4,338 research outputs found

    The influence of the electronic specific heat on swift heavy ion irradiation simulations of silicon

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    The swift heavy ion (SHI) irradiation of materials is often modelled using the two-temperature model. While the model has been successful in describing SHI damage in metals, it fails to account for the presence of a bandgap in semiconductors and insulators. Here we explore the potential to overcome this limitation by explicitly incorporating the influence of the bandgap in the parameterisation of the electronic specific heat for Si. The specific heat as a function of electronic temperature is calculated using finite temperature density functional theory with three different exchange correlation functionals, each with a characteristic bandgap. These electronic temperature dependent specific heats are employed with two-temperature molecular dynamics to model ion track creation in Si. The results obtained using a specific heat derived from density functional theory showed dramatically reduced defect creation compared to models that used the free electron gas specific heat. As a consequence, the track radii are smaller and in much better agreement with experimental observations. We also observe a correlation between the width of the band gap and the track radius, arising due to the variation in the temperature dependence of the electronic specific heat

    Patterns of recruitment and injury in a heterogeneous airway network model

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    In respiratory distress, lung airways become flooded with liquid and may collapse due to surface-tension forces acting on air-liquid interfaces, inhibiting gas exchange. This pa- per proposes a mathematical multiscale model for the mechanical ventilation of a network of occluded airways, where air is forced into the network at a fixed tidal volume, allowing investigation of optimal recruitment strategies. The temporal response is derived from mechanistic models of individual airway reopening, incorporating feedback on the airway pressure due to recruitment. The model accounts for stochastic variability in airway di- ameter and stiffness across and between generations. For weak heterogeneity, the network is completely ventilated via one or more avalanches of recruitment (with airways recruited in quick succession), each characterised by a transient decrease in the airway pressure; avalanches become more erratic for airways that are initially more flooded. However, the time taken for complete ventilation of the network increases significantly as the network becomes more heterogeneous, leading to increased stresses on airway walls. The model predicts that the most peripheral airways are most at risk of ventilation-induced damage. A positive-end-expiratory pressure (PEEP) reduces the total recruitment time but at the cost of larger stresses exerted on airway walls

    Atomic transition frequencies, isotope shifts, and sensitivity to variation of the fine structure constant for studies of quasar absorption spectra

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    Theories unifying gravity with other interactions suggest spatial and temporal variation of fundamental "constants" in the Universe. A change in the fine structure constant, alpha, could be detected via shifts in the frequencies of atomic transitions in quasar absorption systems. Recent studies using 140 absorption systems from the Keck telescope and 153 from the Very Large Telescope, suggest that alpha varies spatially. That is, in one direction on the sky alpha seems to have been smaller at the time of absorption, while in the opposite direction it seems to have been larger. To continue this study we need accurate laboratory measurements of atomic transition frequencies. The aim of this paper is to provide a compilation of transitions of importance to the search for alpha variation. They are E1 transitions to the ground state in several different atoms and ions, with wavelengths ranging from around 900 - 6000 A, and require an accuracy of better than 10^{-4} A. We discuss isotope shift measurements that are needed in order to resolve systematic effects in the study. The coefficients of sensitivity to alpha-variation (q) are also presented.Comment: Includes updated version of the "alpha line" lis

    Exercise and GLUT4 in human subcutaneous adipose tissue

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    To examine the effect of acute and chronic exercise on adipose tissue GLUT4 expression, a total of 20 healthy, male subjects performed one of two studies. Ten subjects performed cycle ergometer exercise for 60 min at 73 ± 2% VO2 peak and abdominal adipose tissue samples were obtained immediately before and after exercise and after 3 h of recovery. Another 10 subjects completed 10 days of exercise training, comprising a combination of six sessions of 60 min at 75% VO2 peak and four sessions of 6 × 5 min at 90% VO2 peak, separated by 3 min at 40% VO2 peak. Abdominal adipose tissue and vastus lateralis muscle samples were obtained before training and 24 h after the last training session. A single bout of exercise did not change adipose tissue GLUT4 mRNA; however, there was a small, but significant, reduction in adipose tissue GLUT4 protein expression 3 h after exercise. There were no changes in adipose tissue GLUT4 or COX‐IV expression following exercise training. In contrast, skeletal muscle GLUT4 and COX‐IV were increased by 47% and 44%, respectively following exercise training. The exercise training‐induced increase in GLUT4 expression was similar in both type I and type IIa single muscle fibers. Our results indicate that neither a single exercise bout, nor 10 days of exercise training, increased adipose tissue GLUT4, in contrast with the increases observed in skeletal muscle GLUT4 expression

    Mental health challenges facing male survivors of child sexual abuse: implications for mental health nurses

