Viscoelastic coefficients

Fig. 5 Dependencies of viscoelastic coefficients Ki, K2 and rj on total dose of irradiation.

Waugh, R. E., and Agre, P. (1988). Reductions of erythrocyte membrane viscoelastic coefficients reflect spectrin deficiencies in hereditary spherocytosis. J. Clin. Invest. 81, 133-141. 

R448 L. A. Marky and D. W. Kupke, Enthalpy - Entropy Compensations in Nucleic Acids Contribution of Electrostriction and Structm-al Hydration , Methods Enzymol, 2000,323,419 R449 A. F. Martins, Measurement of Viscoelastic Coefficients for Nematic Mesophases Using Magnetic Resonance , EMIS Datarev. Ser., 2000, 25,405... 

TABLE 603 Temperature Dependence of Viscoelastic Coefficients of the Red Cell Membrane... 

Where o = stress of visco-piston, j = strain of visco-piston and t] = viscoelastic coefficient. 

Standard applications of DLS experiments in bulk samples include measurements of viscoelastic coefficients and dispersion relations of orientational fluctuation modes. As the experimental details are given further in the text, let us first discuss the nature of orientational fluctuation modes in nematics. 

In general, in comparison with low molecular weight nematics, polymeric nematics show higher elastic constants. Solutions of low molecular weight fractions of polymers in monomeric nematic liquid crystals are of practical interest, because viscoelastic coefficients can be tailored in this way. Investigations of the viscoelastic characteristics have been reported, e.g. for side-chain [99] and main-chain polymers [100-102, 160]. In the side-chain mixtures, A, has been found to remain constant in mixtures containing up to 20% of added polymer. For main-chain additives, the bend and splay constants both increase moderately with polymer concentration (measurements up to 5% [102]). The twist constant seems to be uninfluenced [160]. 

A.F. Martins [ Datareview in this book 8.3 Measurement of viscoelastic coefficients for nematic mesophases using magnetic resonance ]... 

Measurement of viscoelastic coefficients for nematic mesophases using magnetic resonance... 

Dynamic fight scattering has often been used in bulk liquid crystals for several different purposes. In most cases, the ratios of the viscoelastic coefficients were determined, according to the dispersion relation (4.8). In principle, from the amplitude of the non-normalised autocorrelation function one can also obtain the elastic constants themselves by using (4.7), but as it is difficult to measure absolute intensities in fight scattering, Frank elastic constants are usually obtained using other methods. 

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