bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal structure of a newly oxidized aristolane sesquiterpenes, C15H22O3, from aristolochia debilis
Authors: Farag I. S. Ahmed , Kordy M. A. El , Kirfel A. , Will G. 
Published: January 2007

AbstractMr = 250, orthorhombic, P 212121, a = 9.583(6), b = 11.786(8), c = 12.298(9) Å, V = 1389.0 Å3, Z = 4, Dx = 1.20 g cm−3, F(000) = 544, MoKα, λ = 0.71069 Å, μ = 0.88 cm−1. Final R = 0.023 for 1006 observed reflections, T = 293 K. The structure was solved by direct methods and refined by full‐matrix least squares. It is an α, β unsaturated carbonyl compound with a trisubstituted double bonds. No significant variation in aromatic bond lengths. The strain affecting the molecule is largely due to angular deformation which is partly due to the fusion of the rings and partly due to substitution of H‐atoms by methyl groups and oxygen atoms.
Influence of penetration velocity and temperature by microindentation of NaCl single crystals
Authors: Boyarskaya Yu. S. , Grau P. , Zhitaru R. P. , Kluge G. 
Published: January 2007

AbstractThe kinetic of formation of microhardness indentations on NaCl‐single crystals has been investigated. The indentation was performed dynamically by a new recording technique, allowing to use different penetration velocities at distinct deformation temperatures. The characteristical indentation parameters are dependent on velocity and temperature in a partially complicated way showing the simultaneous action of different thermal activated deformation processes.
Interference pattern of X‐ray waves inside the crystal and its image in vacuum in double‐field approximation (II)
Authors: Aslanian V. G. , Bezirganian H. P. , Bezirganian P. H. 
Published: January 2007

AbstractThe energy flows of the X‐ray waves, diffracted in thick crystals in double‐field approximation, have been examined. It has been demonstrated that in a symmetric Laue case the energy flows in the upper layers are oriented in the direction of incidence and reflection, whereas in the lower layers they are oriented in the direction of the normal to the entrance surface of the crystal. The formation of pendular bands during diffraction of X‐rays in thick parallelepiped and wedge‐shaped crystals has been investigated. A method for obtaining pendular bands from such crystals is described.
Growth of hollow Bi2Se2S crystals from vapour
Authors: Arivuoli D. , Gnanam F. D. , Ramasamy P. 
Published: January 2007

AbstractHollow crystals of Bi2Se2S have been grown from vapour. Crystals show open lateral surface and the length of the crystals is 6 to 7 mm. An explanation is given for the growth mechanism of the hollow crystals.
Growth of Te(OH)6Na2HPO4 · H2O single crystals in silica gel and their characterization
Authors: Devanarayanan S. , Kalkura S. Narayana 
Published: January 2007

AbstractSingle crystals of Te(OH)6Na2HPO4 · H2O were grown in silica gel medium using single‐test tube diffusion method. Hexagonal pyramidal and hexagonal tabular single crystals were obtained. Crystals were characterized by IR, X‐ray, and Raman studies.
Effect of purification on the polytypism in solution‐grown cadmium iodide crystals
Authors: Chaudhary S. K. , Trigunayat G. C. 
Published: January 2007

AbstractThe effect of purification on the polytypism in cadmium iodide crystals has been studied by X‐ray diffraction in three hundred and sixty polytypes. Formation of small period polytype 2H is governed by both temperature and impurities contained in the starting material. 4H is the most stable polytype and higher occurrence of unidentified polytypes in crystals of purified material has been attributed to free movement of edge dislocations during growth. The results have been examined against empirical conclusions of earlier investigations.
X‐ray diffraction in thick perfect crystals with deformed subsurface layers
Authors: Bezirganyan P. H. , Aboyan A. O. , Tumasyan A. S. 
Published: January 2007

AbstractThe diffraction of X‐rays in thick perfect crystals with deformed subsurface layers has been investigated. It was shown that the kinematic scattering of X‐rays took place in deformed layers, while the dynamical one occurred in the perfect part of the crystal, ‐its bulk; also, that in beams of X‐rays diffracted on surface defects, the role played by the second harmonics of the applied characteristic radiation MoKα1 was essential.
Photoelastic and X‐ray topographic studies of residual stress and lattice deformation in GaAs single crystals
Authors: Adamkiewicz G. , Bajor A. , Wierzchowski W. 
Published: January 2007

