bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical Study on the Molecular Geometries of Substituted Fluoroforms
Authors: Kiss Árpád I. , Hargittai István 
Published: February 2015

Abstract
The F…F non-bonded distances are strikingly constant in a large series of trifluoromethyl derivatives. Semiempirical NDDO calculations have been performed for five representative molecules. From the energy partitioning it appears that the bonding interactions (resonance energy terms) are dominating in determining the molecular geometry. The constancy of the non-bonded distances may occur as the changes in the bond lengths and bond angles are compensated. A good description of the total energy, however, necessitates the inclusion of the two-center electrostatic terms of all atom pairs.
Class Specific Physical Properties of Liquid Crystals and Correlations with Molecular Structure and Static Electrooptical Performance in Twist Cells
Authors: Schadt M. , Gerber P. R. 
Published: February 2015

Abstract
We made measurements of the temperature dependence of the static dielectric constants, the optical anisotropy and the three elastic constants of binary mixtures belonging to twelve structurally and physically markedly different liquid crystal classes. The class-specific material properties were quantitatively correlated with molecular structural elements. The changes of material properties occurring when different LC-classes are combined were investigated. Analytical approximations are presented which are shown to reproduce the static transmission characteristics of twisted nematic cells and their dependence on material constants and temperature with an accuracy comparable to exact numerical calculations. Strong smectic pretransitional effects are shown to influence not only k22 and k33 but also k11, thus suggesting that not only twist and bend but also splay deformations may be prohibitive in smectics. We show that the elastic ratio &33/&11 of different liquid crystal classes increases with increasing dielectric anisotropy thus leading to a decrease of the slope of transmission characteristics of twist cells. Furthermore, it is shown that k33/k11 decreases for molecules comprising heterocyclic rings whereas hydrogenation of an aromatic ring causes k33/k11 to increase.
Viscous Properties and Dynamic Electrooptical Performance in Twisted Nematic Displays of Several Liquid Crystal Classes
Authors: Gerber Paul R. , Schadt M. 
Published: February 2015

Abstract
The temperature dependence of the rotational viscosities of several physically markedly different binary mixtures belonging to ten different liquid crystal classes is measured. An attempt is made to correlate the results with class-specific structural properties such as hydrogenated rings, molecular polarity and structure of flexible side-chains. It is show that the measured small-scale dynamic properties of twist cells compare well with approximative theoretical calculations and experimentially determined class-specific material parameters. For the switching times corresponding to large-scale twist deformations heuristic approximations lead to satisfactory results.
Infrared Band-Shape Studies of Sulphate Glasses
Authors: Sundar H. G. K. , Parthasarathy R. , Rao K. J. 
Published: February 2015

Abstract
IR band-shape analysis has been carried out on the 620 cm-1 deformation band of the sulphate ion in several Na2SO4-K2SO4-ZnSO4 glasses. Variations of correlation times and second moments suggest that reorientational motions of sulphate ions begin to evolve prior to the glass-transition temperature. The correlation times may support a cluster model for the glass-transition.
Topological Resonance Energy of Linear Polyaeenes
Authors: Gutman Ivan 
Published: February 2015

Abstract
A method for computation of the topological resonance energy (TRE) of linear polyacenes is described. When the length of the polyacene chain increases, TRE tends to 0.02 β units per π-electron, contrary to a previous prediction [1]. The ionization potential and the energy of the p-band of linear polyacenes are found to be excellently correlated with TRE.
Low Temperature Vibrational Relaxation of Gaseous CF3Cl, CF3Br, CHF2Cl, and CH3Cl
Authors: Kadibelban R. , Ahrens-Botzong R. , Hess P. 
Published: February 2015

