7,370 research outputs found

    Descriptions of reversed yielding in bending

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    Existence of Bauschinger effect in bending-unbending of copper beams has been shown from experiment. In modelling of the Bauschinger effect, it is shown that a significant second plastic penetration can occur with the release of the moment required for an elasticplastic bending of a beam. The theory is given for both linear and parabolic hardening material models. The elastic and plastic strains are developed from each hardening model to express the beam curvature of the unstressed neutral axis. Conditions are expressed, using the normalized stress—strain response of a rectangular beam section, for which the release is purely elastic and elastic—plastic. Under the latter the depth to which a second zone of plasticity penetrates is given. Two stress distributions: one for applying the moment and the other for its release, are sufficient to derive the residual stress. Residuals found for parabolic hardening are believed to be more realistic than those from simpler linear or perfectly plastic models, particularly, where a second penetration is evident

    Collector Failures on 350 MHz, 1.2 MW CW Klystrons at the Low Energy Demonstration Accelerator (LEDA)

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    We are currently operating the front end of the accelerator production of tritium (APT) accelerator, a 7 MeV radio frequency quadrapole (RFQ) using three, 1.2 MW CW klystrons. These klystrons are required and designed to dissipate the full beam power in the collector. The klystrons have less than 1500 operational hours. One collector has failed and all collectors are damaged. This paper will discuss the damage and the difficulties in diagnosing the cause. The collector did not critically fail. Tube operation was still possible and the klystron operated up to 70% of full beam power with excellent vacuum. The indication that finally led us to the collector failure was variable emission. This information will be discussed. A hydrophonic system was implemented to diagnose collector heating. The collectors are designed to allow for mixed-phase cooling and with the hydrophonic test equipment we are able to observe: normal, single-phase cooling, mixed-phase cooling, and a hard boil. These data will be presented. The worst case beam profile from a collector heating standpoint is presented. The paper will also discuss the steps taken to halt the collector damage on the remaining 350 MHz klystrons and design changes that are being implemented to correct the problem.Comment: LINAC2000 conference paper THE1

    A model of the quasi-stellar radio variable CTA 102

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    Model of quasi-stellar radio source CTA 102 - flux density and red shift observation

    A study of the hexose transport in the rat adipocyte.

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    Hallelujahs From Portsmouth Campmeeting

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    https://place.asburyseminary.edu/firstfruitsheritagematerial/1126/thumbnail.jp

    Binding of ligands to the active site of carboxypeptidase A.

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    Flash-Heating of Circumstellar Clouds by Gamma Ray Bursts

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    The blast-wave model for gamma-ray bursts (GRBs) has been called into question by observations of spectra from GRBs that are harder than can be produced through optically thin synchrotron emission. If GRBs originate from the collapse of massive stars, then circumstellar clouds near burst sources will be illuminated by intense gamma radiation, and the electrons in these clouds will be rapidly scattered to energies as large as several hundred keV. Low-energy photons that subsequently pass through the hot plasma will be scattered to higher energies, hardening the intrisic spectrum. This effect resolves the "line-of-death" objection to the synchrotron shock model. Illuminated clouds near GRBs will form relativistic plasmas containing large numbers of electron-positron pairs that can be detected within ~ 1-2 days of the explosion before expanding and dissipating. Localized regions of pair annihilation radiation in the Galaxy would reveal past GRB explosions.Comment: 9 pages, 1 figure, submitted to ApJ Letter

    Human Myeloma Marrow Cells in Immunologically Deficient Mice

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    Intact human bone marrow cells from 7 patients with myelomatosis were inoculated intravenously into adolescent CBA mice rendered immunologically deficient by thymectomy followed by total body irradiation (600 rad). Each inoculum of human myeloma marrow cells and subsequent passages of intact mouse marrow and spleen cells resulted in the presence of morphological changes in the marrow, spleen and peripheral blood of a proportion of these mice which were closely similar to those seen in the human donor. A substantial amount of human immunoglobulin (IgG and IgA) was detected in the sera of some of the mice showing morphological changes. Mice prepared identically but remaining uninoculated or receiving intact human bone marrow cells from 3 patients with no evidence of haematological malignancy showed none of these changes when examined after similar intervals
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