177,988 research outputs found

    Consent bias in research: how to avoid it

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    Maximum likelihood method for fitting the Fundamental Plane of the 6dF Galaxy Survey

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    We have used over 10,000 early-type galaxies from the 6dF Galaxy Survey (6dFGS) to construct the Fundamental Plane across the optical and near-infrared passbands. We demonstrate that a maximum likelihood fit to a multivariate Gaussian model for the distribution of galaxies in size, surface brightness and velocity dispersion can properly account for selection effects, censoring and observational errors, leading to precise and unbiased parameters for the Fundamental Plane and its intrinsic scatter. This method allows an accurate and robust determination of the dependencies of the Fundamental Plane on variations in the stellar populations and environment of early-type galaxies.Comment: 3 pages, 1 figure, to appear in the proceedings of the IAU Symposium 262 "Stellar Populations: Planning for the Next Decade", Charlot and Bruzual ed

    Occupational therapy students’ views of health promotion

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    With the increased interest in the contribution of occupational therapists to health promotion, the College of Occupational Therapists (2004a) recommended that pre-registration programmes should prepare graduates for practice which includes health promotion. This study ascertained the views of second year occupational therapy students about health promotion. Thirty five (30%) students responded to a self report questionnaire and demonstrated positive views about the future relationship between health promotion and occupational therapy. The students thought health promotion should be included in the education of occupational therapists and did not think that there had bee

    Spectral reflectivity of solid surfaces at low temperatures

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    Spectral reflectivity of solid surfaces at low temperature

    Acceleration Rates and Injection Efficiencies in Oblique Shocks

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    The rate at which particles are accelerated by the first-order Fermi mechanism in shocks depends on the angle, \teq{\Tbone}, that the upstream magnetic field makes with the shock normal. The greater the obliquity the greater the rate, and in quasi-perpendicular shocks rates can be hundreds of times higher than those seen in parallel shocks. In many circumstances pertaining to evolving shocks (\eg, supernova blast waves and interplanetary traveling shocks), high acceleration rates imply high maximum particle energies and obliquity effects may have important astrophysical consequences. However, as is demonstrated here, the efficiency for injecting thermal particles into the acceleration mechanism also depends strongly on obliquity and, in general, varies inversely with \teq{\Tbone}. The degree of turbulence and the resulting cross-field diffusion strongly influences both injection efficiency and acceleration rates. The test particle \mc simulation of shock acceleration used here assumes large-angle scattering, computes particle orbits exactly in shocked, laminar, non-relativistic flows, and calculates the injection efficiency as a function of obliquity, Mach number, and degree of turbulence. We find that turbulence must be quite strong for high Mach number, highly oblique shocks to inject significant numbers of thermal particles and that only modest gains in acceleration rates can be expected for strong oblique shocks over parallel ones if the only source of seed particles is the thermal background.Comment: 24 pages including 6 encapsulated figures, as a compressed, uuencoded, Postscript file. Accepted for publication in the Astrophysical Journa

    Perceiving infant faces

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    Evolutionary theories have long been used to generate testable predictions about responses to adult facial cues in the contexts of mate choice, cooperation, and intrasexual competition, among others. More recently, researchers have also used evolutionary theories to guide research on responses to infant facial cues. Here we review some of this work, focusing on research investigating hormonal regulation of responses to infant facial cuteness and the role of kinship cues in perceptions of infant faces. These studies suggest that sex hormones have dissociable effects on the reward value of and perceptual sensitivity to infant facial cuteness. They also suggest that attitudes and behavior toward infants displaying cues of kinship are complex processes influenced by individual differences
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