Abstract
Ultrasonic absorption measurements are reported for gaseous CF3Cl, CF3Br, CHF2Cl, and CH3Cl between room temperature and the lower temperatures 163 K, 193 K, 198 K, and 213 K, respectively. Starting from a statistical point of view, the relaxation behavior is divided into three classes, which are associated with the positive, zero, and negative slope in a log(k) versus 1/T plot. On this basis the vibrational relaxation behavior of CF4, CF3Cl, CF3Br, CHF3, CHF2Cl, CH3Cl, NF3, PF3, and BF3 is discussed especially in the critical temperature to boiling point region. This temperature region is used as a reference for comparing different molecules.
Absolute Cross Sections for the Chemiluminescent and Chemiionizing Reactions Mg*(3P), Ca*(3P) + SOCl2
Authors: Kowalski Andrzej 
Published: February 2015

Abstract
The absolute cross sections for different electronic exit channels for the reactions Mg*(3P), Ca*(3P) + SOCl2 were measured in a beam-gas experiment. The chemiluminescence and chemiionization yields measured are low (total 2%) but equal or are even higher for some channels than those calculated from a statistical model.
Variational Calculation of the Lower Vibrational Energy Levels of the Ammonia Molecule
Authors: Bopp Philippe , McLaughlin Don R. , Wolfsberg Max 
Published: February 2015

Abstract
A variational calculation of the lower-lying vibrational energy levels of the ammonia molecule is performed, in which all six vibrational degrees of freedom are treated simultaneously. A literature potential is assumed for all non-inversion motions; a new inversion barrier potential with a barrier of 1616 cm-1 is determined by fitting experimental data.
Spherical Wave Treatment of Laue Case Rocking Curves
Authors: Bonse U. , Teworte R. 
Published: February 2015

A spherical wave theory is given for the calculation of the observed fine structure of Laue case rocking curves [1 - 3] of a pair of perfect crystals.
It is shown that under the experimental condition of measuring simultaneously the full width of outgoing beams, the simple plane wave theory presented previously [1] yields identical results.
A Geometrical Correction for Precise Lattice Constant Determination
Authors: Bradaczek Hans , Leps Bernd , Uebach Wilhelm 
Published: February 2015

A correction term for high precision lattice constant investigations has been derived, which is caused by geometrical and absorption effects. Surprisingly there is no dependence on absorption and extinction in the case of high absorption and/or “infinite” crystal thickness. Only the half width of the rocking curve has to be considered. In the case of low absorption and/or thin crystal, there are terms of higher order which still depend on p.t but can be neglected compared to the main effect.
The main reason for the correction is that the observed rocking curve is the result of a “true” rocking curve multiplied by a geometrical function which is not symmetrical with respect to the rocking angle. For high precision measurements (< 10-5) the application of the correction term is recommended.
Dislocations in Homoepitaxial Layers on "Dislocation Free" LEC-GaP Substrates
Authors: Umeno M. , Kawabe H. , Kokonoi T. 
Published: February 2015

Abstract
Dislocation structures in S-and N-doped homoepitaxial layers on GaP wafers are studied by high voltage electron microscopy. Many dislocations are introduced in the epilayer, even if the substrate is nearly dislocation free. The origins of the dislocations in this case are the microdefects, especially the perfect dislocation loops in the substrate. Dislocation dipoles are induced by dis-location half loops appearing at the epi-substrate interface and are classified into three types, two of which are concerned with the interactions of two dipoles in the epilayer, each interaction yielding a screw dislocation segment. The third type of dipole does not extend into the epilayer so far, but terminates and forms an elongated dislocation loop. The interactions and the terminations of dipoles decrease the density of the induced dislocations in proportion to the distances from the interface. The screw dislocations generated by the dipole interactions relax the torsional lattice distortion of the epilayer caused by dopant materials.
Experimental and Theoretical Studies on X-ray Plane Wave Images of a Dislocation in the Laue Case
Authors: Ishida H. , Miyamoto N. , Ishikawa T. , Kohra K. 
Published: February 2015

