Depolarization mechanisms

Small cathodes promote a high current density, which tends to retard cathodic depolarization mechanisms. 

The values of /labs were determined from the experimentally measured absorption anisotropy with Eq. 6. In viscous polyTHF, the rotational movement of dye molecules on a lOOps time scale is assumed to be negligible, and thus, does not reduce the limiting value of anisotropy. For the concentrated fluorene solutions (5 x 10 M, 1 mm cuvette), the anisotropy Tabs was not affected by FOrster depolarization mechanisms [13] due to the short time delay, tD, between probe and pump pulses when td/ti 1 [35]. 

The two most important depolarization mechanisms that give rise to a time-dependent anisotropy are fluorophore rotation and energy transfer. Energy transfer leads to depolarization as the hopping of excitation from one fluorophore to another, when not parallel, is equivalent to an angular displacement. 

Taste-active chemicals react with receptors on the surface of sensory cells in the papillae causing electrical depolarization, ie, drop in the voltage across the sensory cell membrane. The collection of biochemical events that are involved in this process is called transduction (15,16). Not all the chemical steps involved in transduction are known however, it is clear that different transduction mechanisms are involved in different taste quaUties different transduction mechanisms exist for the same chemical in different species (15). Thus the specificity of chemosensory processes, ie, taste and smell, to different chemicals is caused by differences in the sensory cell membrane, the transduction mechanisms, and the central nervous system (14). 

UF and MF use energy to depolarize membranes so as to increase flux. As is shown in Fig. 22-55, membranes and mechanical equipment are traded off to achieve an overall economic minimum. Three things can drive a design toward the use of more membranes and less mechanical equipment cheaper membranes, veiy high flux, and veiy low flux. The availability of lower-cost membranes is easiest to understand. In the five years ending in 1995, the cost of both membrane area and membrane housings was driven down by competition. 

In the case of whey, paint, and other midflux process fluids, mechanical energy at the membrane surface produces a larger dividend. For these applications, pumping for depolarization is much more important economically, but the trend toward lower-cost membranes has nonetheless shifted systems toward more membrane area. 

In the above mechanism, both hydrogen ion and molecule are utilized by SRB to convert SO to H,S. The consumption of hydrogen depolarizes the cathode and leads to an increased rate of corrosion. 

A cell may produce early afterdepolarizations that are depolarization during incomplete repolarization. This is possible if the action potential is considerably prolonged. This is the typical mechanism for elicitation of Torsade de Pointes arrhythmia, a typical complication of class III antiarrhythmics and many other drugs. 

In E-C coupling in the heart, the RyR2 channel releases Ca2+ from the SR on depolarization of the plasma membrane or T-tubules by CICR mechanisms. The... 

Smooth Muscle Tone Regulation. Figure 2 Membrane mechanisms leading to an increases in cytosolic calcium concentration, depolar, depolarisation of the membrane see text for abbreviations. 

Even when they have a partial crystallinity, conducting polymers swell and shrink, changing their volume in a reverse way during redox processes a relaxation of the polymeric structure has to occur, decreasing the crystallinity to zero percent after a new cycle. In the literature, different relaxation theories (Table 7) have been developed that include structural aspects at the molecular level magnetic or mechanical properties of the constituent materials at the macroscopic level or the depolarization currents of the materials. 

Depolarization of the cell membrane, for example, favors such events. It should also be noted that any mechanism which affects the action of the Na K pump and the Na transmembrane gradient will also affect the Na Ca exchanger flux. 

The AChR is composed of five subunits, ql2Pi - A neurotoxin attaches to the a subunit. Since there are 2 mol of the a subunits, 2 mol of neurotoxins attach to 1 mol of AChR. A neurotransmitter, acetylcholine (ACh), also attaches to the a subunit. When the ACh attaches to the AChR, the AChR changes conformation, opening up the transmembrane pore so that cations (Na" ", K ) can pass through. By this mechanism the depolarization wave from a nerve is now conveyed to a muscle. The difference between neurotoxin and ACh is that the former s attachment does not open the transmembrane pore. As a consequence, the nerve impulse from a nerve cannot be transmitted through the postsynaptic site (27). 

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