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2001[X]
61Author    Harald Fripertinger, Ivan Gutman3, Adalbert Kerber6, Axel Kohnertb, Dusica Vidovic3Requires cookie*
 Title    The Energy of a Graph and its Size Dependence. An Improved Monte Carlo Approach  
 Abstract    In an earlier work [Gutman et al., Chem. Phys. Lett. 297, 428 (1998)] the average energy (E) o f graphs with n vertices and m edges was examined, in particular its dependence on n and m . The quantity (E) was computed from a set of randomly, but not uniformly, constructed (n ,m)-graphs. We have now improved our method by constructing the (n,m)-graphs uniformly, so that every (n , m)-graph has equal probability to be generated. Differences between the old and new approaches are significant only in the case of graphs with a small number o f edges. 
  Reference    Z. Naturforsch. 56a, 342—346 (2001); received April 2 2001 
  Published    2001 
  Keywords    Energy (of Graph), Total 7r-electron Energy, Random Graphs, Monte Carlo Methods 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0342.pdf 
 Identifier    ZNA-2001-56a-0342 
 Volume    56 
62Author    B. H. LavendaRequires cookie*
 Title    Is Relativistic Quantum Mechanics Compatible with Special Relativity?  
 Abstract    The transformation from a time-dependent random walk to quantum mechanics converts a modi­ fied Bessel function into an ordinary one together with a phase factor e,ir/2 for each time the electron flips both direction and handedness. Causality requires the argument to be greater than the order o f the Bessel function. Assuming equal probabilities for jumps ± 1 , the normalized modified Bessel function o f an imaginary argument is the solution o f the finite difference differential Schrödinger equation whereas the same function o f a real argument satisfies the diffusion equation. In the nonrelativistic limit, the stability condition o f the difference scheme contains the mass whereas in the ultrarelativistic limit only the velocity of light appears. Particle waves in the nonrelativistic limit become elastic waves in the ultrarelativistic limit with a phase shift in the frequency and wave number of 7r/2. The ordinary Bessel function satisfies a second order recurrence relation which is a finite difference differential wave equation, using non-nearest neighbors, whose solutions are the chirality components o f a free-particle in the zero fermion mass limit. Reintroducing the mass by a phase transformation transforms the wave equation into the Klein-Gordon equation but does not admit a solution in terms o f ordinary Bessel functions. However, a sign change of the mass term permits a solution in terms o f a modified Bessel function whose recurrence formulas produce all the results of special relativity. The Lorentz transformation maximizes the integral o f the modified Bessel function and determines the paths o f steepest descent in the classical limit. If the definitions of frequency and wave number in terms o f the phase were used in special relativity, the condition that the frame be inertial would equate the superluminal phase velocity with the particle velocity in violation o f causality. In order to get surfaces o f constant phase to move at the group velocity, an integrating factor is required which determines how the intensity decays in time. The phase correlation between neighboring sites in quantum mechanics is given by the phase factor for the electron to reverse its direction, whereas, in special relativity, it is given by the Doppler shift. 
  Reference    Z. Naturforsch. 56a, 347—365 (2001); received February 14 2001 
  Published    2001 
  Keywords    Random Walks, Quantum Mechanics, Special Relativity, Ordinary and Modified Bessel Functions 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0347.pdf 
 Identifier    ZNA-2001-56a-0347 
 Volume    56 
63Author    Woo-Pyo Hong, Myung-Sang YoonaRequires cookie*
 Title    Analytic Solitary-wave Solutions for Modified Korteweg -de Vries Equation with /-dependent Coefficients  
 Abstract    We find analytic solitary wave solutions for a modified KdV equation with i-dependent coeffi­ cients o f the form u t — 6a (t) u u x + ß (t) u xxx — 6 7u 2u x = 0. We make use of both the application o f the truncated Painleve expansion and symbolic computation to obtain an auto-Bäcklund trans­ formation. We show that kink-type analytic solitary-wave solutions exist under some constraints on a (t), ß (t) and 7 . 
