Growth of rutile TiO2 nanorods on TiO2 seed layer deposited by electron beam evaporation

Dense rutile TiO2 nanorods were grown on anatase TiO2 seed layer coated glass substrate by solution technique. The crystalline nature of nanorods has confirmed by transmission electron microscopy. The band gap of the TiO2 seed layer and nanorods were calculated using the UV-vis absorption spectrum and the band gap value of the anatase seed layer and rutile nanorods were 3.39 eV and 3.09 eV respectively. Water contact angle measurements were also made and showed that the contact angle of rutile nanorods was (134 degrees) larger than the seed layer contact angle (93 degrees). The RMS surface roughness of the TiO2 seed layer (0.384 nm) and nanorods film (18.5 nm) were measured by an atomic force microscope and correlated with their contact angle values. (C) 2011 Elsevier B.V. All rights reserved.

Phase separation by nanoparticle splitting

The present report illustrates the phenomenon of phase separation leading to the splitting of solid solution structured Ag-Co nanoparticles into pure Ag and pure Co nanoparticles upon isothermal annealing inside a transmission electron microscope. In bulk, Ag-Co system shows negligible mutual solubility into a single phase solid solution structure upto a very high temperature. The Ag-Co nanoparticle splitting revealed that room temperature, solid solution atomic configuration, between bulk immiscible Ag and Co atoms coexisting in a nano-sized particle, is a kinetically frozen atomic arrangement and not a thermodynamically stable structure. The observed phase separation behavior resulting in particle splitting at high temperatures can be used to produce devices for sensor applications. (C) 2011 Elsevier B.V. All rights reserved.

Higher spin quasinormal modes and one-loop determinants in the BTZ black hole

We solve the wave equations of arbitrary integer spin fields in the BTZ black hole background and obtain exact expressions for their quasinormal modes. We show that these quasinormal modes precisely agree with the location of the poles of the corresponding two point function in the dual conformal field theory as predicted by the AdS/CFT correspondence. We then use these quasinormal modes to construct the one-loop determinant of the higher spin field in the thermal BTZ background. This is shown to agree with that obtained from the corresponding heat kernel constructed recently by group theoretic methods.

Higher spin fermions in the BTZ black hole

Recently it has been shown that the wave equations of bosonic higher spin fields in the BTZ background can be solved exactly. In this work we extend this analysis to fermionic higher spin fields. We solve the wave equations for arbitrary half-integer spin fields in the BTZ black hole background and obtain exact expressions for their quasinormal modes. These quasinormal modes are shown to agree precisely with the poles of the corresponding two point function in the dual conformal field theory as predicted by the AdS/CFT correspondence. We also obtain an expression for the 1-loop determinant for the Euclidean non-rotating BTZ black hole in terms of the quasinormal modes which agrees with that obtained by integrating the heat kernel found by group theoretic methods.

Optical, electrochemical and morphological investigations of poly (3,4-propylenedioxythiophene)-sultone (PProDOT-S) thin films

In this paper, we have carried out thin film characterization of poly(3,4-propylenedioxythiophene)-sultone (PProDOT-S), a derivative of electrochromic poly(3,4-propylenedioxythiophene) (PProDOT). PProDOT-S was deposited onto transparent conducting oxide coated glass substrates by solution casting method. Single wavelength spectrophotometry is used to monitor the switching speed and contrast ratio at maximum wavelength (lambda (max)). The percentage transmittance at the lambda (max) of the neutral polymer is monitored as a function of time when the polymer film is repeatedly switched. This experiment gives a quantitative measure of the speed with which a film is able to switch between the two states i.e. the coloured and the bleached states. PProDOT-S films were switched at a voltage of 1 center dot 9 V with a switching speed of 2 s at lambda (max) of 565 nm and showed a contrast of similar to 37%. Cyclic voltammetry performed at different scan rates have shown the characteristic anodic and cathodic peaks. The structural investigations of PProDOT-S films by IR spectra were in good agreement with previously reported results. Raman spectra of PProDOT-S showed a strong Raman peak at 1509 cm (-aEuro parts per thousand 1) and a weak peak at 1410 cm (-aEuro parts per thousand 1) due to the C = C asymmetric and symmetric stretching vibrations of thiophene rings. The morphological investigations carried out by using scanning electron microscope (SEM) of polymer films have shown that these polymers are found to be arranged in dense packed clusters with non-uniform distribution having an average width and length of 95 nm and 160 nm, respectively.

