| 101 | Author
| Hideta Ishihara, Toshiya Okajima, Keizo Horiuchia, Ingrid Svobodab, Hartmut Fuessb | Requires cookie* | | Title
| Isolated versus Condensed Anion Structure VII: X-ray Structure Analysis of 1,3-Propanediammonium Dibromodichlorocadmate(II), [H3N(CH2)3NH3]CdBr2Cl2, and Estimation of Stability of Five-coordinated Halide Anions, MXg3-(M = Cd, Zn; X = Cl, Br) by Means of Ab-initio MO Calculations  | | | Abstract
| The coordination capability of Cl and Br in halogenocadmate(II) complexes is estimated by a solution of the structure of 1,3-propanediammonium dibromodichlorocadmate(II). The compound crystallizes as a layered anion structure with Cl bridges and Br terminals at 293 K: Imma, a = 741.56(7), b = 1869.5(5), and c -771.55(8) pm, Z = 4. In order to explain the stronger tendency of halogenocadmate(II) complexes to form layered structures as compared to halogenozincate(II), ab-initio calculations were performed. The stability of MX53-(M = Cd, Zn; X = Cl, Br) is compared. Isolated ZnX53-and CdBr53-ions are not stable. On the other hand a trigonal bipyramid CdCl53-ion is considered to be subtly stable in the crystal mainly due to Coulomb attractive interactions between the positively charged metal cation Cd2+ in a CdCl3 " fragment and two Cl-ions. | | |
Reference
| Z. Naturforsch. 56a, 641—646 (2001); received June 16 2001 | | |
Published
| 2001 | | |
Keywords
| Crystal Structure, Halogenocadmate(II), Ab-initio MO Calculations | | |
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| default:Reihe_A/56/ZNA-2001-56a-0641.pdf | | | Identifier
| ZNA-2001-56a-0641 | | | Volume
| 56 | |
102 | Author
| F. Da Silva3, L. Rycerza, M. Gaune-Escard3 | Requires cookie* | | Title
| Thermodynamic Properties of EuC12 and the NaCl-EuCl2 System  | | | Abstract
| The temperature and enthalpy of the phase transition and fusion of EuC12 were determined and found to be 1014 K, 11.5 kJ mol-and 1125 K, 18.7 kJ mol-1 , respectively. Addition ally, the heat capacity of solid EuC12 was measured by Differential Scanning Calorimetry in the temperature range 306 -1085 K. The results were fitted to the linear equation C^ m = (68.27 + 0.0255 T/K) J m ol-1 K-1 in the temperature range 306 -900 K. Due to discrepancies in the liter ature on the temperature of fusion of EuC12, the determination of the NaCl-EuCl2 phase diagram was repeated. It consists of a simple eutectic equilibrium at Tem = 847 K with x(EuCl2) = 0.49. | | |
Reference
| Z. Naturforsch. 56a, 647—652 (2001); received August 1 2001 | | |
Published
| 2001 | | |
Keywords
| Europium Dichloride, Sodium Chloride, Phase Diagram, Enthalpy of Transition, Heat Capacity | | |
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| default:Reihe_A/56/ZNA-2001-56a-0647.pdf | | | Identifier
| ZNA-2001-56a-0647 | | | Volume
| 56 | |
103 | Author
| F. Da Silva3, L. Rycerz3, M. Gaune-Escard3 | Requires cookie* | | Title
| Calorimetric Investigation of MC1-EuCI2 Melts (M = Na, K, Rb)  | | | Abstract
| The molar enthalpies of mixing (A mixH m) of MCl-EuCl2 (M = Na, K, Rb) liquid binary systems were measured at 1138 K over the whole composition range by direct calorimetry. A Calvet type calorimeter was used, and mixing of the two liquid components was achieved by the ampoule break-off technique under argon at atmospheric pressure. The enthalpy of mixing of these systems is negative over the whole composition range with a minimum of approximately -0.5, -3.5 and -4.5 kJ mol-1 for M = Na, K, Rb, respectively. The least-squares coefficients A, B, C in the equation A (kJ mol-1) = A + B x + C x 2, where A is an interaction parameter, are reported. From the trend observed in these MCl-EuCl2 systems it was possible to estimate the mixing enthalpy of the CsCl-EuCl2 system. In tro d u c tio n | | |
Reference
| Z. Naturforsch. 56a, 653—657 (2001); received August 1 2001 | | |
Published
| 2001 | | |
Keywords
| Mixing Enthalpy, Europium Dichloride, Alkali Chlorides, Calvet Calorimeter | | |
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| default:Reihe_A/56/ZNA-2001-56a-0653.pdf | | | Identifier
| ZNA-2001-56a-0653 | | | Volume
| 56 | |
104 | Author
