331 research outputs found

    Hydrodynamic ablation of protoplanetary disks via supernovae

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    We present three-dimensional simulations of a protoplanetary disc subject to the effect of a nearby (0.3 pc distant) supernova (SN), using a time-dependent flow from a one-dimensional numerical model of the supernova remnant (SNR), in addition to constant peak ram pressure simulations. Simulations are performed for a variety of disc masses and inclination angles. We find disc mass-loss rates that are typically 10−7–10−6 M yr−1 (but they peak near 10−5 M yr−1 during the ‘instantaneous’ stripping phase) and are sustained for around 200 yr. Inclination angle has little effect on the mass-loss unless the disc is close to edge-on. Inclined discs also strip asymmetrically with the trailing edge ablating more easily. Since the interaction lasts less than one outer rotation period, there is not enough time for the disc to restore its symmetry, leaving the disc asymmetrical after the flow has passed. Of the low-mass discs considered, only the edge-on disc is able to survive interaction with the SNR (with 50 per cent of its initial mass remaining). At the end of the simulations, discs that survive contain fractional masses of SN material up to 5 × 10−6. This is too low to explain the abundance of short-lived radionuclides in the early Solar system, but a larger disc and the inclusion of radiative cooling might allow the disc to capture a higher fraction of SN material

    On the Energy Dependence of the Dipole-Proton Cross Section in Deep Inelastic Scattering

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    We study the dipole picture of high-energy virtual-photon-proton scattering. It is shown that different choices for the energy variable in the dipole cross section used in the literature are not related to each other by simple arguments equating the typical dipole size and the inverse photon virtuality, contrary to what is often stated. We argue that the good quality of fits to structure functions that use Bjorken-x as the energy variable - which is strictly speaking not justified in the dipole picture - can instead be understood as a consequence of the sign of scaling violations that occur for increasing Q^2 at fixed small x. We show that the dipole formula for massless quarks has the structure of a convolution. From this we obtain derivative relations between the structure function F_2 at large and small Q^2 and the dipole-proton cross section at small and large dipole size r, respectively.Comment: 27 page

    The Psychological and Physiological Consequences of Low Energy Availability in a Male Combat Sport Athlete.

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    PURPOSE: To evaluate the effects of low energy availability (EA) on health and performance indices associated with the Male Athlete Triad and Relative Energy Deficiency in Sports (RED-S) models. METHODS: Over an 8 week period, a male combat sport athlete adhered to a phased body mass (BM) loss plan consisting of 7 weeks energy intake (EI) equating to resting metabolic rate (RMR) (1700 kcal·day) (Phase 1), 5 days of reduced EI (1200-300 kcal·day) prior to weigh-in (Phase 2) and one week of ad libitum EI post-competition (Phase 3). EA fluctuated day by day due to variations in exercise energy expenditure. Regular assessments of body composition, RMR, cardiac function, cardiorespiratory capacity, strength & power, psychological state and blood clinical chemistry for endocrine, bone turnover, hydration, electrolyte, renal, liver and lipid profiles were performed. RESULTS: BM was reduced over the 8 week period by 13.5% (72.5 to 62.7 kg). No consequences of Male Athlete Triad or RED-S were evident during phase 1, where mean daily EA equated to 20 kcal·kg·FFM·day (range: 7 to 31 kcal·kg·FFM·day) and BM and fat mass (FM) losses were 6.5 and 4.4 kg, respectively. However, consequences did present in phase 2 when mean daily EA was consistently <10 kcal·kg·FFM·day, as evidenced by alterations to endocrine hormones (e.g. testosterone: <5 nmol.L) and reduced RMR (-257 kcal·day). CONCLUSION: Data demonstrate that 7 weeks of daily fluctuations in EA equating to a mean value of 20 kcal·kg·FFM·day permits reductions of BM and FM without perturbations to physiological systems associated with the Male Athlete Triad and RED-S. In contrast, a subsequent period of 5 consecutive days of EA <10 kcal·kg·FFM·day induced consequences of Male Athlete Triad and RED-S

    Implementation of routine outcome measurement in child and adolescent mental health services in the United Kingdom: a critical perspective

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    The aim of this commentary is to provide an overview of clinical outcome measures that are currently recommended for use in UK Child and Adolescent Mental Health Services (CAMHS), focusing on measures that are applicable across a wide range of conditions with established validity and reliability, or innovative in their design. We also provide an overview of the barriers and drivers to the use of Routine Outcome Measurement (ROM) in clinical practice

    The use of routine outcome measures in two child and adolescent mental health services: a completed audit cycle

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    Background: Routine outcome measurement (ROM) is important for assessing the clinical effectiveness of health services and for monitoring patient outcomes. Within Child and Adolescent Mental Health Services (CAMHS) in the UK the adoption of ROM in CAMHS has been supported by both national and local initiatives (such as government strategies, local commissioning policy, and research). Methods: With the aim of assessing how these policies and initiatives may have influenced the uptake of ROM within two different CAMHS we report the findings of two case-note audits: a baseline audit conducted in January 2011 and a re-audit conducted two years later in December 2012-February 2013. Results: The findings show an increase in both the single and repeated use of outcome measures from the time of the original audit, with repeated use (baseline and follow-up) of the Health of the Nation Outcome Scale for Children and Adolescents (HoNOSCA) scale increasing from 10% to 50% of cases. Re-audited case-notes contained more combined use of different outcome measures, with greater consensus on which measures to use. Outcome measures that were applicable across a wide range of clinical conditions were more likely to be used than symptom-specific measures, and measures that were completed by the clinician were found more often than measures completed by the service user. Conclusions: The findings show a substantial improvement in the use of outcome measures within CAMHS. These increases in use were found across different service organisations which were subject to different types of local service priorities and drivers

    Implications of sperm banking for health-related quality of life up to 1 year after cancer diagnosis.

