6,185 research outputs found

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    This is a semi-fictional story told through a series of fake found documents. It describes my work and thoughts through metaphor. Machines have the potential to gain self-consciousness through accumulation of errors. Creativity can be confused with randomly generated variety. The acceptance of chaos and loss of control can provide a path to enlightenment

    Generalized Ohm\u27s Law In A 3-D Reconnection Experiment

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    We report the measurement of non-ideal terms of the generalized Ohm\u27s law at a reconnection site of a weakly collisional laboratory magnetohydrodynamic plasma. Results show that the Hall term dominates the measured terms; resistive and electron inertia terms are small. We suggest that electron pressure (not measured) supports the observed quasistatic reconnection rate, and that anomalous resistivity, while not ruled out, is not required to account for the results

    Three-Dimensional Structure Of Magnetic Reconnection In A Laboratory Plasma

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    The local three-dimensional structure of magnetic reconnection has been measured for the first time in a magnetohydrodynamic (MHD) laboratory plasma at the Swarthmore Spheromak Experiment. An array of 600 magnetic probes which resolve ion inertial length and MHD time scale dynamics on a single shot basis measured the magnetic structure of partial spheromak merging events. Counter-helicity spheromaks merge rapidly, and reconnection activity clearly self-generates a local component of B which breaks the standard 2D symmetry at the ion inertial scale. Consistent with prior results, no reconnection is observed for co-helicity merging

    Evaluation of the microstructure of Al-Cu-Li-Ag-Mg Weldalite (tm) alloys, part 4

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    Weldalite (trademark) 049 is an Al-Cu-Li-Ag-Mg alloy designed to have ultrahigh strength and to serve in aerospace applications. The alloy displays significantly higher strength than competitive alloys in both naturally aged and artificially aged tempers. The strengthening phases in such tempers have been identified to, in part, explain the mechanical properties attained. In general, the alloy is strengthened by delta prime Al3Li and Guinier-Preston (GP) zones in the naturally aged tempers. In artificially aged tempers in slightly underaged conditions, strengthening is provided by several phases including GP zones, theta prime Al2Cu, S prime Al2CuMg, T(sub 1) Al2CuLi, and possibly a new phase. In the peak strength artificially aged tempers, T(sub 1) is the predominant strengthening phase

    Shear thickening in densely packed suspensions of spheres and rods confined to few layers

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    We investigate confined shear thickening suspensions for which the sample thickness is comparable to the particle dimensions. Rheometry measurements are presented for densely packed suspensions of spheres and rods with aspect ratios 6 and 9. By varying the suspension thickness in the direction of the shear gradient at constant shear rate, we find pronounced oscillations in the stress. These oscillations become stronger as the gap size is decreased, and the stress is minimized when the sample thickness becomes commensurate with an integer number of particle layers. Despite this confinement-induced effect, viscosity curves show shear thickening that retains bulk behavior down to samples as thin as two particle diameters for spheres, below which the suspension is jammed. Rods exhibit similar behavior commensurate with the particle width, but they show additional effects when the thickness is reduced below about a particle length as they are forced to align; the stress increases for decreasing gap size at fixed shear rate while the shear thickening regime gradually transitions to a Newtonian scaling regime. This weakening of shear thickening as an ordered configuration is approached contrasts with the strengthening of shear thickening when the packing fraction is increased in the disordered bulk limit, despite the fact that both types of confinement eventually lead to jamming.Comment: 21 pages, 14 figures. submitted to the Journal of Rheolog

    Experimental Observation Of Energetic Ions Accelerated By Three-Dimensional Magnetic Reconnection In A Laboratory Plasma

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    Magnetic reconnection is widely believed responsible for heating the solar corona as well as for generating X-rays and energetic particles in solar flares. On astrophysical scales, reconnection in the intergalactic plasma is a prime candidate for a local source (Mpc) of cosmic rays exceeding the Greisen-Zatsepin-Kuzmin cutoff (∼10(19) eV). In a laboratory astrophysics experiment, we have made the first observation of particles accelerated by magnetic reconnection events to energies significantly above both the thermal and the characteristic magnetohydrodynamic energies. These particles are correlated temporally and spatially with the formation of three-dimensional magnetic structures in the reconnection region

