bluuebunny/crossref_metadata_2025 huggingface dataset:
Progenitor Cells from the Porcine Neural Retina Express Photoreceptor Markers After Transplantation to the Subretinal Space of Allorecipients
Authors: Klassen Henry , Kiilgaard Jens Folke , Zahir Tasneem , Ziaeian Boback , Kirov Ivan , Scherfig Erik , Warfvinge Karin , Young Michael J.
Published: January 2007

Work in rodents has shown that cultured retinal progenitor cells (RPCs) integrate into the degenerating retina, thus suggesting a potential strategy for treatment of similar degenerative conditions in humans. To demonstrate the relevance of the rodent work to large animals, we derived progenitor cells from the neural retina of the domestic pig and transplanted them to the laser-injured retina of allorecipients. Prior to grafting, immunocytochemical analysis showed that cultured porcine RPCs widely expressed neural cell adhesion molecule, as well as markers consistent with immature neural cells, including nestin, Sox2, and vimentin. Subpopulations expressed the neurodevelopmental markers CD-15, doublecortin, β-III tubulin, and glial fibrillary acidic protein. Retina-specific markers expressed included the bipolar marker protein kinase Cα and the photoreceptor-associated markers recoverin and rhodopsin. In addition, reverse transcription-polymerase chain reaction showed expression of the transcription factors Dach1, Hes1, Lhx2, Pax6, Six3, and Six6. Progenitor cells prelabeled with vital dyes survived as allografts in the subretinal space for up to 5 weeks (11 of 12 recipients) without exogenous immune suppression. Grafted cells expressed transducin, recoverin, and rhodopsin in the pig subretinal space, suggestive of differentiation into photoreceptors or, in a few cases, migrated into the neural retina and extended processes, the latter typically showing radial orientation. These results demonstrate that many of the findings seen with rodent RPCs can be duplicated in a large mammal. The pig offers a number of advantages over mice and rats, particularly in terms of functional testing and evaluation of the potential for clinical translation to human subjects.

Disclosure of potential conflicts of interest is found at the end of this article.
Transcription Profiling of Adult and Fetal Human Neuroprogenitors Identifies Divergent Paths to Maintain the Neuroprogenitor Cell State
Authors: Maisel Martina , Herr Alexander , Milosevic Javorina , Hermann Andreas , Habisch Hans-Jörg , Schwarz Sigrid , Kirsch Matthias , Antoniadis Gregor , Brenner Rolf , Hallmeyer-Elgner Susanne , Lerche Holger , Schwarz Johannes , Storch Alexander
Published: January 2007

Global gene expression profiling was performed using RNA from adult human hippocampus-derived neuroprogenitor cells (NPCs) and multipotent frontal cortical fetal NPCs compared with adult human mesenchymal stem cells (hMSCs) as a multipotent adult stem cell control, and adult human hippocampal tissue, to define a gene expression pattern that is specific for human NPCs. The results were compared with data from various databases. Hierarchical cluster analysis of all neuroectodermal cell/tissue types revealed a strong relationship of adult hippocampal NPCs with various white matter tissues, whereas fetal NPCs strongly correlate with fetal brain tissue. However, adult and fetal NPCs share the expression of a variety of genes known to be related to signal transduction, cell metabolism and neuroectodermal tissue. In contrast, adult NPCs and hMSCs overlap in the expression of genes mainly involved in extracellular matrix biology. We present for the first time a detailed transcriptome analysis of human adult NPCs suggesting a relationship between hippocampal NPCs and white matter-derived precursor cells. We further provide a framework for standardized comparative gene expression analysis of human brain-derived NPCs with other stem cell populations or differentiated tissues.