| Albert Würflinger, M. Massalska-Arodż3, S. Urbanb, W. Weissflogc, S. Emstc | Requires cookie* | | Title
| Thermodynamic Measurements on the Binary System Bis{[2,2-di(w- hexyloxycarbonyl)ethenyl]phenyl} Biphenyl-4,4'-dicarboxylate and 4-w-Octyloxyphenyl 4-/i-Pentyloxybenzoate at Elevated Pressures  | | | Abstract
| Thermodynamic measurements have been carried out on the binary system of a swallow-tailed liquid crystal A = bis{[2,2-di(n-hexyloxycarbonyl)ethenyl]phenyl} biphenyl-4,4'-dicarboxylate (4DS6) and B = 4-n-octyloxyphenyl 4-rc-pentyloxybenzoate (5 0 /0 8). A filled smectic A phase is induced in the concentration range 0.11 < xA < 0.75. The maximum of the SmA-N transition temperature (365 K) is observed for xA = 0.33. Dilatometric measurements show that the packing density in the filled phases is increased. High-pressure DTA is employed in order to investigate the coexistence range of the liquid crystalline phases and the slopes of the transition lines. The slopes of the melting curves for the mixtures are significantly smaller than those for the pure components. The slopes for the smectic -nematic -isotropic transitions are considerably larger. The coexistence range for the (smectic + nematic) phases does not seem to be pressure-limited, rather it increases with pressure. | | |
Reference
| Z. Naturforsch. 56a, 658—662 (2001); received July 18 2001 | | |
Published
| 2001 | | |
Keywords
| Phase Transitions, DTA, High Pressure, Swallow-tailed Liquid Crystals | | |
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| default:Reihe_A/56/ZNA-2001-56a-0658.pdf | | | Identifier
| ZNA-2001-56a-0658 | | | Volume
| 56 | |
105 | Author
| HansH. Diebner3, O. Tf\, Adolf Mathias3, Horst Prehnc, Marco Rohrbacha, Sven Sahle3 | Requires cookie* | | Title
| Control and Adaptation of Spatio-temporal Patterns  | | | Abstract
| We apply a recently introduced cognitive system for dynamics recognition to a two-dimensional array of coupled oscillators. The cognitive system allows for both the control and the adaptation of spatio-temporal patterns of that array of oscillators. One array that shows Turing-pattems in a self-organizational manner is viewed as an externally presented dynamics (stimulus) which is mapped onto a mirror dynamics, whereby the latter is capable to simulate (simulus). Two of the parameters of the stimulus are thereby regarded to be unknown and have to be estimated by the cognitive system. The cognitive system itself consists of dynamical modules that are stimulated by the external dynamics in the sense of Pyragas' external force control mechanism and thereby yield measures of how good they match the stimulus. These measures are used as weights to construct the simulus. The adaptation process is performed "on the fly", i. e., without the storage of data. The proposed cognitive system, therefore, is a prominent candidate for the construction of a control device for a permanent real time observation of an external dynamical system in order to interfere instantaneously when necessary. | | |
Reference
| Z. Naturforsch. 56a, 663—669 (2001); received August 21 2001 | | |
Published
| 2001 | | |
Keywords
| Adaptive Systems, Cognitive Systems, Pattern Formation, Brain Dynamics, Force Control | | |
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| default:Reihe_A/56/ZNA-2001-56a-0663.pdf | | | Identifier
| ZNA-2001-56a-0663 | | | Volume
| 56 | |
106 | Author
| Hsin-Yi Hsu, Chao-Cheng Yang | Requires cookie* | | Title
| Conductivities of Room Temperature Molten Salts Containing AICI3, Measured by a Computerized Direct Current Method  | | | Abstract
| The conductivities of the binary room-temperature molten salt systems AlCl3-yV-«-butylpyridinium chloride (BPC), AlCl3-l-ethyl-3-methylimidazolium chloride (EMIC) and AlCl3-benzyltriethylammo-nium chloride (BTEAC) have been measured at different temperatures and compositions by a d.c. four-probes method. There is a maximum of the conductivity at 50 mol% A1C13 in the A1C13-BPC and A1C13-EMIC systems at 40 to 80 °C, their activation energies being relatively low (20.79 and 14.76 kJ/mol, respec tively). As to the A1C13-BTEAC system, there is an irregular change in the conductivity at 40-70 mol% A1C13 in the temperature range 50 to 80 °C. The conductivities of the three RTMS are in the order A1C13-EMIC > A1C13-BPC > A1C13-BTEAC, the reason being discussed. | | |
