80,986 research outputs found

    Semitoroidal diaphragm cavitating valve Patent

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    Semitoroidal diaphragm cavitating flow control valv

    High dispersion observations of Venus during 1972. The CO2 band at 7820 angstrom

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    Photographic plates of Venus which show the spectrum of the carbon dioxide band at 7820A were obtained at Table Mountain Observatory in September-October 1972. These spectra showed a semi-regular 4-day variation in the CO2 abundance over the disk of the planet. Evidence for temporal variations in the rotational temperature of this band and temperature variations over the disk was found. The two quantities, CO2 abundance and temperature, do not show any obvious relationship; however, an increase in the temperature usually is accompanied by a decrease in the abundance of CO2. The average temperature, found from a curve of growth analysis assuming a constant CO2 line of width, is 249 plus or minus 1.4 K (one standard deviation)

    Explosive Nucleosynthesis from GRB and Hypernova Progenitors: Direct Collapse versus Fallback

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    The collapsar engine behind long-duration gamma-ray bursts extracts the energy released from the rapid accretion of a collapsing star onto a stellar-massed black hole. In a collapsing star, this black hole can form in two ways: the direct collapse of the stellar core into a black hole and the delayed collapse of a black hole caused by fallback in a weak supernova explosion. In the case of a delayed-collapse black hole, the strong collapsar-driven explosion overtakes the weak supernova explosion before shock breakout, and it is very difficult to distinguish this black hole formation scenario from the direct collapse scenario. However, the delayed-collapse mechanism, with its double explosion, produces explosive nucleosynthetic yields that are very different from the direct collapse scenario. We present 1-dimensional studies of the nucleosynthetic yields from both black hole formation scenarios, deriving differences and trends in their nucleosynthetic yields.Comment: 47 pages, submitted to Ap

    Light Curve Calculations of Supernovae from Fallback Gamma-Ray Bursts

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    The currently-favored model for long-duration gamma-ray bursts (GRBs) invokes explosions from the collapse of a massive star down to a black hole: either directly or through fallback. Those GRBs forming via fallback will produce much less radioactive nickel, and hence it has been argued (without any real calculation) that these systems produce dim supernovae. These fallback black-hole GRBs have been recently been argued as possible progenitors of a newly discovered set of GRBs lacking any associated supernovae. Here we present the first ever radiation-hydrodynamics calculations of the light-curves produced in the hypernova explosion by a delayed-fallback gamma-ray burst. We find that the bolometric light-curve is dominated by shock-deposited energy, not the decay of radioactive elements. As such, observations of such bursts actually probe the density in the progenitor wind more than it does the production of radioactive nickel.Comment: 11 pages (including 3 figures), submitted to ApJ, comments welcom

    Defect energy of infinite-component vector spin glasses

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    We compute numerically the zero temperature defect energy, Delta E, of the vector spin glass in the limit of an infinite number of spin components m, for a range of dimensions 2 <= d <= 5. Fitting to Delta E ~ L^theta, where L is the system size, we obtain: theta = -1.54 (d=2), theta = -1.04 (d=3), theta = -0.67 (d=4) and theta = -0.37 (d=5). These results show that the lower critical dimension, d_l (the dimension where theta changes sign), is significantly higher for m=infinity than for finite m (where 2 < d_l < 3).Comment: 4 pages, 5 figure

    Non-invasive, multichromatic eye oximeter Final report

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    Optical eye oximeter for measuring oxygen of choroidal blood for monitoring brain oxygen suppl
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