bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solvent Self Diffusion Coefficients and 109Ag NMR Chemical Shifts in Silver Nitrate/Acetonitrile/Water Mixtures – Correlation with Macroscopic Transport Properties –
Authors: Wittekopf Burghard , Weiden Norbert , Weil Konrad G. 
Published: July 2012

AbstractWe used the 1H NMR spin echo technique to determine the self diffusion coefficients of acetonitrile and of water in acetonitrile/water/silver nitrate mixtures. Both diffusion coefficients decrease strongly with increasing salt concentration. By comparison with earlier determined electric conductivity and viscosity data we find, that the ratio of molar conductivity and water self diffusion coefficient is constant, as well as the product of the viscosity and the acetonitrile self diffusion coefficient. The 109Ag NMR chemical shifts in these mixtures show, that silver ions are only solvated by acetonitrile.
Photo‐Enhancement of Electrochromism in MoO3 Thin Films
Authors: Yao J. N. , Loo B. H. , Hashimoto K. , Fujishima A. 
Published: July 2012

AbstractMoO3 thin films after irradiated with a UV light showed enhancement in electrochromism when compared to the non‐irradiated ones. It was found that the change in absorbance for the irradiated portion was as large as six times that of the non‐irradiated portion of a sample. This enhancement in electrochromism may be due to the differences in the electrical conductivity and film crystallinity between the irradiated and non‐irradiated samples.
Determination of the Structure of Fluid Deuterium Chloride by Neutron Diffraction at High Pressure
Authors: Bausenwein T. , Bertagnolli H. , Tödheide K. , Chieux P. 
Published: July 2012

AbstractHigh‐pressure neutron diffraction measurements on liquid and fluid deuterium chloride are reported. Temperature and density were varied over a broad range involving pressures up to nearly 2000 bars. The employed high‐pressure equipment and the pressure cell are presented. Data evaluation up to the corrected structure factor is described. Several correction procedures for multiple scattering and self‐absorption and for inelastic scattering effects are discussed with regard to their applicability in the present case. The intramolecular structure is determined by fitting to the total differential cross section as well as to the separated intramolecular cross section. A separation of the intra‐ and the intermolecular contribution is done by means of Fourier transformation. The dependence of the intermolecular radial distribution function on temperature and density is shown.
The Absorption Spectrum of the Nitrate (NO3) Radical in Aqueous Solution
Authors: Herrmann H. , Exner M. , Zellner R. 
Published: July 2012

AbstractAbsorption coefficients for the nitrate (NO3) radical in aqueous solution have been determined using multichannel optical absorption in the range λ = 540 – 760 nm. NO3 radicals were generated by excimer laser photolysis of (NH4)2[Ce(NO3)6] at 351 nm. For the quantum yield of NO3 formation from this process a value of ϕ(NO3) = (0.85 ± 0.09) has been determined using a Br− scavenging technique. With this value the absolute absorption coefficient of NO3 at the maximum of its absorption at 635 nm was found as ϵ = (527 ± 105) l/mol · cm (base 10). Absorption coefficient data for the range 540–760 nm are presented in 2 nm intervals. The oscillator strength of the (0‐0) band transition near 665 nm has been calculated to be (1.6 ± 0.5) · 10−3 in reasonable agreement with the gas phase value.
The Influence of Unimolecular Fall‐off Behaviour on Pyrolysis Systems. A Case Study
Authors: Olzmann M. , Scherzer K. , Schwede M. 
Published: July 2012

