bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal and Molecular structure of 3,3‐Diethyl–2,4,6–[1 H,3 H,5 H] Pyrimidine Trione
Authors: Sambyal Vinod Singh , Goswami K. N. , Khajuria Ravi Kant
Published: January 2007

C8H12O3N2, Mr = 184.19, Trigonal, R3 (hexagonal axes) a = b = 26.800(1) Å, c = 6.828(3) Å, α = β = 90°, γ = 120°, V = 4247.11 Å3, Z = 18, Dm = 1.297 Mg m−3, Dc = 1.296 Mg m−3, mu = 0.79 mm−1, F(000) = 1764, T = 293 K, final R = 0.080 for 1205 observed reflections. There are two crystallographically independent molecules in the unit cell of the title compound.
Positron Lifetime and Defects in Y‐doped (Ba0.6Sr0.4)TiO3 Ceramics
Authors: Tang C. Q. , Zhang D. M. , Xue Q. Z.
Published: January 2007

The positron lifetime spectra in Y‐doped (Ba0.6Sr0.4)TiO3 ceramics have been measured at room temperature for Y contents of 0–0.8 at. %. It was found from the experiments that with increasing Y content, the variation of the positron lifetime parameters is nonmonotonic, and the Y content corresponding to the knee is about 0.7 at. %, which is much larger than the La content corresponding to the knee in the La‐doped BaTiO2 (TANG 1994a). The experimental results show that the Y ions substitute predominantly for Sr ions, and this substitution induces a large number of Sr vacancies; when the Y content increases to about 0.7 at. %, the Y ions begin to substitute for Ba ions, and then the associated defects (2 YBaV“SrSr) and (2 YSrV”BaBa) form gradually.
Optical Absorption Spectrum of Co2+ Ion Impurities in Lithium Sodium Potassium Sulphate Single Crystal
Authors: Kumar R. Rama , Reddy Prof. Dr. B. C. Venkata
Published: January 2007

Optical absorption spectrum of Co2+ ions doped in lithium sodium potassium sulphate single crystal has been studied at room and liquid nitrogen temperatures. The observed bands are assigned as transitions from the ground 4T1g(F) to various excited quartet and doublet levels of Co2+ ion in octahedral symmetry. The splitting in one of the bands at liquid nitrogen temperature has been explained as due to spin‐orbit interaction. All the observed band positions have been fitted with the parameters B, C, Dq and ζ.
Hardness of Crystals with NaCl Structure and the Significance of the GILMAN‐CHIN Parameter
Authors: Sirdeshmukh D. B. , Subhadra K. G. , Kishan Rao K. , Thirmal Rao T.
Published: January 2007

The microhardness of PbTe, PbSe, EuS and EuSe has been determined. The microhardness vs lattice constant plot for chalcogenides is a curve similar to the one for alkali halides. The Gilman‐Chin parameter (H/C44) has been calculated for a large number of crytals with NaCl structure. There is no unique value representing the entire group of crystals, the values ranging from 0.01 to 0.20.

The Gilman‐Chin parameter broadly correlates with the effective ionic charge (e) indicating that it is a measure of the ionicity. Empirically, it is observed that the product (H/C44) · (e)2 is approximately constant.
Investigation of Thermoelectric Power of Ga2Se3 Monocrystals
Authors: Gamal G. A. , Elshaikh H. A.
Published: January 2007

Single crystals of Ga2Se3 were prepared by a technique based on the Bridgman method. Thermoelectric power was investigated in the temperature range 160–525 K. From this investigation many physical parameters such as effective masses of charge carriers, carrier mobilities, diffusion length, diffusion coefficient, and the relaxation time for both majority and minority carriers were estimated. In conjunction with the electrical conductivity and the charge carrier concentration, the thermoelectric power is discussed.
Growth of Semiinsulating GaAs Crystals by Vertical Gradient Freeze Technique
Authors: Frank C. , Hein K.
Published: January 2007

GaAs crystals having dislocation densities of 1–2 103 cm−2 were grown using VGF technique. In the grown crystals SiGa is the dominant donor and CAs the dominant acceptor. Theoretical and experimental investigations have shown the possibilities to influence on the silicon and carbon content in GaAs. Based on these results, semiinsulating properties in the crystals could be achieved reproducibly.
Electric and Dielectric Evaluation of KDP
Authors: Parmar S. G. , Chaudhari S. K. , Arora S. K.
Published: January 2007

Single crystals of potassium dihydrogen phosphate, KH2PO4 (KDP), grown by isothermal evaporation at room temperature have been characterized by their measurement of electrical conductivity and dielectric behaviour. Implications in respect of practical utility of KDP crystals in devices have been given.
Dual action of Impurities in Crystal Growth from Solutions
Authors: Alexandru Horia V.
Published: January 2007

A dual action of impurities becomes evidently in growth kinetic of prismatic faces of KDP. At higher supersaturation two‐dimensional nucleation mechanism due to impurities prevails. At smaller supersaturation the blocking effect of the steps created by the dislocation mechanism of growth become efficient. The limit of the “dead” growth zone depending on the impurity's concentration and the solution pH is a result of this last effect and agrees with the Cabrera‐Vermilyea mechanism.
Interface Shape Studies for Fluoride‐ and Silicon Rods Grown by the E.F.G. Method
Authors: Nicoara Irina , Vizman Daniel
Published: January 2007

The influence of the die geometry and of the thermal conductivity of materials on the solid‐liquid interface shape in Edge‐defined Film‐fed Growth has been studied.
Crystal Structure of 5,7‐Dimethoxy‐8‐(2‐oxo‐3‐methylbutyl)‐2 H‐1‐benzopyran‐2‐one (Isosibiricin)
Authors: Singh Attar , Gupta Vivek K. , Rajnikant  , Goswami K. N.
Published: January 2007

