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1980 (1)
1976 (1)
1Author    H.-D Amberger, R. D. Fischer, B. KanellakopulosRequires cookie*
 Title    of Uranium(rV) -tetracyclopentadienide  
 Abstract    Some significant features of the low-energy part of the crystal field (=CF) splitting pattern of the organometallic 5f 2 -system (^ 5 -C5Hs)4U(IV) can be deduced from the tem-perature dependence of the magnetic susceptibility which has been measured on poly-crystalline samples between 1.1 and 298 K. The results of model calculations performed independently on the basis of three different semi-empirical approaches are compatible with the deductions from the experiments and allow estimates of the sign and order of magnitude of quantities like the CF-splitting parameters B4 0 and Bö 0 viz. the (averaged) angular overlap parameters ea and e" and of the valence state ionisation potential of the 5f-electrons. Anticipating a rather weakly perturbed tetrahedral CF, the observed magnetic properties may be satisfactorily simulated if the six lowest-lying first-order CF-states and one common scaling factor are accounted for. 
  Reference    (Z. Naturforsch. 31b, 12—21 [1976]; received July 17 1975) 
  Published    1976 
  Keywords    Uranium-tetracyclopentadienide, Susceptibility, Model Calculations, Crystal Field Splitting Pattern, Electronic Structure 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-0012.pdf 
 Identifier    ZNB-1976-31b-0012 
 Volume    31 
2Author    U. Kreibig, C. W. EtterRequires cookie*
 Title    Light Diffraction of in vitro Crystals of Six Tobacco Mosaic Viruses  
 Abstract    Iridescent gels o f the common, tomato mosaic, para-tobacco mosaic, ribgrass mosaic, sunnhemp mosaic, and cucumber 4 tobacco mosaic virus strains were prepared using the purification method of Boedtker and Simmons (J. Amer. Chem. Soc. 1958). Macrocrystals which were stable for many months could be grown from iridescent gels of all viruses when stored at 0 -1 0 °C. The gels exhibited various structural phases (nematic and smectic) differing in density. The structure of the microcrystalline gels and of macrocrystals was investigated by means of optical diffraction. Distinct Bragg reflections were observed from which a mean periodicity of 340 nm was derived for all virus strains. The results indicate a crystalline multilayer structure as first proposed by Oster (J. Gen. Physiol. 33, 445, [1950]). The angular positions and widths of the Bragg reflections depended on the concentration of virus and the ionic strength. The periodicity decreased from 365 nm at 30 mg/ml virus to about 315 nm at 109 mg/ml virus, i.e. the periodicity approached the 300 nm length o f the virion. Model calculations taking into account Debye-Hückel repulsive and van der Waals attractive forces gave a qualitative explanation for the crystalline structure and its observed concentration dependence. The in vitro crystals resemble immature crystal forms observed in the living cell. 
  Reference    Z. Naturforsch. 35c, 750—762 (1980); received March 7 1980 
  Published    1980 
  Keywords    Tobacco Mosaic Viruses, Crystallization, Phase Transitions, Light Diffraction, Crystal Structure, Model Calculations 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0750.pdf 
 Identifier    ZNC-1980-35c-0750 
 Volume    35