| | 21 | Author
| Agnieszka Chrzanowska, PawelT. Jochym | Requires cookie* | | | Title
| Microscopic Stress Tensor of Nematic Liquid Crystal Binary Mixtures  | | | | Abstract
| A microscopic stress tensor for the binary nematic mixture of anisotropic molecules is presented. Its simple additive character is beneficial for hydrodynamics studies. We pay attention to mixtures of disc and rodlike molecules which may exhibit interesting hydrodynamic properties. | | | |
Reference
| Z. Naturforsch. 51a, 147—150 (1996); received September 6 1995 | | | |
Published
| 1996 | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0147.pdf | | | | Identifier
| ZNA-1996-51a-0147 | | | | Volume
| 51 | |
| 22 | Author
| Hager Gritli, Gilberte Chambaud, Pavel Rosmus | Requires cookie* | | | Title
| On the Interaction of the S~ Ion with H 2 at low Collision Energies | | | | Abstract
| Potential energy functions have been calculated for the reactions S~(: P) + H 2 — HS + H~ and S~(~P) + H 2 — HS" + H for low collision energies and collinear geometries. Unlike in the O -+ H 2 system, only very flat polarisation minima in the structures S~...H : and SH...H" have been found. They are not deep enough to support the formation of a complex in the detachment, in the reactive detachment and in the reactive charge transfer processes of the S~ + H : collision system. | | | |
Reference
| Z. Naturforsch. 51a, 151—154 (1996); received December 23. 1995 | | | |
Published
| 1996 | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0151.pdf | | | | Identifier
| ZNA-1996-51a-0151 | | | | Volume
| 51 | |
| 23 | Author
| C. Cruz, J. L. Figueirinhas, P. J. Sebastião, A. C. Ribeiro, F. Noack, H. T. Nguyen, B. Heinrich, D. Guillon, I.P C M | Requires cookie* | | | Title
| Molecular Dynamics in the Columnar and Lamellar Mesophases of a Liquid Crystal of Biforked Molecules | | | | Abstract
| In this work we present the first study of molecular dynamics in the S c and 4> h mesophases of a liquid crystal of biforked molecules. This study was performed by means of proton NMR relaxation measurements obtained at different temperatures in the studied phases, combining standard and fast field-cycling techniques in order to cover a large domain of Larmor frequencies (100 Hz-300 MHz). The experimental results were analysed considering the potential contributions of different relax-ation mechanisms, namely local molecular rotational reorientations, self-diffusion and collective movements. The description of the contributions of the rotational reorientations and self-diffusion mechanisms are not quite different in the two studied phases. The main distinction in the molecular dynamics is found in the low Larmor frequency range dominated by the collective movements. While in the S c phase this contribution can be described by the law characteristic of smectic layer undulations, the contribution of the collective movements in the </> h phase can be assigned to elastic deformation of the columns. | | | |
Reference
| Z. Naturforsch. 51a, 155—166 (1996); received November 29 1995 | | | |
Published
| 1996 | | | |
Keywords
| NMR, Proton Relaxation, Molecular Dynamics, Biforked Molecules, </> h Mesophase | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0155.pdf | | | | Identifier
| ZNA-1996-51a-0155 | | | | Volume
| 51 | |
| 27 | Author
| Uwe Hoppe, Günter Walter, Dörte Stachel, AlexC. Hannon | Requires cookie* | | | Title
| Short-Range Order in KP0 3 Glass Studied by Neutron and X-Ray Diffraction | | | | Abstract
| The short-range order of KP0 3 glass has been studied by diffraction methods in order to make evident the different behaviour of the P-O bonds within the P0 4 tetrahedron. The oxygen sites are devided into bridging and terminal (non-bridging) oxygen sites, corresponding to two P-0 bond lengths, the difference of which amounts to 14.5 pm. Previous conclusions about the changes of the P-0 bond lengths under the influence of modifier cations of different electric field strength are corroborated. The K-O environments reveal two apparently different distances r KO with equal contributions to the total K-0 coordination number of about 6.7. To explain this phenomenon, the K + cations are suggested to be located in non-spherical cavities. | | | |
