Current-voltage relationships

The impedance area product, ZM, of a diode may be obtained from differentiation of the diode current—voltage relationship and may be expressed as follows, at zero appHed basis. 

Intravenous administration of magnesium sulfate (1-5 g) is used for the termination of torsade de pointes arrhythmia. The underlying electrophysiological mechanism is not well understood. It includes changes of the current-voltage relationship of Iki and Ca2+ channel blockade. 

The current-voltage relationship is a plot of the current through a channel versus the voltage of the membrane potential. 

Due to the small amplitude of the superimposed voltage or current, the current-voltage relationship is linear and thus even charge-transfer reactions, which normally give rise to an exponential current-potential dependence (Chapter 4), appear as resistances, usually coupled with a capacitance. Thus any real ohmic resistance associated with the electrode will appear as a single point, while a charge transfer reaction (e.g. taking place at the tpb) will appear ideally as a semicircle, i.e. a combination of a resistor and capacitor connected in parallel (Fig. 5.29). 

Figure 10. The current-voltage relationship of the MTX-induced steadily flowing current. Each value is the difference between the steady-state current before and 4 min after the administration of MTX (10 g/mL). (Reproduced with permission from Ref. 24. Copyright 1987 Macmillan)...

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],... 

Fig. 21.5. Levamisole-activated single-channel currents activated by 30 pM levamisole in a cell-attached patch and current voltage relationship. The rectangular current pulses were recorded at different patch potentials to determine the relationship between channel current and potential. The slope was linear with a conductance of 34 pS.

Nelson This window is just a way to describe the current—voltage relationship. The open probability is finite it doesn t drop to zero. The question is, is enough Ca2+ coming in The open probability of the Ca2+ channel is increasing as you go from —100 to —50 mV. The question is whether enough Ca2+ is entering. 

Serotonergic dorsal raphe neurons basic properties, 171-175 identification of, 171-172 current-voltage relationships in, 177 and LSD, 175-178 noradrenergic activations of, 175... 

Only experiments as described in sections Current-Voltage Relationship, Background Current and Selectivity will supply sufficient information to select the optimum detection potential. Similar experiments should therefore always be performed when developing a method of analysis using HPLC with electrochemical detection, see note in section Background Current. ... 

The final choice for a detection potential usually is, as has been seen in sections Current-Voltage Relationship, Background Current and Selectivity, a compromise between sensitivity, stability of response and selectivity based on the following considerations ... 

Voltammetry is a part of the repertoire of dynamic electrochemical techniques for the study of redox (reduction-oxidation) reactions through current-voltage relationships. Experimentally, the current response (i, the signal) is obtained by the applied voltage (.E, the excitation) in a suitable electrochemical cell. Polarography is a special form of voltammetry where redox reactions are studied with a dropping mercury electrode (DME). Polarography was the first dynamic electrochemical technique developed by J. Heyrovsky in 1922. He was awarded the Nobel Prize in Chemistry for this discovery. 

Butler-Volmer equation for the current-voltage relationship ... 

Under open-circuit conditions no net current can flow so that the total rate of the anodic reactions must equal that of the cathodic reactions. Applying this condition allows the e.m.f. to be determined if the current-voltage relationships are known for the charge-transfer processes.15... 

This has led to a relatively profound development of theories for the current—voltage relationship of porous electrodes [105, 106]. The... 

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