Improved uniformity of target illumination by combining a lens array and the technique of spectral dispersion

A scheme using a lens array and the technique of spectral dispersion is presented to improve target illumination uniformity in laser produced plasmas. Detailed two-dimensional simulation shows that a quasi-near-field target pattern, of steeper edges and without side lobes, is achieved with a lens array, while interference stripes inside the pattern are smoothed out by the use of the spectral dispersion technique. Moving the target slightly from the exact focal plane of the principal focusing lens can eliminate middle-scale-length intensity fluctuation further. Numerical results indicate that a well-irradiated laser spot with small nonuniformity and great energy efficiency can be obtained in this scheme. (c) 2007 American Institute of Physics.

Identification of triosephosphate isomerase (TIM) genes from Microcystis (Cyanobacteria : Chroococcales) and theoretical analyses of the potential of cyanobacterial TIM as a target for designing specific inhibitors

The genes encoding triosephosphate isomerase (TIM) in three species of Microcystis (M. aeruginosa, M. viridis and M. wesenbergii) were investigated. Reverse transcriptase-polymerase chain reaction indicated that they were transcribed in the cells. Analyses showed that their DNA and deduced amino acid sequences were highly conserved between all the three species, only a single nonsynonymous substitution was seen at position 31, from an Asp in M. aeruginosa and M. viridis to Glu in M. wesenbergii. Sequence alignment of these with 12 other known cyanobacterial TIM sequences showed that all the cyanobacterial TIMs had a very high level of amino acid identity (over 50% between each two). Comparison of the cyanobacterial TIMs with other reported TIMs (from diverse lineages of the three Domains) showed that they possessed common active-site residues and sequence motifs. All cyanobacterial TIMs have two common cysteine residues (Cys127 and Cys176), and the Cys176 is almost cyanobacteria-specific with only one exception in Streptomyces coelicolor. Both secondary structure alignment and comparative modelling of Synechocystis sp. TIM showed that Cys176 was located at the hinge region of the flexible loop-6 and might therefore be critical to the movement of TIM's loop-6, which is important to the function of the enzyme. Thus, the cyanobacterial TIM-specific Cys176 may be a potential site for the discovery of suitable drugs against cyanobacteria, and such drugs may have utility in controlling water blooms due to cyanobacteria.

Insecticide resistance in Chinese populations of the Culex pipiens complex through esterase overproduction

In most parts of China, mosquitoes have been subjected to organophosphate (OP) insecticide treatments since the mid-1960s, and resistance gene monitoring in the Culex pipiens complex (Diptera: Culicidae) started in only a few locations from the end of the 1980s. Many resistant alleles at the Ester locus have been found in field populations, including those commonly found around the world (Ester(B1) and Ester(2)), and those endemic to China (Ester(B6), Ester(B7), Ester(8), and Ester(9)). This situation is atypical, and may represent a complex situation for the evolution of insecticide resistance genes in China. To increase our understanding of the Chinese situation and our ability to manage resistance in the C. pipiens complex, a large study was performed. Twenty field populations were sampled from Beijing to Guangzhou. Bioassays with five insecticides (dichlorvos, parathion, chlorpyrifos, 2-sec-butylphenyl methyl carbamate, and propoxur) disclosed resistance levels variable according to the geographic origin, and up to 85-fold for dichlorvos. Six overproduced esterases were identified, including two that have not been previously described. Most of them were found in all samples, although at variable frequencies, suggesting variable selection or a transient situation, e.g., each one was recently restricted to a particular geographic area. The results are discussed in the context of recent alterations to insecticide campaigns, and of the evolution of resistance genes in Chinese C. pipiens populations.

Structural and optical properties of ZnO thin films on glass substrate grown by laser-ablating Zn target in oxygen atmosphere

C-axis-orientated ZnO thin films were prepared on glass substrates by pulsed-laser deposition (PLD) technique in an oxygen-reactive atmosphere, using a metallic Zn target. The effects of growth condition such as laser energy and substrate temperature on the structural and optical properties of ZnO films had been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission spectra and room-temperature (RT) photoluminescence (PL) measurements. The results showed that the thickness, crystallite size, and compactness of ZnO films increased with the laser energy and substrate temperature. Both the absorption edges and the UV emission peaks of the films exhibited redshift, and UV emission intensity gradually increased as the laser energy and substrate temperature increased. From these results, it was concluded that crystalline quality of ZnO films was improved with increasing laser energy and substrate temperature. (c) 2007 Elsevier B.N. All rights reserved.

A novel vision chip for high-speed target tracking

This paper presents a novel vision chip for high-speed target tracking. Two concise algorithms for high-speed target tracking are developed. The algorithms include some basic operations that can be used to process the real-time image information during target tracking. The vision chip is implemented that is based on the algorithms and a row-parallel architecture. A prototype chip has 64 x 64 pixels is fabricated by 0.35 pm complementary metal-oxide-semiconductor transistor (CMOS) process with 4.5 x 2.5 mm(2) area. It operates at a rate of 1000 frames per second with 10 MHz chip main clock. The experiment results demonstrate that a high-speed target can be tracked in complex static background and a high-speed target among other high-speed objects can be tracked in clean background.

ZnO thin films on Si(111) grown by pulsed laser deposition from metallic Zn target

ZnO thin films with highly c-axis orientation have been fabricated on p-type Si(1 1 1) substrates at 400 degrees C by pulsed laser deposition (PLD) from a metallic Zn target with oxygen pressures between 0.1 and 0.7 mbar. Experimental results indicate that the films deposited at 0.3 and 0.5 mbar have better crystalline and optical quality and flatter surfaces than the films prepared at other pressures. The full width at half maximum (FWHM) of (0 0 0 2) diffraction peak decreases remarkably from 0.46 to 0.19 degrees with increasing annealing temperature for the film prepared at 0.3 mbar. In photoluminescence (PL) spectra at room temperature, the annealed film at 700 degrees C exhibits a smaller ultraviolet (UV) peak FWHM of 108 meV than the as-grown film (119 meV). However, an enhanced deep-level emission is observed. Possible origins to above results are discussed. (c) 2006 Elsevier B.V. All rights reserved.

Ground target detection, classification and sensor fusion in distributed fiber seismic sensor network - art. no. 683015

This paper describes the ground target detection, classification and sensor fusion problems in distributed fiber seismic sensor network. Compared with conventional piezoelectric seismic sensor used in UGS, fiber optic sensor has advantages of high sensitivity and resistance to electromagnetic disturbance. We have developed a fiber seismic sensor network for target detection and classification. However, ground target recognition based on seismic sensor is a very challenging problem because of the non-stationary characteristic of seismic signal and complicated real life application environment. To solve these difficulties, we study robust feature extraction and classification algorithms adapted to fiber sensor network. An united multi-feature (UMF) method is used. An adaptive threshold detection algorithm is proposed to minimize the false alarm rate. Three kinds of targets comprise personnel, wheeled vehicle and tracked vehicle are concerned in the system. The classification simulation result shows that the SVM classifier outperforms the GMM and BPNN. The sensor fusion method based on D-S evidence theory is discussed to fully utilize information of fiber sensor array and improve overall performance of the system. A field experiment is organized to test the performance of fiber sensor network and gather real signal of targets for classification testing.