Voltage time dependence

On Fig. 4 the graphs of the voltage-time dependencies are given for each of the samples. From this figure it is obviously that the samples with 50 pm islands subjected to degradation not observed with other samples. 

Figure 7. Noise voltage time dependence before self-healing event.

When a voltage is applied to a dielectric (insulator), a current passes that decays with time owing to various polarization mechanisms [ 133]. Conductivity is always time-dependent. This general time dependency affects conductivity measurement for nonconductive liquids, where the peak initial current is used to calculate conductivity. Test methods are given in 3-5.5 and... 

The electrophysiological experiments reported here and done with patch-clamp techniques support this idea. The external application of MTX to isolated cardiac myocytes caused a sustained inward current which was carried by Ca . MTX did not increase the voltage-dependent Ca channel current, and both the time dependence and voltage dependence of the MTX-induced current were clearly different from those of the usual Ca channel current. These results suggest that the MTX-induced steady current is different from the usual voltage-dependent Ca channel current, and that this is possibly a current which flows through a new type of Ca -permeable channel. Tbe steady current described here may be responsible for the highly enhanced Ca influx induced by MTX and could account for the excitatory action of MTX on smooth and cardiac muscles. 

Protozoa and Porifera. The pharmacology and toxicology of the dinoflagellate toxins which act upon the voltage- and time-dependent sodium channel found in nerves of vertebrates and invertebrates, and the skeletal muscle of vertebrates, are discussed in other chapters in this volume. 

Br > Cl > I. This conductance was not time-dependent. On the other hand, Cl conductance stimulated by the Ca2+ ionophore A23187 (2.5 pM) or elevation in the free Ca2+ levels in the pipet from 100 to 500 nM was time-dependent and exhibited a nonlinear current-voltage relationship that was outwardly rectifying. The permselectivity of this Ca2+-stimulated conductance was 1 > Br > cr, distinguishing it from the cAMP-stimulated Cfr conductance. As both calcium ionophore A23187 and cAMP were shown to elevate the Cl conductance of the cornea, it is quite likely that these two types of Cr channels are present in the corneal epithelium [96,106,114],... 

Electric field sensitive dyes respond to changes in electrical membrane potential by a variety of different mechanisms with widely varying response times depending on their chemical structure and their interaction with the membrane. An understanding of the mechanisms of dye response and their response mechanisms is important for an appropriate choice of a probe for a particular application. The purpose of this chapter is, therefore, to provide an overview of the dyes presently available, how they respond to voltage changes, and give some examples of how they have been applied. Finally, because there is still scope for the development of new dyes with improved properties, some directions for future research will be discussed. 

Fig. 11. The time dependence of the threshold voltage shift for a 20 V bias applied to an a-Si H based metal-insulator-semiconductor device for various temperatures (Jackson et al., 1989a).

Time resolution of the enthalpy changes is often possible and depends on a number of experimental parameters, such as the characteristics of the transducer (oscillation frequency and relaxation time) and the acoustic transit time of the system, za, which can be defined by ra = r0/ua where r0 is the radius of the irradiated sample, and va is the speed of sound in the liquid. The observed voltage response of the transducer, V (t) is given by the convolution of the time-dependent heat source, H (t) and the instrument response function,... 

The characteristic shape of i-E curve depends on the nature of the redox couple in the condensed phase, its thermodynamics, kinetics, mass transfer, and on the voltage-time profile (E—t). In this section we will discuss various voltammetric techniques and their applications in modern chemistry. 

As a result of this excitation step, the net coherent ion motion produces a time-dependent signal on the receiver plates, termed the image current , which represents aU ions in the FT-ICR cell. The image current is converted to a voltage, ampMed, digitized, and Fourier transformed to yield a frequency spectrum that contains complete information about frequencies and abundances of all ions trapped in the cell. A mass spectrum can then be determined by converting frequency into mass because frequency can be measured precisely, the mass of an ion can be determined to one part in 10 or better. 

There are discrepancies in the amounts of harmful species tolerance that fuel cell developers establish, even for similar type fuel cells. These discrepancies are probably due to electrode design, microstructure differences, or in the way developers establish tolerance. There are some cases where the presence of certain harmful species causes immediate performance deterioration. More often, the degradation occurs over a long period of time, dependant on the developer s allowable voltage degradation rate on exposure to the specific harmful species. Here, the developer establishes an estimated cell life based on economics. The permissible amount of the harmful constituent is then determined based on its life effects. 

The analyser applies a tiny voltage V across the sample (perhaps superimposed on a pre-set or offset voltage). The magnitude ofW varies with time since it is sinusoidedly modulated. The analyser measures the respective time-dependent currents I, and hence calculates Z and the time lag 9 experienced between the current and voltage. 

Now the voltage provides information on the activity according to Nernst s law whereas Eqs (8.53) and (8.54) indicate the time dependence of the concentration. This may be overcome by expanding Eqn (8.54) by d and by introducing the relation between changes in the concentration and the stoichiometry, dCj = (NJVff) d, where A/ is Avogadro s number... 

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