bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microscopic Observation of Crystallites in the Deionized Suspensions of Monodispersed Polystyrene Spheres
Authors: Okubo T. 
Published: March 2014

AbstractPhotographs are taken for the crystallites and grain boundaries in the ordered colloidal crystals of monodispersed polystyrene spheres by four methods, (1) using a metallurgical microscope with a standard illumination device, (2) a metallurgical microscope with diagonal illumination, (3) a polarized metallurgical microscope, and (4) close‐up photographing. The size of the crystallites is 100–200 urn and increases as the concentration of spheres decreases, which is consistent with the results from the reflection spectrum measurements.
Renormalization Group from a Center Manifold Reduction in Dynamic Critical Phenomena
Authors: Fernández Ariel 
Published: March 2014

AbstractWe prove that a coarse‐graining procedure is obtained by performing a center‐manifold reduction of fast‐relaxing short wavelength modes in dissipative spin systems. The probability distribution width about the center manifold is only dependent on static spin autocorrelations. Agreement with renormalization group derivations is found.
A structural interpretation of impedance spectra and radioisotope diffusion in dental enamel
Authors: Scholberg H. P. F. , Borggreven J. M. P. M. , Driessens F. C. M. 
Published: March 2014

AbstractIn this study complex impedance measurements and radioisotope diffusion experiments are used to estimate physical parameters for enamel such as pore‐diameter, membrane‐porosity and membrane‐charge. The assumptions implied in deriving a model and in estimating the membrane‐parameters and ionic radii were Verified by comparing the experimental observations with values calculated with the proposed model. A good congruence was found between the measured and calculated values. The membrane‐porosity appeared to be the main determinant for the experimentally observed wide ranges in permeability and conductance. The dependence of conductance on the electrolyte‐concentration (2 to 100 mmol/1) and ionic species (RbCl, KCl, KNO3 and Mg(NO3)2) are shown to be explained by the model in a satisfactory way.
Diffusion coefficients and thermal diffusion factors for the systems He‐CF4 and Ne‐CF4
Authors: Dunlop Peter J. , Robjohns H. L. , Bignell C. M. 
Published: March 2014

AbstractDiffusion coefficients and thermal diffusion factors are reported for the systems He‐CF4 and Ne‐CF4 between 200–400 K. The results are used to generate and test approximate potential functions for the unlike interactions.
Dynamics of proton transfer in solution by NMR relaxation
Authors: Latanowicz L. 
Published: March 2014

AbstractThe expression has been derived for the rate of intramolecular part of the relaxation induced by the motion of nuclei transferred between the two sites of unequal energy and by isotropic reorientation of nuclear pairs. This expression should be useful in analizing T1 data for hydrogen bonded liquids. — The relaxation time T1 of protons in H2O—D2O mixtures has been measured and analysed on the basis of the presented theory.
Structure determination of adsorbates on single crystal electrodes with X‐ray standing waves
Authors: Materlik G. , Schmäh M. , Zegenhagen J. , Uelhoff W. 
Published: March 2014

AbstractTl submonolayers were deposited from an aqueous electrolyte on a Cu(lll) surface. The electrodes were studied inside and outside the electrolyte with standing X‐ray wave fields. These measurements allow to determine the fraction and the position of Tl atoms which occupy adsorption sites coherently relative to the bulk diffraction planes. The results show that the method can be applied to ex‐situ as well as in‐situ structure studies of the solid/liquid interface. The influence of oxygen on immersed and emersed Cu electrodes is discussed in detail.
In situ microweighing at the junction metal/electrolyte
Authors: Stöckel Wolfgang , Schumacher Rolf 
Published: March 2014

AbstractWe report on in situ measurements of frequency shifts and charge fluxes registered simultaneously with the Electrochemical Quartz Microbalance (EQMB) on 5 MHz, 6 MHz and 10 MHz crystals, oscillating in a liquid environment. The investigations on gold electrodes reveal an influence of pH on the interfacial processes forming oxidic overlayers. This result is in agreement with a recent XPS investigation on emersed samples. It is further demonstrated, that in contrast to a single potential excursion the metallic gold surface becomes rough upon multiple potential excursions. This becomes evident from a frequency gap, that persists upon reduction. Anodic and cathodic processes on platinum electrodes lead to strong frequency changes, which are not related to weight changes. In agreement with an IR study performed recently on emersed Platinum electrodes, We attribute these frequency changes upon cycling to a transition from the hydrophilic to the hydrophobic surface state and vice versa.
The time‐resolved response of semiconductor‐electrolyte interfaces to short pulses of illumination
Authors: Gottesfeld Shimshon 
Published: March 2014

