bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics and Absolute Cross Sections of Some Hot Hydrogen Atom Reactions
Authors: Kleinermanns K. , Wolfrum J. 
Published: July 2012

AbstractThe dynamics of chemical reactions with high threshold energies is studied by combining hot atom production by laser photolysis and fast and state selective product detection by laser induced fluorescence. — The nascent OH rotational, vibrational and fine structure (λ‐doublet and spin‐doublet) state distributions produced in the reactions

have been measured at collision energies up to 240 kJ/mol (C.M.‐system) with hot H atoms from the Excimer laser photolysis of HJ, and HBr at 193 nm and 248 nm. Absolute reaction cross sections have been obtained by measuring reactant and product densities at short times. Polarization experiments with photolysis‐ and probelaser polarized parallel and perpendicular to each other are performed. — For the reaction H + O2, the experimental results are compared with extensive trajectory calculations on an ab initio potential surface (Melius, Blint 1979).
Rotational Polarization of Product Molecules: Crossed Laser‐Molecular Beam Studies of Ca* + HF and Ca + F2
Authors: Engelke F. , Meiwes‐Broer K. H. 
Published: July 2012

AbstractQuantitative results have been obtained for the alignment, due to chemical reactions under single collision conditions, in CaF(X) product molecules using the technique of laser‐induced fluorescence (LIF). We find that the anisotropic distribution of angular momenta is of the form 1 + A2P2(cosv), where the alignment appears to be large (A2 = ‐ 1.82 ± 0.06) for Ca* + HF → CaF + H, while for Ca + F2 → CaF + F a considerably smaller alignment (A2 = ‐0.14 ± 0.09) is measured and discussed.
Reactions of CHF (X̃ 1A') and NCO (X̃ 2Π) Radicals
Authors: Cookson J. L. , Hancock G. , Mckendrick K. G. 
Published: July 2012

AbstractInfrared multiple photon dissociation has been used to produce ground state radicals CHF(X̃ 1A') and NCO (X̃ 2Π), and their kinetic behaviour in the presence of added gases studied by time resolved laser induced fluorescence. Both kinetics and the products of reactions of CHF with NO, NO2, O and N atoms, and of NCO with NO will be discussed.
Solubility of Hydrogen in Titanium Alloys. II. Blocking Models and Hole Size Considerations
Authors: Mrowietz Michael , Weiss Alarich 
Published: July 2012

AbstractAssuming a geometrical model with mutual (H‐H) blocking, for hydrogen dissolved in titanium and titanium alloys experimental data are compared. It is found that interstitial sites with pure titanium coordination only host hydrogen atoms. In alloys with bcc crystal lattices only tetrahedral interstitial sites are occupied, whereas in hep alloys both tetrahedral and octahedral interstitials host hydrogen. A linear relation is found which connects the partial molar absorption enthalpy ΔHOHand the partial molar excess absorption entropy ΔSE, OHat infinite dilution of dissolved hydrogen. The enthalpy of absorption ΔHOHcan be rationalized as a function of interstitial hole size and an optimum hole radius of 47 pm is found for titanium and titanium alloys.
Analysis of Trapping and Recombination Effects in Photoelectrochemical Processes at Semiconductor Electrodes: Investigations at n‐GaAs
Authors: Schröder K. , Memming R. 
Published: July 2012

AbstractFast impedance measurements have shown that reliable flatband potentials of GaAs can only be obtained using high scan rates. Illumination leads to a shift of energy bands at the interface which is interpreted by hole trapping in surface states. A recombination conductance determined by impedance measurements is used to characterize the recombination of minority carriers injected by light or a redox system. A semiquantitative model is discussed according to which the recombination occurs mainly in the space charge region of the semiconductor.
Potential Distribution and Interaction between two Parallel Dielectric Cylinders in a Static Transverse Field. I
Authors: Schlögl Reinhard W. 
Published: July 2012

AbstractAt first the following potential problem is solved: Two infinitely long cylinders with radii R1, R2 and dielectric constants ϵ1, ϵ2 are placed in a static transverse homogeneous field with an otherwise arbitrary orientation. The interaction between the cylinders is then evaluated. By suitable transformations, solutions are found in closed form in terms of rapidly convergent series. R1 = R2, ϵ1 = ϵ2 is treated as a special case. In very “unsymmetrical” cases (R1 > R2, ϵ1 ϵ2 < 0), unexpected changes of sign of the forces are found, which are due to “image forces”. The results for a static field carry over for alternating fields, provided that dielectric losses do not contribute significantly.
Solubility and Diffusion of Chlorine in Silica Glass
Authors: Hermann Wilhelm , Rau Hans , Ungelenk Joachim 
Published: July 2012

