Effect of substrate temperature on the physical properties of dc magnetron sputtered CuAlO2 films

Copper aluminum oxide films were prepared by direct current (dc) reactive magnetron sputtering under various substrate temperatures in the range of 303–648 K and systematically studied their physical properties. The physical properties of the films were strongly affected by the substrate temperature. The films formed at substrate temperatures <373 K were amorphous while those deposited at higher substrate temperatures (≥373 K) were polycrystalline in nature. The electrical properties of the films enhanced with substrate temperature due to the improved crystallinity. The Hall mobility of 9.4 cm2/V s and carrier concentration of 3.5 × 1017 cm−3 were obtained at the substrate temperature of 573 K. The optical band gap of the films decreased from 3.87 to 3.46 eV with the increase of substrate temperature from 373 to 573 K.

Constitutive modeling of shape memory alloy wire with non-local rate kinetics

A constitutive modeling approach for shape memory alloy (SMA) wire by taking into account the microstructural phase inhomogeneity and the associated solid-solid phase transformation kinetics is reported in this paper. The approach is applicable to general thermomechanical loading. Characterization of various scales in the non-local rate sensitive kinetics is the main focus of this paper. Design of SMA materials and actuators not only involve an optimal exploitation of the hysteresis loops during loading-unloading, but also accounts for fatigue and training cycle identifications. For a successful design of SMA integrated actuator systems, it is essential to include the microstructural inhomogeneity effects and the loading rate dependence of the martensitic evolution, since these factors play predominant role in fatigue. In the proposed formulation, the evolution of new phase is assumed according to Weibull distribution. Fourier transformation and finite difference methods are applied to arrive at the analytical form of two important scaling parameters. The ratio of these scaling parameters is of the order of 10(6) for stress-free temperature-induced transformation and 10(4) for stress-induced transformation. These scaling parameters are used in order to study the effect of microstructural variation on the thermo-mechanical force and interface driving force. It is observed that the interface driving force is significant during the evolution. Increase in the slopes of the transformation start and end regions in the stress-strain hysteresis loop is observed for mechanical loading with higher rates.

A sensitive immunochemical method for detecting 5mC in DNA fragments

Abstract is not available.

A gravimetric procedure for the determination of wet precipitated sulphur, dissolved sulphur, soluble sulphides and hydrogen sulphide

Elemental sulphur (in wet precipitated form or dissolved in organic solvents) and hydrogen sulphide have been determined gravimetrically at room temperature by conversion into copper sulphide by elemental copper in presence of an organic solvent such as benzene or acetonitrile. Any solvent in which sulphur is soluble can be used. The black copper sulphide formed can be weighed or determined iodometrically. Analysis indicates the black compound to be Cu1.8S. This room temperature method is a versatile one-step procedure sensitive to microgram or macro amounts of sulphur. It has been used for determining the solubility of sulphur in tetrahydrofuran and dioxan. The apparent heat of solution indicates that sulphur dissolves in these solvents without any marked solute—solvent interactions.

Low-temperature stabilization of pure Ni(IT)O

Ordinary nickel (II) oxide prepared by any of the usual methods is always contaminated with some higher valency states of nickel. Such nickel oxide however can be converted to pure nickel (II) oxide by soaking for some hours at 800–850°C in a closed system under a static inert atmosphere and in the presence of pure MnO as oxygen-getter. The resulting Ni(IT)O is highly resistant to oxidation.

High-temperature superconductivity in the 100 K region in perovskite-related oxides of the Ln-Ba-Cu-O (Ln=Y or La) system

Oxides of the Y-Ba-Cu-O system are found to show onset of superconductivity in the 100–120 K region.

Low temperature electrical transport properties of carbon matrix containing iron nanoparticles

We present a comparative study of the low temperature electrical transport properties of the carbon matrix containing iron nanoparticles and the films. The conductivity of the nanoparticles located just below the metal-insulator transition exhibits metallic behavior with a logarithmic temperature dependence over a large temperature interval. The zero-field conductivity and the negative magnetoresistance, showing a characteristic upturn at liquid helium temperature, are consistently explained by incorporating the Kondo relation and the two dimensional electron-electron interaction. The films, in contrast, exhibit a crossover of the conductivity from power-law dependence at high temperatures to an activated hopping law dependence in the low temperature region. The transition is attributed to changes in the energy dependence of the density of states near the Fermi level. The observed magnetoresistance is discussed in terms of quantum interference effect on a three-dimensional variable range hopping mechanism.

Comprehensive Path-sensitive Data-flow Analysis

Data-flow analysis is an integral part of any aggressive optimizing compiler. We propose a framework for improving the precision of data-flow analysis in the presence of complex control-flow. W initially perform data-flow analysis to determine those control-flow merges which cause the loss in data-flow analysis precision. The control-flow graph of the program is then restructured such that performing data-flow analysis on the resulting restructured graph gives more precise results. The proposed framework is both simple, involving the familiar notion of product automata, and also general, since it is applicable to any forward data-flow analysis. Apart from proving that our restructuring process is correct, we also show that restructuring is effective in that it necessarily leads to more optimization opportunities. Furthermore, the framework handles the trade-off between the increase in data-flow precision and the code size increase inherent in the restructuring. We show that determining an optimal restructuring is NP-hard, and propose and evaluate a greedy strategy. The framework has been implemented in the Scale research compiler, and instantiated for the specific problem of Constant Propagation. On the SPECINT 2000 benchmark suite we observe an average speedup of 4% in the running times over Wegman-Zadeck conditional constant propagation algorithm and 2% over a purely path profile guided approach.

