bluuebunny/crossref_metadata_2025 huggingface dataset:
Anisotropy of Electrical Resistivity and Hole Mobility in InTe Single Crystals
Authors: Parlak M. , Erçelebi Ç. , Günal I. , Özkan H. , Gasanly N. M.
Published: January 2007

The temperature dependences of the electrical resistivity and Hall mobility of p‐type InTe chain single crystals in parallel and perpendicular directions to c‐axis have been investigated in the temperature range of 28–260 K. The high anisotropy between ∂‖ and ∂⟂ which depends on temperature is attributed to high concentration of stacking faults due to weak interchain bonding. The mobility parallel to c‐axis was found to vary with temperature asμ α Tn where n = ‐0.6 due to hole scattering on polar optical phonons. The mobility perpendicular to c‐axis above 140 K increases with temperature exponentially with an activation energy of 0.03 eV which is attributed to the hopping mechanism due to the barriers between the chains.
Crystal Structure Investigation of 2‐Pheny limidazo [f]1,10‐phenanthroline
Authors: Wu Jian‐Zhong , Wang Lei , Yang Guang , Ji Liang‐Nian , Koutsodimou Aglaia , Katsaros Nikos
Published: January 2007

The crystal structure of the title compound (PIP) has been determined by single crystal X‐ray diffraction methods. C19H12N4. C2H5OH crystallizes in the monoclinic space group P21/n with a = 11.4414(8), b = 12.6052(9), c = 12.4627(8) Å, β = 100.345(2)°, Z = 4, V = 1768.17 Å3, Dcal = 1.286 Mg. m−3, μ (MoKα) = 0.80 cm‐1, F(000) = 720. The structure was solved by the direct methods and refined by full‐matrix least‐squares method to a final R = 0.0337 and Rw = 0.0332 for 2306 reflections with F0 > 4σ(F0). The phenl ring and the imidazo[f]1,10‐phenanthroline moiety are coplanar in the crystal. The packing of the molecules involves hydrogen bonded association of the hydroxyl group of ethanol both with the NH of the imidazole moiety of one PIP and one nitrogen atom of the phenanthroline moiety of another PIP.
Properties of Doped GaSb Single Crystals Grown by the Czochralski Method
Authors: Šestáková V. , Štěpánek B. , Šesták J.
Published: January 2007

The specific electrical properties and average dislocation density of GaSb crystals are shown and discussed regarding various elements presented as dopant. The single crystals were grown by the Czochralski method without encapsulant in a flowing atmosphere of molecular hydrogen, on the one hand, and of atomic hydrogen, on the other hand. The results are summarized in the Table II.
Monte Carlo Simulation of Crystal Growth
Authors: Nývlt Jaroslav
Published: January 2007

A simple Monte Carlo simulation has been used for the study of crystal growth from solutions. The effect of concentration of the solution, its supersaturation, agitation and presence of admixtures has been investigated. The results of simulation qualitatively correspond to the phenomenon observed experimentally.
Simulation of the Fluidized‐bed Crystallizers (I) Influence of Parameters
Authors: Belcu M. , Turtoi D.
Published: January 2007

A computer programme for the simulation of an ammonium sulphate producing fluidized‐bed crystallizer was elaborated. The results pointed out the strong influence of the equipment geometry and also a very intensive self‐regulation of the system.
Entropy Contribution and Stacking Fault Energy of CdI2 Polytypes
Authors: Khan Momeen, M. Y.
Published: January 2007

The CdI2 material when is grown by using the different techniques under a same growth conditions shows a rich character in crystallization with several phases (polytypes). The exhibition of these polytypes has been explained here by following the Gibb's phase rule. Therefore, an effort has also been made to calculate the stacking fault energy of these polytypes.
Operating Limits for Stable Growth of Silicon Fibers with Diameter Less Than 150 μm by Modified μ‐PD Method
Authors: Epelbaum Boris M. , Shimamura Kiyoshi , Uda Satoshi , Kon Junichi , Fukuda Tsuguo
Published: January 2007

The μ‐PD method originally developed for oxide crystals has been modified and applied for filamentary silicon crystal growth. Our main modification of μ‐PD method is concerned with an arrangement of melt permeable feeder which is inserted into the nozzle. The feeder finishes by a sharp tip the diameter of which (is almost the same as that of the desired semiconductor fiber, i.e., less than 150 μm. Silicon fibers were grown from the small liquid pool at the end of the feeder. Three types of crucible‐die arrangement were designed and tested. The best results were obtained with the help of inclined insert made of graphite fibers because of its ability to quench oscillations and longer operation life. Fiber crystals, 100 μm in diameter and 70 mm in length, have been grown successfully. Small meniscus stability, operating limits of μ‐PD method and silicon carbide formation during the growth process are discussed.
Meyer's hardness law and its relation to other measures of ball hardness tests
Authors: Berg Gunnar , Grau Peter
Published: January 2007

The force dependence of the ball indentation hardness can be described in many cases by MEYER's hardness law. The characteristic material parameters are the MEYER constant K and the MEYER exponent n. But often other simple measures of hardness are used for technical applications. Examples are the difference of hardness for two different loads, which gives a good view of the hardening capability of the material, and the BRINELL hardness.