AbstractThe influence of unimolecular fall‐off effects on the kinetic modelling of larger pyrolysis systems is estimated theoretically for the case of propane decomposition at nearly industrial conditions (1100 K, 0.1 MPa). The ordinary differential equation system based on a mechanism of 34 elementary reactions and 20 chemical species is integrated by means of a Gear algorithm two times, on the one hand with the thermal high‐pressure rate constants and on the other hand with constants corrected for the fall‐off effects in the case of unimolecular as well as in the case of bimolecular association reactions. RRKM theory, combined with an empirical treatment of weak‐collision effects, provides ratios of k/k∞ between 0.2 and 0.9. It turns out that corrections in this order of magnitude have only little influence on the concentrations of stable products, whereas radical species show, at least partly, a higher sensitivity. This results in larger deviations of the concentrations of compounds formed by radical recombination that, nevertheless, contribute to the overall products only to a small extent.
Fluoride Ion Diffusion in MSn2F5 (M+  NH4+, Rb+, Cs+) Studied by 1H and 19F Nuclear Magnetic Relaxation and Electrical Conductivity
Authors: Hirokawa Kiyofumi , Kitahara Hiroshi , Furukawa Yoshihiro , Nakamura Daiyu 
Published: July 2012

AbstractFluoride ion diffusion in NH4Sn2F5, RbSn2F5, and CsSn2F5 was investigated by measuring the electrical conductivity (σ) and nuclear magnetic relaxation times (T1, T1ϱ, and T2) of 1H and 19F nuclei. The frequency dependence of T1 (1H) shows a logarithmic divergence in the high‐temperature phase of NH4Sn2F5, indicating that the fluoride ion diffusion in this phase is two‐dimensional. In the room‐temperature phases of NH4Sn2F5 and RbSn2F5, this two‐dimensionality of the diffusion is weakened. An asymmetric T1ϱ minimum observed for NH4Sn2F5 and RbSn2F5 was analyzed using an analytical expression, τ ln {1 + (ωτ)−1‐β}, for the spectral density of the 2D fluoride ion diffusion, and the β parameter introduced explain the asymmetry of the T1ϱ minimum and a large difference between apparent activation energies deduced from T1 and T2 data. The activation energies determined from the relaxation times in the high‐temperature limit agree well with those from the σ measurements.
The Effect of Temperature on the Double Layer Dielectric Relaxation in Polystyrene Latices
Authors: Bordi F. , Cametti C. 
Published: July 2012

AbstractDielectric properties of polystyrene latices suspended in aqueous electrolyte solution (10−4 M NaCl) are investigated at different temperatures in the interval 0 to 50°C in the frequency range 1 kHz–10 MHz. where these charged colloidal systems generally display two distinct dielectric dispersions. The temperature dependence of the dielectric parameters describing the low‐frequency process is compared with predictions of some well‐established theoretical treatments based on counterion polarization models. The observed behavior is consistent with the counterion polarization at the interface with the dispersed particle when the contribution of the diffuse part of the double layer is included.
Evaluation of the Thermophysical Properties of Toluene and n‐Heptane from 180 to 320 K and up to 260 MPa from Speed‐of‐Sound Data
Authors: Sun T. F. , Bominaar S. A. R. C. , Ten Seldam C. A. , Biswas S. N. 
Published: July 2012

AbstractA number of important thermophysical properties of liquid toluene and n‐heptane have been evaluated in the temperature range form 180 to 320 K and at pressures up to 260 MPa using the previously reported speed‐of‐sound data and following a modified computational method originally developed by Davis and Gordon. The derived properties include the density, the isobaric thermal expansivity, the isothermal compressibility, the specific heat, the entropy and the enthalpy. The derived density data for the two liquids have been used to examine the validity of several empirical equations of state for liquids.
EXAFS Studies of Aqueous Solutions of Rubidium Bromide
Authors: Bertagnolli H. , Ertel T. S. , Hoffmann M. , Frahm R. 
Published: July 2012

AbstractWe report the results of extended X‐ray absorption fine structure (EXAFS) measurements performed on aqueous solutions of rubidium bromide (RbBr) at room temperature. The measurements were made at the Br and Rb K‐edges. Average Rb+–OH2, Br− – OH2 and Rb–Br distances were determined from the quantitative analysis of the EXAFS data.
The Influence of an Oxidation Step in the Adsorbed Layer on the ip vs. Sweep Rate Relationship. — A Diagnostic Criterium Based on the Linear Sweep Voltammetric Method
Authors: González J. 
Published: July 2012

