2,228 research outputs found

    Overview of the Systems Special Investigation Group investigation

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    The Long Duration Exposure Facility (LDEF) carried a remarkable variety of electrical, mechanical, thermal, and optical systems, subsystems, and components. Nineteen of the fifty-seven experiments flown on LDEF contained functional systems that were active on-orbit. Almost all of the other experiments possessed at least a few specific components of interest to the Systems Special Investigation Group (Systems SIG), such as adhesives, seals, fasteners, optical components, and thermal blankets. Almost all top level functional testing of the active LDEF and experiment systems has been completed. Failure analysis of both LDEF hardware and individual experiments that failed to perform as designed has also been completed. Testing of system components and experimenter hardware of interest to the Systems SIG is ongoing. All available testing and analysis results were collected and integrated by the Systems SIG. An overview of our findings is provided. An LDEF Optical Experiment Database containing information for all 29 optical related experiments is also discussed

    Cultural Resource Survey Of Proposed Expansion Areas For The Kerrville City Landfill And Limited Testing Of Site 41KR501, Kerrville, Kerr County, Texas

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    In April of 2015, AmaTerra Environmental, Inc. staff conducted intensive cultural resource investigations of approximately 78 acres of proposed expansions to the City of Kerrvilleā€™s existing Kerrville Landfill in Kerr County, Texas. Working on behalf of the City of Kerrville (the land owner and project sponsor) and their design consultant LNV, Inc., AmaTerra investigated portions of the Landfillā€™s proposed Western Expansion Area (36.5 acres) and the Big Hill Expansion Area (41.5 acres) for compliance with Section 106 of the National Historic Preservation Act of 1966 (as amended) and the Antiquities Code of Texas (Antiquities Permit 7238). Within undisturbed and previously-unsurveyed portions of the Big Hill Expansion Area, archeologists conducted intensive area survey and excavated 17 subsurface shovel tests, finding the expansion area composed of shallow, deflated, upland soils. Previously recorded Site 41KR673, a diffuse prehistoric surface scatter of non-diagnostic tools and lithic debris was expanded to encompass approximately 15 acres of the Big Hill Expansion Area. The proposed Western Expansion Area was surveyed previously, hence, archeologists focused on intensive survey and limited NRHP/SAL-eligibility testing of a previously recorded prehistoric site, Site 41KR501. Nine backhoe trenches were excavated within the site area. These yielded seven flakes and three burned rock fragments in three of the trenches. All of the artifacts were found within secondary, high-energy, flood-related contexts (or subsurface disturbance) ranging from 70 to 210 centimeters below the surface. A small surface scatter of burned rock was also observed near the siteā€™s southern boundary. No evidence of intact features was observed. Given the lack of temporal diagnostics, very minimal artifacts, and the resulting poor level of research potential, Sites 41KR501 and 41KR673 are recommended as not eligible for listing in the National Register of Historic Places or as a State Antiquities Landmarks. Accordingly, AmaTerra recommends that the project proceed with no adverse effects to Historic Properties and/or State Antiquities Landmarks and no further work necessary. No artifacts were collected during the survey but all field-generated notes, forms, and photographs will be permanently curated at the Texas Archeological Research Laboratory in Austin

    Space environmental effects observed on the Hubble Space Telescope

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    The Hubble Space Telescope (HST) Repair Mission of December, 1993, was first and foremost a mission to improve the performance of the observatory. But for a specialized segment of the aerospace industry, the primary interest is in the return to Earth of numerous pieces of the HST hardware, pieces which have been replaced, repaired, improved, or superseded. The returned hardware is of interest because of the information it potentially carries about the effects of exposure to the space environment for three and a half years. Like the LDEF retrieval mission four years ago, the HST repair mission is of interest to many engineering disciplines, including all of the disciplines represented by the LDEF Special Investigation Groups (SIG's). There is particular interest in the evaluation of specific materials and systems in the returned components. Some coated surfaces have been processed with materials which are newer and still in use by, or under consideration for, other spacecraft in a variety of stages of development. Several of the systems are being returned because a specific failure or anomaly has been observed and thus there is, at the outset, a specific investigative trail that needs to be followed. These systems are much more complex than those flown on LDEF and, in two instances, comprised state-of-the-art science instruments. Further, the parts used in these systems generally were characterized more rigorously prior to flight than were those in the LDEF systems, and thus post flight testing may yield more significant results

    Probing spectral and timing properties of the X-ray pulsar RX J0440.9+4431 in the giant outburst of 2022-2023

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    The X-ray pulsar RX J0440.9+4431 went through a giant outburst in 2022 and reached a record-high flux of 2.3 Crab, as observed by Swift/BAT. We study the evolution of different spectral and timing properties of the source using NICER observations. The pulse period is found to decrease from 208 s to 205 s, and the pulse profile evolves significantly with energy and luminosity. The hardness ratio and hardness intensity diagram (HID) show remarkable evolution during the outburst. The HID turns towards the diagonal branch from the horizontal branch above a transition (critical) luminosity, suggesting the presence of two accretion modes. Each NICER spectrum can be described using a cutoff power law with a blackbody component and a Gaussian at 6.4 keV. At higher luminosities, an additional Gaussian at 6.67 keV is used. The observed photon index shows negative and positive correlations with X-ray flux below and above the critical luminosity, respectively. The evolution of spectral and timing parameters suggests a possible change in the emission mechanism and beaming pattern of the pulsar depending on the spectral transition to sub- and super-critical accretion regimes. Based on the critical luminosity, the magnetic field of the neutron star can be estimated in the order of 1012^{12} or 1013^{13} G, assuming different theoretical models. Moreover, the observed iron emission line evolves from a narrow to a broad feature with luminosity. Two emission lines originating from neutral and highly ionized Fe atoms were evident in the spectra around 6.4 keV and 6.67 keV (higher luminosities).Comment: Published in Monthly Notices of the Royal Astronomical Societ

    The Decline in Vitamin Research Funding:A Missed Opportunity?

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    Background: The National Nutrition Research Roadmap has called for support of greater collaborative, interdisciplinary research for multiple areas of nutrition research. However, a substantial reduction in federal funding makes responding to these calls challenging. Objectives: The objectives of this study were to examine temporal trends in research funding and to discuss the potential consequences of these trends. Methods: We searched the NIH RePORTER database to identify NIH research grants and USASpending to identify National Science Foundation and USDA research grants awarded from 1992 to 2015. We focused on those that pertained to vitamin research. For the years 2000 to 2015, we examined funding trends for different vitamins, including vitamins A, B (one-carbon B-vitamins were considered separately from other B-vitamins), C, D, E, and K. Results: From 1992 to 2015, total federal research spending increased from similar to14to14 to 45 billion (2016 US dollars). Although vitamin research spending increased from similar to89to89 to 95 million, the proportion of grants awarded for vitamin research declined by more than two-thirds, from 0.65% in 1992 to 0.2% in 2015. Federal agencies awarded 6035 vitamin research grants over the time period, with vitamin A associated with the most research projects per year on average (n = 115) and vitamin K the fewest (n = 8). Vitamin D research projects were associated with the greatest average yearly project value ($34.8 million). Conclusions: Vitamin research has faced a disproportionate decline in research funding from 1992 to 2015. Insufficient federal research funding streams risk stalling progress in vitamin research and leaving important advancements unrealized
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