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Abstract
For nematic phases of pentacyanobiphenyl (5CB) and 4-n-methoxybenzoate-4-n-pentylphenyl (MBPP) the viscosity coefficients have been determined by means of a flat capillary viscometer. The detailed information on the experimental set-up has been published elsewhere. The measurements enable the calculation of all Leslie coefficients αi i = 1 - 6. Having the Leslie coefficients determined, the twist viscosity coefficient [mgrave]1 can be calculated. The comparison of the calculated and experimentally determined twist viscosity coefficient may serve as a test of validity of the Parodi relaxation: α2 + α3 = α6 - α5. The validity of this relation was additionally proved by means of comparison of the results of the viscometric measurements and the results of measurements of the attenuation of longitudinal ultrasound waves.