bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular dynamics simulations from putative transition states of α‐spectrin SH3 domain
Authors: Periole Xavier , Vendruscolo Michele , Mark Alan E. 
Published: July 2007

AbstractA series of molecular dynamics simulations in explicit solvent were started from nine structural models of the transition state of the SH3 domain of α‐spectrin, which were generated by Lindorff‐Larsen et al. (Nat Struct Mol Biol 2004;11:443–449) using molecular dynamics simulations in which experimental Φ ‐ values were incorporated as restraints. Two of the nine models were simulated 10 times for 200 ns and the remaining models simulated two times for 200 ns. Complete folding was observed in one case, while in the other simulations partial folding or unfolding events were observed, which were characterized by a regularization of elements of secondary structure. These results are consistent with recent experimental evidence that the folding of SH3 domains involves low populated intermediate states. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Prediction of protein secondary structure content for the twilight zone sequences
Authors: Homaeian Leila , Kurgan Lukasz A. , Ruan Jishou , Cios Krzysztof J. , Chen Ke 
Published: July 2007

AbstractSecondary protein structure carries information about local structural arrangements, which include three major conformations: α‐helices, β‐strands, and coils. Significant majority of successful methods for prediction of the secondary structure is based on multiple sequence alignment. However, multiple alignment fails to provide accurate results when a sequence comes from the twilight zone, that is, it is characterized by low (<30%) homology. To this end, we propose a novel method for prediction of secondary structure content through comprehensive sequence representation, called PSSC‐core. The method uses a multiple linear regression model and introduces a comprehensive feature‐based sequence representation to predict amount of helices and strands for sequences from the twilight zone. The PSSC‐core method was tested and compared with two other state‐of‐the‐art prediction methods on a set of 2187 twilight zone sequences. The results indicate that our method provides better predictions for both helix and strand content. The PSSC‐core is shown to provide statistically significantly betterresults when compared with the competing methods, reducing the prediction error by 5–7% for helix and 7–9% for strand content predictions. The proposed feature‐based sequence representation uses a comprehensive set of physicochemical properties that are custom‐designed for each of the helix and strand content predictions. It includes composition and composition moment vectors, frequency of tetra‐peptides associated with helical and strand conformations, various property‐based groups like exchange groups, chemical groups of the side chains and hydrophobic group, auto‐correlations based on hydrophobicity, side‐chain masses, hydropathy, and conformational patterns for β‐sheets. The PSSC‐core method provides an alternative for predicting the secondary structure content that can be used to validate and constrain results of other structure prediction methods. At the same time, it also provides useful insight into design of successful protein sequence representations that can be used in developing new methods related to prediction of different aspects of the secondary protein structure. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Dipole–Dipole Interaction of Substitutional Impurity Molecules in Crystals
Authors: Kamenogradskii N. E. , Konobeev Yu. V. 
Published: July 2007

AbstractA theory is given of effective dipole—dipole interactions between two identical substitutional guest molecules at large intermolecular distance. An interaction theory for interstitial impurity molecules was developed in [3]. A two‐level scheme for the guest and host molecules is assumed. Local field corrections are discussed. It is shown that the dipole—dipole interaction of the guest molecules in a crystal is the interaction of the effective dipole moments. The values of such effective dipole moments differ from their values in vacuum by a factor which is expressed both by the dielectric constant at the impurity transition frequency and the microscopic characteristics of the medium.
Effect of the Superconducting Transition on the Creep in Lead
Authors: Soldatov V. P. , Startsev V. I. , Vainblat T. I. 
Published: July 2007

AbstractThe effect of the superconducting transition on the velocity of creep in lead has been investigated and found to increase sharply at the transition to the superconducting state. The value of the jump of creep velocity depends on the sample purity. The magnetic field does not effect the creep velocity. The possible causes (change of interaction between electrons and dislocations, change of barriers determining the mobility of dislocations at the superconducting transition) of the effect observed are discussed.
Evidence for a Defect Conversion Mechanism in Copper
Authors: Thompson D. O. , Buck O. 
Published: July 2007