It is shown that empirical found relations between the mentioned measures of hardness and the MEYER parameters are strong consequences of the validity of MEYER'S law. In special ranges of the values of the material parameters these empirical relations are linear ones. As a result of the theoretical considerations one must recommend to use the theoretical relations to fit the experimental values, because only in this case all physical conditions are fulfiled automatically.
Modification of the CuInSe2 Crystal Surface during Polishing and Annealing
Authors: Yakushev M. V. , Neumann H. , Tomlinson R. D.
Published: January 2007

The RBS/channelling technique was used to study the near‐surface damage characteristics of CuInSe2 crystals after polishing with 0.05 μm grade alumina and subsequent annealing up to temperatures of 600 °C. A comparative RUMP and damage density depth profile analysis of the channelling spectra revealed a polish‐induced near‐surface disordered layer with a thickness close to 40 nm. Up to annealing temperatures of about 400 °C a gradual overall decrease of the defect density in the damaged layer is observed without detectable changes in its thickness. An indium‐rich surface layer is formed after vacuum annealing at 600 °C.
Certification of Reference Material with Special Emphasis on Porous Solids
Authors: Meyer K. , Klobes P. , Röhl‐Kuhn B.
Published: January 2007

Certified reference materials (CRMs) are very important for the reliability of the results of chemical analyses and, at the same time, constitute the basis of comparability of analytical data. The development of a new type of CRMs is demonstrated using the example of porous and finely dispersed solids having specific surface area, specific pore volume, pore volume distribution, and mean pore radius as their characteristic values.

Many of the properties of reference materials to be certified, such as their elemental content, are established by means of measurement procedures relying on different and independent principles of measurement. With porous or finely dispersed solids, however, the characteristic values referring to pores strongly depend on the size of the probe molecules used, a fact which is due to the fractal character of these substrates. This is particularly true for the specific surface area or the pore volume. As a result, when applying the method of gas adsorption, the certified values refer to a specific probe gas, e.g. to nitrogen. The use of other gases yields different numerical values for the characteristic values to be certified.

Generally, the pore system of a solid contains pores of irregular shape. Therefore, depending on the presence of e.g. cylinder or slit pores, different evaluation models must be applied. For the verification of model calculation of microporous solids, zeolites with their crystallographically defined voids are particularly well suited. They can serve as a reference point for the correctness of the model used.
The modelling of irregular interstratified structures of single crystals with chemical inhomogeneity
Authors: Frank‐Kamenetskaya Olga V. , Ivanova T. I.
Published: January 2007

The possibilities of modelling of irregular interstratified structures of single crystals with chemical inhomogeneity are discussed: the theoretical basis, the requirements to the X‐ray experiment, the accuracy and reproducibility of the diffraction data, the reliability of the suggested models. The examples of the successful application of the approach to the study and description of the defect structures of single crystals belonging to different structural types are considered. Three general types of irregular interstratified structures differing in the nature of chemical inhomogeneity as well as in the peculiarities of their diffraction patterns are distinguished.
Polarity identification of GaN bulk single crystals (0001) surface by Auger electron spectroscopy
Authors: Iller Alicja , Marks Jerzy , Grzegory Izabela , Litwin‐Staszewska Elżbieta , Boćkowski Michal
Published: January 2007

An attempt to identify the polarity of (0001) polar surface of GaN bulk single crystals grown by high nitrogen pressure solution method has been made using Auger electron spectroscopy (AES). AES concentration depth profiles of the top layer in (0001) direction starting from both (0001) faces of the sample have been measured. Distinct difference in the Ga concentration at the sample surface of both faces has been observed. The dependence of Ga eoncentration on depth is also different for both faces of the sample.
CuxAg1–xGaS2 Solid Solutions
Authors: Bodnar I. V.
Published: January 2007

CuxAg1–xGaS2 large‐scale blocks were obtained by two‐temperature synthesis method with the following crystallization of the melt. It was established, that crystal lattice parameters are changed according with Vegard's law, and microhardness have an extremum on the base DTA measurements state diagram of AgGaS2CuGaS2 system was built up. The composition dependence of band gap has nonlinear behaviour.
PVT and CVT Growth and Characterization of SnSxSe2‐x (0 ≤ x ≤ 2) Single Crystals
Authors: Patel D. H. , Patel R. G. , Arora S. K. , Agarwal M. K.
Published: January 2007

Single crystals of solid solutions of tin sulphoselenide have been grown in the same ampoule. Specific conditions for growing single crystals of SnSSe have also been identified. A study of microstructures on the growth surfaces responds to the mechanism of growth of these crystals. The dependence of electrical resistivity, Hall mobility and carrier concentration with the values of the configuration parameter 2 has been studied.
Crystal Structure of the Fibrillar Zinc Trimolybdate ZnMo3O10 · 3.75 H2O by Powder Diffraction Methods
Authors: Lasocha W. , Surga W. , Hodorowicz S. , Schenk H.
Published: January 2007

The crystal structure of polycrystalline fibrillar zinc trimolybdate ZnMo3O10 · 3.75 H2O, has been solved ab initio by the Powder Diffraction — Direct Methods package POWSIM. The structure was refined by the Rietveld method with final discrepancy factors RF = 11.0 and Rwp = 21.0%. The structure consists of polymeric chains parallel to the b axis built up of MoO6 octahedra. The space group is Immm (71) with a = 8.8330(6), b = 3.8207(4), c = 15.737(2) Å V = 531,08(6) Å3, Z= 2.
Anisotropic Surface Order in the Isotropic Phase of Nematic Liquid Crystals
Authors: Harthi Salim Al , George A. K.
Published: January 2007

