bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exploiting the pressure effect on lipase‐catalyzed wax ester synthesis in dense carbon dioxide
Authors: Knez Željko , Laudani Chiara Giulia , Habulin Maja , Reverchon Ernesto 
Published: January 2007

AbstractThe present work focuses on the thermodynamic interpretation of the lauryl oleate biosynthesis in high‐pressure carbon dioxide. Lipase‐catalyzed lauryl oleate production by oleic acid esterification with 1‐dodecanol over immobilized lipase from Rhizomucor miehei (Lipozyme RM IM) was successfully performed in a sapphire window batch stirred tank reactor (BSTR) using dense CO2 as reaction medium. The experiments were planned to elucidate the pressure effect on the reaction performance. With increasing the pressure up to 10 MPa, the catalytic efficiency of the studied enzyme improved rising up to a maximum and decreased at higher pressure values. Kinetic observations, exhibiting that dense CO2 expanded reaction mixture in subcritical conditions led to higher performance than when diluted in a single supercritical phase, were elucidated by phase‐equilibrium arguments. The experimental results were justified with emphasis on thermodynamic interpretation of the studied system. Particularly, the different reaction performances obtained were related to the position of the operating point with respect to the location of liquid–vapor phase boundaries of the reactant fatty acid/alcohol/CO2 ternary system. The outlook for exploitation of CO2 expanded phase at lower pressure compared to supercritical phase, with heterogeneous system in which the solid catalyst particles are exposed to dense CO2 expanded reaction mixture, in developing new biotransformation schemes is promising. Biotechnol. Bioneg. 2007;97: 1366–1375. © 2007 Wiley Periodicals, Inc.
Optical and X‐ray Topographic Studies of Barium Fluoride Single Crystals
Authors: Desai C. C. , George K. V. 
Published: January 2007

AbstractSingle crystals of synthetic barium fluoride have been cleaved along {111} planes and the freshly cleaved faces have been etched in (1 : 250) concentration of nitric acid solution. One to one correspondence of dislocation etch pits have been observed on matched pairs. The same crystal has been investigated using X‐ray topographic technique. By selecting 0222 and 0222 reflections and MoKα1 radiation, stereopair projection topographs have been obtained and critically compared with the optical micrograph. One‐to‐one correspondence between dislocation out crop images and dislccation etch pits have been established. Due to dislocation contrast, the outcrop of dislocation images have been observed with the associated dislocation etch pits. The orientation of the Burgers vectors of the dislocation lines have been identified using AgKα1 radiation with 1111, 1111 and 1111 reflections and the implications have been discussed.
Dielectric and Electrooptic Investigations in the Nematic Phase of 5‐n‐Pentyl‐2‐[4‐n‐nonyloxyphenyl]‐1,3‐dioxane
Authors: Kresse H. , Keil M. , Vorbrodt H. M. , Zaschke H. , Demus D. 
Published: January 2007

AbstractThe dielectric constant and the dielectric loss of 5‐n‐pentyl‐2‐[4‐n‐nonyloxyphenyl]‐1,3‐dioxane were investigated in the region of 0.1 to 10 MHz. An isotropy temperature was detected, at which the static dielectric anisotropy Δε01 = 0. Using both the Freedericksz and the DAP effect, we measured the frequency dependence of the threshold voltage U0 and compared the results with those of the dielectric measurements. In the case of DAP effect we could find two different types of dispersions curves of U0.
Dissolution of Si in Al–Si Melts. Effect of Sb on the Crystallization Process and As‐cast Structure of Al–Si Alloys
Authors: Yaneva S. B. , Stoichev N. V. , Panajotova A. D. 
Published: January 2007

AbstractThe effect of Sb on the dissolution of Si single crystals (face {111}) in Al–Si melts is studied. The dissolution isotherms at three temperatures and fixed undersaturation are obtained. The experimental data are treated according to the Bliznakov's ratio. Some conclusions are made with reference to the crystal growth process. A probable mechanism of the influence of Sb on the structure of Al–Si alloys is given.
Deposition of InP on GaAs Substrates in the InP/PCl3/H2 System
Authors: Wagner G. , Kühn G. , Neumann H. , Nowak E. 
Published: January 2007