AbstractThe kinetics of elementary steps in the overall process of photoelectrochemical current generation at an illuminated semiconductor‐electrolyte interface can be investigated using relaxation techniques based on perturbations by pulses of illumination. This article reviews theoretical predictions for the form of transients expected under various experimental conditions, and compares these predictions with experimental results. Photopotential, photocurrent, and photoluminescence transient measurements following such perturbations of the semiconductor/electrolyte interface are described.
Photocapacitance study of n‐GaAs/electrolyte interfaces
Authors: Allongue P. , Cachet H. 
Published: March 2014

AbstractThe electrochemical photocapacitance spectroscopy (EPS) is used to determine the interface state distribution at n‐GaAs/aqueous electrolyte junctions. Two states (Ec — 1.30eV and Ec — 1.05 eV) are found to be related to corrosion of GaAs. It is also shown that ruthenium induces additional states 0.2 eV above the valence band. A new insight of its effect on the stabilization of GaAs is given.
Electrochemical reactivity of ordered and disordered n‐GaAs(110) surfaces. A combined XPS, LEED and electrochemical study
Authors: Solomun T. , Richtering W. , Gerischer H. 
Published: March 2014

AbstractInitial stages of electrochemical oxidation of UHV‐prepared n‐GaAs(110) surfaces, possessing either a long‐range order or an extensively damaged surface layer, were compared using an apparatus coupling ultra‐high vacuum and electrochemical practices. Not only the sputtered but also the annealed, stoichiometric surface is initially significantly more active than a surface prepared by Br2/Me etching. Anodic treatment results in a rapid loss of surface order and reactivity. A subsequent XPS analysis reveals that, irrespective of the extent of the initial surface order, an overlayer with a great enrichment of As is produced in acidic solution but not in an alkaline environment. A model is derived explaining the influence of the pH on the reactivity.
Computer supported pulse measurements of current and capacity during fast oxide formation on iron
Authors: König U. , Lohrengel M. M. , Schultze J. W. 
Published: March 2014

AbstractComputer supported potentiostatic pulse measurements are described which allow the determination of current density i in a wide range of / orders of magnitude of i and t. Pulse measurements of capacity in the same time scale reveal the electronic properties of the interface. Oxide film formation on iron is investigated as an example. Common models of high field mechanism of oxide growth and an n‐type semiconducting film are confirmed qualitatively, but in detail they have to be corrected. The n‐type semiconducting film represents only a part of the oxide, and the dielectric constant D and the donor concentration N decrease with time. The properties of a stable semiconductor develop slowly, parallel to the decrease of ionic currents in the film. That is also shown by the slow stabilization of the transpassivity.
Electroluminescence at p‐type semiconductor/electrolyte interfaces
Authors: Uosaki Kohei , Kita Hideaki 
Published: March 2014

AbstractElectroluminescence (EL) was observed at p‐InP/1 M NaOH—0.15 M S2O2−8 and p‐GaAs/0.5 M H2SO4—0.15 M S2O2−8 interfaces. Although in the former case EL was observed only when potential was kept at very negative potential as at p‐GaAs/1 M NaOH—0.15 M S2O2−8 interface, in the latter case EL was observed not only during cathodic pulse but also just after the potential was pulsed to the anodic limit. The EL observed during cathodic pulse is caused by the recombination of hole in the valence band injected by S2O2−8 and/or SO*−4, which is the one electron reduction product of S2O2−8, and electron in the conduction band. The comparison of the result at p‐GaAs in 0.5 M H2SO4—0.15 M S2O2−8 interface with that in 1 M NaOH—0.15 M S2O2−8 suggests that S2O2−8 and/or SO*−4 adsorb more strongly in 1 M NaOH than in 0.5 M H2SO4.
Some nontraditional approaches for examining strong‐ and weak‐overlap electron‐transfer processes at electrodes
Authors: Weaver Michael J. 
Published: March 2014

