Electrical field method

Stopped-Flow Instrumentation and Design 92 Application of Stopped-Flow Techniques to Soil Constituent Reactions 93 Electric Field Methods 95 Introduction 95... 

Relaxation methods can be classified as either transient or stationary (Bernasconi, 1986). The former include pressure and temperature jump (p-jump and t-jump, respectively), and electric field pulse. With these methods, the equilibrium is perturbed and the relaxation time is monitored using some physical measurement such as conductivity. Examples of stationary relaxation methods are ultrasonic and certain electric field methods. Here, the reaction system is perturbed using a sound wave, which creates temperature and pressure changes or an oscillating electric field. Chemical relaxation can then be determined by analyzing absorbed energy (acous-... 

Another chemical relaxation method that can be used to determine the kinetics of fast reactions on soil constituents is the electric field pulse technique. This technique was developed by Hachiya et al. (1980) to study the kinetics of I03 adsorption and desorption on Ti02 and by Sasaki et al. (1983) to investigate ion-pair formation on the surface of a-FeOOH. Excellent review articles on electric field methods are found in DeMaeyer (1969), Hemmes (1979), and Eyring and Hemmes (1986). 

Hemmes, P. (1979). Electric field methods. In Techniques and Applications of Fast Reactions in Solutions (W. J. Gettins and E. Wyn-Jones, eds.), Vol. 50, pp. 95-101. Reidel Publ., Dordrecht, The Netherlands. 

This model, as previously discussed, allowed large charge to be built up at various atomic positions in the molecule. The reason for this is that the atomic potentials do not act to counter this charge depletion or growth as would be expected in a self-consistent (electric) field method. Although this degraded the accuracy of EHT theory when applied to ionic situations, it simply was not possible to calculate the structure of transition metal complexes with this scheme. 

Tsong, T. Y. Active cation pumping of Na,K-ATPase and SR Ca-ATPase induced by an electric field. Methods Enzymol. 157, 240-251. 

Tsong, T. Y. Tomita, M. Lo, M. M. S. Pre-selection of B-lymphocytes by antigen for fusion to myeloma cells by pulsed electric field method. In Molecular Mechanisms of Membrane Fusion Oki, S. et al., Eds. Plenum New York pp 223-236. 

Electric field methods for the study of fast kinetics encompass a number of diverse experimental techniques. If the applied field is small the techniques are usually considered under the heading of dielectric relaxation techniques. These will be discussed elsewhere in this volume. At high field strengths there is an increased dissociation of weak electrolytes, the so called second Wien effect. Quantitatively this effect is given by the equation of Onsager (1)... 

The radiation-induced isotope exchange has been studied by the electric field method [263]. Thus G(HD) = 6 10 has been attained which corresponds to... 

The stationary electric field method of Eigen enables rate coefficients of ionic reactions to be measured at very low concentrations (because the solution must have a very low conductivity) it has led to the measurement of the rate of neutralization of by OH ions in ice, and can be applied to non-aqueous solvents and even to semiconductors. 

The electric field-induced Freedericksz transition method has been used primarily to detomine K and K3, although it is possible to obtain K2 with reduced accuracy from the threshold voltage for twisted nematic samples. In order to obtain satisfactwy values for K2, it was necessary to use a magnetic field-induced Freedericksz transition, but recently [6] a new electric field method has been devised using an in-plane electrode configuration. 

The above-mentioned way of photogeneration efficiency determination is possible only when there is a nonzero electric field in the moment of illumination. The measurement is also difficult when the electric field is too small, because of the noise and the presence of deep traps. The evaluation of the photogeneration efficiency for the zero electric field is achievable by using the delayed electric field method, which is the modification of this technique. In this method the external electric field is applied to the electrodes after extinguishing the light pulse with delay time d (Figure 17(b)). 

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