bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Structural Systematics in the II–VI, III–V, and Group‐IV Semiconductors at High Pressure
Authors: McMahon M. I. , Nelmes R. J. 
Published: July 2007

AbstractA systematic study of the II‐VI, II‐V, and group‐IV semiconductors using angle‐dispersive diffraction techniques is revealing new structures and transitions that significantly modify the accepted structural systematics of these materials. Recent new results from Ge, ZnSe, InSb, and GaAs extend the range of some aspects already indicated by our previous work, and new intermediate phases have been found in InSb, and in HgSe and HgTe.
Pretransitional Behavior in Zincblende HgTe under High Pressure and Temperature
Authors: Besson J. M. , Grima P. , Gauthier M. , Itié J. P. , Mézouar M. , Häusermann D. , Hanfland M. 
Published: July 2007

AbstractThe equation of state of mercury telluride, HgTe, has been measured under pressure in its zincblende and cinnabar phases up to 800K, by X‐ray diffraction under synchrotron radiation in a large volume Paris‐Edinburgh cell. The thermal expansion coefficient decreases to zero around 1.1 GPa and then becomes negative up to the first‐order phase transition to the high‐pressure cinnabar phase, around 1.4 GPa. This behavior is related to the increase with temperature of the nonlinearity in the pressure dependence of the bulk modulus. It indicates an overall softening of the phonon branches of zincblende HgTe prior to the phase transition which characterizes a second‐order pretransitional behavior.
High Pressure Structural Study of I–III–VI2 Chalcopyrites
Authors: Mori Y. , Takarabe K. , Iwamoto S. , Minomura S. , Niwa E. , Masumoto K. 
Published: July 2007

AbstractHigh pressure powder X‐ray diffraction studies are reported for the chalcopyrite phases of AgGaX2 (X = S, Se, and Te). Structural parameters have been determined by the Ftietveld method. While the c/a ratio decreases with increasing pressure, the anion displacement parameter u is constant within experimental error for all samples investigated.
Structural Studies of CuInS2 and CuInSe2 under High Pressure
Authors: Tinoco T. , Polian A. , Gómez D. , Itié J. P. 
Published: July 2007

AbstractCuInS2 and CuInSe2 chalcopyrites have been studied up to 29 GPa in a diamond anvil cell by energy dispersive X‐ray diffraction (EDX) using synchrotron radiation. Phase transitions have been observed at 9.5 and 7.6 GPa and the high‐pressure phases have been indexed as cubic. The pressure dependence of the volume per formula unit has been fitted with a first‐order Murnaghan equation of state. The bulk moduli are 75 and 72 GPa for the chalcopyrite phases and 123 and 114 GPa for the cubic phases of CuInS2 and CuInSe2, respectively. The volume reduction at the transition pressure is roughly 10%. The recovered phases are quite different from the initial ones. For CuInSe2 it is of the zincblende type, for CuInS2 it is an amorphous phase. Thus, the pressure‐induced phase changes are not reversible.
High Pressure Phases of AlSb from ab‐initio Theory
Authors: Rodríguez‐Hernández P. , Muãoz A. , Mujica A. 
Published: July 2007

AbstractWe present the results of an ab‐initio study of the ground state properties and the high pressure phase diagram of AlSb. We have analyzed the structural parameters and the total energy of AlSb in the rocksalt, cesium chloride, ß‐tin, zincblende, and nickel arsenide‐type structures, performing first principles self‐consistent local density calculations with nonlocal pseudopotentials. From the energy versus volume diagram we obtain that at 4.7 GPa AlSb transforms to the NiAs‐type structure, like other III‐V AIX compounds. This is in disagreement with a recent experimental study that reports a transition to a ß‐tin structure. We also predict a second transition to the CsCl‐type structure at 39.5 GPa.
ZnSb and GaSb Bulk Amorphous Semiconductors: Transport Properties
Authors: Antonov V. E. , Barkalov O. I. , Kolyubakin A. I. , Ponyatovsky E. G. 
Published: July 2007

AbstractTemperature dependencies of the conductivity and thermopower of bulk amorphous semiconducting alloys Zn41Sb59 and Ga100−xSbx with 47.5 < x < 55 were measured at 80 to 370 K and 120 to 370 K, respectively. The samples were prepared by solid state amorphization of the quenched high pressure phases occurring on heating at ambient pressure. The electrical properties of nonstoichiometric a‐Zn41Sb59 are well described by the conventional Mott‐Davis model. Those of both stoichiometric a‐GaSb and nonstoichiometric a‐Ga100−xSbx, appear to be more unusual and require a modification of the model.
Pressure‐Induced Amorphization of LiInGe
Authors: Bräninger S. , Schwarz U. , Syassen K. , Kniep R. 
Published: July 2007