AbstractVapour phase epitaxial layers of InP were deposited onto (111)A‐, (111)B‐, (001)‐, and (110)‐oriented GaAs substrates in the InP/PCl3/H2 system using a close‐space technique. It is shown that the dependence of the layer quality on the substrate orientation is due to differences in the initial growth stages. Results on the growth rates and the electrical properties of the layers are reported.
Growth Kinetics of Barium Sulphate in Suspension
Authors: Hostomský J. , Rathouský J. , Skřivánek J. 
Published: January 2007

AbstractThe growth rate of barium sulphate seed crystals from stirred solutions was studied conductometrically at 25°C by a stopped‐flow technique. The supersaturation ranged from 3 × 10−7 to 3 × 10−8 mol BaSO4/cm3. The seed crystals were grown in the system during the initial (steady‐state) period of the experiment. Crystal size distributions were determined by optical microscopy. The growth rate of barium sulphate under the conditions of the experiments can be expressed by a quadratic function of supersaturation. The results, which suggest an interface rate‐controlling mechanism, are discussed with respect to published data.
Experimental Evidence for a Step Growth Mechanism of Garnet LPE Films
Authors: Hergt R. , Bürger W. 
Published: January 2007

AbstractExperimental observations suggesting a lateral growth mode at {110} and {211} garnet LPE films are reported. Growth steps are revealed using a gold decoration technique and a new decoration method based on the condensation of PbO nuclei is developed which allows to image the step structure of the whole film surface using light optical interference contrast. The step velocity reduced per K undercooling of spiral steps having step distances larger than 100 nm amounts to (0.70 ± 0.10) μm/min ± K independently of step density. Spiral rotation rates and critical nuclei radii are in the order of 1 s−1 and 10 nm respectively.
The Phase Diagram of the Pb–Mo–S System at 1250 K and Some Properties of the Superconducting PbMo6S8
Authors: Krabbes G. , Oppermann H. 
Published: January 2007

AbstractPbxMo6Sy arises as the sole ternary compound in the System Pb–Mo–S. At 1250 K it is surrounded by 4 phase regions with 3 solid phases. It has a homogeneity range of between 0.9 ≤ x < 1.1 and 7.6 ≤ y > ≤ 7.9. Tc changes within the homogeneity range. Chemical transport is possible within a limited section of the phase diagram in the presence of lead halides.
Isochronal Phase Transformation in AlZnCu Alloys
Authors: Wendrock G. , Major B. , Löffler H. , Grabianowska K. , Ciach R. 
Published: January 2007

AbstractTwo Al‐Zn alloys with 40 wt% and 74wt% Zn, respectively, and copper additions between 0 and 10 wt% were investigated by means of X‐ray diffraction methods, X‐ray small angle scattering, resistivity, and dilatometric investigations during continuous cooling from 673 K applying a cooling rate of 2 K/min.It was found that copper additions lower the driving forces for the onset of the homogeneous nucleation after crossing the range of homogeneity, but accelerate the formation of the η‐phase. The reasons for this facts are discussed.
Concentration Non‐homogeneity during Electrocrystallization
Authors: Nanev Chr. , Dyulgerov A. 
Published: January 2007

AbstractInterferometry has been applied by the direct measurement of the concentration distribution around a silver single crystal growing electrochemically in a thin (100 μm thick) cell. It has been shown that due to the cell thickness the natural convections do not play any appreciable role, and the process is essentially diffusion controlled. The morphological stability of the growing crystal has been studied and electrolytic whisker formation was observed. Some preliminary results concerning a.c. effect on the diffusion field surrounding the crystal were obtained as well.
Growth of Large Needles and Single Crystals of PbCl2 and PbBr2 in Silica Gel. An Improvement of the New Gel Technique
Authors: Abdulkhadar M. , Ittyachan M. A. 
Published: January 2007

AbstractIn growing crystals by the new gel technique a principal difficulty may arise in that it may be difficult or at times impossible to choose two nutrients that may react to produce the desired crystals. With some crystals, the pair of nutrients that may appear practically most suitable, may not react at all or the rate of reaction may be exceedingly small. Further work on the new gel technique has now led to an improvement of the technique by which it is feasible to impart activity to nutrients which are normally non‐reactive or to enhance the reactivity of generally less reactive nutrients. Large needles of PbCl2 and PbBr2 have been grown in silica gel by this improvement of the new gel technique. The interesting phenomenon of transformation of needles of PbCl2 and PbBr2 into single crystals has been investigate and the various aspects of growth systematically studied.
Investigation of Boron Distribution in Solids Demonstrated in Nickel and in Silica Glass
Authors: Rattke R. , Boden G. 
Published: January 2007