AbstractChlorine diffusion profiles in silica glass have been studied by SEM techniques. From the results the diffusion coefficient D (log10(D·cm−2 s) = −11080 K/T −3.498), the equilibrium solubility of Cl in silica glass (0.25 or 0.32 weight per cent at 1 bar Cl2 pressure and 1438 K or 1970 K), and the pressure dependence of the solubility were derived. The latter is proportional to the fourth root of the CI2 pressure. There are no detectable differences in the behaviour of chlorine in silica made by the PCVD method (plasma activated chemical vapour deposition) or in commercially produced silica (HERALUX, wave guide quality), but the chlorine concentration is much higher in PCVD silica than expected from the small chlorine pressures present during deposition.
Periodic Operation of a Stirred Flow Reactor with Limit Cycle Oscillations
Authors: Taylor T. W. , Geiseler W. 
Published: July 2012

AbstractThe oscillating flow reaction of bromate, bromide, and cerous ions was investigated computationally in a continuously stirred tank reactor (CSTR) where periodic perturbations were imposed on either the input rate or one of the inflow concentrations. The model computations predict a variety of interesting phenomena such as harmonic and subharmonic entrainment, chaos, transient behavior, and low amplitude harmonics. Under certain conditions the natural oscillations of the system can be considerably damped or enhanced by perturbation inputs of the proper frequency. The theoretical behavior of the system, studied under various experimental conditions, suggests many feasible experiments which are interesting in themselves, but may also serve as an additional probe of the complex mechanism used.
Fluid Phase Equilibria of Binary Mixtures of SF6 with Octane, Nonane, Hendecane, and Decahydronaphthalene,cis at Temperatures between 280 K and 440 K and at Pressures up to 140 MPa in Comparison to Mixtures of Hydrocarbons with CO2, CF4, and CHF3
Authors: Matzik I. , Schneider G. M. 
Published: July 2012

AbstractBinary mixtures of SF6 + octane, + nonane, + hendecane, and + decahydronaphthalene,cis were investigated up to 140 MPa. Measurements were performed according to the synthetic method using an optical high pressure cell. ‐ Going from SF6 + octane to SF6 + nonane the critical p(T)‐curves show a continuous transition between the type of liquid‐liquid (ll) phase equilibrium with upper critical solution temperatures (UCST) and the gas‐gas (gg) equilibrium of the 2nd kind. For the SF6 + n‐alkane systems there is a systematical shift of the high‐pressure branches of the critical curves of about 20 K to higher temperatures per CH2‐unit. The experimental results are discussed in comparison to computer calculations with two semiempirical equations of state. Solvent properties of SF6 are compared to those of CO2, CF4, and CHF3.
Observation of Entrainment, Quasiperiodicity and Chaos in Glycolyzing Yeast Extracts under Periodic Glucose Input
Authors: Markus Mario , Müller Stefan C. , Hess Benno 
Published: July 2012

AbstractEntrained, quasiperiodic and chaotic oscillations are observed by monitoring the fluorescence of NADH in glycolyzing baker's yeast under sinusoidal glucose input flux. These dynamic processes occur in the ranges of input amplitude and frequency predicted by numerical analysis of a two‐enzyme glycolytic model. Entrained responses having periods equal to 1, 2, 3, 4, 5, 7 and 9 times the input period were measured. Stroboscopic transfer plots obtained from the measured quasiperiodic and chaotic oscillations match well with the numerical calculations.
Macromolecular Evolution: Dynamical Ordering in Sequence Space
Authors: Eigen Manfred 
Published: July 2012

