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'Dielectric Relaxation' in keywords Facet   Publication Year 1998  [X]
Facet   section ZfN Section A:Volume 053  [X]
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1Author    S. Urban, B. Gestblom, R. Dąbrowski, H. KresseRequires cookie*
 Title    Dielectric Studies of a Substance with Negative Dielectric Anisotropy  
 Abstract    The results of dielectric studies of 6BAP(F) (l-[4-(hexylbicyclo[2,2,2]octyl]-2-(3-fluoro-4-methoxy-phenyl)ethane) in the nematic and isotropic phases are presented. The substance has a negative dielec-tric anisotropy. By applying two experimental techniques, using a network analyzer and time domain spectrometer (TDS), the two main relaxation processes, connected with the molecular reorientation around the short and long axes, respectively, were resolved in the phases studied. The activation bar-riers hindering the motions were obtained. By extrapolation of the longitudinal and transverse relaxa-tion times from the isotropic to the nematic phase the retardation factors, and g x , and the nematic po-tential versus temperature could be calculated. These are discussed together with the order parameter S obtained from the refractive index, and are compared with the predictions of the mean-field theories. 
  Reference    Z. Naturforsch. 53a, 134—140 (1998); received February 20 1998 
  Published    1998 
  Keywords    Liquid Crystals, Dielectric Anisotropy, Dielectric Relaxation, Retardation Factors 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0134.pdf 
 Identifier    ZNA-1998-53a-0134 
 Volume    53 
2Author    A. WiirflingerRequires cookie*
 Title    Nematic Potential and Order Parameter Determined from Dielectric Measurements  
 Abstract    The Maier-Saupe theory is employed in order to calculate order parameters S from the nematic po-tential q. It is found that one of the basic assumptions of the Maier-Saupe theory, q ~S, is approximate-ly fulfilled. The relation between q and S is analysed for various state changes. Previously reported find-ings for 7 PCH that q ~S, not fulfilled along isochoric changes, can be explained by taking into account the pressure and temperature dependences of q. The procedure described in this paper allows to treat experimental data for the nematic potential in a unique way, without being affected by inadequacies of experimentally determined order parameters. 
  Reference    Z. Naturforsch. 53a, 141—144 (1998); received February 11 1998 
  Published    1998 
  Keywords    Liquid Crystals, High Pressure, Nematic Potential, Dielectric Relaxation 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0141.pdf 
 Identifier    ZNA-1998-53a-0141 
 Volume    53