bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adsorption Kinetics of Dye Molecules on Polymer Membrane Filters
Authors: Kost S. H. , Breuer H. D. 
Published: July 2012

Abstracte kinetics of the adsorption of dye molecules on membrane filters made of cellulose nitrate have been studied. In order to obtain thermodynamical data the temperature has been varied from 283 K to 333 K. Because kinetic laws of 1. or 2. order cannot describe the experimental results two different theories were applied. In addition to a classical concept a new equation based on the fractal theory has been checked and has proved to be suitable for adsorption data. We have shown that obtained fractal parameters, fractal dimension Ds and fractal dimension Df, are in excellent agreement with other fractal kinetics experiments.
Prediction of the Isothermal Expansion Coefficient of Electrolyte Solutions Containing Dissolved Gases
Authors: Vogt H. 
Published: July 2012

AbstractDensity data of solutions of electrochemically generated gases such as hydrogen, oxygen, chlorine, carbon dioxide in water and electrolyte solutions are not available even from comprehensive data compilations. The same applies to the isothermal expansion coefficient due to varying concentrations of dissolved gases. These data, however, are necessary for calculations of natural convective mass transfer at gas‐evolving electrodes. An equation for prediction of the expansion coefficient is proposed and compared with some available data obtained experimentally.
The Formation of O and H Atoms in the Reaction of CH2 with O2 at High Temperatures
Authors: Dombrowsky Ch. , Hwang S. M. , Röhrig M. , Gg. Wagner H. 
Published: July 2012

AbstractThe formation of O and H atoms in the reaction of CH2 with O2 was investigated behind incident shock waves at temperatures between 1000 K and 1700 K and at total densities between 5 · 10−6 and 1 · 10−5 mol/cm3 by means of Atomic Resonance Absorption Spectroscopy (ARAS) at 130.5 nm and 121.6 nm, respectively. The contribution of O and H forming channels was found to be about 20%. The rates of formation of O and H atoms in this reaction were determined to bek1a = (4 ± 2) · 1010 cm3/mol · sk1e = (5 ± 2) · 1010 cm3/mol · sIn the temperature range investigated an over all rate constant can be represented by k1 = (5 ± 3) · 1011 cm3/mol · s. A comparison with low temperature data leads to a change of the apparent energy of activation of the overall reaction in the temperature range between 300 and 1000 K.
Study of Homogeneous Reactions with on Line Mass Spectrometry and Potentiometry: The Belousov‐Zhabotinsky‐Reaction
Authors: Schmidt V. M. , Vielstich W. 
Published: July 2012

AbstractPotential oscillations of the Ce3+/Ce4+ redox couple in the Belousov‐Zhabotinsky reaction has been followed using a smooth and a platinized Pt electrode. The same potential oscillations are observed when applying a smooth Pt and a reference (RHE). With a platinized Pt electrode and a RHE as pair of electrodes however, only weak signals are obtained. This effect is due to the slow potential equilibration in a porous metal structure. — A more detailed study of the reaction steps can be made via simultaneous registration of the Ce3+/Ce4+ potential and the oscillations in CO2 formation rate using a PTFE membrane as an interface to a mass spectrometer. The CO2 formation follows the potential oscillation. The maximum rate of CO2 production occurs in the moment of highest Ce4+ concentration with a certain delay of time.
Cationic Self‐Diffusion in the Highest‐Temperature Solid Phases of Ammonium Chloride and Bromide Studied by 1H NMR
Authors: Tansho Masataka , Furukawa Yoshihiro , Nakamura Daiyu , Ikeda Ryuichi 
Published: July 2012

AbstractIonic motions in the highest‐temperature solid phases (Phase I) of NH4Cl and NH4Br having the NaCl‐type cubic structure were investigated by measuring 1H NMR spin‐lattice and spin‐spin relaxation times (T1, T1ϱ and T2). A long T2 of ca. 1 ms observed at 750 K in Phase I of both salts was attributed to the excitation of the rapid cationic self‐diffusion and isotropic rotation suggesting the plastic nature of this phase. The observed relaxation times could be explained well using the monovacancy‐diffusion model proposed by Sholl. The activation energy of self‐diffusion was determined as 120 kJ mol−1 for both salts, which value is much larger than those observed in ionic‐plastic phases with the CsCl‐type cubic structure. The diffusion mechanisms of the NH4+ ions in Phase I, and Phase II having the CsCl‐type structure, were compared.
Photochemical Decay Reactions of N2O5, HNO3, CINO3 and BrNO3 in the Energy Range 10–20 eV
Authors: Jochims H.‐W. , Denzer W. , Baumgärtel H. , Lösking O. , Willner H. 
Published: July 2012

