The salvo combat model with a sequential exchange of fire

This paper develops a version of the stochastic salvo combat model in which the exchange of fire is sequential, rather than simultaneous. This sequential-fire version is built by modifying the equations in the original simultaneous-fire version. The performance of the sequential model is tested by comparing its outputs with those of a Monte Carlo simulation. The fit between the model and the simulation is very close, especially for the mean and standard deviation of losses. The model is then applied to the Battle of the Coral Sea. The results suggest that attacking first would have given the American force a larger advantage than that provided by an extra aircraft carrier.     

Explicit Betti numbers for a family of nilpotent Lie algebras

Betti numbers for the Heisenberg Lie algebras were calculated by Santharoubane in his 1983 paper. However few other examples have appeared in the literature. In this note we give the Betti numbers for a family of -dimensional 2-step nilpotent extensions of by .

     

Optical second harmonic generation studies of the nature of the GaAs(100) surface in air

We present in this paper a study of the non-linear optical response of the GaAs/air interface as measured by second harmonic generation. By careful choice of incidence and analysis electric vectors for the radiation the second harmonic response as a function of crystallographic orientation has been characterized for a GaAs(100) surface. The exact origin of the response remains unclear but comments on the surface specificity of the technique are made and the observed anisotropy in the data is explained in terms of the step density of the crystal surface.     

Considerations on HILIC and polar organic solvent-based separations: use of cyclodextrin and macrocyclic glycopetide stationary phases

There is a natural tendency in science to prefer straightforward, logical classification systems. The use of mobile phase-stationary phase combinations that do not fit neatly into the standard "normal phase" or "reversed-phase" categories has been going on for over 50 years. The term "hydrophilic interaction chromatography" (HILIC) is sometimes being used as a general category for these "other" separations. In some cases, it may be appropriate and in others, not. Indeed the mechanistic constrains used to define the method seem to be varying with time. Given the name HILIC, it is assumed that water is not only present in the mobile phase, but also plays an essential role in the retention mechanism. However, there is residual water present in all organic solvents. Regardless, the number of reported separations in this alternative mode has increased tremendously in the last two decades. This is due to the advent of new stationary phases and an emphasis on polar, biologically important molecules. We discuss the relationships between HILIC and other chromatographic modes. We then examine two classes of stationary phases that have played a major role in these separations. These particular stationary phases can be used to provide appreciable mechanistic information as well.     

Combined capillary electrophoresis and DNA-fluorescence in situ hybridization for rapid molecular identification of Salmonella Typhimurium in mixed culture

CE, long a staple in analytical chemistry for molecular separations, has recently been adapted for separating heterogeneous mixtures of microbial cells based on intrinsic differences in cell morphology and surface charge. In this application, CE enables effective separations of both relatively broad categories of cells, as well as of more similar cell types. As a phenotypic approach, CE may be less applicable to certain populations, including those comprised of pleiomorphic cells or chain-forming cells, where differences in cell size, shape, or chain length may lead to broad, "unfocusable" distributions in cell surface charge. At the other end of the spectrum, closely related species having similar surface charge profiles may not be separable via CE alone. Successful combination of microbial CE with a compatible method for generating cell-specific signals could address these limitations, increasing the diagnostic power of this approach. Fluorescence in situ hybridization (FISH) is a rapid molecular technique for fluorescence-based labeling of whole target cells. In this work, we combined a simple CE-based presence/absence test with FISH to develop a bacterial detection assay having an additional "layer" of molecular specificity. Using this approach, we were able to differentiate Salmonella Typhimurium from Escherichia coli in mixed populations via CE. Both hybridizations and CE run times were short (10-15 min), bacterial populations were highly focused ( approximately 2-3 s peak width) and there was no need for a posthybridization wash step. As few as three injected cells of S. Typhimurium were detected against a background of approximately 300 injected E. coli cells, suggesting the possibility for single-cell detection of pathogens using this technique. This proof of concept study highlights the potential of CE-FISH as a promising new tool for molecular detection of specific bacterial cells within mixtures of closely related, physiologically inseparable populations.     

Practical, scalable, high-throughput approaches to eta3-pyranyl and eta3-pyridinyl organometallic enantiomeric scaffolds using the Achmatowicz reaction

A unified strategy for the high-throughput synthesis of multigram quantities of the eta(3)-oxopyranyl- and eta(3)-oxopyridinylmolybdenum complexes TpMo(CO)(2)(eta(3)-oxopyranyl) and TpMo(CO)(2)(eta(3)-oxopyridinyl) is described (Tp = hydridotrispyrazolylborato). The strategy uses the oxa- and aza-Achmatowicz reaction for the preparation of these organometallic enantiomeric scaffolds, in both racemic and high enantiopurity versions.     

The difference a Se makes? Oxygen-tolerant hydrogen production by the [NiFeSe]-hydrogenase from Desulfomicrobium baculatum

Protein film voltammetry studies of the [NiFeSe]-hydrogenase from Desulfomicrobium baculatum show it to be a highly efficient H2 cycling catalyst. In the presence of 100% H2, the ratio of H2 production to H2 oxidation activity is higher than for any conventional [NiFe]-hydrogenases (lacking a selenocysteine ligand) that have been investigated to date. Although traces of O2 (< 1%) rapidly and completely remove H2 oxidation activity, the enzyme sustains partial activity for H2 production even in the presence of 1% O2 in the atmosphere. That H2 production should be partly allowed, whereas H2 oxidation is not, is explained because the inactive product of O2 attack is reductively reactivated very rapidly, but this requires a potential that is almost as negative as the thermodynamic potential for the 2H(+)/H2 couple. The study provides further encouragement and clues regarding the feasibility of microbial/enzymatic H2 production free from restrictions of anaerobicity.     

Enantioseparation of citalopram analogues with sulfated β‐cyclodextrin by capillary electrophoresis

Capillary electrophoresis methods were developed for the enantiomeric separation of 27 citalopram analogues. Sulfated β‐cyclodextrin was the most broadly selective and useful chiral selector. The separations of most of the citalopram analogue compounds reported in this work have not been reported previously. Excellent enantiomeric separations were obtained for 26 out of 27 compounds, and most of the separations were achieved within 10 min. The effects of chemical parameters such as chiral selector types, buffer types, chiral selector and buffer concentrations, buffer pH and organic modifiers on the separation were investigated. The influence of analyte structure on separation also was examined and discussed.