A spinning‐drop technique was used to study the thermal variation of surface tension of two nematic liquid crystals at the interface with an isotropic fluid. A sharp increase in interfacial tension was observed in the vicinity of the nematic‐isotropic transition. The interfacial tension‐temperature characteristics, unlike monotonically decreasing dependence found in most isotropic fluids, showed regions of positive slope, both in the isotropic and anisotropic phases. A positive slope in the isotropic region of the liquid crystal is interesting since it implies that excess order has developed at the surface while the buk interior remains isotropic.
On the curious structural phases in Al‐deficient (Al62Cu23Cr15) and Al‐rich (Al68Cu17Cr15) quasicrystalline alloys
Authors: Khare V. , Tiwari R. S. , Srivastava O. N.
Published: January 2007

In the present work investigations on the effect of stoichiometric variations on the Occurrence and stabilization of quasicrystalline (qc) and related phases have been carried out. Based on the explorations of several Al‐deficient and Al‐rich versions of the ideal nominal composition i.e. Al65Cu20Cr15, it has been found that the alloy compositions corresponding to Al62Cu23Cr15 (Al‐deficient) and Al68Cu17Cr15 (Al‐rich) exhibit several structural subtleties. The Al‐deficient alloy, has been found to exhibit crystalline bcc and fcc phases with a = 8.90 Å and a = 17.98 Å respectively. In addition to these phases, a new crystalline bcc variant (a = 15.42 Å) originating from the bcc (a = 8.90 Å) phase has been found. Also a curious superstructure of the fcc (a = 17.98 Å) has been observed. The Al‐rich alloy typified by Al68Cu17Cr15, on the other hand, does not exhibit any structural variants, instead it shows nearly pure i‐phase.
Crystal Structure Study of Co(II) Complexes with 2,2′‐(1,4‐Ethylenedioxyl) Dibenzoic Acid‐[Co · L · (H2O)3]n · nH2O· 0.2 nH2O
Authors: Yang Guang , Wang Lei , Ji Liang‐Nian , Koh Lip Lin
Published: January 2007

The structure ofS the title complex [Co. L. (H2O)3]n. nH2O. 0.2 nH2O has been established by single crystal X‐ray diffraction. Crystals of the complex are monoclinic, space group C2/c with cell constants α = 45.29(4), b=10.631(6), c = 8.015(6) Å, β = 90.65(8)°, Z = 8, Dc = 1.489 g. cm−3 The structure was solved and refined to R =0.0478 (wR = 0.0577). In the chain structure, Co(II) ions are hexacoordinated by 0 atoms in an octahedral arrangement. CoO6 octahedra share corners (bridged) through O atoms of water, with each L2‐‐ligand binding two adjacent Co atoms.
Low‐temperature Region of the In–Se System
Authors: Tedenac Prof. J.‐C. , Vassilev Dr. G. P. , Daouchi B. , Rachidi J. , Brun G.
Published: January 2007

A study of the low‐temperature region of the In–Se system has been performed by means of isothermal annealing of diffusion couples as well as by X‐ray, microscopic and microprobe analyses. Four binary compounds have been observed – In4Se3, InSe, In6Se7 and In2Se3.

Original experimental results about the crystal structure and electrical conductivities of the binary compounds have been compared with available literature data or calculated values.

A DSC study of the compound InSe has revealed that it melts peritecticly at about 618 °C.

The diffusion controlled transition from one In‐Se compound to another can be achieved without kinetic difficulties, following the phase arrangement from the equilibrium phase diagram. There are indications that small deviations from the exact stoichiometric ratios are possible.
Change of the Normal Rate of Hills Growth on the (001) Face of TGS Single Crystal Under Constant Crystallization Conditions
Authors: Bikov A. Z. , Stoichkov S. D.
Published: January 2007

Considerable change (up to 100% in one of the cases) of the normal growth rate of hills on the (001) face of the TGS crystal at strictly constant supersaturation and temperature is registered experimentally.

On the basis of the spatial disposition of the dislocations, which form the source of the steps, a model of a growth centre (called herein non‐parallel centre of growth) is proposed. The model is qualitatively concordant with the experimental data.

It is shown that the inconstancy of the normal rate of growth at constant supersaturation and temperature is an immanent characteristic of the non‐parallel centre of growth.
Changes of the Dispersive and Phase Composition of Cerox Type Polishing Material as a Result of Exploitation and Mechanoactivation
Authors: Todorovsky D. , Terziev A. , Minkova N.
Published: January 2007

The changes of the dispersive and phase composition of a Cerox type polishing material as a result of its exploitation and mechanochemical treatment are studied. A slightly expressed destruction of the solid solution CeO2‐Ln2O3 during the exploitation and mechanoactivation in water suspension (in centrifugal ball mill) is found out. The mechanoactivation models very well the changes of the dispersive composition of the polishing powder as a result of its use. A similarity in the behaviour of the wasted and the mechanoactivated materials is observed in the case of a treatment with HNO3+H2O2 mixture as well.
PVT and CVT Growth and Characterization of SnSxSe2‐x (0 ⩽ <x 2) Single Crystals
Authors: Patel D. H. , Patel R. G. , Arora S. K. , Agarwal M. K.
Published: January 2007

Single crystals of solid solutions of tin sulphoselenide have been grown in the same ampoule. Specific conditions for growing single crystals of SnSSe have also been identified. A study of microstructures on the growth surfaces responds to the mechanism of growth of these crystals. The dependence of electrical resistivity, Hall mobility, carrier concentration with the values of the configuration parameter x has been studied.
On the conduction mechanism and thermoelectric phenomena in In6S7 layer crystals
Authors: Gamal G. A.
Published: January 2007

