Development of a parallel storm surge model

A new parallel storm surge model, the Parallel Environmental Model (PEM), is developed and tested by comparisons with analytic solutions. The PEM is a 2‐D vertically averaged, wetting and drying numerical model and can be operated in explicit, semi‐implicit and fully implicit modes. In the implicit mode, the propagation, Coriolis and bottom friction terms can all be treated implicitly. The advection and diffusion terms are solved with a parallel Eulerian–Lagrangian scheme developed for this study. The model is developed specifically for use on parallel computer systems and will function accordingly in either explicit of implicit modes. Storm boundary conditions are based on a simple exponential decay of pressure from the centre of a storm. The simulated flooding caused by a major Category 5 hurricane making landfall in the Indian River Lagoon, Florida is then presented as an example application of the PEM. Copyright © 2003 John Wiley & Sons, Ltd.     

Analysis of thermally induced multistable composites

This paper models the non-linear flexural response of laminates that have piecewise variation of lay-up in the planform, using finite element analysis. Attention is focused on the effects that thermal stresses have on the potential multiple shapes of a composite structure. Unsymmetric laminates may possess more than a single equilibrium configuration, and during the cool-down the solution thus bifurcates at a critical temperature. In static analyses, numerical solutions are often coaxed to converge into one or the other branch of the solution. A methodology to overcome this problem is presented. Such modelling is necessary to allow application of multistable composite within morphing aircraft structures as multistable composites could provide a viable solution for the realisation of shape-adaptable structures.     

Correlating second harmonic optical responses of single Ag nanoparticles with morphology

Femtosecond laser excited second harmonic (SH) activity from single Ag nanoparticles is reported. A correlation of SH single-particle measurements with high-resolution imaging of particle morphology by TEM was achieved by creating position markers on an optical and electron transparent substrate (Si3N4 thin film, approximately 100 nm). We compared the SH activity of single Ag nanoparticles (nanospheres versus nanorods) and cluster structures (composed of two or multiple particles, e.g., dimers and trimers). The direct correlation of single-particle structures and SH activity, spectral and power dependence, strongly suggests one-photon resonant driven nonlinear oscillator response mechanism.     

Double-layer effects on simple electrode reactions III. The reduction of Eu3+ and Cr3+ in the presence of thiocyanate anions. Evidence for ligand bridging

The rates of reduction of Eu³⁺ and Cr³⁺ have been measured in mixed perchlorate + thiocyanate electrolytes at constant ionic strength, using low concentrations of thiocyanate to minimize its association with the cationic reactants. The effect of adsorbed thiocyanate anions on the reduction kinetics of Cr³⁺ resembled those produced by iodide and bromide on both Cr³⁺ and Eu³⁺. However, thiocyanate exhibited an unusual catalytic effect on the reduction of Eu³⁺ which was identified as arising from a reaction pathway involving thiocyanate-bridging between the mercury surface and the Eu³⁺. The diagnostic criteria used to support the proposed mechanism included analysis of the rate—potential behavior and of the effects of competitively adsorbed iodide ions upon the reduction rates.     

The Dyeing of Nylon and Cotton Cloth with Azo Dyes: Kinetics and Mechanism

The mechanism of the dyeing of cotton and nylon cloth by the azo dyes Orange G and Sunset Yellow FCF was investigated using a channel flow cell. The variation in dyeing with flow rate was found to proceed via a mechanism in which the flux of dye entering the cloth relative to the flux of dye to the cloth surfacedecreasedwith increasing flow rate. A mechanism is deduced in which the dye passes from bulk solution, through a porous surface layer within the cloth, before passing into the bulk cloth. Adsorption onto surface sites in this porous layer blocks the passage of further dye into the cloth. Kinetic parameters for such a mechanism are given.     