Disclosure of potential conflicts of interest is found at the end of this article.
Chronic Myeloid Leukemia Blast Crisis Arises from Progenitors
Authors: Michor Franziska
Published: January 2007

Chronic myeloid leukemia (CML) progresses through three distinct clinical stages: chronic phase, accelerated phase, and blast crisis. The progression to accelerated phase and blast crisis is driven by activation of oncogenes, inactivation of tumor suppressor genes, and/or amplification of the BCR-ABL fusion gene, which causes the chronic phase of the disease. The cell of origin of blast crisis is a subject of speculation. Here, I develop a simple mathematical model of CML blast crisis to investigate whether blasts arise from leukemic stem cells or more differentiated leukemic cells. I use data of patients treated with imatinib and previous agents to estimate the effects of therapy on the rate of progression. Imatinib reduces the progression rate 10-fold as compared with previous (ineffective) therapies. If blasts were produced by leukemic stem cells, there would be no difference in the rate of progression between patients treated with imatinib and previous therapies, because imatinib seems to be incapable of depleting leukemic stem cells. Imatinib does, however, deplete leukemic progenitors. Therefore, CML blasts are likely to arise from leukemic progenitors.

Disclosure of potential conflicts of interest is found at the end of this article.
Erasure of Cellular Memory by Fusion with Pluripotent Cells
Authors: Do Jeong Tae , Han Dong Wook , Gentile Luca , Sobek-Klocke Ingeborg , Stehling Martin , Lee Hoon Taek , Schöler Hans R.
Published: January 2007

Pluripotent cells have been suggested as a prime source to reprogram somatic cells. We used F9 EC cells as a pluripotent partner to reprogram neurosphere cells (NSCs) because they exhibit a nonneural differentiation potential in the presence of retinoic acid. F9-NSC hybrid cells displayed various features of reprogramming, such as reactivation of pluripotency genes, inactivation of tissue-specific genes, and reactivation of the inactive X chromosome. As the hybrid cells undergo differentiation, the pluripotency markers Oct4 and Nanog were downregulated. Whereas neural marker genes were not upregulated, endodermal and mesodermal markers were, suggesting that NSCs lose memory of their neural origin and preferentially differentiate to the lineages corresponding to the F9 program. After fusion, the methylation status in the Xist region was similar to that of F9 EC cells. However, upon differentiation, the Xist region failed to resume the methylation patterns of differentiated cells, suggesting that the Xist in F9-NSC hybrids does not easily acquire a differentiated state.

Disclosure of potential conflicts of interest is found at the end of this article.
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

The 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

Single 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

The 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

The 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

Vapour 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

The 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

Experimental 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

PbxMo6Sy 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

Two 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

Interferometry 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

In 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

By 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

The 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

Influence 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

Transmission 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

This 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

The 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

Gel 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

It 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

Thermal 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

Dislocation 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

The 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

The 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

The 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

For 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

Outgoing 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

The 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

A 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

The 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

Experimentally (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

Al2O3 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%.
Electron Diffraction for the Thermomagnetic Analysis of a Ferromagnetic
Authors: Yamaguchi S.
Published: January 2007

A thermomagnetic analysis of ferromagnetic invar was made by the diffraction procedure utilizing the electorns accelerated over 200 keV. An electron beam served for heating the specimen by electron bombardment. An empirical formula has been proposed for analying the observations.
Effect of Mode of Growth on the Preferred Orientation in Bismuth Single Crystals
Authors: Shah B. S.
Published: January 2007

Melt 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.
Mechanism of Formation of Cadmium Oxalate Liesegang Rings
Authors: Arora S. K. , Abraham Tomy , Godebole R. S.
Published: January 2007

Qualitative and semiquantitative study of the Liesegang rings formed by the reaction of oxalic acid and cadmium chloride in the acidic range of pH in silica hydrogel is made. The behaviour of Jablczynski's space constant and Morce‐Pierce's time constant at various temperatures, pH and concentration of outer electrolyte is studied. The possible mechanisms for the above observed behaviour are suggested. The deviations from Isemura's general obserations are interprerted by considering two particular aspects, viz., comparatively larger crystals constituting the rings and the irreversibility of inner and outer electrolytes.
A thick window pAl0.7Ga0.3As‐pGaAs‐nGaAs concentrator Solar Cell
Authors: Díaz P. , Hernández L. , Rodríguez J. A. , Romero R.
Published: January 2007

Thick window pAl0.7Ga0.3As‐pGaAs‐nGaAs solar cells are reported being grown by forced cooling LPE. Device evaluation shows an 18% maximum conversion efficiency at room temperature.

