6,268 research outputs found
Confirming Fundamental Parameters of the Exoplanet Host Star epsilon Eridani Using the Navy Optical Interferometer
We measured the angular diameter of the exoplanet host star epsilon Eridani
using the Navy Optical Interferometer. We determined its physical radius,
effective temperature, and mass by combining our measurement with the star's
parallax, photometry from the literature, and the Yonsei-Yale isochrones (Yi et
al. 2001), respectively. We used the resulting stellar mass of 0.82 +/- 0.05
M_Sun plus the mass function from Benedict et al. (2006) to calculate the
planet's mass, which is 1.53 +/- 0.22 M_Jupiter. Using our new effective
temperature, we also estimated the extent of the habitable zone for the system.Comment: Accepted for publication in The Astrophysical Journa
The ortho-para H2 distribution on Uranus: Constraints from the collision-induced 3-0 dipole band and 4-0 S(0) and S(1) quadrupole line profiles
Recent high quality spectral observations have allowed the derivation of constraints on the atmospheric structure of Uranus. The present analysis, which is based on the detailed modeling of a broadband geometric albedo spectrum and high resolution observations of the H2 4-0 quadrupole and 6818.9-A CH4 features, yields (1) a family of models which parameterize an upper tropospheric haze layer, (2) a lower, optically infinite cloud at a given pressure level, (3) the cloud-level methane molar fraction, and (4) the mean ortho/para ratio in the visible atmosphere. The single scattering albedo of atmospheric aerosols exhibits a steep darkening between 5890 and 6040 A
Inspection and Characterization of Exoplanet Using the CHARA Array
Until the last decade or so, our entire knowledge of planets around Sun-like stars consisted of those in our own Solar System. This is no longer the case. Over 200 planets have been discovered through radial velocity surveys and photometric studies, both of which depend on observing the planet\u27s effects on its host star. Much of our knowledge of the planets orbiting these stars is uncertain, based on assumptions about the stars\u27 masses and the planets\u27 orbital inclinations. This dissertation is comprised of two main sections. The first involves measuring the angular diameters for a sample of exoplanet host stars using Georgia State University\u27s CHARA Array in order to learn more about the nature of these stars. These direct angular measurements are not dependent on the exoplanet systems\u27 inclinations or the masses of the stars. Improved angular diameters lead to linear diameters when combined with HIPPARCOS parallax measurements, which in turn tell us of the stars\u27 ages and masses. Of the 82 exoplanet systems observable with the CHARA Array, 31 host stars were observed and stellar angular diameters were measured for 26 systems. In the special case of an exoplanet system with a transiting planet, this direct measurement of the star\u27s angular diameter leads to a direct measurement of the planet\u27s diameter, when the planet-to-star-radii ratio is known from photometric studies. This was done for HD 189733. The star\u27s angular diameter is 0.377 +/- 0.024 mas, which produces a stellar linear radius of 0.779 +/- 0.052 R_Sun and a planetary diameter of 1.19 +/- 0.08 R_Jupiter. The second part of this project involved the inspection of the exoplanet systems for stellar companions masquerading as planets. From radial velocity studies alone, it is impossible to distinguish between a planet in a high-inclination orbit and a low-mass stellar companion in a low-inclination orbit. Using the CHARA Array, it was possible to rule out certain secondary spectral types for each exoplanet system observed by studying the errors in the diameter fit and searching for separated fringe packets. While no definitive stellar companions were found, two expolanet systems, upsilon Andromedae and rho Coronae Borealis, exhibited behavior that were not consistent with the host star being a simple limb-darkened disk
Development and Conflict Prevention: Reflections on Rwanda - An Interview with Professor Peter Uvin
'White knuckle care work' : violence, gender and new public management in the voluntary sector
Drawing on comparative data from Canada and Scotland, this article explores reasons why violence is tolerated in non-profit care settings. This article will provide insights into how workers' orientations to work, the desire to care and the intrinsic rewards from working in a non-profit context interact with the organization of work and managerially constructed workplace norms and cultures (Burawoy, 1979) to offset the tensions in an environment characterized by scarce resources and poor working conditions. This article will also outline how the same environment of scarce resources causes strains in management's efforts to establish such cultures. Working with highly excluded service users with problems that do not respond to easy interventions, workers find themselves working at the edge of their endurance, hanging on by their fingernails, and beginning to participate in various forms of resistance; suggesting that even among the most highly committed, 'white knuckle care' may be unsustainable