In the present paper, measurements of the electrical conductivity and Hall coefficient on single crystal of In6S7, grown by a new crystal growth technique, were done. The crystal was found to be of n‐type conductivity. The low conductivity sample showed as the most striking feature an exponential increase of the Hall mobility with temperature. This effect was explained by assuming a mixed conduction and different scattering mechanisms for electrons and holes in the same temperature range. Also we have made thermoelectric power measurements to support this assumption. An energy gap of 0.64 eV was found.
Problems with the preparation of anhydrous single crystal sulphates. I. M2+SO4 (M = Fe, Co, Ni)
Authors: Růžička M.
Published: January 2007

The article deals with the problems retarded to preparing the single crystals of anhydrous sulphates of the iron‐metal group. The article provides a comprehensive review on up to date recent knowledge on the chemical and physical properties of these sulphates and, in addition, it describes some methods of preparing their anhydrous form. Also inform about the experiments of single crystal growth. It exhibits the facility of the solution of this problem, that is still under investigation.
In situ Observation Setup for Semiconductor Growth Interface from Solution in a Magnetic Field
Authors: Inatomi Y. , Dold P. , Danilewsky A. N. , Benz K. W.
Published: January 2007

A setup for in situ observation was developed which makes possible the optical visualization of a solid‐liquid interface during solution growth of semiconductors in an external magnetic field. This setup consisted of an optimized monoellipsoidal mirror furnace, a near‐infrared optical system, and static or rotating electromagnetic facility. The target crystals were GaP, GaAs and CdTe.
Study of Electrical Conduction Behaviour of the System Sr1‐xLaxSn1‐xCoyO3 (x = y ⩽ 0.5; x ⩽ 0.5, y = 0.00; x = 0.00; y ⩽ 0.05)
Authors: Mandal K. D. , Sastry M. S. , Christopher C. C. , Parkash Om
Published: January 2007

Single phase solid solution forms in the Sr1‐xLaSn1‐xCoyO3 (x = y) system for x⩽0.05 in the samples prepared by solid state ceramic method. A few compositions were prepared in the Sr1‐3x/2LaxSnO3 and SrSn1‐yyCoyO3‐y/2 to understand the role of La3+ and Co3+ in the electrical conduction behaviour of the system. Resistivity increases with incorppration of La3+ ions and decreases with doping of Co3+ ions. These results have been explained in terms of the defect structures of these materials.
Some Physicochemical Studies on Organic Analog of Metal‐Nonmetal Eutectics
Authors: Rai U. S. , Rai R. N.
Published: January 2007

Phase diagram, growth behaviour, thermochemistry and microstructure of organic analog of metal‐nonmetal systems, namely, urea‐succinonitrile system and diphenyl‐neopentyl alcohol system, were studied. While phase diagram study shows the formation of simple eutectic in each case, the growth kinetics investigations suggest the applicability of Hillig‐Turnbull equation to these systems. The values of entropy of fusion, enthalpy of mixing, Jackson's roughness parameter, interfacial energy and excess thermodynamic functions were calculated using enthalpy of fusion values determined by the DSC method. The microstructure of eutectics were found to be significantly different from those of the parent components.
Formation of the Perovskite Phase Pb3NiNb2O9
Authors: Balzer B. , Langbein H.
Published: January 2007

Pb3NiSNb2O9 was synthesized via various methods in order to investigate the mechanisms of perovskite formation. Two relatively simple routes to precursors that give single‐phase perovskite after calcination at 900°C are described: a modified columbite‐method and a synthesis from a freezedried complex salt solution. The results show that the formation of perovskite Pb3NiNb2O9 does not start below 900 °C and that the pyrochlore formation beginning at lower temperatures has be hindered by a thermal shock calcination.
Light Scattering Experiments during Freezing and Melting
Authors: Bilgram J.
Published: January 2007

Anomalous light scattering has been observed at the solid‐liquid interfaces of high purity systems during freezing as well as during melting. The model substances used are water, salol, cyclohexane and xenon. From light scattering experiments the existence of a layer of pre‐ordered material at the solid‐liquid interface is deduced. Light is scattered by long range fluctuations in this layer. The thickness of this layer is a few μM. The correlation length of the fluctuations in this layer has been determined to be ξ ≈ 260 nm. Dynamic and static light scattering experiments lead to the same correlation length. Xenon, salol and cyclohexane cover a range of a factor of 15 in viscosity at the melting temperature. Growth velocities have been varied by a factor of about 200. Thermal gradients at the solid‐liquid interface have been varied in a wide range. No dependence of the correlation length on these parameters or on substance has been found in the experiments. The observations do not depend on the crystallographic orientation of the crystal surface nor on the orientation of the crystal surface relative to gravity. The interface‐layer may be compared to the quasiliquid layer which has been found at crystal vapour interfaces at conditions close to the melting point. The existence of a pre‐ordered layer in‐between a crystal and its melt means that the crystal does not grow into the melt but into the pre‐ordered layer.
Structural Perfection of ZnSe Crystals Grown by Travelling Heater Method
Authors: Dohnke I. , Mühlberg M. , Neumann W.
Published: January 2007

ZnSe crystals have been grown by the travelling heater method (THM) with PbCl2 as solvent. Our investigations have shown that ZnSe crystals could be obtained with high crystalline perfection referred to a full width at the half maximum (FWHM) down to 20 arcsec of double crystal rocking curves measured at chemically polished (100)‐oriented surfaces. Solvent growth techniques like THM should have a remarkable potential for ZnSe bulk growth if the capture of solute as inclusion and precipitation can be avoided.
HVC microlesions do not destabilize the vocal patterns of adult male zebra finches with prior ablation of LMAN
Authors: Thompson John A. , Johnson Frank
Published: January 2007

