Autofocusing of through-the-wall radar imagery under unknown wall characteristics.

The quality and reliability of through-the-wall radar imagery is governed, among other things, by the knowledge of the wall characteristics. Ambiguities in wall characteristics smear and blur the image, and also shift the imaged target positions. An autotechnique, b ased on higher order statistics, i s presented which corrects for errors under unknown walls. Simulation results show that the proposed technique provides high-quality focused images with target locations in close proximity to true target positions.     

A sensitive ELISA for 6 beta-hydroxycortisol in urine using enzyme penicillinase (beta-lactamase)

A sensitive and specific, enzyme labelled immunosorbent assay (ELISA) for 6 beta-hydroxycortisol in diluted urine using penicillinase was developed. 6 beta-Hydroxycortisol-21-hemisuccinate was conjugated with enzyme penicillinase. Antibody immobilized on a polyvinylchloride ELISA plate (Dynatech) was used for separation of bound from free ligand. The sensitivity of the assay was between 2.0-3.0 pg per well and recovery of 6 beta-hydroxycortisol from urine ranged between 85.0-108.0%. The assay is simple, rapid and precise.     

Manganese-induced growth of GaAs nanowires

GaAs nanowires have been grown on SiO2 and GaAs by molecular beam epitaxy using manganese as growth catalyst. Transmission electron microscopy shows that the wires have a wurtzite-type lattice and that alpha-Mn particles are found at the free end of the wires. X-ray absorption fine structure measurements reveal the presence of a significant fraction of Mn-As bonds, suggesting Mn diffusion and incorporation during wire growth. Transport measurements indicate that the wires are p-type, as expected from doping of GaAs with Mn.     

Vertically aligned nanocomposite La0.8Sr0.2MnO3−δ/Zr0.92Y0.08O1.96 thin films as electrode/electrolyte interfacial layer for solid oxide reversible fuel cells

A thin layer with a vertically aligned nanocomposite (VAN) structure of La_0.8Sr_0.2MnO_3−δ (LSM) and Zr_0.92Y_0.08O_1.96 (YSZ) between the oxygen electrode and the electrolyte has been fabricated by a pulsed laser deposition (PLD) technique for solid oxide reversible fuel cells (SORFCs). The high quality epitaxial growth of VAN structured LSM/YSZ has been achieved on single crystal SrTiO₃ substrate at high-deposition temperatures. The symmetric cells with the VAN interlayer are found to have a lower area specific resistance compared to that without the interlayer. The enhancement in performance has been demonstrated by increased oxygen electrode catalytic properties and porous oxygen electrode microstructure. The cell with the VAN interlayer shows an open circuit voltage (OCV) of 1.00 V at 650 °C and maximum power densities of 0.22, 0.32, 0.43 and 0.55 W cm⁻² at 650, 700, 750 and 800 °C, respectively. Compared with the cell without an interlayer, the cells with the interlayer have ∼2 times of the overall maximum power density at the measured temperature range, demonstrating that the VAN interlayer significantly enhances the oxygen electrode performance.     

Contactless monitoring of the diameter-dependent conductivity of GaAs nanowires

Contactless monitoring with photoelectron microspectroscopy of the surface potential along individual nanostructures, created by the X-ray nanoprobe, opens exciting possibilities to examine quantitatively size- and surface-chemistry-effects on the electrical transport of semiconductor nanowires (NWs). Implementing this novel approach-which combines surface chemical microanalysis with conductivity measurements-we explored the dependence of the electrical properties of undoped GaAs NWs on the NW width, temperature and surface chemistry. By following the evolution of the Ga 3d and As 3d core level spectra, we measured the position-dependent surface potential along the GaAs NWs as a function of NW diameter, decreasing from 120 to ?20 nm, and correlated the observed decrease of the conductivity with the monotonic reduction in the NW diameter from 120 to ~20 nm. Exposure of the GaAs NWs to oxygen ambient leads to a decrease in their conductivity by up to a factor of 10, attributed to the significant decrease in the carrier density associated with the formation of an oxide shell. Open image in new window     

Biodegradation of chlorpyrifos and its hydrolysis product 3,5,6-trichloro-2-pyridinol by Bacillus pumilus strain C2A1

A bacterial strain C2A1 isolated from soil was found highly effective in degrading chlorpyrifos and its first hydrolysis metabolite 3,5,6-trichloro-2-pyridinol (TCP). On the basis of morphology, physiological characteristics, biochemical tests and 16S rRNA sequence analysis, strain C2A1 was identified as Bacillus pumilus. Role of strain C2A1 in the degradation of chlorpyrifos was examined under different culture conditions like pH, inoculum density, presence of added carbon/nutrient sources and pesticide concentration. Chlorpyrifos was utilized by strain C2A1 as the sole source of carbon and energy as well as it was co-metabolized in the presence of glucose, yeast extract and nutrient broth. Maximum pesticide degradation was observed at high pH (8.5) and high inoculum density when chlorpyrifos was used as the sole source and energy. In the presence of other nutrients, chlorpyrifos degradation was enhanced probably due to high growth on easily metabolizable compounds which in turn increased degradation. The strain C2A1 showed 90% degradation of TCP (300 mg L⁻¹) within 8 days of incubation.