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1994[X]
81Author    S. U. Rban, T. Briickert, A. W. ÜrflingerRequires cookie*
 Title    Dielectric Studies on Liquid Crystals under High Pressure: VI. Low Frequency Relaxation Process in the Nematic and Smectic A Phase of 4-n-Octyl-4'-Cyanobiphenyl (8 CB)  
 Abstract    Dielectric relaxation studies of 4-n-octyl-4'-cyanobiphenyl (8 CB) were performed in the pressure range 0 .1 -1 2 0 M Pa, the frequency range 1 k H z -1 3 M Hz and the temperature range 2 9 5-331 K. The dielectric behaviour of 8C B in the nematic phase is similar to that of 5CB, 6C B and 7CB. In particular, the activation enthalpy decreases with increasing pressure and the activation volume decreases with increasing temperature in the nematic phase. In the smectic A phase of 8CB both these parameters are markedly lower and show opposite pressure and temperature dependencies. We tentatively interpret these effects as a result of breaking of the dipole-dipole correlations which manifests itself differently in these liquid crystalline phases. 
  Reference    Z. Naturforsch. 49a, 552 (1994); received March 5 1994 
  Published    1994 
  Keywords    Dielectric relaxation, High pressure, Liquid crystals, Activation quantities 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0552.pdf 
 Identifier    ZNA-1994-49a-0552 
 Volume    49 
82Author    N.V S Rao, G. Padm, Rani, D. M. Potukuchi, V.G K M PisipatiRequires cookie*
 Title    Dilatometric Study of the Isotropic-Smectic F Transition of 100.14  
 Abstract    The com pound N(p-n-decyloxy benzylidene)p-n-tetradecyl aniline, (100.14), a higher hom ologue of the M BBA series, exhibits smectic F and smectic G phases. Dilatom etric studies inferred strong pre-transitional effects in a large temperature range. D SC results confirmed the first order nature of the IF and FG transitions. The exponential growth of continuous six fold hexagonal order across the isotropic-smectic F phase transition is estim ated from the density studies with an exponent b = 0.75. 
  Reference    Z. Naturforsch. 49a, 559 (1994); received July 26 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0559.pdf 
 Identifier    ZNA-1994-49a-0559 
 Volume    49 
83Author    W. Alexander, VanH. OokRequires cookie*
 Title    Comments on H /D Isotope Effects on Polarizabilities of Small Molecules. Correlation with Virial Coefficient, Molar Volume, and Electronic Second Moment Isotope Effects  
 Abstract    Literature data on H /D isotope effects on polarizability are reviewed. An argument based on perturbation theory correlates the isotopic differences with electronic transition mom ents via vibra­ tional averaging. The contribution of the second moment isotope effect is especially important. The approach is first illustrated with a calculation on H 2/ D 2 and then em ployed to correlate differential refractive index data on about twenty other H /D isotopic pairs. A table o f bond polarizability isotope effects is presented which permits the estimation o f polarizability isotope effects for various kinds of H /D substituted compounds. Coupling these results with known isotope effects on vibra­ tional amplitude permits calculation of vapor phase virial coefficient isotope effects, while com bina­ tion with refractive index data on liquids yields reasonable values for the sum o f the isotope effects on m olar volume and electronic second moment. However the quantitative correlation of the polarizability isotope effect with isotope effects on vapor pressure or thermodynam ic activity is less direct. Key words: Polarizability, isotope effects, refractive index, electronic second m om ent isotope effects, bond polarizabilities, molar volume isotope effects. 
  Reference    Z. Naturforsch. 49a, 563—5 (1994); received January 3 1994 
  Published    1994 
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 Identifier    ZNA-1994-49a-0563 
 Volume    49 
84Author    Michael Kom, JörnK. Üster, Herbert DreeskampRequires cookie*
 Title    Einfluß des Silberkations auf das Fluoreszenzverhalten polyzyklischer aromatischer Kohlenwasserstoffe  
 Abstract    Com bining the results o f fluorescence and triplet-triplet absorption measurements, the influence o f silver perchlorate on the excited states o f pyrene, phenanthrene, 9-cyanophenanthrene, 9,10-diphenylanthracene and 9,10-dicyanoanthracene in fluid solutions has been investigated. In corre­ spondence with a small energy gap between the lowest excited singlet state and the nearest lower triplet state an external heavy atom effect has been found to be responsible for the fluorescence quenching in the case o f pyrene, phenanthrene and 9-cyanophenanthrene. In the case o f 9,10-diphenylanthracene and 9,10-dicyanoanthracene, where this energy gap is large, an exciplex emission is observed with no significant increase o f triplet state formation. Furthermore, 9-cyanophenanthrene and 9,10-dicyanoanthracene under similar experimental conditions form ground state complexes with A gC 104 with a red-shifted fluorescence. From time-resolved fluorescence m easurements a dynamic equilibrium o f association in the excited state is deduced. 
