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Zusammenfassung:
Using quartz crystal resonators, we have measured the effective viscosities of nematic liquid crystals (LCs) in the MHz domain. The LC orientation was switched via the command-surface effect. The dependence of viscosity on orientation cannot be explained by orientational modes. They are attributed to the emission of longitudinal sound, the latter effect requiring a tilt orientation of the nematic director with respect to the surface. Optical investigations confirm the existence of a finite pretilt angle. Sensor applications are discussed. (C) 2002 American Institute of Physics.
