Pre-exponential factor in<Emphasis Type="Italic">a</Emphasis>-Se<Subscript>75</Subscript>In<Subscript>25-<Emphasis Type="Italic">x</Emphasis></Subscript>Pb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> thin films

Temperature dependence of d.c. conductivity is studied ina- Se₇₅In_25-x Pb _x thin films wherex is varied from 0–10. From these measurements, the values of the pre-exponential factor (σ₀) and activation energy (ΔE) are calculated for each glassy alloy. An approximate linear dependence of ln σ₀ on AE is observed in this glassy system with good agreement between the expected and calculated σ₀ values using Meyer-Neldel rule. Linear dependence of ln σ₀ on ΔE in case of amorphous materials indicates that the conduction band tails a finite energy distance towards the valence band and Fermi level is controlled by fixed dominant hole levels deeper in the gap.     

Magneto-Peltier cooling of single-crystal Bi<Subscript>1-<Emphasis Type="Italic">X</Emphasis></Subscript>Sb<Subscript><Emphasis Type="Italic">X</Emphasis></Subscript> (<Emphasis Type="Italic">X </Emphasis>= 0.12 and 0.15) alloys

The cooling temperatures of rectangular parallelepiped Bi_1-X Sb _X (X = 0.12 and 0.15) single-crystals with the same thickness of t = 2 mm but different width W were measured at 113 K and 290 K as a function of electric current in the magnetic field B up to 2.17 T. The magnetic field was aligned along the thickness t of a sample and the current flows along its length L through the copper leads soldered to both end surfaces of cross section (W × t), where W, t and L are parallel to the binary, bisector and trigonal axes of the single-crystal, respectively. The thermoelement was not in contact with a heat sink. The cooling temperature of Bi_0.85Sb_0.15 at 290 K was increased with an increase of B and was almost symmetric for the reverse of the field direction, while at 113 K it exhibited a maximum at B = ±0.25 T and a strong asymmetry for the field direction. The largest maximum cooling temperature ΔT _max of Bi_0.85Sb_0.15 was achieved when a thermoelement has optimum dimensions so that heat energy is hardly generated at the cold side. When the single-crystal Bi_0.85Sb_0.15 alloy has optimum dimensions of L = 15 mm, W = 4 mm and t = 2 mm, the ΔT _max at 290 K increased from 4.2 K in B = 0 T to 9.6 K in B = +2.17 T, so that it exceeded ΔT _max values of 5.7 K obtained for a typical Bi₂Te₃ and 8.5 K measured previously for Bi single-crystal in B = +2.17 T.     

Optical band gap in the system ZnO<Subscript>1 – <Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>. An experimental and quantum chemical study

The synthesis of single crystalline and polycrystalline material is reported in the system ZnO_{1 – x} S _x . Substitution of oxygen by sulphur yields hexagonal wurtzite-type mixed crystals in the range 0 ≤ x ≤ 0.05. The cubic zincblende structure is observed for oxygen incorporation into ZnS for 0.96 ≤ x ≤ 1. At intermediate compositions, the system is two-phase. For both types of anion substitution, the band gap energies, as determined from optical transmission and remission experiments, are found to decrease from the pure end members. Quantum chemical calculations at density functional level identify local structural changes as the main factor responsible for the reduction of band gap energies.     

The thermodynamic properties of liquid binary mixtures of <Emphasis Type="Italic">n</Emphasis>-alkanes: <Emphasis Type="Italic">n</Emphasis>-decane + <Emphasis Type="Italic">n</Emphasis>-hexadecane

Data on sound velocity are used for determining the density, the isobaric expansion coefficient, the isobaric and isochoric heat capacity, and the isothermal compressibility of liquid binary mixture of n-decane + n-hexadecane of three compositions in the temperature range of 298–433 K and pressure range of 0.1–100 MPa. The coefficients of Tait equation are calculated in the above-identified range of parameters. The calculation results are compared with experimental data on density. The divergence does not exceed 0.2% for the most reliable data.     