Reference
| Z. Naturforsch. 51a, 179—186 (1996); received January 27 1996 | | | |
Published
| 1996 | | | |
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| | | | | TEI-XML for
| default:Reihe_A/51/ZNA-1996-51a-0179.pdf | | | | Identifier
| ZNA-1996-51a-0179 | | | | Volume
| 51 | |
| 28 | Author
| Piercarlo Mustarelli, Corrado Tomasi, Marco Villa, C.S T E, -CN R And | Requires cookie* | | | Title
| Heat Capacities of Thermally Treated Na 2 0-3B 2 0 3 Glasses Above and Below T g | | | | Abstract
| Various contributions have been obtained from the heat capacities of "as quenched" and annealed Na 2 0-3 B 2 0 3 glasses. It is shown that the enthalpic release gives a major contribution to the DSC curves obtained by reheating quenched glasses. Different relaxation processes are followed by comparing DSC scans of quenched and annealed samples in the vitreous state and around the glass transition temperature, 7^. As a function of the annealing time at T = T g — 30 "C, the specific heats at room temperature initially increase, due to the decrease of the exothermic contribution from quenched-in defects, which are absent in a fully annealed glass; over a month-long time scale these heat capacities drop, due to a partial ordering, which decreases the configurational contribution. Such a decrease is related with the "overshoot" which occurs above and which attains a limiting value AH g s 14 J moP 1 in a matter of days. The heat capacities above T g relax towards a value of C P of = 2.3 J mol" 1 K~ 1 after a few days of annealing, which is intermediate between the anomalously low C P (~ 1.8 J mol" 1 K _1) of a fast quenched (~10 3 Kmin _1) and that (~2.9J mol" 1 K" 1) of a sample annealed for one hour. These phenomena point to complex relationships among enthalpic relaxation, entropic relaxation and temperature in these glasses. | | | |
Reference
| Z. Naturforsch. 51a, 187—191 (1996); received January 11 1996 | | | |
Published
| 1996 | | | |
Keywords
| Glasses, borates, structural relaxation, annealing | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0187.pdf | | | | Identifier
| ZNA-1996-51a-0187 | | | | Volume
| 51 | |
| 30 | Author
| Pao-Hwa Chou, Isao Okada | Requires cookie* | | | Title
| Internal Cation Mobilities in the Molten Binary System (Ag, T1)N0 3 | | | | Abstract
| Internal mobility ratios in the molten binary system (Ag, T1)N0 3 have been measured by Klemm's countercurrent electromigration method. In the usual way the internal cation mobilities b have been calculated from these data and those available on the densities and conductivities. In the investigated region of temperature and composition ft Ag is greater than b Ti . | | | |
Reference
| Z. Naturforsch. 51a, 197—199 (1996); received November 27 1995 | | | |
Published
| 1996 | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0197.pdf | | | | Identifier
| ZNA-1996-51a-0197 | | | | Volume
| 51 | |
| 31 | Author
| G. Winnewisser, S. P. Belov, Th Klaus, S. Urban | Requires cookie* | | | Title
| Ro-inversional Spectrum of Ammonia | | | | Abstract
| The ground state 7 = 2— 1,^ = 0 and K -1 ro-inversional spectrum of l4 NH 3 and l5 NH 3 at 1.2 THz has been measured with an accuracy of 20 kHz using the Cologne terahertz spectrometer. The measured frequencies for the K = 0 components are: | | | |
Reference
| Z. Naturforsch. 51a, 200—206 (1996); received February 24. 1996 | | | |
Published
| 1996 | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0200.pdf | | | | Identifier
| ZNA-1996-51a-0200 | | | | Volume
| 51 | |
| 32 | Author
| Jürgen Preusser, Manfred Winnewisser | Requires cookie* | | | Title
| Nuclear Quadrupole Hyperfine Structure of the Direct /-Type Transitions of the Fulminic Acid Isotopomers H 12 C 14 N 16 0 and H 13 C 14 N 16 0 | | | | Abstract