Abstract
Plane wave images of a dislocation in a silicon crystal were observed with (4̄04) diffraction of MoKα1 over a wide angular range. The fine structures consisting of five kinds of sub-images and their angular dependences were well simulated by the wave theory taking into account the finite angular spread and polarization states of the incident beam. The mechanism of the image formation is studied in terms of interbranch scattering, Eikonal theory and kinematical diffraction.
Experimentelle und semi-empirische Protonen-Hyperfein- kopplungen von 1.3-Benzodioxol-Radikal-Kationen und ihre Korrelation mit Reaktivitäten in elektrophilen Substitutionen
Authors: Fleischhauer Jörg , Ma Sun , Schleker Wolfgang , Gersonde Klaus , Twilfer Hans 
Published: February 2015

Abstract
The solution ESR X-band spectra of 1.3-benzodioxole (methylenedioxybenzene) (1), benzo- [1.2-d:4.5-d']bis[1.3]dioxole (2), benzo[1.2-d:3.4-d']bis[1.3]dioxole (3) and benzotris[1.3]dioxole (4) have been measured at room temperature. Hyperfine splitting constants of the aromatic ring protons of the compounds 1 - 3 have been determined. They have been correlated with the HOMO orbital densities of the adjacent carbon atoms and exhibit sufficient correspondence with the reactivities of these compounds in electrophilic substitution reactions. The splitting constants of all protons of the compounds 1 - 4 have been calculated by the INDO and HMO methods and have been compared with the experimental hyperfine values. By perturbation theory applied to the interactions between the π-MO'S of benzene and the dioxole fragment one can explain and understand the magnitudes of the experimental hyperfine splitting constants of the hydrogen atoms of these compounds. In particular, the hyperfine values of the methylene protons calculated by the HMO method are in good agreement with the experimental data.
Nuclear Magnetic Relaxation Induced by the Dynamics of Lattice Defects in Solids (7 = 3/2,I=2, and I= 5/2)
Authors: Becker K. D. 
Published: February 2015

Abstract
Results are presented for the relaxation of the nuclear magnetization via quadrupolar inter-actions caused by the dynamics of point-like lattice defects in cubic solids. For systems with nuclear spins I = 3/2, several aspects of the lineshape function of the absorption signal are con-sidered. The treatment includes the transition to the rigid lattice case, the presence of additional static quadrupolar interactions as well as the dynamic shift of the absorption, and saturation effects. For spins I = 2, expressions are given in detail for the parameters governing the relaxa-tion of the longitudinal and the transverse magnetization. For the I = 5/2 case, numerical results are presented for the same quantities accounting for complete and incomplete excitation of the spin system.
Nonlinear Landau Damping of Alfvén Waves in a High β Plasma
Authors: Völk Heinrich J. , Cesarsky Catherine J. 
Published: February 2015

A study is made of the nonlinear damping of parallel propagating Alfvén waves in a high β plasma. Two circularly polarized parallel propagating waves give rise to a beat wave, which in general contains both a longitudinal electric field component and a longitudinal gradient in the magnetic field strength. The wave damping is due to the interactions of thermal particles with these fields. If the amplitudes of the waves are low, a given wave (ω1, k1) is damped by the presence of all longer wavelength waves; thus, if the amplitudes of the waves in the wave spectrum increase with wave length, the effect of the longest waves is dominant.
However, when the amplitude of the waves is sufficiently high, the particles are trapped in the wave packets, and the damping rate may be considerably reduced. We calculate the induced electrostatic field, and examine the trapping of thermal particles in a pair of waves. Finally, we give examples of modified damping rates of a wave in the presence of a spectrum of waves, and show that, when the trapping is effective, the waves are mostly damped by their interactions with waves of comparable wavelengths
Two Photon Ionization of Benzene in Methanol and Cyclohexane Solution
Authors: Tagawa S. , Beck G. , Schnabel W. 
Published: February 2015

