10,184 research outputs found
Clouds, Clumps, Cores & Comets - a Cosmic Chemical Connection?
We discuss the connection between the chemistry of dense interstellar clouds
and those characteristics of cometary matter that could be remnants of it. The
chemical evolution observed to occur in molecular clouds is summarized and a
model for dense core collapse that can plausibly account for the isotopic
fractionation of hydrogen, nitrogen, oxygen and carbon measured in primitive
solar system materials is presented.Comment: to be published in Advances in Geoscience
Growth and Coagulation in a Herding Model
We discuss various existing models which mimic the herding effect in financial markets and introduce a new model of herding which incorporates both growth and coagulation. In this model, at each time step either (i) with probability p the system grows through the introduction of a new agent or (ii) with probability q=1-p two groups are selected at random and coagulate. We show that the size distribution of these groups has a power law tail with an exponential cut-off. A variant of our basic model is also discussed where rates are proportional to the size of a grou
Examining the role of mental health and clinical issues within talent development
Although significant research supports the association between physical activity and mental wellbeing, current literature acknowledges that athletes are no less susceptible to mental illness than the general population. Despite welcomed initiatives aimed at improving mental health within elite sport, these programs often fail to target young athletes; an important concern given that the genesis of many mental illnesses are recognized to occur during this critical period. Given the importance of early intervention and effective treatment, and the potentially devastating consequences of clinical issues going undiagnosed, the implications for talent identification and development become obvious. With this in mind, this study sought to examine the range of mental health issues that may impact upon developing athletes and potential consequences for the development process, specific risk and protective factors associated with talent development, along with an examination of current practices concerning the identification of mental health issues in such environments. Qualitative interviews were conducted with purposively sampled clinicians (n = 8) experienced in working with adolescents and/or young athletes. Inductive content analysis was undertaken, identifying four main themes: key behavioral indicators; associated risk factors; associated protective factors; and issues around identification and diagnosis. Key behavioral indicators included behavioral change, along with behaviors associated with eating disorders, anxiety and depression. Risk factors centered on family background, the performance environment, and issues surrounding adolescence. Protective factors were primarily social in nature. Finally, a lack of awareness and understanding of clinical issues, multiple causes of symptoms, non-disclosure and the need for triangulation of assessment were identified. The need for improved identification and intervention strategies was apparent, with coaches identified as well placed to detect general ‘warning signs’ such as behavioral change. Short of integrating trained clinicians into talent development environments, as part of a triangulation process, ecologically validated assessment tools – coupled with appropriate training and signposting – could offer a practical way of flagging potential issues in developing athletes. The need for the development of such an instrument is therefore apparent. Finally, education around the influential role of family is also recommended in order to promote the protective elements and mitigate risk factors
Analytical design and performance studies of the nuclear light bulb engine
Analytical studies were conducted to investigate in detail the heat balance characteristics of the nuclear light bulb engine. Distributions of energy deposition to all engine components from the fission process, conduction and convection, and thermal radiation were considered. Where uncertainties in basic data or heat transfer characteristics were encountered, ranges of heat loads were calculated and reference values were selected. The influence of these heat loads on engine performance, space radiator requirements, and cooling sequence and cooling circuit designs was determined. The analyses resulted in revisions to the previously reported reference engine characteristics, principally in the heat loads to some engine components and in the cooling sequence. These revisions were incorporated in the engine dynamics digital computer simulation program. No significant changes occurred in the dynamic response of the engine to perturbations in fuel injection rate, reactivity or exhaust nozzle area
Analytical studies of nuclear light bulb engine radiant heat transfer and performance characteristics
Analytical model of nuclear light bulb engine radiant heat transfer and engine performance, dynamics and control, heat loads and shutdown characteristic
Food Security and the Federal Minimum Wage
This working paper, by William M. Rodgers III, Hanley S. Chiang, and Bruce W. Klein, estimates the extent to which increases in the U.S. federal minimum wage in October 1996 and September 1997 improved the ability of households to be food secure -- that is, to purchase for their members an adequate supply of nutritional and safe foods. First, the authors show that the two increases significantly altered the hourly wage distribution of householders (principal person in a household). The shifts were greatest among household heads that are minority, single parents, and household heads with no more than a high school diploma. Even after controlling for the link between the 1990s economic expansion and food security, the October 1996 and September 1997 increases in the federal minimum wage raised food security and reduced hunger, particularly in low-income households where householders had completed no more than a high school degree or were a single parent
Responses of Hyalella azteca and Ceridaphnia dubia to reservoir sediments following Chelated Copper Herbicide Applications
In response to nuisance growths of algae and vascular
plants, such as dioecious hydrilla (
Hydrilla verticillata
L.f.
Royle), copper formulations have been applied in lakes and
reservoirs for a number of years. Concerns have arisen regarding
the long-term consequences of copper applications
and those concerns have appropriately focused on sediment
residues. In this study, we evaluated the toxicity of sediments
from treated (for a decade) and untreated areas in Lake
Murray, South Carolina and estimated the capacity of those
sediments to bind additional copper. Two sentinel aquatic invertebrates,
Hyalella azteca
Saussure and
Ceriodaphnia dubia
Richard, were used to measure residual toxicity of treated
and untreated sediments from the field and after laboratory
amendments. (PDF has 5 pages.
Stable One-Dimensional Integral Representations of One-Loop N-Point Functions in the General Massive Case: I - Three Point Functions
In this article we provide representations for the one-loop three point
functions in 4 and 6 dimensions in the general case with complex masses. The
latter are part of the GOLEM library used for the computation of one-loop
multileg amplitudes. These representations are one-dimensional integrals
designed to be free of instabilites induced by inverse powers of Gram
determinants, therefore suitable for stable numerical implementations.Comment: 40 pages, 1 figur
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