Electrical properties of photodiodes based on <Emphasis Type="Italic">p</Emphasis>-GaSb/<Emphasis Type="Italic">p</Emphasis>-GaInAsSb/<Emphasis Type="Italic">N</Emphasis>-GaAlAsSb heterojunctions

We have studied the electrical characteristics of photodiodes based on p-GaSb/p-GaInAsSb/N-GaAlAsSb heterojunctions and investigated the mechanisms of current transfer in these heterostructures at various temperatures. A comparison of the theoretical results and experimental data showed that the tunneling charge transfer mechanism dominates at low temperatures (T < 150 K) under both forward and reverse bias conditions. The tunneling current becomes a determining factor at an electric field strength in the p-n junction of no less that 10⁵ V/cm, which is related to a small bandgap width of the materials studied and low effective masses of electrons and holes.     

Ab-initio Calculation of Electronic and Magnetic Properties of Mn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Cr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te

The electronic and magnetic properties of Mn_1−x Cr _x Te of NiAs-type and zinc-blend type structures are theoretically investigated using the first-principles KKR-CPA method. It is concluded that at low concentration region of Cr, an antiferromagnetic state is the ground-state, while a ferrimagnetic state is more stable at higher concentration region of Cr in the both types of structures. In particular, a new type of half-metallic ferrimagnets is found in zinc-blend type Mn_1−x Cr _x Te. On the other hand, a nearly half-metallic behavior is observed in NiAs-type Mn_1−x Cr _x Te, where the Fermi level locates slightly above the minority spin band gap. The features of the half-metallicity of Mn_1−x Cr _x Te in zinc-blend structure are also seen in the results of the conductivity calculations using the Kubo–Greenwood formula.     

Nuclear-Physical Properties of <Superscript>105, 106<Emphasis Type="Italic">m</Emphasis>, 110<Emphasis Type="Italic">m</Emphasis></Superscript>Ag

The nuclear-physical properties of the nuclides ^{105, 106m,110m} Ag, which are concomitant nuclides in reactor production of ¹⁰³Pd and ¹⁰⁹Cd used in metrology of ionizing radiations and in nuclear medicine, were studied. The following quantities were determined by semiconductor X-ray and γ-ray spectrometry: the parameter K _α/K _β of X-ray K radiation accompanying the decay of ^110m Ag and the intensities of γ-ray quanta with the energies of 280 and 345 keV (¹⁰⁵Ag); 430, 451, and 512 keV (^106m Ag); 658, 764, 885, 938, and 1384 keV (^110m Ag). The half-lives determined using the above γ-ray lines are as follows: T _1/2(¹⁰⁵Ag) = 41.2 ± 0.1 days; T _1/2(^106m Ag) = 8.30±0.07 days. The errors are given for 95% confidence level.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 31–34.Original Russian Text Copyright © 2005 by Popov, Zakharova, Sadulin, Andreev, Pakhomov.     

Generalization of <Emphasis Type="Italic">T</Emphasis> and <Emphasis Type="Italic">A</Emphasis> integrals to time-dependent materials: analytical formulations

This paper deals with the generalization of T-integral to crack growth process in viscoelastic materials. In order to implement this expression in a finite element software, a modelling form of this integral, called Aθ, is developed. The analytical formulation is based on conservative law, independent path integral, and a combination of real, virtual displacement fields, and real, virtual thermal fields introducing, in the same time, a bilinear form of free energy density F. According to the generalization of Noether’s method, the application of Gauss Ostrogradski’s theorem combined with curvilinear cracked contour, T _v is obtained. By introducing a volume domain around crack tip, the modelling expression Aθ is also defined.. Finally, the viscoelastic generalization through a thermodynamic approach, called A _v , is introduced by using a discretisation of the creep tensor according to a generalized Kelvin Voigt representation.     