The title compound, C16H18O5, a simple coumarin crystallizes in the monoclinic space group P21/c with unit cell parameters a = 7.321(3), b = 21.111(9), c = 11.649(3) Å; β = 123.14(2)°. The structure has been solved by direct methods. The coumarin ring system is planar. The methoxy groups at C5 and C7 are almost coplanar with the coumarin mean plane. The crystal structure is stabilized by C–H… O hydrogen bonds.
Crystal Growth and Differential Thermal Analysis of AgGaSe2
Authors: Zhu Shi‐Fu , Liu Jun , Zhao Bei‐Jun , Jiang Hong‐An , Li Zheng‐Hui
Published: January 2007

High quality AgGaSe2 single crystals with 20 mm in diameter and 55 mm in length have been grown by Bridgman technique. It is found that there is a second phase of Ag‐rich Ga2Se3 (or named AgGa7Se11) in the AgGaSe2 crystal. It is concluded by discussions with the DTA results and the phase diagram that single crystals grown from polycrystalline materials with stoichiometric composition must contain a second phase of Ag‐rich Ga2Se3. This result is helpful for the heat treatment, in which what and how much is added and what temperature is chosen for the heat treatment, are very important.
A New Molecular Crystal: Urea Tartrate
Authors: Fanqing Meng , Mengkai Lü , Hong Zeng
Published: January 2007

Urea tartrate, CO(NH2)2(+)C4H6O6 (hereafter abbraviated as UT) is reported for the first time. Large Single Crystals have been grown by the cooling method from aqueous solution. Some of its physical properties have been measured. The second harmonic generation of powder specimens is about three times larger than that of KH2PO4.
X‐Ray Study of the Structure and Thermal Properties of Ba1–xKxBiO3 at Different Temperatures
Authors: Barilo S. N. , Olekhnovich N. M. , Orlova N. S. , Pushkarev A. V. , Salak A. N. , Shiryaev S. V.
Published: January 2007

The crystal structure as well as the temperature and composition dependences of the lattice parameters, the thermal expansion coefficients in the high‐temperature superconducting Ba1–xBiO3 system were determined by an X‐ray powder diffraction method at temperatures between 80 and 650 K. The character of variation of intensity, profiles, and line widths of the diffraction lines for different perovskite structures as a function of the content x and temperatures was found. The correlation between the behaviour of the thermal expansion coefficients and potassium content was revealed at different temperatures. It is shown that the thermal expansion coefficients vary inversely with rising x at any temperature in the range from 80 to 400 K.
Discontinuous Dielectric Reorientation in the Smectic C Phase of 3‐n‐Heptyl‐6‐[4‐n‐hexyloxyphenyl]‐1,2,4,5‐tetrazine
Authors: Camara K. , Pelzl G. , Schiller P.
Published: January 2007

In the nematic phase and smectic C phase of 3‐n‐Heptyl‐6‐[4‐n‐hexyloxyphenyl]‐ 1,2,4,5‐tetrazine the Freedericksz transition was studied. In both phases the threshold voltage and the switching times were measured. In the smectic C phase two thresholds were observed which can be explained by an asymmetric chevron structure.
Long‐term Crystal Growth under Microgravity during the EURECA‐1 Mission (II) THM Growth of Sulphur‐doped InP
Authors: Danilewsky A. N. , Meinhardt J. , Benz K. W.
Published: January 2007

Long‐term crystal growth experiments were successfully performed under microgravity conditions during the first flight of the unmanned EURECA‐1 mission in the automatic mirror furnace (AMF). Two crystals of sulphur‐doped InP with [001] and [111] orientation respectively were grown from indium solution by the travelling heater method (THM). The absence of time dependent buoyancy‐driven convection is documented by the lack of type I striations in the space‐grown crystals. The sulphur concentration is measured by spatially resolved photoluminescence. As expected, the macrosegregation can be described by a pure diffusion‐controlled model which is in good agreement with the findings from the first German spacelab mission D1. Compared to the earth‐grown reference samples, both of the space‐grown InP crystals show strong disturbances such as inclusions and type II striations. The morphological instabilities are similar to growth disturbances already known from the space‐grown MD‐ELI‐01 from the D1 mission.
X‐ray Photoelectron Spectroscopic Studies of Sellinite and Eulytite BGO and BSO Crystals
Authors: Gopalakrishnan R. , Gopinath C. S. , Ramasamy P.
Published: January 2007

Single crystals of Bi12GeO20, Bi12SiO20, Bi4Ge3O12, and Bi4Si3O12 are grown by Floating zone and Czochralski techniques. The X‐ray photoelectron spectroscopic (XPS) studies have been carried out on BSO and BGO crystals. XPS is employed to characterise the surface quality and bulk nature of the crystals. The surface contamination on both types of crystals are identified. In addition to the contamination, some amount of Bi atoms are observed with Bi ions on sellinite. It is demonstrated that the eulytite crystals are chemically more robust to degradation than the sellinite crystals. The predominant covalent and ionic character of Bi4Ge3O12 and Bi4Si3O12 respectively is explained from their oxygen 1s core level spectra.
Effect of Supersaturation and Temperature on the Growth Morphology of Ammonium Oxalate Monohydrate Crystals Obtained from Aqueous Solutions
Authors: Sangwal K. , Zdyb A. , Chocyk D. , Mielniczek‐Brzóska E.
Published: January 2007