Abstract
Irradiation of benzene with 15 ns flashes of 265 nm light caused ionization as evidenced by optical absorption measurements. In the case of dilute methanol solutions solvated electrons were formed. The yield depends on the intensity of the incident light I as ϕ (es̄olv) ∝ I1.8. In the case of cyclohexane solution dimer radical cations were detected by their absorption between 600 and 1100 nm. O2 enhances the yield of dimer cations because it scavenges electrons, thus impeding ion recombination.
Dielectric Behaviour of Ice Microcrystals Dispersed within Suspensions: A DTC Study
Authors: Pissis P. , Apekis L. , Christodoulides C. , Boudouris G. 
Published: February 2015

Abstract
The dielectric properties of water-in-oil (W/O) suspensions have been studied by means of the depolarization thermocurrent (DTC) method in the temperature range of 85-250 K. Two predominant peaks have been observed at about 140 and 225 K. Evidence has been obtained that the peak at 140 K and the dielectric absorption observed by many investigators at sub-zero temperatures in the kHz frequency range are due to the same relaxation mechanism.
Eisenionen als Spinsonden in CdGa2S4-Kristallen / Fe(III) Ions as Spin Probes in CdGa2S4 Crystals
Authors: Frick B. , Siebert D. 
Published: February 2015

Abstract
In EPR studies on Fe(III) ions in CdGa2S4 crystals, in accordance with the two different Ga sites two paramagnetic centers could be detected which differ widely in their axial parameter D. An investigation of the crystal field allowed a unique site assignment. A comparison with the Fe(III) resonances in CuGaS2 and AgGaS2 does show that the superposition model of Newman and Urban cannot be applied to CdGa2S4 with similar parameters as in the chalcopyrite structures. - A characteristic twinning could be revealed, similar to the “reversed cubic structure” in sphalerite.
Nuclear Magnetic Resonance of Amorphous Alloys CuxZr100-x(40≦x≦60)
Authors: Abart J. , Socher W. , Voitländer J. 
Published: February 2015

Abstract

91Zr-and 63Cu-NMR measurements of the amorphous alloys CuxZr100-x(40≦x≦60) are reported. By comparison of the experimental quadrupole disturbed spectra with simulated spectra of the amorphous alloys a short range order can be deduced, which is similar to the local lattice symmetry of the corresponding crystalline compounds. Furthermore the Knight shift of both nuclei in the alloys could be determined.
Determination of a High Potential Barrier Hindering Internal Rotation from the Ground State Spectrum The Methylbarrier of cis-Propanal
Authors: Hardy J. A. , Cox A. P. , Fliege E. , Dreizler H. 
Published: February 2015

Abstract
The barrier hindering internal rotation of the methyl group was determined by analysing the splittings of rotational lines in the ground state. So model errors are minimized. The assignment was checked by double resonances and a centrifugal distortion analysis.
Molecular Dynamics Simulation of an Aqueous MgCl2 Solution. Structural Results
Authors: Dietz W. , Riede W. O. , Heinzinger K. 
Published: February 2015

Abstract
A molecular dynamics simulation of a 1.1 molal aqueous MgCl2 solution has been performed employing the central force model for water. The effective pair potentials for ion-water have been derived from ab initio calculations. The basic box with a sidelength of 18.30 Å contained 200 water molecules, 8 anions and 4 cations, corresponding to an experimental density of 1.079 g/cm3 . The simulation extended over about 3.3 picoseconds at an average temperature of 309 K. The structure of the solution is described by radial distribution functions and the orientation of the water molecules in respect to physically meaningful directions. Values for the dielectric constant and hydration energies have been calculated. The strong influences of the twofold charged magnesium ion on the geometry of the water molecules and the structure of the hydration shell is discussed in comparison with the results of a previous simulation of a 2.2 molal NaCl solution.
Magnetic Susceptibility of Pressed Powders of Some Rare-Earth Iron Garnets
Authors: Yadava V. R. , Verma B. K. , Tripathi A. K. , Lai H. B. 
Published: February 2015