  Reference    Z. Naturforsch. 56a, 366—370 (2001); received November 16 2000 
  Published    2001 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0366.pdf 
 Identifier    ZNA-2001-56a-0366 
 Volume    56 
64Author    DurgaPrasad OjhaRequires cookie*
 Title    Nematogenic Behaviour of EPPV in a Dielectric Medium. A Theoretical Study  
 Abstract    4-(4/-ethoxyphenylazo) phenyl valerate (EPPV) is a nematic liquid crystal, which shows a nematic mesophase at 352 K and becomes an isotropic melt at 401 K. A theoretical study o f the molecular order­ ing has been carried out on the basis of intermolecular interaction energy calculations. The CNDO/2 method has been employed to compute the net atomic charge and atomic dipole components at each atom­ ic centre of the molecule. Modified Rayleigh-Schrödinger perturbation treatment has been employed to calculate the interaction energy between a molecular pair. The probability of the occurrence of a partic­ ular configuration in a dielectric medium has been calculated using the Maxwell-Boltzmann formula. The flexibility of various configurations has been studied in terms of the variation of the probability due to a small departure from the most probable configurations. On the basis of stacking, in-plane and terminal interactions, all possible geometrical arrangements between a molecular pair have been considered, and the most favourable configuration of pairing has been obtained. An attempt has been made to explain the nematogenic behaviour of liquid crystals based on the parameters introduced in this paper. 
  Reference    Z. Naturforsch. 56a, 371—375 (2001); received December 4 2000 
  Published    2001 
  Keywords    CNDO/2 Method, Interaction Energy, Statistical Distribution 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0371.pdf 
 Identifier    ZNA-2001-56a-0371 
 Volume    56 
65Author    Z. Akdeniz, A. Karaman, M. P. TosiaRequires cookie*
 Title    Ionic Interactions in Actinide Tetrahalides  
 Abstract    We determine a model of the ionic interactions in AX 4 compounds (where A is an atom in the actinide series from Th to Am and X = F, Cl, Br or I) by an analysis o f data on the static and dynamic structure of their molecular monomers. The potential energy function that we adopt is taken from earlier work on rare-earth trihalides [Z. Akdeniz, Z. Q q e k and M. P. Tosi, Z. Naturforsch. 55a, 861 (2000)] and in particular allows for the electronic polarizability of the actinide ion. This polarizability quantitatively determines the antisymmetric-bending vibrational mode, but its magnitude remains compatible with a symmetric tetrahedral shape o f the molecule at equilibrium. The fluorides have an especially high degree o f ionic character, and the interionic-force parameters for each halide of the U, Np, Pu and Am series show regular trends, suggesting that extrapolations to the other transuranic-element halides may usefully be made. The Th compounds show some deviations from these trends, and the interionic-force model that we determine for ThCl4 differs somewhat from that obtained in a previous study. We therefore return on the evaluation of the relative stability of charged oligomers of ThCl4 and ZrCl4 and find confirmation o f our earlier results on this problem. 