The experimental results of a study of the effect of supersaturation and temperature on the growth morphology of ammonium oxalate monohydrate [(NH4)2C2O4H2O; AO] single crystals obtained from aqueous solutions at 30 and 40 °C and supersaturation up to 9% are presented. The observations are analysed in terms of theoretical morphology, growth models and attachment energy for growth units in steps of growing faces.
Tetrabutylphosphonium Cation as Template in the Kinetics of Crystallisation of ZSM‐5
Authors: Lingappan N. , Krishnasamy V.
Published: January 2007

Zeolite ZSM‐5 was synthesised using ethyl silicate ester 40 and sodium aluminate so as to get the gel mix with SiO4/Al2O3 = 90 employing TBPCl and TPABr templates separately (for comparison) at temperatures 423 K, 448 K, and 473 K. Nucleation and crystallisation processes were kinetically analysed. Activation energies for nucelation and crystallisation and the geometric factors have been evaluated. Correlations were found between the kinetic characteristics and the habits of the crystals formed. The study of the composition and morphology of the intermediates, with the support of SEM pictures, reveal the different mechanisms operating in the templating action of TBPCl and TPABr molecules.
Crystal Structure of an Adduct of Sarcosine with Sulfuric Acid (at 140 K)
Authors: Mostad A. , Natarajan S.
Published: January 2007

The crystal structure of an adduct of sarcosine with sulfuric acid, (C3NO2H8)2SO2−4, has been determined at low temperature (140 K). The crystals are triclinic, space group = P1 with the unit cell dimensions, a= 7.623(1) Å, b = 11.538(2) Å, c = 14.214(2) Å, α = 71.46(2)°, β = 74.36(2)°, γ = 86.46(2)°. Based on 4924 reflections with intensities larger than 3σ(I), the structure was refined to a conventional R factor of 0.038 giving e.s.d.s. in bond lengths and angles of 0.003 Å and 0.2°, respectively. There are two formula units in the asymmetric unit and both sulfate ions exist in two disordered orientations. The sulfate group 1 occupies the two orientations in the proportion 0.82/0.18 and sulfate group 2 in proportion 0.69/0.31. Both Orientations of the sulfate groups satisfy the hydrogen bonding scheme equally well.

There is also a pseudo‐symmetry element within the asymmetric unit as one half of this unit is transformcd into the other by a translation of approximately one half along the b‐ and c‐axes. Thus, sarcosine molecule 1 is translated to sarcosine IV and sarcosine II to III. In the same manner, the sulfate group I in its main orientation is translated to the sulfate group 2 in its alternative orientation and vice versa.
Photorefraction Dependent on Composition in LiNbO3 Crystals with and without MgO Doping
Authors: Kan S. , Sakamoto M. , Okano Y. , Yoon D. H. , Fukuda T. , Oguri O. , Sasaki T.
Published: January 2007

The photorefraction in LiNbO3 single crystals dependent on the melt composition with and without MgO doping was investigated. It was found that 1 mol% MgO‐doped crystal with nearly stoichiometric composition has a strong photorefraction resistance. compared with a congruent composition. In an undoped crystal, the photorefraction was shown to be pronounced as incrcasing Li content of a melt from 48.6 to 58 mol% Li2O. These results were discussed from a viewpoint of the relationship between the photoconductivity and the concentration of cation‐site vacancies or Nb on Li‐site.
Photoacoustic Spectra of Complexes of Erbium (III) with Glycine and Alanine
Authors: Qingde Su , Yuetao Yang , Guiwen Zhao
Published: January 2007

The crystals of the complexes Er(Gly)3Cl3. 3 H2O and Er(Ala)3Cl3. 3 H2O were synthesized and the photoacoustic (PA) spectra in the 300–800 nm region are reported. Their PA and absorption spectra are interpreted. The PA relative intensities represented by intensity branching vectors and the perturbation of ligands on the energy levels of Er3+ ion are discussed. The fluorescene properties of Er(Gly)3Cl3. 3 H2O and the relaxation process models were also studied based on the PA and absorption spectra.
The Effective Temperature of Surfaces of Liquid Metals and Some Non‐Metals
Authors: Vlasov A. D.
Published: January 2007

An estimation of decrease of atomic bond energy by raising temperature for surfaces of liquid metals and some non‐metals had been made. The calculation values of the derivative dusdub where us and ub, are bond energy of atoms in surface and bulk of a liquid, are significantly above 1 and in limits from 2 to 10. It was supposed that this results from anomalously intensive thermal expansion of surface layers of liquids – the effect which is well known for crystal surfaces. This expansion was explained by the effective temperature of these surfaces which, thus, was found to be by several times above those for bulk of liquids.
Modelling of Growth Rate for MSMPR Crystallizer Data
Authors: Mydlarz Jerzy
Published: January 2007

One of the most important applications of the population balance approach to MSMPR crystallizer modelling is the recovery of crystal nucleation and growth rates data from steady‐state crystal size distributions (RANDOLPH, LARSON). A large number of studies have confirmed that both size‐dependent (growth rate is a function of crystal size) and growth rate dispersion (crystals of the same size do not have the same growth rate), causes nonlinearities which limit the usefulness of the RANDOLPH and LARSON approach.

A discussion of modelling of crystal growth kinetics for simulated and real MSMPR crystallizer data is presented. In the former case, both linear and non‐linear log population density distributions are used. The modelling of growth kinetics is done twice – once assuming that growth rate dispersion is a source of curvature in the log population density vs size data plot and, again when this curvature is caused by size‐dependent growth. Calculations clearly indicate that even for crystallizing systems which follow the McCabe's δL law, both growth rate dispersion and size‐dependent growth models lead to proper estimation of growth kinetics. When log population density vs size data plots exhibit curvature, however, use of the size‐dependent growth rate approach gives more reliable growth kinetics across a broad crystal size range than those obtained from modelling of growth kinetics by growth rate dispersion.
On a Hypothesis on the Molecule Vacancies in PbTe
Authors: Moldovanova M. , Assenov R.
Published: January 2007

The temperature dependence of the current carriers mobility in SnTe(I) and PbTe (I) synthesized in presence of SnI2 or PbI2 respectively was studied. An experimental formula was established, showing that current carriers scattering in SnTe(I) is due to vacancies at constant Hall coefficient.

