555 research outputs found

    The Dirac-Maxwell Equations with Cylindrical Symmetry

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    A reduction of the Dirac-Maxwell equations in the case of static cylindrical symmetry is performed. The behaviour of the resulting system of o.d.e.'s is examined analytically and numerical solutions presented. There are two classes of solutions. The first type of solution is a Dirac field surrounding a charged "wire". The Dirac field is highly localised, concentrated in cylindrical shells about the wire. A comparison with the usual linearized theory demonstrates that this localization is entirely due to the non-linearities in the equations which result from the inclusion of the "self-field". The second class of solutions have the electrostatic potential finite along the axis of symmetry but unbounded at large distances from the axis.Comment: 17 pages, Latex, 5 figures, psfig, to be published in J. Maths Phy

    Effects of solute concentrations on kinetic pathways in Ni-Al-Cr alloys

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    The kinetic pathways resulting from the formation of coherent L12-ordered y'-precipitates in the g-matrix (f.c.c.) of Ni-7.5 Al-8.5 Cr at.% and Ni-5.2 Al-14.2 Cr at.% alloys, aged at 873 K, are investigated by atom-probe tomography (APT) over a range of aging times from 1/6 to 1024 hours; these alloys have approximately the same volume fraction of the y'-precipitate phase. Quantification of the phase decomposition within the framework of classical nucleation theory reveals that the y-matrix solid-solution solute supersaturations of both alloys provide the chemical driving force, which acts as the primary determinant of the nucleation behavior. In the coarsening regime, the temporal evolution of the y'-precipitate average radii and the y-matrix supersaturations follow the predictions of classical coarsening models, while the temporal evolution of the y'-precipitate number densities of both alloys do not. APT results are compared to equilibrium calculations of the pertinent solvus lines determined by employing both Thermo-Calc and Grand-Canonical Monte Carlo simulation.Comment: Submitted to Acta Materialia, June, 200

    Promotion of Coalescence in Bicellar Mixtures by an SP-B Fragment

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    How Do Pharmacies Evaluate Cleanroom Automation Systems?

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    Many pharmacies have implemented or considered implementing cleanroom automation or compounding systems. Intravenous (IV) admixture automation is one of the newest areas of technology that has been applied to pharmacy workflow. Manufacturers tout systems for reducing errors reaching patients. Clinical literature supports that cleanroom technology can aid in patient safety
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