Abstract
The molar magnetic susceptibilities (χм) of spherical balls of rare-earth iron garnets REIG's, with RE = Y, Gd, Dy, Ho, Er and Yb, prepared from pellets pressed at pressures ranging from 2 to 8 × 107 kg m-2 , have been measured in the temperature range 300-900 K. It is found that χмα exp( - f), where f is the pore fraction of the pressed balls. It has also been observed that χм for a particular garnet at a fixed temperature increases from powder through pressed material to single crystal. REIG's reveal typical ferrimagnetic behaviour with the ferrimagnetic Curie temperature (Tc) lying in the range 550-570 K for single crystals. In general, for pressed material Tc increases linearly with density. The χм
-1 vs, T variation has been analysed using molecular field theory. It has been found that for T ≫ Tc the magnetic ions behave as if they were almost free and yield a magneton number very close to their free ion value.
Effect of Temperature on the Mechanoluminescence of Coumarin Crystals
Authors: Chandra B. P. , Deshmukh N. G. 
Published: February 2015

Abstract
The mechanoluminescence of coumarin crystals is studied. It is found that mechanoluminescence decreases sharply with temperature near the melting point and that it may be a useful probe for studying the behaviour of crystals near the melting points.
EPR of Cu2+ in Ferroelectric LiH3(SeO2)2 Single Crystals
Authors: Waseem Mohd. , Dayal R. , Jain Vimal Kumar 
Published: February 2015

Abstract
The electron paramagnetic resonance of Cu2+ in ferroelectric LiH3(SeO3)2 has been studied at 298 K in X-band. The Cu2+ appears to substitute Li+ in the lattice with the z-axis nearly along the Li-O(6) bond direction. The spectra have been analysed using the spin-Hamiltonian appropriate for Cu2+ in orthorhombic symmetry.
Influence of O2 on the 535.0 nm Thallium Line
Authors: Lisicki E. , Bielski A. , Szudy J. 
Published: February 2015

Abstract
The effect of molecular oxygen on the broadening and shift of the 535.0 nm Tl line resulting from the photodissociation of thallium iodide vapour was studied at low densities of O2. The broadening and shift coefficients were determined.
Pressure Dependence of the Nematic State Temperature of a Compensated Cholesteric Liquid Crystal
Authors: Pollmann P. , Wiege B. 
Published: February 2015

Abstract
At a certain temperature Tn (nematic temperature) a mixture of two cholesteric components which separately form helices of opposite senses behaves like a nematic. An inversion of the helical structure occurs when passing Tn, from a right-handed to a left-handed structure or vice versa. In the temperature-pressure space such compensated mixtures therefore will exhibit an inversion line which - on the basis of optical rotatory power measurements under high pressure - is presented for the first time.
On Electro- and Thermomigration and Thermoelectric Transport Coefficients in Metals
Authors: Bohn H.-J. , Simon G. 
Published: February 2015

Abstract
The system of coupled Boltzmann transport equations for electrons, phonons and impurities in metals is set up and solved with special interest for the effect of the cross-coupling terms. General expressions for the effective charge in electromigration and heat of transport in thermomigration are given. The cross-coupling terms in the transport equations lead to a number of corrections in the thermoelectric transport coefficients. Noteworthy is the result that the resistance by impurities depends now on the temperature. The investigation is restricted to high temperatures, isotropic dependence of the energies of electrons and phonons on wave number vector, and to normal scattering processes of phonons.
Electronic Structure of Solvent-Polarity Indicators. Solvatochromism and Tautomeric Epuilibria of Styryl-Merocyanines
Authors: Abd-El-Mottaleb M. S. A. 
Published: February 2015