AbstractThe effects of γ‐ray irradiation upon the internal friction and Young's modulus of copper have been measured in the temperature range from 81 to 241 °K. It is found that there exists a pronounced minimum in the rate at which defects arrive at dislocations in the vicinity of 170 to 180 °K. This minimum is discussed and its significance in terms of the two predominant radiation damage models is considered.
Trigonal Boracites — A New Type of Ferroelectric and Ferromagnetoelectric that Allows no 180° Electric Polarization Reversal
Authors: Schmid H. 
Published: July 2007

AbstractThe space group of the trigonal phase of the FeCl, FeBr, FeI, CoCl, and ZnCl boracites is established as C. Ferroelectricity is evidenced by domain switching. High coercive fields at room temperature (up to 800 kV/cm) are found. Polarization‐microscopical studies show that the polarization vector is not reversible by 180° but can jump only from, e.g., [111] to [111], [111], or [111], etc., in accord with crystal structure and group theoretical symmetry considerations. Two twinning “laws” are observed: a) head—head (tail—tail) domains with {110}cub as composition plane and b) head—tail domains with {100}cub as composition plane. The domain structure and the relevant twinning operations are discussed. The onset of ferromagnetism at low temperature in FeCl, FeBr, FeI, and CoCl boracites leads to ferromagnetoelectricity. In the case of CoCl boracite the ferromagentoelectric point group is m.
On the Analysis of the Force on a Moving Dislocation
Authors: Malén K. 
Published: July 2007

AbstractVarious derivations of an “equation of motion” for a dislocation seem to be contradictory. It is the aim of this paper to show how the various conclusions regarding the Lorentz force on a dislocation have arisen. It is found that an interpretation of the “equation of motion” needs a careful consideration of constraints imposed by the physical model of the dislocation and of the external condition imposed by the actual physical situation.
Intensity Relations in Laue Case Reflections of Perfect Crystals Containing Nearly Monochromatic Lattice Vibrations
Authors: Köhler R. , Möhling W. , Peibst H. 
Published: July 2007

AbstractA dynamical theory for the intensity relation of Laue case X‐ray reflections in the presence of nearly monochromatic lattice vibrations is developed. The results are compared with intensities diffracted from vibrating cadmium sulphide crystals excited by the acousto‐electric effect. A good agreement is obtained so that a useful method can be proposed for the measurement of vibration amplitudes.
Franz‐Keldysh Effect and Hot Electron Effects in the Interband Absorption of Semiconductors in an External Electric Field
Authors: Enderlein R. 
Published: July 2007

AbstractStarting from the generalized Kubo formula in the presence of an external electric field an expression for the electronic dielectric tensor of a semiconductor is obtained. The influence of a special type of non‐stationarity of the distribution function on the dielectric tensor is considered. For a two‐band model the imaginary part of the dielectric tensor is calculated explicitly considering both the Franz‐Keldysh effect and the hot electron effects. The relative influence of both effects is discussed.
On the Theory of Light Absorption by Antiferrodielectrics in the Frequency Range of Double Electronic Excitations of Molecules (Ions)
Authors: Petrov E. G. , Loktev V. M. , Gaididei Yu. B. 
Published: July 2007

AbstractThe band and bound states of double electronic excitations of antiferrodielectrics are considered; from the equation for Green's function the excitation spectrum of an anti‐ferrodielectric under creation of two electronic excitations in a crystal is obtained. The absorption spectrum of a molecular antiferrodielectric, of solid α‐oxygen, is considered as an example in the frequency range of double electronic 1Δg + 1Δg, 1Σ + 1Δg, 1Σ + 1Σ transitions.
Magnetization Distribution in a Ferromagnetic Thin Film by the Method of Statistical Green Functions
Authors: Onyszkiewicz Z. 
Published: July 2007

AbstractThe method of double‐time statistical Green functions is used to obtain the magnetization distribution in a ferromagnetic thin film. To solve the difference equations of motion for the Fourier transform of the Green function, the perturbation method is applied. Corrections to the magnon energy are obtained resulting from a stricter than hitherto treatment of the non‐uniform magnetization distribution in the film. Moreover, the present distribution differs considerably from those obtained by others recurring to the Green function method but resembles that derived from the molecular field method.
Neutron Diffraction Study of γ‐FeOOH
Authors: Oleś A. , Szytuła A. , Wanic A. 
Published: July 2007

