Electrical transport across Au/Nb:SrTiO3 Schottky interface with different Nb doping

We have investigated electron transport in Nb doped SrTiO$_3$ single crystals for two doping densities. We find that the resistivity and mobility are temperature dependent in both whereas the carrier concentration is almost temperature invariant. We rationalize this using the hydrogenic theory for shallow donors. Further, we probe electrical transport across Schottky interfaces of Au on TiO$_2$ terminated n-type SrTiO$_3$. Quantitative analysis of macroscopic I-V measurements reveal thermionic emission dominated transport for the low doped substrate whereas it deviates from such behavior for the high doped substrate. This work is relevant for designing devices to study electronic transport using oxide-semiconductors.Comment: 10 Pages, 3 Figure

A NuSTAR observation of the fast symbiotic nova V745 Sco in outburst

The fast recurrent nova V745 Sco was observed in the 3-79 keV X-rays band with NuSTAR 10 days after the optical discovery. The measured X-ray emission is consistent with a collisionally ionized optically thin plasma at temperature of about 2.7 keV. A prominent iron line observed at 6.7 keV does not require enhanced iron in the ejecta. We attribute the X-ray flux to shocked circumstellar material. No X-ray emission was observed at energies above 20 keV, and the flux in the 3-20 keV range was about 1.6 $\times$ 10$^{-11}$ erg cm$^{-2}$ s$^{-1}$. The emission measure indicates an average electron density of order of 10$^7$ cm$^{-3}$. The X-ray flux in the 0.3-10 keV band almost simultaneously measured with Swift was about 40 times larger, mainly due to the luminous central supersoft source emitting at energy below 1 keV. The fact that the NuSTAR spectrum cannot be fitted with a power law, and the lack of hard X-ray emission, allow us to rule out Comptonized gamma rays, and to place an upper limit of the order of 10$^{-11}$ erg cm$^{-2}$ s$^{-1}$ on the gamma-ray flux of the nova on the tenth day of the outburst.Comment: in press in Monthly Notices of the Royal Astronomical Society, 201

V1432 Aql: a polar or an intermediate polar?

We present evidence for a spin period of 4070 s in a magnetic cataclysmic variable V1432 Aql, classified as a polar. The evidence is based on the analysis of archival X-ray data obtained from a 25 ks long and uninterrupted observations with XMM-Newton. We also detect modulation of the X-ray flux with the orbital period, various harmonics of the spin period, and side-bands due to beating of the spin period with the orbital period. The energy-dependent light curves and hardness ratios show a very complex behaviour with both the spin phase and the orbital phase, indicating the presence of multiple absorbers of different densities. The observed characteristics suggest the presence of a disk in the system and accretion via a disk-overflow mechanism as is commonly observed in intermediate polars

Expression of genes related to Na⁺ exclusion and proline accumulation in tolerant and susceptible wheat genotypes under salt stress

In the present investigation, expression of genes related to Na+ exclusion such as salt overly sensitive (TaSOS1) and Na+/H+ antiporter (TaNHX1) and proline accumulation such as pyrroline-5-carboxylate reductase (P5CR) and glutamate synthase (GOGAT) was studied in seedlings of Kharchia 65 (Kh 65, salt tolerant) and HD 2009 (sensitive) under salt stress (ECe, 12 dSm–1) and controlled conditions. As compared to HD 2009, Kh 65 showed significantly lower accumulation of Na+ (p + exclusion in root and compartmentation in leaf and increased proline concentration are associated with tolerance to salinity stress in wheat. The information will be useful for improving wheat genotypes for salt tolerance

Phytochemical Screening of Methanolic Extract and Antibacterial Activity of Active Principles of Hepatoprotective Herb, Eclipta alba

Aerial parts of Eclipta alba are used traditionally for the treatment of several diseases of liver, skin and stomach. Methanolic extract and active principle compound of a well known Indian hepatoprotective herb, Eclipta alba was tested for in vitro antimicrobial studies. It was evaluated using zone of inhibition studies and minimum inhibitory concentration. The extract exhibited activity against all six strains studied. Phytochemical screening of the extract revealed the presence of tannins, flavonoids, coumestans, saponins and alkaloids etc. Ethylacetate fraction and further pure isolated wedelolactone showed enhanced antimicrobial activity. Staphylococcus epidermidis, Staphylococcus aureus and Salmonella typhimurium were most susceptible. Shigella flexneri was the most resistant bacterial strain. These results suggest coumestans/wedelolactone as a promising antimicrobial agent

Chandra High Resolution X-ray Spectroscopy of AM Her

We present the results of high resolution spectroscopy of the prototype polar AM Herculis observed with Chandra High Energy Transmission Grating. The X-ray spectrum contains hydrogen-like and helium-like lines of Fe, S, Si, Mg, Ne and O with several Fe L-shell emission lines. The forbidden lines in the spectrum are generally weak whereas the hydrogen-like lines are stronger suggesting that emission from a multi-temperature, collisionally ionized plasma dominates. The helium-like line flux ratios yield a plasma temperature of 2 MK and a plasma density 1 - 9 x10^12 cm^-3, whereas the line flux ratio of Fe XXVI to Fe XXV gives an ionization temperature of 12.4 +1.1 -1.4 keV. We present the differential emission measure distribution of AM Her whose shape is consistent with the volume emission measure obtained by multi-temperature APEC model. The multi-temperature plasma model fit to the average X-ray spectrum indicates the mass of the white dwarf to be ~1.15 M_sun. From phase resolved spectroscopy, we find the line centers of Mg XII, S XVI, resonance line of Fe XXV, and Fe XXVI emission modulated by a few hundred to 1000 km/s from the theoretically expected values indicating bulk motion of ionized matter in the accretion column of AM Her. The observed velocities of Fe XXVI ions are close to the expected shock velocity for a 0.6 M_sun white dwarf. The observed velocity modulation is consistent with that expected from a single pole accreting binary system.Comment: 6 figures, AASTEX style, accepted for publication in Ap

AC/DC conductivity and dielectric relaxation behavior of aqueous solutions of 1-butyl-3-methylimidazolium chloride

The complex relative dielectric function ɛ*(f) = ɛ' - jɛ" of aqueous solutions of 1-butyl-3-methylimidazolium chloride [BMiM][Cl] of varying concentrations, has been measured using precision LCR meter in the frequency range 20 Hz to 2 MHz at four different temperatures 293.15, 303.15, 313.15 and 323.15 K. Complex ac conductivity σ*(f) of the liquid samples have been determined from the measured ɛ*(f). DC conductivity σdc of the samples have also been determined. Values of σdc at different concentrations have been fitted to the empirical Casteel-Amis (CA) equation. The influence of concentration and temperature variation on the complex permittivity and electrical conductivity of the solutions of [BMiM][Cl] in distilled water has been discussed. The molar conductivities and the infinite dilution conductance of these ionic liquids have also been determined. Orientational relaxation behavior of the aqueous solutions of [BMiM][Cl] has also been studied by measuring complex permittivity in the frequency range 1 GHz to 20 GHz using vector network analyzer. Various processes contributed to the electrical/dielectric properties of the solutions of [BMiM][Cl] in distilled water have been explored