AbstractThe GaAs crystals, grown with three different methods were simultaneously studied by means of photoelastic and X‐ray topographic methods. The methods provide complementary information about lattice deformation. The correspondence between interplanar distance changes and photoelastically measured stress values and the connection between cellular structure and high stress values were also found.
Multifrequency ultrasonic investigations in the liquid crystal 80CB
Authors: Venkatacharyulu P. , Gupta A. V. N. , Murthy V. Krishna , Rao J. V. 
Published: January 2007

AbstractInvestigations on the temperature variation of the specific volume and ultrasonic velocity (at four different fixed frequencies) in the liquid crystal 4′‐n‐octyloxy‐4‐cyanobiphenyl (80CB) are carried out both in the nematic and isotropic phases. From these studies various physical parameters like adiabatic compressibility (ßad), molar sound velocity or Rao number (Rn), molar compressibility (B), Van der Waal's constant (b) and the intermolecular free lengths (L) as a function of temperature are estimated. The variation of all these parameters with the ultrasonic frequency is also studied. The variation of the order parameter with temperature is also studied at the four frequencies and the results are discussed.
A special shear method of alignment for smectic liquid crystals
Authors: Jákli A. , Jánossy I. , Bata L. , Buka A. 
Published: January 2007

AbstractA special shear method is presented for the planar alignment of smectic liquid crystals. The shear was applied at the isotropic‐smectic A or cholesteric‐smectic A phase transition temperature, when the “batonnets” floated freely in the isotropic or cholesteric fluid. This type of shearing provided good alignment in the broad range of sample thickness (up to 100 μm) with monodomain areas of about one square centimeter.
On the fivefold cluster symmetry
Authors: Kostov R. I. , Kostov I. 
Published: January 2007

AbstractSeven pentagonal point groups are considered to be compatible with the local symmetry of crystal structures and important when interpreting the transition from precrystalline and quasicrystalline to true crystalline states. Clusters of fivefold symmetry seem to be stable balancing fourfold and sixfold symmetries. Together with clusters with other symmetry they play perhaps a significant role in the nucleation process and the ensuing growth of the crystals.
TEM studies of medium‐doses Kr+‐implanted silicon
Authors: Morawiec J. 
Published: January 2007

Abstract〈100〉 silicon wafers implanted with 300 ke V Kr+ ions to the following 5 × 1013, 1 × 1014 and 5 × 1014 cm−2 doses were investigated by means of conventional and high voltage transmission electron microscopes. Planar‐view technique was applied to characterize primary damage and to determine the geometry and the nature of secondary defects left after the furnace annealing. It is concluded that implantation to the lowest and highest doses, respectively, leads to incomplete and complete amorphicity of entire bombarded region, whereas the intermediate dose forms a burried amorphous layer. Small interstitial Frank dislocation loops on {111} planes are the predominant secondary defects for the range of doses. Occurrence of additional rod‐like defects is related to the regions of discontinuous initial amorphicity.
Momentum distribution of electrons in metallic lithium
Authors: Mosharafa A. A. , Radwan A. M. 
Published: January 2007

AbstractThe momentum distribution of electrons in metallic lithium is calculated along the main axes of symmetry in momentum space. The crystal has a bcc structure of side 6.6317 a.u., both the crystal potential and orthogonalization to core states are adequately considered. The results show a marked anisotropy in the momentum distribution, this is mainly due to the strong effective potential seen by the conduction electrons. This causes states in the lowest band, particularly near the Brillouin zone boundary, to be strongly coupled.
Photoconductivity of ZnSe:Dy
Authors: Bhushan S. , Abraham K. E. 
Published: January 2007

AbstractNature of dark current has been investigated as a function of different metallic electrodes and the ambient temperature. Photoconductivity rise and decay curves have been investigated as a function of different metallic electrodes, flux and impurity concentrations, ambient temperature and the cell thickness. A maximum increase of 59 times in Ipc has been reported. Possible explanations are given for the observed effects.
On the crystallization of gypsum from supersaturated solutions
Authors: Hünger Klaus‐Jürgen , Henning Otto 
Published: January 2007