AbstractWe have investigated the structural stability of the ternary Zintl phase LiInGe up to 35 GPa by means of angle dispersive X‐ray powder diffraction. At ambient conditions LiInGe crystallizes in a cubic facecentred structure consisting of a polytetrahedral arrangement of In and Ge atoms. The compound undergoes a reversible phase transition to an X‐ray amorphous high pressure modification between 20 and 30 GPa. We have determined the equation of state for the low pressure phase and the result is discussed with respect to the related binary NaTl‐and zincblendetype compounds. In order to investigate the electronic properties of LiInGe we have performed LMTO band structure calculations.
Raman Spectra of InAs1−xSbx Alloys and InAs0.58Sb0.42/InSb Strained Layer Superlattice under High Pressure
Authors: Nagata K. , Webb S. J. , Stradling R. A. 
Published: July 2007

AbstractRaman scattering has been measured in InAs1−xSbx alloys (0 ⩽ × ⩽ 1) and an InAs0.58Sb0.42/InSb strained layer superlattice under hydrostatic pressures up to the phase transition. The pressure coefficient of the Raman frequency (δω/δp) of the InAs‐like LO mode in InAs1−xSbx alloys increases with increasing composition ×, while that of the InSb‐like LO mode is almost constant above × = 0.5. The phase transition pressure of InAs1−xSbx alloys decreases almost linearly with composition. On the other hand, both component layers of an InAs0.58Sb0.42/InSb superlattice change phase simultaneously at a pressure which is the mean of the phase transition pressures for bulk InAs0.58Sb0.42 and InSb.
Optical Properties of Pressure‐Polymerized C60
Authors: Venkateswaran U. D. , Sanzi D. , Krishnappa J. , Marques L. , Hodeau J.‐L. , Núñez‐Regueiro M. , Rao A. M. , Eklund P. C. 
Published: July 2007

AbstractWe report Raman, infrared (IR), and photoluminescence (PL) studies of several polymeric phases of solid C60 synthesized under high pressure and temperature conditions. The structure and dimensionality of bonding in the polymer depend on the conditions of synthesis. Relative to pristine C60, the Raman and IR spectra of these polymers exhibit numerous lines which are shifted to low frequencies and are also broadened. These changes are consistent with the loss of the original icosahedral C60 symmetry and an increase in the strength of intermolecular bonding due to polymerization. PL features are also broadened significantly and are redshifted compared to those of pristine C60 which is consistent with the usual trend that polymerization decreases the HOMO‐LUMO gap. The pressureinduced shift of the PL bands in the rhombohedral fullerene polymer is about five times smaller than that reported for solid C60.
The Effect of Pressure on the Concentration of Thermal Donors in Czochralski Grown Silicon
Authors: Misiuk A. , Jung W. 
Published: July 2007

AbstractWe have investigated the effect of annealing at temperatures up to 1230 K under hydrostatic argon pressure up to 1.1 GPa on thermal donor formation and on interstitial oxygen precipitation in Czechralski grown silicon. Depending on annealing temperature and applied pressure, the stressen‐hanced formation of thermal donors, enhanced interstitial oxygen loss from the Si‐O solid solution, and generation of oxygen‐related defects were observed.
The Structure of the Ordered Phase in Rocksalt Type Titanium Carbide, Carbidenitride, and Carbidehydride
Authors: Em V. T. , Yu. Tashmetov M. 
Published: July 2007

AbstractIt is shown that on the basis of the disordered δ‐phase (space group Fm3m) two ordered equilibrium phases with cubic (δ′‐phase, space group Fd3m) and trigonal (δ″‐phase, space group R3m or P3121) unit cells can be formed in titanium carbide TiC0.62 and carbidenitrides TiCxNy (x+y ≈︁ 0.63), whereas only a cubic δ′‐phase has been observed in TiC0.62Hy. With increasing temperature the low temperature trigonal δ″‐phase transforms at about 1053 K to the cubic δ′‐phase which experiences disordering. The formation of the cubic δ′‐phase at temperatures lower than 1053 K is explained by the difference between the order of δ → δ and δ → δ″ phase transitions.
Two‐Phonon Magneto‐Raman Scattering in Quantum Wells: Fröhlich Interaction
Authors: Cros A. , Cantarero A. , Belitsky V. I. 
Published: July 2007