System Gd-Rh-O: Thermodynamics and phase relations

Thermodynamic properties of GdRhO3 are investigated in the temperature range from 900 to 1300 K by employing a solid-state electrochemical cell, incorporating calcia-stabilized zirconia as the electrolyte. The standard Gibbs free energy of formation of GdRhO3 from component binary oxide Gd2O3 with C-rare earth structure and Rh2O3 with orthorhombic structure can be expressed as; Delta G(f(ox))(o)(+/- 60)/J mol(-1) = -56603 + 3.78(T/K) Based on the thermodynamic information on GdRhO3 from experiment and auxiliary data for binary oxides from the literature and estimated properties of Gd-Rh alloys, phase relations are computed for the system Gd-Rh-O at 1273 K. Gibbs free energies for intermetallic phases in the binary Gd-Rh are evaluated using calorimetric data available in the literature for two compositions and Miedema's model, consistent with the binary phase diagram. Isothermal section of the ternary phase diagram, oxygen potential-composition diagram and a 3-D chemical potential diagram for the system Gd-Rh-O at 1273 K are developed. Phase relations in the ternary Gd-Rh-O are also computed as a function of temperature at constant oxygen partial pressures. The ternary oxide, GdRhO3 decomposes to Gd2O3 with B-rare earth structure, metallic Rh and O-2 at 1759(+/- 2) K in pure O-2 and 1649(+/- 2) K in air at a total pressure P-0 -0.1 MPa. (c) 2012 Elsevier B.V. All rights reserved.

Growth of branched carbon nanotubes with doped/un-doped intratubular junctions by one-step co-pyrolysis

Branched CNTs with nitrogen doped/un-doped intratubular junctions have been synthesized by a simple one-step co-pyrolysis of hexamethylenetetramine and benzene. The difference in the vapor pressure and the insolubility of the precursors are the keys for the formation of the branched intratubular junctions. The junctions behave like Schottky diodes with nitrogen-doped portion as metal and un-doped portion as p-type semiconductor. The junctions also behave like p-type field effect transistors with a very large on/off ratio.

Tensile flow and work hardening behavior of hot cross-rolled AA7010 aluminum alloy sheets

The present work describes the tensile flow and work hardening behavior of a high strength 7010 aluminum alloy by constitutive relations. The alloy has been hot rolled by three different cross-rolling schedules. Room temperature tensile properties have been evaluated as a function of tensile axis orientation in the as-hot rolled as well as peak aged conditions. It is found that both the Ludwigson and a generalized Voce-Bergstrom relation adequately describe the tensile flow behavior of the present alloy in all conditions compared to the Hollomon relation. The variation in the Ludwigson fitting parameter could be correlated well with the microstructural features and anisotropic contribution of strengthening precipitates in the as-rolled and peak aged conditions, respectively. The hardening rate and the saturation stress of the first Voce-Bergstrom parameter, on the other hand, depend mainly on the crystallographic texture of the specimens. It is further shown that for the peak aged specimens the uniform elongation (epsilon(u)) derived from the Ludwigson relation matches well with the measured epsilon(u) irrespective of processing and loading directions. However, the Ludwigson fit overestimates the epsilon(u) in case of the as-rolled specimens. The Hollomon fit, on the other hand, predicts well the measured epsilon(u), of the as-rolled specimens but severely underestimates the epsilon(u), for the peak aged specimens. Contrarily, both the relations significantly overestimate the UTS of the as-rolled and the peak aged specimens. The Voce-Bergstrom parameters define the slope of e Theta-sigma plots in the stage-III regime when the specimens show a classical linear decrease in hardening rate in stage-III. Further analysis of work hardening behavior throws some light on the effect of texture on the dislocation storage and dynamic recovery.

