bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonequilibrium Phase Transitions in Solid Catalysts for Oxidation
Authors: Greger M. , Riekert L. 
Published: March 2014

AbstractNonequilibrium phase transitions in oxidation catalysts follow either one of two distinct patterns. The system CuO/Cu2O—C3H6+O2exemplifies the pattern of hysteresis. The influence of catalyst preparation on this pattern at 645 K is investigated as well as the influence of the presence of small amounts of Pd. The system Ni/NiO—H2+O2exemplifies the pattern of coexistence of two phases of the active component, which in this case coexist by alternating in time.
Plancks Strahlungsgesetz und die Quantisierung der Entropie
Authors: Zimmermanc Herbert W. 
Published: March 2014

AbstractIn order to derive Planck's law of black‐body radiation we consider a gas of photons which is in equilibrium with its surroundings at temperature T. Instead of the usual energy quanta of the photons ε = hv we introduce entropy quanta σ = ε/T. Now, ε and T are used from the beginning of the calculations and it is easy to derive Planck's distribution law of the photon gas, avoiding Lagrange's method of undetermined multipliers. Using ε instead of ε we get the entropy‐distribution of the black‐body radiation which may be transformed by ε = hv into the usual energy‐distribution formula. Conventionally, entropy is a property of an ensemble of particles. But the entropy quantum ε is a property of the particle itself which is in thermodynamic equilibrium with its surroundings.
Study of the System Nitrobenzene/Isooctane in the Vicinity of its Critical Point: Static and Dynamic Light Scattering and Reevaluation of Ultrasonic Absorption Data
Authors: Belkoura L. , Harnisch F. P. , Kölchens Silvia , Müller‐Kirschbaum Th. , Woermann D. 
Published: March 2014

AbstractStatic and dynamic light scattering measurements with nitrobenzene/isooctane mixtures of critical composition in combination with measurements of temperature dependence of specific heat and density are used to obtain values of parameters appearing in the Ferrell‐Bhattacharjee theory of ultrasound absorption of binary critical mixtures (σ0: characteristic temperature independent relaxation rate, ω0 = (43.8 ± 0.7) GHz; g: coupling constant, g = – (0.56 ± 0.01). Recent ultrasound absorption data of that system are reanalysed on the basis of Ferrell‐Bhattacharjee theory. The analysis of data measured at seven frequencies of ultrasound in the range 9 MHz to 45 MHz gives values of the parameters ω0 and g which are in satisfactory agreement with those obtained from light scattering and thermodynamic measurements (ω0 = (37 σ 3) GHz; lgl = 0.5).
Properties of Polar Gases and Their Dimer Structures
Authors: Ksiąz̊czak Andrzej , Anderko Andrzej 
Published: March 2014

AbstractA method for predicting dimerization constants in the gas phase using vapour pressure data is presented. The probable dimer structures of polar compounds such as aldehydes, ketones, esters, nitrocompounds, nitriles and heterocyclic compounds are discussed. The dimerization constants are employed to predict virial coefficients, heat capacity and thermal conductivity. The predicted values are in good agreement with experimental data.
Nuclear quadrupole resonance of substituted anilinium halides. 127I and 79Br NQR studies of toluidinium and para‐phenylenediammonium halides
Authors: Hartmann Jutta , Weiss Alarich 
Published: March 2014

AbstractThe 79,81Br and the 127I NQR frequencies of several bromides and iodides of ring substituted anilines were studied in the range 77 ≦ T/K < decomposition temperature. Phase transitions have been observed for 2‐(CH3)C6H4NH⊕3 Br⊖ at T = 83 K, for 3‐(CH3)C6H4NH⊕3I⊖ at 145 K and for [1,4‐(H3N)2C6H4]2⊕ [I]2⊖2 at 139 K. Transitions do not occur in [1,4‐(H3N)2C6H4]2⊕ [I]2⊖2, 2‐(H3N)2C6H4I2⊕ [I]2⊖2, 3‐(H3N)2C6H4I2⊕ [I]2⊖2, 2,4‐(H3N)2C6H4I2⊕ [I]2⊖2, 2,4‐(H3N)2C6H4I2⊕ [I]2⊖2 and 3‐(H3N)2C6H4I2⊕ [I]2⊖2. The results are discussed in the light of known crystal structure data and they are compared with studies on other anilinium halides.
Fluorescence studies of excited state intramolecular proton transfer (ESIPT) in molecules isolated in solid argon: 3‐hydroxyflavone and 2,5‐bis(2‐benzoxazolyl)hydroquinone
Authors: Dick Bernhard 
Published: March 2014

