14,515 research outputs found

    Disc Clearing of Young Stellar Objects: Evidence for Fast Inside-out Dispersal

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    The time-scale over which and the modality by which young stellar objects (YSOs) disperse their circumstellar discs dramatically influences the eventual formation and evolution of planetary systems. By means of extensive radiative transfer (RT) modelling, we have developed a new set of diagnostic diagrams in the infrared colour-colour plane (K-[24] vs. K-[8]), to aid with the classification of the evolutionary stage of YSOs from photometric observations. Our diagrams allow the differentiation of sources with unevolved (primordial) discs from those evolving according to different clearing scenarios (e.g. homologous depletion vs. inside-out dispersal), as well as from sources that have already lost their disc. Classification of over 1500 sources in 15 nearby star-forming regions reveals that approximately 39 % of the sources lie in the primordial disc region, whereas between 31 % and 32 % disperse from the inside-out and up to 22 % of the sources have already lost their disc. Less than 2 % of the objects in our sample lie in the homogeneous draining regime. Time-scales for the transition phase are estimated to be typically a few 10^5 years independent of stellar mass. Therefore, regardless of spectral type, we conclude that currently available infrared photometric surveys point to fast (of order 10 % of the global disc lifetime) inside-out clearing as the preferred mode of disc dispersal.Comment: 31 pages, 21 figures, 6 tables, accepted for publication in MNRA

    The sexual health needs of looked after young people; findings from qualitative interviews led through public health and health psychology.

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    Background - Looked after young people (LAYP) have poorer sexual health outcomes than their peers. However, research seldom examines the health needs of, or intervenes with, this group. The aim of the current study was to identify LAYP's perceived sexual health needs and explore sources of sexual health information, knowledge levels, concerns and service preferences. Methods - Looked after young people within Fife, Scotland, were recruited through their workers and carers to participate in qualitative semi-structured interviews. Those aged 12–19 years were targeted for recruitment. National Health Services ethics approval was granted. Thematic analysis was conducted using NVivo. Results - Interviews were conducted with 10 LAYP. Key themes included gaps in knowledge, and gaps between knowledge and behaviour. Being ‘looked after’ may have negative consequences on knowledge, sources of support and safer sex. A flexible, one-to-one service, aimed at several lifestyle issues, not solely sexual health, was preferred by respondents. Conclusion - Looked after young people require support to bridge the gap between knowledge and behaviour and several theories relevant to the findings have been identified. Participants desired more support around a range of health issues, which may come from school, workers and carers, as well as health professionals. Further research examining effective interventions with this group is crucial to improve outcomes

    Assessing the efficacy of registered underground baiting products for mountain beaver (Aplodontia rufa) control

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    The mountain beaver (Aplodontia rufa) is a fossorialrodent species endemic to the Pacific Northwest and portions of California. This herbivore inflicts millions of dollars of damage annually to forest seedling plantations. Currently, extensive trapping prior to planting is the most reliable method for reducing damage. With increasing restrictions placed on trapping, forest resource managers need alternative tools to minimize forest damage. This study assessed the potential of four toxicants registered for underground use to controlmountain beaver; zinc phosphide, diphacinone, chlorophacinone, and strychnine. Zinc phosphide and strychnine are acute toxicants, whereas diphacinone and chlorophacinone are anticoagulants. Anticoagulants prevent the recycling of vitamin K in the body, which inhibits the production of clotting factors. Efficacy varied among treatments. Zinc phosphide and strychnine were avoided by mountain beaver. Pre-baiting marginally increased acceptance of strychnine, but did not alter mountain beaver acceptance of zinc phosphide. Diphacinone and chlorophacinone were both readily consumed, but only chlorophacinone was 100% effective after a 14-day baiting regime. Subsequently, we tested the effects of diet on the efficacy of diphacinone by varying the availability of food containing vitamin K, the anticoagulant antidote. Restricting access to potential sources of vitamin K appeared to increase efficacy. We conclude that anticoagulants hold some promise as additional tools for managers to reduce mountain beaver populations with chlorophacinone showing the most promise. However, limitations to anticoagulant baits include the necessity of long-term baiting (greater than 10 days), a possible decrease in toxicity if baits contact moisture, and potential primary hazards