AbstractEvolution of self‐replicating macromolecules through natural selection is a dynamically ordered process. Two concepts are introduced to describe the physical regularity of macromolecular evolution: sequence space and quasi‐species. Natural selection means localization of a mutant distribution in sequence space. This localized distribution, called the quasi‐species, is centered around a master sequence (or a degenerate set), that the biologist would call the wild‐type. The self‐ordering of such a system is an essential consequence of its formation through self‐reproduction of its macromolecular constituents, a process that in the dynamical equations expresses itself by positive diagonal coefficients called selective values. The theory describes how population numbers of wild type and mutants are related to the distribution of selective values, that is to say, how value topology maps into population topology. For selectively (nearly) neutral mutants appearing in the quasi‐species distribution, population numbers are greatly enhanced as compared to those of disadvantageous mutants, even more so in continuous domains of such selectively valuable mutants. As a consequence mutants far‐distant from the wild‐type may occur because they are produced with the help of highly populated less‐distant precursors. Since values are cohesively distributed, like mountains on earth, and since their positions are multiply connected in the high‐dimensional sequence space, the overpopulation of (nearly) neutral mutants provides guidance for the evolutionary process. Localization in sequence space, subject to a threshold in the fidelity of reproduction, is steadily challenged until an optimal state is reached. The model has been designed according to experimentally determined properties of self‐replicating molecules. The conclusions reached from the theoretical models can in turn be used to construct machines that provide optimal conditions for the evolution of functional macromolecules.
Noise Induced Limit Cycles of the Bonhoeffer‐Van der Pol Model of Neural Pulses
Authors: Treutlein Herbert , Schulten Klaus 
Published: July 2012

AbstractThe effect of additive noise on the Bonhoeffer‐van der Pol (BvP) model is studied. For this purpose we developed a numerical algorithm to solve the pertinent 2‐dim. Fokker‐Planck equation. The results demonstrate that the global behaviour of the system is determined by certain lines toward which the distribution function is attracted. These lines are also the seeds for the limit cycle in the deterministic system. The noisy BvP model exhibits a limit cycle (oscillations) even when the deterministic system does not. This behaviour may explain the firing pattern of neurons.
A Low‐Pressure Extension of the Stokes‐Einstein Relationship
Authors: Hippler H. , Schubert V. , Troe J. 
Published: July 2012

AbstractAn empirical relation between diffusion coefficients and viscosities is proposed which interpolates between the kinetic theory of dilute gases and the Stokes‐Einstein equation of liquids. This extended Stokes‐Einstein‐relationship is tested with experimental examples. It is useful for studies of reaction processes over large density ranges.
Laser Flash Induced Charge Carrier Transfer in Polycrystalline n‐TiO2 Semiconductors
Authors: Hartig K. J. , Grabner G. , Getoff N. , Popkirov G. , Kanev St. 
Published: July 2012

AbstractPhotocurrent and photovoltage transients have been measured at n‐TiO2 electrolyte junctions by means of ns‐laser pulse excitation. Two different kinds of build‐up, independent of excitation intensity and external resistance have been observed. It is concluded that the charge carrier transit through the depletion layer is the rate determining step if traps or grain boundaries of the microcrystals acting as such, play a significant role. The result is a longer rise time of either photocurrent or ‐voltage, which exceeds the laser pulse width by orders of magnitude.
Electrochemical Study of the Mechanism of Photoreduction of Silver Ions at a Zinc Oxide Surface
Authors: Tanemura H. , Yonezawa Y. , Hada H. 
Published: July 2012

AbstractThe electrochemical behavior of ZnO sinter electrode has been investigated in order to clarify the mechanism of photoreduction of Ag+ on a ZnO surface in aqueous solutions. The flat‐band potential of ZnO electrode depends on the Ag+ concentration. From the stationary polarization curves of the electrode in the dark and under irradiation, we have determined the zero‐current potential, Ezcp, at which total current under irradiation is zero, and the cathodic current at this potential, idzcp. It has been shown that the greater part of idzcp contributes to the photoreduction of Ag+. We could obtain the general expressions for the dependences of Ezcp, idzcp, and the quantum efficiency of idzcp, Φhv, on the Ag+ concentration, which are able to explain the essential features of our experimental findings.
Inelastic Neutron Scattering and Far IR Spectroscopy of Acetonitrile in Solid Ar and CCl4 Matrices
Authors: Langel Walter , Kollhoff Helmut , Knözinger Erich 
Published: July 2012

AbstractInelastic neutron scattering has been applied for the first time to the study of matrix isolated species whose thermodynamically stable phase under normal conditions is the liquid. The aims of these investigations, which are complemented by far infrared studies, are to explore the aggregational behaviour of acetonitrile and the intermolecular dynamics of the respective aggregates in low temperature matrices of solid Ar and CCl4. The only aggregate observed, using a variety of different spectroscopic techniques and diverse experimental conditions, is an antiparallel dimer. In contrast to the external intermolecular modes of this aggregate, which were not accessible by vibrational spectroscopy, the internal modes could be described and assigned.
Charge Transfer from the n‐Hexadecane Radical Cation to Cycloalkanes, Alkenes and Aromatics
Authors: Mehnert R. , Brede O. , Naumann W. 
Published: July 2012