  Reference    Z. Naturforsch. 56a, 376—380 (2001); received March 12 2001 
  Published    2001 
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 Identifier    ZNA-2001-56a-0376 
 Volume    56 
66Author    Z. Akdeniz, M. Gaune-Escard3, M.P T OsibRequires cookie*
 Title    Static and Dynamic Structure of Molecular Monomers and Dimers of the Rare-earth Fluorides  
 Abstract    We determine a model o f the ionic interactions in RF3 compounds, where R is a rare-earth element in the series from La to Lu, by an analysis o f data on the bond length and the vibrational mode frequencies o f the PrF3, GdF3 and HoF3 molecular monomers. All RF3 monomers are predicted to have a pyramidal shape, displaying a progressive flattening o f the molecular shape in parallel with the lanthanide contraction o f the bond length. The vibrational frequencies of all monomers are calculated, the results being in good agreement with the data from infrared studies of matrix-isolated molecules. We also evaluate the geometrical structure and the vibrational spectrum of the La2F6 and Ce2F6 dimers, as a further test o f the proposed model. -PACS 36.40.Wa (Charged clusters) 
  Reference    Z. Naturforsch. 56a, 381—385 (2001); received April 2 2001 
  Published    2001 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0381.pdf 
 Identifier    ZNA-2001-56a-0381 
 Volume    56 
67Author    B.Thimme Gowda, Helmut Paulus3, Hartmut FuessaRequires cookie*
 Title    Structural Studies on Substituted 7V-(phenyl)-2,2-DichIoroacetamides, 2/4-XC6H4 NHCO CHCI2 (X = H, Cl or CH3)  
 Abstract    The effect o f substitution in the phenyl ring on the crystal systems of amides o f the type, 2/4-XC 6H4-NHCO-CHCl2 (X = H, Cl or CH3), has been studied by determining the crystal structures o f the compounds, iV-(phenyl)-2,2-dichloroacetamide, C6H5-NHCO-CHCl2 (PhDCA); N-(2-chlorophenyl)-2,2-dichloroacetamide, 2-ClC6H4-NHCO-CHCl2 (o-ClPhDCA), jY-(4-chlorophenyl)-2,2-dichloroacetamide, 4-ClC6H4-NHCO-CHCl2 (p-ClPhDCA) and N -(4-methylphenyl)-2,2-dichloroacetamide, 4-CH3C6H4-NHCO-CHCl2 (p-CH3PhDCA) and analysed the data along with our earlier crystal structures of the compounds, N-(phenyl)-2,2,2-trichloro-acetamide (PhTCA), N-(2-chlorophenyl)-2,2,2-trichloroacetamide (o-ClPhTCA), N -(4-chloro-phenyl)-2,2,2-trichloroacetamide (p-ClPhTCA), N-(4-methylphenyl)-2,2,2-trichloroacetamide (p-CH3PhTCA); N-chloro-N-(phenyl)-2,2-dichloroacetamide (NClPhDCA), N-chloro-N-(phenyl)-2,2,2-trichloroacetamide (NClPhTCA) and N-(phenyl) acetamide (PhA). The crystal type, space group, formula units and lattice constants in A of the new structures are; PhDCA: monoclinic, P 2,/c, Z = 4, a = 8.785(3), b = 11.139(4), c = 9.521(3), ß = 97.47(2)°; o-CIPhDCA: monoclinic, P 2,/c, Z = 4, a = 4.711(2), b = 11.234(6), c = 19.191(8), ß = 98.12(2)°; p-CIPhDCA: monoclinic, P 2,/c, Z = 8, a = 18.627(5), b = 11.533(3), c = 9.583(3), ß = 102.43(2)°, and /?-CH3PhDCA: orthorhombic, Pbca, Z = 8, a = 9.464(3), b = 9.894(3), c = 21.973(7). The compound /?-ClPhDCA shows two molecules in its asymmetric unit. This is in agreement with the multiple lines observed in the 35Cl NQR spectra of the compound. The crystal systems of the chlorosubstituted and methyl substituted chloroacetamides get interchanged on replacement of the side chain -CHC12 by -CC13. C(i)-C(j) ring distances show no significant variations with the substitution either at the side chain or in the phenyl ring. C(ring)-N and C (0)-N bond distances are also not much affected by either ring or side chain substitution, but are affected by N-chlorination, while the C -0 bond length is slightly shortened by the replacement o f the -CH3 group by -CC13, the introduction o f electron withdrawing group into the phenyl ring or by N-chlorination. Deviations o f C2(ring)-Cl(ring)-N, C6(ring)-Cl(ring)-N and C (ring)-N-C(0) bond angles from 120° narrow down on substitution either in the phenyl ring or in the side chain, but the latter increases on W-chlorination o f the compounds. 