AbstractThe photochemical behaviour of gaseous N2O5, HNO3, CINO3 and BrNO3 has been investigated in the energy range 10–20 eV by photoionization mass spectrometry using monochromatized synchrotron radiation. The decay reactions are analyzed using the photoion yield curves of fragment ions and their appearance energies. Hitherto unknown photochemical reactions and thermochemical data have been evaluated.
How Random are Regulatory Signals in RNA Replication? Evolutionary Constraints do not Play a Decisive Role
Authors: Fernández Ariel 
Published: July 2012

AbstractWe propose a kinetically‐controlled Monte Carlo simulation to investigate the search in configuration space of an RNA molecule which folds onto itself as it is being assembled by sequential incorporation of nucleotides. The results are specialized to the template‐directed synthesis of MDV‐1RNA performed by Qß‐replicase. The theoretical predictions are compared with existing experimental results obtained by pulse‐chase electrophoresis. The simulation reproduces satisfactorily the observed variable rate of chain elongation and specifically enables us to establish that the rate of growth out of a pause site is identical to the rate of the refolding event which has induced the pause. Moreover, our results reveal that the extent of functionally‐relevant secondary structure does not differ appreciably from that of a randomly generated sequence. This result suggests that the transient structures whose formation induce regulatory signals have not been selected by evolution.
Electrochemical Color Change of 1,4‐Diketo‐3,6‐Diphenyl‐Pyrrolo‐[3,4‐c]‐Pyrrole
Authors: Mizuguchi Jin , Rochat Alain Claude 
Published: July 2012

AbstractThe title compound (DPP) is a red pigment based on the diketopyrrolopyrrole chromophore. DPP is, however, transparent in solution and appears slightly greenish‐yellow. It has been found that DPP turns red when electrochemically reduced (“electrochromism”). Electrochromic properties of DPP have thus been investigated in the presence of sodium ferrocyanide or ferrocene used as a sub‐redox system. Attention has been paid to the elucidation of the coloration mechanism by means of voltammetry and spectroscopy. The first reduction of DPP proceeds in a one‐electron process and is reversible, whereas the second reduction is irreversible. The electrochromic red color arises as a result of deprotonation at the NH group which follows the cathodic reduction. The mono and di‐deprotonation give absorption maxima at 582 and 620 nm, respectively.
Negative Ion Chemistry in Clusters
Authors: Illenberger Eugen 
Published: July 2012

AbstractFor the prototype system oxygen it is shown that electron attachment to clusters results in a variety of new processes which do not show up in the single molecule. These are (a) formation of molecular anions in their stable configuration, (b) population of electronic states not accessible in isolated molecules and (c) secondary reactions due to inelastically scattered electrons within one cluster.
Direct Absorption Studies of Jet‐Cooled Metal Dimers: Magnesium and Cesium
Authors: Lauterwald H. , Rademann K. 
Published: July 2012

AbstractOptical absorption of diatomic magnesium and cesium molecules is investigated in a supersonic molecular beam. A vibronic band of Mg2, which is located at 270nm and assigned to a 1Πu ← 1Σg+ transition, is found to have remarkable fine structure. The vibrationally resolved spectrum and the spectroscopic constants of the excited state are reported here for the first time.
Highly Sensitive Infrared Spectroscopy: IR‐REMPI Double Resonance Experiments
Authors: Bahnmaier Albert H. , Schmid Reiner , Zhang Bing , Jones Harold 
Published: July 2012

AbstractThe first double resonance signals involving the use of a c.w. infrared laser and multiphoton ionization Spectroscopy using a pulsed UV laser has been observed in 15NH3. Despite the low duty‐cycle of such a combination, very strong double resonance signals were observed using a low power CO2 laser as infrared source. The observations indicate that such measurements should be possible with the extremely low power levels available from tunable diode lasers. Such a combination would allow high resolution infrared Spectroscopy to be carried out with the sensitivity of ionization Spectroscopy and allow application to molecular species such as clusters. Term values of 15NH3 have been calculated from the data.
Characterization of Silica Supported Transition‐Metal Oxide Catalysts by Luminescence Spectroscopy
Authors: Hazenkamp M. F. , Blasse G. 
Published: July 2012