A method for calculating cell conversion efficiency upon knowledge of internal collection efficiency, open circuit voltage and short circuit current is also devised.
The monoclinic modification of Lead Phthalocyanine – a Quasi‐one‐dimensional Metal with characteristic order of molecular dipoles
Authors: Przyborowski F. , Hamann C.
Published: January 2007

Lead phthalocyanine (PbPc) crystallizes in a monoclinic modification with characteristic order of molecular dipoles. Japanese data on unit cell and space group were not to be confirmed by X‐ray and electron diffraction investigations.

A group‐theoretical classification of energy levels of the molecule may result from the C4v symmetry of the shuttlecock‐like molecule. The space group P 21/b of the crystalline solid leads to the state of an antiferroelectric molecular crystal. In addition to earlier given microscopical explanation of the switching phenomenon a phenomenological solid state model of switching between semiconduction and metallic quasi‐one‐dimensional behaviour of PbPc is given.
A model study of the growth of crystals consisting of a small number of metal atoms by the Hückel molecular orbital method (I). Addition of One atom to small crystals
Authors: Delineshev S. P. , Bliznakov G. M.
Published: January 2007

The paper deals 1) with the regularities of the formation of (N + 1)‐atomic clusters during the growth of N‐atomic one‐, two‐, and three‐dimensional crystals and 2) with the distribution with respect to stability of the (N + 1)‐atomic clusters. The N‐atomic crystals have the structure of a hypothetical metal with a simple cubic lattice and a small number of one‐electron atoms. The binding energy (BE) of the clusters calculated by the Hückel molecular orbital method was assumed to be a measure of their stability. Interactions between nearest‐neighbours only were taken into account.

The most stable (N + 1)‐atomic cluster formed from a one‐dimensional crystal is that in which the N + 1‐st atom is bonded to the end atom of the N‐atomic one‐dimensional crystal.

For two‐dimensional crystals, the N + 1st atom forms the strongest bond with an atom from the diagonal of the square.

With three‐dimensional crystals, the N + 1st atom is most strongly bonded to a corner atom of the small crystal.

The inhomogeneity in the bond energy of the N + 1st atom to a surface atom of the small N‐atomic crystal decreases with increasing N.

According to earlier studies of ours, the BE per atom increases, whereas the mean energy of a nearest‐neighbour bond decreases with increasing N.
Temperature profile and homogeneity of the growth rate of CVD Silicon from SiH4‐HCl‐H2 mixtures
Authors: Kühne H. , Morgenstern Th , Kühne Ch.
Published: January 2007

With the aid of the methods of the statistical design of experiments for each wafer site (x) on the graphite susceptor an empiric polynomial was obtained for CVD epitaxial silicon from SiH4–HCl–H2 mixtures, linking the growth rate vepi to the process parameters p0, p0HCl, and T(x). By means of the statistical model optimum temperatur characteristics along the susceptor were selected and discussed for specific deposition conditions.
Intergrowth and stacking faults in the Sm5Co19 Phase
Authors: Takeda S. , Komura Y.
Published: January 2007

An electron microscope observation was made on the binary Sm‐Co alloy. One‐dimensional lattice images of Sm5Co19 taken with the incident beam parallel to the [010] and [110] directions of the hexagonal axis showed many stacking faults.