  Reference    Z. Naturforsch. 56a, 386—394 (2001); received February 15 2001 
  Published    2001 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0386.pdf 
 Identifier    ZNA-2001-56a-0386 
 Volume    56 
68Author    P. Andonov, H. E. Fischer3 ', P. Palleau3, S. KimurabRequires cookie*
 Title    Structural Study of Liquid Lithium Niobate by Neutron Diffraction Role of the Li Atom in the Clustering Near Solidification  
 Abstract    The structure of liquid LiNb03 has been investigated by neutron diffraction using samples with dif­ ferent isotopic composition of lithium. The intensity scattered by these samples has been measured for momentum transfers 0.4 A-1 < Q < 17.1 Ä-1 and temperatures 1600 K>T> 1500 K, which include the undercooling domain. From an analysis of the correlation functions Gt j (r) of the atomic pairs Li-Li, Li-Nb, Li-O and their structural evolutions, given by A G,_v (r) = G,_j (r)1500 -G,_, (r)1550 made with reference to the crystalline LiNb03 ferroelectric structure, it was possible to confirm a local ordering similar to that of the crystal. The presence of clusters (groupings of N b 03 octahedra) is confirmed. Both regular and irregular N b06 octahedra are observed in the liquid near solidification. With its high mobil­ ity in the melt, the Li atom plays an important role in the clustering: the Li— O and Li— Nb bonds make possible the staking of four octahedra groups into clusters of eight octahedra or more. The Li-Li bonds join these groups. The diameter of the clusters is a least 22 A in the undercooling regime. 
  Reference    Z. Naturforsch. 56a, 395—406 (2001); received February 12 2001 
  Published    2001 
  Keywords    Structure of Liquids, Neutron Scattering, Atomic Clusters, Liquid Lithium Niobate 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0395.pdf 
 Identifier    ZNA-2001-56a-0395 
 Volume    56 
69Author    A. Kawski, B. Kukliriski, P. BojarskiRequires cookie*
 Title    Ground and Excited State Dipole Moments of BADAN and ACRYLODAN Determined from Solvatochromic Shifts of Absorption and Fluorescence Spectra  
 Abstract    The electric dipole moments in the ground a , and excited states ^ of the fluorescent probes BADAN (6-bromoacetyl-2-dimethylamino-naphthalene) and ACRYLODAN (6-acrylolyl-2-dimethylamino-naphthalene) are determined from the solvatochromic shifts of their absorption and fluorescence spec­ tra for two Onsager interaction radii (a = 4.2 and 4.6 A). The obtained values of and ^ for BADAN are comparable to those of PRODAN, while for ACRYLODAN they are distinctly greater. 
  Reference    Z. Naturforsch. 56a, 407—411 (2001); received March 16 2001 
  Published    2001 
  Keywords    Solvatochromic Shifts, Dipole Moments in the Ground and Excited States, BADAN and ACRYLODAN-Fluorescent Probes 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0407.pdf 
 Identifier    ZNA-2001-56a-0407 
 Volume    56 
70Author    MyriamS. De Giambiagi, Mario Giambiagi, Aloysio Paiva De FigueiredoRequires cookie*
 Title    Revisiting Julg's Structural Approach to Aromaticity  
 Abstract    Julg's classical formula for aromaticity is updated so as to involve bond indices. A simple CNDO/2 calculation is shown to account satisfactorily for heterocyclic typical rings and other mis­ cellaneous systems. Results are compared with a multicenter MO bond index recently introduced as an aromaticity measure. 