  Reference    Z. Naturforsch. 49a, 578 (1994); eingegangen am 7. Februar 1994 
  Published    1994 
  Keywords    Fluorescence quenching, Silver ions, External heavy atom effect, Exciplex, Ground state com plexation 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0578.pdf 
 Identifier    ZNA-1994-49a-0578 
 Volume    49 
85Author    O. Böttcher, V. Meyer, D. H. SutterRequires cookie*
 Title    On the Validity of Additivity Rules for the Molecular Magnetizability Tensor and the Molecular 0-Tensor in van der Waals Complexes. A Rotational Zeeman Effect Study o f 1,1-Dideutero-Cyclopropane  
 Abstract    , who contributed so much to the development of microwave Fourier transform spectroscopy, on occasion of his 65th birthday The m olecular g-tensor and the magnetic susceptibility anisotropy of cyclopropane were deter­ mined by a microwave Fourier transform study of the rotational Zeeman effect of its 1,1-dideuterated isotopomer. The results ^ = 0.0 2 6 7 5 (2 3), gn = 0.06998(23), and £±—«Ü y = 8.80(31)-10-6 erg G " 2 m o l" 2 are in agreement with values determinea indirectly from van der Waals complexes. This finding provides experimental evidence that in van der Waals molecules additivity rules might hold to a high degree o f approxim ation for both types of tensors. Rotational Zeem an effect studies o f van der Waals com plexes may thus provide valuable extra information on their structures. 
  Reference    Z. Naturforsch. 49a, 585 (1994); received February 23 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0585.pdf 
 Identifier    ZNA-1994-49a-0585 
 Volume    49 
86Author    AxelA H OffRequires cookie*
 Title    Chaos Control and Neural Classification  
 Abstract    Chaotic behaviour in biological neural networks is known from various experiments. The recent finding that it is possible to "control" chaotic systems may help answer the question whether chaos plays an active role in neutral information processing. It is demonstrated that a m ethod for chaos control which was proposed by Pyragas can be used to let a chaotic system act like an autoassocia-tive memory for time signal inputs. Specifically a com bined chaotic and chaos control system can reconstruct unstable periodic orbits from incomplete information. The potential relevance o f these findings for neural information processing is pointed out. 
  Reference    Z. Naturforsch. 49a, 589—5 (1994); received December 20 1993 
  Published    1994 
  Keywords    Chaos control, Neural networks, Classification, Associative memory 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0589.pdf 
 Identifier    ZNA-1994-49a-0589 
 Volume    49 
87Author    Shi-Qi, H. Artm Ut Fuess2, Wolfgang Schmahl2, Roman Strauss1, Alarich Weiss1Requires cookie*
 Title    Orientational Order-Disorder and Phase Transition in Solid Trichloromethane Sulfonic Acid Chloride, C13C S 0 2C1  
 Abstract    By DTA DSC a phase transition of C13C S 0 2C1 was observed, 7],, = 227.4 K, AH" , = 7.10 kJ • M o l" 1; ASn i/R = 3.63; Tm = 418.5 K, AHm = 7.46 kJ • M o l ' 1, AS jk = 2.14. By X-ray'powder diffraction, the orientationally disordered solid phase I (plastic phase) was found to be body centered cubic, Im3m, Z = 2, a = 721.7 (5) pm at room temperature. The 35C1 N Q R quartet fades out at the transition temperature 7J,, = T{, and the fade out temperature T{ is identical for the four 35C1 NQ R lines. The N Q R spectrum shows a hysteresis in 7] u — Tu ,. 