AbstractWe have developed a theoretical model of two‐phonon resonant magneto‐Raman scattering in a semiconductor quantum well (QW). Fröhlich electron—phonon interaction has been considered and the corresponding selection rules are derived for Faraday geometry and backscattering configuration. The resonant profiles are analyzed as a function of magnetic field and laser energy. To simplify the discussion a three‐band model with parabolic masses has been used as a first approach, studying later the role of heavy‐hole light‐hole admixture in the scattering process. It is shown that, due to mixing effects, Fröhlich interaction contributes to the two‐phonon Raman spectra in the parallel (z̄(σ±, σ±)z) and also in the usually forbidden crossed (z̄(σ±, σ∓) z) polarizations. The model has been used to calculate the two‐phonon magneto‐Raman spectra of a 35 Å, GaAs/AlAs QW as an example.
Scattering of Excitons by Free Carriers in Semiconducting Quantum Well Structures: Finite Potential Well Model
Authors: Koh Tong San , Feng Yuan Ping , Spector Harold N. 
Published: July 2007

AbstractWe present a theoretical calculation of the elastic and ionization scattering cross sections of excitons due to their scattering by free carriers, in semiconducting quantum well structures of finite width, using the finite confining potential well model. Our results reveal interesting features that differ significantly from the predictions of the infinite confining potential well model. We find that both the elastic and ionization cross sections initially decrease with decreasing well width, but then in‐ crease below a critical well width where the exciton begins to revert to a quasi‐3D behavior. We compare the present results with those obtained using previous models to account for these new effects.
Decorated vacancy clusters in Si and thin C films grown on Si studied by depth profiling positron annihilation spectroscopies
Authors: Brusa R. S. 
Published: July 2007

AbstractThe combined use of different depth profiling positron annihilation spectroscopies give insight on distribution, type and decoration of open‐volume defects. Applications regarding defects produced in modified silicon and at the interface between deposited thin films and the silicon substrate are presented. The attention is focused on selected systems and situations potentially related to technological developments: a) identification of decorated vacancy clusters in silicon implanted by light‐ion (He, He+H) and evolution of the clusters with the thermal treatments; b) release of compressive stress through vacancy‐like defects formation at the interface during the growth of thin (10‐200 nm thick) carbon films. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PALS study of epoxy matrices: self‐assembly of block copolymers and its capability for nanostructuring thermosetting systems
Authors: Ramos Jose Angel , Serrano Elena , Tercjak Agniezska , Salgueiro Walter , Goyanes Silvia , Mondragon Inaki 
Published: July 2007

AbstractThe free volume in epoxy systems based on diglycidyl ether of bisphenol‐A (DGEBA) fully cured with aminic hardeners having different chemical structures has been studied by means of positron annihilation lifetimes spectroscopy. The results are compared with those obtained from the analysis of the macroscopic specific volume changes by using pressure‐volume‐temperature (PVT) experimental technique. An excellent correlation between the volumes measured at macro and nanoscales was found for the epoxy systems fully cured with aminic hardeners. On the other hand, a systematic study on the dependence of the volumes at nano‐scale in epoxy systems cured with two selected aminic hardeners at different pre‐cure temperatures revealed that the pre‐cure temperature, as well as, the structure of the hardeners governs the packing of the molecular chains of the epoxy network and its influence in the volume and number density of the nanoholes. In the second part of this work, a systematic study of the effect of several epoxidation degrees of butadiene block in a commercial polystyrene‐polybutadiene star block copolymer (SB) has been carried out to control nano‐ordering in thermosetting epoxy systems. For this purpose, blends of DGEBA cured with 4,4′‐methylenebis(3‐chloro‐2,6‐diethylaniline) (MCDEA) containing 30 wt% neat SB and several epoxidized SB star block copolymers have been synthesized. At low epoxidation degrees, interactions with the epoxy matrix are not sufficiently favorable and macroscopic phase separation takes place, leading to a phase‐inverted morphology where the block copolymer may become the matrix. For high epoxidation degrees, however, nanostructured thermosetting systems, being the epoxy‐rich phase the matrix of the blends, have been obtained. It has been proved that, in blends containing SepB61 and SepB76 star block copolymers, the copolymer self‐assembles into a well‐defined hexagonally ordered structure, where cylinders are formed by PS arranged in an epoxy matrix containing both epoxidized and non‐epoxidized butadiene units. SAXS experiments show that there are not strong differences in the long spacing between the different systems because the repeated distance between PS cylinders for all the blends is around 41‐42 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of nanopores in nanofiltration membranes using slow positron beam techniques
Authors: De Baerdemaeker J. , Boussu K. , Djourelov N. , Van der Bruggen B. , Dauwe C. , Weber M. , Lynn K. G. 
Published: July 2007