AbstractBy means solid state track autoradiography has been demonstrated that boron is enriched on grain boundaries of nickel and on texture boundaries of silica glass. This result has been proved on nickel by SIMA and on silica glass by luminescence autoradiography.
Stability of Electronic Colour Centres in NaF:Li Single Crystals
Authors: Alybakov A. A. , Denisov G. S. , Pankov P. S. , Umurzakov B. S. , Chebotareva E. B. 
Published: January 2007

AbstractThe influence of the lithium impurity on the formation and the stability of electronic colour centres is studied in NaF crystals. It is found that F‐ and M‐absorption bands are somewhat displaced to the long wavelengthes when doping with lithium owing to the overlapping with FA‐ and MA‐absorption bands. It is shown that the lithium impurity is stabilising one for the charged M‐centres though their accumulation in the doped crystals occurs slower. The activation energy is determined for the thermal destruction of M+‐ centres. Thermal destruction of M+‐centres assumed to be resulting from the anion vacancy removal.
Factors influencing the periodic precipitation of BaMoO4 crystals in silica gel
Authors: Kurien K. V. , Vaidyan V. K. , Ittyachen M. A. 
Published: January 2007

AbstractInfluence of electric and magnetic fields on the periodic precipitation of BaMoO4 crystals in Silica gel has been discussed. The retarding effect of gel density on the advancing precipitation front has been qualitatively analysed. The role of impurity on the formation of rings has been investigated.
Precipitation of supersaturated chromium solutions in gallium arsenide
Authors: Bochkareva V. A. , Maksimov S. K. , Sokolov E. B. 
Published: January 2007

AbstractTransmission electron microscopy has been used to investigate precipitation processes in gallium arsenide doped with chromium and Cr2O3. Whatever the doping technique, at concentrations of chromium 4 × 1016 cm−3 the solid solution was observed to contain precipitates which grew, at least partially, due to the migration of substitutional atoms and their transformation into the precipitates. The process is accompanied by generation of vacancies from dislocation loops.
The melt temperature change influence on the crystallization rate in czochralski growth system
Authors: Nalbandyan H. G. 
Published: January 2007

AbstractThis paper opens a series of publications about growth system parameters change influence on the crystallization rate. The influence of crucible melt temperature fluctuations and mechanical instability will be investigated. In approximation of one‐dimensional heat transfer the behaviour of crystallization rate in case of crucible melt temperature small change is investigated in this paper. As an example characteristic time values and system sensitivity are given for fluorite and silicon crystals.
The effect of mechanical instability on crystallization rate in czochralski growth system
Authors: Manucharyan S. M. , Nalbandyan H. G. 
Published: January 2007

AbstractThe effect of mutual displacement of crucible and crystal or melt level change on crystallization rate is described in one‐dimensional heat‐transfer approximation. It is found that Czochralski growth system is very sensitive to mechanical instability and crystallization rate follows the jitter pattern. As an example crystallization rate behaviour is examined for fluorite and silicon crystal growth.
Investigations of the growth mechanism and morphology of silver crystals grown electrolytically in gels
Authors: George M. T. , Vaidyan V. K. 
Published: January 2007

AbstractGel medium has been used for the electrolytic growth of silver dendrites and single crystals of a variety of morphological features and forms. Microtopographic studies of the crystals have been carried out using optical and scanning electron microscopes. Some unusual growth surface morphologies have been observed. The surfaces of some of the crystals have a high degree of perfection. Sufficient experimental evidences are obtained for the striated growth of crystals and twin plane re‐entrant edge (TPRE] mechanism of growth. The formation of tertiary three‐dimensional (T3D) dendrites and dendrites with obliquely forward and backward branchings at different stages of growth have been investigated.
On the Codepositon of Silicon and Boron (II) The Influence of Traces of Water Vapour on the Codepostion of Silicon and Boron
Authors: Bartsch K. , Wolf E. 
Published: January 2007

AbstractIt has been proved experimentally that at the codeposition of silicoan and boron at low concentrations of boron, being comparable with the residual water vapour of the gases, gaseous phase reactions ake place, decreasing the incorporation of boron in the deposited silicon. Probably silioxy‐boron‐halides are formed in these reactions.
Thermal Etching on Calcite Cleavages
Authors: Mehta B.J. , Pandya J.R. 
Published: January 2007