  Reference    Z. Naturforsch. 49a, 594—5 (1994); received January 3 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0594.pdf 
 Identifier    ZNA-1994-49a-0594 
 Volume    49 
88Author    D. Irk, G. Ro K E, G. Ernot, H. Eger1, BerndPeter Schweiss1, AlarichW. Eiss2Requires cookie*
 Title    Neutron Diffraction Study of l,2,3-Trichlorobenzene-d3  
 Abstract    In order to explain the observed 35C1-NQR anom aly of the title com pound, a neutron diffraction study on single crystals was carried out at 295 K and 158 K. N o significant structural changes concerning phase transitions or molecular disorder between the two experiments were observed. The 
  Reference    Z. Naturforsch. 49a, 599 (1994); received February 21 1994 
  Published    1994 
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 Identifier    ZNA-1994-49a-0599 
 Volume    49 
89Author    Paolo Ghigna, M. Arco, ScaviniRequires cookie*
 Title    Kinetics and Mechanism of Nd2C u04 Synthesis  
 Abstract    The reaction N d20 3 -I-C uO -*■ N d 2C u 0 4 was investigated on the basis of the Wagner-Schmalz-ried theory of diffusion-driven reactions between crystalline solids, with the help of monodimen­ sional chemical diffusion measurements. It was found that the kinetics of the process is governed by C u2+ diffusion, and the chemical diffusion coefficient Z)(Cu2+) in the N d 2C u 0 4 matrix was obtained (9.9 • 10-13, 1.97 • 10-12 and 1.98 • 10" 11 cm 2 s -1 at 1223, 1273 and 1323 K, respectively). The rela­ tively low value of D (C u2+) was interpreted on the basis of the crystal structures of the compound and related materials, which in addition may suggest an alternative rationale for the interpretation of neodymium immobility. 
  Reference    Z. Naturforsch. 49a, 611—616 (1994); received M arch 14 1994 
  Published    1994 
  Keywords    N d 2C u 0 4 superconductor, Synthesis, Reaction mechanism, Kinetics, Chemical diffu­ sion 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0611.pdf 
 Identifier    ZNA-1994-49a-0611 
 Volume    49 
90Author    H. Ak-Jin, Jung, N. Ikola, G. Etoff, Eberhard LorbeerRequires cookie*
 Title    Radiation Induced Incorporation of CO in Pure and Aqueous Methanol  
 Abstract    Pure and aqueous m ethanol were used for radiation induced incorporation of CO at elevated pressure (up to 15 bar). The initial yields (G,) of the main products in pure methanol under 15 bar CO and 1 bar N 20 were found to be: G, (formaldehyde) = 3.80 and G;(glycolic aldehyde) = 2.0. For aqueous (10" 2 mol • d m -3) methanol under 15 bar CO (dose: 0.557 kGy, pH — 2): the yields were G (formaldehyde) = 5.44, G (glycolic aldehyde) = 4.0 and G (oxalic acid) = 7.7. At pH = 7 the yields were essentially lower, namely: G(formaldehyde) = 3.2, G(glycolic aldehyde) = 2.0, G(formate) = 3.8 and G (oxalate) = 5.0. Probable reaction-mechanisms for the product form ation are discussed. 
  Reference    Z. Naturforsch. 49a, 617—622 (1994); received February 14 1994 
  Published    1994 
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 Identifier    ZNA-1994-49a-0617 
 Volume    49 
91Author    Ewa Hawlicka, Tomasz LisRequires cookie*
 Title    An Effect of Urea on Association and Solvation of Ions in Aqueous Solutions of Alcohols  
 Abstract    The conductivity of N al in ternary solvents consisting of water, alcohol and urea has been determined at 25 °C in its dependence on the alcohol concentration. Viscosities and static dielectric constants of these ternary solvents have also been measured. It has been found th at in all studied solvents the limiting equivalent conductivities A0 are smaller than those in binary solvents despite of the lower viscosities. The observed effect indicates that urea prevents the dehydration of ions and also hinders the ionic association. These phenomena have led to the conclusion that urea molecules are able to solvate alcohol clusters similar to what has been observed for micelles. 