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    Sperm banking is recommended for all men diagnosed with cancer where treatment is associated with risk of long-term gonadatoxicity, to offer the opportunity of fatherhood and improved quality of life. However, uptake of sperm banking is lower than expected and little is known about why men refuse. Our aims were to determine: (i) demographic and medical variables associated with decisions about banking and (ii) differences in quality of life between bankers and non-bankers at diagnosis (Time 1 (T1)) and 1 year later (Time 2 (T2))

    A risk profile for identifying community-dwelling elderly with a highrisk of recurrent falling: results of a 3-year prospective study

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    Introduction: The aim of the prospective study reported here was to develop a risk profile that can be used to identify community-dwelling elderly at a high risk of recurrent falling. Materials and methods: The study was designed as a 3-year prospective cohort study. A total of 1365 community-dwelling persons, aged 65 years and older, of the population-based Longitudinal Aging Study Amsterdam participated in the study. During an interview in 1995/1996, physical, cognitive, emotional and social aspects of functioning were assessed. A follow-up on the number of falls and fractures was conducted during a 3-year period using fall calendars that participants filled out weekly. Recurrent fallers were identified as those who fell at least twice within a 6-month period during the 3-year follow-up. Results: The incidence of recurrent falls at the 3-year follow-up point was 24.9% in women and 24.4% in men. Of the respondents, 5.5% reported a total of 87 fractures that resulted from a fall, including 20 hip fractures, 21 wrist fractures and seven humerus fractures. Recurrent fallers were more prone to have a fall-related fracture than those who were not defined as recurrent fallers (11.9% vs. 3.4%; OR: 3.8; 95% CI: 2.3-6.1). Backward logistic regression analysis identified the following predictors in the risk profile for recurrent falling: two or more previous falls, dizziness, functional limitations, weak grip strength, low body weight, fear of falling, the presence of dogs/cats in the household, a high educational level, drinking 18 or more alcoholic consumptions per week and two interaction terms (high educationx18 or more alcohol consumptions per week and two or more previous falls x fear of falling) (AUC=0.71). Discussion: At a cut-off point of 5 on the total risk score (range 0-30), the model predicted recurrent falling with a sensitivity of 59% and a specificity of 71%. At a cut-off point of 10, the sensitivity and specificity were 31% and 92%, respectively. A risk profile including nine predictors that can easily be assessed seems to be a useful tool for the identification of community-dwelling elderly with a high risk of recurrent falling. © International Osteoporosis Foundation and National Osteoporosis Foundation 2006

    Semi-viviparous embryo development and dehydrin expression in the mangrove Rhizophora mucronata Lam.

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    Rhizophora mucronata Lam. is a tropical mangrove with semi-viviparous (cotyledon body protrusion before shedding), non-quiescent and non-desiccating (recalcitrant) seeds. As recalcitrance has been thought to relate to the absence of desiccation-related proteins such as dehydrins, we for the first time systematically described and classified embryogenesis in R. mucronata and assessed the presence of dehydrin-like proteins. Embryogenesis largely follows the classic pattern till stage eight, the torpedo stage, with the formation of a cotyledonary body. Ovule and embryo express radical adaptations to semi-vivipary in the saline environment: (1) A large, highly vacuolated and persistent endosperm without noticeable food reserves that envelopes the developing embryo. (2) Absence of vascular tissue connections between embryo and maternal tissue, but, instead, transfer layers in between endosperm and integument and endosperm and embryo. Dehydrin-like proteins (55–65 kDa) were detected by the Western analysis, in the ovules till stage 10 when the integuments are dehisced. An additional 50 kDa band was detected at stages 6–8. Together these results suggest a continuous flow of water with nutrients from the integument via the endosperm to the embryo, circumventing the vascular route and probably suppressing the initially induced dehydrin expression

    Predicting the Impact of Climate Change on Threatened Species in UK Waters

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    Global climate change is affecting the distribution of marine species and is thought to represent a threat to biodiversity. Previous studies project expansion of species range for some species and local extinction elsewhere under climate change. Such range shifts raise concern for species whose long-term persistence is already threatened by other human disturbances such as fishing. However, few studies have attempted to assess the effects of future climate change on threatened vertebrate marine species using a multi-model approach. There has also been a recent surge of interest in climate change impacts on protected areas. This study applies three species distribution models and two sets of climate model projections to explore the potential impacts of climate change on marine species by 2050. A set of species in the North Sea, including seven threatened and ten major commercial species were used as a case study. Changes in habitat suitability in selected candidate protected areas around the UK under future climatic scenarios were assessed for these species. Moreover, change in the degree of overlap between commercial and threatened species ranges was calculated as a proxy of the potential threat posed by overfishing through bycatch. The ensemble projections suggest northward shifts in species at an average rate of 27 km per decade, resulting in small average changes in range overlap between threatened and commercially exploited species. Furthermore, the adverse consequences of climate change on the habitat suitability of protected areas were projected to be small. Although the models show large variation in the predicted consequences of climate change, the multi-model approach helps identify the potential risk of increased exposure to human stressors of critically endangered species such as common skate (Dipturus batis) and angelshark (Squatina squatina)
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