Constrained by managerialism : caring as participation in the voluntary social services
The data in this study show that care is a connective process, underlying and motivating participation and as a force that compels involvement in the lives of others, care is at least a micro-participative process. Care or affinity not only persisted in the face of opposition, but it was also used by workers as a counter discourse and set of practices with which to resist the erosion of worker participation and open up less autonomized practices and ways of connecting with fellow staff, clients and the communities they served. The data suggest that while managerialism and taylorised practice models may remove or reduce opportunities for worker participation, care is a theme or storyline that gave workers other ways to understand their work and why they did it, as well as ways they were prepared to resist managerial priorities and directives, including the erosion of various kinds of direct and indirect participation. The degree of resistance possible, even in the highly technocratic worksite in Australia, shows that cracks and fissures exist within managerialism
Automatic estimation of flux distributions of astrophysical source populations
In astrophysics a common goal is to infer the flux distribution of
populations of scientifically interesting objects such as pulsars or
supernovae. In practice, inference for the flux distribution is often conducted
using the cumulative distribution of the number of sources detected at a given
sensitivity. The resulting "-" relationship can be used to
compare and evaluate theoretical models for source populations and their
evolution. Under restrictive assumptions the relationship should be linear. In
practice, however, when simple theoretical models fail, it is common for
astrophysicists to use prespecified piecewise linear models. This paper
proposes a methodology for estimating both the number and locations of
"breakpoints" in astrophysical source populations that extends beyond existing
work in this field. An important component of the proposed methodology is a new
interwoven EM algorithm that computes parameter estimates. It is shown that in
simple settings such estimates are asymptotically consistent despite the
complex nature of the parameter space. Through simulation studies it is
demonstrated that the proposed methodology is capable of accurately detecting
structural breaks in a variety of parameter configurations. This paper
concludes with an application of our methodology to the Chandra Deep Field
North (CDFN) data set.Comment: Published in at http://dx.doi.org/10.1214/14-AOAS750 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Developing the evidence-base for school sex education programmes: Contributions of an augmented Theory of Planned Behaviour, gender and school year across three contraceptive methods
Background Positive adolescent sexual health is supported by effective school based sex education. Methods to promote positive sexual health need to reflect determinants of contraception intention, which must include understanding gender and age (year group) differences. To date, there has been limited theory-based exploration of these determinants in school-age participants, placing limitations on sexual health educators to tailor learning most effectively. MethodsCross sectional survey data was collected from UK school pupils (N = 1378) aged 12-16 years. Measures included Theory of Planned Behaviour, Prototype Willingness, anticipated regret and knowledge items. Linear regression determined significant predictors of intention to use condoms, the oral contraceptive pill and the emergency contraceptive pill. t-tests and ANOVAs were used to assess differences by gender and school year. ResultsThree distinct predictive models emerged for condom, pill and EC, predicting 36%, 18% and 23% variance respectively. Attitude, gender and anticipated regret for unprotected sex significantly predicted intention for all types (p<.001). The influence of other explanatory variables differed by contraceptive. Girls scored higher on all variables except condom intention, and intention scores peaked in year 10. ConclusionCondoms, pill and EC intention have different predictive profiles, with girls more strongly motivated and year 10 a crucial stage for intention. Social comparisons and control beliefs exert differential effects across contraceptive types whilst attitudes and anticipated regret are consistently strong influences. Findings suggest clear scope for supporting sexual health and wellbeing through modified school sex education
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