AbstractThe fluorescence properties of 3‐hydroxyflavone and 2,5‐bis(2‐benzoxazolyl)hydroquinone have been investigated in solid argon matrices at 15 K. In both cases dominant emission from the tautomeric form of the molecules is observed. The excitation spectra of this fluorescence and a weak fluorescence at shorter wavelength show that the latter is due to molecules with a different ground state, presumably dimers or conformers lacking an internal hydrogen bond. For both molecules no fluorescence from the normal form is found indicating the absence of a barrier to excited state intramolecular proton transfer (ESIPT).
Photochromism of spirooxazines I. Investigation of the primary processes in the ring‐opening reaction by picosecond time‐resolved absorption and emission spectroscopy
Authors: Schneider S. , Mindl A. , Elfmger G. , Melzig M. 
Published: March 2014

AbstractThe heterolytic bond cleavage between the spiro‐carbon and the neighbouring oxygen is commonly accepted as the primary photochemical step after exciting indolino‐spirooxazines with UV‐photons. The nonplanar intermediate “X” generated in this way is said to relax very fast to a distribution of open forms, which are in structure similar to merocyanines. In this paper, the existence of an intermediate “X” is proven for various derivatives of indolino‐spironaphthoxazines. The build‐up time of these “X”‐forms is generally shorter than 2 ps, and the following reaction to the planar forms takes 2 to 12 ps depending on the nature of the solvent as well as the kind of substituent added to the parent molecule. In contrast to nitro‐substituted compounds the triplet route is found to be negligible in the investigated derivatives.
NBr (b1Σ+, a1Δ) in solid argon: Effect of the rare gas matrix on radiative and radiationless processes
Authors: Becker A. C. , Schurath Ulrich 
Published: March 2014

AbstractHeterogeneous structure in the laser‐induced b1Σ+ ↔ X3Σ− and a1Δ ↔ X3Σ− fluorescence bands of NBr in solid argon has been assigned to multiple trapping sites. A stacking‐fault model accounts for the spectral observations. Symmetry properties of the trapping sites can be correlated with photophysical properties of the emitter.
Crystal dynamics and phase transitions of malononitrile
Authors: Bougeard D. , Le Calvé N. , Pasquier B. 
Published: March 2014

AbstractThe crystal dynamics of the three phases, α, β and γ of malonitrile are calculated by using atom‐atom potentials from the literature and considering the dipole and quadrupole moments. The experimental frequencies used for comparison are extended by new FIR measurements and low temperature single crystal Raman spectra. The overall agreement obtained is satisfactory. The splitting of some internal modes iu the triclinic β phase is mostly caused by the atom‐atom potential. The form of the calculated soft mode agrees nicely with the values expected from crystallographic data. Finally, the influence of the multipole in the crystal energy is only of the order of 10%.
Nonlinear optical properties of polymeric materials
Authors: Willand C. S. , Williams D. J. 
Published: March 2014

AbstractIn this paper we discuss the molecular and macroscopic requirements for large second order nonlinear optical effects in polymeric systems. A new enhancement mechanism attributable to cooperative interactions between dipoles in polar polymer chains is proposed and tested by the synthesis and characterization of asymmetric condensation copolymers derived from p‐oxy‐α‐cyanocinnimate derivatives. An enhancement of a factor of 20 in electric field induced second harmonic generation relative to an equivalent concentration of chemically identical nonpolymerized chromophores in solution is obtained. Conformational and perhaps alignment restrictions in the rubbery state result in a reduction in alignment relative to what would be expected for an equivalent concentration of the polymerized chromophores in a moderately viscous medium. A model is proposed to account for the enhancement factors.
Phase transition and anionic motion in solid [(CH3)2NH2]2SnCl6 as studied by the temperature dependence of 35Cl NQR frequencies and chlorine nuclear relaxation times determined with a pulsed NQR spectrometer
Authors: Horiuchi Keizo , Ikeda Ryuichi , Nakamura Daiyu 
Published: March 2014

