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1990 (227)
1Author    G. Hübner, H. SchamelRequires cookie*
 Title    Magnetic Field Influence on Coulomb Relaxation of Anisotropic Electron-Ion-Plasmas  
 Abstract    The relaxation of velocity-space-anisotropies due to Coulomb collisions is studied within the class of bi-Maxwellian distributions in the presence of an external homogeneous magnetic field, both analytically and numerically. It is found that the anisotropy dependence of the energy exchange collision frequency well separates from its magnetic field dependence. In a certain region of magnetic field strength, the latter can be approximated by a substitution of the thermal electron's Larmor-radius for the Debye-length in the Coulomb-logarithm, as has been conjectured earlier. 
  Reference    Z. Naturforsch. 45a, 1—6 (1990); received November 14 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0001.pdf 
 Identifier    ZNA-1990-45a-0001 
 Volume    45 
2Author    Dieter BaalssRequires cookie*
 Title    The Viscosity Coefficients of Biaxial-Nematic Liquid Crystals. Phenomenology and Affine Transformation Model  
 Abstract    The viscosity tensor of biaxial-nematic liquid crystals contains 16 independent elements. A complete set of these viscosity coefficients is introduced and related to experimentally accessible quantities. Furthermore, the flow alignment and its stability against an arbitrary infinitesimal disturbance are discussed. By the affine transformation model, formerly established for the uniaxial symmetric case, one can express the viscous anisotropy of perfectly ordered biaxial ellipsoids in terms of the two viscosities of an isotropic reference system and the axes ratios of the nonspherical particles. 
  Reference    Z. Naturforsch. 45a, 7—13 (1990); received October 28 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0007.pdf 
 Identifier    ZNA-1990-45a-0007 
 Volume    45 
3Author    C. G. KoutroulosRequires cookie*
 Title    Relativistic Energy States of the A-Particle in Hypernuclei Using Gaussian Potentials  
 Abstract    The Dirac equation with scalar potential and fourth component of vector potential of the Gaussian form is solved numerically for potential parameters obtained by a least squares fitting of the ground state binding energies of the A in a number of hypernuclei. The binding energies in the ground and excited states for various hypernuclei are determined. The spacings between the various levels are also given. 
  Reference    Z. Naturforsch. 45a, 14—16 (1990); received October 9 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0014.pdf 
 Identifier    ZNA-1990-45a-0014 
 Volume    45 
4Author    Reinhard HoneggerRequires cookie*
 Title    Decomposition of Positive Sesquilinear Forms and the Central Decomposition of Gauge-Invariant Quasi-Free States on the Weyl-Algebra  
 Abstract    A decomposition theory for positive sesquilinear forms densely defined in Hilbert spaces is developed. On decomposing such a form into its closable and singular part and using Bochner's theorem it is possible to derive the central decomposition of the associated gauge-invariant quasi-free state on the boson C*-Weyl algebra. The appearance of a classical field part of the boson system is studied in detail in the GNS-representation and shown to correspond to the so-called singular subspace of a natural enlargement of the one-boson testfunction space. In the example of Bose-Ein-stein condensation a non-trivial central decomposition (or equivalently a non-trivial classical field part) is directly related to the occurrence of the condensation phenomenon. Key words: Closable and singular positive sesquilinear forms; gauge-invariant quasi-free states on the Weyl algebra; central decomposition; classical part of boson fields; condensation phenomena. 
  Reference    Z. Naturforsch. 45a, 17—28 (1990); received June 10 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0017.pdf 
 Identifier    ZNA-1990-45a-0017 
 Volume    45 
5Author    S.Sreehari Sastry, V. Venkata, Rao, P. Narayana Murty, G. Satyanandam, T. F. Sundar, RajRequires cookie*
 Title    Molecular Ordering in Nematic MBCA and EPAPU  
 Abstract    By EPR, two nematic liquid crystals (MBCA and EPAPU) were investigated using a steroidal nitroxide spin probe. In both liquid crystals the isotropic-nematic phase transition is of first order. The observed variation of the order parameter with temperature is compared with predictions from the Maier-Saupe and Humphries-James-Luckhurst models and with results obtained by several other experimental techniques. 