AbstractThe luminescence properties of some silica‐supported transition‐metal (Mo, W, Nb, Re) oxide catalysts are reported under dehydrated conditions and at low temperatures. The luminescence results are used to identify the metal oxide species in the catalyst samples. UV/VIS reflection spectroscopy is used as an additional tool. The anomalously long decay times of the luminescence of the Mo/SiO2, W/SiO2 and Nb/SiO2 samples indicate that in these samples there are strongly distorted monomeric oxo‐transition‐metal species present. The luminescence of the Re/SiO2 sample is very weak. It is the first report of luminescence of a perrhenate complex. Finally, the possibilities to use luminescence spectroscopy to characterize supported transition‐metal oxide catalysts are evaluated.
Phase Transitions in Minerals: From Equilibrium Properties Towards Kinetic Behaviour Progress Report
Authors: Salje E. K. H. 
Published: July 2012

AbstractLandau theory is derived from a simple atomistic model. The Gibbs free energy can be written in the displacive limit as magnified image where Ts = 1/2Θs is the saturation temperature due to quantum fluctuations. The coefficients A, B,… and degeneracies of the order parameter are determined by the conventional symmetry constraints. For T > Θs, G is the classic Landau potential. Solutions for non‐displacive systems and coupled order parameters are discussed. – The theory is applied to some model‐minerals such as quartz, Na‐feldspar, and calcite as typical examples. It is argued that the structural complexity of minerals is often related to several thermodynamic degrees of freedom. The transition leads to coupling phenomena, which are reviewed in some detail. – Non‐equilibrium features in crystals which are “nearly” in thermodynamic equilibrium are domain walls. It is shows that domain walls react very sensitively to small changes in the thermodynamic state of the material. New structural configurations are generated in the wall which do not exist in the bulk. – Kinetic processes with continuous order parameters can be analysed using a general rate equation which contains δG/δQ (G is often a Landau potential, Q is the order parameters) as a driving force. This theory draws, thus, a connection between the equilibrium Landau‐type theories and kinetic rate theories.
Electron Density and Chemical Bonding: The Shape of Independent Atoms in Molecules
Authors: Irie S. , Lin H. L. , Niu J. E. , Schwarz W. H. E. 
Published: July 2012

AbstractElectron density distributions ρ(r) contain three types of features, which give rise to a new natural approach of analyzing ρ with respect to chemical bonding. These features are 1) the very large spherical atomic core densities, defining the geometric structure, 2) the small multipolar atomic valence densities, defining the orientation and population of partially filled p‐ and d‐shells of the “independent atoms” in the molecule or crystal, and 3) the very small density deformations due to the interatomic interactions. The valence shell parameters and the Chemical Deformation Densities are determined theoretically and experimentally for molecules and crystals. The features are brought in relation to intramolecular and intramolecular interactions.
The Transition from Molecular Units to Collective Structures in Complex Transition Metal Chalcogenides, Characterized by Magnetochemical Experiments Progress Report
Authors: Bronger W. 
Published: July 2012

AbstractDepending on the stoichiometry the alkali metal‐transition metal‐chalogenides crystallize analogous to the silicates in structures with isolated groups, chains or layers. The formation of the framework structures is realized by linkage of anionic transition metal‐chalcogenide complexes. – The magnetic properties of the transition metal ions are used as an indicator for the changes in bonding properties at the transition from molecular units to the collective framework structures. Susceptibility measurements and neutron diffraction experiments show a reduction of the magnetic moments with an increasing degree of linkage in the anionic frameworks of these structures. Crystal field calculations, based on a point charge model, concerning the total atomic arrangement, show a strong correlation with the series of magnetic moments. For ternary phosphides, arsenides etc. corresponding relations exist.
Investigation of Sub‐Shell Occupation in Some Ba Compounds by LMTO‐ASA Calculations
Authors: Felser‐Wenz Claudia , Hohlneicher Georg , Andersen O. K. , Jepsen O. 
Published: July 2012