  Reference    Z. Naturforsch. 49a, 623—626 (1994); received December 31 1993 
  Published    1994 
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 Identifier    ZNA-1994-49a-0623 
 Volume    49 
92Author    S. I. Kuznetsov, E. V. Bryukhova, T.L K Hotsyanova, G. K. SeminRequires cookie*
 Title    35C1 and 79Br NQR Spectra in Cp2M H al2  
 Abstract    The 35C1 and 79 81Br NQR spectra of (C 5H 5)2M H al2 (M = T i, Mo, W, Zr, Hf; Hal = Cl, Br) are similar. They are quadruplets with splittings ranging from 2 to 7%. The averaged frequencies of chlorine and brom ine are related by a linear dependence. The tem perature dependence of 81 Br in C p2HfBr2 (in the range of 77 4= 224 K.) is of conventional character with frequencies slowly changing with tem perature; phase transitions have not been observed. 
  Reference    Z. Naturforsch. 49a, 627—629 (1994); received December 31 1993 
  Published    1994 
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 Identifier    ZNA-1994-49a-0627 
 Volume    49 
93Author    G. K. Semin, S. I. Kuznetsov, A. M. Raevsky, E. V. BryukhovaRequires cookie*
 Title    2,Sb and 35C1 NQR in RCN * SbCl5 Complexes  
 Abstract    35C1 and 121Sb NQR spectra of RCN • SbCl5 complexes with R = Et, n-Pr, i-Pr, n-Bu, n-C 5H n , C1(CH2)2, C 6H 4C H 2, Ph, Cl, Me, CC13 were measured an d /o r refined at 77 K. Redistribution of the "transferred charge" in the SbCl5 fragment of the complexes under study was investigated. The existence of a specific region of dispersion of the electron-nuclear m otions (D ENM) in RCN ■ SbC l5 complexes was established. of the electron-nuclear motions (DENM). 
  Reference    Z. Naturforsch. 49a, 630—634 (1994); received December 31 1993 
  Published    1994 
  Keywords    Complexes RCN ■ SbCls, NQR, 121Sb, 35C1, dispersion 
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 Identifier    ZNA-1994-49a-0630 
 Volume    49 
94Author    A. Chrzanowska, K. SokalskiRequires cookie*
 Title    On the Microscopic Stress Tensor for Anisotropic Molecules in Homogeneous Systems  
 Abstract    The flowing nematic liquid crystal is considered in the small velocity gradient approximation. The molecular expression for the stress tensor is improved by use of the procedure of Doi. The symmetric and antisymmetric parts of the microscopic stress tensor are shown to differ by the formfactor in comparison to forms which have been used so far. The consequences for the molecular hydrody­ namic theories are considered. 
  Reference    Z. Naturforsch. 49a, 635—638 (1994); received December 15 1993 
  Published    1994 
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 Identifier    ZNA-1994-49a-0635 
 Volume    49 
95Author    ValentinP. Feshin, PeterA. Nikitin, IsmailA. AlievRequires cookie*
 Title    79'81Br NQR Spectra of Alkyl(4-Bromophenyl)Sulphides  
 Abstract    The 79,81Br NQR spectra of compounds of the series 4-BrC6H 4SR with R = (C H 2)"H (n = 1,2, 4 -9), (CH 2)I)C H (C H 3)2 (n = 0 -2) and C H m(C H 3)3_m were obtained at 77 K. The halogen atom electron densities in these compounds and chlorine-containing analogs are compared. The ratio of the amplitudes of the N Q R frequency oscillations in chlorine-and brom ine-containing compounds with R = (CH2)nH corresponds to the ratio of the polarizabilities of 35C1 and 79Br. The variation of the alkyl groups R influences the electron distribution of the halogen atom. 
  Reference    Z. Naturforsch. 49a, 639—641 (1994); received November 4 1993 
  Published    1994 
  Keywords    NQR spectra, Frequency, Alkyl(4-bromophenyl)sulphides, Oscillation effect 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0639.pdf 
 Identifier    ZNA-1994-49a-0639 
 Volume    49 
96Author    A. K. Ittel1, A. W. Illm, H.-GW. Ener1, R. R. Ichter1, R.P H Uebener1, J. P. Arisi2Requires cookie*
 Title    New Concept o f a Scanning Laser M icroscope Integrated Inside an Encapsulated Cryogenic Sam ple Stage  
 Abstract    We introduce a compact scanning laser microscope that is applicable for direct visualization of dissipative electric struc­ tures in solid state systems. In order to overcome the dis­ turbing influence of any background radiation, the shielded sample cryostage incorporates the complete microscope con­ sisting of a laser diode, the deflection unit, and the focussing optics. O ur imaging method provides access to a class of nonlinear transport phenomena that so far have eluded un­ perturbed observation. 