AbstractSome nontraditional approaches for gaining molecular‐level information on the roles of surface‐reactant interactions in electrode kinetics and mechanisms are described with the aid of recent results from our laboratory. The virtues of evaluating unimolecular rate constants, ket (s−1), for one‐electron transfer reactions for both inner‐ and outer‐sphere pathways are pointed out. Illustrative data are presented for the reduction of pentaamminecobalt(lll) anchored to metal surfaces via systematic series of organic and inorganic bridges, X, with the objective of probing the sensitivity of the electronic transmission coefficient, Kel, and the intrinsic electron‐transfer barrier, ΔG*int to the geometry and electronic structure of the bridging ligand. Evidence is presented that most of the ca. 106 fold rate variations are due to variations in Kel, the reactions being of the “weak‐overlap” type, although the especially large ka values seen for the small inorganic bridges may be due in part to diminutions in ΔG*int, caused by the onset of “strong‐overlap” behavior. Several applications of surface‐enhanced Raman spectroscopy for examining the vibrational properties of adsorbed reactants and reaction intermediates are also described. These include experiments aimed at elucidating the structural perturbations induced by surface‐reactant binding, and for obtaining a molecular identification of adsorbed reaction intermediates in multistep electrode processes.
The kinetics of the polycrystalline Ag/Ag+‐electrode studied by high‐frequency impedance spectroscopy
Authors: Schöne G. , Wiesbeck W. , Stoll M. , Lorenz W. J. 
Published: March 2014

AbstractThe fast charge‐transfer reaction of the polycrystalline Ag/Ag+‐electrode was studied using a new technique of high‐impedance spectroscopy working in the frequency range between 1 kHz and 5 MHz. The method is characterized by a special electrochemical cell with two working electrodes, a new designed de‐control being completely ac‐decoupled, a highly precise impedance measurement technique (ICEP = Impedance Conversion and Error Processing) and the quantitative calculation of the electrodynamic field distribution. The accuracy of the measurements is better than 0.05%. The results obtained in the Ag/Ag+‐system are in a quantitative agreement with a theoretical transfer function based on a 2‐D inhomogeneous surface model. The exchange current densities were found to be about half an order of magnitude higher than the literature data.
Research on chemically modified electrodes: Electrocatalytic reduction of dioxygen by iron tetraphenylporphyrin modified glassy carbon electrode with heat treatment
Authors: Dong Shaojun , Jiang Rongzhon 
Published: March 2014

AbstractThe heat treatment of iron tetraphenylporphyrin chemically modified glassy carbon electrode is described. This electrode shows high catalytic activity and good stability for dioxygen reduction. Its catalytic activity is still maintained through 1000 cycles of potential scans (100 mv/s) in an air saturated solution of 0.05 M H2SO4 after a heat treatment to 500°C. Using XPS, Mössbauer, UV‐VIS spectroscopy and mass spectroscopy the microstructure of the electrode surface has been analyzed. The electrocatalytic and dynamic behavior for dioxygen reduction has been studied by cyclic voltammetry and rotating disk electrode respectively. The rate constants for dioxygen reduction at the electrode in a variety of pH solutions have been measured.
Electrochemical Photocapacitance of ZnSe: Effect of Photoelectrochemical Etching
Authors: Tenne R. , Haak R. , Triboulet R. 
Published: March 2014

AbstractMeasurements of electrochemical photocapacitance spectroscopy (EPS) of ZnSe were carried out with the aim of studying the effect of photoelectrochemical etching. A new transition is observed that can be assigned to a shallow acceptor state. The observation of that transition is explained by the etching‐out of shallow donor states which are associated with acceptor states. Thus acceptor states which were “dormant” before the process become observable after photoelectrochemical etching.
Thermochemical Study of the Gaseous Molecules EuNbO3, EuNbO2, EuNb2O6 and of the Niobium Oxides NbO and NbO2
Authors: Balducci G. , Gigli G. , Guido M. 
Published: March 2014

AbstractThe gaseous ternary oxide molecules EuNbO3, EuNbO2 and EuNb2O6 have been identified by high temperature mass spectrometry in the vapours in equilibrium over a mixture of europium sesquioxide and niobium monoxide in a molybdenum Knudsen cell over the temperature interval 1996–2382 K. From the study of various all‐gas equilibria, the atomization energies and the standard heats of formation for these molecules were derived. In addition, from the study of a gaseous exchange reaction involving EuO, NbO, and NbO2, new results for the niobium oxides were obtained and compared with literature data. — The proposed values are: ΔH0o,at(EuNbO3 = 2396 ± 29 kJ/mol; ΔH0o,at(EuNbO3 ∼ 1675 kJ/mol; ΔH0o,at(EuNbO3 = 5070 ± 39 kJ/mol; D0o(NbO) = 774 ± 18 kj/mol; ΔH0o,at(NbO2) = 1405 ± 14 kJ/mol. — The corresponding standard heats of formation are: ΔH0f,298(EuNbO3,g) = −756 ± 33 kJ/mol; ΔH0f,298(EuNbO2,g ∼ −279 kJ/mol; ΔH0f,298(EuNbO2O6,g = −1972 ± 51 kJ/mol; ΔH0f,298(NbO,g) = 202 ± 25 kJ/mol; ΔH0f,298(NbO2,g) = −185 ± 22kJ/mol.
The Interaction of CFCl3 and CF2Cl2 with Solid Surfaces Studied by Thermal Desorption Mass Spectroscopy
Authors: Buchmann Lutz‐Martin , Illenberger Eugen 
Published: March 2014