AbstractThermal etch pits are observed on calcite cleavages at very small range of temperatures in atmosphere. Different characteristics such as nonmovement of cleavage lines and dislocations, thermal percussion by gas molecules, are observed in thermal etching. It is found that chemical and thermal etching are not the same process for calcite cleavage etching. The origin of thermal etch pits is not at dislocations intersecting the cleavage surfaces.
Etching and Dissolution Mechanism of Cadmium Oxalate Trihydrate Crystals
Authors: Arora S.K. , Abraham Tomy 
Published: January 2007

AbstractDislocation etching and dissolution of gel‐grown cadmium oxalate trihydrate crystals are carried out using different etchants. The study revealed the existence of dislocation network in the body of the crystal and shallow dislocation loops in the substructure. Faster dissolution of the crystal at elevated temperatures revealed that the rate of dissolution in the initial part of the dissolution time is much lesser, which increases fast to attain a steady value. This observation is related to the available specific surface area of the crystal.
The Influence of the Dispersion and Vertical Divergence on the Reflection Curve of a Double‐crystal Arrangement
Authors: Brümmer O. , Eisenschmidt CH. , Nieber J. 
Published: January 2007

AbstractThe influence of the dispersion and vertical divergence on the half width of the reflection curves was investigated using a double‐crystal arrangement where the second crystal could be rotated about an axis parallel to the beam reflected by the first crystal. The experimentally measured dependence of the half width of the reflection curves on the angle of rotation φ is accurately confirmed by geometrical considerations.
Plateau Behaviour of Fatigued FCC Single Crystals
Authors: Blochwitz C. , Veit U. 
Published: January 2007

AbstractThe mechanical behaviour of fatigued pure nickel monocrystals oriented for single slip was studied in push‐pull tests at room temperature. Especially the cyclic hardening curves, the cyclic stress‐strain curve and the shape changes of the hysteresis loops were investigated in the range of the plastic resolved shear strain amplitude, γap, between 10‐10 and 10‐2. In this range the cyclic stress‐strain curve exhibits a plateau which is related to plastic strain localization in persistent slip bands (PSBs) developing within the residual “matrix” volume. Using a two‐phase model the cyclic saturation mechanical behaviour of the PSB and the matrix volumes has been determined. An explanation has been given of the constant plateau stress τB of the cyclic stress‐strain curve by taking into account the nucleation stress for PSBs depending on the plastic resolved shear strain amplitude of the matrix volume. Further, the propagation rate of PSBs after strain amplitude increase in the plateau range has been calculated by applying the two‐phase model.
On the Binding in Two‐component Nitrides
Authors: Schubert K. 
Published: January 2007

AbstractThe usual classification of nitrides into ionic, metallic, diamond like, and covalent phases is refined by analyzing the spatial correlation of the valence electrons (b correlation) and of the peripheral core electrons (c correlation). When the valence electrons of the N‐atoms take part in the b correlation then the octet rule is obeyed and ionic or covalent nitrides are formed; when the valence electrons of the N‐atoms take part in the c correlation then either azides or metallic interstitial structures are formed, depending on whether the metal contributes sp electrons or d electrons into the c correlation. The interstitial nitrides with NaCl structure owe their stability to the participation of an additional e correlation in the binding. The occurrence of stacking homeotypes of the NaCl structure is related to the c correlation which is filled by d electrons of the T‐atoms and by the valence electrons of the N‐atoms. The Bn nitrides follow the octet rule which stabilizes the B3N compounds at the equiatomic composition. The diamond type is not formed, instead the related ZnO (H2.2) type is formed as a cC̃ correlation may become stable here. The analysis of the binding in Si3N4 shows that the structural transformation Si3N4 · h → Si3N4 · r is caused by increasing Hund insertion with decreasing temperature. The possibility of the present binding classification confirms that the two‐correlations model is a valence model also for nitrides.
On the Influence of the Distortion Distribution on the Determination of Roentgenographic Particle Sizes and Distortions (I) Introduction and Calculation of Distortion Distributions
Authors: Röll H. , Schulz H. 
Published: January 2007

