Effective electric field strength

The study of the electric field strength effect on the shape of the density gradient formed in the TLF cell indicated an important difference compared with the first approximation theoretical model. A series of experimental data and the theoretically calculated curves are shown in Figure 6. The difference can be caused by the interactions between the colloidal particles of the binary density forming carrier liquid. Moreover, the electric field strength across the cell or channel thickness was estimated from the electric potential measured between the electrodes, but the electrochemical processes at both electrodes can contribute to this difference. 

The dielectric constant (permittivity) tabulated is the relative dielectric constant, which is the ratio of the actual electric displacement to the electric field strength when an external field is applied to the substance, which is the ratio of the actual dielectric constant to the dielectric constant of a vacuum. The table gives the static dielectric constant e, measured in static fields or at relatively low frequencies where no relaxation effects occur. 

The heating effect is the limiting factor for all electrophoretic separations. When heat is dissipated rapidly, as in capillary electrophoresis, rapid, high resolution separations are possible. For electrophoretic separations the higher the separating driving force, ie, the electric field strength, the better the resolution. This means that if a way to separate faster can be found, it should also be a more effective separation. This is the opposite of most other separation techniques. 

FIG. 22-29 Qualitative effects of Reynolds number and applied-electric-field strength on the filtration permeate flux J. Dashed lines indicate large particles (radial migration dominates) solid lines, small particles (particle diffusion dominates). 

Thus the IR active modes will be determined by the matrix elements of the polarlsablllty matrix and not by a combination of the surface selection rule and the normal IR selection rules l.e. all of the Raman active modes could become accessible. This effect has been formalized and Its significance assessed In a discussion (12) which compares Its magnitude for a number of different molecules. In the case of acrylonitrile adsorption discussed In the previous section, the Intensity of the C=N stretch band appears to vary with the square of the electric field strength as expected for the Stark effect mechanism. 

The principal axis of the cone represents the component of the dipole under the influence of the thermal agitation. The component of the dipole in the cone results from the field that oscillates in its polarization plane. In this way, in the absence of Brownian motion the dipole follows a conical orbit. In fact the direction of the cone changes continuously (because of the Brownian movement) faster than the oscillation of the electric field this leads to chaotic motion. Hence the structuring effect of electric field is always negligible, because of the value of the electric field strength, and even more so for lossy media. 

Hence, if thermodynamic effects of electric effect occur, the electric field strengths necessary are too high compared with ordinary operating conditions of microwave heating. 

The migration in CE is obviously influenced by both the effective and the electroosmotic mobility. Therefore, the proportionality factor in the relationship of the migration velocity and the electric field strength in such a case is called the apparent electrophoretic mobility (/iapp) and the migration velocity the apparent migration velocity (vapp). The /iapp is equal to the sum of /migration velocity is expressed as... 

Fig. 17.7. The effect of electric field perturbations, due to differences in conductivity between the sample- and the buffer electrolyte zone on the shape of the peaks, (a) conductivity distribution, (b) sample ions distribution, (c) electric field strength perturbations, and (d) effect on the peak shapes.

Fig. 26. Effect buffer concentration in the mobile phase on EOF velocity (1) and current (2). (Reprinted with permission from [ 110]. Copyright 2000 Elsevier). Conditions monolithic capillary column 75 pm i.d., total length 30 cm, active length 25 cm, containing sol-gel bonded 3 pm ODS/SCX with 80 A pores, mobile phase 70 30 acetonitrile/phosphate buffer pH 3.0, electric field strength 442 V/cm (voltage 15 kV)...

Other models are based on electric breakdown of the oxide [Fo2, Chl2]. It is not clear whether this breakdown should be thought of in terms of an electronic or an ionic effect. However, in both cases breakdown may cause a degradation in the oxide morphology, which leads to an enhanced etch rate. An electric field strength in the order of 10 MV cm4, the observation of an electroluminescent burst associated with the current peak of the oscillation, and the presence of an electronic component in the interface current are in favor of this model [CalO, Chl2]. 

In practice, electric fields sufficient to effect field ionization are only obtained in close proximity to sharp tips, edges, or thin wires. The smaller the radius of the curvature of the anode, the further away (1-10 nm) the field suffices to cause ionization. The importance of sufficient electric field strength is reflected by the half-... 

The tendency for a system at equilibrium to adjust in a manner that minimizes the effect of a change imposed by external factors (such as changes in temperature, pressure or electric field strength). 

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