Chromium isotope variations (delta Cr-53/52) in mantle-derived sources and their weathering products: Implications for environmental studies and the evolution of delta Cr-53/52 in the Earth's mantle over geologic time

Here we report chromium isotope compositions, expressed as delta Cr-53/ 52 in per mil (&) relative to NIST 979, measured in selected Cr-rich minerals and rocks formed by the primary magmatic as well as the secondary metamorphic and weathering processes. The main objectives of this study were: (i) to further constrain the isotope composition of the Earth's mantle Cr inventory and its possible variation during geological history, based on the analysis of globally distributed and stratigraphically constrained mantle-derived chromites; and (ii) to investigate the magnitude and systematics of Cr isotope fractionation during oxidative weathering and secondary alteration (i. e., hydration, serpentinization) of the magmatic Cr sources. Specifically, we analyzed delta Cr-53/ 52 in a set of globally distributed mantle-derived chromites (FeMgCr2O4, n = 30) collected from various locations in Europe, Asia, Africa and South America, and our results confirm that a chromite-hosted Earth's mantle Cr inventory is uniform at - 0.079 +/- 0.129& (2SD), which we named here as a ` canonical' mantle d 53/ 52 Cr signature. Furthermore our dataset of stratigraphically constrained chromites, whose crystallization ages cover most of the Earth's geological history, indicate that the bulk Cr isotope composition of the chromite-hosted mantle inventory has remained uniform, within about +/- 0.100&, since at least the Early Archean times (similar to 3500 million years ago, Ma). To investigate the systematics of Cr isotope fractionation associated with alteration processes we analyzed a number of secondary Cr-rich minerals and variably altered ultramafic rocks (i. e., serpentinized harzburgites, lherzolites) that revealed large positive delta Cr-53/ 52 anomalies that are systematically shifted to higher values with an increasing degree of alteration and serpentinization. The degree of aqueous alteration and serpentinization was quantified by the abundances of fluid-mobile (Rb, K) elements, and by the Loss On Ignition (LOI) parameter, which determines the amount of structurally bound water (OH/ H2O) present in secondary hydrated minerals like serpentine. Overall, we observed that altered ultramafic rocks that yielded the highest LOI values, and the lowest amounts of fluid mobile elements, also yielded the heaviest delta Cr-53/ 52 signatures. Therefore, we conclude that secondary alteration (i.e., hydration, serpentinization) of ultramafic rocks in near-surface oxidative environments tend to shift the bulk Cr isotope composition of the weathered products to isotopically heavier values, pointing to a dynamic redox cycling of Cr in the Earth's crustal and near-surface environments. Hence, if validated by future

Toward the total synthesis of a lagunamide B analogue

Lagunamides, isolated from a marine cyanobacterium Lyngbya majuscule found in Singapore, showed very potent activities against Plasmodium falciparum and murine leukemia cell line (P388). Herein, a concise synthetic approach toward the total synthesis of a lagunamide B analogue is discussed. Macrolactonization, HWE-olefination, and modified Crimmin's aldol are some of the key reactions featured in this synthesis. (C) 2014 Elsevier Ltd. All rights reserved.