AbstractThe temperature dependence of 35Cl NQR frequencies of [(CH3)2NH2]2SnCl6 was precisely determined between 78 and ca. 250 K. by means of an FT NQR spectrometer. The high‐frequency line of the two 35Cl NQR signals having the intensity ratio of 2:1 already reported was observed to be split below 102 K. into sharp and broad lines with approximately equal integrated intensify. This clearly indicates the occurrence of a structural phase transition of a second‐order nature at this temperature. The presence of phase transition around this temperature has been anticipated from the IR and NQR studies previously done. The temperature dependence of chlorine nuclear spin‐lattice relaxation time, T1Q shows a dip with a clear depression at 102 K. The mechanism of the phase transition is discussed from the T1Q results and the fact that the frequency separation of the doublet increases with decreasing temperature. Above 180 K, T1Q of both lines decreased rapidly and the log T1Q vs. T−1 curves were almost linear. This decrease of T1Q was explained through the onset of the C4 reorientation of the anions with the activation energy of ca. 35 kJ mol−1. The fade‐out phenomenon of the two NQR lines occurring far below room temperature can be well explained by the onset of the above motion with the very low activation energy.
Photochemistry of colloidal semiconductors 24. Interparticle electron transfer in Cd3P2—TiO2 and Cd3P2—ZnO sandwich structures
Authors: Spanhel Lubomir , Henglein Arnim , Weller Horst 
Published: March 2014

AbstractColloidal solutions of Q‐Cd3P2 of different particle size were illuminated with visible light. The solutions also contained colloidal TiO2 or ZnO. The fluorescence of Cd3P2 was quenched by the oxide colloids. The rate of the photo‐anodic corrosion in aerated solution was drastically increased by TiO2, the quantum yield being 0.7. These effects are explained in terms of improved charge separation by rapid electron transfer from illuminated Cd3P2 into the conduction band of TiO2 or ZnO particles that are bonded to the Cd3P2 particles. — Electron injection into ZnO was more efficient for Q‐Cd3P2 particles of smaller size. This is attributed to the shift of the conduction band to more negative potentials in these particles. The injected electrons caused a blue‐shift of the absorption threshold of the ZnO part of the Cd3P2—ZnO sandwich structure.
Ionisation and dissociation of diarylmethyl chlorides in BCl3/CH2Cl2 solution: Spectroscopic evidence for carbenium ion pairs
Authors: Schneider Reinhard , Mayr Herbert , Plesch Peter Hl 
Published: March 2014

AbstractThe ionisation equilibria of diarylmethyl chlorides Ar2CHCl (Ar = p‐CH3O‐C6H4, p‐PhO‐C6H4, p‐CH3‐C6H4 reacting with BCl3 in CH2Cl2 to give ion‐pairs Ar2CH BCl−4 (KI), and the dissociation of these (KD) were studied by conductimetry and spectro‐photometry. The molar conductivities are almost independent of the nature of the aryl group (3.5 · 10−3 Sm2/mol at — 70°C). The ionisation constants KI increase strongly with increasing electron releasing ability of the p‐substituents. The standard ionisation enthalpies and entropies for (p‐CH3‐C6H4)2CHCl and (p‐PhO‐C6H4)(Ph)CHCl, calculated from the KI at different temperatures are negative. The dissociation constants KD [(1.9—2.9) · 10−4 mol/L at — 70°C] do not show a systematic dependence on the electron donating abilities of the substituents in the aryl groups. Small differences between the UV‐vis absorption spectra of unpaired and paired ions were used to confirm the conductimetrically determined values of KD.
A New Statistical Model for the Kinetics of the Desorption of Mixtures from Heterogeneous Adsorbing Surfaces
Authors: Liedy W. , Schlünder E.‐U. 
Published: March 2014

AbstractA new model for the desorption kinetics of single substances and of mixtures is developed. The heterogeneity of the adsorbing surface is included in the model. A comparison with experimental data shows, that the new equation can predict the mixture behavior even for a system with strong deviations from ideality.
Electro‐optic and Rheological Behaviour of Aqueous Dispersions of Polytetrafluorethylene (PTFE) Fibrilles
Authors: Angel M. , Hoffmann H. , Huber G. , Rehage H. 
Published: March 2014

AbstractElectro‐optic and rheological measurements were carried out on PTFE‐fibrilles. The crystalline fibrilles had an axial ratio of about 100 and a thickness of 200 Å. The dispersions were stabilized by ionic Perfluorosurfactants and could be kept for months without precipitation. — The rotational diffusion constant of the fibrilles was determined as a function of the volume fraction. Both electric birefringence and rheological measurements gave identical results for the orientation times. In the dilute and semidilute concentration range the rotational diffusion constant was the same and did not change at the overlap concentration. The shear modulus was found to increase in the semidilute concentration with the square of the volume fraction of the PTFE fibrilles. — Electric birefringence measurements with AC‐pulses showed a remarkable result. The stationary birefringence changed sign as a function of the frequency. It is concluded that this phenomenon is related to the adsorption/desorption equilibrium of the surfactant ions on the PTFE fibrilles. The equilibrium is shifted by the electric field. These conclusions could be confirmed by light scattering measurements in AC‐fields.
Pressure Effect on Dimerization Equilibria of a Series of Substituted Nitrosobenzenes in Solution
Authors: Yoshimura Y. , Nakahara M. 
Published: March 2014