The intergrowth with the Sm2Co7 phase was observed in the matrix of the Sm5Co19 phase, the analysis being based on the thickness of blockj layers estimated by the distance of lattice fringes.
Surface Roughness and Kinetics of Spontaneous Transformation of Negative Crystals
Authors: Nenow D. , Trayanov A. , Pavlovska A.
Published: January 2007

Spontaneous isothermal transformation of negative crystals (vapcur inclusions) at temperatures close to the melting point is experimentally studied. Linear dependence of the transformation rate on supersaturation is established. This result shows that the evaporating crystal surfaces of the inclusions are moleculary‐rough. Surface self‐diffusion has no appreciable contribution to the transformation process of the molecularly‐rough surfaces of diphenyl.
Growing Single Crystal Corundum Tubes by Verneuil Technique in Stable Conditions
Authors: Borodin V. A. , Brener E. A. , Steriopolo T. A. , Tatarchenko V. A. , Chernishova L. I.
Published: January 2007

The authors analyze the process of corundum tube growth by modified Verneuil's method from the viewpoint of its stability. The article shows that the process is stable in the case of thin‐walled tubes and becomes unstable when the tube wall thickness exceeds a certain critical value which is known to be below the capillary constant. The critical thickness of the tube wall grows with a decrease of the heat flux density differential from the burner along the furnace muffle and with an increase of the tube's outer radius.

As a result of a process of crystal growth under preset conditions constant cross‐section single crystaal corundum tubes have been obtained.
Kinetics of the Incorporation of Dopants into Epitaxial CVD Silicon
Authors: Kühne H.
Published: January 2007

Starting from the gas‐phase‐transport‐controlled and reaction‐controlled incorporation mechanisms and the equilibrium incorporation of the dopants a critical study of the adsorption model is carried through, as a result of which a model of adsorption is proposed. This modified model reflects the incorporation concentration of the dopants as a function of the layer growth rate and contains the equilibrium incorporation of dopants as a border‐line case for a layer growth rate of zero.
Influence of Quenching on Microhardness and Dislocation Mobility of Doped NaCl Crystals
Authors: Boyarskaya Yu. S. , Zhitaru R. P. , Linte M. A.
Published: January 2007

The effect of quenching on microhardness and dislocation mobility of NaCl:Ca and NaCl:Pb single crystals was studied. Both the decrease and increase of these parameters in quenching occurred depending on the type and concentration of impurity and quenching temperature. The absence of correlation between the changes of microhardness and those of dislocation ensemble mobility which resulted from the quenching, has been found first. The conditions of the observation of this phenomenon were revealed and the interpretation of the experimental facts was proposed.
The Influence of the Frequency on the Electrooptic Behaviour of Liquid Crystalline 4,4′‐Bis‐n‐pentyl‐azoxybenzene
Authors: Kresse H. , Keil M. , Deresch S. , Spott G. , Demus D.
Published: January 2007

The threshold voltage and the rise time of planar, homeotropic and twisted nematic layers were investigated in dependence of the frequency and the temperature. A strong increase of threshold voltage and rise time could be observed in the region of the dielectric relaxation frequencies between 0.1 and 1 MHz. The results were compared with those of the dielectric measurements.
An analysis of the behaviour of the sead crystals in batch crystallization
Authors: Baumann Karl‐Heinrich
Published: January 2007

The population density function of seed crystals, well defined at the beginning of batch crystallization experiments undergoes a strong deformation in the course of the process. A mathematical model, developed on the base of the generally accepted equations of the kinetics of crystallization and the population balance as a function of the crystal size and the process time is not suitable to describe such a behaviour.
Incorporation of dopants into epitaxial CVD‐Silicon layers and incorporation equilibrium
Authors: Kühne H.
Published: January 2007

