2,322 research outputs found

    An experimental investigation of the flow field for double-wedge configurations in a Mach 4.97 stream

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    The viscous-inviscid interactions which perturb the flow around the wing leading edge are discussed. The flow field perturbation results when the fuselage-generated shock wave interacts with the wing-generated shock wave. Three types of shock interference patterns are possible for the wing leading edge of the orbiter

    Small carbon chains in circumstellar envelopes

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    Observations were made for a number of carbon-rich circumstellar envelopes using the Phoenix spectrograph on the Gemini South telescope to determine the abundance of small carbon chain molecules. Vibration-rotation lines of the ν3\nu_{3} antisymmetric stretch of C3_{3} near 2040 cm−1^{-1} (4.902 μ\mum) have been used to determine the column density for four carbon-rich circumstellar envelopes: CRL 865, CRL 1922, CRL 2023 and IRC +10216. We additionally calculate the column density of C5_{5} for IRC +10216, and provide an upper limit for 5 more objects. An upper limit estimate for the C7_{7} column density is also provided for IRC+10216. A comparison of these column densities suggest a revision to current circumstellar chemical models may be needed

    FORMS AND "TYPES" IN THE STUDY OF HUMAN BEHAVIOR: An Examination of the Generalizing Concepts of Mead and Schutz

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    http://web.ku.edu/~starjrn

    Fluorine in the solar neighborhood - is it all produced in AGB-stars?

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    The origin of 'cosmic' fluorine is uncertain, but there are three proposed production sites/mechanisms: AGB stars, ν\nu nucleosynthesis in Type II supernovae, and/or the winds of Wolf-Rayet stars. The relative importance of these production sites has not been established even for the solar neighborhood, leading to uncertainties in stellar evolution models of these stars as well as uncertainties in the chemical evolution models of stellar populations. We determine the fluorine and oxygen abundances in seven bright, nearby giants with well-determined stellar parameters. We use the 2.3 μ\mum vibrational-rotational HF line and explore a pure rotational HF line at 12.2 μ\mum. The latter has never been used before for an abundance analysis. To be able to do this we have calculated a line list for pure rotational HF lines. We find that the abundances derived from the two diagnostics agree. Our derived abundances are well reproduced by chemical evolution models only including fluorine production in AGB-stars and therefore we draw the conclusion that this might be the main production site of fluorine in the solar neighborhood. Furthermore, we highlight the advantages of using the 12 μ\mum HF lines to determine the possible contribution of the ν\nu-process to the fluorine budget at low metallicities where the difference between models including and excluding this process is dramatic

    The time variation in infrared water-vapour bands in Mira variables

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    The time variation in the water-vapour bands in oxygen-rich Mira variables has been investigated using multi-epoch ISO/SWS spectra of four Mira variables in the 2.5-4.0 micron region. All four stars show H2O bands in absorption around minimum in the visual light curve. At maximum, H2O emission features appear in the ~3.5-4.0 micronm region, while the features at shorter wavelengths remain in absorption. These H2O bands in the 2.5-4.0 micron region originate from the extended atmosphere. The analysis has been carried out with a disk shape, slab geometry model. The observed H2O bands are reproduced by two layers; a `hot' layer with an excitation temperature of 2000 K and a `cool' layer with an excitation temperature of 1000-1400 K. The radii of the `hot' layer (R_hot) are ~1 R_* at visual minimum and 2 R_* at maximum, where R_* is a radius of background source of the model. The time variation of R_hot/R_* from 1 to 2 is attributed to the actual variation in the radius of the H2O layer. A high H2O density shell occurs near the surface of the star around minimum, and moves out with the stellar pulsation. This shell gradually fades away after maximum, and a new high H2O density shell is formed in the inner region again at the next minimum. Due to large optical depth of H2O, the near-infrared variability is dominated by the H2O layer, and the L'-band flux correlates with the area of the H2O shell. The infrared molecular bands trace the structure of the extended atmosphere and impose appreciable effects on near-infrared light curve of Mira variables.Comment: 15 pages, 16 figures, accepted by A&

    How Environmental Litigation Has Turned Pipelines Into Pipe Dreams

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    Proposed oil and gas pipelines have faced a myriad of legal challenges in the past several years. Even where pipeline proponents have prevailed, the cost and delay of protracted litigation has often caused cancellation of pipeline projects. In addition, presidential transitions have led to abrupt reversals of pipeline policies, which courts have often reviewed skeptically. This Article explores the regulatory framework for pipeline construction and analyzes recent lawsuits, describing the legal requirements that agencies must follow to change policies and discussing policies of the Obama and Trump Administrations in context of the legal challenges. It concludes by analyzing the approaches taken by pipeline opponents and discussing implications for future projects
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