High performance air pollution modeling for a power plant environment

The aim of this work is to provide a high performance air quality simulation using the STEM-II (Sulphur Transport Eulerian Model 2) program, a large-scale pollution modeling application. First, we optimize the sequential program with the aim of increasing data locality. Then, we parallelized the program using OpenMP directives for shared memory systems, and the MPI library for distributed memory machines. Performance results are presented for a SGI O2000 multiprocessor, a Fujitsu AP3000 multicomputer and a Cluster of PCs. Experimental results show that the parallel versions of the code achieve important reductions in the CPU time needed by each simulation. This will allow us to obtain results with adequate speed and reliability for the industrial environment where it is intended to be applied.     

Catalytic effects during cellulose liquefaction

Cellulose can be totally liquefied by heating to 350 °C in the presence of an aqueous phenolic solvent containing a catalyst. The main products are light aromatic hydrocarbons, benzofurans, heavier aromatic hydrocarbons such as substituted indanes and tetralin, and xanthenes. The variation of product distribution with catalyst was examined and it was found that in aqueous phenol, xanthene formation was enhanced by acidity. By substituting guaiacol for phenol, it was determined that most benzofuran formation involved the phenol solvent molecules, although a small proportion did not. This benzofuran may have arises from phenol generated from cellulose, the incorporation of phenol in the products being enhanced through a cage effect.     

Fish assemblages and stream hydraulics: consistent relations across spatial scales and regions

General relationships between organisms and their habitat, consistent across spatial scales and regions, suggest the existence of repeatable ecological processes and are useful for the management of stream networks. From published data, we defined four guilds of European fish species with contrasting preferences for microhabitat hydraulics within stream reaches. At the scale of stream reaches and across 139 French sites (590 460 fishes sampled), we analysed how fish guild proportions were related to reach hydraulics (proportion of pools vs. riffles %POOL; median discharge by unit width Q50/W). The strongest correlations were observed between two fish guilds and %POOL (p < 0.001, r² ≥ 0.41) and between one fish guild proportion and Q50/W (p < 0.001, r² = 0.10). These reach–scale relationships were consistent across six large French basins, and consistent with the analyses made at the microhabitat scale. Therefore, microhabitat preferences for hydraulics are strong enough to generate consistent reach‐scale community responses to hydraulics across regions, despite the influence of other filters such as temperature, nutrient levels or history. The distribution of basic geomorphic features (pools, riffles) in streams and their modification (by dams, weirs and dikes) can modify the proportion of fish guilds by up to 80%, probably contributing to the long‐term decline of riffle‐dwelling species in Europe. Copyright © 2006 John Wiley & Sons, Ltd.     

Uncertainty analysis based on sensitivity applied to angle-ply composite structures

This article describes a finite element-based formulation for the statistical analysis of the response of stochastic structural composite systems whose material properties are described by random fields. A first-order technique is used to obtain the second-order statistics for the structural response considering means and variances of the displacement and stress fields of plate or shell composite structures. Propagation of uncertainties depends on sensitivities taken as measurement of variation effects. The adjoint variable method is used to obtain the sensitivity matrix. This method is appropriated for composite structures due to the large number of random input parameters. Dominant effects on the stochastic characteristics are studied analyzing the influence of different random parameters. In particular, a study of the anisotropy influence on uncertainties propagation of angle-ply composites is carried out based on the proposed approach.     

Crystallization study of chemically vapour-deposited amorphous silicon films by in situ x-ray diffraction

The solid phase crystallization kinetics of chemically vapour-deposited amorphous silicon films were studied by in situ X-ray diffraction. We determined the crystalline volume directly from the Bragg peak intensities at various times during isothermal annealing in the temperature range 578 °C < T < 658 °C. From these experiments we deduced that the crystallization was due to nucleation predominantly at the substrate-film interface followed by crystal growth perpendicular to this interface. The crystal growth rate was thermally activated with an activation energy E_v of 3.1 eV. A strong 〈111〉 preferred orientation of the growing polycrystal was observed and the grain size remained constant at about 60 nm. Evidence of stresses at the amorphous-crystalline interface during the early stages of crystallization was observed. A comparison with previous conductivity measurements is also carried out.     

Water‐Stable,Magnetic Silica–Cobalt/Cobalt Oxide–Silica Multishell Submicrometer Spheres

A method to produce monodisperse magnetic composite spheres with diameters from less than 100 nm to more than 1 μm in water solution is reported. The spheres consist of a dielectric silica core and a cobalt/cobalt oxide shell which can be protected from further oxidation with an outer shell of silica or, alternatively, they can be covered with the polymer polyvinylpyrrolidone as a stabilizer. The formation of a uniform magnetic shell proceeds with the adsorption of metallic cobalt seeds, produced by the reduction of cobalt chloride with sodium borohydride, on a self‐assembled layer of polyelectrolytes on the silica core. In the second step, an outer silica shell can be formed by the hydrolysis and condensation of (3‐aminopropyl)trimethoxysilane and tetraethoxysilane. The double‐shell composite spheres show excellent sphericity, monodispersity, and a magnetic hysteresis loop at room temperature.     

Fast adders using enhanced multiple-output domino logic

Using an enhanced multiple output domino logic (EMODL) implementation of a carry lookahead adder (CLA), sums of several consecutive bits can be built in one nFET tree with a single carry-in. Based on this result, a new sparse carry chain architecture is proposed for the CLA adder. We demonstrate the design approach using a 32-b adder, and show that only four carries are sufficient for generating all sums, with a consequent reduction in the number of stage delays. Using a 1.2-μm CMOS technology, we verify our simulation procedures by fabrication and measurement of a 2.7 ns critical path     

Novel NMDA antagonists: replacement of the pyridinium ring of 6,11-ethanobenzo[b]quinolizinium cations with heteroisoquinolinium cations

Replacement of the pyridinium ring of 6,11-ethanobenzo[b]quinolizinium cations with thiazolium (4a and 4b) and N-methylimidazolium (4c and 4d) resulted in equipotent compounds in the [3H]TCP binding assay. The corresponding N-methyl-1,2,4-triazolium analogs were less potent in this assay. The thiazolium derivative 4b, with a Ki = 2.9 nM, is being evaluated as a possible neuroprotective N-methyl-D-aspartic acid (NMDA) antagonist.