  Reference    Z. Naturforsch. 49a, 642—644 (1994); received April 9 1994 
  Published    1994 
  Keywords    Scanning laser microscopy, Cryogenics, N on­ linear transport phenomena 
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 Identifier    ZNA-1994-49a-0642_n 
 Volume    49 
97Author    U. Spoerel, H. Dreizler, W. StahlRequires cookie*
 Title    On the Sign o f the O ff-D iagon al Elem ents o f the N uclear Quadrupole Coupling Tensor  
 Abstract    If off-diagonal elements of the nuclear quadrupole cou­ pling tensor are determined from the rotational spectrum of only one isotopomer, the magnitude of the off-diagonal ele­ ments and the sign of the product XabXbcXac can be obtained but not the individual signs of the off-diagonal elements. In this article we give two proofs for this fact. A determ ination of the individual signs of the off-diagonal elements is only possible by analysing the spectra of more isotopomers. 
  Reference    Z. Naturforsch. 49a, 645—646 (1994); received M arch 25 1994 
  Published    1994 
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 Identifier    ZNA-1994-49a-0645_n 
 Volume    49 
98Author    G. GrimRequires cookie*
 Title    Effective Boson-Fermion Dynamics for Subfermion Models  
 Abstract    Effective composite particle dynamics can be derived by weak mapping of quantum fields. This m ethod was already applied to derive effective boson or boson-fermion coupling theories from a nonlinear subfermion field. In this paper we present an extension of those calculations to the general group theoretical treatm ent of two-fermion bound states and their coupling to (elementary) fermions within an arbitrary nonlinear spinor-isospinor field model. The resulting effective field equations are com pared with the corresponding phenomenological expressions which for example underly the standard electroweak theory. PACS 1 1 .1 0 -Field theory. PACS 12.10 -Unified field theories and models. PACS 12.35 -Composite models of particles. 
  Reference    Z. Naturforsch. 49a, 649—662 (1994) 
  Published    1994 
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 Identifier    ZNA-1994-49a-0649 
 Volume    49 
99Author    S. Sh, Soulayman, C. M. Ch, Ch Arti, Ch, GuilpinRequires cookie*
 Title    Anharmonic Self-Consistent Theory of Crystals. II. The 2d and 3d Quartic Crystal Models  
 Abstract    In this paper we apply the method developed in part I for describing the crystalline state of two and three dimensional inert gases. For strong anharm onicity of fourth order, the equations of state of these gases are obtained. This way we calculate the thermoelastic properties of two and three dimensional argon, krypton and xenon using the Lennard-Jones potential. The corrections to the Helmholtz free energy and thermodynamic properties due to quantum effects are considered. The results are compared with the available experimental data. 
  Reference    Z. Naturforsch. 49a, 663—670 (1994); received December 18 1993 
  Published    1994 
  Keywords    Inert gases, Anharmonicity, Thermodynamic properties, Two-and three-dimensional crystals 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0663.pdf 
 Identifier    ZNA-1994-49a-0663 
 Volume    49 
100Author    Danuta Bauman, Thomas Hanemann, Eryk WolarzRequires cookie*
 Title    Spectral Properties of Some Naphthalene Derivatives of Bicarboxylic Acid; Comparison of Experimental Results with Theoretical Predictions  
 Abstract    The basic electronic quantities of some dichroic dyes, naphthalene derivatives of bicarboxylic acid, have been evaluated theoretically using a semi-empirical INDO (intermediate neglect of differential overlap) Cl (configuration interaction) approach. The theoretical data have been com­ pared with the experimental results obtained from the absorption and fluorescence measurements of the dyes dissolved in toluene and oriented in liquid crystal 8CB. Additionally, the order parame­ ters of the dyes in smectic A and nematic phases of 8CB have been determined. 
  Reference    Z. Naturforsch. 49a, 671—679 (1994); received March 24 1994 
  Published    1994 
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 Identifier    ZNA-1994-49a-0671 
 Volume    49 
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