  Reference    Z. Naturforsch. 45a, 29—32 (1990); received October 12 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0029.pdf 
 Identifier    ZNA-1990-45a-0029 
 Volume    45 
6Author    J. Wąsicki, Z. Pająk, A. KozakRequires cookie*
 Title    Cation and Anion Reorientation at Phase Transition in Pyridinium Tetrafluoroborate  
 Abstract    Temperature dependences of and 19 F second moment and spin-lattice relaxation times for polycrystalline pyridinium tetrafluoroborate were measured. A phase transition was discovered at 202 K. A model of cation reorientation between inequivalent (low-temperature phase) and equiva-lent (high-temperature phase) equilibrium positions is proposed. Whether the anion reorients isotropically or about a symmetry axis cannot be decided. An analysis of cross-relaxation effects yielded activation parameters for cation and anion reorientation. The rotational correlation times for both ions converge just at the phase transition reaching the value of 10~ 10 s. 
  Reference    Z. Naturforsch. 45a, 33—36 (1990); received August 5 1989 
  Published    1990 
  Keywords    NMR, cross-relaxation, molecular motions, phase transitions 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0033.pdf 
 Identifier    ZNA-1990-45a-0033 
 Volume    45 
7Author    A. Scharkowski, H. Schmiedel, R. Stannarius, E. WeißhuhnRequires cookie*
 Title    Elastic Constants of Nematic Phenylpyrimidines Determined by Two Different Methods  
 Abstract    A survey of various methods to measure the elastic constants K, of nematic liquid crystals is given. To determine K 3 and the anisotropy of the diamagnetic susceptibility Ax of two members of the 5n-hexyl-2-[4n-alkyloxy-phenyl]-pyrimidines and a mixture of both, we used a combined electro-magneto-optical method, consisting in independent measurements of the optical phase difference in electric and magnetic fields acting on the same cell. The temperature dependence of the K r and K 3 -values for these phenylpyrimidines can be explained by common theories. The Ax data show the same temperature dependence as the values of the orientational order parameter S obtained by 'H-NMR. 
  Reference    Z. Naturforsch. 45a, 37—42 (1990); received June 23 1989 
  Published    1990 
  Keywords    Nematic liquid crystals, elastic constants, diamagnetic susceptibility, electro-optic, magneto-optic 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0037.pdf 
 Identifier    ZNA-1990-45a-0037 
 Volume    45 
8Author    D. J. Isbister, D. H. ChaplinRequires cookie*
 Title    The Influence of the Skin Effect on the Amplitude of Single Pulse Gamma Detected NMR on Oriented Nuclei Signals  
 Abstract    The effects of skin depth on gamma detected single pulse Nuclear Magnetic Resonance on Oriented Nuclei (NMRON) signals are theoretically explored for narrow, intermediate and broad line metallic samples, using the density matrix approach describing a pure Zeeman system. It is shown that the skin effect distortion of the signal can dominate over intermediate to broadline distortions for that range of experimental conditions generally applicable to ferromagnetic hosts. In particular, the skin effect distortions of the first maximum, obtained when the excitation pulse width is lengthened, are significant and can determine the accuracy of calibration of the radiofrequency "(rf)" field amplitude at the resonating nuclei when assigning an average turn angle to this maximum. 
  Reference    Z. Naturforsch. 45a, 43—49 (1990); received July 7 1989 
  Published    1990 
  Keywords    NMRON, Zeeman interactions, Skin effect, Density matrix 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0043.pdf 
 Identifier    ZNA-1990-45a-0043 
 Volume    45 
9Author    E. Matsubara, Y. Waseda, A. P. Tsai, A. Inoue, T. MasumotoRequires cookie*
 Title    Anomalous X-ray Scattering Study of the Quasi-crystalline Al 6 5Cu 20 Fe 15 Alloy  
 Abstract    The environmental radial distribution functions (RDFs) around Cu and Fe as well as the ordinary RDF of an as-quenched Al 65 Cu 20 Fe 15 alloy have been determined by anomalous x-ray scattering (AXS) and conventional x-ray diffraction techniques. The experimental information indicates that a strong directional dependence along the symmetrical axes exists for the Cu atoms but not for the Fe atoms. Almost identical RDFs were also obtained in both the as-quenched and fully-annealed states of the Al 65 Cu 20 Fei 5 alloy. Thus, the small differences observed between diffraction profiles of the as-quenched and annealed samples of this alloy may be attributed to defects or strains introduced during the rapid quenching process. 
