Published by De Gruyter

Volume 56 Issue 11

Issue of Zeitschrift für Naturforschung A

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Open Access June 2, 2014

Quantum Effect on Collisions in Electron-positron Plasmas

Young-Dae Jung

Page range: 713-716

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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.

Open Access June 2, 2014

Structure and Binding of Ionic Clusters in Th and Zr Chloride Melts

Z. Akdeniz, M. P. Tosi

Page range: 717-720

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Abstract

We discuss microscopic ionic models for the structure and the binding of small clusters which may exist as structural units in molten ThCl 4 and ZrCl 4 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 ThCl 4 than for ZrCl 4 , 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 ZrCl 4 against a structure including charged oligomers in molten ThCl 4 .

Open Access June 2, 2014

Structure of Rare-earth/Alkali Halide Complexes

Z. Akdeniz, Z. Çiçek Önem, M. P. Tosia

Page range: 721-724

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Abstract

Vapour complex formation of rare-earth halides with alkali halides strongly increases the volatility 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 MRX 4 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 MRX 4 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.

Open Access June 2, 2014

The Interactions between Ta-Nb Ferroalloys and Sulfate-carbonate Melts

V. Chumarev, S. Krasikov, M. Timofeev, O. Savushkina, V. Maryevich

Page range: 725-729

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Abstract

The reactions of pure metals Ta, Nb, V, Fe, Si, etc. and Ta-Nb-containing ferroalloys with sodium (calcium) sulfate (carbonate) melts are characterized by large exothermic effects and formation of solid, liquid and gaseous products. The liquid phases formed reduce diffusion restrictions and result in catastrophically large rates of metal oxidation.

Open Access June 2, 2014

Molecular Organization in a Nematogen: PBPCN -A Computational Analysis Based on Quantum Mechanics

Durga Prasad Ojha, Devesh Kumar, V. G. K. M. Pisipati

Page range: 730-734

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Abstract

A computational analysis has been carried out to determine the configurational preference of a pair of 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 of 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 of experimental as well as other theoretical observations.

Open Access June 2, 2014

Current Efficiency Obtained with SnO₂-based Inert Anodes in Laboratory Aluminium Cell

Ana-Maria Popescu

Page range: 735-738

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Abstract

A systematic study of the current efficiency (CE) in a laboratory aluminium cell with SnO 2 -based inert anodes was carried out by measuring the overall amount of oxygen relieved at the anode, using two different methods. Inert ceramic anodes of 96% SnO 2 , 2% Sb 2 O 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.

Open Access June 2, 2014

Electrochemical Synthesis of Titanium Silicides from Molten Salts

S. V. Devyatkin, O. I. Boiko, N. N. Uskova, G. Kaptay

Page range: 739-740

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Abstract

Presented at the NATO Advanced Study Institute, Kas, Turkey, May 4 -14, 2001. Electrochemical synthesis of titanium silicides from chloro-fluoride melts has been investigated by thermodynamic calculation, voltammetry and electrolysis. The electrochemical synthesis of four titanium silicides (TiSi 2 , TiSi, Ti 5 Si 4 , Ti 5 Si 3 ) was to be a one-step process, the stoichiometry of the deposited silicides being correlated with the concentration of Si and Ti ions in the melt.

Open Access June 2, 2014

Electrochemical and Thermodynamic Properties of EuCl₃ and EuCl₂ in an Equimolar NaCl-KCl Melt

S. A. Kuznetsov, L. Rycerz, M. Gaune-Escard

Page range: 741-750

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Abstract

The electroreduction of EuCl 3 in an equimolar NaCl-KCl mixture was studied at 973 -1123 K by different electrochemical methods. This reduction of Eu(III) in NaCl-KCl melt occurs via two successive reversible steps involving transfer of one and two electrons. The diffusion coefficients of Eu(III) and Eu(II) were measured by linear sweep voltammetry and chronopotentiometry. The values found by these methods are in a good agreement. The standard rate constants for the redox reaction Eu(III) + e~ Eu(II) were calculated from cyclic voltammetry data. The sluggish kinetics of this reaction is discussed in terms of substantial rearrangement of the europium coordination sphere. Special attention was paid to the choice of working electrodes for the study of electrode reactions. The formal standard potentials E*E u (^ /Ba, E* eU (hr/eu and the formal redox potentials ^*Eu(ni)/Eu(ii) were determined from open-circuit potentiometry and linear sweep voltammetry data. The free Gibbs energy changes for the reaction EuCl 3(so1) EuCl 2(SOi.) + 1/2 Cl 2(g.) and the equilibrium constants of the metal-salt reaction 2Eu(III) + Eu 3 Eu(II) were calculated. The thermodynamics of the formation of dilute solutions of europium di-and trichloride in an equimolar NaCl-KCl melt were determined. It was shown that electrochemical transient techniques give the possibility of the determination of the relative partial molar mixing enthalpy of europium trichloride and dichloride in NaCl-KCl melt.