AbstractThe pore distribution of the commercial nanofiltration membranes Desal 5DL, Desal 51HL, N30F, NTR 7450 and NF‐PES‐10 were analyzed by positron annihilation spectroscopy using slow positron beam analysis. From the depth selective 3γ/2γ analysis a dense nanoporous filtration layer could be determined. From the depth selective lifetime analysis the size and distribution of the nanopores could be extracted. The measurements indicate the presence of 2 pore sizes in the samples with a radius of 1.25‐1.55 Å and 3.2‐3.95 Å. These experimental values are compared with the molecular weight cut‐off values of these membranes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron experiments at the new positron beam facility NEPOMUC at FRM II
Authors: Hugenschmidt C. , Brunner T. , Legl S. , Mayer J. , Piochacz C. , Stadlbauer M. , Schreckenbach K. 
Published: July 2007

AbstractThe in‐pile positron source NEPOMUC of the Munich research reactor FRM II delivers a low‐energy positron beam of highest intensity. Different source potentials can be applied in order to vary the primary kinetic energy of the positrons in the range between 15 eV and 1 keV. The maximum yield of slow positrons is up to 4 × 107 and 5 × 108 moderated positrons per second, respectively. New instruments for beam diagnostics have been implemented for the determination of the positron intensity and for positron beam profile measurements. The long‐term stability and the degradation of the platinum moderator as well as the recovery procedure were investigated. In the present arrangement of NEPOMUC's instrumentation the monoenergetic positron beam is magnetically guided to different experiments: a coincident Doppler broadening spectrometer (CDBS) and an analysis chamber for positron induced Auger electron spectroscopy (PAES). In addition, an apparatus for the production of the negatively charged positronium ion was connected to the beam line in order to investigate this bound leptonic system in collaboration with the Max‐Planck Institute for nuclear physics. An overview of the beam performance, the current status of the positron beam facility and the experiments is presented. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Atomic structure of pre‐Guinier–Preston zones in Al alloys
Authors: Staab T. E. M. , Haaks M. , Zamponi C. , Modrow H. , Maier K. 
Published: July 2007

AbstractWe propose X‐ray absorption (XAS) measurements as a novel approach to determine the atomic structure of pre‐Guinier–Preston zones. These nano‐clusters are formed during very early stages of aging AlCu alloys, immediately after solution heat treatment and quenching. X‐ray absorption near‐edge structure (XANES) spectra were taken from technical aluminum alloys at the copper K edge, revealing the local atomic environment of copper. The spectra of – after solution heat treatment – freshly quenched and of artificially aged alloys differ significantly from each other. We compare the measured XANES spectra with those calculated by the FEFF‐8 code. We show the importance of employing realistic, i.e. relaxed, atomic coordinates around the scattering atom type from ab‐initio calculations with SIESTA. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)magnified image
Effect of grape seed extract on lipid peroxidation, antioxidant activity and peripheral blood lymphocytes in rats exposed to x‐radiation
Authors: Enginar Hüseyin , Cemek Mustafa , Karaca Turan , Unak Perihan 
Published: July 2007