    Absorption of Nitrogen during Pulsed Wave L-PBF of 17-4 PH Steel

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    In the fabrication of 17-4 PH by laser powder bed fusion (L-PBF) the well-documented occurrence of large amounts of retained austenite can be attributed to an elevated concentration of nitrogen present in the material. While the effects of continuous wave (CW) laser processing on in-situ nitrogen absorption characteristics have been evaluated, power modulated pulsed wave (PW) laser processing effects have not. In this study the effects of PW L-PBF processing of 17-4 PH on nitrogen absorption, phase composition, and mechanical performance are explored using commercially available PW L-PBF equipment and compared to samples produced by CW L-PBF. PW L-PBF samples fabricated in cover gas conditions with varying amounts of nitrogen demonstrated reduced absorption levels compared to those produced by CW L-PBF with no effects on phase composition and minimal effects on mechanical performance

    rotl: an R package to interact with the Open Tree of Life data

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135519/1/mee312593_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135519/2/mee312593.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135519/3/mee312593-sup-0001-AppendixS1.pd

    Convergence on cooperation: the driving factors In U.S. and Russian cooperation on Belarus

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    RussiaBelarusOil PipelinesDemocratic RevolutionAs the last dictatorship in Europe, Belarus is a "problem state" for the United States. This thesis analyses U.S. interests in Belarus and assesses the extent of interdependence of these interests with Russian interests there. It first establishes a theoretical framework for U.S. and Russian national interests and the possibility for cooperation between the two countries. It then examines the mutuality of U.S and Russian interests in Belarus in the areas of democracy and human rights, drug and human trafficking, arms proliferation, oil and gas transit, and Russo-Belarusian trade and political integration and the policy options available to each country. Next, other elements of cooperation are applied to the situation in Belarus. Finally, the possibilities for cooperation are evaluated. This thesis demonstrates that the achievement of U.S. interests is significantly constrained by Russia's willingness to cooperate and that the United States can best achieve its objectives only through cooperation with Russia. This cooperation should center on neither country's first preference, but a compromise solution involving the ascendance of a moderate opponent to Lukashenka from within the Belarusian elite.http://archive.org/details/convergenceoncoo109452007Approved for public release; distribution is unlimited

    Liver Transplantation to Provide Low-Density-Lipoprotein Receptors and Lower Plasma Cholesterol in a Child with Homozygous Familial Hypercholesterolemia

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    A six-year-old girl with severe hypercholesterolemia and atherosclerosis had two defective genes at the low-density-lipoprotein (LDL) receptor locus, as determined by biochemical studies of cultured fibroblasts. One gene, inherited from the mother, produced no LDL receptors; the other gene, inherited from the father, produced a receptor precursor that was not transported to the cell surface and was unable to bind LDL. The patient degraded intravenously administered 125I-LDL at an extremely low rate, indicating that her high plasma LDL-cholesterol level was caused by defective receptor-mediated removal of LDL from plasma. After transplantation of a liver and a heart from a normal donor, the patient's plasma LDL-cholesterol level declined by 81 per cent, from 988 to 184 mg per deciliter. The fractional catabolic rate for intravenously administered 125I-LDL, a measure of functional LDL receptors in vivo, increased by 2.5-fold. Thus, the transplanted liver, with its normal complement of LDL receptors, was able to remove LDL cholesterol from plasma at a nearly normal rate. We conclude that a genetically determined deficiency of LDL receptors can be largely reversed by liver transplantation. These data underscore the importance of hepatic LDL receptors in controlling the plasma level of LDL cholesterol in human beings. (N Engl J Med 1984; 311: 1658–64.). © 1984, Massachusetts Medical Society. All rights reserved
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