1,700 research outputs found

    Evaluation of high Reynolds number flow in a 180 degree turn-around-duct

    Get PDF
    Mean and turbulent velocities were measured for the flow in a 180 degree turn-around-duct over a Reynolds number range from 600,000 to greater than 900,000. The measurements were made in water using a forward scattering laser velocimeter. A duct of 100 x 10 cm constant cross-section, with a mean radius of curvature (centerline) of 10 cm was employed for the study. The measurements are in agreement with previous studies in that the use of local bulk velocity to nondimensionalize the mean and turbulent velocities reduce the Reynolds number variations. The basic phenomenon of relaminarization along the inner surface at the exit of the turn are similar to the flow observed at low Reynolds numbers. The separation bubble region shows a systematic variation with Reynolds number, however the Reynolds number effect may be of second order in the calculation of the overall flow. Large tangential, radial, and lateral turbulent velocities are measured along the outer surface of the turn

    Asian dust storm events of spring 2001 and associated pollutants observed in New England by the Atmospheric Investigation, Regional Modeling, Analysis and Prediction (AIRMAP) monitoring network

    Get PDF
    Between 18 April and 13 May 2001, three statistically extreme dust aerosol events were observed across the entire northeastern United States. High levels of bulk aerosol water-soluble Ca2+ (range = 42–482 pptv) and PM2.5 elemental Ca (range = 19–156 pptv) were observed simultaneously at Atmospheric Investigation, Regional Modeling, Analysis and Prediction (AIRMAP) and Interagency Monitoring of Protected Visual Environments (IMPROVE) stations. On the basis of Ca2+ concentrations, the average bulk dust concentration for all events across all four AIRMAP stations was estimated to be 7.4 μg/m3. There was no evidence of dust outbreaks in North America large enough to explain these events. However, in April 2001, massive dust storms occurred in the Tarim Pendi basin and in the Gobi deserts of southern Mongolia and China. Comparison of elemental ratios of AIRMAP samples to previously reported Asian dust aerosol samples showed that all AIRMAP samples had a chemical composition similar to Asian dust transported over long distances. Within the dust plumes, strong correlations were observed between absorption, scattering, and CO, indicative of an anthropogenic contribution including elemental carbon and SO42− aerosols. Aerosol NO3− was also highly elevated during event days, most likely due to uptake of HNO3 by the dust during transport. A comparison of dust plumes sampled by AIRMAP to those sampled off the Asian coast during the TRACE-P airborne mission and on the U.S. west coast, strongly suggested entrainment of additional pollutants (e.g., CO, aerosol NO3−, and SO42−) as the dust plumes were transported over North America

    Identification and Removal of Noise Modes in Kepler Photometry

    Full text link
    We present the Transiting Exoearth Robust Reduction Algorithm (TERRA) --- a novel framework for identifying and removing instrumental noise in Kepler photometry. We identify instrumental noise modes by finding common trends in a large ensemble of light curves drawn from the entire Kepler field of view. Strategically, these noise modes can be optimized to reveal transits having a specified range of timescales. For Kepler target stars of low photometric noise, TERRA produces ensemble-calibrated photometry having 33 ppm RMS scatter in 12-hour bins, rendering individual transits of earth-size planets around sun-like stars detectable as ~3 sigma signals.Comment: 18 pages, 7 figures, submitted to PAS

    The HARPS search for southern extra-solar planets. VI. A Neptune-mass planet around the nearby M dwarf Gl 581

    Full text link
    We report the discovery of a Neptune-mass planet around Gl 581 (M3V, M = 0.31 Msol), based on precise Doppler measurements with the HARPS spectrograph at La Silla Observatory. The radial velocities reveal a circular orbit of period P = 5.366 days and semi-amplitude K1 = 13.2 m/s. The resulting minimum mass of the planet (m2 sin i) is only 0.052 Mjup = 0.97 Mnep = 16.6 Mearth making Gl 581b one of the lightest extra-solar planet known to date. The Gl 581 planetary system is only the third centered on an M dwarf, joining the Gl 876 three-planet system and the lone planet around Gl 436. Its discovery reinforces the emerging tendency of such planets to be of low mass, and found at short orbital periods. The statistical properties of the planets orbiting M dwarfs do not seem to match a simple mass scaling of their counterparts around solar-type stars.Comment: letter submitted to A&

    The Ground on Which We All Stand: A Conversation About Menstrual Equity Law and Activism

    Get PDF
    This essay grows out of a panel discussion among five lawyers on the subject of menstrual equity activism. Each of the authors is a scholar, activist or organizer involved in some form of menstrual equity work. The overall project is both enriched and complicated by an intersectional analysis. This essay increases awareness of existing menstrual equity and menstrual justice work; it also identifies avenues for further inquiry, next steps for legal action, and opportunities that lie ahead. After describing prior and current work at the junction of law and menstruation, the contributors evaluate the successes and limitations of recent legal changes. The authors then turn to conceptual issues about the relationship between menstrual equity and gender justice, as well as the difference between equity and equality. The essay concludes with consideration of the future of menstrual equity and menstrual justice work. The authors envision an expanded, inclusive group of individuals working for greater gender justice

    Major Anthropogenic Causes for and Outcomes of Wild Animal Presentation to a Wildlife Clinic in East Tennessee, USA, 2000–2011

    Get PDF
    To determine the reasons for presentation and outcome of wildlife cases in East Tennessee, a retrospective analysis was performed using 14,303 records from cases presented to the wildlife clinic of the University of Tennessee Veterinary Teaching Hospital between 2000 and 2011. The cases were first categorized into amphibian/non-avian reptile, mammal, or avian and then classified into groups based on the primary admitting/presenting sign. There are a variety of reasons animals were presented to the clinic, and some were directly or indirectly anthropogenic in origin, including cat related, dog related, hit by automobile, and other human encounters leading to trauma; of the cases reviewed, 4,443 (31.1%) presented for one of these 4 reasons. Overall case fatality risk in regard to these 4 admitting/presenting signs was 0.519 for the amphibian/non-avian reptile cases, 0.675 for mammal cases, and 0.687 for avian cases. This study confirms the importance of monitoring wildlife morbidity and mortality and of focusing efforts to reduce the anthropogenic threat on native habitats and resident wildlife populations

    A Third Exoplanetary System with Misaligned Orbital and Stellar Spin Axes

    Get PDF
    We present evidence that the WASP-14 exoplanetary system has misaligned orbital and stellar-rotational axes, with an angle lambda = 33.1 +/- 7.4 deg between their sky projections. The evidence is based on spectroscopic observations of the Rossiter-McLaughlin effect as well as new photometric observations. WASP-14 is now the third system known to have a significant spin-orbit misalignment, and all three systems have "super-Jupiter" planets (M_P > 3 Mjup) and eccentric orbits. This finding suggests that the migration and subsequent orbital evolution of massive, eccentric exoplanets is somehow different from that of less massive close-in Jupiters, the majority of which have well-aligned orbits.Comment: 8 pages, 5 figures, 3 tables, PASP accepte
    • …
    corecore