AbstractThe effect of pressure was studied on the dimerization reactions of six di‐ and tri‐substituted nitrosobenzenes in carbon tetrachloride at 25°C. The obtained configurational volume changes for the prototype one bond formation reactions are in the range of —17 to —21 cm3 mol−1 at 6.13 MPa. The volume changes were interpreted in terms of the perturbation theory of liquid; they were dominated by the volume change in the reference system composed of hard spheres. Small differences between the observed and theoretical reference volume changes were ascribed to the perturbation due to electrostatic interactions between the solute and solvent; the perturbation volume changes were estimated by the Kirkwood theory of dipolar solvation.
Description of Three Phase Systems and Liquid‐Liquid Equilibria at High Pressures on the Basis of a Mean‐Field Lattice‐Gas Model
Authors: Kajtor J. , Peter S. 
Published: March 2014

AbstractThe calculation of phase equilibria in systems with dense supercritical components by means of a method developed by Kleintjens and Koningsveld was investigated. The three phase equilibria (gas, liquid, solid) in the systems H2O/NaCl (18.0—92.0 MPa, 673 — 873 K) and H2O/KBO2 (16.0—70.0 MPa, 670—771 K) can be successfully represented by using substance specific parameters derived from VLE equilibria. — Also the representation of the liquid‐liquid equilibria in the binary systems of 2‐methoxyethanol with different alkanes, which have upper critical solution temperatures and lower critical solution pressures in the temperature range 250 — 430 K and at pressures from 0.1 —400 MPa can be achieved.
UV/VIS‐Spectroscopic Studies of Cold Condensed Metal/Metal Halide Films With and Without Matrix‐Isolation
Authors: Gottwald Helmut , Weil Konrad G. 
Published: March 2014

AbstractFilms of about 200 nm thickness were prepared by vacuum deposition of the halides onto fused silica windows, which were kept at 12 K by a closed cycle helium refrigerator. AgCl, CuCl, and TlCl films showed an structureless absorption edge which extended from about 350 nm to 200 nm. Annealing of the films below 170 K (150 K in the case of CuCl) for more than two hours gave no changes in the absorption spectra. Films which were annealed above this temperature showed at 12 K the exciton bands which are characteristic for the crystalline state of the materials. — Cocondensation of 1 to 30 mol% of metal Me to the halide MeCl gave rise to a broad absorption band around 300 nm which can be assigned to a surface plasmon excitation of small particles. When the films are annealed, these bands disappear simultaneously with the crystallization of the matrix, and a broad band between 400 and 500 nm is formed. We assume that this band is due to Mie scattering of metallic colloid particles. — The non‐crystalline state apparently is a metastable ionic glass phase. ‐Silver chloride, matrix isolated in Ar or Kr matrices on LiF windows shows an UV/VIS spectrum which is different from the gas spectrum. No new bands appear when it is cocondensed with silver atoms.
Spectroscopic Investigation (INS, FIR) of Structural Phase Transformations of Ferroelectric CH3NH3HgCl3
Authors: Körfer M. , Fuess H. , Prager M. , Zehnder E.‐J. 
Published: March 2014

AbstractThe mechanism of the structural phase transformation from the ferroelectric room temperature to the paraelectric high temperature phase at T = 333(2) K in methylammonium trichloromercurate (CH3NH3HgCl3 and CD3NH3HgCl3) was investigated by inelastic neutron scattering and FIR‐measurements. Energies for an internal torsional mode of CH3 (ΔE(CH3) = 13.7 meV) and an external librational mode of NH3 (ΔE(NH3) = 37.2 meV) are derived from the inelastic part of neutron time of flight spectra. The evaluation of the quasielastic intensity revealed a jump rotation at T ≈ 100 K and a rotational diffusion at T ≈ 295 K for the CH3NH⊕3‐group around the C —N axis. For CH3− this rotational diffusion still exists in the paraelectric phase. It is, however, strongly reduced for NH⊕3 at the phase transition where an end over end libration for the whole CH3NH⊕3‐group is activated. The FIR and neutron fixed window studies give some indications of two further phase transitions at T ≈ 20 K and T ≈ 120 K.
Über die Quantisierung der Entropie und die Verteilungsfunktionen von Boltzmann, Bose‐Einstein und Fermi‐Dirac
Authors: Zimmermann Herbert W. 
Published: March 2014

