bluuebunny/crossref_metadata_2025_split huggingface dataset:
An efficient calculation procedure of predicting heat conductivities of complex gaseous mixtures
Authors: Heintz Andreas 
Published: March 2014

AbstractA simplified expression for the heat conductivity of multicomponent gaseous mixtures λmix has been developed which allows to predict λmix with sufficient accuracy under conditions which occur in flame combustion processes. Several modifications of the rigorous kinetic theory have been made in order to reduce the computational effort of calculating λmix of molecular mixtures containing 50 or more components. Empirical functional of collision integrals based on the principle of corresponding states have been used rather than integrals which require the detailed knowledge of intermolecular forces. The translational contribution to λmix appearing in the Hirschfelder‐Eucken expression is essentially simplified by using an empirical expression originally developed by Mason and Saxena for monoatomic gaseous mixtures. Parameters such as collision numbers and diffusion coefficients of internal energy needed for the calculation of the internal contribution to λmix are reported for 27 gases relevant to combustion processes. The formula used for λmix of molecular mixtures has proved to describe λmix of 107 binary and 13 ternary mixtures with an average deviation of ±2. 9% and ±3. 4% respectively and is expected to predict λmix of multicomponent gaseous mixtures with similar accuracy.
Composition and thermochemistry of the equilibrium vapour of the systems NaI—FeI2 and NaI—PbI2
Authors: Hilpert K. , Gerads H. , Kobertz D. , Miller M. 
Published: March 2014

AbstractThe vaporization of NaI/FeI2 and NaI/PbI2 samples of equimolar composition was investigated in the temperature ranges between 574 to 683 K and 562 to 669 K, respectively, by using the mass spectrometric Knudsen effusion method. The gaseous species I. I2, Nal. (NaI)2 FeI2, (FeI2)2, FeI3, NaFel3, and Na2FeI4 (NaI—FeI2 system) as well as Nal, (Nal)2, PbI2, (PbI2)2, and NaPbI3 (NaI—PbI2 system) are present in the equilibrium vapours. The equilibrium partial pressures of these species were determined with the exception of I, I2, and Fel3. Enthalpies and entropies of dissociation resulted for the reactions magnified image as ΔdH2980 (Eq. (1)) = 184 ± 5 kJ mol−1, ΔdH2980 (Eq. (1)) = 043 ± 8 j mol−1K−1;ΔdH2980 (Eq. (2)) = 333 ± 9 kj mol−1, ΔdH2980 (Eq. (2)) = 274 ± 14 J mol−1 K−1; and ΔdH2980 (Eq. (3)) = 168 ± 5 J mol−1, ΔdH2980 (Eq. (3)) = 151 ± 9 j mol−1 K−1. Equilibrium constants for these reactions are additionally given. The pressures of NaFel3(g) and NaPb13(g) as well as their enthalpies of dissociation are discussed with respect to their significance for semi empirical rules.
Surface‐enhanced raman scattering from ethylenediaminetetraacetic acid
Authors: Lee K. A. Bunding , McLennan G. , Gordon J. G. 
Published: March 2014

AbstractSurface‐enhanced Raman scattering (SERS) from ethylenediaminetetraacetic acid (EDTA, NaO2CCH2N(CH2CO2H)CH2CH2N‐(CH2CO2Na)CH2CO2H) on silver and copper electrodes is reported. There is no SERS spectrum observed for EDTA on copper electrodes. The SERS spectrum on silver is very dependent on electrolyte and laser power. In nitrate electrolyte, most of the bands typical of EDTA are observed in the SERS spectra with small wavenumber shifts and small relative intensity changes. In 0.1 mol/1 chloride electrolyte the SERS spectra show indication of decarboxylation and are nearly identical to SERS spectra of N,N,N′,N′‐tetramethylethylenediamine (TMEDA, (CH3)2NCH2CH2N(CH3)2). However, SERS spectra of TMEDA show evidence that TMEDA also reacts. SERS spectra of ethylenediamine‐N,N′‐diacetic acid show many similar bands to those found in the SERS spectra of TMEDA.
IR reflection and raman spectroscopies of the anodic oxide films on tungsten
Authors: Ohtsuka T. , Goto N. , Sato N. , Kunimatsu K. 
Published: March 2014