AbstractAdsorption and desorption of CFCl3 and CF2Cl2 on Fe and pyrex glass surfaces has been studied in the temperature range 90–400 K. In contrast to a previous study of the interaction of CFCl3 with a clean Fe(100) surface, for the samples presently used no extra cleaning procedure has been applied in the UHV. Under these conditions adsorption only occurs at temperatures not far from conditions for condensation. From the desorption spectra, the activation energy of desorption for CFCl3 on a Fe surface is 36.8 ± 2 kJ mol−1 (at 148 K) and the heat of vaporization 34.7 kJ mol−1 (at 128 K). No evidence for dissociative adsorption of CF2Cl2 or CFCl3 (as was the case for CFCl3 on a clean Fe surface) has been found. In addition, no evidence for a photon stimulated decomposition of these molecules when adsorbed on these surfaces has been found when visible laser light is used. The results are discussed with respect to the problem whether surfaces may operate as sinks for halocarbons released into the atmosphere.
Scavenging of Radicals from the Gas Phase by Freezing with Dimethyl Disulfide
Authors: Schottler M. , Homann K. H. 
Published: March 2014

AbstractH and O atoms and methyl radicals produced in microwave discharges of H2/He, O2/He and CH4/He mixtures, respectively, were scavenged by supersonic nozzle probing with subsequent freezing and reaction with dimethyl disulfide on a liquid nitrogen cooled wall. The main reaction products for the three kinds of radicals were CH3SH, CH3S(O)SCH3 and CH3SCH3, respectively. Side products were CH3SCH2SSCH3 and CH3SSSCH3 for H atoms and CH3S(O)2SCH3 for O atoms. – The scavenging efficiencies for the different radicals were determined and measured as a function of the gas phase radical concentration, the flow of scavenger molecules, the pressure in the vacuum chamber, and the conditions of the discharge and the flow through the sampling nozzle. It is concluded that this method is suitable for light radicals with reservations in the case of H atoms and can probably be used with still better success for heavier radicals.
Scavenging of Radicals from the Gas Phase by Freezing with Dimethyl Disulfide. 2. Radicals from Discharges and a Flame of Acetylene
Authors: Kubitza Ch. , Schottler M. , Homann K. H. 
Published: March 2014

AbstractThe method of detecting radicals from low‐pressure gas‐phase systems by scavenging with dimethyl disulfide (DMD) has been applied to microwave discharges in C2H2/He mixtures and to a C2H2/O2 flame. It was accomplished by condensing a supersonic nozzle beam from the reaction system together with a beam of DMD on a liquid‐N2 cooled surface. The scavenging products were measured by GC/MS after warming‐up. Radicals measured in the discharge were C2H, C4H, C6H, C3H2, C2 besides H atoms. Preliminary measurements on the flame showed that C6H5 (phenyl), CH2, C3H2, besides H and O atoms were prominent radicals at the end of the oxidation zone. The concentration of phenyl is of the same order as that of e.g. naphthalene. The method provides a means to distinguish condensible flame products from those that are formed during the sampling process when no scavenger is added.
Kinetics, Energetics and OH Product Yield of the Reaction CH3O + O(3P) → CH3O*2 → Products
Authors: Ewig F. , Rhäsa D. , Zellner R. 
Published: March 2014

AbstractThe rate constant for the reaction (1) CH3O + O → products at 298 K has been determined using 248 nm laser co‐photolysis of CH3ONO/O3 mixtures for the generation of CH3O radicals and O atoms combined with LTF for time resolved detection of CH3O and product OH. k1 is found to be (2.5±0.7) 10−11 cm3/s with a relative yield of OH of Φ = ‐Δ[OH]/Δ[CH3O] = 0.12+0.08−0.04. The results are shown to be consistent with a primary capture mechanism on an electronically adiabatic surface forming highly vibrationally excited CH3O and followed by rapid subsequent decomposition or isomerization, viz. magnified image.From modelling of the OH yield using RRKM theory the isomerization barrier between CH3O2 and CH2OOH is placed near 160 kJ/mol in good agreement with recent ab initio calculations. As a consequence the CH3 + O2 combustion reaction is predicted to proceed primarily via the low energy CH2O + OH channel, in contrast to most previous suggestions.
Determination of the Dissociation Energy of the Cr2 Molecule
Authors: Hilpert K. , Ruthardt R. 
Published: March 2014