AbstractCharge transfer from n‐hexadecane radical cations C16H+34 to solutes as cycloalkanes, alkenes and aromatics was studied by pulse radiolysis. Using ion‐pair kinetics the rate constants ks of the electron transfer reactions
equation image
were determined. The electron transfer rate constants ks increase from low values for slightly exothermic reactions to a limiting value of 9 · 109 dm3 mol−1 s−1 when the electron transfer reaction is more exothermic than −0.4 eV.
Small Angle Neutron Scattering on Nematic Lyotropic Liquid Crystals
Authors: Herbst L. , Hoffmann H. , Kalus J. , Reizlein K. , Schmelzer U. , Ibel K. 
Published: July 2012

AbstractA solution of 30% by weight of the tetramethylammonium salt of the perfluorononanoic acid (TMPFN = C8F17COON(CH3)4) in D2O forms a nematic phase in the temperature range between 32 and 37°C. The nematic phase was aligned and cooled down to 25°C in a magnetic field of 1.63 and 1.26 T. The structure of the aligned sample was studied with small angle neutron scattering (SANS) at different temperatures. In the liquid crystalline phase first and second order Bragg‐peaks were observed. This phase consists mainly of liquid crystals build by sheets of disk‐like TMPFN micelles alternating with layers of D2O. The lattice parameter is around 75 Å at 25°C. An order parameter S near 1 was determined by a thorough analysis of a rocking experiment. Besides the Bragg‐peaks further scattering features were observed: A Debye‐Scherrer like ring probably related to disclike micelles and a ridge related to a unknown aligned structure. The SANS‐pattern was examined in an temperature range between 25 and 45°C.
Information Theoretical Approach to the Excess Entropy of Liquid Mixtures
Authors: Bär Hans‐Jürgen , Brickmann Jürgen 
Published: July 2012

AbstractA new approach to treat the problem of excess entropies of liquid mixtures on the basis of probability measure functions (PMF) is introduced. In this the excess entropy is proportional to the entropy deficiency where the molar fractions are interpreted as probabilities. It turns out that the PMF's can be easily linked to macroscopic activity coefficients of the constituents in the mixture. On the other hand, first ideas on the microscopic structure can be directly obtained from these new quantities.
Kinetics of the Reactions between CH2(X̃3B1)‐Radicals and Saturated Hydrocarbons in the Temperature Range 296 K ≤ T ≤ 707 K
Authors: Böhland T. , Dõbẽ S. , Temps F. , Wagner H. Gg. 
Published: July 2012

AbstractThe reaction between CH2‐radicals in their ground electronic state (X̃3B1) and n‐hexane
equation image
was studied in a discharge flow system with LMR detection of CH2. In the temperature regime 413 K ≤ T ≤ 707 K the experimental rate constant was found to be
equation image
The reaction proceeds both via direct H‐atom abstraction by CH2(X̃) and via thermal excitation of CH2(X̃) to the low‐lying singlet state (ã1A1) followed by fast consecutive reactions of CH2(ã). The contributions due to thermal excitation and singlet reaction were evaluated for the present work as well as for a recent study of the reactions of CH2(X̃) with a series of other hydrocarbons. Corrected rate constants kT for the direct reactions of CH2(X̃) with the reactants HR = CH4 (1), C2H6 (2), C3H8 (3), n‐C6H14 (4), i‐C4H10 (5), and CH3CHO (6) in the temperature range 296 K ≤ T ≤ 707 K were found to be
equation image
The activation energies for the reactions studied are described by an Evans Polanyi type relation. Arrhenius expressions are proposed for the rate constants of H‐atom abstraction by CH2(X̃3B1) from primary, secondary, tertiary, and aldehydic C ‐H bonds. The results are compared to the isoelectronic reactions of O(3P).
On the Physical Crosslinking of Amine‐Extended Polyurethane Urea Elastomers: A Crystallographic Analysis of Bis‐Urea from Diphenyl Methane‐4‐Isocyanate and 1,4‐Butane Diamine
Authors: Born L. , Hespe H. 
Published: July 2012