  Reference    Z. Naturforsch. 45a, 50—54 (1990); received October 10 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0050.pdf 
 Identifier    ZNA-1990-45a-0050 
 Volume    45 
10Author    MarcoL H Gruwel, RoderickE. WasylishenRequires cookie*
 Title    A Deuterium NMR Study of some Ammonium Tetraphenylborates  
 Abstract    Deuterium nmr has been used to study the rotational dynamics of the ammonium ion in ammo-nium tetraphenylborate and of the cation in a series of methylammonium tetraphenylborates. The results of variable temperature 2 H relaxation measurements (T 1Z and T 1Q) on the parent compound, ND 4 B(C 6 H 5) 4 , lead to a low activation energy for reorientation of the ND 4 ion, 5.0 ± 0.5 kJ mol -1 , indicative of weak cation-anion interactions. Related studies of the tetramethyl-d 12 ammonium salt indicate rapid jumps of the whole cation (T <|10 -5 S) over the complete temperature range investi-gated, 137 to 385 K, with an activation energy of 14.1 + 0.5 kJ mol" 1 . Deuterium nmr lineshape studies of the methylammonium salt indicate rapid reorientation of the CD 3 and ND 3 groups about their C 3 axes; however, the motion of the C-N axis is restricted to large amplitude librations. Similar studies of the dimethylammonium salt indicate methyl group jumps at 245 K; at temperatures above 320 K the cation also undergoes two-site jumps about the C 2 axis. In the case of the trimethylam-monium salt, the nmr lineshapes indicate methyl group jumps superimposed on C 3 rotations of the complete cation about the N-H bond axis over the temperature interval 185-348 K. In all the tetraphenylborate salts studied, the 2 H nmr lineshapes indicate substantial librational motion of the cation at room temperature. 
  Reference    Z. Naturforsch. 45a, 55—66 (1990); received August 31 1989 
  Published    1990 
  Keywords    2 H nmr, rotation, ammonium derivatives, tetraphenylborates 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0055.pdf 
 Identifier    ZNA-1990-45a-0055 
 Volume    45 
11Author    K. Kynev, N. Maneva, S. AngelovRequires cookie*
 Title    Luminescent Centres of T D Symmetry in "Cold" Activated ZnS-Mn  
 Abstract    By coprecipitation of ZnS and MnS in excess of Na 2 S, luminescent centres are built differing considerably from those in zinc salt excess. ESR data give evidence of centres of T d symmetry. 
  Reference    Z. Naturforsch. 45a, 67—68 (1990); received October 9 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0067_n.pdf 
 Identifier    ZNA-1990-45a-0067_n 
 Volume    45 
12Author    J. Brunvoll, S. J. CyvinRequires cookie*
 Title    What do We Know about the Numbers of Benzenoid Isomers?  
 Abstract    The numbers of benzenoid chemical isomers, represented by the formulas C"H S , are reviewed. The data which have been deduced from the available literature are supplemented. 