Double-layer effects on simple electrode reactions II. The effects of specifically adsorbed anions and ion-pairing on the reduction of Eu3+ and Cr3+

The kinetics of the reduction of Eu³⁺ and Cr³⁺ at mercury electrodes have been studied in various mixed perchlorate electrolytes containing iodide, bromide, and p-toluene-sulfonate as adsorbing anions. Specific adsorption data were obtained by means of the constant ionic strength approach due to Hurwitz and Parsons. The rate enhancements observed in the presence of the first two (monatomic) anions were in good agreement with the predictions of the simple Frumkin model only when the experimental, rather than calculated diffuse-layer capacitances were employed in the data analysis. It was demonstrated that the effects of ion-pairing and ligand-bridging of the reactants with the adsorbing anions were negligible under the experimental conditions chosen. From experiments with these systems and also with weakly adsorbing chloride electrolytes it was concluded that ion-pairing did not enhance the electrochemical reactivity of either Eu³⁺ or Cr³⁺. The value of the analyses described in separating various contributions to the catalytic effects of adsorbing anions is emphasized.     

KINETIC BEHAVIOR OF EPR SIGNAL I: INDUCTION EFFECTS IN INTACT ALGAE

Abstract— There is considerable evidence that the light-induced narrow EPR signal I at g = 2·0025 in green algae is a reflection of the turnover of the photosynthetic reaction center, P700. A lag period or induction effect of the formation of this signal, subsequent to a dark period in whole fresh cells, is similar to induction effects for the bleaching of P700. The rate of formation of the signal is slower the longer the preceding dark period. DCMU does not much affect the induction phenomenon, but heating the cells to 60° abolishes it. Some substance or process which exists in the intact cell is altered by light and is detectable by its effect on signal I and on the rate of light-induced oxidation of P700 and cytochrome.     

Ketene-ketenimine rearrangements in the gas phase and in polar media. 1,3-Migration intermediates and sequential transition states

[reaction: see text] Calculations of the activation barrier for the 1,3-shifts of substituents X in alpha-imidoylketenes 1 (HN=C(X)-CH=C=O), which interconverts them with alpha-oxoketenimines 3 (HN=C=CH-C(X)=O) via a four-membered cyclic transition state TS2 have been performed at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31G* level. Substituents with accessible lone pairs have the lowest activation barriers for the 1,3-shift (halogens, OR, NR2). The corresponding activation barriers for the alpha-oxoketene-alpha-oxoketene rearrangement of 4 via TS5 are generally lower by 1-30 kJ/mol. A polar medium (acetonitrile, epsilon = 36.64) was simulated using the polarizable continuum (PCM) solvation model. The effect of the solvent field is a reduction of the activation barrier by an average of 12 kJ/mol. In the cases of 1,3-shifts of amino and dimethylamino groups, the stabilization of the transition state TS2 in a solvent field is so large that it becomes an intermediate, Int2, flanked by transition states (TS2' and TS2') that are due primarily to internal rotation of the amine functions, and secondarily to the 1,3-bonding interaction. In the case of the alpha-oxoketene-alpha-oxoketene rearrangement of 4, there is a corresponding intermediate Int5 for the 1,3-amine shift already in the gas phase.     

1,1,3,3-Tetramethylguanidine-gallane, (Me2N)2CN(H).GaH3: an unusually strongly bound gallane adduct

The novel adduct 1,1,3,3-tetramethylguanidine-gallane, (Me2N)2CN(H).GaH3, has been prepared by the reaction of [(Me2N)2CNH2]+Cl- with LiGaH4 in Et2O solution. Its spectroscopic properties indicate a monomeric species with an unusually strong coordinate link between the imido function and GaH3, an inference confirmed by the crystal structure at 150 K which also reveals significant secondary interactions through non-classical N-H...H-Ga bridges. Despite the intrinsic strength of the Ga-N bond, however, vaporisation at ca. 310 K occurs with partial dissociation, and decomposition via more than one pathway proceeds at temperatures >330-350 K to give a variety of products, including the free base, Me2NH, H2, and a novel gallium-nitrogen compound composed of a Ga4N4 cubane-like core bridged on three edges by -N{C(NMe2)2}GaH2- units.