The songs of adult male zebra finches (Taeniopygia guttata) arise by an integration of activity from two neural pathways that emanate from the telencephalic nucleus HVC (proper name). One pathway descends directly from HVC to the vocal premotor nucleus RA (the robust nucleus of the arcopallium) whereas a second pathway descends from HVC into a basal ganglia circuit (the anterior forebrain pathway, AFP) that also terminates in RA. Although HVC neurons that project directly to RA outnumber those that contribute to the AFP, both populations are distributed throughout HVC. Thus, partial ablation (microlesion) of HVC should damage both pathways in a proportional manner. We report here that bilateral HVC microlesions in adult male zebra finches produce an immediate loss of song stereotypy from which birds recover, in some cases within 3 days. The contribution of the AFP to the onset of song destabilization was tested by ablating the output nucleus of this circuit (LMAN, the lateral magnocellular nucleus of the anterior nidopallium) prior to bilateral HVC microlesions. Song stereotypy was largely unaffected. Together, our findings suggest that adult vocal production involves nonproportional integration of two streams of neural activity with opposing effects on song—HVC's direct projection to RA underlies production of stereotyped song whereas the AFP seems to facilitate vocal variation. However, the rapid recovery of song in birds with HVC microlesions alone suggests the presence of dynamic corrective mechanisms that favor vocal stereotypy. © 2006 Wiley Periodicals, Inc. Develop Neurobiol 67: 205–218, 2007.
Glutamate regulates neurite outgrowth of cultured descending brain neurons from larval lamprey
Authors: Ryan Sarah K. , Shotts Lindsay R. , Hong Soo‐Kyung , Nehra Deepika , Groat Carl R. , Armstrong Jon R. , McClellan Andrew D.
Published: January 2007

In larval lamprey, descending brain neurons, which regenerate their axons following spinal cord injury, were isolated and examined in cell culture to identify some of the factors that regulate neurite outgrowth. Focal application of 5 mMor 25 mML‐glutamate to single growth cones inhibited outgrowth of the treated neurite, but other neurites from the same neuron were not inhibited, an effect that has not been well studied for neurons in other systems. Glutamate‐induced inhibition of neurite outgrowth was abolished by 10 mMkynurenic acid. Application of high potassium media to growth cones inhibited neurite outgrowth, an effect that was blocked by 2 mMcobalt or 100 μMcadmium, suggesting that calcium influx via voltage‐gated channels contributes to glutamate‐induced regulation of neurite outgrowth. Application of glutamate to growth cones in the presence of 2 μMω‐conotoxin MVIIC (CTX) still inhibited neurite outgrowth, while CTX blocked high potassium‐induced inhibition of neurite outgrowth. Thus, CTX blocked virtually all of the calcium influx resulting from depolarization. To our knowledge, this is the first direct demonstration that calcium influx via ligand‐gated ion channels can contribute to regulation of neurite outgrowth. Finally, focal application of glutamate to the cell bodies of descending brain neurons inhibited outgrowth of multiple neurites from the same neuron, and this is the first demonstration that multiple neurites can be regulated in this fashion. Signaling mechanisms involving intracellular calcium, similar to those shown here, may be important for regulating axonal regeneration following spinal cord injury in the lamprey. © 2006 Wiley Periodicals, Inc. Develop Neurobiol 67: 173–188, 2007.
Electrical stimulation promotes peripheral axon regeneration by enhanced neuronal neurotrophin signaling
Authors: English Arthur W. , Schwartz Gail , Meador William , Sabatier Manning J. , Mulligan Amanda
Published: January 2007

Electrical stimulation of cut peripheral nerves at the time of their surgical repair results in an enhancement of axon regeneration. Regeneration of axons through nerve allografts was used to evaluate whether this effect is due to an augmentation of cell autonomous neurotrophin signaling in the axons or signaling from neurotrophins produced in the surrounding environment. In the thy‐1‐YFP‐H mouse, a single 1 h application of electrical stimulation at the time of surgical repair of the cut common fibular nerve results in a significant increase in the proportion of YFP+ dorsal root ganglion neurons, which were immunoreactive for BDNF or trkB, as well as an increase in the length of regenerating axons through allografts from wild type litter mates, both 1 and 2 weeks later. Axon growth through allografts from neurotrophin‐4/5 knockout mice or grafts made acellular by repeated cycles of freezing and thawing is normally very poor, but electrical stimulation results in a growth of axons through these grafts, which is similar to that observed through grafts from wild type mice after electrical stimulation. When cut nerves in NT‐4/5 knockout mice were electrically stimulated, no enhancement of axon regeneration was found. Electrical stimulation thus produces a potent enhancement of the regeneration of axons in cut peripheral nerves, which is independent of neurotrophin production by cells in their surrounding environment but is dependent on stimulation of trkB and its ligands in the regenerating axons themselves. © 2006 Wiley Periodicals, Inc. Develop Neurobiol 67: 158–172, 2007.
Eph receptor and ephrin signaling in developing and adult brain of the honeybee (Apis mellifera)
Authors: Vidovic Maria , Nighorn Alan , Koblar Simon , Maleszka Ryszard
Published: January 2007