AbstractResults of the study of γ‐FeOOH structure by means of neutron diffraction and Mössbauer effect are discussed. The positions of the ions are determined. The hydrogen ion occupies a central position between two oxygen ions separated from one another by 2.70 Å. The Néel temperature determined from magnetic susceptibility is 50 °K. A model of antiferromagnetic ordering of the magnetic moments is suggested.
Pressure Variation of Mössbauer Fraction for an Impurity Atom
Authors: Nandwani S. S. , Puri S. P. 
Published: July 2007

AbstractThe variation of “Mossbauer fraction”, f, with pressure of Fe57 embedded as a dilute impurity in Ti, V, Ni, Cu, Mo, Pd, W, and Pt host lattices has been calculated by incorporating both the force constant change and the mass change at the site of the impurity. Comparison of the calculations with available experimental values of the slope gives definite evidence for the change of the force constant q′/q. The value of q′/q thus obtained is in agreement with that obtained from the variation of f with temperature for Fe in Cu, but not for Fe in V.
The Interaction of Impurity Centres with the Surroundings and Quasi‐Line Spectra
Authors: Kizel V. A. , Sapozhnikov M. N. 
Published: July 2007

AbstractThe temperature dependence of the integral intensities and the positions and half‐width of the lines in the quasi‐line spectra of 3,4‐benzopyrene, naphthantrone, and dibenzoperopyrene in n‐paraffin matrices are measured and the temperature dependence of the quantum yield of the luminescence is investigated as well. It is shown that with increasing temperature the lines were broadened and shifted and that the integral intensity of the lines decreases slowly. However, it is established that the fall of the integral intensity is not due to a decrease of the probability of the zero‐phonon transition, but is due to a decrease of the quantum yield of the luminescence. — It is shown that the absence of any noticeable change of probability of the zero‐phonon transition in the temperature range 77 to 200 °K is a result of the weak coupling of the impurity with the crystal. The experimental data are interpreted from the point of view of the theory of the spectra of impurity centres in crystals.
Theoretical and Experimental Study of Interbranch Scattering Observed near a Dislocation Line in X‐Ray Topography
Authors: Authier A. , Balibar F. , Epelboin Y. 
Published: July 2007

AbstractIn the highly distorted regions surrounding a dislocation line the approximation of geometrical optics for the propagation of X‐rays is no more valid; diffraction phenomena then occur and give rise to the splitting of the wave fields incident upon these regions. The position of the points where these newly created wave fields originate and their direction of propagation are given theoretically. An experimental evidence of these new created wave fields is given using a double crystal spectrograph.
63Cu NMR in Elastically Deformed Copper Foils of Cubic Texture
Authors: Tompa K. , Tóth F. , Nagy E. 
Published: July 2007

AbstractThe 63Cu NMR spectrum parameters are, within the experimental accuracy, the same for the undeformed as for the in the 〈100〉av direction up to the elastic limit stretched copper foil of cubic texture. Our results with the application of the Sholl and Béal‐Monod and Kohn theories of the quadrupole effect in metals give an upper limit for the enhancement factor α ≦ 25.
The Effect of Non‐Linear Cohesive Stresses on the Stress Distributions around a Crack Tip
Authors: Schmidt V. , Woltersdorf J. 
Published: July 2007

AbstractStresses around the tip of a Barenblatt crack are calculated. The effect of non‐linear cohesive stresses behind the crack tip is taken into account in a linear elastic crack model consisting of special arrangements of edge dislocations. The cohesive stress distribution calculated, as well as the corresponding non‐linear stress—displacement relation agree with existing qualitative expectations. Within a region of radius d (where d presumably is 6 a < d < 30 a; a lattice constant) stresses and displacements should decrease more slowly with increasing distance as in the case of a Griffith crack. The distribution of the principal stress lines is discussed.
Mössbauer Study of Properties and Phase Transitions of GexSn1−xTe
Authors: Rigamonti A. , Petrini G. 
Published: July 2007