AbstractThe substance under investigation is taken as a model for hard segments consisting of diphenylmethane‐4,4′‐di‐isocyanate (MDI) and 1,4‐butane diamine. It crystallizes in the triclinic space group P1 with a = 4.6297; b = 5.8259; c = 25.286 A; α = 90.721; β = 91.580; γ = 102.90 degrees and Z = 1. Bond distances and angles are given, together with some data on the conformation. — The most significant finding is that neighbouring molecules in one and the same plane are linked to one another by means of bifurcated hydrogen bonds. — A comparison with the corresponding data for an analogous bis‐urethane provides a plausible explanation of the main differences between diamine and glycol extension in polyurethane elastomers.
Structural Models for Some Liquid Crystalline Cellulose Derivatives
Authors: Vogt U. , Zugenmaier P. 
Published: July 2012

AbstractModels for helicoidal cholesteric structures are proposed for some cellulose derivative/solvent systems. The pitch of these structures is determined by independent methods as a function of temperature, concentration, solvent, degree of polymerization. The results are discussed on the basis of available theoretical considerations.
Effect of Interfacial Polarization on the Critical Behaviour of Electrical Resistivity and Dielectric Constant in Polar + Nonpolar Binary Liquid Mixtures
Authors: Gunasekharan M. K. , Guha S. , Vani V. , Gopal E. S. R. 
Published: July 2012

AbstractThe dielectric constant ϵ and the resistance R have been measured as a function of frequency in the region 1 kHz to 1 MHz. The measurements have been performed on two critical binary liquid mixtures cyclohexane + methanol and carbondisulphide + acetonitrile in the one phase region. The measurements are carried out using a double ratio transformer bridge, in a bath with millidegree temperature control. At low frequencies ϵ and R increase with T → Tc+. Above 100 kHz the resistance reaches a maximum and begins to decrease as T → Tc+. The observed behaviour is explained qualitatively on the basis of interfacial polarization mechanisms (IPM) using the ideas of the droplet model theory of binary Liquid mixtures. The analysis of the low frequency data using the functional form R or ϵ ˜ tθ shows a value of θ near 0.9. The high frequency data have been analysed with a new functional form, but the quantitative discussions of the IPM are hampered by the lack of information of its dependence upon t.
Structural Phase Transition in Orthorhombic and Monoclinic Fe3+ Doped K3Co(CN)6 Crystals as Studied by the Temperature Variation of 14N NQR Frequencies
Authors: Fukada Shin‐Ichi , Horiuchi Keizo , Asaji Tetsuo , Nakamura Daiyu 
Published: July 2012

AbstractThe temperature dependence of 14N NQR frequencies was observed for Orthorhombic crystals of K3[Co(1‐x)Fex(CN)6] (x ∼ 0.02) and monoclinic crystals of K3[Co(1‐x)Fex(CN)6] (x · 0.005). The former crystals yielded two pairs of vI and vII frequencies above 84 K indicating the existence of at least two crystallographically nonequivalent nitrogens. Below 84 K, each line split into two, the average frequency of which increases smoothly with decreasing temperature without showing discontinuity in frequency itself and also its temperature derivative at 84 K. This can be regarded as that the crystal undergoes a structural phase transition of second order at 84 K which agrees fairly well with the previously reported temperature. The mechanism of the phase transition is interpreted in terms of softening of a translational mode of the anions and/or cations. For the monoclinic crystals, a structural phase transition was located at 65 K in agreement with the reported value.
Electronic and Thermodynamic Properties of the Liquid TIAgTe System
Authors: Uemura O. , Sekiya T. , Ishikawa H. , Satow T. 
Published: July 2012

AbstractThe electrical conductivity, the magnetic susceptibility, and the thermoelectric power of the liquid TI‐AgTe system have been obtained as functions of temperature and composition. The thermodynamic properties of the system have also been determined by means of the EMF method. The system shows a sharp minimum in electrical conductivity and a marked maximum in diamagnetic susceptibility at the stoichiometric composition of AgTlTe, where the change in sign of thermoelectric power also appears. These electronic properties are discussed in the light of current transport theories employed in the amorphous and liquid semiconductors. Further, the presence of the local order around the stoichiometric composition in the system is discussed by the support of the results of thermodynamic properties.
Modification of the Electric Double Layer Properties of the Interface Mica/Aqueous Solution by Adsorption of Polyelectrolytes
Authors: Wehn R. , Woermann D. 
Published: July 2012

AbstractMeasurements of streaming potentials with an rectangular channel formed by two mica plates and spacers are used to study (a) the properties of the electric double layer at the interface mica/aqueous alkali chloride solution and (b) modifications of these properties by adsorption of polyelectrolytes (poly‐4‐vinyl‐pyridinium bromide, heparine, poly‐vinyl sulfate). The results obtained for the unmodified