Abstract
Solvatochromic and halochromic behaviour of two unsymmetrical merocyanine-type dyes, namely 2-[2′- and 4′-hydroxystyryl]-pyridinium methiodide, are studied.
In alcoholic and hydrogen-bond-acceptor (HBA) solvents their visible absorption spectra exhibit an additional long-wavelength band suggesting the existence of tautomeric equilibria in their solutions. The tautomeric equilibrium constants in triethanolamine-acetone mixed solvents are determined.
Quantum mechanical MO method PPP-π-SCF-CI is used to calculate the electronic spectra and the underlying keto-enol-tautomeric stability. Deprotonation of the OH group is shown to provide destabilization in binding energy in excess of 5 eV in agreement with the experimental results indicating that these indicators exist mainly as protonated species (enol form) in their solutions.
Furthermore, solvent-induced changes in the ground-state electronic structures are examined by means of 1H-NMR spectroscopy and the PPP calculations.
Microwave and Millimeterwave Spectrum of Bromofluoroacetylene (Br—C≡C—F)
Authors: Andolfatto M. , Kleibömer B. , Guarnieri A. 
Published: February 2015

Abstract
The microwave and millimeterwave spectra of Bromofluoroacetylene 79Br-C ≡ C-F and 81Br-C ≡ C-F in natural abundance have been investigated. The molecule has been found to be linear. The rotational constant, the centrifugal distortion constants Do, the Bromine quadrupole coupling constant and the electrical dipole moment have been determined.
Some r0-structures have been calculated assuming different values for the C ≡ C distance.
Darstellung enantiomerenreiner 3-Oxa-2,7-diazabicyclo[3.3.0]octane und ihre Umwandlung in andere bicyclische Ringsysteme/Preparation of Pure Enantiomeric 3-Oxa-2,7-diazabicyclo[3.3.0]octanes and their Conversion to Other Bicyclic Ring-Systems
Authors: Aurich Hans Günter , Soeberdt Michael 
Published: February 2015

Pure Enantiomeric (S)-N-benzylalaninol (R1 = Me) and (S)-N-benzylvalinol (R1 = i-Pr) were allylated with Br-CH2-CH=CR2R3 (R2 = R3 = H; R2 = Ph, R3 = H; R2 = R3 = Ph). Swern oxidation followed by treatment with methylhydroxylamine afforded nitrones 6 (Me- N(O)=CH-CHR1-N(CH2Ph)CH2-CH=CR2R3) which underwent an intramolecular 1,3-dipolar cycloaddition providing 3-oxa-2,7-diazabicyclo[3.3.0]octanes, e.g. (1R,5R,8S)-7-benzyl-2,8- dimethyl-3-oxa-2,7-diazabicyclo[3.3.0]octane 7a (R1 = Me, R2 = R3 = H) and (1R,4R,5R,8S)- 7-benzyl-2,8-dimethyl-4-phenyl-3-oxa-2,7-diazabicyclo[3.3.0]-octane 7b (R1 = Me, R2 = Ph, R3 = H).
Reductive ring opening of 7a and 7b afforded the corresponding a-hydroxyalkylated pyrrolidines (9a: R2 = H or 9b: R2 = Ph. resp.). Condensation of these compounds with benzaldehyde yielded a mixture of diastereomeric 4-oxa-2,8-diazabicyclo[4.3.0]- nonanes: 10a/11a (1R,3S,6R,9S)/(1R,3R,6R,9S) R1 = Me, R2 = R3 = H and 10b /lib (1R,3S,5R,6R,9S)/(1R,3R,5R,6R,9S) R1 = Me, R2 = Ph, R3 = H. Pyrrolidine 9b was converted to the mesylate which formed (1R,4S,5R,7S)-3-benzyl-4,6-dimethyl-7-phenyl-3,6-diazabicyclo[3.2.0]heptane 13 along with (4R,5S)-1-benzyl-3,5-dimethyl-4-styryl-imidazolidine 15 upon treatment with sodium hydroxide.