| The direct I-type transitions of H l3 C ,4 N l6 0 in the vibrational states (i^i's) = (01) and (03) were measured in the frequency range from 18 to 40 GHz. These transitions show a nuclear quadrupole hyperfine structure caused by the l4 N nucleus, which could partially be resolved at Doppler-limited resolution. The analogous transitions of the parent species. H l2 C l4 N 16 0, were remeasured. They displayed a very similar hyperfine structure, also partially resolved. The hyperfine patterns of both H l2 C l4 N l6 0 and H 13 C 14 N 16 0 were analysed by means of contour fitting s to the absorption profiles. The parameter l^eQq, which is responsible for the splittings, is determined to be 645(20) kHz for the vibrational state (01) and 890(44) kHz for the vibrational state (03) for H l2 C l4 N l6 0 and 642(32) kHz for (01) and 898(22) kHz for (03) for H 13 C l4 N 16 0. This unexpectedly large splitting parameter for states involving the large amplitude motion (HCN bending) is discussed as another consequence of the quasilinearity of fulminic acid, in view of the fact that the analogous transitions for the vibrational state (10) (NCO bending) do not split or even show a significant line broadening at the resolution used for the present measurements. | | | |
Reference
| Z. Naturforsch. 51a, 207—214 (1996); received February 17. 1996 | | | |
Published
| 1996 | | | |
Keywords
| Nuclear quadrupole hyperfine structure, quasilinear molecule, microwave spectroscopy | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0207.pdf | | | | Identifier
| ZNA-1996-51a-0207 | | | | Volume
| 51 | |
| 34 | Author
| Jan Wiersig, PeterH. Richter | Requires cookie* | | | Title
| Energy Surfaces of Ellipsoidal Billiards | | | | Abstract
| Energy surfaces in the space of action variables are calculated and graphically presented for general triaxial ellipsoidal billiards. As was demonstrated by Jacobi in 1838, the system may be integrated in terms of hyperelliptic functions. The actual computation, however, has never been done. It is found that generic energy surfaces consist of seven pieces, representing topologically different types of invariant tori. The character of the corresponding motion is discussed. Frequen-cies, winding numbers, and the location of resonances are also determined. The results may serve as a basis for perturbation theory of slightly modified systems, and for semi-classical quantization. | | | |
Reference
| Z. Naturforsch. 51a, 219—241 (1996); received March 14 1996 | | | |
Published
| 1996 | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0219.pdf | | | | Identifier
| ZNA-1996-51a-0219 | | | | Volume
| 51 | |
| 35 | Author
| Fevzi Köksal, Fatih Ucun, İbrahim Kartal | Requires cookie* | | | Title
| EPR Study of Cr 5 + and Cu 2 + in Some Zeolites Introduced by Solid-and Liquid-State Reactions | | | | Abstract
| This study reports on the EPR of Cr 5+ and Cu 2+ ions, introduced by solid-and liquid-state reactions with the synthetic zeolites 3A, 4A and 5A, and the natural zeolite clinoptilolite. Cr 3+ was oxidized to Cr 5 + in the samples, the coordination around Cr 5 + being square pyramidal. Super-hyperfine (shf) interaction of Cr with 27 A1 nucleus was observed in both solid-and liquid-state-introduced 5A zeolite, whereas this shf could not be observed for the solid-state introduced 4A zeolite. The liquid-state Cr-introduced 4A zeolite needed a heat treatment at 473 K for Vi h for the appearance of shfs. Furthermore, it has been found that the coordination structure around the Cu 2 + is square pyramidal in solid-state introduced samples, whereas it is octahedral in the liquid-state introduced ones. | | | |
Reference
| Z. Naturforsch. 51a, 242—244 (1996); received January 8 1996 | | | |
Published
| 1996 | | | |
Keywords
| EPR, Cu 2 +, Cr 5 +, Zeolites, Ion introduction | | | |
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| | | | | TEI-XML for
| default:Reihe_A/51/ZNA-1996-51a-0242.pdf | | | | Identifier
| ZNA-1996-51a-0242 | | | | Volume
| 51 | |
| 36 | Author
| Geetha Jayaram, V. G. Krishnan | Requires cookie* | | | Title
