Relaxation cyclic

If a strain-controlled fatigue experiment is performed at a non-zero mean strain, cyclic relaxation may occur in addition to cyclic hardening or softening, with the mean stress decreasing over time (figure 10.31(a)). If, on the other hand, the experiment is stress-controlled at a non-zero mean stress, the hys-... 

Steam is injected into a reservoir to reduce oil viscosity and make it flow more easily. This technique is used in reservoirs containing high viscosity crudes where conventional methods only yield very low recoveries. Steam can be injected in a cyclic process in which the same well is used for injection and production, and the steam is allowed to soak prior to back production (sometimes known as Huff and Puff). Alternatively steam is injected to create a steam flood, sweeping oil from injectors to producers much as in a conventional waterflood. In such cases it is still found beneficial to increase the residence (or relaxation) time of the steam to heat treat a greater volume of reservoir. 

By changing from the simplest to larger aliphatic and cyclic ketones, structural factors may be introduced which favor alternative unimolecular primary photoprocesses or provide pathways to products not available to the simple model compound. In addition, both the increase in molecular size and irradiation in solution facilitate rapid vibrational relaxation of the electronically excited reactant as well as the primary products to thermally equilibrated species. In this way the course of primary and secondary reactions will also become increasingly structure-selective. In a,a -unsym-metrically substituted ketones, the more substituted bond undergoes a-cleavage preferentially. 

To initiate a chemical relaxation it is necessary to perturb the system from its initial equilibrium position. This is done by applying a forcing function, which is an appropriate experimental stress to which the system responds with a shift in equilibrium configuration. Forcing functions can be transient (a sudden, essentially discontinuous Jolt ) or periodic (a cyclic stress of constant frequency). 

Most proton transfer reactions are fast they have been carefully studied by relaxation methods. A system consisting of a conjugate acid-base pair in water is a three-state cyclic equilibrium as shown in Scheme IV. [The symbolism is that used by Bemasconi. ... 

By constructing a cyclic version as in Scheme VII it is readily seen that this is a four-state system, so it possesses three relaxation times. 

FIGURE 2.17 Differential efficiency of receptor coupling for cardiac function, (a) Guinea pig left atrial force of contraction (inotropy, open circles) and rate of relaxation (lusitropy, filled circles) as a function (ordinates) of elevated intracellular cyclic AMP concentration (abscissae). Redrawn from [6]. 

If MLCK activates contraction by increasing myosin phosphorylation, then an increase in the activity of myosin light chain phosphatase, MLCP, by decreasing the fraction of myosin which is phosphorylated, should lead to relaxation from the active (contractile) state. Cyclic adenosine monophosphate (AMP) is a strong inhibitor of smooth muscle contraction and it has been suggested that activation of MLCP could result from its phosphorylation via cAMP activated protein kinase (see Figure 5). 

K Relaxation mechanism was also proposed [130-133], The % relaxation originates from cyclic delocalization of % electrons in the double bond through the hyperconjugation with a bonds on the saturated ring atoms under control of the orbital phase property [134, 135],... 

Kamata, K., Miyata, N. and Kasuya, Y. (1989). Impairment of endothelium-dependent relaxation and changes in levels of cyclic GMP in aorta from streptozocin-induced diabetic rats. Br. J. Pharmacol. 97, 614-618. 

P2-Agonists cause airway smooth muscle relaxation by stimulating adenyl cyclase to increase the formation of cyclic adenosine monophosphate (cAMP). Other non-bronchodilator effects have been observed, such as improvement in mucociliary transport, but their significance is uncertain.11 P2-Agonists are available in inhalation, oral, and parenteral dosage forms the inhalation route is preferred because of fewer adverse effects. 

Chain and ring macromolecules are topologically distinct. Thus it is not surprising that many differences in their microscopic properties are observed [127], Besides many other experimental techniques, which were applied to specify these differences, NSE was used to compare the center of mass diffusion and the internal relaxation of linear and cyclic PDMS systems in dilute solutions under good solvent conditions [120,128,129]. An important parameter for these investigations was the molecular mass, which was varied between 800 and 15400 g/mol and which was almost identical for the corresponding linear (L) and ring (R) systems. 

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