Open Access June 2, 2014

The Electrical Conductivity of Molten (Ag, Cd_1/2)Br

Alina Wojakowska, Agata Gòrniak

Page range: 751-753

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Abstract

The electrical conductivity of molten (Ag, Cd 1/2 )Br has been determined as a function of temperature in the whole range of compositions. The resulting activation energy values and the conductivity isotherm at 850 K are compared with those of the system (Ag, Cd 1/2 )Cl.

Open Access June 2, 2014

Redox Potentials of Samarium and Europium in Molten Lithium Chloride

Alena Novoselova, Vladimir Shishkin, Vladimir Khokhlov

Page range: 754-756

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Abstract

The samarium (III)/(II) and europium (III)/(II) redox potentials in molten lithium chloride were measured using the direct potentiometric method in the temperature range from 923 to 1094 K. Glassy carbon was used as the indifferent working electrode, and the standard chlorine electrode as a reference. The total concentration of rare-earth chlorides dissolved in molten lithium chloride did not exceed 4.5 mol%.

Open Access June 2, 2014

Calculation of the CD Spectrum of Class A β-Lactamase from Escherichia coli (TEM-1)

C. Christov, S. Gabriel, B. Atanasov, J. Fleischhauer

Page range: 757-760

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Abstract

The Circular Dichroism (CD) spectrum of β-lactamase from Escherichia coli (TEM-1) has been calculated with the matrix method on the basis of the x-ray diffraction structure. All known transitions in the peptide and side-chain groups, especially the aromatic and disulfide groups have been included. The calculations were performed with and without the tryptophan (Trp) residues. Rotational strengths calculated with the matrix method were combined with Gaussians to generate the CD spectrum. The calculated spectrum reproduces the signs and approximate magnitudes of the CD bands rather w ell only when the trytophan side chains are included. However, the experimental negative double band at 208 and 222 nm, which is characteristic for a-helices, is absent in the calculated spectrum.

Open Access June 2, 2014

The Polysurface Mechanism of Ta and Ti Anodic Dissolution in Low-Temperature Carbamide-NH₄CL Melt

S. Volkov, N. Tumanova, S. Kothetova, N. Buryak

Page range: 761-763

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Abstract

In this work the peculiarities of the electrochemical dissolution of tantalum and titanium in carbamide containing low temperature melts were studied.

Open Access June 2, 2014

Pressure Dependence of the Chlorine NQR in Three Solid Chloro Anisoles

K. S. Suresh, K. P. Ramesh, C. Raghavendra Rao, J. Ramakrishna

Page range: 764-772

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Abstract

The 35 C1 Nuclear Quadrupole Resonance (NQR) frequency (V Q ) and spin lattice relaxation time (T 1 ) in the three anisoles 2,3,4-trichloroanisole, 2,3,6-trichloroanisole and 3,5-dichloroanisole have been measured as a function of pressure upto 5.1 kbar at 300 K, and the data have been analysed to estimate the temperature coefficients of the NQR frequency at constant volume. All the three com pounds show a non linear variation of the NQR frequency with pressure, the rate of which is positive and decreases with increasing pressure. In case of 3,5-dichloroanisole the value becomes negative in the higher range of pressure studied. The spin lattice relaxation time T 1 in all the three compounds shows a weak dependence on pressure, indicating that the relaxation is mainly due to the torsional motions.

Open Access June 2, 2014

Structural Investigation of Vanadium-Sodium Metaphosphate Glasses

A. Chrissanthopoulos, C. Pouchan, G. N. Papatheodorou

Page range: 773-776

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Abstract

Paper presented a t the NATO A dvanced Study Institute, May 4-1 4 , 2001 (Kas, Turkey) The structure of the glass forming system (V 2 O 5 )x -(Na 2 O • P 2 O 5 ) (1-x) , (x = 0-0.4), has been inves tigated using Raman spectroscopy. The stretching vibrations of various phosphate groups, connected to phosphorus or vanadium atoms, have been assigned. Variation of the composition leads to structural changes where the sodium metaphosphate -P-O-P-chains break and then reconnect with the oxovana-dium units forming a -V-O-P-network structure.