Reference
| Z. Naturforsch. 56a, 670—676 (2001); received July 23 2001 | | |
Published
| 2001 | | |
Keywords
| Conductivity, Room-temperature Molten Salts, Activation Energy, Direct Current Method, Computerized Measurement System | | |
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| default:Reihe_A/56/ZNA-2001-56a-0670.pdf | | | Identifier
| ZNA-2001-56a-0670 | | | Volume
| 56 | |
107 | Author
| M. M. Ahmad, M. A. Hefnia | Requires cookie* | | Title
| Effect of Li Content on the DSC and Electrical Conductivity of (Li1_J C Kx)2S 0 4 Mixed Crystals  | | | Abstract
| Differential scanning calorimetry on (Li1_J(K (.)2S 04 mixed crystals, where x = 0.01, 0.1, 0.3 and 0.5, revealed that, as the potassium content increases, the first high temperature phase of the intermediate LiKS04 phase at T -432 °C grows and shifts to higher temperature, and a double-phase mixture con sisting of LiKS04 and Li2S 04 exists for x< 0.5. Ionic conductivity measurements on (Li|_xK;t)2S 04 mixed crystals for x < 0.5 did show that the electrical conductivity increases as the Li2S 04 concentra tion increases, with an average activation energy of 0.9 eV. The enhanced electrical conductivity is pri marily a result of the increase in the Li+ ion (charge carriers) concentration and/or the formation of a diffuse space charge layer at the interface between the two phases. | | |
Reference
| Z. Naturforsch. 56a, 677—680 (2001) | | |
Published
| 2001 | | |
Keywords
| (Li)_^KJ()2S 04 Crystals, DSC, Ionic Conductivity, Diffuse Space Charge Layer | | |
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| default:Reihe_A/56/ZNA-2001-56a-0677.pdf | | | Identifier
| ZNA-2001-56a-0677 | | | Volume
| 56 | |
108 | Author
| F. W. Interberg | Requires cookie* | | Title
| The Value of Sommerfeld's Finestructure Constant as a Consequence of the Planck-Aether Hypothesis  | | | Abstract
| A value of the finestructure constant at the unification eneigy is obtained by a dimensional analysis of quantum gravity and fluid dynamics. The derivation assumes that the vacuum is a superfluid made up of positive and negative Planck mass particles obeying an exactly nonrelativistic law of motion with Lorentz invariance a low energy approximation. The dimensional analysis presented gives a value for the finestructure constant in good agreement with the empirical value 1 la = 25. | | |
Reference
| Z. Naturforsch. 56a, 681—684 (2001); received July 16 2001 | | |
Published
| 2001 | | |
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| default:Reihe_A/56/ZNA-2001-56a-0681.pdf | | | Identifier
| ZNA-2001-56a-0681 | | | Volume
| 56 | |
109 | Author
| M. Srinivasulu, P.V V Satyanarayana, P. A. Kumar3, V.G K M Pisipatia | Requires cookie* | | Title
| Induced Smectic-G Phase through Intermolecular Hydrogen Bonding Part VIII: Phase and Crystallization Behaviours of 2-(p-/i-heptyloxybenzyIidene imino)-5-chIoro-pyridine: p-n-alkoxybenzoic acid (HICP:n ABA) Complexes  | | | Abstract
| New intermolecular H-bonded liquid crystalline complexes, viz., 2-(p-n-heptyloxybenzylidene imi-no)-5-chloro-pyridine:p-/z-alkoxybenzoic acid; (HICP:nABA) (where n denotes the alkoxy carbon num bers 3 to 10 and 12) exhibiting smectic-F (n = 12) and smectic-G phases have been synthesized and char acterized by Thermal Microscopy and Differential Scanning Calorimetry (DSC). Detailed IR (solid and solution states) analysis confirms the existence of intermolecular H-bonding between the pyridyl nitro gen and the COOH group of the p-n-alkoxybenzoic acid moiety. The phase behaviour of the series is discussed in the light of reported data on free p-n-alkoxybenzoic acids. The crystallization kinetics of a representative complex, using the DSC technique, is discussed. The mechanism of the crystal growth of the new crystalline smectic-G phase is computed with the Avrami equation. | | |
Reference
| Z. Naturforsch. 56a, 685—691 (2001); received June 27 2001 | | |
Published
| 2001 | | |
Keywords