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    Child sexual abuse (CSA) is an issue of epidemic proportions in the United Kingdom (UK) and an international public health problem. Evidence suggests that in the UK one in twenty children have been sexually abused, with one in three not telling anyone about it at the time of the abuse. Conservative estimates suggest that around one in six men have experienced sexual abuse before the age of 18. CSA has been correlated with the development of numerous mental health problems, abused men often displaying externalising behaviours, including substance misuse, ‘risky’ sexual behaviours, anti-social behaviour, and offending. This paper reports on one aspect of a research study focusing specifically on male survivors of CSA and its effect on their mental health. Using narrative research, face to face interviews were used to collect the stories of four men who participated in the research. Interviews were audio-recorded and transcribed verbatim. Analysis used a two-phase approach; initially, each narrative was analysed as a whole, with an across transcripts analysis then being carried out identifying shared themes emerging from the individual stories. Whilst findings from the second phase of the analysis identifies four themes, it is the theme of ‘Blocking the Memories’ that is the focus for this paper. Making a valuable contribution to existent knowledge regarding the experiences of men who were sexually abused as children, this paper will help to inform mental health practitioners who are likely to deliver care to male survivors of CSA

    Exploring male survivors of childhood sexual abuse experiences of specialist counselling services

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    Global estimates suggest 5% to 10% of men report experience of childhood sexual abuse (CSA). However, male CSA is significantly underreported, with men being reluctant to disclose due to vulnerability, stigmatisation, homophobic responses, and fearing a loss of masculinity. A lack of research and service provision targeted towards men suggests male survivors of CSA are marginalised. This qualitative study, using a narrative approach, focused on four adult male survivors of CSA. The aim of the study was to explore their experiences of engaging in counselling and support services for CSA from non-statutory and voluntary organisations. Face-to-face narrative interviews were audio-recorded and transcribed verbatim. Analysis was undertaken using a two-phase approach; firstly, each narrative was analysed as a whole, secondly, an across transcripts analysis was carried out to identify shared themes and divergences that emerged from the individual stories. In this paper findings from the second phase of the analysis are presented. Three themes regarding male survivors’ experiences of specialist counselling services were identified; ‘Trust Me, I’m a Doctor,’ ‘Trust me, I’m a Counsellor,’ and ‘Counsellor or Mother?’ This is the first academic study focusing specifically on men’s experience of support for CSA in the United Kingdom from a service user perspective. Making an original contribution to the knowledge base regarding counselling experiences and the effectiveness of therapy for male CSA survivors, it will help to inform professional counselling services who are likely to come into contact with male survivors of CSA

    A western diet increases serotonin availability in rat small intestine

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    Diet-induced obesity is associated with changes in gastrointestinal function and induction of a mild inflammatory state. Serotonin (5-HT) containing enterochromaffin (EC) cells within the intestine respond to nutrients and are altered by inflammation. Thus, our aim was to characterize the uptake and release of 5-HT from EC cells of the rat ileum in a physiologically relevant model of diet-induced obesity. In chow-fed (CF) and Western diet-fed (WD) rats electrochemical methods were used to measure compression evoked (peak) and steady state (SS) 5-HT levels with fluoxetine used to block the serotonin reuptake transporter (SERT). The levels ofmRNAfor tryptophan hydroxylase 1 (TPH1) and SERT were determined by quantitative PCR, while EC cell numbers were determined immunohistochemically. In WD rats, the levels of 5-HT were significantly increased (SS: 19.2±3.7 ±M; peak: 73.5±14.1 ±M) compared with CF rats (SS: 12.3±1.8 ±M; peak: 32.2±7.2 ±M), while SERTdependent uptake of 5-HT was reduced (peak WD: 108% of control versus peak CF: 212% control). In WD rats, there was a significant increase in TPH1 mRNA, a decrease in SERT mRNA and protein, and an increase in EC cells. In conclusion, our data show that foods typical of a Western diet are associated with an increased 5-HT availability in the rat ileum. Increased 5-HT availability is driven by the up-regulation of 5-HT synthesis genes, decreased re-uptake of 5-HT, and increased numbers and/or 5-HT content of EC cells which are likely to cause altered intestinal motility and sensation in vivo. Copyright © 2010 The Endocrine Society. All rights reserved

    Body, Self and Consciousness according to TirumĆ«lar’s Tirumandiram: A comparative study with Kashmir ƚaivism

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    Tirumular’s Tirumandiram is the earliest known Tamil treatise on yoga. This text is considered to be both, a devotional work as well as a tantric text. Unlike other major Siddha compositions, Tirumandiram does not contain any section on medicinal preparations or alchemy. It is the only Tamil text where the sections are named tanáč­iram. In contrast to the popular pluralistic ƚaiva Siddhānta, Tirumandiram, one of the twelve Saiva cannons (tirumurai), is monistic in its philosophy. This study, while elaborating on the metaphysics of the text Tirumandiram, also examines the shared philosophical thoughts between the monistic Kashmir ƚaivism and Tamil Siddha mystics
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