Based on the temperature dependence of the layer growth rate influence on the incorporation of dopants into epitaxial silicon the range of validity of an incorporation equilibrium between dopants in the gas phase and in the layer is discussed. Additional to the borderline case of an infinitely low layer growth rate the incorporation equilibrium is equally important to high layer deposition temperature. For this region deducing the incorporation enthalpy from the temperature dependence of the incorporation of dopants proves adequate.
Proposal for general principles for the construction of fully descriptive polytype Symbols
Authors: Dornberger‐Schiff K. , Ďurovič S. , Zvyagin B. B.
Published: January 2007

Experience with polytype families of layered structures and the theory of OD structures consisting of layers made it possible to elaborate generally applicable principles for a full description of polytypes by symbols. According to these principles, the exact stacking sequence of building layers (BLs) in any given polytype may be described by a symbol which, in general, has the form
The Behaviour of Zinc in GaP Synthesis by the SSD Technique
Authors: Koi H. , Buhrig E. , Hein K. , Geidel B.
Published: January 2007

In this paper the principle of GaP synthesis by the SSD technique is described followed by a discussion of the results obtained in studying the transfer of an impurity such as the highly volatile zinc from the phosphorus source or gallium melt into GaP crystals. The radionuclide Zn65 was used as a tracer to determine the concentrations of zinc in the phases involved in the process of synthesis. The results of these studies are compared with calculated values.
Facet Formation on Near (111) Silicon Surfaces and the Desorption Energy of SiCl2 Adatoms
Authors: Van Der Putte P. , Giling L. J. , Bloem J.
Published: January 2007

Silicon wafers which have a small misorientation from (111) become facetted, when they are etched beyond a critical HCl concentration. This facetting can be explained by the action of a second etch mechanism which directly attacks the surface between the steps. In this way enough new steps are generated to give a proper response to the desired etchrate. In BCF language: the spiral dissolution around a dislocation containing a screw component can become dominant over the etching process which occurs by a set of parallel steps, when beyond a critical HCl concentration the density of steps inside the shallow pit exceeds the density of the parallel steps due to the original misorientation. From the slope of the shallow pits at the critical HCl concentration a desorption energy for SiCl2 adatoms of around 60 kcal/mole could be calculated.
The Influence of High Temperature Predeformation on Ductility of LiF and BaF2 Single Crystals
Authors: Berezhkova G. V. , Skvortzova N. P. , Chormonov T. H.
Published: January 2007

The effect of high temperature predeformation on deformation characteristics of ductile LiF and brittle BaF2 crystals was investigated. The same predeformation, as has been shown previously, leads to the increasing of the limited plastic deformation of MgO crystals by one order of magnitude. It was found that in both investigated crystals, as in the case of MgO crystals, at the test temperature T2 ≅ 0.1 Tm limited plastic deformation before fracture obviously increases if the specimen was prestrained up to εp ≦ 1% at T1 = 0.5 Tm. This increase is as higher as the plasticity of crystal is lower. In BaF2 crystals it reaches a factor of 20 and more. The effect is connected with the creation of mobile dislocations during the high temperature predeformation and dislocaton sources for subsequent deformation at lower temperatures and with the homogeneity of the process of plastic deformation. These conditions prevent the appearance of dangerous places in which the fracture can begin.
Stress relaxation in the intermetallic phase V3Si at elevated temperatures
Authors: Bertram M. , Paufler P.
Published: January 2007

The plastic deformation behaviour of the intermetallic phase V3Si (Cr3Si‐type) was investigated in stress relaxation experiments. The experiments revealed that V3Si shows stress relaxation after dynamic deformation above 1550 K. The characteristic parameters of stress relaxation depend strongly on temperature, chemical composition (within the range of homogeneity) and deformation rate. The decrease of stress is governed by dislocation climb processes.
Amorphousness of metalloid ion implanted metals as a function of irradiation dose
Authors: Rauschenbach Bernd
Published: January 2007

Ion implantation into crystalline metals at room temperature an at lower temperatures can result in the formation of amorphous phases. The effect of dependence of amorphization on the implantation dose due to the impact of metalloid ions into metals is described by a model based upon the theory of critical energy density. Comparison is made to experimental results.
Effect of plastic deformation of the thermoluminescence of γ‐irradiated NaCl and KCl Crystals
Authors: Chandra B. P. , Elyas M. , Kathuria S. P.
Published: January 2007

