60,704 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

    Alaska Natives and American Laws

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    Irradiate-anneal screening of total dose effects in semiconductor devices

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    An extensive investigation of irradiate-anneal (IRAN) screening against total dose radiation effects was carried out as part of a program to harden the Mariner Jupiter/Saturn 1977 (MJS'77) spacecraft to survive the Jupiter radiation belts. The method consists of irradiating semiconductor devices with Cobalt-60 to a suitable total dose under representative bias conditions and of separating the parts in the undesired tail of the distribution from the bulk of the parts by means of a predetermined acceptance limit. The acceptable devices are then restored close to their preirradiation condition by annealing them at an elevated temperature. IRAN was used when lot screen methods were impracticable due to lack of time, and when members of a lot showed a diversity of radiation response. The feasibility of the technique was determined by testing of a number of types of linear bipolar integrated circuits, analog switches, n-channel JFETS and bipolar transistors. Based on the results of these experiments a number of device types were selected for IRAN of flight parts in the MJS'77 spacecraft systems. The part types, screening doses, acceptance criteria, number of parts tested and rejected as well as the program steps are detailed

    Analytical and experimental study of reentrant stream crossed-field amplifiers Final report

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    Computer simulation and noise measurements of reentrant stream crossed-field amplifier

    IRREVERSIBLE INVESTMENT DECISIONS IN PERENNIAL CROPS WITH YIELD AND PRICE UNCERTAINTY

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    Optimal entry and exit thresholds for Georgia commercial peach production are calculated when both price and yield follow a Brownian motion process. The thresholds are based on an irreversible sunk-cost investment model, where revenue from peach production is affected by the timing of when to enter production. Results indicate stability in Georgia peach production, with growers who are currently producing peaches remaining in production and potential peach growers delaying investment unless they have the ability of earning enhanced returns.Crop Production/Industries,

    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,
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