AbstractIn a foregoing communication the concept of quantization of entropy has been introduced to derive Planck's law of black‐body radiation. In the following it is extended from photons to non‐relativistic particles. — We consider an ensemble of N particles with the total energy U which is the sum of the particle energies ε. The particles are in equilibrium with their surroundings at temperature T. In order to derive the distributions of Boltzmann, Bose‐Einstein, and Fermi‐Dirac we introduce the entropy quantum σ = ε/T which is a property of the particle itself. Again, ε and T are used from the beginning of the calculations and the distribution functions can be derived avoiding Lagrange's method for constrained maximum. Conventionally, the maximum of the entropy S for N = const, and U = const, describes the thermal equilibrium of the particle system. Instead we use the condition that the entropy quanta σ = ε/T of all particles have the same temperature T. Employing conventional particle statistics the concept of quantization of entropy leads to the same distribution functions as ordinary statistical thermodynamics, but in an easier manner.
The Shear Viscosity of Liquid Hg Based Alloys Containing In
Authors: Nozaki M. , Morikawa Y. , Itami T. , Shimoji M. 
Published: March 2014

AbstractThe shear viscosity η was measured as a detailed function of composition for liquid Hg based alloys containing 0–16 at% In in the temperature range from 320 K. to 520 K. A capillary viscometer of the Ostwald type was used for measurements. — The η increases linearly with the addition of In. This concentration dependence could be well explained by a simple hard sphere theory for η of liquid mixtures, in which the correction of back scattering took an important role. — The isothermal curves of ∂η/∂Tshow a slight depression at a few at% In, particularly at lower temperatures. This phenomenon appears to be related to higher order correlation (HOC) effects, which have been proposed recently for some liquid Hg based alloys by the present authors.
Electronic Transport in Molten Salt Rich Na — NaX Solutions (X = Br, I)
Authors: Haarberg G. M. , Osen K. S. , Egan J. J. , Heyer H. , Freyland W. 
Published: March 2014

AbstractThe electronic conductivity of liquid Na—Nal and Na—NaBr has been measured over a wide concentration range from dilute to concentrated nonmetallic solutions at different temperatures between 700 and 900°C. Two methods have been applied, the Wagner polarization technique at low metal activities and an ac‐technique at high activities where the concentration has been varied by coulometric titration. A thermodynamic defect model previously used for solids is developed and extended to liquid solutions. It quantitatively describes the concentration and temperature dependence of the thermodynamic properties as well as the charge carrier concentration in these nonmetallic systems. The electronic mobility has been determined and the transport mechanism approaching the nonmetal‐metal transition is discussed.
23Na MAS‐NMR and 1H MAS‐NMR Studies in the Hydro‐Sodalite System
Authors: Buhl J.‐Ch. , Engelhardt G. , Felsche J. , Luger S. , Foerster H. 
Published: March 2014

AbstractThe basic (x = 2, n = 4), (x = 2, n = 0) and the non‐basic (x = 0, n = 8), (x = 0, n = 0) species of the hydrosodalite system Na6+x[AlSiO4]6(OH)x · nH2O have been studied by 23Na MAS‐NMR and 1H MAS‐NMR techniques at 297 K. The spectra are discussed in terms of structural data, which are provided by X‐ray and neutron diffraction experiments on hydro‐sodalite phases of identical compositions. The 1H MAS‐NMR spectrum of the non‐basic phase Na6[AlSiO4]6 · 8H2O confirms the recent neutron diffraction data. The chemical shift of 4.2 ppm correlates to regular water molecules in the sodalite cage, which show hydrogen bonding to the framework oxygens. The 1H MAS‐NMR double peak spectrum of the basic hydro‐sodalite species Na8[AlSiO4]6(OH)2 · 4H2O correlates with the structural OH groupings (3.4 ppm) and with one proton per ß‐cage (—1.0 ppm) showing a significant magnetic shielding effect. The large diamagnetic shift (—6.5 ppm) of the resonance signal in the 1H MAS‐NMR spectrum of the hydroxy‐sodalite Na8[AlSiO4]6(OH)2 indicates substantial change in the chemical bond of the hydrogen atom upon dehydration of the tetrahydrate Na8[AlSiO4]6(OH)2 · 4H2O at 775 K. — The phases of the non‐basic hydro‐sodalites show 23Na chemical shifts of approximately —8 and —9 ppm for the octahedrally coordinated sodium atoms in the octahydrate (n = 8) and in the anhydrous (n = 0) sodalite, respectively. — The 23Na chemical shifts of the basic sodalites range from —0.6 to —5.6 ppm, and the species reveal considerable quadrupolar interactions. At least two types of sodium ions are registered in basic hydro‐sodalite (n = 4) in accordance with structure analysis.