The effect of an electric field

An electric or magnetic field can orient the polymer, and measurement of this process gives information on the rotational motion of polymers in solution. Using the Smoluchowski equation, we shall consider the orientation caused by an electric field. 

Elementary electrostatics says that if an object with dipole moment p is placed in an electric field E i), it feels a torque 

The dipole moment p consists of two parts, the permanent dipole pp and 

The orientation of the polymers can be studied by measurement of the dipole moment 

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The molecular simulations also showed that electro-osmosis is also observed in aqueous electrolyte solutions, as long as the external electric field is reversed periodically to prevent the ions from accumulating near the membrane. An example of this is shown in Fig. 10, which shows the effect of an electric field on a 4.67 mole percent aqueous LiCl solution at 25°C. It is quite clear that the mobility of the solvent molecules increases as a result of... 

Figure 4.54 The effect of an electric field gradient (EFG) creating asymmetry in the electron distribution round a gold nucleus, leading to a quadrupole splitting in the Mossbauer spectrum. (Reproduced with permission from Gold Bull., 1982,15, 53, published by World Gold Council.)...

Kabanov and Zingel [352] have recently published a comprehensive review of studies of the effect of application of continuous or periodic electric fields on the reactant during thermal decomposition of a solid. They comment on the superficiality of most of the work discussed. The application of an electric field is contrasted with the effect of selected additives as a means of obtaining information on the mechanism of a decomposition reaction. Both may alter the concentration of free electrons in the solid, but the effect of the field is more apparent in the vicinity of the surface. An example of an investigation of the effect of an electric field on a reaction is to be found in the work of the Panafieu et al. [373] on KN3. 

FIGURE 17.4 The effects of an electric field on nuclear radiation. The direction of deflection shows that a-rays are positively charged, p-rays negatively charged, and y-rays uncharged. 

The Wilhelmy hanging plate method (13) has been used for many years to measure interfacial and surface tensions, but with the advent of computer data collection and computer control of dynamic test conditions, its utility has been greatly increased. The dynamic version of the Wilhelmy plate device, in which the liquid phases are in motion relative to a solid phase, has been used in several surface chemistry studies not directly related to the oil industry (14- 16). Fleureau and Dupeyrat (17) have used this technique to study the effects of an electric field on the formation of surfactants at oil/water/rock interfaces. The work presented here is concerned with reservoir wettability. 

The effect of an electric field on the ensuing chemistry can be studied experimentally, although interpretations of the results are not always straightforward. The main disadvantage of the gas-phase work is complications due to the wall effect At low densities, some reactions such as neutralization take place mainly on the walls these are not easy to account for. 

In principle the effect of an electric field on chemical equilibria can be described by the thermodynamic relationship described by Eq. (19) ... 

Capillary electrophoresis (CE) separates sample components within a capillary tube under the effect of an electric field employed across the two ends of the capillary. The different... 

Saunders, M. J., 1980. The effect of an electric field on the backscattered radiance of a single water droplet, in Light Scattering by Irregularly Shaped Particles, D. Schuerman (Ed.), Plenum, New York, pp. 237-242. 

The energy dissipation of a system containing free charges subjected to electric fields Is well known but this Indicates a non-equilibrium situation and as a result a thermodyanmlc description of the FDE Is Impossible. Within the framework of interionic attraction theory Onsager was able to derive the effect of an electric field on the Ionic dissociation from the transport properties of the Ions In the combined coulomb and external fields (2). It is not improper to mention here the notorious mathematical difficulty of Onsager s paper on the second Wien effect. 

Finally, we should still mention work by Makram-Ebeid and Lannoo (1982a,b) that calculates (in the adiabatic approach) the effect of an electric field in enhancing, with phonon assistance, the tunneling rate. Very good... 

Consequently, while the effect of an electric field dependence of both drift mobility and diffusion coefficient and also hydrodynamic repulsion decreases, the recombination probability, dielectric saturation and relaxation effects increase the recombination probability. 