Roles for Eph receptor tyrosine kinase and ephrin signaling in vertebrate brain development are well established. Their involvement in the modulation of mammalian synaptic structure and physiology is also emerging. However, less is known of their effects on brain development and their function in adult invertebrate nervous systems. Here, we report on the characterization of Eph receptor and ephrin orthologs in the honeybee, Apis mellifera (Am), and their role in learning and memory. In situ hybridization for mRNA expression showed a uniform distribution of expression of both genes across the developing pupal and adult brain. However, in situ labeling with Fc fusion proteins indicated that the AmEphR and Amephrin proteins were differentially localized to cell body regions in the mushroom bodies and the developing neuropiles of the antennal and optic lobes. In adults, AmEphR protein was localized to regions of synaptic contacts in optic lobes, in the glomeruli of antennal lobes, and in the medial lobe of the mushroom body. The latter two regions are involved in olfactory learning and memory in the honeybee. Injections of EphR‐Fc and ephrin‐Fc proteins into the brains of adult bees, 1 h before olfactory conditioning of the proboscis extension reflex, significantly reduced memory 24 h later. Experimental amnesia in the group injected with ephrin‐Fc was apparent 1 h post‐training. Experimental amnesia was also induced by post‐training injections with ephrin‐Fc suggesting a role in recall. This is the first demonstration that Eph molecules function to regulate the formation of memory in insects. © 2006 Wiley Periodicals, Inc. Develop Neurobiol 67: 233–251, 2007.
Overexpression of Bcl‐2 or Bcl‐xL prevents spiral ganglion neuron death and inhibits neurite growth
Authors: Hansen Marlan R. , Roehm Pamela C. , Xu Ningyong , Green Steven H.
Published: January 2007

Spiral ganglion neurons (SGNs) provide afferent innervation to the cochlea and rely on contact with hair cells (HCs) for their survival. Following deafferentation due to hair cell loss, SGNs gradually die. In a rat culture model, we explored the ability of prosurvival members of the Bcl‐2 family of proteins to support the survival and neurite outgrowth of SGNs. We found that overexpression of either Bcl‐2 or Bcl‐xL significantly increases SGN survival in the absence of neurotrophic factors, establishing that the Bcl‐2 pathway is sufficient for SGN cell survival and that SGN deprived of trophic support die by an apoptotic mechanism. However, in contrast to observations in central neurons and PC12 cells where Bcl‐2 appears to promote neurite growth, both Bcl‐2 and Bcl‐xL overexpression dramatically inhibit neurite outgrowth in SGNs. This inhibition of neurite growth by Bcl‐2 occurs in nearly all SGNs even in the presence of multiple neurotrophic factors implying that Bcl‐2 directly inhibits neurite growth rather than simply rescuing a subpopulation of neurons incapable of extending neurites without additional stimuli. Thus, although overexpression of prosurvival members of the Bcl‐2 family prevents SGN loss following trophic factor deprivation, the inhibition of neurite growth by these molecules may limit their efficacy for support of auditory nerve maintenance or regeneration following hair cell loss. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007
Locomotor activity is regulated by D2‐like receptors in Drosophila: An anatomic and functional analysis
Authors: Draper Isabelle , Kurshan Peri T. , McBride Edward , Jackson F. Rob , Kopin Alan S.
Published: January 2007

In mammals, dopamine 2‐like receptors are expressed in distinct pathways within the central nervous system, as well as in peripheral tissues. Selected neuronal D2‐like receptors play a critical role in modulating locomotor activity and, as such, represent an important therapeutic target (e.g. in Parkinson's disease). Previous studies have established that proteins required for dopamine (DA) neurotransmission are highly conserved between mammals and the fruit fly Drosophila melanogaster. These include a fly dopamine 2‐like receptor (DD2R; Hearn et al. PNAS 2002 99(22):14554) that has structural and pharmacologic similarity to the human D2‐like (D2R). In the current study, we define the spatial expression pattern of DD2R, and functionally characterize flies with reduced DD2 receptor levels. We show that DD2R is expressed in the larval and adult nervous systems, in cell groups that include the Ap‐let cohort of peptidergic neurons, as well as in peripheral tissues including the gut and Malpighian tubules. To examine DD2R function in vivo, we generated RNA‐interference (RNAi) flies with reduced DD2R expression. Behavioral analysis revealed that these flies show significantly decreased locomotor activity, similar to the phenotype observed in mammals with reduced D2R expression. The fly RNAi phenotype can be rescued by administration of the DD2R synthetic agonist bromocriptine, indicating specificity for the RNAi effect. These results suggest Drosophila as a useful system for future studies aimed at identifying modifiers of dopaminergic signaling/locomotor function. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007
Serotonin in a diencephalic nucleus controlling communication in an electric fish: Sexual dimorphism and relationship to indicators of dominance
Authors: Telgkamp Petra , Combs Nicole , Smith G. Troy
Published: January 2007

Serotonin regulates aggressive behavior. The production or release of serotonin is sexually dimorphic and related to social rank in many species. We examined serotonin expression in the central posterior/prepacemaker nucleus (CP/PPn) of the electric fish Apteronotus leptorhynchus. The CP/PPn is a thalamic nucleus that controls agonistic and reproductive electrocommunication signals known as chirps and gradual frequency rises. In parts of the CP/PPn that control chirping, females had more than twice as many serotonergic fibers and terminals as did males. Serotonin immunoreactivity in chirp‐controlling areas of the CP/PPn was also negatively correlated with two indicators of dominance: electric organ discharge (EOD) frequency and body mass. Within sexes, the negative correlation between EOD frequency and serotonergic innervation of the PPn was significant in females, but not in males. Females with higher EOD frequencies had less serotonin in the CP/PPn than did females with lower EOD frequencies. Thus, the CP/PPn contained more serotonin in females than in males, and in particular, more serotonin in females with EOD frequencies typical of social subordinates than in females with EOD frequencies typical of social dominants. These results, combined with previous findings that serotonin inhibits chirping and that females chirp much less than males, suggest that serotonin may link sex, social rank, and the production of agonistic communication signals. The relative simplicity of the neural circuits that control the EOD and chirping make the electromotor system well‐suited for studying the cellular, physiological, and behavioral mechanisms by which serotonin modulates agonistic communication. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007
Efficient DNA Cleavage Induced by Copper(II) Complexes of Hydrolysis Derivatives of 2,4,6‐Tri(2‐pyridyl)‐1,3,5‐triazine in the Presence of Reducing Agents
Authors: Borrás Joaquín , Alzuet Gloria , González‐Alvarez Marta , García‐Giménez Jose L. , Macías Benigno , Liu‐González Malva
Published: January 2007