AbstractThe present studies were designed to evaluate supplemental grape seed extract (GSE) and vitamin E supplements on lipid peroxidation, on antioxidant systems and peripheral blood lymphocytes in rats exposed to x‐rays. Three groups of rats were investigated: a control group (CG) received intraperitoneal (i.p.) physiological serum 1 mL/day (n = 10), i.p.; a vitamin E group (VG) received 50 mg/kg/day (n = 10); an i.p. grape seed extract group received 50 mg/kg/day (n = 10). Four weeks later, a 6 Gy radiation dose was given to the rats. Blood samples were taken 24 h later after irradiation and lymphocyte, malondialdehyde (MDA), reduced glutathione (GSH), nitrate, nitrite, reduced ascorbic acid, retinol, β‐carotene and ceruloplasmin concentrations were analysed. The levels of GSH (p < 0.05), retinol (p < 0.001), β‐carotene (p < 0.05) and ceruloplasmin concentration (p < 0.001) in the GSE group were found to be higher than in the control group but the level of MDA (p < 0.001) and nitrite concentration (p < 0.05) in rats supplemented with GSE were found to be lower than in the control group.The results indicate that GSE enhanced the antioxidant status and decreased the incidence of free radical‐induced lipid peroxidation in blood samples of rats exposed to x‐radiation. The antioxidant effect of GSE given to animals was more effective than vitamin E administered before whole‐body irradiation in rats. Copyright © 2007 John Wiley & Sons, Ltd.
Necessary and sufficient conditions for the stability of polynomials with linear parameter dependencies
Authors: Abdallah C. , Docampo D. , Jordan R. 
Published: July 2007

AbstractIn this paper we show that Kharitonov's theorem will provide a necessary and sufficient condition for the stability of a particular family of polynomials where the coefficients are real and linearly dependent on a set of uncertain parameters. The main results are obtained by restricting the linear map from the parameter to the coefficient space to contain the Kharitonov polynomials. The results are applied to both continous‐time and discrete‐time polynomials and future extensions are discussed.
Stability radii of linear discrete‐time systems and symplectic pencils
Authors: Hinrichsen D. , Son N. K. 
Published: July 2007

AbstractIn this paper, we introduce and analyse robustness measures for the stability of discrete‐time system x(t + 1) = Ax(t) under parameter perturbations of the form A→A + BDC where B,C are given matrices. In particular we characterize the stability radius of the uncertain system x(t + 1) = (A + BDC)x(t), D an unknown complex perturbation matrix, via an associated symplectic pencil and present an algorithm for the computation of that radius.
A first principles solution to the non‐singular H∞ control problem
Authors: Petersen Ian R. , Anderson Brian D. O. , Jonckheere Edmond A. 
Published: July 2007

AbstractThis paper presents an elementary solution to the non‐singular H∞ control problem. In this control problem, the underlying linear system satisfies a set of assumptions which ensures that the solution can be obtained by solving just two algebraic Riccati equations of the game type. This leads to the central solution to the H∞ control problem. The solution presented in this paper uses only elementary ideas beginning with the Bounded Real Lemma.
Adaptive motion control of robot manipulators: A unified approach based on passivity
Authors: Brogliato Bernard , Landau Ioan‐Doré , Lozano‐Leal Rogelio 
Published: July 2007

AbstractThis paper presents a unified approach to direct adaptive motion control laws for robot manipulators that have been studied during the last few years by several authors. It provides a general approach based on sensivity to demonstrate the global asymptotic stability of adaptive schemes applied to rigid multilinked manipulators. It is shown that most of the schemes fit within this framework, which presents the advantage of being more systematic than other techniques and therefore will enable a unified presentation of the several schemes proposed to date and will increase our understanding of adaptive control of robot manipulators.
Robust control of robotic manipulators without velocity feedback
Authors: Yuan Jing , Stepanenko Yury 
Published: July 2007

AbstractThis study concerns the problem of robust control of robotic manipulators without joint velocity feedback. A robust lead + bias controller is studied. The bias signal is intended to compensate the nonlinear dynamics of the robot. The focus of this study is robustness when the nonlinear compensation is not perfect and the external disturbances are not negligible.A conservative polynomial bound is introduced to describe the worst feedback effect of the compensation error and the external disturbances. The polynomial bound covers a class of possible bias signals, synthesized according to the available knowledge about the robot dynamics. Based on the polynomial bound, the tracking errors of a lead + bias controller are proved to be uniformly bounded. They can be minimized by a proper design of the bias signal. In the ideal case where the bias signal compensates the robot dynamics perfectly, the tracking errors will converge to zero.
Outer factor ‘absorption’ forH∞control problems
Authors: Flamm David S. 
Published: July 2007

AbstractWe present a constructive method for ‘absorbing’ an irrational outer factor of a plant into the ‘Q‐parameter’ in theH∞optimal weighted sensitivity problem for single‐input/single‐output distributed parameter systems, when the plant has finitely many irrational zeros on the imaginary axis. This problem could not be solved using previous results. We also extend our new results to the mixed sensitivity problem.