| H-bonding, HICP:nABA, Crystallization Kinetics, Avrami Parameters | | |
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| default:Reihe_A/56/ZNA-2001-56a-0685.pdf | | | Identifier
| ZNA-2001-56a-0685 | | | Volume
| 56 | |
111 | Author
| G. D. Zissia, C. Bessada3 | Requires cookie* | | Title
| 27A1 NMR Spectra of the REC13-A1C13 (RE = Y, La) Glasses and Melts  | | | Abstract
| 27 AI NMR spectra of pure crystalline and molten A1C13 and of RECI3-AICI3 (RE = Y, La) glass form ing binary mixtures have been obtained. Compositions corresponding mainly to YC13/A1C13 = 1/3 and LaCiyAlC^ = 1/3.7 have been studied from the glassy and crystalline state up to the melt. The 27A1 spectra can be unambiguously assigned to four-coordinated Al-species, such as A12C16, 'A1C14', and 'A12C17\ The chemical shifts lie between 95 and 110 ppm, very well separated with the -1.6 ppm giv en by the 'A1C16' coordination in solid A1C13. From the temperature evolution of the 27Al NMR spec tra, a description for the dynamic behaviour of these systems is proposed. | | |
Reference
| Z. Naturforsch. 56a, 697—701 (2001) | | |
Published
| 2001 | | |
Keywords
| 27A1 MAS NMR, REC13-A1C13, Glass Forming Melts, Structure, Dynamics | | |
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| default:Reihe_A/56/ZNA-2001-56a-0697.pdf | | | Identifier
| ZNA-2001-56a-0697 | | | Volume
| 56 | |
115 | Author
| Young-Dae Jung | Requires cookie* | | Title
| Quantum Effect on Collisions in Electron-positron Plasmas  | | | Abstract
| Quantum effects on the electron-positron scattering are investigated in electron-positron plasmas. The corrected Kelbg potential, taking into account the quantum effects, is applied to describe the electron-positron interaction potential in electron-positron plasmas. The Bom approximation is considered to obtain high-energy electron-positron scattering cross sections. The results show that the differential electron-positron scattering cross sections increase with increasing thermal de Broglie wavelength, i.e., decreasing plasma temperature. The differential electron-positron scattering cross sections decreases with increasing collision energy. It is also found that the quantum effects on the differential scattering cross section are small for forward and backward scattering angles. | | |
Reference
| Z. Naturforsch. 56a, 713—716 (2001); received May 31 2001 | | |
Published
| 2001 | | |
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| default:Reihe_A/56/ZNA-2001-56a-0713.pdf | | | Identifier
| ZNA-2001-56a-0713 | | | Volume
| 56 | |
116 | Author
| Z. Akdeniza, M. P. Tosia | Requires cookie* | | Title
| Structure and Binding of Ionic Clusters in Th and Zr Chloride Melts  | | | Abstract
| We discuss microscopic ionic models for the structure and the binding of small clusters which may exist as structural units in molten ThCl4 and ZrCl4 and in their mixtures with alkali halides according to Raman scattering studies of Photiadis and Papatheodorou. The models are adjusted to the two isolated tetrahedral molecules. Appreciably higher ionicity is found for ThCl4 than for ZrCl4, and this fact underlies the strikingly different behaviour of the two systems in the dense liquid state -in particular, a molecular-type structure for molten ZrCl4 against a structure including charged oligomers in molten ThCl4. | | |
Reference
| Z. Naturforsch. 56a, 717—720 (2001); received September 10 2001 | | |
Published
| 2001 | | |
Keywords
| Ionic Clusters, Liquid Structure, Molten Salts | | |
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| default:Reihe_A/56/ZNA-2001-56a-0717.pdf | | | Identifier
| ZNA-2001-56a-0717 | | | Volume
| 56 | |
117 | Author
| Z. Akdeniz, Z. £i£ek Önem, M. P. Tosia | Requires cookie* | | Title
| Structure of Rare-earth/Alkali Halide Complexes  | | | Abstract
