The effect of annealing temperature and the characteristics of p-n junction diodes based on sprayed polyaniline/ZnO thin films

Polyaniline,ZnO and polyaniline/ZnO nanocomposite thin films are coated on glass substrates using the spray pyrolysis technique.The samples are characterized by the XRD,SEM,EDAX,UV-Vis and I-V characteristics. The XRD analyses confirm that the spray-coated polyaniline and ZnO thin films have orthorhombic and hexagonal structures,respectively,and optical bandgap energy decreases from 3.81 to 3.41 eV with the addition of a Zn atom.SEM analysis of the polyaniline/ZnO nanocomposite thin films shows that there is an agglomeration of ZnO particles with uniform distribution in the polyaniline matrix,and the diode characteristics of the polyaniline /ZnO nanocomposite show weak rectification behavior.Parameters such as the ideality factor,reverse saturation current and barrier height are calculated from the I-V characteristics.     

Hydrophobic distribution and spatial arrangement of amino acid residues in membrane proteins

The analysis of known three-dimensional structures of membrane proteins provides an opportunity to understand their structure and stability. In this article we analyse the hydrophobic variation of amino acid residues at various ranges in membrane and aqueous parts of membrane proteins. The numerical indices for several properties of amino acid residues in membrane proteins, such as surrounding hydrophobicity, gain in surrounding hydrophobicity, hydrophobic gain ratio, accessible surface area, preference of amino acid residues in the interior and surface parts, solvent accessible reduction ratio and buriedness, were set up. The relative preference of amino acid residues at various positions of membrane proteins were obtained in a very realistic approach.     

Synthesis of High-Performance Parallel Programs for a Class of ab Initio Quantum Chemistry Models

This paper provides an overview of a program synthesis system for a class of quantum chemistry computations. These computations are expressible as a set of tensor contractions and arise in electronic structure modeling. The input to the system is a a high-level specification of the computation, from which the system can synthesize high-performance parallel code tailored to the characteristics of the target architecture. Several components of the synthesis system are described, focusing on performance optimization issues that they address.     

Sequential and parallel implementations of the partitioningfinite-element method

With the computational capabilities of parallel computers, we should investigate new methods which have performance advantages on parallel computers even if they are not faster than conventional methods on sequential computers. One such method is the partitioning finite-element method (FEM). In this paper, we consider the implementation of the partitioning FEM on both the Gray Y-MP and the Intel Touchstone Delta. The partitioning method is shown to have many advantages over a traditional finite-element approach. On the Gray YMP and sequential computers, the partitioning method requires significantly less memory. For parallel processors such as the Intel Delta, we show that the partitioning FEM has a higher parallel efficiency than traditional FEM. EM scattering from an infinitely long dielectric cylinder is used as an example     

Layout transformation support for the disk resident arrays framework

The Global Arrays (GA) toolkit provides a shared-memory programming model in which data locality is explicitly managed by the programmer. It inter-operates with MPI and supports a variety of language bindings. The Disk Resident Arrays (DRA) model extends the GA programming model to secondary storage. GA and DRA together provide a convenient programming model that encourages locality-aware programming by the user, while presenting a high-level abstraction. High performance depends on the appropriate distribution of the data in the disk-resident arrays. In this paper, we discuss the addition of layout transformation support to DRA. The implementation of an efficient parallel layout transformation algorithm is done on top of existing GA/DRA functions; thus GA/DRA is itself used in implementing the enhanced DRA functionality. Experimental performance data is provided that demonstrates the effectiveness of the new layout transformation functionality. This work was supported in part through funding from the U.S. Department of Energy and the National Science Foundation (award 0121676).     

Enzymology and folding of natural and engineered bacterial beta-glucanases studied by X-ray crystallography

1,3-1,4-beta-D-glucan 4-glucanohydrolases (beta-glucanases) are synthesized in both plants and bacteria. The enzymes specifically hydrolyze beta-1,4 glycosyl bonds that are adjacent to beta-1,3 linkages in beta-glucan, a linear polysaccharide containing these bonds in an approximate ratio of 2.5:1. Here we review structural studies by X-ray crystallography of natural Bacillus beta-glucanases and engineered variants characterized by hybrid sequences, single-site mutations and circular permutations. In combination with biochemical data and site-directed mutagenesis, the crystallographic evidence permits the formulation of a likely reaction mechanism for the retaining Bacillus beta-glucanases. In addition, the shape of the active site channel, the known binding mode of a cellobioside epoxyalkyl inhibitor and the energy profile of the beta-glucan substrate explain the specificity of the enzymes for beta-glucan and the requirement for a beta-1,3 glycosyl bond next to the scissile bond. beta-Glucanases with circularly permuted sequences retain conformational stability, enzymatic activity and the native fold. The jellyroll tertiary structure of Bacillus beta-glucanases is remarkably stable, resisting changes in amino acid sequence, chain topology, ligand binding and crystal packing.     

Influence of molar concentration on the physical properties of nebulizer-sprayed ZnO thin films for ammonia gas sensor

Zinc oxide (ZnO) thin films were deposited by nebulizer spray pyrolysis technique with different molar concentrations of 0.05 M, 0.10 M and 0.15 M. The films were characterized by structural, morphological, electrical and optical properties. X-ray diffraction confirms that the all films are polycrystalline in nature with hexagonal crystal structure having preferential orientation along (002) plane and the maximum crystallite size is found to be ～77 nm. The band gap energy increases with molar concentration and reaches a maximum value of 3.2 eV at 0.15 M. Room temperature photoluminescence measurements were performed and band to band emission energies of ZnO films were determined. High resolution scanning electron microscopy shows the uniform distribution, densely packed grains with a plate like structure of ～55 nm (0.05 M).