AbstractResults of a Mössbauer study of 119Sn in Ge0.1Sn0.9Te and Ge0.3Sn0.7Te are reported and discussed. The effective Debye temperatures for recoilless absorption are about 160 and 180 °K, respectively. From the isomer shifts a percentage of covalent character in the bonding of at least 47 could be deduced. A marked decreasing of the recoilless fraction has been observed near the transition from the cubic to the rhombohedral structure: it has been explained theoretically on the assumption of a critical lowering in the phonon frequencies; a possible q and temperature dependence of the anomalous branch has been derived indirectly. Finally an increasing in the half‐width of the Mössbauer line has been observed on cooling in the rhombohedral phase and it was attributed to the appearance of a quadrupole interaction.
Hydrostatic Pressure Coefficients and Deformation Potentials for II–VI Compounds
Authors: Cerdeira F. , Dewitt J. S. , Rössler U. , Cardona M. 
Published: July 2007

AbstractCalculations of the pressure coefficients of the gaps and spin—orbit splittings at the Γ and L Brillouin zone points have been performed for cubic ZnS, ZnSe, ZnTe, and CdTe using the KKR method. Special emphasis was placed on the determination of the pressure coefficients of spin—orbit splittings. These coefficients were found to be considerably smaller than those predicted from the wave function renormalization due to the change of volume. We also calculated pressure coefficients and deformation potentials for the smallest gaps of hexagonal ZnO, ZnS, CdS, and CdSe. The results of the calculations are compared with experimental data.
Interband optical transitions in disordered semiconductors
Authors: Bonch‐Bruevich V. L. 
Published: July 2007

AbstractThe interband absorption coefficient is calculated for the frequency range, ω, below the threshold value (“optical tail”). The tail is attributed to the influence of the random force field present in a disordered system. Two cases are considered: that of the “smooth” random field possessing a correlation function which is continuous and differentiable as many times as needed and that of the Coulomb field produced, for example, by randomly distributed charged centres. In both cases an exponential optical tail is obtained for a sample which is in a certain sense nearly intrinsic: In α ∼ – (Δ – ħ ω)/ω, where Δ is the band gap that would have been observed without fluctuations of the force field and ω is some characteristic energy. The tail is correlated with the density of states tail but does not reproduce it, the latter being Gaussian in the same energy range. In the most interesting case the formation of an optical tail is due to quantum effects in contrast to the density of states tail which may be obtained in a purely classical approximation as well. In the Coulombic case an explicit form of the dependence of ω on impurity concentration n is obtained ω ∼ n2/5. This seems to be in agreement with the experimental data available.
Magnetic susceptibility anomaly in nearly equiatomic MnNi alloys
Authors: Pál L. , Tarnóczi T. , Konczos G. 
Published: July 2007

AbstractThe crystallographic and magnetic properties of nearly equiatomic nickel–manganese alloys have been investigated by X‐ray and neutron diffraction techniques as well as by classical susceptibility measurements. It has been found that the antiferromagnetic–paramagnetic phase transition takes place in most of the cases as a result of the θ → β allotropic transformation. It has been observed that the temperature dependence of the susceptibility in alloys containing somewhat more than 50% nickel is strongly influenced by an external magnetic field. Samples cooled down slowly in a magnetic field of several kOe have a room temperature susceptibility three to four times higher than before the heat treatment. The increased susceptibility shows an unidirectional anisotropy which is explained by the non‐equal distribution of the excess nickel atoms between the two manganese sublattices.
Galvanomagnetic phenomena in semiconductors with non‐parabolic dispersion law at non‐elastic scattering of carriers
Authors: Tolpygo H. I. 
Published: July 2007

AbstractBy means of [1] the distribution function, conductivity, Hall coefficient, and magnetoresistance are calculated for non‐degenerate semiconductors with Kane's dispersion law in the temperature and concentration ranges where impurity and optical scattering dominate. Intrinsic conductivity and scattering of electrons by holes are considered at elevated temperatures. Numerical calculations are made and compared with experimental data for n‐InSb. A complicated temperature dependence of the Hall factor with a characteristic “dip” at kT ≈︁ ħωopt is obtained. Some discrepancy of the theoretically evaluated mobility with experimental results at high temperature is probably due to a not exact knowledge of the parameters of interaction with optical phonons and the neglect of the temperature dependence of the effective mass at the bottom of the conduction band.
Inter‐valence band magneto‐absorption in tellurium
Authors: Miura N. , Tanaka S. 
Published: July 2007

