11,076 research outputs found

    DEMAND THEORY: TIME ALLOCATION AND OUTDOOR RECREATION

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    Resource /Energy Economics and Policy,

    The V471 Tauri System: A Multi-datatype Probe

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    V471 Tauri, a white dwarf--red dwarf eclipsing binary in the Hyades, is well known for stimulating development of common envelope theory, whereby novae and other cataclysmic variables form from much wider binaries by catastrophic orbit shrinkage. Our evaluation of a recent imaging search that reported negative results for a much postulated third body shows that the object could have escaped detection or may have actually been seen. The balance of evidence continues to favor a brown dwarf companion about 12 AU from the eclipsing binary. A recently developed algorithm finds unified solutions from three datatypes. New radial velocities (RVs) of the red dwarf and BV RCIC light curves are solved simultaneously along with white dwarf and red dwarf RVs from the literature, uvby data, the MOST mission light curve, and 40 years of eclipse timings. Precision-based weighting is the key to proper information balance among the various datasets. Timewise variation of modeled starspots allows unified solution of multiple data eras. Light curve amplitudes strongly suggest decreasing spottedness from 1976 to about 1980, followed by approximately constant spot coverage from 1981 to 2005. An explanation is proposed for lack of noticeable variation in 1981 light curves, in terms of competition between spot and tidal variations. Photometric spectroscopic distance is estimated. The red dwarf mass comes out larger than normal for a K2V star, and even larger than adopted in several structure and evolution papers. An identified cause for this result is that much improved red dwarf RVs curves now exist

    Modulations in Multi-Periodic Blue Variables in the LMC

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    As shown by Mennickent, et al(2003), a subset of the blue variable stars in the Large Magellanic Cloud exhibit brightness variability of small amplitude in the period range 2.4 to 16 days as well as larger amplitude variability with periods of 140 to 600 days, with a remarkably tight relation between the long and the short periods. Our re-examination of these objects has led to the discovery of additional variability. The Fourier spectra of 11 of their 30 objects have 3 or 4 peaks above the noise level and a linear relation of the form f_a = 2(f_b - f_L) among three of the frequencies. An explanation of this relation requires an interplay between the binary motion and that of a third object. The two frequency relations together with the Fourier amplitude ratios pose a challenging modeling problem.Comment: 4 pages, 3 figures, Astrophysical Journal (in press

    Awareness of stroke warning signs, risk factors and response to stroke: a hospital based survey

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    Background: Stroke is the third most common cause of mortality and a significant cause of disability in India. Knowledge about stroke risk factors, warning signs and appropriate response to stroke are important to reduce the morbidity. Aim was to evaluate the awareness and response to stroke among the public. Methods: In this prospective, observational study, stroke awareness questioner was administered to 105 participants, who were relatives of patients without history of stroke attending the outpatient department of a tertiary care hospital. Results: The mean age of the study participants was 49.7±11.9 years (range 24-69years) with 46 (44%) women. Thirty six percent of the subjects recognized brain as the affected organ in stroke. The common risk factors identified by the participants were diabetes mellitus in 30 (28.6%), hypertension in 27 (25.7%), high cholesterol in 15 (14.3%). Commonly identified warning signs were paralysis of one side of the body (56; 53%), deviation of mouth (21; 20%), speech impairment (17; 16%). On having/seeing a warning sign, 27 (25.7%) replied the appropriate response of rushing to emergency department of a hospital. Eleven (10.5%) were aware of clot lysis as the treatment for stroke and 9 (8.7%) the availability of this treatment at free of cost in Government hospitals in Tamil Nadu. Five (4.8%) participants responded that they should rush to hospital within the golden hour. Conclusions: Knowledge about organ involved, etiology, and response to stroke warning signs are lacking and continuous education programs are necessary to improve the public awareness

    Fluorescence and Chromospheric Activity of V471 Tau

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    The red dwarf + white dwarf eclipsing binary V471 Tau shows a variable Hα feature that varies from absorption during eclipse to maximum emission during white dwarf transit. In 1998 we obtained simultaneous BVRI photometry and Hα spectroscopy, with thorough phase coverage of the 12.5 hour orbital period. A binary star model was used with our light curve, radial velocity, and Hα data to refine stellar and orbital parameters. Combined absorption-emission profiles were generated by the model and fit to the observations, yielding a red star radius of 0.94⊙. Orbital inclination 78° is required with this size and other known parameters. The model includes three spots 1,000 K cooler than the surrounding photosphere. The variable Hα profile was modeled as a chromospheric region (essentially on the surface of the red star) centered at the substellar point. Additional emission seen outside our modeled profiles may be large co-rotating prominences that complicate the picture

    Quarkonia in Hamiltonian Light-Front QCD

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    A constituent parton picture of hadrons with logarithmic confinement naturally arises in weak coupling light-front QCD. Confinement provides a mass gap that allows the constituent picture to emerge. The effective renormalized Hamiltonian is computed to O(g2){\cal O}(g^2), and used to study charmonium and bottomonium. Radial and angular excitations can be used to fix the coupling α\alpha, the quark mass MM, and the cutoff Λ\Lambda. The resultant hyperfine structure is very close to experiment.Comment: 9 pages, 1 latex figure included in the text. Published version (much more reader-friendly); corrected error in self-energ
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