AbstractA new diagnostic criterium has been deduced for an electrochemical system adsorbed which oxidizes, giving rise to a new adsorbed intermediate. The rate equations, combined with linear sweep conditions lead to ip vs. ν (sweep rate) plots, which are linear for low scan rates and tend to a limiting value at higher sweep rates. Two examples of this very frequent behaviour are given.
Crystallization of Cold Condensed Lead Chloride (PbCl2)
Authors: Zuber Ralf , Weil Konrad G. 
Published: July 2012

AbstractBy comparison of the UV spectra of freshly prepared cold condensed lead chloride films with those of tempered ones, it can be seen that initially non crystalline material is formed. The excitonic transitions give rise to broad structureless bands. Upon annealing, these bands shift and become more sharply. From the excitonic absorption at about 270 nm the non crystalline to crystalline transition can be monitored quantitatively. We can demonstrate that this is a first order phase transition. Nucleation is a necessary step. The initial non crystalline state therefore is metastable and not a frozen‐in state.
Thermodynamics of the Ternary Mixture Propan‐1‐ol + Triethylamine + n‐Heptane. Experimental Results and ERAS‐Model Calculations of HE and VE
Authors: Bender M. , Hauser J. , Heintz A. 
Published: July 2012

AbstractMolar excess enthalpies (HE) and molar excess volumes (VE) of the liquid mixture Propan‐1‐ol (PrOH) + Triethylamine (TEA) + n‐Heptane have been measured by flow calorimetry and the vibrating tube technique respectively. Data of the three binary systems have also been obtained. The excess properties are dominated by strong hydrogen bondings due to the self‐association of PrOH and the association of PrOH with TEA. The third component, heptane, serves mainly as an inert diluting solvent. HE and VE are positive for PrOH + heptane and also for TEA + heptane to a much smaller extent. Strongly negative values of both HE and VE have been obtained for PrOH + TEA. The values obtained for the ternary system lie in between these extreme cases showing certain compositions where HE and VE vanish.—An extended version of the so‐called ERAS model has been used for describing HE and VE of the complete ternary system. The parameters adjusted to the binary data reveal that the hydrogen bonding enthalpies and volumes between PrOH and TEA are distinctly stronger than between self‐associating PrOH molecules. In addition the widely applied NRTL‐model has also been used for describing HE of the ternary systems. VE, however, can not be calculated with the NRTL model.
The Influence of the Local Anaesthetic Tetracaine on the Temperature and Pressure Dependent Phase Behaviour of Model Biomembranes
Authors: Winter R. , Christmann M.‐H. , Böttner M. , Thiyagarajan P. , Heenan R. K. 
Published: July 2012

AbstractBy using differential scanning calorimetry and neutron small‐angle scattering, the effect of the local anaesthetic tetracaine on the temperature and pressure dependent phase behaviour of model biomembrane systems, such as pure and cholesterol—containing 1, 2‐dimyristoyl‐phosphatidylcholine bilayers, has been investigated. The results provide insight into the thermodynamic and structural consequences of the incorporation of the anaesthetic into the membranes and might thus help in understanding the molecular mechanisms underlying the pharmacological action of local anaesthetics and the antagonistic effect of pressure against anaesthesia, which has been observed in vivo. Furthermore, as tetracaine can be viewed as a model system for amphiphilic molecules, knowledge of its concentration, temperature and pressure dependent phase behaviour helps in understanding the general physico‐chemical action of amphiphilic molecules on membranes.
A Computer‐controlled System of Transmission Lines for the Determination of the Complex Permittivity of Lossy Liquids between 8.5 and 90 GHz
Authors: Barthel J. , Bachhuber K. , Buchner R. , Hetzenauer H. , Kleebauer M. 
Published: July 2012