AbstractThe infrared magneto‐absorption of tellurium due to the inter‐valence band transition of holes was investigated between 1.7 and 4.2° K. Magnetic fields up to 44.9 kOe were applied in the directions of the three crystallographic axes. For H⊥c‐axis, an oscillatory absorption was observed, which is caused by the harmonic transition of holes from the lowest lying impurity state. The effective cyclotron mass of the split off band was estimated to be \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {m_z m \bot } = 0.11\;\,m_0 $\end{document}. The results were analysed using the dumb‐bell model of the valence bands involving the difference in the transverse effective masses between the two valence bands.
The elastic constants of cuprous oxide
Authors: Hallberg J. , Hanson R. C. 
Published: July 2007

AbstractThe elastic constants of cuprous oxide have been measured by a standard pulse echo technique. The low temperature limiting values of the stiffness moduli are (in units of 1011 dyn/cm2) C11 = 12.1 ± 0.5, C12 = 10.5 ± 0.4, C44 = 1.09 ± 0.03. The Debye temperature calculated from these is 181° K. Both shear moduli show an unusual increase with increasing temperature.
Structure, energy, and periodic potential of kinks in screw dislocations for B.C.C. lattices
Authors: Hartmann O. , Pegel B. 
Published: July 2007

AbstractThe widths, energies, and periodic potentials of kinks in undissociated screw dislocations are numerically computed within a modified Dietze and Leibfried model. The kinks considered are assumed to lie in a {110} plane. Results are presented for Nb, Mo, and Fe. The kink widths range between 0.8 and 2.6 lattice constants while the amplitudes of the periodic potential felt by the kink when moving along the dislocation are found to be 6, 15, and 2 meV for Nb, Mo, and Fe, respectively. The kinks are short and the kink widths differ, depending on the kink position, by about 100%. The kink energies range between 0.5 and 4 eV.
Energy loss and energy straggling of well channelled hydrogen, helium, and lithium ions in gold
Authors: Högberg G. , Nordén H. , Skoog R. 
Published: July 2007

AbstractThe stopping cross‐sections of well channelled H+, D+, He+, and Li+ ions have been determined in thin gold single crystals along the 〈110〉, 〈112〉, and 〈111〉 directions. The energy range studied was 2 to 54 keV. The energy straggling has been investigated as a function of energy loss for different mean energies, kinds of ions, and crystallographic directions. In some cases the energy loss spectrum showed a structure.
Nuclear magnetic relaxation and random reorientations in molecular crystals
Authors: Ivanov E. N. 
Published: July 2007

AbstractA calculation is made of the half‐width of the nuclear magnetic resonance line Δω1/2 and the spin‐lattice relaxation time T1 in molecular crystals. It is suggested that the relaxation is due to the modulation of the intermolecular dipole–dipole interaction of random reorientations of molecules. The random reorientations of molecules in a crystal lattice are treated on the basis of the random rotational travelling model, earlier suggested by the author. Δω1/2 and T1 are found to be determined by the number of equilibrium reorientations of the molecule. For different elementary rotational angles (π/2, π/4, π/6) calculation formulae are given. The nature of random reorientations is discussed.
Energy transfer and rate equations—application to ruby
Authors: Heber J. 
Published: July 2007

AbstractAtomistic rate equations are represented for the transfer of optical excitation energy between donor and acceptor ions in ionic crystals. The physical assumptions which are necessary to deduce the phenomenological collective rate equations from the atomistic ones are specified. Time resolved measurements of the energy transfer from isolated Cr3+ ions to Cr3+ pairs in ruby are discussed. It is shown that, contrary to the present ideas, the collective rate equations cannot be applied in this case.
The optical properties of Sb2Se3Sb2Te3
Authors: Procarione W. , Wood C. 
Published: July 2007

AbstractThe optical properties of single crystal specimens of Sb2Te3Sb2Se3 solid solutions have been investigated in the photon energy range 0.04 eV to 6.5 eV. A wide range of solid solutions having hexagonal structure were found to exhibit properties closely corresponding to the isostructural compounds Bi2Te3 and Bi2Se3. Small indirect band gaps approaching semimetallic values were obtained. The high free‐carrier concentrations gave rise to plasma effects in the near infra‐red. In contrast Sb2Se3 is orthorhombic with a direct band gap near 1 eV. The chemical bonding concepts applied to similar systems seem applicable with only slight modification.