<Emphasis Type="Italic">SH</Emphasis>-wave intromission concept

The existence of an SH-wave incidence angle for which the reflected amplitude is zero (SH-wave intromission angle) is established for the case of plane-wave scattering by a planar interface joining two homogeneous, isotropic, and linearly elastic half-spaces. Such an incidence angle is numerically shown to exist for two combinations of bimaterial interface properties. The SH-wave intromission angle is roughly parallel to the electromagnetic Brewster angle and the acoustic P-wave intromission angle, and the concept should find new applications for non-intrusive characterization of interfaces.     

Electrical impedance of ethylene-carbon monoxide/propylene-carbon monoxide (<Emphasis Type="Italic">EPEC</Emphasis>-<Emphasis Type="Italic">69</Emphasis>) thermoplastic polyketone

Electrical impedance technique was employed to investigate the electrical properties of ethylene-carbon monoxide/propylene-carbon monoxide terpolymer (EPEC-69). The measurements were performed in the frequency range 0.1–10⁵ Hz and in the temperature range 30–110 °C. The results reveal that the dielectric constant, loss factor, modulus, and ac conductivity are dependent of frequency and temperature. A Debye relaxation peak was detected in the plot of Z″ versus frequency where the activation energy was determined and found to be 1.26 eV. When the surface phenomenon effects were separated using the imaginary part of the complex admittance a second dielectric dispersion was observed in the low frequency region. Two models were proposed from the impedance measurements depending on temperature range.     

Ionic Conductivity of Ln<Subscript>2 + <Emphasis Type="Italic">x</Emphasis></Subscript>Zr<Subscript>2 − <Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>7 − <Emphasis Type="Italic">x</Emphasis>/2</Subscript> (Ln = Sm-Gd) Solid Solutions

The electrical conductivity of Ln_{2 + x} Zr_{2 − x} O_{7 − x/2} (Ln = Sm-Gd) solid solutions prepared from mechanically activated Ln₂O₃ and ZrO₂ is shown to correlate with their structural properties. In the three systems, the x-T regions are determined in which electrical transport is dominated by oxygen-ion conduction. In the Sm₂O₃-ZrO₂ system, ionic conductivities from 5 × 10⁻⁴ to 6 × 10⁻³ S/cm at 740°C are found in Sm_{2 + x} Zr_{2 − x} O_{7 − x/2} with 26.6, 33.3, 35.5, 37, and 40 mol % Sm₂O₃ prepared at 1450, 1530, and 1600°C. Eu_{2 + x} Zr_{2 − x} O_{7 − x/2} and Gd_{2 + x} Zr_{2 − x} O_{7 − x/2} containing 33.3 to 37 mol % Ln₂O₃ have 740°C ionic conductivities of 10⁻³ to ∼7.5 × 10⁻³ and 10⁻³ to 7 × 10⁻³ S/cm, respectively. The activation energy of conduction in Ln_{2 + x} Zr_{2 − x} O_{7 − x/2} (Ln = Sm-Gd), E _a = 0.84–1.04 eV, increases with the atomic number of Ln and x. The highest ionic conductivity is offered by the stoichiometric Ln₂Zr₂O₇ (Ln = Sm-Gd) pyrochlores prepared at 1600°C, owing to the optimal concentration of Ln_Zr + Zr_Ln antistructure pairs (∼5–22%). The grains in the ceramic samples studied range in size from 0.5 to 2 µm.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 8, 2005, pp. 975–984.Original Russian Text Copyright © 2005 by Shlyakhtina, Kolbanev, Knotko, Boguslavskii, Stefanovich, Karyagina, Shcherbakova.     

Optical,structural and electrical investigations on PbTe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> alloys

The fabrication of devices with lead salts and their alloys with detecting and lasing capabilities has been an important technological development. The high quality polycrystalline thin films of PbTe_1−x S _x with variable composition (0 ≤ x ≤ 1) have been deposited onto ultra clean glass substrates by vacuum evaporation technique. Optical, structural and electrical properties of PbTe_1−x S _x thin films have been examined. Absorption coefficient and band gap of the films were determined by absorbance measurements in wavelength range 2,500–5,000 nm using FTIR spectrophotometer. Sample nature, crystal structure and lattice parameter of the films were determined from X-ray diffraction patterns. DC conductivity and activation energy of the films were measured in temperature range 300–380 K through I–V measurements.     

