27,256 research outputs found

    High-voltage pulse generator developed for wide-gap spark chambers

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    Low-inductance, high-capacitance Marx pulse generator provides for minimization of internal inductance and suppression of external electromagnetic radiation. The spark gaps of the generator are enclosed in a pressurized nitrogen atmosphere which allows the charging voltage to be varied by changing the nitrogen pressure

    Molecular orientation entanglement and temporal Bell-type inequalities

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    We detail and extend the results of [Milman {\it et al.}, Phys. Rev. Lett. {\bf 99}, 130405 (2007)] on Bell-type inequalities based on correlations between measurements of continuous observables performed on trapped molecular systems. We show that for some observables with a continuous spectrum which is bounded, one is able to construct non-locality tests sharing common properties with those for two-level systems. The specific observable studied here is molecular spatial orientation, and it can be experimentally measured for single molecules, as required in our protocol. We also provide some useful general properties of the derived inequalities and study their robustness to noise. Finally, we detail possible experimental scenarii and analyze the role played by different experimental parameters.Comment: 10 pages and 5 figure

    Focal plane transport assembly for the HEAO-B X-ray telescope

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    The High Energy Astronomy Observatory - Mission B (HEAO-B), an earth orbiting X-ray telescope facility capable of locating and imaging celestial X-ray sources within one second of arc in the celestial sphere, is considered. The Focal Plane Transport Assembly (FPTA) is one of the basic structural elements of the three thousand pound HEAO-B experiment payload. The FPTA is a multifunctional assembly which supports seven imaging X-ray detectors circumferentially about a central shaft and accurately positions any particular one into the focus of a high resolution mirror assembly. A drive system, position sensor, rotary coupler, and detent alignment system, all an integral part of the rotatable portion which in turn is supported by main bearings to the stationary focal plane housing are described

    Polymorphism of the tumor necrosis factor beta gene in systemic lupus erythematosus

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    We investigated the Nco I restriction fragment length polymorphism (RFLP) of the tumor necrosis factor beta (TNFB) gene in 173 patients with systemic lupus erythematosus (SLE), 192 unrelated healthy controls, and eleven panel families, all of German origin. The phenotype frequency of the TNFB*I allele was significantly increased in patients compared to controls (63.6% vs 47.1%, RR = 1.96, p <0.002). The results of a two-point haplotype statistical analysis between TNFB and HLA alleles show that there is linkage disequilibrium between TNFB*I and HLA-A1, Cw7, B8, DR3, DQ2, and C4A DE. The frequency of TNFB*I was compared in SLE patients and controls in the presence or absence of each of these alleles. TNFB*I is increased in patients over controls only in the presence of the mentioned alleles. Therefore, the whole haplotypeA1, Cw7, B8, TNFB* I, C4A DE, DR3, DQ2 is increased in patients and it cannot be determined which of the genes carried by this haplotype is responsible for the susceptibility to SLE. In addition, two-locus associations were analyzed in 192 unrelated healthy controls for TNFB and class I alleles typed by serology, and for TNFB and class II alleles typed by polymerase chain reaction/oligonucleotide probes. We found positive linkage disequilibrium between TNFB*I and the following alleles: HLA-A24, HLA-B8, DRBI*0301, DRBI*ll04, DRBI*1302, DQAI*0501, DQBI*0201, DQBI*0604, and DPBI*OIO1. TNFB*2 is associated with HLA-B7, DRBI*1501, and DQB I *0602

    Oxygen-isotope effect on the superconducting gap in the cuprate superconductor Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta}

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    The oxygen-isotope (^{16}O/^{18}O) effect (OIE) on the zero-temperature superconducting energy gap \Delta_0 was studied for a series of Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta} samples (0.0\leq x\leq0.45). The OIE on \Delta_0 was found to scale with the one on the superconducting transition temperature. These experimental results are in quantitative agreement with predictions from a polaronic model for cuprate high-temperature superconductors and rule out approaches based on purely electronic mechanisms.Comment: 5 pages, 3 figure

    Evolution from a molecular Rydberg gas to an ultracold plasma in a seeded supersonic expansion of NO

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    We report the spontaneous formation of a plasma from a gas of cold Rydberg molecules. Double-resonant laser excitation promotes nitric oxide, cooled to 1 K in a seeded supersonic molecular beam, to single Rydberg states extending as deep as 80 cm−1^{-1} below the lowest ionization threshold. The density of excited molecules in the illuminated volume is as high as 1 x 1013^{13} cm−3^{-3}. This population evolves to produce prompt free electrons and a durable cold plasma of electrons and intact NO+^{+} ions.Comment: 4 pages (two column) 3 figures; smaller figure files, corrected typo

    Iconography in Medieval Spanish Literature

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    The masterpieces of medieval Spanish literature have come to be known and loved by Hispanists, and more recently by others throughout the world. But the brilliant illuminations with which the original manuscripts were illustrated have remained almost totally unknown on the shelves of the great European libraries. To redress this woeful neglect, two noted scholars here present a generous selection from this great visual treasury including many examples never before reproduced. John E. Keller and Richard P. Kinkade have chosen five representative works, dating from the mid-thirteenth century to the late fifteenth, to illustrate the richness of early Spanish narrative art. Together, these five works encompass the entire range of narrative techniques and iconography to be found in medieval Spain, and reflect both foreign and native Spanish artistic tendencies. The authors’ analyses of the relation between verbalizations and visualizations will provide students of medieval art and literature a wealth of new information expanding our knowledge of this fascinating period. The beauty of many of the illuminations speaks for itself. John E. Keller is professor of Spanish at the University of Kentucky. Richard P. Kinkade is professor of Spanish and dean of humanities at the University of Arizona.https://uknowledge.uky.edu/upk_spanish_literature/1022/thumbnail.jp

    Insights into Regolith Dynamics from the Irradiation Record Preserved in Hayabusa Samples

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    The rates of space weathering processes are poorly constrained for asteroid surfaces, with recent estimates ranging over 5 orders of magnitude. The return of the first surface samples from a space-weathered asteroid by the Hayabusa mission and their laboratory analysis provides "ground truth" to anchor the timescales for space weathering. We determine the rates of space weathering on Itokawa by measuring solar flare track densities and the widths of solar wind damaged rims on grains. These measurements are made possible through novel focused ion beam (FIB) sample preparation methods
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