14,120 research outputs found
Disc wind models for FU Ori objects
We present disc wind models aimed at reproducing the main features of the
strong Na I resonance line P-Cygni profiles in the rapidly-accreting pre-main
sequence FU Ori objects. We conducted Monte Carlo radiative transfer
simulations for a standard magnetocentrifugally driven wind (MHD) model and our
own "Genwind" models, which allows for a more flexible wind parameterisation.
We find that the fiducial MHD wind and similar Genwind models, which have flows
emerging outward from the inner disc edge, and thus have polar cavities with no
absorbing gas, cannot reproduce the deep, wide Na I absorption lines in FU Ori
objects viewed at low inclination. We find that it is necessary to include an
"inner wind" to fill this polar cavity to reproduce observations. In addition,
our models assuming pure scattering source functions in the Sobolev
approximation at intermediate viewing angles () do not yield sufficiently deep line profiles. Assuming complete
absorption yields better agreement with observations, but simple estimates
strongly suggest that pure scattering should be a much better approximation.
The discrepancy may indicate that the Sobolev approximation is not applicable,
possibly due to turbulence or non-monotonic velocity fields; there is some
observational evidence for the latter. Our results provide guidance for future
attempts to constrain FU Ori wind properties using full MHD wind simulations,
by pointing to the importance of the boundary conditions necessary to give rise
to an inner wind, and by suggesting that the winds must be turbulent to produce
sufficiently deep line profiles.Comment: 12 pages, 17 figures, accepted for publication in MNRA
Gauge drivers for the generalized harmonic Einstein equations
The generalized harmonic representation of Einstein's equations is manifestly hyperbolic for a large class of gauge conditions. Unfortunately most of the useful gauges developed over the past several decades by the numerical relativity community are incompatible with the hyperbolicity of the equations in this form. This paper presents a new method of imposing gauge conditions that preserves hyperbolicity for a much wider class of conditions, including as special cases many of the standard ones used in numerical relativity: e.g., K freezing, Gamma freezing, Bona-Massó slicing, conformal Gamma drivers, etc. Analytical and numerical results are presented which test the stability and the effectiveness of this new gauge-driver evolution system
Application of adaptive antenna techniques to future commercial satellite communication
The purpose of this contract was to identify the application of adaptive antenna technique in future operational commercial satellite communication systems and to quantify potential benefits. The contract consisted of two major subtasks. Task 1, Assessment of Future Commercial Satellite System Requirements, was generally referred to as the Adaptive section. Task 2 dealt with Pointing Error Compensation Study for a Multiple Scanning/Fixed Spot Beam Reflector Antenna System and was referred to as the reconfigurable system. Each of these tasks was further sub-divided into smaller subtasks. It should also be noted that the reconfigurable system is usually defined as an open-loop system while the adaptive system is a closed-loop system. The differences between the open- and closed-loop systems were defined. Both the adaptive and reconfigurable systems were explained and the potential applications of such systems were presented in the context of commercial communication satellite systems
Application of adaptive antenna techniques to future commercial satellite communications. Executive summary
The purpose of this contract was to identify the application of adaptive antenna technique in future operational commercial satellite communication systems and to quantify potential benefits. The contract consisted of two major subtasks. Task 1, Assessment of Future Commercial Satellite System Requirements, was generally referred to as the Adaptive section. Task 2 dealt with Pointing Error Compensation Study for a Multiple Scanning/Fixed Spot Beam Reflector Antenna System and was referred to as the reconfigurable system. Each of these tasks was further subdivided into smaller subtasks. It should also be noted that the reconfigurable system is usually defined as an open-loop system while the adaptive system is a closed-loop system. The differences between the open- and closed-loop systems were defined. Both the adaptive and reconfigurable systems were explained and the potential applications of such systems were presented in the context of commercial communication satellite systems
If i had one -- it would be huge
By alluding to genitalia, If I Had One-It Would Be Huge calls attention to the need in contemporary society to eliminate gender bias in favor of more relevant criteria for evaluating an individual\u27s worth and potential. Gender is never an appropriate criterion. By referring to one, it also alludes to bringing what appears to be opposite elements, materials, and viewpoints into compatibility. On examination of the completed pieces which I selected for the thesis exhibit, I found that a quote from Eugene Delacroix1 was very appropriate as the Artist\u27s Statement for my thesis exhibit: The scientist discovers the elements of things, if you like, and the artist, with elements having no value in the place they chance to be, composes, invents a unity, in one word, creates; he strikes the imagination of men by the spectacle of his creations, and in a particular manner. He renders clear the sensations that things arouse within us, and which the great run of men, in the presence of nature, only vaguely see and feel. This thesis also describes the installation of my work in general and in terms of the materials in the four individual pieces. Opposite elements are incorporated into four pieces (Untitled-Slide #1, Chick-Slides #2 and #3, Building-Slides #4 and #5, and Altar-Slide #6) primarily through the use of unusual combinations of materials. In addition to the material combinations that make up the installation, symbolic elements are also suggestive of opposite elements. The choice of particular materials is based on the interpretation of the environment and what seems to dominate it. Each of the pieces is intended to be clear, honest, non-didactic, and accessible