AbstractIn order to understand the mechanism of the electrochromic reaction of hydrated WO3, the oxide film formed on tungsten in sulphuric and perchloric acid solutions has been studied by in‐situ optical techniques. Ellipsometric measurements reveal that the optical property of the film changes from a transparent substance to a coloured substance at a potential of E = 0.50 V (vs. RHE). The IR reflection absorption Spectroscopy (IRRAS) shows that the anodic oxide film is strongly hydrated forming two types of OH bonds, one corresponding to the incorporated H2O and the other to the OH bonded with tungsten ion. The Raman Spectroscopy (RS) shows that the anodic oxide film is an amorphous form of hydrated tungsten oxide including a terminal W(VI) = O bond. The mechanism of electrochromic reaction is discussed on the basis of IR and Raman spectra which change as the potential shifts from the transparent state to the colouring state. The electrochromic process may start with a reaction between the terminal W = O and the incorporated H2O: W(VI) = O + H2O(film) + e → W(V) — OH + OH−(film) The OH−(film) formed reacts in the film with H+ injected from the acid aqueous solution.
The anodic formation of lead iodide. Evidence for the underpotential deposition of a reversible monolayer
Authors: Tan Ah Chin , Wright Graham A. 
Published: March 2014

AbstractThe electrocrystallisation of Pbl2 has been studied using cyclic voltammetry at a rotating disk electrode of polycrystalline lead. A small anodic peak, corresponding to formation of a monolayer of PbI2, was observed. The anodic charge of 170 μC/cm2 was independent of pH, iodide concentration, potential sweep rate and electrode rotation rate. Reversal of the potential sweep gave a cathodic peak at the same potential and with the same charge and peak current; this is good evidence for the reversible formation of the monolayer, which was shown to obey the Langmuir isotherm. The monolayer appeared at an underpotential of −65 mV with respect to the reversible potential of crystalline PbI2, and this can be explained by the reduction of surface tension which occurs when the solid electrode is covered by a monolayer. At higher potentials a porous film of crystalline PbI2 was formed by a dissolution‐precipitation mechanism, with the monolayer acting as the precursor for lead(I1) iodo‐complexes.
The influence of anions on the structure of underpotentially deposited Cu on Au(111): A LEED, RHEED and AES study
Authors: Zei M. S. , Qiao G. , Lehmpfuhl G. , Kolb D. M. 
Published: March 2014

AbstractThe underpotential deposition of Cu onto Au(111) in different electrolytes has been investigated by LEED, RHEED and AES. Ordered layers of (√3 × √3) R30° and (2.2 × 2.2) type were found for Cu at medium coverages in sulfate and perchlorate solutions, respectively. The formation of different superstructures in different electrolytes is caused by the specific adsorption of the anions.
Charge transfer kinetics at semiconductor electrodes
Authors: Memming R. 
Published: March 2014

AbstractIn the present paper various factors influencing the kinetics of charge transfer processes at semiconductor electrodes are described. It is shown that the interfacial currents can be determined by the interfacial kinetics as well as by the transport of electrons and holes through the space charge layer. In the case of minority carriers created by light excitation the corresponding photocurrent‐potential dependence is frequently influenced by minority carrier trapping at the interface. In addition the influence of surface chemistry such as e.g. oxide formation is demonstrated for some photoelectrochemical reactions. Various models are presented and discussed in detail.
Behaviour of surface intermediate states in anodic O2 evolution electrocatalysis at Co3O4 on Ni and Ti substrates
Authors: Conway B. E. , Liu T. C. 
Published: March 2014

AbstractDetermination of the behaviour of the adsorbed species that are the kinetically‐involved intermediates in multi‐step Faradaic reactions of the electrocatalytic type has remained an undeveloped area of electrode kinetics, yet is important in the evaluation of electrocatalysis and reaction mechanisms of electrode processes as a function of current‐density (i) and electrode potential (V). — From values of the complementary derivatives dV/d log i, AV(t)/d log t and dV(t)/d log [—dV(t)/dt], obtained from potential‐relaxation measurements, the electrochemical behaviour and change of steady‐state coverage with potential of the intermediate states in the OER at Co3O4 is derived. The behaviour observed is related to changes of oxidation state of the bulk oxide and its surface region. — The observed potential‐relaxation and a.c. impedance behaviour is different at Co3O4 on Ni and Ti substrates. It is clearly shown that this effect arises from the additional component of impedance at the interface which is introduced by the presence of a thin underlying oxide film of TiO2 on the Ti, on which the Co3O4 film is formed. These observations have practical interest regarding preparation of composite electrocatalytic surface films on Ti substrates. Over most of the potential range studied, however, the mechanism and electrode kinetic characteristics of the OER are the same for the two metal substrates. — The O2 evolution kinetics and associated potential‐relaxation behaviour on open‐circuit, following current interruption, are determined by two pseudo‐capacitances: one arising from the potential‐dependent state of oxidation of metal ions in the oxide film and a second, coupled contribution from the potential‐dependence of coverage by OH/O intermediates on the oxide film.
Analysis and Thermochemistry of the Equilibrium Vapour of the Nal‐SnI2 and ScI3‐SnI2 Systems
Authors: Miller M , Hilpert K. 
Published: March 2014