  Reference    Z. Naturforsch. 56a, 413 (2001); received January 16 2001 
  Published    2001 
  Keywords    Aromaticity, Julg's Formula, Multicenter MO Bond Index 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0413.pdf 
 Identifier    ZNA-2001-56a-0413 
 Volume    56 
71Author    Mohamed Fahmy, El-SayedRequires cookie*
 Title    Magnetohydrodynamic Stability of Two Streaming Superposed Viscoelastic Conducting Fluids  
 Abstract    The stability o f the plane interface separating two Oldroydian viscoelastic superposed moving fluids of uniform densities when immersed in a uniform horizontal magnetic field has been in­ vestigated. The stability analysis has been carried out, for mathematical simplicity, for two highly viscous fluids o f equal kinematic viscosities. It is found that the potentially stable configuration remains stable if the fluids are at rest, while it becomes unstable if the fluids move. The stability criterion is found to be independent o f the viscosity and viscoelasticity, and to be dependent on the orientation of the magnetic field and the magnitudes of the fluids and Alfven velocities. It is also found that the potentially unstable configuration remains unstable in the absence of average fluid velocities, or in the presence of fluid velocities and absence of a magnetic field. The magnetic field is found to stabilize a certain wavenumbers range o f the unstable configuration even in the presence o f the effects of viscoelasticity. The behaviour of growth rates with respect to the stress relaxation time, strain retardation time, fluid and Alfven velocity parameters is examined analytically, and the stability conditions are obtained and discussed. -Pacs: 47.20.-k; 47.50.+d; 47.65.+a. 
  Reference    Z. Naturforsch. 56a, 416 (2001); received December 13 2000 
  Published    2001 
  Keywords    Hydrodynamic Stability, Non-Newtonian Fluid Flows, Magnetohydrodynamics 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0416.pdf 
 Identifier    ZNA-2001-56a-0416 
 Volume    56 
72Author    A. Guarnieri, A. HuckaufRequires cookie*
 Title    The Rotational Spectrum of (170)Ketene  
 Abstract    The rotational spectrum of H2CC17O in the ground vibrational state has been investigated between 20 and 330 GHz. From 82 /?-branch transitions a set of rotational constants and several centrifugal distortion constants could be derived, employing the Watson 5-reduction formalism. The obtained rotational constants in MHz are: A = 282071.6(223), B = 10013.4764(28), C = 9655.9118(24). The nuclear quadrupole coupling structure of the J'KaiKci <— JKaKc = loi Ooo line has been recorded by means of molecular beam Fourier transform microwave spectroscopy allowing the determination o f the nuclear quadrupole constant Xaa. = -1.534(54) MHz (without considering the spin-rotation interaction). A recalculation of the rs-structure has also been carried out, using the constants of the new isotopomer. The result agrees with the values reported by East et al. in 1995. This is, to our knowledge, the first reported investigation of the H2CC170 rotational spectrum. 
  Reference    Z. Naturforsch. 56a, 440—446 (2001); received April 9 2001 
  Published    2001 
  Keywords    Rotational Spectra, Structure, Ketene, Isotopomer 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0440.pdf 
 Identifier    ZNA-2001-56a-0440 
 Volume    56 
73Author    Peter Nikolov, Irina Petkova, Stefan Stoyanov3Requires cookie*
 Title    Media Effect upon the Fluorescence Ability of Differently Substituted a-Cyanostilbenes  
 Abstract    The steady state and dynamic photophysical characteristics of a-cyanostilbene derivatives have been investigated in solution and in Polyvinylchloride (PVC) film at 300 K as well as in a frozen matrix at 77 K. While no emission is observed in solution, a significant fluorescence ability is registered both in PVC and frozen media. This fact is attributed to the matrix effect, which lessens the possible intramolecular motions around the central double bond. No phosphorescence at 77 K is observed. The fluorescence lifetimes at 77 K are compared with literature data for similar chemically fixed structures. 