AbstractThe influence of supersaturation relations in the mixing of Ca2+‐ and SO containing solutions in different concentrations on the size and shape of growing gypsum crystals are investigated. The PBC vector method is used to describe the shape of gypsum crystals theoretically. The change of the specific electrical conductivity during the formation process is measured. The numerical integration of a differential equation system permits the relative determination of the nucleation and crystal growth rate. The value of the surface tension of gypsum nuclei is 3.3 · 10−3 N/m.The formation of gypsum fibres is explained by the differences in the specific surface tension of some faces. The (hkl)‐ and (hk0) faces are unstable and grow faster than the (0kl) faces, that's why the a direction is the fibre axis. The prefered arrangement of CaSO4 molecules in a direction is supported through two fibrous crystals situated parallel a direction.
Reflectivity measurements of thin SiO2 layers in the soft‐X‐ray region
Authors: Klinkenberg E.‐D. , Illinsky P. P. 
Published: January 2007

AbstractEnergy and angular dependent reflectivity measurements of differently prepared SiO2 layers were made in the soft X‐ray region in order to study differences in their optical and electronic behaviour caused by the technological process. The optical constants of the layers were determined by fitting the angular dependent reflectivity data with a multilayer model which takes into account the roughness of all interfaces. Detailed knowledge of the polarization level of the primary beam from the synchrotron radiation source is needed for reliable results. The energy dependent reflectivity measurements indicate that high‐pressure dry‐oxidized layers have a more perfect structure than normal dry‐oxidized layers. Independent on the deposition process the SiSiO2 interface roughness amounts to ± 1 nm. The Si2p‐XANES of Si and SiO2 were detected.
The pseudomorphous phase transformation of faujasite‐type zeolites in processes of their crystal destruction
Authors: Richter‐Mendau J. , Lutz Wolfgang , Grossmann Andreas 
Published: January 2007

AbstractThe hydrothermal treatment of faujasite‐type zeolites in water, water vapour or weak acidic resp. alkaline solution usually leads to a pseudomorphous phase transformation. The process starts near the surface and penetrates the crystal. Due to the small reaction rate of the transformation as long‐time process the new material grows within the geometry of the dissolving zeolites. Therefore their crystal morphology is unchanged. The reaction mechanism of phase transformations is discussed.
Two step nucleation in glass‐forming systems
Authors: Kožíšek Z. 
Published: January 2007

AbstractIt is studied the effect of the preliminary heat treatment on the kinetics of nucleation by the numerical computation of the kinetic equations of the classical homogeneous nucleation theory for the model Li2O · 2SiO2 melt. It was shown, that we can obtain some unexpected results, e.g., the time dependence of the nucleation rate exhibits the jump depending on the preliminary heat treatment.
A method for determination of size‐dependent crystal growth kinetics from batch experiments (I). One‐experiment estimation
Authors: Blickle T. , Lakatos B. , Halász S. , Molnár I. 
Published: January 2007

AbstractThe method developed for determining size‐dependent crystal growth kinetics makes use of the assumption that the linear growth rate is a product of a size‐dependent factor and a supersaturation‐dependent one. The transformed form of the population balance equation, obtained by means of this assumption, is the basis of the evaluation utilizing measurement data from one seeded batch crystallization experiment, namely the size distributions of the seed and product crystals as well as the supersaturation course. The application of the method is illustrated by evaluating an experiment with potash alum crystals.
Gross dissolution of natural rhombohedral calcite crystal in nitric acid in dynamic etching condition
Authors: Mehta Bharat J. , Sidpara G. R. 
Published: January 2007

AbstractGross dissolution of natural rhombohedral calcite crystal in concentrated nitric acid in dynamic etching condition is studied and interesting results are obtained. The gross dissolution is maximum at 6 molar concentration of nitric acid in dynamic etching condition which is similar to static etching condition. The activation energy and pre‐exponential factor is calculated for different concentrations (range 3.0 to 7.5 molar) of nitric acid. The values of activation energy and pre‐exponential factors increase as concentration increases in dynamic etching, and it is more than static etching. The higher values of gross dissolution, activation energy, and pre‐exponential factor in dynamic etching condition is explained.
Equilibrium dopant incorporation in CVD silicon epitaxy
Authors: Kühne H. , Morgenstern Th. 
Published: January 2007