  Reference    Z. Naturforsch. 45a, 69—79 (1990); received September 6 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0069.pdf 
 Identifier    ZNA-1990-45a-0069 
 Volume    45 
13Author    Julian Ławrynowicz, Katarzyna Kędzia, Leszek WojtczakRequires cookie*
 Title    Fields Connected with Particles in Terms of Complex-Riemannian Geometry  
 Abstract    A complex analytical method of solving the generalised Dirac-Maxwell system has recently been proposed by two of us for a certain class of complex Riemannian metrics. The Dirac equation without the field potential in such a metric appeared to be equivalent to the Dirac-Maxwell system including the field potentials produced by the currents of a particle in question. The method proposed is connected with applying the Fourier transform with respect to the electric charge treated as a variable, with the consideration of the mass as an eigenvalue, and with solving suitable convolution equations. In the present research an explicit calculation based on linearization of the spinor connections is given. The conditions for the motion are interpreted as a starting point to seek selection rules for curved space-times corresponding to actually existing particles. Then the same method is applied to solids. Namely, by a suitable transformation of the configuration space in terms of elements of the interaction matrix corresponding to the Coulomb, exchange, and dipole integrals, the interaction term in the hamiltonian becomes zero, thus leading to experimentally verificable formulae for the autocorrelation time. 
  Reference    Z. Naturforsch. 45a, 81—94 (1990); received November 2 1988 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0081.pdf 
 Identifier    ZNA-1990-45a-0081 
 Volume    45 
14Author    Bimal Kumar, Rajkumar RoychoudhuryRequires cookie*
 Title    Quark-Gluon Plasma with Finite Quark Mass  
 Abstract    We have derived exact analytical formulas of various thermodynamic quantities such as Energy, Pressure, Entropy etc., at finite temperature without neglecting quark mass. The critical curve in the H-T plane has been calculated to show the effect of finite quark mass. The energy density has also been calculated for different values of the quark mass. 
  Reference    Z. Naturforsch. 45a, 95—101 (1990); received January 27 1989* 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0095.pdf 
 Identifier    ZNA-1990-45a-0095 
 Volume    45 
15Author    K. Ganesan, R. Damle, J. RamakrishnaRequires cookie*
 Title    Proton NMR Study of Molecular Dynamics in Hydrazinium Perchlorate  
 Abstract    The proton spin-lattice relaxation time T l (at 5.4, 10 and 15 MHz) and second moment M 2 (at 9.8 MHz) have been measured in hydrazinium Perchlorate (N 2 H 5 C10 4). The temperature depen-dence of T, shows two minima. The low temperature T, minimum has been explained in terms of NH 3 reorientation about the N N axis while the high temperature minimum is attributed to the exchange of protons within the NH 2 group (180° flip about the H-N-H bisectrix). The activation energies for NH 3 and NH : motions are found to be 20.5 kJ mol" 1 and 39.8 kJ mol" 1 , respectively. The second moment variation u ith temperature shows two transitions around 120 K and 210 K and has been discussed in terms of NH 3 /NH 2 motions. 
  Reference    Z. Naturforsch. 45a, 102—106 (1990); received October 17 1989 
  Published    1990 
  Keywords    NMR study, Molecular dynamics, Hydrazinium Perchlorate 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0102.pdf 
 Identifier    ZNA-1990-45a-0102 
 Volume    45 
16Author    E. L. Saw, C. T. YapRequires cookie*
 Title    Vanishing Fermi to Gamow-Teller Mixing Ratio of the ß + Decay of 58 Co  
 Abstract    Since 1956, fourteen experimentally-deduced values of the Fermi to Gamow-Teller mixing ratio y = C v M F /C A M GT were published, varying from 0.05 to —0.36 with most values consistent with y = 0, particularly those from recent measurements. Our calculation, using the Nilsson model, yields >> = 2.07 x 10 ~ 4 , which can be taken as zero. Our result is therefore consistent with time-reversal invariance. Furthermore, the vanishing value of y arises both from the AT selection rule and the AK selection rule. 
  Reference    Z. Naturforsch. 45a, 107—109 (1990); received November 6 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0107.pdf 
 Identifier    ZNA-1990-45a-0107 
 Volume    45 
17Author    P. Wolf, H. MäderRequires cookie*
 Title    The Pressure Dependence of 7 2 "^ e ' axat i° n R ates for Rotational Transitions of Sulfur Dioxide in Mixtures with Oxygen and Nitrogen  
 Abstract    The transient emission technique in the time domain has been used to determine the pressure dependence of the coherent dephasing time T 2 of sulfur dioxide in mixtures with 0 2 and N 2 for several rotational transitions in the vibrational ground state. From these data line broadening parameters Av/p and collisional cross-sections are calculated. 