Open Access June 2, 2014

Relaxation of ¹²¹Sb NQR in Antimony Trichloride due to Raman Process

Noriaki Okubo, Mutsuo Igarashi

Page range: 777-784

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Abstract

The spin-lattice relaxation times of 121 Sb nuclear quadrupole resonance in SbCl 3 have been measured from 4.2 K to the m. p., 346 K. The result is analyzed with a theory of the Raman process based on co valency and discussed in comparison with the previous result for Cl nuclei.

Open Access June 2, 2014

A Dielectric Relaxation Study of Diethylsulfoxide/ Tetrachloromethane Binary Mixtures

S. A. Markarian, A. S. Galstian, M. Stockhausen

Page range: 785-787

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Abstract

The dielectric spectra of diethylsulfoxide (DESO)/tetrachloromethane mixtures have been measured from 0.5 to 72 GHz at 20 °C. On the basis of the relation between the relaxation time and the DESO concentration a complex formation between DESO and tetrachloromethane is suggested.

Open Access June 2, 2014

Erratum

Page range: 788-788

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About this journal

Objective
A Journal of Physical Sciences: Zeitschrift für Naturforschung A (ZNA) is an international scientific journal which publishes original research papers from all areas of experimental and theoretical physics. Authors are encouraged to pay particular attention to a clear exposition of their respective subject, addressing a wide readership. In accordance with the name of our journal, which means “Journal for Natural Sciences”, manuscripts submitted to ZNA should have a tangible connection to actual physical phenomena. In particular, we welcome experiment-oriented contributions.

Manuscripts considered for publication in A Journal of Physical Sciences: Zeitschrift für Naturforschung A undergo high-level refereeing. Mere formal correctness of a paper is not sufficient for its acceptance. Moreover, articles reporting a merely marginal extension of already existing knowledge are considered unsatisfactory. Instead, the key quality a publication in A Journal of Physical Sciences: Zeitschrift für Naturforschung A should possess is that it makes a genuine contribution to the advancement of its topic.

Topics

Atomic, Molecular & Chemical Physics
Dynamical Systems & Nonlinear Phenomena
Gravitation & Cosmology
Hydrodynamics
Quantum Theory
Solid State Physics & Materials Science
Thermodynamics & Statistical Physics

Article formats
Original research articles, research notes, letters and review articles from all areas of theoretical and experimental physics

Information on submission process

Volume 56 Issue 11

Issue of Zeitschrift für Naturforschung A

Quantum Effect on Collisions in Electron-positron Plasmas

Abstract

Structure and Binding of Ionic Clusters in Th and Zr Chloride Melts

Abstract

Structure of Rare-earth/Alkali Halide Complexes

Abstract

The Interactions between Ta-Nb Ferroalloys and Sulfate-carbonate Melts

Abstract

Molecular Organization in a Nematogen: PBPCN -A Computational Analysis Based on Quantum Mechanics

Abstract

Current Efficiency Obtained with SnO2-based Inert Anodes in Laboratory Aluminium Cell

Abstract

Electrochemical Synthesis of Titanium Silicides from Molten Salts

Abstract

Electrochemical and Thermodynamic Properties of EuCl3 and EuCl2 in an Equimolar NaCl-KCl Melt

Abstract

The Electrical Conductivity of Molten (Ag, Cd1/2)Br

Abstract

Redox Potentials of Samarium and Europium in Molten Lithium Chloride

Abstract

Calculation of the CD Spectrum of Class A β-Lactamase from Escherichia coli (TEM-1)

Abstract

The Polysurface Mechanism of Ta and Ti Anodic Dissolution in Low-Temperature Carbamide-NH4CL Melt

Abstract

Pressure Dependence of the Chlorine NQR in Three Solid Chloro Anisoles

Abstract

Structural Investigation of Vanadium-Sodium Metaphosphate Glasses

Abstract

Relaxation of 121Sb NQR in Antimony Trichloride due to Raman Process

Abstract

A Dielectric Relaxation Study of Diethylsulfoxide/ Tetrachloromethane Binary Mixtures

Abstract

Erratum

Current Efficiency Obtained with SnO₂-based Inert Anodes in Laboratory Aluminium Cell

Electrochemical and Thermodynamic Properties of EuCl₃ and EuCl₂ in an Equimolar NaCl-KCl Melt

The Electrical Conductivity of Molten (Ag, Cd_1/2)Br

The Polysurface Mechanism of Ta and Ti Anodic Dissolution in Low-Temperature Carbamide-NH₄CL Melt

Relaxation of ¹²¹Sb NQR in Antimony Trichloride due to Raman Process