  Reference    Z. Naturforsch. 56a, 447—451 (2001); received January 23 2001 
  Published    2001 
  Keywords    a-Cyanostilbene Derivatives, Fluorescence, Matrix Effect 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0447.pdf 
 Identifier    ZNA-2001-56a-0447 
 Volume    56 
74Author    Irina Petkova, ApostolosJ. Maroulisa, Constantina Hadjiantoniou-Maroulis3, Peter NikolovRequires cookie*
 Title    Electronic Spectral Investigations upon the Photochemical Transformations of Some Substituted l-(N,N-bisacyl)amino-4,5-diphenyl-l,2,3-triazoles  
 Abstract    The objective of this report is to investigate the steady state and dynamic photophysical and photochemical properties o f l-(N,N-bisacyl)amino-4,5-diphenyl-1,2,3-triazoles in solvents o f dif­ ferent polarity at room temperature and in frozen matrix at 77 K. On the basis o f the comparison of their UV absorption and luminescence spectra with those of 4,5-diphenyl-1,2,3-triazole and diben-zamide (model compounds), cleavage o f the N-N bond in the title compounds after irradiation with polychrome UV light is proved. 
  Reference    Z. Naturforsch. 56a, 452 (2001); received May 14 2001 
  Published    2001 
  Keywords    l-(N ,N-bisacyl)am ino-1,2,3-triazoles, Absorption, Luminescence, UV Irradiation, N-N Bond Cleavage 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0452.pdf 
 Identifier    ZNA-2001-56a-0452 
 Volume    56 
75Author    Masahiko Matsumiya, Ryuzo Takagi3Requires cookie*
 Title    Molecular Dynamics Study on the Adsorption Selectivity for Negative Elements in Aluminosilicates  
 Abstract    For the pyrochemical reprocessing o f spent metallic nuclear fuels in molten salt baths it is important to investigate the adsorption selectivity o f cations in aluminosilicates. A molecular dynamics simulation has been performed on sodalite and zeolite with exchangeable monovalent and multivalent cationic fission products at 673 K in order to calculate their self-diffusion coefficients in the aluminosilicate framework and estimate the selectivity o f the exchangeable cations. The results enables us to conclude that the self-diffusion coefficients of monovalent cations decrease with increasing ionic radius. The order of the adsorption selectivity is Li < K < Na < Cs in sodalite and Li < Na < K < Cs in zeolite. The self-diffusion coefficients of multivalent cations are almost independent o f the ionic radius, and these cations are in aluminosilicates more stable than monovalent cations. The results are consistent with the experimental results. 
  Reference    Z. Naturforsch. 56a, 459—165 (2001); received February 9 2001 
  Published    2001 
  Keywords    Adsorption Selectivity, Aluminosilicates Framework, Molecular Dynamics Simulation, Negative Elements, Self-diffusion Coefficient, Sodalite, Zeolite 
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 Identifier    ZNA-2001-56a-0459 
 Volume    56 
76Author    Masahiko Matsumiya, Ryuzo Takagi3Requires cookie*
 Title    A Molecular Dynamics Simulation of the Electric and Thermodynamic Properties in Molten (Nd1/3, Na or K)C1 Mixtures  
 Abstract    Molecular dynamics simulations have been carried out on molten (N d 1/3, K)C1 at 1065 and 1073 K and (N d 1/3, Na)Cl at 1124 K for various compositions. The calculated self-exchange velocity (v), self-diffusion coefficient (D), electrical conductivity (k) and enthalpy o f mixing (A //mix) were compared with the corresponding experimental values. The calculated results re­ 
  Reference    Z. Naturforsch. 56a, 466—472 (2001); received May 3 2001 
  Published    2001 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0466.pdf 
 Identifier    ZNA-2001-56a-0466 
 Volume    56 
77Author    Wen-Chen Zhenga, Shao-Yi Wua, Jian ZibRequires cookie*
 Title    Defect Structures for Fe3+, Mn2+, and Ni3+ Impurities in Wuritzite GaN Crystals  
 Abstract    Electron paramagnetic resonance (EPR) zero-field splittings D for Mn2+ and Fe3+ in wurtzite GaN crystals are studied from high-order perturbation formulas based on the spin-orbit mechanism in both weak-and strong-field schemes. From these studies it can be seen that the Mn2+ or Fe3+ 