AbstractBa compounds behave very unusual in XPS‐studies as they exhibit only small and often negative binding energy shifts. Four different explanations have been given for these observation. To provide a more quantitative basis for these different models and to shed new light on the unusual behaviour of Ba compounds, we calculated total and 1‐projected densities of states for Ba metal and three Ba compounds. All four explanations given up to now are not in qualitative agreement with the obtained results. A different possible explanation is discussed.
Thermodynamics, Structure, and Structural Dynamics in Glass Progress Report
Authors: Ingram Malcolm D. 
Published: July 2012

AbstractA common feature of glass is the thermodynamic instability which manifests itself in differences between Tg and To, and in the existence of many relaxation/memory effects. These latter are observable by DSC, by crystallisation studies and by mechanical spectroscopy, and play an important rǒle in relation to such ubiquitous phenomena in “ionic” glasses as the conductivity dispersions and the mixed alkali effect. The concept of strong and fragile liquids provides a useful way of comparing the behaviour of glass‐forming systems, and for observing the influence of chemical bonding on the structural dynamics. It is the existence of the wide spectrum of structural relaxations, however, which seems to be the distinctive feature of the glassy state, rather than the presence of any special kind of chemical bonding or structural units.
Spinodal Decomposition in Solutions of Ternary Oxides
Authors: Burkert N. , Grüne R. , Schmalzried H. , Rahman S. 
Published: July 2012

AbstractA miscibility gap exists in the quasi‐binary solid solution Co2TiO4 – CoAl2O4 as verified by experimental investigations and theoretical calculations. The critical temperature is ca. 1700 K. Spinodal decomposition was observed in this two‐cation‐sublattice system, if the spinel solid solution had been undercooled into the region of the coherent spinodal at T = 973 K. Simultaneous ordering occurs in certain regions of the crystal. The growth‐rate of the spinodal wavelength λ varies linearly in time. This unusual quasi‐ripening process is discussed in relation to the characteristic features of diffusion in (semiconducting) oxides.
Computerunterstützte Thermodynamik fester Ni–Pd Legierungen über die Knudsenzellen‐Massenspektrometrie und Berechnung des Zustandsdiagrammes
Authors: Kopecky K. , Belegratis M. S. , Neckel A. , Tomiska J. 
Published: July 2012

AbstractSolid Ni–Pd alloys have been investigated thermodynamically by means of the computer‐aided Knudsen cell mass spectrometry. Thermodynamic evaluation has been performed by applying the enlarged “Algebraic Intensity‐Ratio”‐method (A.I.R.). The thermodynamic excess properties can be described algebraically by means of T.A.P.‐series (Thermodynamically adapted power series) with three adjustable parameters (C = [8757.5–11.2810 T/K] J/mol; C = [–18573.3 + 5.1073 T/K] J/mol; C = [3908.0–0.4558] J/mol). – At higher temperatures solid Ni–Pd alloys are characterised by negative molar excess Gibbs energies GE, and slightly positive molar excess entropies SE. At 1500 K the minimum GE‐value is –3270 J/mol (57 at.% Pd), and the maximum SE‐value is 2.25 J/mol·K (43.7 at.% Pd). Ni–Pd alloys with Pd contents with less than 50 at.% Pd show endothermic molar heats of mixing HE (maximum value: 835 J/mol at 21.5 at.% Pd), whereas Ni–Pd alloys with more than 50 at.% Pd show slightly exothermic HE‐values (minimum value: –575 J/mol at 79.5 at.% Pd). The thermodynamic Pd‐activities aPd exhibit at 1500 K over the whole concentration range slightly negative deviations from Raoult's law. The thermodynamic Ni‐activities aNi of the Ni‐rich solid alloys (xPD < 0.25) show at 1500 K nearly ideality, Ni–Pd alloys with higher Pd contents than 25 at.% Pd were found to show slightly negative deviations from ideality. – The phase diagram has been computed by means of a generally applicable procedure for the calculation of the equilibrium compositions of coexisting phases. The calculations were based upon the results of this work, the thermodynamic data from mass spectrometric studies on the liquid phase, and literature data for the heat capacities and enthalpies of Ni and Pd.
A.C. Impedance Studies of Glassy and Crystalline Lithium Aluminosilicate Compounds
Authors: Munro B. , Schrader M. , Heitjans P. 
Published: July 2012