For PbTe (I) crystallized from tellurium solution by traveling heater method the mobility is high (between 2.104 and 4.104 cm2/Vs) and the Hall coefficient is constant within the interval 77 K–450 K. Only within 77 K–160 K interval the current carriers scattering is due to vacancies.

A hypothesis is proposed based on the presence of molecular vacancies (VpbTe). These vacancies do not change electron gas concentration but do change the carriers mobility. Specimens with a negligibly low lead atoms vacancies Concentration were investigated. An empirical expression is established which shows that their mobility depends on molecular vacancies concentration and explains observed weak temperature influence upon carriers mobility. These results are obtained only from Hall coefficient and electric conductivity measurements within the 77 K–160 K temperature interval.
Validity of the Lattice‐Parameter Vegard‐Rule in Cd1‐xZnxTe Solid Solutions
Authors: Schenk M. , Hähnert I. , Duong L. T. H. , Niebsch H.‐H.
Published: January 2007

Cd1‐xZnxTc crystals of different composition (0 ⩽ x ⩽ 1) were grown by the vertical Bridgman method and by synthesis in Te excess. After careful surface preparation of crystal slices, their Zn:Cd ratios were ascertained by wavelength‐dispersive X‐ray spectroscopy (WDXS), and the lattice parameters of the same slice regions were measured by X‐ray diffractometry. The Vegard rule concerning the linear lattice‐parameter dependence on composition is – in contrast with earlier literature data – exactly valid within the limits of error (Δx ⩽ ±0.01 and Δa/a ⩽ 3.7. 10−4) and follows the equation a(x) = (0.64822 ‐ 0.03792x) nm. After annealing some slices at different temperatures and controlled partial pressure conditions in ordcr to find possible phase separations or cation ordering effects, neither the lattice parameters were changed nor additonal interferences were found. A published occurrence of a rhomhohedral phase could not be confirmed by means of powder diffraction analysis. The results are discussed in relation to own electron diffraction investigations and to EXAFS literature data.
Relation of the Hydrostatic Electrostrictive Coefficient of Cubic Dielectrics with other Material Constants
Authors: Kloos G.
Published: January 2007

A simple relation is derived that links the hydrostatic coefficient of quadratic electrostriction with the volume compressibility and an expression involving the dielectric constant. The first part of the derivation is mainly macroscopic and applicable to dielectrics with cubic symmetry. Making use of the Born‐Mayer potential, an expression of the derivative of the ionic polarizability with respect to volume is given in the second part. A negative sign of the hydrostatic coefficient is predicted for typical alkali halides. This result is in agreement with recent experimental findings reported in the literature, if the observed values are corrected for the influence of electrostatic stresses in an alternative way.
A Simple Model for Evaluation of Electronic Polarizabilities of Chalcopyrity Semiconductors
Authors: Reddy R. R. , Ahammed Y. Nazeer , Reddy C. V. K. , Buddhudu S.
Published: January 2007

Simple correlations between the energy gap, optical electronegativity and the refractive index are given for some ternary chalcopyrite semiconductors. Refractive indices and electronic polarizabilities are evaluated. Results are in good agreement (±5.3%) with the experimental values, better than those of the valus (±19.5−28%) using bond charge model and plasma frequency formalism.
Theoretical Study of Ge Implanted Silicon Subjected to Pulsed Excimer (XeCl) Laser Radiation
Authors: Klinger D. , Auleytner J. , Z̊ymierska D.
Published: January 2007

A theoretical study of time‐dependent temperature profiles in Ge implanted silicon crystal subjected to excimer pulsed laser irradiation is presented. The minimum depth of the annealing process is calculated with assumed laser beam parameters.
Study on the Morphological Change of Growing Ag Crystallites by in‐situ SEM Observation
Authors: Horii Akira , Kawanowa Hitoshi , Kamei Masayuki , Yumoto Hisami , Gotoh Yoshihiko , Gonda Takehiko
Published: January 2007

The morphology of the initial growth stage of Ag thin films on Mo(110) substrate was investigated in‐situ by the scanning electron microscope (SEM). A great majority of the Ag crystallites showed a truncated Wulff's equilibrium shape of the face‐centered‐cubic (fcc) structure with epitaxial orientation [10]Ag//[11]Mo, (111)Ag//(110)Mo with the substrate temperature of 400 °C. In‐situ SEM observation during the growth revealed two kinds of particular morphological change of Ag crystallites, namely (1) rotation of an Ag crystallite and (2) reformation of the crystal faces of the Ag crystallite. However, a small number of Ag crystal particles showed Wulff‐polyhedron truncated by the (100) plane parallel to the substrate surface (oriented to the 〈100〉 axis normal to the substrate surface).
The as‐Grown SiC (0001) Surface as Observed by Reflection Electron Microscopy
Authors: Marek T. , Heindl J. , Strunk H. P. , Eckstein R. , Müller St. G. , Hofmann D.
Published: January 2007

Reflection electron microscopy (REM), capable of imaging surfaces in high resolution, reveals that the risers and treads in the terrace growth surfaces of vapor grown SiC(0001) bulk crystals are characterized on a microscopic scale by growth steps. At the risers microscopic growth occurs by the ‘step flow mode’. At the treads, growth occurs by island formation and by operation of growth spirals.
Simulation of the Fluidized‐bed Crystallizers (II) Productivity Related Aspects
Authors: Belcu M. , Turtoi D.
Published: January 2007