AbstractThe NaI‐SnI2 and ScI3‐SnI2 systems were investigated under equilibrium conditions in the temperature ranges between 620 K to 840 K and 726 K to 873 K, respectively, by using a mass spectrometer coupled with a two compartment Knudsen cell. The gaseous species NaI, (NaI)2, SnI2, NaSnI3 (NaI‐SnI2 system) as well as ScI3, (ScI3)2, SnI2, ScSnI5 (ScI3‐SnI2 system) are present in the vapours. Their partial pressures were employed in a second‐law evaluation. The enthalpy and entropy changes of the dissociation reactionsNaSnI3(g) ⇌ NaI(g) + SnI2(g) (1)andScSnI5(g) ⇌ ScI3(g) + SnI2(g) (2)as well as of the reactions for the vapour transport of Na or ScNaI(s) + SnI2(g) ⇌ NaSnI3(g) (3)andScI3(s) + SnI2(g) ⇌ ScSnI5(g) (4)resulted as ΔdH0298 (Eq. (1)) = 166 ± 5 kJ mol−1, ΔdS0298 (Eq. (1)) = 144 ± 7 J mol−1 K−1; ΔdH0298 (Eq. (2)) = 172 ± 8 kJ mol−1, ΔdS0298 (Eq. (2)) = 181 ± 11 J mol−1 K−1; ΔrH0298 (Eq. (3)) = 25 ± 3 kJ mol−1, ΔrS0298 (Eq. 3)) = −1.3 ± 4 J mol−1 K−1; and ΔrH0298 (Eq. (4)) = 94 ± 6 kJ mol−1, ΔrS0298 (Eq. (4)) = 47 ± 7 J mol−1 K−1. The equilibrium constants for these reactions are also given. The data are discussed with respect to their significance for chemical vapour transport and for semi empirical rules used to predict the dissociation enthalpies of gaseous heterocomplexes.
Die Messung der Ultraschall‐Diffusion an einer Elektrode und ihre praktische Anwendung
Authors: Huck H. 
Published: March 2014

AbstractUnder the action of ultrasound (Iup to 2 W/cm2) quasi‐stationary current voltage curves were obtained, from which the densities of the exchange, the diffusion‐limited currents and the transfer coefficient were calculated. The acceleration of diffusion with ultrasound was attributed to surface cavitation involving pulsating bubbles surrounded by microstreaming. At higher sound intensities a limiting current due to cavitation saturation was observed. In order to explain this saturation effect a Langmuir kinetic for the enrichment and the depletion of cavitation bubbles beyond the threshold intensity was proposed. In the case of acoustic resonance (h=nλ/2) standing waves are generated in the solution. At the pressure loops the sound action has then a maximum. — Reproducible results were only obtained in the presence of cavitation nuclei, how they are given at rough surfaces or at smooth surfaces after adsorption of colloidal particles. The measurements were performed with Pt, glassy carbon and graphite electrodes in solutions of Fe3+/Fe2+and [Fe(CN)6]3‐/[Fe(CN)6]4‐. According to the obtainedi0values it is suspected that the complex bounded cyanid ions are favoring the exchange of electrons between the central atom and the electrode surface by an inner‐sphere mechanism.
Anomalous Behavior of Glassy GeO2 in the Reduction Process by Hydrogen
Authors: Yoshida N. , Nakanishi M. , Ikegami K. , Shimura S. , Kishimoto S. 
Published: March 2014

AbstractThe reaction of GeO2 glass with hydrogen was studied with special attention to the initial process under different conditions and the results were compared with those of crystalline GeO2. The reaction curves for the crystalline materials were a simple type which is commonly encountered in solid state reactions, whereas the curves for glassy materials at reaction temperatures above 400°C showed complicated behavior which is characterized by the presence of two steps in a reaction course. It seemed that this behavior could be understood in terms of the structural changes of the reactant involving glass transition and crystallization which are caused by the progress of the reaction. On the other hand, in the case of the reaction below 400°C, no special abnormalities were observed during the reaction.
Hydrogen Abstraction Reactions by NH2(X̄2B1)‐Radicals from Hydrocarbons in the Gas Phase
Authors: Ehbrecht J. , Hack W. , Rouveirolles P. , Gg. Wagner H. 
Published: March 2014

