60,612 research outputs found

    Something in it for the underdog: the playwriting of Joan Ure

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    Modification of the one-dimensional REKAP program to allow for charring in three material layers Final report

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    Modified one-dimensional reaction kinetics program to allow for charring in three material layers of rocket nozzle throat insert cas

    Evidence for Circumburst Extinction of Gamma-Ray Bursts with Dark Optical Afterglows and Evidence for a Molecular Cloud Origin of Gamma-Ray Bursts

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    First, we show that the gamma-ray bursts with dark optical afterglows (DOAs) cannot be explained by a failure to image deeply enough quickly enough, and argue that circumburst extinction is the most likely solution. If so, many DOAs will be ``revived'' with rapid follow up and NIR searches in the HETE-2 and Swift eras. Next, we consider the effects of dust sublimation and fragmentation, and show that DOAs occur in clouds of size R > 10L_{49}^{1/2} pc and mass M > 3x10^5L_{49} M_{sun}, where L is the luminosity of the optical flash. Stability considerations show that such clouds cannot be diffuse, but must be molecular. Consequently, we compute the expected column density distribution of bursts that occur in Galactic-like molecular clouds, and show that the column density measurements from X-ray spectra of afterglows, DOAs and otherwise, satisfy this expectation in the source frame.Comment: Invited Review. To appear in Procs. of Gamma-Ray Burst and Afterglow Astronomy 2001: A Workshop Celebrating the First Year of the HETE Mission, 8 pages, 8 figures, LaTe

    What Students Tell Us About School If We Ask

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    This article examines what school climate factors students perceive as helping them be successful in school, and what school administrators can do to aid the process. Specifically, the questions that drove this inquiry were How does sociocultural theory impact student voice and student engagement in the classroom? How does caring pedagogy impact student voice and student engagement in the classroom? What school climate factors do students perceive as helping them to be successful in school

    IMPLICATIONS OF RAISING THE NONFAT SOLIDS STANDARDS FOR BEVERAGE MILK

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    An econometric model of the dairy industry was used to estimate the effects on farmers, consumers, and taxpayers of nationwide adoption of the California nonfat solids standards for fluid milk. It was estimated that adoption of the California standards would raise farm-level milk prices by 1 to 5 percent in the short run and by 1 to 2 percent in the long run. The average retail price of fluid milk would rise by 9 to 13 cents per gallon. Dairy program costs fall under most scenarios, but could rise if surpluses fall to levels that would trigger increases in the support price.Agricultural and Food Policy,

    Alaska Natives and American Laws

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    Voyager electronic parts radiation program, volume 1

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    The Voyager spacecraft is subject to radiation from external natural space, from radioisotope thermoelectric generators and heater units, and from the internal environment where penetrating electrons generate surface ionization effects in semiconductor devices. Methods for radiation hardening and tests for radiation sensitivity are described. Results of characterization testing and sample screening of over 200 semiconductor devices in a radiation environment are summarized

    Spitzer Observations of Gamma-Ray Burst Host Galaxies: A Unique Window into High Redshift Chemical Evolution and Star-formation

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    We present deep Spitzer 3.6 micron observations of three z~5 GRB host galaxies. Our observations reveal that z~5 GRB hosts are a factor of 3 less luminous than the median rest-frame V-band luminosity of spectroscopically confirmed z~5 galaxies in the GOODS fields and the UDF. The strong connection between GRBs and massive star formation implies that not all star-forming galaxies at these redshifts are currently being accounted for in deep surveys and GRBs provide a unique way to measure the contribution to the star-formation rate density from galaxies at the faint end of the galaxy luminosity function. By correlating the co-moving star-formation rate density with co-moving GRB rates at lower redshifts, we estimate a lower limit to the star-formation rate density of 0.12+/-0.09 and 0.09+/-0.05 M_sun/yr/Mpc^3 at z~4.5 and z~6, respectively. Finally, we provide evidence that the average metallicity of star-forming galaxies evolves as (stellar mass density)^(0.69+/-0.17) between z5z\sim5 and z0z\sim0, probably indicative of the loss of a significant fraction of metals to the intergalactic medium, particularly in low-mass galaxies.Comment: ApJ, in pres
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