Properties of Mg(Fe<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript>O<Subscript>4 + δ</Subscript> solid solutions in stable and metastable states

Using pyrohydrolytic synthesis, we have obtained a continuous series of Mg(Fe_{1 − x} Ga _x )₂O_{4 + δ} solid solutions, as checked by X-ray diffraction. The magnetization and coercivity of the samples have been determined from field dependences in applied magnetic fields of ±5 T, and their conductivity has been assessed using current-voltage measurements at 300 K in electric fields from −200 to +200 V. The effective band gap of the solid solutions has been evaluated from their absorption spectra obtained by diffuse reflectance measurements. The optimal composition for spintronic applications is Mg(Fe_0.8Ga_0.2)₂O_{4 + δ}.     

Gravireception in <Emphasis Type="Italic">Phycomyces Blakesleeanus</Emphasis> and <Emphasis Type="Italic">Arabidopsis Thaliana</Emphasis>: Hysteretic Behavior of Primary Reactions

The gravireception of the fungus Phycomyces blakesleeanus and seedlings of Arabidopsis thaliana is accompanied by gravity-induced absorption changes (GIACs) that occur very fast and most likely represent primary responses of gravireception. GIACs that were analyzed during parabolic flights in micro- and hypergravity invariably display hysteretic behavior. Even though the identity of the pigments generating the GIACs remain presently unknown, it is nevertheless clear that they are specific for gravireception. This is strongly suggested by the fact that hystereses loops of wild-type specimen are significant larger than of gravitropic mutants. Hystereses are largely kinetically determined, are specific for the different organisms and stimulus programs, and thus aid in characterizing the requisite transduction chains of gravireception. The fact that monocot as well as dicot plants display GIACs just in the area of highest gravitropic sensitivity at the tip supports the conclusion that gravireception is generally associated with primary reactions.     

Structural,Superconducting, and Magnetic Properties of Y<Subscript>1- <Emphasis Type="Italic">x</Emphasis></Subscript>Dy<Subscript>x</Subscript>Rh<Emphasis Type="Italic">4</Emphasis>B<Emphasis Type="Italic">4</Emphasis> Borides

Samples with nominal compositions Y_1-x Dy_xRh₄B₄ are prepared by argon-atmosphere arc melting. The phase composition of the samples and the elemental compositions of the individual phases present are determined by x-ray diffraction and electron-probe x-ray microanalysis. The results indicate that increasing the dysprosium content of the starting mixture increases the percentage of the magnetic phase and reduces that of the superconducting phase in the samples. The electrical resistivity, magnetic susceptibility, and magnetic moment of the samples are measured between 1.6 and 30 K (magnetic fields of up to 14 T). The magnetic phase present in the samples with 0.2 ≤ × ≤ is shown to undergo ferromagnetic ordering at T _magn ≃ 13–13.5 K. The samples with 0 ≤ × ≤ 0.6 contain a superconducting phase with T _c from 9.1 to 5.0 K. The superconducting and magnetic properties of the Y_0.6Dy_0.4Rh₄B₄ sample are examined in detail.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 6, 2005, pp. 676–681.Original Russian Text Copyright © 2005 by Burkhanov, Lachenkov, Kuz’micheva, Kovneristyi, Khlybov, Kostyleva, Tomilin.     

<Emphasis Type="Italic">hg</Emphasis>-index: a new index to characterize the scientific output of researchers based on the <Emphasis Type="Italic">h</Emphasis>- and <Emphasis Type="Italic">g</Emphasis>-indices

To be able to measure the scientific output of researchers is an increasingly important task to support research assessment decisions. To do so, we can find several different measures and indices in the literature. Recently, the h-index, introduced by Hirsch in 2005, has got a lot of attention from the scientific community for its good properties to measure the scientific production of researchers. Additionally, several different indicators, for example, the g-index, have been developed to try to improve the possible drawbacks of the h-index. In this paper we present a new index, called hg-index, to characterize the scientific output of researchers which is based on both h-index and g-index to try to keep the advantages of both measures as well as to minimize their disadvantages.     