AbstractIn‐situ doping of epitaxial silicon layer with arsenic is controlled either by means of a mixed equilibrium – kinetical mechanism characterised by the influence of layer growth rate, or by means of a pure equilibrium‐related mechanism showing no layer growth rate effect. Layer growth rate can be selected to mark the transition from one mode to the other by introducing a characteristic rate v. Equilibrium controls dopant incorporation when vepi 〈 v 〉 0 is ture. That critical rate depends on temperatur as well as on input partial pressure of arsine and can be expressed by the three different empirical quantities A, B, and E. The former two of them are defined by conventional dopant incorporation theory. The additional quantity E is a function of arsine input pressure. That function not only defines an upper limit E= E∞ but also a lower limit E= 0 at which v= 0 is valid.
Comparison of lead solubility in NaCl crystals from data obtained by different methods
Authors: Dudnikova V. B. , Urusov V. S. 
Published: January 2007

AbstractThe solvus of the NaCl: Pb2+ system was found in the concentration range from 1.5 × 10−3 to 1.9 × 10−2 mol% at temperatures ranging from 375 to 430 °C from the data of flotation measurements of the crystal density. The heat of impurity dissolution equal to 2.0 ± ± 0.6 eV and the change in the vibrational entropy in the formation of the solid solution Sv/K= 20 ± 10 were determined.Reasons for a difference in the estimates of lead solubility in NaCl, obtained from temperature dependences of light scattering and by other methods: measurement of the density, electric conductivity, and the electron‐microscopic decoration of the same crystals are discussed.
Ultra‐micro‐hardness measurements of non‐metallic crystals and an attempt for their calculation
Authors: Ulrich J. , Kruse M. 
Published: January 2007

AbstractThe ultra‐micro‐hardness of non metallic crystals has been measured for 16 substances. These are products usually produced in mass‐crystallization; inorganic, organic, with hydrates and unhydrates. The hardness‐force‐dependency was examined and data are compared to literature. KNO3 crystals showed a strong direction dependency (a factor of 2). In the end there has been made a first attempt to introduce a correlation of the measured micro‐hardness and physical properties of the crystals, but so far this was only possible for face centred cubic lattices.
Liquid crystalline phase transition studies in N(p‐n‐butoxybenzylidene) p‐n decylaniline, 40.10
Authors: Rao N. V. S. , Potukuchi D. M. , RaoA P. Bhaskara , Pisipati V. G. K. M. 
Published: January 2007

AbstractThe synthesis, characterization and the temperature dependence of density and ultrasonic velocity of N(p‐n‐Butoxybenzylidene) p‐n‐decylaniline, 40.10 are presented. The compound exhibits as trivariant liquid crystalline mesomorphism Viz., NAB the Isotropic – Nematic, and Smectic A – Smectic B phase transitions are found to be first order. However, the interesting Nematic Smectic A (NA) transition shows a second order nature. The NA transition results are discussed in the light of the available data on other nO.m compounds. The computed molecular parameters: adiabatic compressibility (βad) molar sound velocity (Rn) and molar compressibility (Aw) are presented.
Growth rate dispersion — a review
Authors: Ulrich J. 
Published: January 2007

AbstractThe growth rate dispersion (GRD) is reviewed from its start up to today. A definition is given followed by a summary of the facts and the first approaches for explanations. This all are surface reaction steps. The discussion of the consequences – no size dependent growth – is carried through. At the end the models (RF‐and CCG‐model) will be introduced which make it possible to work with the growth rate dispersion instead of size dependent growth. The newest approach is the superpositioning of the two models, this is perhaps the most promising way.
The current understanding of epitaxial CVD silicon layer doping in the light of modeling and theory development (VIII)
Authors: Kühne H. , Schröder K.‐W. 
Published: January 2007

AbstractLateral autodoping along the susceptor in downstream gas direction is described to be the result of a parasitic dopant partial pressure in the gas. Parasitic dopant species are distributed from buried layer surface into the gas during the predeposition period of the epitaxy process. They are diluted as well as gathered by the gas stream along the susceptor. The parasitic dopant pressure profile along the susceptor that exists when layer deposition begins, has been modelled by deriving an exponential expression taking into account a tilted flat susceptor having constant temperature, an increase of gas temperature along the susceptor, total gas throughput, total pressure, buried layer doping level, and the ratio of buried layer area per wafer to the susceptor area related to a wafer.
Cd diffusion in In0.53Ga0.47As
Authors: Ambrée P. , Gruska B. 
Published: January 2007