AbstractA Knudsen cell — mass spectrometer system has been developed allowing for the determination of extremely small partial pressures. This instrument and a second different Knudsen cell — mass spectrometer system were used to study the thermochemistry of the vapour over chromium. The results obtained by the two instruments agreed excellently. The partial pressure of Cr2(g) was determined in the temperature range between 1542 and 1819 K to be magnified image The enthalpies of sublimation and dissociation for Cr2(g) essentially resulted from eight independent runs according to a second‐law evaluation as ΔsubH = 612 ± 4 kJ mol−1, ΔsubH = 653 ± 4 kj mol−1, and ΔsubH = 652 ± 4 kJ mol−1 as well as ΔsubH = 150 ± 5 kJ mol−1, ΔsubH = 142 ± 5 kj mol−1, and ΔsubH = 139 ± 5 kj mol−1. The binding energy for Cr2(g), De = 142 ± 5 kJ mol−1, was determined. An evaluation of the enthalpy cf dissociation for Cr2(g) according to the third‐law method shows indirectly the existence of low‐lying electronic states for this dimer. The binding energy of Cr2(g) obtained here is compared with those predicted by numerous theoretical computations using different methods. The ionization potential of Cr2+ was determined by ionization efficiency measurements to be 6.4 ± 0.2 V.
The Influence of Dissolved Electrolytes on the Miscibility of Binary Liquid Systems with Closed Miscibility Gaps
Authors: Erol M. , Kocak M. , Richter P. , Steiger A. , Becker F. 
Published: March 2014

AbstractThe dependence of the upper and lower critical solution temperatures Tc of the systems (1) oxolane + water, and (2) 2‐butoxyethanol + water on the mole fraction XEl of dissolved 1‐1, 2‐1, and 3‐1 electrolytes has been investigated. The material stability of the homogeneous state of both systems is extremely sensitive to small electrolyte concentrations so that the observed shift of Tc may be interpreted as the result of a perturbation of the mutual solvation of both non‐electrolytes by ion solvation. Cations destabilize homogeneity in the order Me+ < Me2+ Me3+. The nature of the anions, however, for which the order Cl− > Br− > I− > NO−3 > ClO4− is established, determines whether the closed miscibility gap expands, shrinks, or is shifted to higher temperatures with increasing xEL. The importance of the anions is evident from a comparison of MgCl2 and Mg(ClO4)2, for which the lower critical solution temperatures of oxolane + water at XEl = 0.003 differ by about 70 K.
Impurity Diffusion in a Chemical Potential Gradient (II): Iron Tracer Diffusion in Cobalt Oxide in an Oxygen Potential Gradient
Authors: Martin M. , Dorris S. 
Published: March 2014

AbstractImpurity tracer diffusion coefficients for 59Fe in CoO have been measured as a function of the oxygen activity at a temperature of 1200°C. The results can be described by a weak impurity‐vacancy binding at high oxygen potential and a strong binding (Δgv = −0.7 eV) at low oxygen potential. Impurity tracer diffusion has also been measured for 59Fe in CoO which has been exposed to an oxygen potential gradient. In addition to the normal Brownian motion the impurity cations are seen to drift in the crystal as a result of the cation vacancy wind. These results confirm the picture of weak binding at high oxygen potential and strong binding at low oxygen potential. From both experiments it is possible to calculate frequency ratios or directly the frequencies of vacancy jumps.
Studies on the Interaction of Anthraquinone Triplet and α‐Phenylethyl Hydroperoxide in Benzene and Chlorobenzene
Authors: Móger G. , Paál‐Lukács J. , Gál D. 
Published: March 2014

AbstractThe quantum yields of the formation of products as well as their temperature dependence during the photochemical decomposition of α‐phenylethyl hydroperoxide (HROOH) have been measured in the presence of triplet anthraquinone (TQ) in air‐saturated benzene and chlorobenzene at 301–373 K. The photochemical and thermal decomposition of HROOH have been compared. Experimental results and their mathematical simulation indicate that in the reaction of TQ with HROOH peroxy radicals, HRO2, are generated. According to the measurements magnified image at T	= 30 K, and the energy of activation of the reaction magnified image is about 5.9 kJ mol−1.