| EPR of V0 2+ in ZnTiF 6 * 6H 2 0 | | | | Abstract
| Electron Paramagnetic Resonance (EPR) studies have been carried out on the vanadyl (VO 2) ion doped in single crystals of ZnTiF 6 • 6 H 2 0. The spectra indicate the presence of one set of eight lines characteristic of only one occupation site. The V-O bond orientation is along one of the three Zn-H 2 0 bond directions in the trigonally distorted [Zn(H 2 0) 6 ] octahedra. This behaviour is unlike that reported for vanadyl ion substituting for the M(H 2 0) 6 sites in the Tutton salts, alums and A1C1 3 • 6H 2 0. The Spin-Hamiltonian and bonding parameters for the [V0(H 2 0) 5 ] complex have been evaluated. The hyperfine linewidths are 0.8 mT at 300 K and 77 K. No proton superhyperfine structure was observed at both these temperatures. | | | |
Reference
| Z. Naturforsch. 51a, 245—248 (1996); received November 16 1995 | | | |
Published
| 1996 | | | |
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| | | | | TEI-XML for
| default:Reihe_A/51/ZNA-1996-51a-0245.pdf | | | | Identifier
| ZNA-1996-51a-0245 | | | | Volume
| 51 | |
| 37 | Author
| Gerhard Taubmann | Requires cookie* | | | Title
| Calculation of the Partition Function of a Double Minimum Oscillator from a Modified Variation Perturbation Method | | | | Abstract
| The partition function of a double minimum oscillator is evaluated by means of variation perturbation theory. For low temperatures, the method cannot be applied in the usual way. Even for a symmetric double minimum potential VDM(-C), the shift of the harmonic reference oscillator is not always zero as expected, but its minimum is near one of the minima of VDM(^) at low temperatures. The partition function thus calculated is only half the correct value. For sufficiently high temperature, the method works normally. The anomaly in the low temperature region is investigated in detail, and a modification of the variation perturbation method is suggested which eliminates most of the problems. | | | |
Reference
| Z. Naturforsch. 51a, 249—256 (1996); received September 29 1995 | | | |
Published
| 1996 | | | |
Keywords
| partition function, double minimum oscillator, inversion modes, variation perturbation theory, Pitzer-Gwinn method | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0249.pdf | | | | Identifier
| ZNA-1996-51a-0249 | | | | Volume
| 51 | |
| 39 | Author
| V. Massarotti, M. Bini, D. Capsoni | Requires cookie* | | | Title
| Structural and Defect Study of LiMn 2 0 4 Formation | | | | Abstract
| The LiMn 2 0 4 formation from MnO and Li 2 C0 3 mixtures with lithium cationic fraction 0.31 < x < 0.40 was studied by structural profile refinement from X-ray data, thermal (TGA and DSC) measurements and scanning electron microscopy (SEM) observations. Quantitative phase analysis, structural and microstructural parameters and composition of the coexisting phases were obtained. Different behaviours were observed in the composition ranges 0.33 < x < 0.35 and x > 0.37. In the former range only the stoichiometric spinel phase was obtained, in the latter, in addition to the Li 2 Mn0 3 compound, two spinel phases could be considered: I) LiMn 2 0 4 stoichiometric spinel; II) Li i +> Mn2-> .04 (0.11 < y < 0.23), a non-stoichiometric phase whose small particle size resulted practically independent of the initial composition and annealing temperature. Such a conclusion was supported also by SEM observations. The relative abundance of phase II increased with increasing lithium content and with decreasing temperature. | | | |
Reference
| Z. Naturforsch. 51a, 267—276 (1996); received March 3 1996 | | | |
Published
| 1996 | | | |
Keywords
| Solid state reaction, Lithium Manganese Spinel, Structural and microstructural parameters, Non-stoichiometry, Substitutional defects | | | |
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| | | | | TEI-XML for
| default:Reihe_A/51/ZNA-1996-51a-0267.pdf | | | | Identifier
| ZNA-1996-51a-0267 | | | | Volume
| 51 | |
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