The reaction of 2,4,6‐tri(pyridyl)‐1,3,5‐triazine (ptz) and copper(II) salts in dmf/water (1:1) results in the hydrolysis of ptz and formation of the anions bis(2‐pyridylcarbonyl)amide (ptO2–) and bis(2‐pyridylamine)amide (ptN2–), which are found in the complexes [Cu(ptN2)(OAc)]·3H2O (1), [Cu(ptO2)(OAc)(H2O)]·H2O (2), [Cu(ptN2)(for)]·3H2O (3) (for = formate), [Cu(ptO2)(for)(H2O)] (4), [Cu(ptO2)(benz)]·H2O (5) (benz = benzoate), and [Cu(ptO2)F(H2O)]2·3H2O (6). This report includes the chemical and spectroscopic characterization of all these complexes along with the crystal structures of 4–6. The coordination spheres of CuII in 4 and 5 are best described as distorted tetragonal square pyramidal for the former and distorted square planar for the latter. The crystal structure of 6 shows the presence of two discrete monomeric [Cu(ptO2)F(H2O)] entities in the crystallographic asymmetric unit in which both copper(II) ions have a distorted square‐pyramidal coordination geometry. The binding of the complexes to DNA has been investigated with the aid of viscosity and thermal denaturation studies, both of which indicate that the interaction is probably due to the outer‐sphere mechanism. The ability of the compounds to cleave DNA has also been tested. Efficient oxidative cleavage was observed in the presence of a mild reducing agent (ascorbate) and dioxygen. Mechanistic studies with reactive oxygen species (ROS) scavengers confirm that hydrogen peroxide, the hydroxyl radical, singlet oxygen‐like species, and the superoxide anion are necessary diffusible intermediates in the scission process. A mechanism involving either the Fenton or theHaber–Weiss reaction plus the formation of copper oxene species is proposed for the DNA cleavage mediated by these compounds.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Preparation, Structure and Reactivity of Polynuclear Gold(I) Phosphanyl Alkanethiolates
Authors: Battisti Antonella , Bellina Oliver , Diversi Pietro , Losi Serena , Marchetti Fabio , Zanello Piero
Published: January 2007

The homoleptic gold(I) thiolates of formula [Au(SR)]n (R = CMe3, CH2CMe3, CH2CHMe2, CPh3) have been converted into their phosphane derivatives of general formula [Au(SR)(L)] (L = PMe3, PMe2Ph, PMePh2, PPh3) and [Au2(SR)2(dppe)] [dppe = 1,2‐bis(diphenylphosphanyl)ethane], which have been characterized by elemental analysis, mass spectrometry, 1H and 31P NMR spectroscopy and cyclic voltammetry. Complexes [Au(SCMe3)(PMePh2)] (1c), [Au2(SCMe3)2(dppe)] (1e) and [Au(SCH2CMe3)(PPh3)] (3d) have been characterized in the solid state by X‐ray diffraction: no aurophilic interactions have been found. The electrochemical behaviour of these phosphane thiolato derivatives shows two irreversible oxidation processes, the first of which involves 0.5 electrons per Au–SR. Chemical oxidation by [FeCp2]BF4 produces disulfide and cationic gold(I) complexes of formula [Au2(SR)(L)2][BF4] and [Au2(SR)(dppe)][BF4], characterized by elemental analysis, mass spectrometry and 1H and 31P NMR spectroscopy. All the complexes are presumably dimeric in the solid state as shown in the case of [Au4(SCMe3)2(dppe)2][BF4]2 (5e) and [Au4(SCH2CMe3)2(PMe3)4][BF4]2 (7a), which have been fully characterized by X‐ray diffraction. The aurophilic interactions form a structure of four gold atoms with pairs of atoms bonded by bridging thiolato ligands, which are arranged in an almost perfect square in the case of 7a and in an unprecedented zigzag sequence in the case of 5e. Complex 4a reacts with HSCMe3 under basic conditions to give [Au(SCMe3)(PMe3)] and with LiX (X = Me, CH2CMe3) to give a 1:1 mixture of [AuX(PMe3)] and [Au(SCMe3)(PMe3)].(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
An Efficient Synthesis of 7,8‐Dihydropyrimido[5,4‐d]pyrimidines
Authors: Carvalho M. Alice , Esperança Sandra , Esteves Teresa , Proença M. Fernanda
Published: January 2007

