8,212 research outputs found

    Lawyers and Judges by Joel Grossman

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    Tidal scattering of stars on supermassive black holes in galactic centers

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    Some of the mass that feeds the growth of a massive black hole (BH) in a galactic center is supplied by tidal disruption of stars that approach it on unbound, low angular momentum orbits. For each star that is disrupted, others narrowly escape after being subjected to extreme tidal distortion, spin-up, mixing and mass-loss, which may affect their evolution and appearance. We show that it is likely that a significant fraction of the stars around massive BHs in galactic centers have undergone such extreme tidal interactions and survived subsequent total disruption, either by being deflected off their orbit or by missing the BH due to its Brownian motion. We discuss possible long-term observable consequences of this process, which may be relevant for understanding the nature of stars in galactic centers, and may provide a signature of the existence of massive BHs there.Comment: 5 pages 4 figures. ApJL in press, minor changes to reflect journal version including redifinition of unbound tidally disturbed stars and additional reference

    Mindfulness as a moderator of coping response and the Abstinence Violation Effect : a test of the role of mindfulness in the Relapse Prevention Model for exercise.

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    The importance of physical activity in preventing disease and promoting health is increasingly evident in health outcomes research. Although most adults in the U.S. have initiated exercise programs at some point in their lives, research suggests that they have difficulty maintaining beneficial levels of physical activity and exercise. With escalating rates of obesity and physical inactivity, the importance of understanding processes by which individuals engage in and maintain physical activity cannot be understated. The Relapse Prevention Model (RPM), developed for use with addiction, has been successfully used to explore factors associated with exercise drop-out, or exercise relapse . In the current study, relationships between constructs of the RPM were examined and the role of mindfulness in moderating these relationships was evaluated using retrospective recall of exercise. In this cross-sectional study, static constructs were used as proxies for the situationally defined constructs of the RPM and the sequelae of high-risk situations for exercise lapse. Mindfulness was predicted to moderate the relationships between vulnerability to relapse and coping response, and between slip frequency and the Abstinence Violation Effect (AVE) in lapsers, such that individuals who were higher in mindfulness would endorse more effective coping strategies and lower AVE. The findings of this study suggest that mindfulness may be associated with better exercise outcomes, that less mindful community exercisers may use certain ineffective coping strategies more often, and that mindfulness may buffer the relationship between missed exercise sessions and the AVE. Future research on the role of mindfulness in exercise is recommended using prospective assessment methodologies and longitudinal design

    Telluric correction in the near-infrared: Standard star or synthetic transmission?

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    Context. The atmospheric absorption of the Earth is an important limiting factor for ground-based spectroscopic observations and the near-infrared and infrared regions are the most affected. Several software packages that produce a synthetic atmospheric transmission spectrum have been developed to correct for the telluric absorption; these are Molecfit, TelFit, and TAPAS. Aims. Our goal is to compare the correction achieved using these three telluric correction packages and the division by a telluric standard star. We want to evaluate the best method to correct near-infrared high-resolution spectra as well as the limitations of each software package and methodology. Methods. We applied the telluric correction methods to CRIRES archival data taken in the J and K bands. We explored how the achieved correction level varies depending on the atmospheric T-P profile used in the modelling, the depth of the atmospheric lines, and the molecules creating the absorption. Results. We found that the Molecfit and TelFit corrections lead to smaller residuals for the water lines. The standard star method corrects best the oxygen lines. The Molecfit package and the standard star method corrections result in global offsets always below 0.5% for all lines; the offset is similar with TelFit and TAPAS for the H2O lines and around 1% for the O2 lines. All methods and software packages result in a scatter between 3% and 7% inside the telluric lines. The use of a tailored atmospheric profile for the observatory leads to a scatter two times smaller, and the correction level improves with lower values of precipitable water vapour. Conclusions. The synthetic transmission methods lead to an improved correction compared to the standard star method for the water lines in the J band with no loss of telescope time, but the oxygen lines were better corrected by the standard star method.Comment: 18 pages, 13 figures, Accepted to A&
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