AbstractA.C. impedance spectroscopy was used to characterise the electrical conductivity behaviour of polycrystalline β‐LiAlSi2O6, β‐LiAlSiO4 and the corresponding glasses with identical stoichiometric compositions. Two bulk conduction processes with different activation energies were detected for β‐LiAlSiO4. The dispersion in the conductivity of the samples, the non‐Debye conductivity relaxation and the frequency dependence of the a.c. activation energies are discussed. The problem of how best to compare data from impedance measurements with results obtained from NMR relaxation experiments is addressed. It was found that diagrams of log resistivity against reciprocal temperature, plotted for individual frequencies, are suitable for comparing directly with NMR data.
Observation of Two Relaxation Processes in an Ion Conducting Glass Yields New Structural Information
Authors: Cramer C. , Funke K. 
Published: July 2012

AbstractThe frequency dependent ionic conductivity of the glass B2O3·0.56Li2O·0.45 LiBr has been measured from 1kHz up to 60 GHz, at temperatures up to 573 K. At first sight, the frequency spectra seem to conform with the so‐called “new universality”, i.e., with a σ(ω) ∝ ω1.0 power law at high frequencies/low temperatures. However, inspection of Arrhenius plots constructed at different frequencies clearly shows that two very well defined processes are superimposed, featuring different activation energies and different power‐law exponents. The latter are 0.67 and 1.30, respectively, while a genuine power law with exponent 1.0 does not exist. The two processes are identified with translational jump diffusion (including jump relaxation) and a non‐Debye localised reorientational motion of the ions within a given neighbourhood.
Alkali Intercalation into Layered Compounds: UHV in‐situ Preparation and Reactivity
Authors: Schellenberger A. , Jaegermann W. , Pettenkofer C. , Papageorgopoulos C. A. , Kamaratos M. 
Published: July 2012

AbstractLi was adsorbed at room temperature (RT) onto UHV cleaved 2H WX2 (X = S, Se) and 1T TaS2 (0001) van der Waals surfaces. On TaS2 Li is intercalated in terms of the rigid band model leading to several phase transitions of the charge density waves. On WX2 Li is intercalated for low concentrations and leads to a decomposition reaction to Li2S and W0 for high concentrations. These experimental results and those of previously studied alkali/layered chalcogenide combinations and their reactivity are discussed in terms of thermodynamic, kinetic and electronic effects.
Defect Chemistry and Luminescence of ZnS: Cu, Au, Al
Authors: Bredol M. , Merikhi J. , Ronda C. 
Published: July 2012

AbstractPresent high quality CRT TV sets employ wurtzite–(Zn,Cd)S:Cu,Al phosphor or its Cd‐free variant sphalerite‐ZnS:Cu,Au,Al to generate the green primary colour. If prepared properly, both phosphors exhibit the desired emission properties. However, the Au‐codoped material tends to large variations of the emission as a function of the preparation procedure and thus is more demanding in terms of precise control of the manufacturing process. – This work aims at a better understanding of these peculiarities. Experiments are presented which demonstrate the large influence of the defect chemistry of the ZnS‐host on the Au‐related emission, whereas the Cu‐related emission is affected to a lesser extent. – Possible techniques for a fine‐tuning of the emission spectrum are discussed and evaluated according to the requirements of screen manufacture.
Formation of Aluminium(III)‐Monocarboxylates in Aqueous Solution
Authors: Pohlmeier Andreas , Thesing Ulrich , Knoche Wilhelm 
Published: July 2012

AbstractBy means of stopped‐flow experiments equilibrium and rate constants are determined for the weak complexation of the aluminium(III)‐ion with formate, acetate, chloroacetate and benzoate. For the innersphere complex formation both equilibrium and rate constants depend on the nature of the ligand, and a linear free energy relation is observed between rate constants and dissociation constants of the corresponding acids.
Volume‐Explicit Perturbed Hard‐Sphere Equation of State for Dense Gases at High Pressures
Authors: Nezbeda Ivo , Vörtler Horst L. 
Published: July 2012

AbstractAn attempt is made to construct an equation of state of dense gases at high pressures in a volume‐explicit form. The equation is a simple perturbed hard sphere equation and is based on the finding that the volume‐explicit equation of state of the fluid of hard spheres captures not only qualitatively but also, roughly, quantitatively the temperature‐ and pressure‐dependence of volume of non‐associating gases at these conditions. The equation is applied to geologically important species, H2, N2, CO, CO2, and CH4, at pressures greater than 1 kbar. The results are compared with existing purely empirical equations and clearly demonstrate the superiority of the proposed equation over the empirical ones.