| Vapour complex formation of rare-earth halides with alkali halides strongly increases the volatil ity of these compounds. We evaluate the structure taken by such complexes having the chemical formulas MRX4, M2RX5 and M3RX6, where X = F or Cl and typically M = Li or Na and R = La. The roles played by the two types of metal atom is investigated in MRX4 complexes by also taking M = K, Rb or Cs and R = Gd or Lu. The main predictions that emerge from our calculations are as follows: (i) in MRX4 a fourfold coordination of the rare-earth atom is accompanied by twofold or threefold coordination of the alkali atom, the energy difference in favour of the twofold-coordination state being about 0.3 eV in the case of the LiF complexing agent but even changing sign as the ionic radius of either the alkali or the halogen is increased; (ii) in M2RX5 a fivefold coordination of the rare-earth atom is energetically more stable than a fourfold one, by again not more than about 0.3 eV; (iii) in M3RX6 the fivefold and sixfold coordinations of the rare-earth atom are energetically competitive; and (iv) in both M2RX5 and M3RX6 each coordination state can be realized in various forms that differ in detail but are close in energy. Bond fluctuations and disorder around the rare-earth atom can be expected to be a general feature at elevated temperatures, both in the vapour and in liquid rare-earth/alkali halide mixtures. | | |
Reference
| Z. Naturforsch. 56a, 721—724 (2001); received September 13 2001 | | |
Published
| 2001 | | |
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| default:Reihe_A/56/ZNA-2001-56a-0721.pdf | | | Identifier
| ZNA-2001-56a-0721 | | | Volume
| 56 | |
119 | Author
| Prasad Durga, Devesh Ojha, V.G K M Kumar, Pisipati | Requires cookie* | | Title
| Molecular Organization in a Nematogen: PBPCN -A Computational Analysis Based on Quantum Mechanics  | | | Abstract
| A computational analysis has been carried out to determine the configurational preference of a pair o f 4'-n-pentyloxy-4-biphenylcarbonitrile (PBPCN) molecules with respect to translatory and orientational motions. The CNDO/2 method has been employed to evaluate the net atomic charge and atomic dipole components at each atomic centre of the molecule. Modified Rayleigh-Schrödinger perturbation theory along with multicentered-multipole expansion method has been employed to evaluate long-range intermolecular interactions, while a '6-exp' potential function has been assumed for short-range interactions. On the basis of stacking, in-plane and terminal interaction energy calculations, all possible geometrical arrangements o f molecular pair have been considered. It has been observed that the molecule has a strong preference for stacking through a particular face, while the other configurations, such as stacking through the other face, in-plane and terminal interactions show, in general, an aligned structure along molecular axis. The results are discussed in the light o f experimental as well as other theoretical observations. | | |
Reference
| Z. Naturforsch. 56a, 730—734 (2001); received September 7 2001 | | |
Published
| 2001 | | |
Keywords
| PBPCN, Nematogen, Interaction Energy, Computer Simulation | | |
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| default:Reihe_A/56/ZNA-2001-56a-0730.pdf | | | Identifier
| ZNA-2001-56a-0730 | | | Volume
| 56 | |
120 | Author
| Ana-Maria Popescu | Requires cookie* | | Title
| Current Efficiency Obtained with S n 02-based Inert Anodes in Laboratory Aluminium Cell  | | | Abstract
| A systematic study of the current efficiency (CE) in a laboratory aluminium cell with S n 0 2-based inert anodes was carried out by measuring the overall amount o f oxygen relieved at the anode, using two different methods. Inert ceramic anodes of 96% S n 0 2, 2% Sb20 3, 2% CuO in wt% composition were prepared and investigated. The influence of: temperature, current density, anode-cathode distance, cryolitic ratio, content of alumina and different additives was studied. At the same time the influence of the age of boron nitride (BN) sheath of the inert anode on the CE was evaluated. | | |
Reference
| Z. Naturforsch. 56a, 735—738 (2001); received August 20 2001 | | |
Published
| 2001 | | |
Keywords
| Inert Anodes, Current Efficiency, Aluminium Electrolysis, Ceramic Anodes, Molten Salts Electrolysis | | |
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| default:Reihe_A/56/ZNA-2001-56a-0735.pdf | | | Identifier
| ZNA-2001-56a-0735 | | | Volume
| 56 | |
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