  Reference    Z. Naturforsch. 56a, 473—477 (2001); received April 20 2001 
  Published    2001 
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 Identifier    ZNA-2001-56a-0473 
 Volume    56 
78Author    Uwe Hoppe, Rainer Kranold, Emil Gattefa, Jörg Neuefeindb, DavidA. KeencRequires cookie*
 Title    An X-ray and Neutron Scattering Study of the Structure of Zinc Vanadate Glasses  
 Abstract    The short-range order of vitreous V20 5 and of three (Zn0)Jt(V20 5)1_x glasses with x = 0.2, 0.4, and 0.5 is studied by X-ray and neutron diffraction experiments where the change of the contrast allows to resolve the V -0 and Z n -0 correlations. The V -0 and the Z n -0 first-neighbor peaks are approximat­ ed by several Gaussian functions. In case of vitreous V20 5 two obvious V -0 distances exist which are related with V 0 4 and V 0 5 units. With ZnO additions the V -O coordination number decreases from 4.4 in vitreous V20 5 to 4.0 in the metavanadate glass where the strongest decrease of the fraction of V 0 5 units is found for glasses of * < 0.2. Dominantly, the V 0 5 groups are linked with the neighboring units by comers. The Z n-0 coordination numbers of the modified glasses are about five with closest dis­ tances of = 0.200 nm. 
  Reference    Z. Naturforsch. 56a, 478—4 (2001); received April 3 2001 
  Published    2001 
  Keywords    Neutron Scattering, X-ray Scattering, Short-range Order, Vanadate Glasses 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0478.pdf 
 Identifier    ZNA-2001-56a-0478 
 Volume    56 
79Author    Stanislaw Urban, Albert Wiirflinger3Requires cookie*
 Title    DTA and Dielectric Studies under Pressure of a Smectogen Substance with a Strong Perpendicular Dipole Moment  
 Abstract    The phase diagram of a substance with two CN groups attached to the benzene ring at lateral posi­ tions (CNCN) has been obtained with differential thermal analysis (DTA). The pressure range of the smectic A phase is limited, resulting in a triple point (Cr, SA, L) at 135 MPa and 371 K. However, the SA-phase exists also above the triple point as a metastable phase. The transverse relaxation times rx were obtained from the dielectric spectra measured for several isotherms as a function of pressure with­ in the SA-phase of CNCN. The activation volume, A#Vj_ = RT (d In = (52 ± 3) cm3/mol is larg­ er than A Vj|, recently derived from the pressure dependence of the longitudinal relaxation times for other substances in the SA-phase. It is concluded that due to steric hindrances made by the cyano groups the molecular rotations around the long axes become strongly slowed down by pressure and the smec­ tic phase disappears 
  Reference    Z. Naturforsch. 56a, 489—4 (2001); received April 23 2001 
  Published    2001 
  Keywords    Liquid Crystals, Smectic A, DTA, Phase Diagram, Dielectric Relaxation, High Pressure 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0489.pdf 
 Identifier    ZNA-2001-56a-0489 
 Volume    56 
80Author    RehabM. Kubba, Muthana ShanshalRequires cookie*
 Title    Frequencies and Normal Modes of Benz(a)anthracene. A MINDO/3-FORCES Treatment  
 Abstract    Quantum mechanical calculations, based on the MINDO/3-FORCES method, of the vibration fre­ quencies and IR absorption intensities of benz(a)anthracene are reported and compared with calculated vibration frequencies of that molecule. For the first time a complete normal coordinate analysis for the molecule is reported. Interesting correlations between vibration motions of the same type but different symmetries are reported. 
  Reference    Z. Naturforsch. 56a, 493—498 (2001); received September 8 2000 
  Published    2001 
  Keywords    Benz(a)anthracene, Vibration Frequencies, MINDO/3-FORCES 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0493.pdf 
 Identifier    ZNA-2001-56a-0493 
 Volume    56 
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