The very intensive system self‐regulation renders the evacuated‐crystal size reduction a less efficient method for the productivity increase. The most promising possibilities seem to be:

Recirculation of some already‐grown crystals and their insertion as seeds on the crystallizer bottom;

The use of a supplementary crystallizer, with considerably reduced dimensions, in order to produce a seeds flux numerically equal to the flux of crystals evacuated as product

.
Electrical Conductivity in Polycrystalline Copper Oxide Thin Films
Authors: Roy B. N. , Wright T.
Published: January 2007

This study presents a preliminary investigation on the electrical properties and the electronic structure of the copper‐oxygen system. Thin films, prepared by high vacuum sputtering on glass and MgO substrates, were oxidised both at constant temperatures and by heating continuously from a low to a high temperature, and the variations in the resistance with oxidation were measured. The final oxide was found to be CuO. The room temperature resistance after oxidation is very much higher than that before oxidation, indicating a transition from metal to insulator. At oxidation temperatures below 600 K, the conductivity decreased gradually; a steeper decrease occurred at higher temperatures when an apparent semiconducting behaviour was observed in some cases. At temperatures above 600 K, the behaviour of the conductivity followed the form σ(T) = σ(0) + αTβ, which suggested weak localization or electron‐electron interaction.
XRD Line Broadening Studies on Mullite
Authors: Serrano F. J. , Bastida J. , Amigó J. M. , Sanz A.
Published: January 2007

An X‐ray diffraction microstructural study on 110, 220, 001 and 111 peaks has been performed on mullite in the temperature range of primary mullite formation in order to monitor nucleation and growth process. Considering the crystallinity of the starting kaolinites, a greater disorder of the kaolinite has been found to enhance the mullite formation. Isothermal growth is related to a decrease in the Al2O3 content of mullite.
Modification of Fluid Flow and Heat Transport in Vertical Bridgman Configurations by Rotating Magnetic Fields
Authors: Dold P. , Benz K. W.
Published: January 2007

Applying a rotating magnetic field to an electrically conducting liquid, a Lorentz force is induced which generates a melt rotation of a certain angular velocity. A cylindrical gallium melt (aspect ratio 2.5) has been used as a model liquid. The melt has been heated from the bottom (Ra = 106) or from the top (Ra = −106) and the resulting temperature fluctuations in the melt have been measured in dependence on the rotating field strength (Bmax = 30 mT). In the case of the unstable gradient 0.8 mT are sufficient to dominate the buoyancy driven convection and to reduce the amplitude of the buoyancy caused temperature oscillations for more than one order of magnitude. At the same time, the fluctuation frequency increases with the field strength. In the case of the stabilizing temperature gradient, low amplitude/high frequency temperature fluctuations are generated by the rotating magnetic field, indicating the transition to a time‐dependent flow. In both cases we see an increase of the convective heat transport for magnetic inductions higher than approximately 5 m T.

Applying the rotating magnetic field to the Bridgman growth of gallium doped germanium, the same behavior can be seen: Growing with a top‐seeded arrangement, the intensity of the dopant striations is decreased and their frequency is increased. Growing with a bottom‐seeded arrangement, the interface curvature changes from concave to convex and the flow becomes time‐dependent.
Axial temperature distribution in Silicon‐Germanium grown by the RF‐heated float zone technique
Authors: Schulz D. , Wollweber J. , Darowski N. , Schröder W.
Published: January 2007

Im Konzentrationsbereich von 0 bis 25 at% Germanium wurde das Segregationsverhalten von Sili‐zium‐Germanium‐Einkristallen gezüchtet mit Hilfe des HF‐beheizten tiegelfreien Zonenschmelzver‐fahrens untersucht. Vollstündig versetzungsfreie Kristalle mit bis zu 8 at% Germanium wurden gezüchtet. Störungen des einkristalline Wachstum waren im wesentlichen auf konstitutionelle Unterkühlung zurückzuführen. Mittels pyrometrischer Temperaturmessung wurde der Anstieg der axialen Temperaturverteilung ΔT/ΔZ in der Nähe der Wachstumsphasengrenze bestimmt und daraus die kritische Ziehgeschwindigkeit abgeleitet. Die Messungen zeigten, daß mit zunehmenden Germaniumgehalt der Temperaturgradient im Kristall größer wird.
Twinning due to Transformation from a more Favourable Energetic Transition Structure to a Higher Symmetrical Arrangement: Five‐radiated Intergrowth Crystals of Metals (III)
Authors: Krafczyk Susanne , Jacobi Hans , Follner Heinz
Published: January 2007

Parts I and II investigated twins that form when a more favourable energetic transition structure initially occurs which then, at a certain growth stage (presumably in the nm‐range), transform into a more symmetric structural arrangement. These transition structures, which could explain the transformation between the twin individuals, were found using lattice energy calculations on organic substances such as pentaerythrite, 1,2,4,5‐tetrabromobenzene, 3,5‐dimethylbenzoic acid, and maleic acid. The formation of a more favourable energetic but symmetrically lower transition structure is more likely. when lattice pseudosymmetries are present. Experimentally proving these transition structures is extremely difficult because of their low volume. It has nevertheless been possible to detect such a transition structure — around which crystal growth begins — in many metallic vapour‐deposit layers. Crystal growth begins around a core and then continues as a three‐dimensional periodically ordered cubic face‐centered structure, at which point twins form. In Part III, the attempt is made to confirm these processes with energy calculations.
On the Formation of Dislocation Hollow Cores on Cleaved {100} Faces of L‐Arginine Phosphate Monohydrate Single Crystals
Authors: Sangwal K. , Sanz F.
Published: January 2007

