Enhancement in High-Field J c Properties and the Flux Pinning Mechanism of MgB2 Thin Films on Crystalline SiC Buffer Layers

We have studied the influence of crystalline SiC buffer layers on the critical current density and on the flux pinning mechanism in MgB₂ thin films. Crystalline SiC buffer layers were deposited on the Al₂O₃ (0001) substrates by using a pulsed laser deposition method, and then MgB₂ thin films were grown on the SiC-buffered layer by using a hybrid physical-chemical vapor deposition technique. MgB₂ thin films with crystalline SiC-buffered layers showed a significant critical current density’s enhancement in the high magnetic field region. An uncommon plateau-like behavior was also observed when the normalized flux pinning force density was scaled with the reduced magnetic field. Based on the analyses of the scaling behavior of the flux pinning force, grain boundary pinning is likely to be a dominant pinning mechanism in the SiC-buffered MgB₂ thin films.     

Development of Decibel Stepped Attenuator for Automated Sound Level Meter Calibration

MAPAN - Parameter testing in the sound level meter calibration, such as frequency weighting and linearity, needs precise adjustment of sound level in the decibel (dB) unit. In the...     

Reverse micelle facilitated synthesis of nanostructured polyaniline as the counter electrode materials in dye-sensitized solar cells

ABSTRACT

We report a reverse-micelle emulsion polymerization of nanostructured PANI using a nonionic surfactant Polyglyceryl-2-Dipolyhydroxystearate (PGPH) at various concentrations from 2% to 6% (v/v). SEM images show that the obtained morphologies are irregular agglomerates at low PGPH concentration and relatively regular granules at high PGPH concentration. FTIR and Raman spectra show that the synthesized PANI is in the form of Emeraldine salt (PANI ES) with electrical conductivity around 10^?3 S cm^?1. Photovoltaic current-voltage (J-V) measurements show the highest power conversion efficiency is achieved at 1.71% at 6% (v/v) of PGPH.     

A predictive model and mechanisms associated with hydrogen production via hydrothermal reactions of sulfide

Hydrogen generation and the concurrent formation of sulfur products from hydrothermal reactions of aqueous sulfide solutions at pH values between 9 and 13 and temperatures between 280 and 330 °C were studied. A hydrogen production model was developed by kinetic and statistical analysis of sulfide consumption rates and the ratio of hydrogen produced to sulfide consumed. Results showed that the amount of hydrogen generated in a given reaction may be predicted by a series of equations incorporating starting conditions such as the initial sulfide concentration, pH and temperature. The data from this study suggested that the overall hydrogen generation reaction mechanism consists of one or more elementary reactions which result in the formation of various sulfur products, such as polysulfides and sulfur oxyanions, depending on the reaction conditions. The possible specific sulfur compounds included pentasulfide (S₅²⁻), thiosulfate (S₂O₃²⁻), trithionate (S₃O₆²⁻) and sulfate (SO₄²⁻). The production rate constants of these products increased with temperature, but were independent of pH. Additionally, it was indicated that increasing the reaction temperature and/or pH resulted in the formation of sulfur products with higher oxidation numbers. This work suggests that the optimal mechanism for hydrogen generation via the sulfur redox cycle, taking into account the requirement for sulfide regeneration, is that which forms trithionate as the sole sulfur product.     

Synthesis and characterisation of chemical bath deposited TiO2 thin-films

A series of titania thin films was prepared by chemical bath deposition (CBD) of TiCl₃ on indium tin oxside (ITO) glass at room temperature, followed by calcinations at 500 °C for 4 h. The effect of cyclic deposition on phase composition, microstructure and electrical resistivity of TiO₂ thin films was characterised using X-ray diffraction, scanning electron microscopy and four-point probe respectively. Results showed that TiO₂ films produced by single deposition cycle were amorphous. In contrast, those produced by 5 and 6 deposition cycles were partly amorphous and partly crystalline with the formation of rutile. Both the film thickness and electrical resistivity increased with an increase in the number of deposition cycles.     

Choosing an Appropriate Infection Model to Study Quorum Sensing Inhibition in Pseudomonas Infections

Bacteria, although considered for decades to be antisocial organisms whose sole purpose is to find nutrients and multiply are, in fact, highly communicative organisms. Referred to as quorum sensing, cell-to-cell communication mechanisms have been adopted by bacteria in order to co-ordinate their gene expression. By behaving as a community rather than as individuals, bacteria can simultaneously switch on their virulence factor production and establish successful infections in eukaryotes. Understanding pathogen-host interactions requires the use of infection models. As the use of rodents is limited, for ethical considerations and the high costs associated with their use, alternative models based on invertebrates have been developed. Invertebrate models have the benefits of low handling costs, limited space requirements and rapid generation of results. This review presents examples of such models available for studying the pathogenicity of the Gram-negative bacterium Pseudomonas aeruginosa. Quorum sensing interference, known as quorum quenching, suggests a promising disease-control strategy since quorum-quenching mechanisms appear to play important roles in microbe-microbe and host-pathogen interactions. Examples of natural and synthetic quorum sensing inhibitors and their potential as antimicrobials in Pseudomonas-related infections are discussed in the second part of this review.