AbstractA system of computer controlled transmission lines based on the method of travelling waves is presented, permitting the precise determination of complex permittivities of medium to high loss liquids at 8.5 to 90 GHz. It consists of a newly developed apparatus for the E‐band region (60 ≤ v/GHz ≤ 90), which is described in detail, together with existing X‐ (8.5 ≤ v/GHz ≤ 12.4), Ku‐ (12.4 ≤ v/GHz ≤ 18), and A‐band (26.4 ≤ v/GHz ≤ 40) set‐ups now appropriately adapted for computer control. Consistency and accuracy of the equipment are evidenced with the help of permittivity data for water, methanol, N‐methylformamide (NMF), and N,N‐dimethylformamide (DMF).
1H NMR Studies on Molecular Motions of tert‐Butylammonium Ions in [(CH3)3CNH3]2TeX6 (X = Cl, Br) and Their Partially Deuterated Analogs, [(CD3)3CNH3]2TeX6 and [(CH3)3CND3]2TeX6 (X = Cl, Br)
Authors: Ishida Hiroyuki , Inada Syuichi , Hayama Naomi , Nakamura Daiyu , Ikeda Ryuichi 
Published: July 2012

AbstractTemperature dependences of the 1H spin‐lattice relaxation time, T1, and the second moment of 1H NMR absorptions were studied in tert‐butylammonium hexachlorotellurate(IV), hexabromotellurate(IV), and their partially deuterated analogs. From X‐ray powder patterns taken at room temperature, both complexes were found to be isomorphous with each other. For [(CH3)3CNH3]2TeBr6, a phase transition was located at 136 K by differential thermal analysis. Three kinds of motions: the reorientations of the CH3 groups about their CC bonds, the NH3+ group about its CN bond, and the tert‐butyl group about the CN bond, were observed by 1H NMR, and their motional parameters were determined. Among the three motions, the NH3+ motion was found to occur at the lowest temperature with quite small activation energies (7.9–10.1 kJ mol−1) compared with those in the simple halides.
Chlorine Perchlorate Formation in the Gas Phase Photolysis of Chlorine Dioxide
Authors: Zabel F. 
Published: July 2012

AbstractOClO/O2/N2 mixtures were photolyzed in a temperature controlled 4201 reaction chamber at temperatures between 249 and 300 K and total pressures between 0.5 and 1000 mbar. Initial OClO concentrations were in the range (1.7–5.7) · 1015 molecule/cm3. Reaction mixtures were analyzed in situ via long‐path IR absorption using a Fourier‐transform spectrometer. In some experiments product spectra were simultaneously monitored in the IR and the UV. Depending on reaction conditions, the product IR spectra were dominated by absorption bands of Cl2O3 or Cl2O4 or a mixture of both. Evidence is presented for the crucial role of O atoms in the Cl2O4 formation, suggesting either of the two mechanisms: (I) OClO + O + M → ClO3 + M → ClO3 + ClO + M → Cl2O4 + M, or (II) OClO + ClO + M → Cl2O3 + M, Cl2O3 + O + M → Cl2O4 + M. Both the weak temperature dependence and the strong pressure dependence of the Cl2O4 yield support mechanism (I). In addition, Cl2O6 was detected as a minor product of OClO photolysis under certain reaction conditions, both by its IR and UV absorption.
Is there a “Universal” Explanation for the “Universal” Dynamic Response?
Authors: Funke K. 
Published: July 2012