Thermodynamic conditions and energy considerations for the formation of hollow cores at the emergence points of monolayer cleavage steps associated with screw dislocations on the cleaved {100} faces of LAP single crystals are discussed. Analysis of the formation of hollow cores and the change of the curvature of steps in the vicinity of their origins reveals that dislocations responsible for the origin of hollow cores have stress fields due to trapped mother liquor of different supersaturations. The results also show that (1) the radius of a hollow core is inversely proportional to the one‐third power of the interface supersaturation while the volume of hollow corés increases exponentially with their radius, and that (2) the strain energy associated with a dislocation is responsible for the formation of an equilibrium hollow core of a particular depth at the origins of cleavage steps associated with dislocations.
The Structure and Unusual Optical Textures of Smectic C2 Phases of New Tail‐to‐Tail Twins
Authors: Weissflog W. , Richter S. , Dietzmann E. , Rise J. , Diele S. , Schiller P. , Pelzl G.
Published: January 2007

New tail‐to‐tail twins with alkyl or perfluorinated spacers were synthesized. The mesomorphic properties were studied by polarizing microscopy and X‐ray diffraction measurements. It was found that the smectic C phase is a Sc2 phase with alternating tilt and an intercalated structure. The alternating tilt gives rise to an unusual schlieren texture which exhibits not only singularities with the strength s = ±1 but also those with s = ±1/2 and s = ±3/2.
Crystal and Molecular Structure of 1‐Ethyl‐3‐[tris(trimethylsiloxanyl)silyl]pyrrolinium Hydrochloride
Authors: Rudert R. , Schmaucks G.
Published: January 2007

The crystal and molecular structure of 1‐Ethyl‐3[tris(trimethylsiloxyl)silyl]pyrrolinium hydro‐chloride (C15H38N+O3Si4 · C1−) has been determined by direct methods. The title compound crystallizes in the monoclinic space group C2/c with a = 20.640(3), b = 19.494(2), c = 27.34(3) Å, β = 90.60(4)°, V = 11000(13) Å3, Z = 16, Dx = 1.034 Mg m−3. There are two molecules with different conformations in the crystal. The pyrroline rings are non‐planar.‐The SiOSi angles range from 149(1)° to 163(1)°. Two of the SiMe3 groups are disordered. All molecules are connected by C1− – N+ contacts and C1− ‐ HN+ hydrogen bonds to form double chains.
The Crystal and Molecular Structure of 1‐Allyl‐5‐benzoyl‐4‐phenylpyrimidine‐2‐one hemihydrate
Authors: Öztürk S. , Akkurt M. , Hökelek T. , Yildirim İ.
Published: January 2007

The crystal structure of C20H16N2O2. 0.5 H2O has been determined from three dimensional X‐ray diffraction data. The crystals are monoclinic, space group C 2/c, with a = 24.491(3) Å, b =10.241(2) Å, c = 16.643(2) Å, β =126.63(1)°, V = 3350.0(9) Å3, Dcalc = 1.290 g. cm−3, Z = 8. The structure was solved by direct methods and refined by least‐squares methods to a final R = 0.0625 for 1358 observed unique reflections (F2 ⩾ 2σ(F2)].
Some Morphological Peculiarities of Lysozyme Crystals
Authors: Dimitrova S. , Tsekova D. , Nanev N.
Published: January 2007

Hen‐egg‐white lysozyme (HEWL) crystals does not differ from small molecule crystals in respect to diffusion limited growth but differ substantially as far as lattice bound strength is concerned.
The Electrical Degradation and Coloration in Iron Doped KTa1‐xNbxO3 Single Crystals
Authors: Guan Q. , Yin X. , Wang J. , Wei J. , Liu Y.
Published: January 2007

The electrical degradation and coloration experiments were investigated in Fe‐doped KTa1‐xNbxO3 crystals. The leakage currents of the crystals increase when dc voltages were applied, and a dark region moved from the anode to the cathode. Reversing the electrodes can lead to the dark region move back. The oxygen vacancies and color center defects are considered to play roles in the process.
Peculiarities of the B8‐Solid Solution Formation in Ni(Sb,Sn) and Co(Sb,Sn) Systems Studied by Mossbauer Effect Method
Authors: Vasilev E. A. , Tkachenko T. M.
Published: January 2007

Quadrupole splitting and effective characteristic temperatures of 119Sn in Ni(Sb,Sn) and Co(Sb,Sn) solid solutions with B8‐type structure have been studied by Mossbauer Effect method. The electric field gradient at metalloid atoms was estimated in point charge model for different variants of local environment.

On the basis of the comparison between experimental Quadruple Splitting values and estimated Electric Field Gradient ones it was concluded that MeII‐Sn pairs occur more often than MeII‐Sb when the amount of transition metal in ditrigonal‐dibipyramidal positions is less than 0.10.
Fibrillation potentials following spinal cord injury: Improvement with neurotrophins and exercise
Authors: Burns Anthony S. , Boyce Vanessa S. , Tessler Alan , Lemay Michel A.
Published: January 2007