The interpretation presented above appears reasonable so far, but it lacks clear-cut support because of the intricate mechanism of the cationic homopolymerization. Therefore, it is interesting to investigate the effect of an electric field on the monomer reactivity ratios in the copolymerizations, which depend on the rates of propagation only. 

Polarized light is obtained when a beam of natural (unpolarized) light passes through some types of anisotropic matter. In optical instruments this is usually a birefringent crystal which splits the incident unpolarized beam into two beams of perpendicular linear polarization, known as the ordinary and extraordinary beams. Anisotropy can also be created by the effect of an electric field, this being known as the Kerr effect. 

We wish only to remind readers that there are three main methods of electrochemical re-vealment conductivity, direct current (d.c.) amperometry, and integrated amperometry (pulsed amperometry is a form of integrated amperometry). In revealment by conductivity, the analytes, in ionic form, move under the effect of an electric field created inside the cell. The conductivity of the solution is proportional to the mobility of the ions in solution. Since the mobile phase is itself an electrolytical solution, in order to increase the signal/noise ratio and the response of the detector, it is very useful to have access to an ion suppressor before the revealment cell. By means of ionic exchange membranes, the suppressor replaces the counterions respectively with H+ or OH , allowing only an aqueous solution of the analytes under analysis to flow into the detector. 

FIGURE 22.1 The effect of an electric field on a, /3, and y radiation. The radioactive source in the shielded box emits radiation, which passes between two electrodes. Alpha radiation is deflected toward the negative electrode, (i radiation is strongly deflected toward the positive electrode, and y radiation is undeflected. 

The effect of an electric field on positrons annihilating in dense helium gas at low temperatures was investigated by Canter and coworkers (Ruttenberg, Tawel and Canter, 1985 Tawel and Canter, 1986). This work centred on the localization phenomena responsible for the clustering behaviour of helium atoms around the positron in dense helium gas, as illustrated in Figure 6.12. The aim of the studies was to test the hypothesis of Canter et al. (1980), supported by Azbel and Platzman... 

Electrostriction — The change of shape of an insulating material (dielectric) under the effect of an electric field. The deformation is proportional to the square of the polarization. 

The effect of an electrical field on the absorption/emission of spectra of a probe such as fluorescein or a coumarin derivative. It is derived from the interaction of the induced dipole(s) in the probe interacting with the charged group. See Sitkoff, D., Lockhart, D.J., Sharp, K.A., and Honig, B., Calculation of electrostatic effects at the amino terminal of an helix, Biophys. J. 67,2251-2260,1994 Pierce, D.W. and Boxer, S.A., Stark effect spectroscopy of tryptophan, B/opfiyx. J. 68,1583-1591,1995 Klymchenko, A.S., Avilov, S.V., and Demchenko, A.P., Resolution of Cys and Lys labeling of a-crystalUn with site-sensitive fluorescent 3-hydroxyflavone dye. Anal. Biochem. 329, 43-57, 2004. 

The effect of an electric field on hydrogen fluoride molecules, (a) When no electric field is present, the molecules are randomly oriented. (b) When the field is turned on, the molecules tend to line up with their negative ends toward the positive pole and their positive ends toward the negative pole. (This illustration exaggerates the effect. Actually, only a small fraction of the molecules are lined up with the field at a given instant.)... 

The effect of the strong external field is to accentuate this difference— using the method first developed for achiral molecules described earlier in this review—that of aligning the molecules in the molecular dynamics cube with an externally applied torque.This may be used to simulate the effect of an electric field on an assembly of dipolar molecules using second-order... 

Independently, a highly interesting problem recently revived is that of the alignment of molecules in liquid crystals due to externally applied static and alternating electric fidds. The problem was first approached by Jezewski and Kast, and was developed by Carr, Helfrich, Wysocki et al. and many others, studying various aspects, such as dielectric loss in electric fields and anomalous alignment in the smectic phase and domains, the effect of an electric field on the temperature of mesomorphic-isomorphic phase tranritions of liquid crystals, electric... 

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