2,070 research outputs found
Turbulent transport of impurities and their effect on energy confinement
By presenting linear and nonlinear gyrokinetic studies, based on a balanced
neutral beam injection deuterium discharge from the DIII-D tokamak, we
demonstrate that impurities alter the scaling of the transport on the charge
and mass of the main species, and even more importantly, they can dramatically
change the energy transport even in relatively small quantities. A poloidally
varying equilibrium electrostatic potential can lead to a strong reduction or
sign change of the impurity peaking factor due to the combined effect of the
in-out impurity density asymmetry and the EXB drift of impurities. We present
an approximate expression for the impurity peaking factor and demonstrate that
impurity peaking is not significantly affected by impurity self-collisions.Comment: Accepted for publication in Plasma Physics and Controlled Fusio
Characteristics of drug and dietary supplement inquiries by college athletes.
BackgroundIn the United States, the National Center for Drug Free Sport manages the drug-testing programs for athletes of the National Collegiate Athletic Association (NCAA). Through its Resource Exchange Center (REC), Drug Free Sport supports athletic staff and athletes with information regarding drugs and dietary supplements.PurposeTo characterize the types of drug-related and dietary supplement-related inquiries submitted to Drug Free Sport through the REC.Study designCross-sectional study.MethodsAll inquiries submitted to the REC for the period of September 1, 2005, through June 30, 2006, were reviewed. The data were categorized by the method of inquiry submission; the name of the substance in question; the sex, sport, and NCAA division of the athlete involved; the nature of the inquiry; and the response provided by the REC regarding the NCAA's status of the substance in question.ResultsPseudoephedrine, acetaminophen/hydrocodone, and albuterol were the most commonly self-searched medications; stimulants accounted for the majority of banned medications. Dietary supplements accounted for 80% of all inquiries submitted to the REC via the Banned Drug Inquiry Form. Among all dietary supplements, creatine was the most commonly inquired. Banned substances accounted for 29% of all inquiries.ConclusionsThere were more than 10 000 inquiries regarding the status of medications, dietary supplements, and other substances for NCAA athletes during the 2005-2006 academic year. It is helpful for athletes to have resources that help them navigate banned-substance lists and so avoid the inadvertent use of banned substances.Clinical relevanceEducating athletes regarding the stimulant content of various dietary supplements and addressing the lack of clinical trials to support stated claims and safety appear critical
Competing Alignments of Nematic Liquid Crystals on Square Patterned Substrates
A theoretical analysis is presented of a nematic liquid crystal confined
between substrates pat- terned with squares that promote vertical and planar
alignment. Two approaches are used to eluci- date the behavior across a wide
range of length scales: Monte Carlo simulation of hard particles and
Frank-Oseen continuum theory. Both approaches predict bistable degenerate
azimuthal alignment in the bulk along the edges of the squares; the continuum
calculation additionally reveals the possi- bility of an anchoring transition
to diagonal alignment if the polar anchoring energy associated with the pattern
is sufficiently weak. Unlike the striped systems previously analyzed, the Monte
Carlo simulations suggest that there is no "bridging" transition for
sufficiently thin cells. The extent to which these geometrically patterned
systems resemble topographically patterned substrates, such as square wells, is
also discussed.Comment: 11 pages, 12 figure
Sequential threat detection for harbor defense: An x-ray physics-based bayesian approach
Abstract not provide
Stigma and sexuality : how burn survivors and relational partners manage their experiences
"July 2014."Dissertation Advisor: Dr. Rebecca J. Meisenbach.Includes vita.Burn survivors and their injuries are studied exhaustively while in the context of the hospital; however, what happens after they leave and interact with others is under-researched. Despite the expansive amount of research in the areas of stigma communication, sexuality, and burn survivor, scholars have yet to examine the stigma and sexuality experiences of survivors and relational partners. Through hermeneutic phenomenology, this study explores the stigma management and sexuality experiences of both survivors and relational partners. Interviews were conducted with 19 survivors and 8 relational partners across the United States. Results indicated that survivors managed stigma using the following four strategy patterns: Accepters, Situational Adopters, Challengers, and Dissembling Challengers. Relational partners a different pattern to manage stigma. While stigma seemed to be constructed separately by survivors and partners, sexuality was more clearly co-constructed. Sexuality of the survivor was co-constructed as: feeling not sexy, being fragile, being a new normal, and not being impacted. Implications for addition of the interpersonal context to the SMC model, patterns of stigma strategies, and future research are presented.Includes bibliographical references (pages 142-152)
Asymmetries in Mars' Exosphere: Implications for X-ray and ENA Imaging
Observations and simulations show that Mars' atmosphere has large seasonal
variations. Total atmospheric density can have an order of magnitude
latitudinal variation at exobase heights. By numerical simulations we show that
these latitude variations in exobase parameters induce asymmetries in the
hydrogen exosphere that propagate to large distances from the planet. We show
that these asymmetries in the exosphere produce asymmetries in the fluxes of
energetic neutral atoms (ENAs) and soft X-rays produced by charge exchange
between the solar wind and exospheric hydrogen. This could be an explanation
for asymmetries that have been observed in ENA and X-ray fluxes at Mars.Comment: Submitted to Space Science Review. v2: Minor changes in text and
figure
Macrogol (polyethylene glycol) laxatives in children with functional constipation and faecal impaction: a systematic review
As the evidence base supporting the use of laxatives in children is very limited, we undertook an updated systematic review to clarify the issue. A comprehensive literature search was carried out to identify randomised controlled trials of polyethylene glycol (PEG) versus either placebo or active comparator, in patients aged <18 years with primary chronic constipation. Outcomes were assessed as either global assessments of effectiveness or differences in defaecation rates. Seven qualifying studies involving 594 children were identified. Five were comparisons of PEG with lactulose, one with milk of magnesia and one with placebo. Study duration ranged from 2 weeks to 12 months. PEG was significantly more effective than placebo and either equivalent to (two studies) or superior to (four studies) active comparator. Differences in study design precluded meaningful meta-analysis. Lack of high quality studies has meant that the management of childhood constipation has tended to rely on anecdote and empirical treatment choice. Recent publication of well designed randomised trials now permits a more evidence-based approach, with PEG-based treatments having been proven to be effective and well-tolerated first-line treatment
An Enhanced Nonlinear Critical Gradient for Electron Turbulent Transport due to Reversed Magnetic Shear
The first nonlinear gyrokinetic simulations of electron internal transport
barriers (e-ITBs) in the National Spherical Torus Experiment show that reversed
magnetic shear can suppress thermal transport by increasing the nonlinear
critical gradient for electron-temperature-gradient-driven turbulence to three
times its linear critical value. An interesting feature of this turbulence is
nonlinearly driven off-midplane radial streamers. This work reinforces the
experimental observation that magnetic shear is likely an effective way of
triggering and sustaining e-ITBs in magnetic fusion devices.Comment: 4 pages, 5 figure
- …