Thermal decomposition of trimethylamine borane as a precursor to nanocrystalline CVD BC<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>N<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> films

We have studied the kinetics of BC _x N _y chemical vapor deposition through trimethylamine borane decomposition at atmospheric pressure. The rate constant of the heterogeneous interaction between trimethylamine borane and an adsorption center has been determined to be k _s ⁰ = 2.7 × 10⁷exp(−10560/T) cm/s. The obtained kinetic parameters of the reaction fully determine the growth rate of nanocrystalline carbonitride films under kinetic control. The film thickness has been determined as a function of time, temperature, reactant concentration, and reactor dimensions.     

Combination of <Emphasis Type="Italic">Eigenfactor</Emphasis><Superscript>TM</Superscript> and <Emphasis Type="Italic">h-</Emphasis>index to evaluate scientific journals

The h-index and Eigenfactor ^TM values of top and specialized scientific/engineering journals are tabulated and combined to provide a simple graphical representation of the journals. The information may be tailored to specific uses by respective stakeholders to aid decision making processes with regards to scholarly research and scientific journal publications.     

The <Emphasis Type="Italic">α–β</Emphasis> Transition of Nitrogen

It is well-known that, aside from its triple point, nitrogen exhibits a solid-to-solid transition at about 35 K that is of some interest as a secondary reference temperature. During the recently published highly accurate measurements of the triple point of nitrogen (Metrologia 43, 435 (2006)), an extensive study was made also of the solid α–β transition of nitrogen, using both the continuous heating method and the pulse-heating method. This transition is of significantly lower quality than the triple point of nitrogen. A very high thermal resistance and a large time constant characterize the transition. Therefore, even the determination of the self-heating of the thermometer requires a very long time. A value of T ₉₀ = 35.620 K with an expanded uncertainty U = 8 mK for the coverage factor k = 2 was found, differing by +6 mK from the published CCT-recommended value. The reproducibility of the value was better than ± 5 mK. In addition to the temperature value found for the transition, a comparison is made with previous measurements on this point, and an overview is given of the available information about it.     

Unusual magnetic and transport properties of the CMR Pr<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Ca<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>MnO<Subscript>3−<Emphasis Type="Italic">y</Emphasis></Subscript> system

The substituted nonstoichiometric perovskite Pr_1−x Ca _x MnO_3−y compounds have been synthesized by a standard combustion technique, which show uniphase solid solutions. The all samples of the Pr_1−x Ca _x MnO_3−y system show an orthorhombic crystal system and the cell volumes are decreased with increasing the larger amounts of substituted atoms or the increasing x values. The mixed valence of Mn ions is identified by the XAS (XANES/EXAFS) spectroscopy and the amounts of Mn⁴⁺ ions are determined by an iodometric titration method. Nonstoichiometric chemical formulas of the Pr_1−x Ca _x Mn_1−τ³⁺Mn_τ⁴⁺O_3−y compounds have been obviously formulated. Magnetic properties are investigated by SQUID and thus the Pr_1−x Ca _x MnO_3−y (x = 0.4, 0.6, and 0.8) compounds show the transition from antiferromagnetic state to paramagnetic state. The Pr_1−x Ca _x MnO_3−y (x = 0.0, 0.2, and 1.0) compounds show the transition from ferromagnetic state to paramagnetic state. The facts that Mn⁴⁺ contents play important roles in the magnetic ordering have been found out. The transport properties have been studied by the DC electrical conductivity measurement under magnetic fields of 0 G and 3 kG. Maximum and minimum MR ratios are 1016% of the Pr_0.6Ca_0.4MnO_2.846, and −77.5% of the PrMnO_3.021 compound, respectively.