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1Author    R. Dąbrowski, J. Jadżyn, J. Dziaduszek, Z. Stolarz, G. Czechowski, M. KasprzykRequires cookie*
 Title    The Physical and Molecular Properties of New Low Melting Nematics with Negative Dielectric Anisotropy  
 Abstract    The paper presents some basic physical properties (static electric permittivities, refraction indices, density and viscosity) of 2-chloro-4-n'-alkylphenyl esters of 4-/r-alkylbicyclo[2,2,2] octane-1-carbox-ylic acids (n'=l, n = 5 and 7) which are, at room temperature, nematics with a negative dielectric an-isotropy. On the basis of temperature dependence of the principal static permittivities £ H (T) and e±(T) of the nematics, using the Maier-Meier equations, the angle between the dipole moment vector and the long axis of mesogenic molecules, the apparent molecular dipole moment square pl P[) {T), and the ne-matic order parameter S(T) were determined. 
  Reference    Z. Naturforsch. 54a, 448—452 (1999); received May 8 1999 
  Published    1999 
  Keywords    Nematics, Dielectric Anisotropy, Density, Viscosity 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0448.pdf 
 Identifier    ZNA-1999-54a-0448 
 Volume    54 
2Author    Jan Jadżyn, Grzegorz Czechowski, Danuta BaumanRequires cookie*
 Title    Static and Dynamic Dielectric Polarization and Viscosity of AZ-Hexylcyanobiphenyl in the Isotropic and Nematic Phases  
 Abstract    On the basis of the temperature dependence of the static principal permittivities, £y and e x , measured for the nematic phase of «-hexylcyanobiphenyl (C 6 H 13 -Ph-Ph-C=N, 6CB), a value of the angle ß between the long molecular axis and the direction of the dipole moment /iof 6CB, as well as the order parameter S{T), were obtained by use of the Maier-Meier equations. From the dielectric relaxation and viscosity data, the contribution of the nematic potential to the molecular dynamics was estimated. In the isotropic phase the dielectric and viscosity data allow one, in the framework of the Debye model, to estimate the effective length of 6CB molecule. 
  Reference    Z. Naturforsch. 55a, 810—816 (2000); received June 24 2000 
  Published    2000 
  Keywords    Electric Permittivity, Dielectric Relaxation, Viscosity, 6CB 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0810.pdf 
 Identifier    ZNA-2000-55a-0810 
 Volume    55 
3Author    Hans-Joachim BodeRequires cookie*
 Title    A Viscosity Model of Polyacrylamide Gel Electrophoresis  
 Abstract    In current theories o f polyacrylam ide gel electrophoresis, the idea prevails that molecular siev­ ing relies on different accessibility o f volum e fractions and o f cross-sectional area fractions (denot­ ed "pores") to different-sized ions due to the effect o f "geom etric exclusion". This correlates with the assum ption that all elements o f a polyacrylam ide network occupy fixed and unchangeable po­ sitions thus forcing colliding macro-ions to diffuse laterally in order to find an "accessible pore" and to resume m otion in direction o f the electrical field. H owever, the alternative conception would be equally well justified, i. e. the assum ption that polyacrylam ide chains represent smooth obstacles cleared aside under the electrokinetic pressure o f a macro-ion. This explanation would even be preferable with respect to the m olecular sieving effects occuring in solutions o f "liquid polyacrylam ide". Yet no theory exists as to describe such effects in quantitative terms. In the present article, a parameter is defined and discussed, w hich can be estim ated by experi­ ment, and which seems to be apt to characterize local resistivity o f polymer structures against dis­ location and deformation: the "fractional specific resistance" . D efinition o f this parameter is bas­ ed on the m odel o f a "viscosity-em ulsion" com posed o f two interpenetrating liquid compartments which are characterized by different levels o f hydrodynam ic friction and the spatial dimensions o f which are inferred from Ogston's theory. This concept o f "localized viscosity" m ay also serve as a link between theories o f molecular sieving and o f "m acroscopic viscosity" o f flexible polymers. The data o f Morris, formerly taken as verifications o f the "rigid-pore" concept, are now interpret­ ed in terms o f four factors responsible for sizediscrimination: collision frequency, duration o f sin­ gle contacts, size-dependent frictional force, and the extent o f cooperation am ong fibres, due to crosslinking and to simultanous contacts o f several fibres to a single macro-ion. Som e functions rel­ evant for problem s o f molecular weight determ ination by gel electrophoresis are discussed in rela­ tion to the suggested model. 
  Reference    Z. Naturforsch. 34c, 512—528 (1979); received March 22 1979 
  Published    1979 
  Keywords    Polyacrylamide, M olecular Sieve, Electrophoresis, Viscosity, Frictional Coefficient, Partition C oefficient 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0512.pdf 
 Identifier    ZNC-1979-34c-0512 
 Volume    34 
4Author    Yukihiro Yoshimura, Seiji Sawamura, Yoshihiro TaniguchiRequires cookie*
 Abstract    f fe c ts o f P r e s s u r e , T e m p e r a tu r e , a n d C o n c e n tr a tio n o n th e V is c o s ity o f A q u e o u s A m m o n iu m B ro m id e S o lu tio n Dedicated to Prof. Hitoshi Ohtaki on the occasion of his 60th birthday The viscosity of aqueous ammonium bromide solutions is measured at 0.1-1.0 mol kg-1, 278.2-323.2 K, and 0.1-375 MPa, using a high-pressure rolling-ball viscometer. The activation energy (£v) for viscous flow and Jones-Dole's B coefficient are estimated. Ev against pressure yields a concave curve with a minimum and B yields a convex one with a maximum. These phenomena are attributed to pressure, temperature, and concentration effects on the water-structure. 
  Reference    Z. Naturforsch. 50a, 316—322 (1995); received December 14 1994 
  Published    1995 
  Keywords    Viscosity, High pressure, Ammonium bromide, Activation energy, Jones-Dole's B coef­ ficient 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-0316.pdf 
 Identifier    ZNA-1995-50a-0316 
 Volume    50