AbstractFor a cylindrical crystallite with an axial edge dislocation the reentgenographic distortion distributions for the inserted half plane, respectively the glide plane in interference position are calculated. Both differ from each other essentially and also differ from a Gaussian distribution, respectively from the distrtion distributions of “simple” elastic distortion models, moreover they show a distinct depedency of the Fourier order.
The IR Television Scanning Technique as Temperature Field Control for Growing Silicon Crystals
Authors: Geil W. , Malitzki H. , Tänzer D. 
Published: January 2007

AbstractOutgoing from the idea that the temperature field of the growing crystal is the most general as well as characteristic representation of all technological parameters and equipment conditions the ir‐television scanning technique was as a method for recording and controlling of temperature distributions at the surface of growing crystals and melts. Using a number of electronic treshold value switches, some video signal amplitude levels can be made visible at the monitor, giving an overlook on the isotherm distribution at the crystal surface. Records of such observations are helpful for reproduction and optimization of crystal growth technologies. For Silicon crystal growth, the process control by ir‐television scanning technique is a fast, convenient, and nondisturbing one giving important informations.
The Rate of Growth of Crystals from a Ca(NO3)2 · 4DMSO Melt
Authors: Paćk P. 
Published: January 2007

AbstractThe rate of growth of crystals from a melt containing the tetrasolvate of calcium nitrate with dimethylsulphoxide was measured in dependence on the supercooling (ΔT = 1–46°C) and the results were compared with the system containing the tetrahydrate of calcium nitrate. It was concluded from the results obtained that the growth mechanism is similar in the two systems.
Investigation of Aluminium Solubility Process in Silicon Carbide
Authors: Lilov S.K. 
Published: January 2007

AbstractA thermodynamic analysis of the aluminium solubility process in silicon carbide has been carried out taking account of the electron‐hole interaction. The partial mole heat of aluminium dissolving in SiC was determined on the basis of the thermodynamic analysis of the interaction process in the system SiC–Al, on the dependence of aluminium solubility in SiC on the temperature as well as on the calculation of the Fermi level and other parameters.
Formation Entropy of Schottky Defects and Free Formation Enthalpy of Vacancy Pairs in Alkali Halide Crystals
Authors: Bollmann W. 
Published: January 2007

AbstractThe melting of alkali halides occurs probably at a critical mole fraction xc = 3.2 · 10−4 of thermally created vacancies (Schottky defects). Using this value the formation entropy of Schottky defects is found to be sS = (962.1 K mol/kJ L/Tm – 16.1) k (L, Tm heat and temperature of fusion, respectively). As to the free association enthalpy gA = hA – TsA of (impurity‐vacancy) complexes it is sA = (10.8 hA/eV – 2.56) k. Using this relation the concentration vacancy pairs is found to be smaller than that of isolated vacancies up to the melting point.
Kink‐band Formation
Authors: Urusovskaya A. A. , Chernysheva M. A. , Klassen‐Neklyudova M. V. 
Published: January 2007

AbstractExperimentally (by filming and selective etching methods) and theoretically (by means of the analysis of stress distribution near breaks on the surface at places where kink‐band boundaries are nucleated) mechanism of kink‐band generation and developing is investigated.
Spectral Properties of Oxide Crystals Free of Iron Ions
Authors: Kvapil J. , Perner B. , Kvapil JoS. , Mánek B. , Kubelka J. , Blažek K. , Austrata R. , Schauer P. , Vitamvás Z. 
Published: January 2007

AbstractAl2O3 and YAG crystals were purified from traces of iron by the growth in reducing atmosphere. Luminescence output of such materials was substantially increased, but some undesirable properties as transient colour centre formation in YAG: Nd and low damage threshol of ruby laser rods were observed. Minimum concentration of iron ions which drastically change spectral properties of oxide crystals seems to be ⪅ 10−4 wt%.
Effect of Mode of Growth on the Preferred Orientation in Bismuth Single Crystals
Authors: Shah B. S. 
Published: January 2007

AbstractMelt growth involves mass transfer in a heated fluid, and an analysis of this problem needs a knowledge of the thermal, concentration and other boundary conditions. The geometry of the crystal growing apparatus also has significant influence (Pimpatkar, Ostrach). The factors affecting the orientation in bismuth single crystals have been studied (Bhatt; Shah). In this communication results of the effect of the mode of crystal growth on the preferred orientation are presented.