The overall thermoluminescence (TL) intensity of γ‐irradiated NaCl crystals initially increases and then decreases with the number of newly‐created dislocations. However, the overall TL intensity of γ‐irradiated KCl crystals increases with the increasing number of newly created dislocations. The TL spectra are recorded for different plastic deformations at different temperatures. It is found that the plastic deformation has no considerable effect on the TL spectra of γ‐irradiated NaCl and KCl crystals. Trap destruction model and trap competition model are discussed for the decrease in the TL intensity with deformation of the crystals. The physical ideas behind the increases in the relative intensity of glow peaks and the appearance of new glow peaks are explored.
The role of iron ions in YAG and YAP
Authors: Kvapil Josef , Kvapil Jiři , Kubelka J. , Autrata R.
Published: January 2007

Spectroscopic properties of YAG and YAP doped with Fe were compared. YAG :Fe crystals grown under reducing atmosphere showed strong colouration whereas similar colouration in YAP :Fe was found after oxygen treatment. Nd3+ luminescence was effectively quenched by Fe ions in YAP, whereas Ce3+ luminescence was quenched by Fe ions in both the materials.
Effect of grinding on the low temperature photoluminescence of certain inorganic crystals
Authors: Chandra B. P. , Majumdar B.
Published: January 2007

The broadening as well as shift in the photoluminescence spectra of K2[Pt(CN)4] · 3 H2O, Ba[Pt(CN)4] · 4 H2O, CdS:Te and Ru(C15H11N3)2I2 · H2O crystals take place with their grinding. The original vibronic peaks at 632 and 628 nm of CdS:Te and Ru(C15H11N3)2I2 · H2O crystals, respectively, disappear with the grinding. A new vibronic peak at 650 nm appears with grinding of Ru(C15H11N3)2I2 · H2O crystals. It is concluded that the change in the photoluminescence spectra is attributed to the creation of dislocations during the process of grinding.
On the computer simulation of many‐beam electron microscopical images of phyllo‐silicates
Authors: Heydenreich J. , Hillebrand R. , Werner P.
Published: January 2007

The polytypism of pyrophyllite as a special phyllo‐silicate is investigated by means of high resolution electron microscopy (HREM), supported by computer simulation. Electron micrographs of appropriate specimen orientations provide crystal structure images, which reveal the actual stacking sequence of the silicate layers. Two crystallographic models (2M1‐ and 1Tc‐type) are applied for the numerical simulation of the image contrast. The process of the electron scattering in the crystal as well as the influence of the imaging parameters are described by means of multi‐slice image calculations. The strong effect of through‐focusing to the image contrast of the silicate structure is pointed out.
Modification of the smectic B phase by the aid of dielectric relaxation
Authors: Kresse H. , Gajewska B.
Published: January 2007

The analysis of the dielectric relaxation data in the liquid crystalline SB phase allow to classify the substances into two groups: SB phases which are similar to the low or high temperature modifications. The experimental results are correlated to the recently discussed „heaxtic”︁ and „solid like”︁ SB modifications.
Influence of gravitation on the processes of heat and mass transfer in solution crystal growth by the travelling heater method (THM) (III)
Authors: Cherepanova T. A. , Apanovich Y. V.
Published: January 2007

The effect of the natural and thermocapillary convection on the vortex configuration in solution during growth of PbTe crystal by the travelling heater method is considered. The estimation of the parameters of growth process (i. e. axial temperature gradients, gravitational acceleration, degree of the solution's surface contact with ampoule), when the vortex configuration undergoes qualitative variation, is given. In terms of the one‐dimensional thermodiffusive problem solution the effect produced by the convective stirring on the position of growing and dissolving interfaces is described.