Fibrillation potentials and positive sharp waves (spontaneous potentials) are the electrophysiological hallmark of denervated skeletal muscle, and their detection by intramuscular electromyography (EMG) is the clinical gold standard for diagnosing denervated skeletal muscle. Surprisingly, spontaneous potentials have been described following human and experimental spinal cord injury (SCI) in muscles innervated by spinal cord segments distal to the level of direct spinal injury. To determine whether electrophysiological abnormalities are improved by two therapeutic interventions for experimental SCI, neurotrophic factors and exercise training, we studied four representative hindlimb muscles in adult domestic short‐hair cats following complete transection of the spinal cord at T11–T12. In untreated cats, electrophysiological abnormalities persisted unchanged for 12 weeks postinjury, the longest duration studied. In contrast, fibrillations and positive sharp waves largely resolved in animals that underwent weight‐supported treadmill training or received grafts containing fibroblasts genetically modified to express brain‐derived neurotrophic factor and neurotrophin‐3. These findings suggest that neurotrophins and activity play an important role in the poorly understood phenomenon of fibrillations distal to SCI. Muscle Nerve, 2007
On the optimality of the observability inequalities for parabolic and hyperbolic systems with potentials
Authors: Duyckaerts Thomas , Zhang Xu , Zuazua Enrique
Published: January 2007

In this paper we prove the optimality of the observability inequality for parabolic systems with potentials in even space dimensionsn⩾2. This inequality (derived by E. Fernández-Cara and the third author in the context of the scalar heat equation with potentials in any space dimension) asserts, roughly, that for small time, the total energy of solutions can be estimated from above in terms of the energy localized in a subdomain with an observability constant of the order of\mathrm{\exp }(C\|a\|_{\infty }^{2/ 3}),abeing the potential involved in the system. The problem of the optimality of the observability inequality remains open for scalar equations.

The optimality is a consequence of a construction due to V.Z. Meshkov of a complex-valued bounded potentialq = q(x)in\mathbb{R}^{2}and a nontrivial solutionuof\mathrm{\Delta }u = q(x)uwith the decay property|u(x)|⩽\mathrm{\exp }(−|x|^{4/ 3}). Meshkov's construction may be generalized to any even dimension. We give an extension to odd dimensions, which gives a sharp decay rate up to some logarithmic factor and yields a weaker optimality result in odd space-dimensions.

We address the same problem for the wave equation. In this case it is well known that, in space-dimensionn = 1, observability holds with a sharp constant of the order of\mathrm{\exp }(C\|a\|_{\infty }^{1/ 2}). For systems in even space dimensionsn⩾2we prove that the best constant one can expect is of the order of\mathrm{\exp }(C\|a\|_{\infty }^{2/ 3})for anyT > 0and any observation domain. Based on Carleman inequalities, we show that the positive counterpart is also true whenTis large enough and the observation is made in a neighborhood of the boundary. As in the context of the heat equation, the optimality of this estimate is open for scalar equations.

We address similar questions, for both equations, with potentials involving the first order term. We also discuss issues related with the impact of the growth rates of the nonlinearities on the controllability of semilinear equations. Some other open problems are raised.
Neural Network Analyses of Infrared Spectra for Classifying Cell Wall Architectures
Authors: McCann Maureen C. , Defernez Marianne , Urbanowicz Breeanna R. , Tewari Jagdish C. , Langewisch Tiffany , Olek Anna , Wells Brian , Wilson Reginald H. , Carpita Nicholas C.
Published: January 2007

About 10% of plant genomes are devoted to cell wall biogenesis. Our goal is to establish methodologies that identify and classify cell wall phenotypes of mutants on a genome-wide scale. Toward this goal, we have used a model system, the elongating maize (Zea mays) coleoptile system, in which cell wall changes are well characterized, to develop a paradigm for classification of a comprehensive range of cell wall architectures altered during development, by environmental perturbation, or by mutation. Dynamic changes in cell walls of etiolated maize coleoptiles, sampled at one-half-d intervals of growth, were analyzed by chemical and enzymatic assays and Fourier transform infrared spectroscopy. The primary walls of grasses are composed of cellulose microfibrils, glucuronoarabinoxylans, and mixed-linkage (1 → 3),(1 → 4)-β-d-glucans, together with smaller amounts of glucomannans, xyloglucans, pectins, and a network of polyphenolic substances. During coleoptile development, changes in cell wall composition included a transient appearance of the (1 → 3),(1 → 4)-β-d-glucans, a gradual loss of arabinose from glucuronoarabinoxylans, and an increase in the relative proportion of cellulose. Infrared spectra reflected these dynamic changes in composition. Although infrared spectra of walls from embryonic, elongating, and senescent coleoptiles were broadly discriminated from each other by exploratory principal components analysis, neural network algorithms (both genetic and Kohonen) could correctly classify infrared spectra from cell walls harvested from individuals differing at one-half-d interval of growth. We tested the predictive capabilities of the model with a maize inbred line, Wisconsin 22, and found it to be accurate in classifying cell walls representing developmental stage. The ability of artificial neural networks to classify infrared spectra from cell walls provides a means to identify many possible classes of cell wall phenotypes. This classification can be broadened to phenotypes resulting from mutations in genes encoding proteins for which a function is yet to be described.
Effect of temperature and ration size on carbon and nitrogen stable isotope trophic fractionation
Authors: BARNES CAROLYN , SWEETING CHRISTOPHER J. , JENNINGS SIMON , BARRY JON T. , POLUNIN NICHOLAS V. C.
Published: January 2007

Stable isotope data are widely used to track the origins and transformations of materials in food webs. Reliable interpretation of these data requires knowledge of the factors influencing isotopic fractionation between diet and consumer. For practical reasons, isotopic fractionation is often assumed to be constant but, in reality, a range of factors may affect fractionation.

To investigate effects of temperature and feeding rate on fractionation of carbon and nitrogen stable isotopes in a marine predator, we reared European sea bass Dicentrarchus labrax on identical diets at 11 and 16 °C on three ration levels for 600 days.

Nitrogen trophic fractionation (Δδ15N) was affected by temperature. Bass Δδ15N was 4·41‰ at 11 °C and 3·78‰ at 16 °C.