A Profile of North Carolina Lesbian, Gay, and Bisexual Health Disparities, 2011
Objectives. We investigated the health profile of lesbian, gay, and bisexual (LGB) adults in North Carolina, the first state in the South to include a measure of sexual orientation identity in a probability-based statewide health survey. Methods. Using data from 9876 respondents in the 2011 North Carolina Behavioral Risk Factor Surveillance Survey, we compared sexual minorities to heterosexuals on a variety of health indicators. Results. LGB respondents were younger and more likely to be reached by cell phone. Many examined indicators were not different by sexual orientation. Significant results, however, were consistent with findings from state population surveys in other regions of the country, including disparities in mental health and, among women, smoking. Conclusions. Reporting LGB identity in North Carolina is associated with poorer health. The concentration of anti-LGB policies in the South warrants ongoing monitoring of LGB health disparities in North Carolina and in other Southeastern states for potential effects on the health and well-being of LGB populations
ALMA observations of the outflow from the Source I in the Orion-KL region
In this {\it Letter}, we present sensitive millimeter SiO (J=5-4; =0)
line observations of the outflow arising from the enigmatic object Orion Source
I made with the Atacama Large Millimeter/Submillimeter Array (ALMA). The
observations reveal that at scales of a few thousand AU, the outflow has a
marked "butterfly" morphology along a northeast-southwest axis. However,
contrary to what is found in the SiO and HO maser observations at scales of
tens of AU, the blueshifted radial velocities of the moving gas are found to
the northwest, while the redshifted velocities are in the southeast. The ALMA
observations are complemented with SiO (J=8-7; =0) maps (with a similar
spatial resolution) obtained with the Submillimeter Array (SMA). These
observations also show a similar morphology and velocity structure in this
outflow. We discuss some possibilities to explain these differences at small
and large scales across the flow.Comment: Accepted to ApJ
Predictors of Readiness to Quit Among a Diverse Sample of Sexual Minority Male Smokers
ABSTRACT
Introduction: Readiness to quit smoking - a pattern of attitudes, intentions, and behaviors that reflect a likelihood of engaging in cessation activities—is a useful heuristic for understanding smoking disparities based on sexual orientation. This study examined demographic, tobacco-use patterns, psychosocial and cognitive factors associated with readiness to quit among gay and bisexual male smokers.
Methods: A cross-sectional survey was conducted as part of a larger Tobacco Elimination and Control Collaboration (Q-TECC) initiative in the lesbian, gay, bisexual, and transgender (LGBT) community. Readiness to quit was measured by a composite score created from four variables (motivation to quit, importance of quitting, plan to quit, and confidence in quitting) (alpha=.87, M=3.42, SD=.96, range 1-5).
Results: The sexual minority smokers in the sample (N=208; M=33 years) were racially/ethnically diverse. Latino men had significantly lower levels of readiness to quit compared to African American and White men. Hierarchical linear regression analyses were performed to explore the relative contributions of sociodemographic, tobacco-use patterns, psychosocial and cognitive factors on Readiness to Quit. In the final model, the following variables were associated with readiness to quit scores: Latino ethnicity, fewer quit attempts, positive expectancies for the beneficial effects of smoking, and lower perceived importance of smoking as an important LGBT health issue. None of the psychosocial factors were associated with readiness to quit.
Discussion: Readiness to quit scores were largely predicted by modifiable attitudes, behaviors, and expectancies. Study findings have implications for improving outreach and awareness and for the development of effective treatment approaches
Preaching to the converted: the value of organisationally supported carbon reduction initiatives
Organisation led carbon reduction initiatives are bridging the gap between purely individual
environmental action and higher level intervention and regulation. This research looks into one of
those initiatives aimed at engaging employees in carbon reduction. We adopt a single case study
approach following learning activities of volunteers within a UK organisation over four months.
Observations of their activities were conducted, in addition to interviews with participants and
organisers.
Our core findings are, firstly, that rather than engaging a wide range of employees, only a very
narrow group chose to participate. This group bears similarities with Barr and Gilg’s (2006)
classification of ‘committed’ environmentalists which suggests that those willing to participate in
these initiatives may be those for whom environmentalism is personally relevant. That there was
little evidence of the initiative engaging a broader network of employees raises questions on the
effectiveness of these activities in the wider population of employees. Secondly, we identified
attitude behaviour gaps to varying degrees among participants who still made carbon intensive choices especially in relation to air travel, for example.
We conclude by analysing the effectiveness of the intervention and the associated challenges.
Recommendations are made covering several dimensions such as the potential role of technology in
facilitating behaviour change, and organisational policy making with regards to employee
engagement to carbon reduction
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