AbstractRate constants for the reactions of the NH2(X2B1) radical with ethane, propane and cyclohexane were measured in an isothermal flow system. Kinetic data were obtained at 4 mbar helium pressure in the high temperature range given below. [NH2](t)‐profiles were mapped at pseudo‐first order conditions [NH2]0→[RH]0 with the laser induced fluorescence technique. The temperature dependance of the rate constants is represented by the following Arrhenius‐expressions: A in [cm3/mol·s] and EA in [kJ/mol]: magnified image A correlation of the activation energy with the energy of the broken C–H bond of various hydrocarbons is discussed.
Statistics of Disordered Polymers: An Effective Hamiltonian and its Associated Gibbs Measure
Authors: Fernandez Ariel 
Published: March 2014

AbstractAn ensemble of random polymers made of two kinds of monomers is considered. The effect of quenched randomness on two and three body interactions is evaluated by comparing the Gibbs measure for an effective Hamiltonian with that for a homogeneous polymer with the same bare Flory interaction constants.
Dynamic Viscosity of Supercritical Ethene
Authors: Stanislawski Ulrich , Luft Gerhard 
Published: March 2014

AbstractThe viscosity of ethene was determined using a self‐constructed rolling ball viscometer up to pressures of 200 MPa at four temperatures ranging from 293 to 413 K. The recommended empirical equations of Reichenberg and Jossi, Stiel and Thodos predict the measured values only below 100 MPa with sufficient accuracy. The correlation of the residual viscosity with the density leads to a single curve for all temperatures and up to the greatest observed density σ = 2.7 σ. Since an exponential expression is given, the viscosity range can be extended to higher temperatures provided the density is known. The applicability of Dymond's correction of the Enskog dense fluid theory to the measured values is discussed.
Impurity Diffusion in a Chemical Potential Gradient (I): Theoretical Results
Authors: Martin M. 
Published: March 2014

AbstractA theoretical analysis has been made of the simultaneous diffusion and drift of aliovalent cation impurities B moving in a transition metal oxide AO which has been exposed to an oxygen potential gradient. Starting from linear transport theory and using the known five‐frequency‐model of impurity diffusion, expressions for the impurity and defect fluxes are derived. The corresponding coupled diffusion equations are solved analytically for the limiting cases of weak and strong impurity‐vacancy binding, and are solved numerically in the general case.
Use of a Wien Filter for Mass and Velocity Analysis of Charged Soot Particles in a Nozzle Beam
Authors: Homann K. H. , Traube J. 
Published: March 2014

AbstractA simple Wien filter in combination with an energy‐discriminating detector was used to determine mass and velocity distributions of positively and negatively charged particles in a nozzle beam. The particles were sampled from different heights in a 26.7 hPa flat, premixed C2H2/O2 flame. The method allows the measurement of mass distributions of particles with different velocities in the beam, of velocity distributions of particles with different masses, and of over‐all mass and velocity distributions, examples of which are given. There is a velocity slip of the large species during expansion of the flow. Particles with larger mass reach a lower final velocity in the beam. The velocity distributions are non‐gaussian displaying a long tail to lower velocities. The growth of positively charged soot particles from an average mass of about 1·103 u to 1·104 u takes place over a distance of 4 mm in the flame.
Precision Conductivity Measurements and DSC on Single Crystals of the Organic Conductor (FA)2PF6
Authors: Schimmel Th. , Rieß W. , Denninger G. , Schwoerer M. 
Published: March 2014

AbstractThe temperature dependence of the dc conductivity of (FA)2PF6 single crystals has been investigated using low cooling and heating rates, up to six temperature cycles between 45 K and 300 K and a very high density of data (about 80000 data points per temperature sweep). Phase transitions detected at 180 K and 200 K have been confirmed by DSC measurements. Because of the accuracy and reproducibility of the measurements, a new and detailed picture of the conductivity could be derived: at the “metal‐to‐semiconductor” phase transition at 180 K, no sudden change to a semiconductor with constant band gap occurs. Instead, an intermediate range exists between 180 K and 120 K, in which the band gap opens gradually. Thermally activated conductivity (ΔE = 60 meV – 70 meV) is observed only below 120 K. Above 215 K, the high temperature phase of fresh crystals can be fitted to a model of charge density wave (CDW) fluctuations in a one‐dimensional metal. Aged crystals above 215 K exhibit the behaviour of a onedimensional variable range hopping resistance. Conductivity hystereses can be explained as a dynamic effect of the real crystal.
Knight Shift in the Organic Conductor (Fluoranthenyl)2AsF6
Authors: Hentsch F. , Helmle M. , Köngeter D. , Mehring M. 
Published: March 2014