Carbon fractionation (Δδ13C) was also affected by temperature. Bass Δδ13C was 1·18‰ at 11 °C and 1·64‰ at 16 °C. The higher lipid content in the tissues of bass reared at cooler temperatures accounted for the temperature effect on Δδ13C. When Δδ13C was determined using mathematically defatted values, there was a direct effect of ration size and Δδ13C was 2·51, 2·39 and 2·31‰ for high, medium and low rations, respectively.

Reported Δδ15N for all treatments exceeded the mean of 3·4‰ widely used in ecological studies of fish populations and communities. This would confound the interpretation of δ15N as an indicator of trophic level when comparing populations that are exposed to different temperatures.

The Δδ13C of 0–1‰ commonly applied in food web studies did not hold under any of the temperature or feeding regimes considered and a value of 2‰ would be more appropriate.
IT for niche companies: is an ERP system the solution?
Authors: Olsen Kai A , Sætre Per
Published: January 2007

Abstract.  Niche companies are per definition idiosyncratic. They survive in a competitive world by mastering a small market niche, providing what their customers need. This often requires a flexible organization, and the ability to customize products. To be more efficient, many of these companies rely on extensive use of IT, often by installing general Enterprise Resource Planning (ERP) systems. These systems have grown from isolated systems that handle planning based on incoming orders and the component structure of the various products, to systems with ambitions to embrace the total functioning of the company including vendor and customer relation management. In this paper, we present four case studies. One company is a part of a large enterprise, but performs niche functions within this enterprise. The other three are small‐ or medium‐sized enterprises. Each of these performs in small niche markets. Common to all is the fact that they encounter problems with the utilization of their ERP systems. The major problem seems to be that the ERP system has an inherent business model that may not conform to the needs of the company. Without a good understanding of the underlying models and the constraints under which the fundamental algorithms operate, it is difficult to use these systems correctly. Even excellent systems may give bad results if they are applied to situations where they are not suited. Further, the monolithic structure of an ERP system, with a rather complicated parameter setting, is often insufficient to mould the system to the needs of a niche company. We discuss these problems based on our four case studies, and offer alternative approaches that may be considered.
Improving paediatric nurses' knowledge and attitudes in childhood fever management
Authors: Edwards Helen , Walsh Anne , Courtney Mary , Monaghan Sarah , Wilson Jenny , Young Jeanine
Published: January 2007

Title. Improving paediatric nurses' knowledge and attitudes in childhood fever management

Aim.  This paper reports an evaluation of the effectiveness of a peer education programme in developing paediatric nurses’ evidence‐based knowledge and attitudes towards fever management and the sustainability of these changes.

Background.  In general, paediatric nurses’ fever management knowledge seems to be mediocre. They believe fever to be harmful, causing febrile convulsions and brain damage. Antipyretics are administered to prevent febrile convulsions and alternate antipyretics are given when temperatures are not reduced.

Method.  A quasi‐experiment was conducted from August 2002 to March 2003. An experimental group of Registered Nurses received the peer education programme and peer support and education were promoted for those unable to attend the sessions. A control group continued its normal practices. Seventy‐seven nurses were eligible to attend the programme; 74·0% attended at least one session, 52% two or more. Questionnaire data were collected 1 month before and 1 and 4 months after the peer education programme from 56·3% to 77·8% of eligible experimental and 40·9% to 51·6% of eligible control group nurses.

Findings.  Interaction effects between group and time were found in overall knowledge (P = 0·01), specifically knowledge of the physiology of fever (P = 0·001), and attitudes towards evidence‐based fever management (P = 0·05). In addition, experimental group nurses demonstrated statistically significantly more knowledge of general fever management principles at 4 months after the intervention than control group nurses (P = 0·01), and compared with their own knowledge at baseline (P < 0·001).

Conclusions.  Educational programmes targeting practice change must be theoretically based and target knowledge, attitudes and barriers to change. The programme tested here, which incorporated peer education and support and facilitated group change, is adaptable to other practices, groups and settings.
What degree of work overload is likely to cause increased sickness absenteeism among nurses? Evidence from the RAFAELA patient classification system
Authors: Rauhala Auvo , Kivimäki Mika , Fagerström Lisbeth , Elovainio Marko , Virtanen Marianna , Vahtera Jussi , Rainio Anna‐Kaisa , Ojaniemi Kati , Kinnunen Juha
Published: January 2007

Title. What degree of work overload is likely to cause increased sickness absenteeism among nurses? Evidence from the RAFAELA patient classification system

Aim.  This paper reports a study examining whether nurses’ work overload is associated with increased sick leave and quantifying the loss of working days from work overload.

Background.  The RAFAELA patient classification system indicates nursing care intensity in relation to an optimum and is one of the few validated monitoring instruments of patient‐associated workload among nurses. However, it is not clear whether work overload is a risk factor for increased sickness absenteeism, an important occupational problem in health care.

Method.  An observational cohort study was carried out with 877 nurses, 31 wards and five Finnish hospitals. Patient‐associated workload scores from the RAFAELA system were based on a 6‐month monitoring period in 2004. Records of 12‐month self certified (1–3 days) and medically certified (>3 days) periods of sick leave in the same year were obtained from employers’ registers.

Findings.  The mean workload was 9% (sd = 8%) above the optimum. There was a linear trend between increasing workload and increasing sick leave (P ≤ 0·006). Among nurses with workload ≥30% above the optimum the rate of self certified periods of sick leave was 1·44 (95% CI 1·13–1·83) times higher than among those with an optimum workload. The corresponding rate ratio for medically certified sick leave was 1·49 (1·10–2·03). These excess rates of sickness absence resulted in 12 extra sick leave days per person‐year.

Conclusion.  Measuring nurses’ workload may be an important part of strategic human resource management of nurses to reduce sick leave among nurses.