyldisilane, 29, and the homocoupling product hexaphenyldisilane, 30, only, were found,125 as indicated in Scheme 15. 

Parameters representing the effect of the chemical reactions, i.e., K and , are identically defined as for corresponding mechanisms of a dissolved redox couple (Sect. 2.4) hence their influence on the voltammetric response is rather similar as for the latter mechanisms. For these reasons, in the following part only the unique voltammetric properties of the surface electrode mechanisms coupled with chemical reactions will be addressed. 

The applicability of the foregoing procednre has been tested by modeling simple reaction under semi-infinite diffusion conditions (reaction 1.1) and EC mechanism coupled to adsorption of the redox couple (reaction (2.177)) [2]. The solutions derived by the original and modified step-function method have been compared in order to evaluate the error involved by the proposed modification. As expected, the precision of the modified step-function method depends solely on the value of p, i.e., the number of time subintervals. For instance, for the complex EC mechanism, the error was less than 2% for p>20. This slight modification of the mathematical procedure has opened the gate toward modeling of very complex electrode mechanisms such as those coupled to adsorption equilibria and regenerative catalytic reactions [2] and various mechanisms in thin-film voltammetry [5-7]. 

Fig. 15. A proposed mechanism coupling the formation of the His-Tyr bond to the oxidation of ring III of the heme in HPII. The mechanism begins with the formation of compound I shown in A. A concerted series of reactions, possibly triggered by either Aspl97/His395 or by a putative anionic species bound to compound I, results in the transfer of a hydroxyl to the heme from the H2O2 shown in C, which would facilitate spirolactone cyclization to form the final product containing the His-Tyr bond and the modified heme shown in D. Reprinted with permission of Cambridge University Press from Bravo et al. (.93).

In order to give a more quantitative view of the relative perturbation of each vibrator (C=C stretching and CH2 scissoring), the authors performed calculations for this complex based on simplified harmonic models involving mechanical couplings between the C=C... 

This indicates a lack of dynamic cohesion within the adducts i.e. the substrate has considerable freedom for reorientation within the receptor. The apparent reason for an absence of mechanical coupling is the nearly cylindrical symmetry of cucurbituril, which allows the guest an axis of rotational freedom when held within the cavity. Hence, the bound substrates show only a moderate increase in tc relative to that exhibited in solution. No relationship exists between values and the thermodynamic stability of the complexes as gauged by K (or K, cf. Tables 1 and 2). It must be concluded that the interior of cucurbituril is notably nonsticky . This reinforces previous conclusions that the thermodynamic affinity within adducts is chiefly governed by hydrophobic interactions affecting the solvated hydrocarbon components, plus electrostatic ion-dipole attractions between the carbonyls of the receptor and the ammonium cation of the ligands. 

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