On factors influencing the ductile-to-brittle transition in a bulk metallic glass

An experimental study to ascertain the ductile-to-brittle transition (DBT) in a bulk metallic glass (BMG) was conducted. Results of the impact toughness tests conducted at various temperatures on as-cast and structurally relaxed Zr-based BMG show a sharp DBT. The DBT temperature was found to be sensitive to the free-volume content in the alloy. Possible factors that result in the DBT were critically examined. It was found that the postulate of a critical free volume required for the amorphous alloy to exhibit good toughness cannot rationalize the experimental trends. Likewise, the Poisson's ratio-toughness correlations, which suggest a critical Poisson's ratio above which all glasses are tough, were found not to hold good. Viscoplasticity theories, developed using the concept of shear transformation zones and which describe the temperature and strain rate dependence of the crack-tip plasticity in BMGs, appear to be capable of capturing the essence of the experiments. Our results highlight the need for a more generalized theory to understand the origins of toughness in BMGs.

A simple, wide-range, linear thermistor-based temperature indicator

A novel thermistor-based temperature indicator using an RC oscillator and an up/down counter has been developed and described. The indicator provides linear performance over a wide dynamic temperature range of 0-100°C. This indicator is free from the error due to lead resistances of the thermistor and gives a maximum error of ±0 · 1°C in the range 0-100°C. Test results are given to support the theory.

A rapid and sensitive method for the estimation of individual tRNA pools

A rapid and sensitive method is described to quantitatively compare tRNA pools for individual aminoacids in a single experiment. The procedure comprises of: (i) charging of total tRNA with a mixture of radiolabeled aminoacids, (ii) deacylation of the esterified tRNA with a volatile base and the recovery of the labeled aminoacid, (iii) derivatisation of the aminoacid with phenylisothiocyanate after mixing with excess of nonradioactive aminoacids, (iv) baseline separation of the phenylthiocarbamyl aminoacids by reverse phase high performance liquid chromatography monitored by A254nm and (v) quantitation of the radioactivity in individual aminoacid peaks. The radioactivity in the aminoacid peak corresponds to the quantity of the aminoacylated tRNA. The method has been successfully applied to quantitate the individual tRNA pools in the developing silk glands of Bombyx mori, a functionally adapted tissue which undergoes considerable variations in tRNA content. PSG, posterior silk gland; PITC, phenylisothiocyanate; DMAA, N,N-dimethyl-N-allylamine; APH, algal protein hydrolysate; ptc-, phenylthiocarbamyl; HPLC, high performance liquid chromatography.

Frequency and temperature-dependent mobility of a charged carrier on a randomly interrupted strand

A randomly interrupted strand model of a one-dimensional conductor is considered. An exact analytical expression is obtained for the temperature-dependent ac mobility for a finite segment drawn at random, taking into account the reflecting barriers at the two open ends. The real part of mobility shows a broad resonance as a function of both frequency and temperature, and vanishes quadratically in the dc limit. The frequency (temperature) maximum shifts to higher values for higher temperatures (frequencies).

Influence of the electric field on the low-temperature thermal decomposition of ammonium perchlorate/polystyrene propellant

An electric field (100 V/cm at 230°C and 150°C) has been applied to ammonium perchlorate (AP)/polystyrene (PS) propellant mixtures in order to understand the low temperature decomposition behavior of the propellant. The charge-carrying species is anionic in nature at 230°C, which could be ClO4−, but is cationic at 150°C, which could be either NH4+ or H+. These results are parallel to that observed for pure ammonium perchlorate (AP) pellets [1]. The burning rate (r' ) of the propellant was found to follow the same trend as that for the thermal decomposition of the propellant on application of an electric field. At 150°C Image was higher at the −ve electrode than at the +ve electrode, but at 230°C just the opposite was observed. Kinetic studies have confirmed that the decomposition of the orthorhombic AP follows two mechanism corresponding to E = 30 kcal mol−1 (180–230°C) and E = 15 kcal mol−1 (150–180°C).

High temperature stability of oxysulfides containing Ce3+ and Y3+ ions

Standard Gibbs energies of formation of oxysulfides of cerium and yttrium from their respective oxedes were determined using solid oxide galvanic cells incorporating calcia-stabilized zirconia as the electrolyte in the temperature range 870–1120 K. The sulfur potential over the electrode containing the oxide and oxysulfide was fixed by a buffer mixture of Ag + Ag2S. A small amount of CaH2 was added to the buffer to generate an equilibrium ratio of H2S and H2 species in a closed system containing the buffer and the electrode. The sulfur potential is transmitted to the electrode via the gas phase. The results can be summarized by the equations 2left angle bracketCeO2right-pointing angle bracket+1/2(S2)→left angle bracketCe2O2Sright-pointing angle bracket+(O2) ΔG°=430600−109·7T(±400)J mol−1 left angle bracketY2O3right-pointing angle bracket+1/2(S2)→left angle bracketY2O2Sright-pointing angle bracket+1/2(O2) ΔG°=114780−1·45T(±200)J mol−1 The values are compared with data reported in the literature. The stability field diagram for the Ce---O---S system has been developed using the results of this study for Ce2O2S and data for other phases from the literature.

A study of the effect of N2 reservoir temperature on a 16 μm CO2-N2 downstream-mixing gasdynamic laser

A study of the effect of N2 reservoir temperature on the small-signal gain in a downstream-mixing 16 μm CO2-N2 GDL is presented. It is shown that the small-signal gain decreases with the increase of N2 reservoir temperature. The conditions for reversing this trend are discussed and the results are presented in the form of graphs.