7,8‐Dihydropyrimido[5,4‐d]pyrimidines 4 were isolated in very good yields by treatment of 9‐aryl‐6‐cyanopurines 1 with primary amines. Nucleophilic attack of the amine on C8 of the purine ring was followed by ring‐opening of the imidazole unit, and subsequent intramolecular cyclization involving the newly formed amidine group and the cyano substituent in the pyrimidine ring produced the 7,8‐dihydropyrimido[5,4‐d]pyrimidine structure 4. When ammonia was used instead of primary amines, compound 4 rapidly reacted further to afford the more stable pyrimido[5,4‐d]pyrimidine 6 as a result of tautomeric equilibration. The aromatic structure 6 was also isolated when purine 1a and an excess of ethanolamine were heated at reflux in methanol, and also whenpurine 1c was combined with an excess of (4‐methoxyphenyl)hydrazine in THF at room temperature in the presence of a catalytic amount of DBU. In both cases the product is formed by a Dimroth rearrangement of the precursor 7,8‐dihydropyrimido[5,4‐d]pyrimidine 4. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Formation of a Tetracyclic Isoquinoline Derivative by Rearrangement of a [(Bromophenyl)butyryl]oxazolidinone
Authors: Roydhouse Mark D. , Walton John C.
Published: January 2007

Treatment of 3‐[4‐(2‐bromophenyl)‐2‐phenylbutyryl]‐4,4‐dimethyloxazolidin‐2‐one with LDA in THF launched a domino rearrangement sequence ending in the assembly of a tetracyclic cyclopentaoxazolo[3,2‐b]isoquinolin‐6‐one derivative. Two mechanisms involving an SRN1‐type process were proposed. EPR spectroscopic and13C‐labelling experiments suggested that both were operative.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Continuous measurement of sediment transport in the Erlenbach stream using piezoelectric bedload impact sensors
Authors: Rickenmann D. , McArdell B. W.
Published: January 2007

We report on bedload transport observations using piezoelectric bedload impact sensors (PBIS), an indirect method of estimating the volume of bedload transport of coarse sediment. The PBIS device registers vibrations produced by bedload (particle diameter >∼20 mm) and records the signal as a sum of the number of impulses per time. Sediment transport at the Erlenbach stream has been continuously monitored with a PBIS array starting in 1986. The sensor array spans the width of an entire cross‐section and is mounted flush with the surface of a check dam immediately upstream of a sediment retention basin. We compare PBIS data with long‐term sedimentation records obtained from repeated surveys of material stored in the sediment retention basin, with artificial sediment input under controlled conditions in the field, and also with laboratory experiments. The rate of bedload transport is proportional to the number of impacts on the sensor per unit time. The reliability of the calibration relationship increases with the length of the observation period, e.g. for higher numbers of impacts and larger bedload volumes. Sediment volumes for individual flood events estimated with the PBIS method are in agreement with volumes estimated using an independent empirical method based on the effective runoff volume of water, the peak water discharge, and the critical discharge for the onset of sediment transport. Copyright © 2007 John Wiley & Sons, Ltd.
Short‐term rock surface expansion and contraction in the intertidal zone
Authors: Porter Neil J. , Trenhaile A. S.
Published: January 2007

Transverse micro‐erosion meter (TMEM) stations were installed in rock slabs from shore platforms in eastern Canada. The slabs were put into artificial sea water for 1, 6 or 11 hours, representing high, mid‐ and low tidal areas, respectively. The TMEMs were used to record changes in surface elevation as the rocks dried during the remainder of the 12 h of a semi‐diurnal tidal cycle. A similar technique was used on the same rock types at intertidal TMEM stations in the field, as the rocks dried during low tide. Argillite and basalt surface contraction was from 0 to 0·04 mm: there was little surface expansion. Sandstones contracted by up to 0·03 mm in the field, but there was almost no contraction in the laboratory. Argillite and basalt contraction tended to be greatest in the upper intertidal zone, and to increase with rates of longer‐term surface downwearing, but there was little relationship with rock hardness or air temperature and humidity. Changes in elevation at the same points at TMEM stations in the laboratory and field were quite consistent from one tidal cycle to the next, but there were considerable variations within single tidal cycles between different points within each station. The data suggest that contraction within the elevational zone that is normally submerged twice a day by the tides is by alternate wetting and drying. Short‐term changes in elevation are generally low compared with annual rates of downwearing owing to erosion, but they may generate stresses that contribute to rock breakdown. Copyright © 2007 John Wiley & Sons, Ltd.
Hydrodynamics in an expanded bed of large size ion‐exchange resin, and natural product adsorption
Authors: Chen Wei‐Dong , Wang Yan‐Dong , Hu Han‐Hua , Su Zhi‐Guo
Published: January 2007

Successful applications of expanded bed adsorption (EBA) technology have been widely reported in the literature for protein purification. Little has been reported on the recovery of natural products and active components of Chinese herbal preparations using EBA technology. In this study, the hydrodynamic behavior in an expanded bed of cation resin, 001 × 7 Styrene‐DVB, was investigated. Ephedrine hydrochloride (EH) was used as a model natural product to test the dynamic binding capacity (DBC) in the expanded bed. EBA of EH directly from a feedstock containing powdered herbs has also been investigated. These particles are different from commercially available expanded bed adsorbents by virtue of their large size (205 to 1030 µm). When the adsorbent bed is expanded to approximately 1.3 to 1.5 times its settled bed height, the axial liquid‐phase dispersion coefficient was found to be of the order 10−5 m2 s−1, which falls into the range 1.0 × 10−6 to 1.0 × 10−5 m2 s−1 observed previously in protein purification. Because of the favorable column efficiency (low axial dispersion coefficient), the recovery yield and purification factor values of EH directly from a feedstock reached 86.5% and 18, respectively. The results suggest that EBA technology holds promise for the recovery of natural products and active components of Chinese herbal preparations. Copyright © 2007 Society of Chemical Industry