A parameter used to characterize ER fluids is the Mason number, which describes the ratio of viscous to electrical forces, and is given by equation 14, where 8 is the solvent dielectric constant T 0, th solvent viscosity 7, the strain or shear rate P, the effective polarizability of the particles and E, the electric field (117). [Pg.175]

The polarity of the solvent exerts an appreciable effect on some of the hfc constants for pyridinyl radicals The effects have been correlated with the solvent polarity parameters, Z-value and Er(30)-value and a theory relating the shifts to the permittivity of the solvent has been published [Pg.140]

Langhals has described a remarkable relationship of most of the empirical solvent parameters (Z, Er (30), Y, etc.] to composition in binaiy solvent mixtures [Pg.477]

For each family of silica-aluminas several synthesis parameters can be identified and applied to control the textural properties of final products. For example the role of the type and the amount of gelling agent (8,9), the solvent role (10), the silica/alumina molar ratio (9) have been discussed for MSA and ERS-8 formation. [Pg.625]

For molecular systems in the vacuum, exact analytical derivatives of the total energy with respect to the nuclear coordinates are available [22] and lead to very efficient local optimization methods [23], The situation is more involved for solvated systems modelled within the implicit solvent framework. The total energy indeed contains reaction field contributions of the form ER(p,p ), which are not calculated analytically, but are replaced by numerical approximations Efp(p,p ), as described in Section 1.2.5. We assume from now on that both the interface Y and the charge distributions p and p depend on n real parameters (A, , A ). In the geometry optimization problem, the A, are the cartesian coordinates of the nuclei. There are several nonequivalent ways to construct approximations of the derivatives of the reaction field energy with respect to the parameters (A1 , A ) [Pg.43]

The selective resolution enhancement in derivative spectroscopy is pushed even further in the fourth derivative mode. As in the case of second derivative spectroscopy, the amplitude and the position of the derivative spectral bands of the aromatic amino acids are related to the polarity of the medium. We have undertaken a systematic investigation of these spectral features of the N-acetyl O-ethyl esters of tyrosine and tryptophan in various solvents of different polarity (from cyclohexane to water). Astonishingly, a simple relationship between the spectral parameters of the fourth derivatives and the dielectric constant was found [11]. As shown in Figure 5, for tyrosine it is the position of >.max, and for tryptophan it is the derivative amplitude which depends linearly on the dielectric constant er. Since in addition the fourth derivative spectra of these model compounds do not depend significantly on pressure (at least up to 500 MPa), these spectral features may be used as an intrinsic probe to sense the dielectric constant in the vicinity of tyrosine and tryptophan. [Pg.557]

See also in sourсe #XX -- [ Pg.391 ]

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