Thermally oxidized p-type Si [resistivity (5-10) Omega cm and < 1 0 0 > orientation] with oxide thickness of 245 nm was used as the substrate for the deposition of graphene by CVD. The formation of multilayer graphene (MLG) was confirmed by Raman spectroscopy. A heterojunction was fabricated by sol-gel coating of TiO2 on CVD grown graphene layer. The formation of titanium dioxide was verified by electron dispersion spectroscopy (EDS). The surfaces of TiO2, graphene as well as p-TiO2/n-graphene interface were characterized by scanning electron microscopy (SEM). Detail sensor study of the p-TiO2/n-graphene heterojunction was performed by taking two lateral catalytic metal (Pd) contacts deposited by e-beam evaporation. The response time of 16 s and the corresponding recovery time of 61 s were obtained for 0.5% H-2 in air at 125 degrees C. The p-TiO2/n-graphene junction showed selectivity for H-2 compared to methane. The stability study was performed and it showed almost the steady results over a period of 3 days as tested by the discrete measurements. The sensing mechanism was formulated using a simplified energy band diagram. (C) 2015 Elsevier B.V. All rights reserved.

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A crack detection technique based on nonlinear acoustics is investigated in this study. Acoustic waves at a chosen frequency are generated using an actuating lead zirconate titanate (PZT) transducer, and they travel through the target structure before being received by a sensing PZT wafer. Unlike an undamaged medium, a cracked medium exhibits high acoustic nonlinearity which is manifested as harmonics in the power spectrum of the received signal. Experimental results also indicate that the harmonic components increase nonlinearly in magnitude with increasing amplitude of the input signal. The proposed technique identifies the presence of cracks by looking at the two aforementioned features: harmonics and their nonlinear relationship to the input amplitude. The effectiveness of the technique has been tested on aluminum and steel specimens. The behavior of these nonlinear features as crack propagates in the steel beam has also been studied.

The Escherichia coli gene hflX was first identified as part of the hflA operon, mutations in which led to an increased frequency of lysogenization upon infection of the bacterium by the temperate coliphage lambda. Independent mutational studies have also indicated that the HflX protein has a role in transposition. Based on the sequence of its gene, HflX is predicted to be a GTP-binding protein, very likely a GTPase. We report here purification and characterization of the HflX protein. We also specifically examined its suggested functional roles mentioned above. Our results show that HflX is a monomeric protein with a high (30% to 40%) content of helices. It exhibits GTPase as well as ATPase activities, but it has no role in lambda lysogeny or in transposition.

Porous nature of silica gel samples comprising of micro- and meso-pores were studied with the help of positron annihilation lifetime spectroscopy based on a simple and realistic model which was further compared by nitrogen gas adsorption method namely Brunauer, Emmett and Teller isotherm. The final results illustrate the merits and fineness of the former, the extent of corroboration of the results and also the discrepancies accruing due to the limitations of the latter.

A new variety of heterocyclic polyamide membrane material has been studied for the micro-void size and its dominant associative features through positronium annihilation method, concomitantly its molecular characterization was confirmed through FTIR spectroscopy. A nonmonotonous temperature dependence of annihilation rate constant related to configurational energy changes have been discussed through the paradigm of activated process for positronium–molecular interaction, and a plausible explanation for the corresponding inhibition of positronium formation at the low temperature has been presented.