AbstractProton and 13C NMR Knight shift investigations performed in the organic conductor Fa2AsF6 provide locally resolved information on the electronic states of the conducting band. From single crystal measurements the principal axis values of the proton hyperfine tensor for two positions are determined.
Preparation, Crystal Structure and Dielectric Properties of the New Unsymmetrically Substituted Diacetylenes NP/R2
Authors: Strohriegl P. , Schultes H. , Heindl D. , Gruner‐Bauer P. , Enkelmann V. , Dormann E. 
Published: March 2014

AbstractWe report on the preparation, the crystal structure and the dielectric properties of several new unsymmetrically substituted diacetylenes R1,‐CC‐CC‐R2 of the general constitution NP/R2. They carry a polar nitrophenoxy‐group on one side and different urethanes on the other.
Organic Electrochemistry in the Solid State‐Overoxidation of Polypyrrole
Authors: Beck Fritz , Braun Petra , Oberst Manfred 
Published: March 2014

AbstractAnodic overoxidation of polypyrrole in the presence of nucleophiles such as H2O, OH−, CH3OH, CH3O−, Br− and CN− has been studied in detail. At potentials up to 2.1 V (vs. SCE), irreversible anodic peaks are observed with 200 nm layers on Pt. In most of the cases, a total of z = 4 – 6 F/mol monomer unit initially oxidized in the reversible potential region to the radical cation has been evaluated. Only every third ring is involved by this way. Characteristic products in aqueous systems are pyrrolinones (with a keto group in 3‐position), z = 4, and the product of further hydroxylation in 4‐position (z = 6). In the presence of the other nucleophiles, corresponding substitution products seem to be generated. The central reactive intermediate seems to be the dication. Pronounced deviations from this scheme, which is confirmed by IRRAS results, seem to proceed in the presence of strong nucleophiles as OH−, which add initially to the radical cation, and upon strong polarization, which may lead to an attack of the other rings and/or polymer destruction. Practical implications are due to polymer modification and battery material optimization.
Two‐dimensional MAS NMR: New prospects for the investigation of partially oriented polymers
Authors: Blüimich B. , Böffel C. , Harbison G. S. , Yang Y. , Spiess H. W. 
Published: March 2014

AbstractOf many interesting materials single crystals are difficult if not impossible to obtain. Examples are synthetic liquid crystalline and biological polymers. Often such materials can, however, be partially oriented. If a set of rotor‐synchronized 13C MAS NMR spectra is taken of a macroscopically anisotropic sample for different initial rotor phases, a two‐dimensional sideband spectrum can be generated by a subsequent second Fourier transformation over the rotor phase. From the sideband intensities in the new dimension the orientational distribution function can be derived for the individual carbon positions. This yields the order of the macromolecules as well as their conformation. — The new method does not require isotope labelling, the acquisition times are short compared with other two‐dimensional NMR techniques, and from a single experiment the orientational distribution function can be determined for each molecular segment with a distinguishable chemical shift. The method is reviewed and demonstrated on samples of liquid crystalline polymers and drawn polyethylene terephthalate.
Fortschritte in der 2D‐NMR‐Spektroskopie mit Rauschanregung
Authors: Armitage H. , Blümer U. , Genge I. , Khuen A. , Wille E. E. , Ziessow D. 
Published: March 2014

AbstractStochastic excitation of nuclear spin systems and subsequent nonlinear analysis of acquired excitation/response (e/r) data pairs (multidimensional stochastic method, MUDISM) yields 2D NMR spectra which provide information similar to the conventional E‐COSY and NOESY pulse schemes. For the study of complex molecules such as peptides and proteins, hardware and software has been developped which allows the continuous recording of 106 e/r data pairs where one pair occupies one 16 bit word. Many such sets are commonly measured and stored on a large‐volume hard disk, the total number of pairs being 107–108 depending on the size of the spin system. The r.f. carrier is modulated with suitable pseudo random sequences which are generated in a home‐made computer‐controlled digital pulse generator. The design and properties of these sequences are described and quaternary noise is shown to provide an excellent compromise between ease of generation and similarity to Gaussian white noise. The spin response to this noise has been simulated for coherent and incoherent interactions in order to examine the overall procedure, most notably the dependence of the residual systematic noise upon the number of measured data for given resolution. Experimental results are reported for phenylacetylene (strong coupling case), glucose in water (strong solvent line), and the cyclic decapeptide cyclosporin (complex molecule). For the latter, 80 Megapairs raw data have been acquired for a total spectral range of 3246 Hz (7.5 h magnet time) from which 2D subspectra with 512·512 points at 0.4 Hz step size are calculated. They provide evidence that the structure of complex molecule may indeed be determinded with stochastic NMR.