  Reference    Z. Naturforsch. 45a, 110—112 (1990); received November 18 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0110.pdf 
 Identifier    ZNA-1990-45a-0110 
 Volume    45 
18Author    G. Gassier, W. HüttnerRequires cookie*
 Title    The gauche-trans Energy Difference of n-Butane from a Doppler Limited Investigation of the 740 cm -1 CH 2 -Rocking Region  
 Abstract    Tunable diode laser spectra of n-butane gas were recorded in the 740 cm -1 CH 2 -rocking region using path lengths of typically 300 m, pressures below 1 mbar and temperatures between 170 and 300 K. The spectra are complicated by the overlap of the two trans and gauche rotameric fundamen-tals, and by a strong absorption background probably caused by the addition of hot-band transi-tions involving excitation of one or more quanta of the torsion vibrations around the central C-C bond. Analysis was aided by Fourier transform recordings in medium and high resolution and lead to the assignment of rovibrational features close to the band centers at v 0 (trans) = (733.5797 ±0.0015) cm -1 and v 0 (gauche) = (747.5116 ± 0.0018) cm" 1 of the trans and gauche rotamers, re-spectively, and to medium accurate spectroscopic parameters. A statistical evaluation of the temper-ature dependence of the relative absorption intensities of near-by trans and gauche transitions resulted in the trans-gauche rotameric energy difference of AH = (246 ± 18) cm -1 or (2.94 + 0.21) kJ mol -1 . This value is lower than those from previous determinations but still indicates an inter-esting decrease of the gauche-trans energy difference in going from gas to the liquid state. 
  Reference    Z. Naturforsch. 45a, 113—125 (1990); received June 20 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0113.pdf 
 Identifier    ZNA-1990-45a-0113 
 Volume    45 
19Author    E. DachwitzRequires cookie*
 Title    Studies of Polymer Solvation by Dielectric Relaxation Spectroscopy III: Polyvinyl Pyrrolidone in N-Methyl-2-Pyrrolidone, Ethanediol, Methanol, and Water  
 Abstract    The permittivity of the title solutions has been measured at frequencies between some MHz and 72 GHz at 20 °C. Polyvinyl pyrrolidone of relative molar mass ranging from 1200 to 360 000 has been used. Referring to the concentration of monomeric repeat units (x = 0.65 maximum) there is no significant chain length effect. The permittivity data are described in terms of discrete Debye type spectral components. Special attention is paid to the contributions ascribable to the solvents, which are discussed with respect to their solvation behaviour. This can be described by a three state solvent model as follows. Besides the "bulk" solvent a further contribution is found in any case which is due to loosely affected (slowed down) solvent. Moreover a part of the solvent appears to be tightly bound to the polymer at high concentrations. All the solvents considered show similar solvation properties, notwithstanding their different tendencies towards selfassociation. 
  Reference    Z. Naturforsch. 45a, 126—134 (1990); received November 2 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0126.pdf 
 Identifier    ZNA-1990-45a-0126 
 Volume    45 
20Author    Szilvia Murányi, Horst-Dieter FörsterlingRequires cookie*
 Title    Chloride Induced Oscillations in the Classical Belousov-Zhabotinsky Reaction Explained by the "Radicalator"-Model  
 Abstract    We detected non-bromide controlled oscillations, which appear in a classical Belousov-Zhabotin-sky (BZ) system at a high malonic acid/bromate ratio in the presence of added chloride. The oscillations start immediately after the addition of the catalyst. To explain the oscillations we assume control by a synergetic process involving both chloride ions and malonyl radicals. The experiments are well in accordance with calculations based on the "Radicalator" model. This model is also capable of explaining the rate of formation of C0 2 in the BZ system. 
  Reference    Z. Naturforsch. 45a, 135—144 (1990); received October 24 1989 
  Published    1990 
  Keywords    Belousov-Zhabotinsky reaction, Bromous acid, Chloride, Autocatalysis 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0135.pdf 
 Identifier    ZNA-1990-45a-0135 
 Volume    45 
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