AbstractStructurally disordered solid electrolytes, both crystalline and glassy, as well as ionic melts, exhibit a set of spectroscopic peculiarities that are at variance with the predictions of simple random‐hopping models. Typically, stretched exponential functions are encountered where ordinary exponential functions are expected. The effect has come to be called “universal dynamic response.” In this paper, it is traced back to a mean square displacement which, in a broad time regime, varies as time to the power of β, with 0 < β < 1. Computer simulations as well as model considerations show that this particular shape of the mean square displacement is caused by the frequent occurrence of correlated forward‐backward hopping sequences. The latter processes result from the mutual repulsive Coulomb interaction of the mobile ions.
A Molecular Dynamics Study of the Dependence of the Conductivity of Sodium Beta″‐Alumina on Temperature and Frequency
Authors: Smith W. , Gillan M. J. 
Published: July 2012

AbstractThe first results of an extensive simulation study of diffusion in sodium beta”‐alumina are presented. The simulations are performed by the molecular dynamics technique on a large periodic system of 3213 ions, including all the ions in the spinel blocks, with a realistic model for the interactions between the ions. From simulations performed at a series of temperatures between 200 and 1200 K, we obtain the ionic conductivity, which, in accord with experiments, shows non‐Arrhenius behaviour. The frequency‐dependent conductivity shows marked dispersion at low temperatures, which agrees qualitatively with recent measurements. The reasons for this dispersion are discussed.
Diffusion Limited Percolation: A Model for Transport in Ionic Glasses
Authors: Bunde Armin , Maass Philipp , Ingram Malcolm D. 
Published: July 2012

AbstractWe present a novel model for ionic transport in glasses which we call diffusion limited percolation. The model focuses on the fact that each mobile ion prefers and maintains its own distinct characteristic environment in the glassy network. This leads to mismatch effects and to the existence of a memory effect which strongly influences the process of ion migration. We show that by our simple model a variety of so far imperfectly understood phenomena can be explained, among them the drastic increase of the dc conductivity of oxide glasses with the modifier content and the mixed alkali effect.
Frequency‐Dependent Conductivity. Ionic Conductivity and Memory Effects in Glassy Electrolytes
Authors: Ingram Malcolm D. , Maass Philipp , Bunde Armin 
Published: July 2012

AbstractIonic conductivities in glass depend very strongly on temperature, frequency and glass composition. In the absence of well‐defined structure, the behaviour of vitreous electrolytes may be strongly influenced by various “memory effects”. These include the classical ion‐atmosphere effect which tends to return ions to their starting positions – and hence causes a reduction in ion mobilities – and a newly formulated site memory effect, which effectively creates “cation vacancies”, and leads to conductivity enhancement. The site memory effect gives a straightforward explanation for compositional variations in conductivity (including the mixed alkali effect) and points up a connection with “strength” and “fragility” concepts of glass/melt structure.
Dynamics of Supercooled Molten Salts
Authors: Bosse J. , Henel M. 
Published: July 2012

AbstractFor the density modes of a supercooled multi‐component liquid a closed set of non‐linear integro‐differential equations is derived within the mode‐coupling approximation. Its solution requires all partial static structure factors as input information. The scope of the theory is demonstrated by studying the solutions of strongly simplified equations‐of‐motion representing a schematic model of both a molten salt near the glass transition and a glassy ionic conductor.
Hopping Conductivity in Hydrogen‐Bonded Antiferroelectric Compounds
Authors: Hutton S. L. , Fehst I. , Loidl A. 
Published: July 2012

AbstractAntiferroelectric betaine phosphate (BP: (CH3)3NCH2COO · H3PO4) and ferroelectric betaine phosphite (BPI: (CH3)3NCH2COO · H3PO3) are molecular crystals of the amino acid betaine and the phosphoric or phosphorous acids, respectively. In both compounds the inorganic components are linked by hydrogen bonds to one‐dimensional chains. The two isostructural compounds form solid solutions BPxBPI1‐x at any concentration. Here we report measurements of the dielectric permittivity for concentrations 0.85 ≤ × ≤ 1 at frequencies 10−2 ≤ v ≤ 109 Hz and temperatures 2 K ≤ T ≤ 300 K. The dielectric response in BP:BPI (x = 0.95) is dominated by contributions from pure hopping conductivity which we ascribe to the motion of the protons along the one‐dimensional chains. The onset of electric order supresses the a.c. conductivity. It will also be seen that BP:BPI (x = 0.95) shows dc conductivity in addition to the observed ac conductivity. These results are contrasted to BP and BP:BPI (x = 0.85) which reveal pure relaxational behavior.
Dielectric Studies under Pressure of the Plastic Phases of Some Alcohols
Authors: Würflinger Albert 
Published: July 2012

