8,372 research outputs found

    The Ulysses Supplement to the BATSE 4Br Catalog of Cosmic Gamma-Ray Bursts

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    We present Interplanetary Network localization information for 147 gamma-ray bursts observed by the Burst and Transient Source Experiment between the end of the 3rd BATSE catalog and the end of the 4th BATSE catalog, obtained by analyzing the arrival times of these bursts at the Ulysses and Compton Gamma-Ray Observatory (CGRO) spacecraft. For any given burst observed by these two spacecraft, arrival time analysis (or "triangulation") results in an annulus of possible arrival directions whose half-width varies between 7 arcseconds and 2.3 degrees, depending on the intensity and time history of the burst, and the distance of the Ulysses spacecraft from Earth. This annulus generally intersects the BATSE error circle, resulting in an average reduction of the error box area of a factor of 25.Comment: Accepted for publication in the Astrophysical Journal Supplemen

    Error Analysis for Reciprocating Compressor Performance

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    The Ulysses Supplement to the BATSE 3B Catalog of Cosmic Gamma-Ray Bursts

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    We present Interplanetary Network localization information for 218 gamma-ray bursts in the 3rd BATSE catalog, obtained by analyzing the arrival times of these bursts at the Ulysses and Compton Gamma-Ray Observatory (CGRO) spacecraft. For any given burst observed by these two spacecraft, arrival time analysis (or "triangulation") results in an annulus of possible arrival directions whose half-width varies between 7 arcseconds and 32 arcminutes, depending on the intensity and time history of the burst, and the distance of the Ulysses spacecraft from Earth. This annulus generally intersects the BATSE error circle, resulting in an average reduction of the error box area of a factor of 30.Comment: Accepted for publication in the Astrophysical Journal Supplemen

    Vacuum friction in rotating particles

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    We study the frictional torque acting on particles rotating in empty space. At zero temperature, vacuum friction transforms mechanical energy into light emission and produces particle heating. However, particle cooling relative to the environment occurs at finite temperatures and low rotation velocities. Radiation emission is boosted and its spectrum significantly departed from a hot-body emission profile as the velocity increases. Stopping times ranging from hours to billions of years are predicted for materials, particle sizes, and temperatures accessible to experiment. Implications for the behavior of cosmic dust are discussed.Comment: 4 figures, 10 pages, includes paper and supplementary information in the appendi

    Estimated refractive index and solid density of DT, with application to hollow-microsphere laser targets

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    The literature values for the 0.55-mumum refractive index N of liquid and gaseous Hsub2sub 2 and Dsub2sub 2 are combined to yield the equation (N - 1) = [(3.15 +- 0.12) x 10sup−6sup -6]rho, where rho is the density in moles per cubic meter. This equation can be extrapolated to 300sup0sup 0K for use on DT in solid, liquid, and gas phases. The equation is based on a review of solid-hydrogen densities measured in bulk and also by diffraction methods. By extrapolation, the estimated densities and 0.55-mumum refractive indices for DT are given. Radiation-induced point defects could possibly cause optical absorption and a resulting increased refractive index in solid DT and Tsub2sub 2. The effect of the DT refractive index in measuring glass and cryogenic DT laser targets is also described. (auth

    Evaluation of an online youth ambassador program to promote mental health

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    To evaluate an online Youth Ambassador (YA) program designed to promote internet resources for mental health in an adolescent population, 56 YAs and 357 of their Year 10 peers from 11 Tasmanian schools completed e-mental health questionnaires before and after the YAs attended a single workshop session. The workshops, which were delivered in the high school setting, were either facilitated or self-directed. Self-reported awareness of e-mental health resources increased among both YAs and their peers. The peer group also showed increased frequency of recommending help-seeking to others. There were no differences in outcomes for facilitated or self-directed workshop formats. The results suggest that an online YA program delivered in school is useful in improving mental health awareness for workshop participants. While their Year 10 peer groups also showed increased awareness, this could not necessarily be attributed to the participation of all 11 schools in the YA program

    The prevalence of MRI-defined spinal pathoanatomies and their association with Modic changes in individuals seeking care for low back pain

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    Modic changes are of increasing interest, however their age and gender prevalence are not well described. To date, the associations between Modic changes and other common vertebral pathologies have only been described in small samples (n < 100). Our aim was, in a large dataset of people with low back pain, to (1) describe the prevalence of a range of spinal pathoanatomies, and (2) examine the association between Modic changes and stages of intervertebral disc (IVD) pathology. Common pathologies were coded from the lumbar spine MRIs from 4,233 consecutive people imaged while attending a publicly-funded secondary care outpatient facility in Denmark. Prevalence data were calculated by pathology and by vertebral level. Prevalence was also calculated by age and gender categories for Modic changes. The association between stages of IVD pathology (degeneration, bulge, herniation) and Modic changes at L4/5 and L5/S1 was expressed using prevalence ratios (PR) and 95% confidence intervals. The prevalence of Modic changes and IVD pathology were greater in L4/5 and L5/S1, compared with the upper lumbar spine. There was no significant gender difference in prevalence of Modic changes (p = 0.11). The prevalence of IVD disc pathology occurring concurrently with Modic changes ranged from 11.5 to 17.5% (Type 1), 8.5 to 12.7% (Type 2) and 17.1 to 25.6% (Type 1 and/or 2) while the prevalence occurring in the absence of Modic changes ranged from 0.5 to 6.3% (Type 1), 0.3 to 4.9 (Type 2), 0.8 to 9.7% (Type 1 and/or 2). The associated PR for IVD pathology occurring concurrently with Modic changes ranged from 1.8 to 29.2 (p < 0.05). The highest PR (29.2) was between degeneration and Modic changes, indicating that it is rare for Modic changes to occur without disc degeneration.Spinal pathoanatomy was common in this population, particularly IVD pathologies, and a consistent trend of a relatively greater prevalence in the lower lumbar spine was identified. Modic changes were more likely to be present among individuals with IVD pathology than without, which may implicate mechanical factors as being one aetiological pathway for Modic changes, although other hypotheses may equally explain this association
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