AbstractDiffusion experiments of Cd in VPE‐In GaAs, lattice matched to InP, are reported. The closed ampoule technique used makes it possible to discuss the thermodynamics of the diffusion system consisting of the semiconductor samples, Cd3As2 as compound source and additional In or GaAs powder to prevent surface deterioration. Results on Cd concentration profiles, diffusion depth, carrier mobility and activation energy for Cd diffusion are given. The phenomenon of double diffusion fronts obtained in some experiments is discussed.
Temperature variation of the structural and thermal characteristics of YBa2Cu3O7−x in the range from 90 to 400 K
Authors: Olekhnovich N. M. , Zhabko T. E. , Orlova N. S. , Pashkovskii O. I. , Yanovich V. D. , Myaldun A. Z. 
Published: January 2007

AbstractThe X‐ray studies of the tetragonal YBa2Cu3O7−x compound are performed at different temperatures from 400 to 90 K and the temperature variation of the thermal expansion coefficients and the Debye characteristic temperature is determined. The anisotropy of thermal expansion is investigated. It is found that the two dynamical characteristics monotonously decrease with temperature lowering whereas for the superconducting orthorhombic modification their temperature dependences are anomalous. The mean thermal expansion coefficient as well as the overall Debye temperature for the tetragonal phase are smaller than those for the orthorhombic one.
Crystal and molecular structure of tetrachloro tetraaquo‐(1,8,10,17‐tetraazacyclooctadecane‐9,10‐dithione) dicopper (II)
Authors: Mishra Lallan , Pandey A. K. 
Published: January 2007

AbstractTetradentate bioactive macrocyclic thiourea 1,8,10,17‐tetraazacyclooctadecane‐9,18‐dithione(L) has been complexed with copper chloride dihydrate yielding bluish green coloured paramagnetic complex of orthorhombic geometry. The composition and tentative environment around Cu(II) is assigned on the basis of elemental analysis, IR, ESR spectra, X‐ray diffraction and magnetic studies.
Low temperature X‐ray diffraction study of CdI2 crystals
Authors: Wahab M. A. , Trigunayat G. C. 
Published: January 2007

AbstractSolid state structural transformations in polytypic crystals of cadmium iodide have been investigated at low temperatures using X‐ray diffraction techniques. The crystals were cooled to liquid nitrogen and liquid helium temperatures employing three different methods. The results obtained are discussed on the basis of bond dissociation energies of interlayer and intralayer bonds and the possible mode of layer displacements in MX2‐type polytypic crystals.
On the growth kinetics of Y3Fe5O12: Bi films grown from Bi2O3PbOB2O3 melts
Authors: Durčok S. , Pollert E. 
Published: January 2007

AbstractLPE isothermal growth of thin films of Y3−xBixFe5O12 from PbOB2O3Bi2O3 melts was used as a tool for studies of structure of high temperature solutions (HTS). Using an anionic model of HTS enthalpy and entropy of dissolving of the garnet phase, the equilibrium constant of Bi2O3 dissociation and diffusion coefficients of the growth unit were calculated from experimental data.
Structural aspects of thermal instability of polytypes in the CoC system
Authors: Rood' A. D. , Ustinov A. I. , Chuistov K. V. 
Published: January 2007

AbstractThe stability of the irregular long‐period structures being formed in CoC alloys during β → α transformation has been studied according to the carbon content. In the concentration range 0.2 to 1.2 at.% C the type of the short‐range order concerning the atomic layer stacking sequence remains unaffected on subsequent cooling of the alloy, whereas the α‐phase crystalline structure of the alloys with the carbon content of 1.3 to 2.17% C suffers polytype transformation. The transition from one polytype structure to another is found to be due to the decrease in length of the cubic‐type stacking sequences.
Dynamics of structural defects of LPE‐grown Gax‐In1−xP Layers
Authors: Popov A. , Dardjonov St. , Bahnev A. , Petrov Sr. 
Published: January 2007

AbstractThe structural properties of epitaxial GaxIn1−xP, LPE‐grown on 〈111〉‐oriented GaAs‐substrate, have been investigated. Two groups of samples have been distinguished with respect to the lattice parameters of the layers (a1) and the substrate (as): group A with a1 < as and Δa/as = (0.85 ÷ 2.98)%, and group B with a1 > as and Δa/as = (0.11 ÷ 1.98)%. Group A is characterized by a structure, including orthogonal, and slanted at 60° towards the surface, linear dislocations, originating from mismatch ones. Group B is characterized by a segmented‐surface structure. The optimum conditions for the growth of GaInP layers on GaAs substrates (initial temperature, saturation and composition of the melt, as well as cooling rate) are discussed on the basis of the data obtained.