AbstractThe phase behaviours and dielectric properties of the plastic phases of several cyclic and branched alcohols have been studied up to pressures of 300 MPa and frequencies to 13 MHz. High values for the static permittivity are found for the liquid and the solid phases below the melting curve. For these compounds the dielectric relaxation occurs at relatively low frequencies. The loss curves have been fitted to modified Debye equations and expressions of Jonscher and Dissado & Hill. The temperature and pressure dependence of the dielectric relaxation time enables us to determine the activation enthalpy and volume, respectively. The activation quantities and parameters for the spectral shape functions of the cyclic and branched alcohols are compared and discussed.
Molecular Motions in Liquid Crystal Side‐Chain Polymers
Authors: Haase W. , Bormuth F. J. , Pfciffer M. , Jakob E. 
Published: July 2012

AbstractDielectric relaxation spectroscopy is used to investigate the molecular dynamics of liquid crystalline side chain polymers. The purpose of this comparative study is to show the influence of chemical and structural variations on the molecular dynamics and thus to contribute on the general understanding of the relaxation behaviour. On the basis of our recent measurements and by comparison to the data in literature we are able to give a detailed interpretation of the different processes in terms of basic molecular movements.
Considerations and Examples for a Uniform Behaviour of Spin‐Lattice Relaxation in Glasses
Authors: Grüne M. , Müller‐Warmuth W. 
Published: July 2012

AbstractThe NMR spin‐lattice relaxation of cation conducting glasses with an extended accessible relaxation range has been discussed in terms of current models on jump diffusion. Glassy systems with different mechanisms of motion and crystalline solids with a disordered sublattice have been found to show a similar relaxation behaviour. Spin‐lattice relaxation of all glasses appears to be quite similar, even if a quantitative description is still lacking.
Depolarized Light Scattering at the Liquid to Glass Transition
Authors: Fuchs M. , Latz A. 
Published: July 2012

AbstractDepolarized light scattering spectra in supercooled liquids are studied. Starting from a microscopic dielectric model an exact projection operator formalism is used. The change from liquid (e.g. Rytov Dip) to solid like (e.g. transverse phonon peaks) spectra upon supercooling is explained with the frequency dependence of the elasto optic constants.
DD‐Fusionsreaktionen an einem PdAg(D)‐Target in einem Minireaktor
Authors: Gentsch H. 
Published: July 2012

AbstractDeuteriumionen mit hoher Energie bis 30 ke V stoßen auf mit Deuterium gesättigtes PdAg23 als Target. 1st die Ionenenergie > 25 ke V, beginnt ein meßbarer Neutronenstrom. Der Neutronenstrom ist proportional zum Ionenstrom. Mitgeteilt werden Ergebnisse bei einem Ionenstrom von 2 μA und 27 ke V. Das PdAg ausgeführt als einseitig geschlossenes Rohr ist Kathode in einer Elektrolysezelle. Die offene Seite ist mit einer Vakuumapparatur verbunden. Von dieser Seite ragt eine koaxial angeordnete, hochspannungsisolierte Elektronenstoß‐Ionenkanone in das Rohr. Sie erzeugt Ionen aus dem eindiffundierenden Gas, die in dem starken elektrischen Feld im Vakuumspalt zwischen Ionenkanone und Metallrohr beschleunigt, mit hoher Energie gegen den Diffusionsstrom ins Metall eindringen. Die Fusionsrate ist um Faktor 100 größer als an einem reinen Gastarget.