Dissimilar friction stir welding between aluminum alloy and magnesium alloy at a low rotational speed

A sound weld was obtained between 2024-T3 Al alloy and AZ31B-O Mg alloy dissimilar metal plates of 5 mm thickness, at a rotational speed of 300 rev min(-1) and at a welding speed of 50 mm min(-1). One of the parameter studied was, the effect of interface offset variation, on the quality and properties of the welded samples and on the thickness of intermetallic layer formed in the welded samples. The intermetallic layer at the midst of the weld volume contains intermetallic compounds Al12Mg17 and Al3Mg2. Highest tensile strength of 106.86 MPa, corresponding tensile joint efficiency of 44.52% and corresponding elongation 1.33% were obtained for the tensile sample, with interface offset of 0.66 mm from zero interface offset in retreating side and with approximate least intermetallic thickness of 1.2 mu m. Dissimilar friction stir welded joint samples had failed completely in brittle fracture mode; the position of tensile fracture was located at the midst of intermetallic layer, which had maximum hardness and minimum ductility. The nano hardness values fluctuate in the weld nugget owing to dynamic recrystallization of alloy materials and formation of brittle intermetallic compounds of alloy materials in the weld nugget; maximum hardness of 10.74 GPa occurred for the sample with least intermetallic thickness of 1.2 mu m. (C) 2014 Elsevier B.V. All rights reserved.

Spectral intensity distribution of trapped

To calculate static response properties of a many-body system, local density approximation (LDA) can be safely applied. But, to obtain dynamical response functions, the applicability of LDA is limited bacause dynamics of the system needs to be considered as well. To examine this in the context of cold atoms, we consider a system of non-interacting spin4 fermions confined by a harmonic trapping potential. We have calculated a very important response function, the spectral intensity distribution function (SIDF), both exactly and using LDA at zero temperature and compared with each other for different dimensions, trap frequencies and momenta. The behaviour of the SIDF at a particular momentum can be explained by noting the behaviour of the density of states (DoS) of the free system (without trap) in that particular dimension. The agreement between exact and LDA SIDFs becomes better with increase in dimensions and number of particles.

Simulation of Effective Thermal Conductivity of Metal Hydride Packed Beds

Several mathematical models are available for estimation of effective thermal conductivity of nonreactive packed beds. Keeping in view the salient differences between metal hydride beds in which chemisorption of hydrogen takes place and conventional nonreactive packed beds, modified models are proposed here to predict the effective thermal conductivity. Variation in properties such as solid thermal conductivity and porosity during hydrogen absorption and desorption processes are incorporated. These extended models have been applied to simulate the effective thermal conductivity of the MmNi(4.5)Al(0.5) hydride bed and are compared with the experimental results. Applicability of the extended models for estimation of the effective thermal conductivity at different operating conditions such as pressure, temperature, and hydrogen concentration is discussed.

Kernelization complexity of possible winner and coalitional manipulation problems in voting

In the POSSIBLE WINNER problem in computational social choice theory, we are given a set of partial preferences and the question is whether a distinguished candidate could be made winner by extending the partial preferences to linear preferences. Previous work has provided, for many common voting rules, fixed parameter tractable algorithms for the POSSIBLE WINNER problem, with number of candidates as the parameter. However, the corresponding kernelization question is still open and in fact, has been mentioned as a key research challenge 10]. In this paper, we settle this open question for many common voting rules. We show that the POSSIBLE WINNER problem for maximin, Copeland, Bucklin, ranked pairs, and a class of scoring rules that includes the Borda voting rule does not admit a polynomial kernel with the number of candidates as the parameter. We show however that the COALITIONAL MANIPULATION problem which is an important special case of the POSSIBLE WINNER problem does admit a polynomial kernel for maximin, Copeland, ranked pairs, and a class of scoring rules that includes the Borda voting rule, when the number of manipulators is polynomial in the number of candidates. A significant conclusion of our work is that the POSSIBLE WINNER problem is harder than the COALITIONAL MANIPULATION problem since the COALITIONAL MANIPULATION problem admits a polynomial kernel whereas the POSSIBLE WINNER problem does not admit a polynomial kernel. (C) 2015 Elsevier B.V. All rights reserved.