    Leading contributors to accountancy

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    Doctoral candidates at many schools are expected to be familiar with the individuals who have made a significant contribution to the field of accounting. This awareness and appreciation of individuals who have contributed to accounting is considered to be basic knowledge which any candidate for a Ph.D. in Accountancy should possess. However, when considering individuals who have helped to advance the profession of accountancy many names come to mind, names such as Luca Pacioli, Robert Sprousc, Maurice Moonitz, William Paton, A. C. Littleton, Edgar Edwards, Philip Bell, Robert Anthony, George May, Carman Blough, John Burton, Francis Wheat, and Robert Trueblood, to name but a few. Thus, being familiar with the works and achievements of all significant accounting contributors is a formidable task, to say the least, to a Ph.D. candidate who is studying for his/her comprehensive written and oral examinations in accounting. As a consequence, a research study was undertaken to determine the answer to the following question: Which individuals are perceived, by current accounting professors, to have contributed the most to the field of accounting

    Neurofilament Phosphorylation during Development and Disease: Which Came First, the Phosphorylation or the Accumulation?

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    Posttranslational modification of proteins is a ubiquitous cellular mechanism for regulating protein function. Some of the most heavily modified neuronal proteins are cytoskeletal proteins of long myelinated axons referred to as neurofilaments (NFs). NFs are type IV intermediate filaments (IFs) that can be composed of four subunits, neurofilament heavy (NF-H), neurofilament medium (NF-M), neurofilament light (NF-L), and α-internexin. Within wild type axons, NFs are responsible for mediating radial growth, a process that determines axonal diameter. NFs are phosphorylated on highly conserved lysine-serine-proline (KSP) repeats located along the C-termini of both NF-M and NF-H within myelinated axonal regions. Phosphorylation is thought to regulate aspects of NF transport and function. However, a key pathological hallmark of several neurodegenerative diseases is ectopic accumulation and phosphorylation of NFs. The goal of this review is to provide an overview of the posttranslational modifications that occur in both normal and diseased axons. We review evidence that challenges the role of KSP phosphorylation as essential for radial growth and suggests an alternative role for NF phosphorylation in myelinated axons. Furthermore, we demonstrate that regulation of NF phosphorylation dynamics may be essential to avoiding NF accumulations

    Assessing the efficacy of registered underground baiting products for mountain beaver (Aplodontia rufa) control

    Get PDF
    The mountain beaver (Aplodontia rufa) is a fossorialrodent species endemic to the Pacific Northwest and portions of California. This herbivore inflicts millions of dollars of damage annually to forest seedling plantations. Currently, extensive trapping prior to planting is the most reliable method for reducing damage. With increasing restrictions placed on trapping, forest resource managers need alternative tools to minimize forest damage. This study assessed the potential of four toxicants registered for underground use to controlmountain beaver; zinc phosphide, diphacinone, chlorophacinone, and strychnine. Zinc phosphide and strychnine are acute toxicants, whereas diphacinone and chlorophacinone are anticoagulants. Anticoagulants prevent the recycling of vitamin K in the body, which inhibits the production of clotting factors. Efficacy varied among treatments. Zinc phosphide and strychnine were avoided by mountain beaver. Pre-baiting marginally increased acceptance of strychnine, but did not alter mountain beaver acceptance of zinc phosphide. Diphacinone and chlorophacinone were both readily consumed, but only chlorophacinone was 100% effective after a 14-day baiting regime. Subsequently, we tested the effects of diet on the efficacy of diphacinone by varying the availability of food containing vitamin K, the anticoagulant antidote. Restricting access to potential sources of vitamin K appeared to increase efficacy. We conclude that anticoagulants hold some promise as additional tools for managers to reduce mountain beaver populations with chlorophacinone showing the most promise. However, limitations to anticoagulant baits include the necessity of long-term baiting (greater than 10 days), a possible decrease in toxicity if baits contact moisture, and potential primary hazards

    The Henry’s Fork: Finding Mutual Interest in the Watershed

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    9 pages. Contains references
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