192 research outputs found

    Phase transition in ultrathin magnetic films with long-range interactions: Monte Carlo simulation of the anisotropic Heisenberg model

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    Ultrathin magnetic films can be modeled as an anisotropic Heisenberg model with long-range dipolar interactions. It is believed that the phase diagram presents three phases: An ordered ferromagnetic phase I, a phase characterized by a change from out-of-plane to in-plane in the magnetization II, and a high-temperature paramagnetic phase III. It is claimed that the border lines from phase I to III and II to III are of second order and from I to II is first order. In the present work we have performed a very careful Monte Carlo simulation of the model. Our results strongly support that the line separating phases II and III is of the BKT type.Comment: 7 page

    Polarization Modulation in Ferroelectric Organic Field-Effect Transistors

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    The polarization modulation effect of the gate dielectric on the performance of metal-oxide-semiconductor field-effect transistors has been investigated for more than a decade. However, there are no comparable studies in the area of organic field-effect transistors (FETs) using polymer ferroelectric dielectrics, where the effect of polarization rotation by 90 is examined on the FET characteristics. We demonstrate the effect of polarization rotation in a relaxor ferroelectric dielectric, poly(vinylidene fluoride trifluorethylene) (PVDF-TrFE), on the performance of small-molecule-based organic FETs. The subthreshold swing and other transistor parameters in organic FETs can be controlled in a reversible fashion by switching the polarization direction in the PVDF-TrFE layer. X-ray diffraction and electron microscopy images from PVDF-TrFE reveal changes in the ferroelectric phase and domain size, respectively, upon rotating the external electric field by 90. The structural changes corroborate density-functional-theoretical studies of an oligomer of the ferroelectric molecule in the presence of an applied electric field. The strategies enumerated here for polarization orientation of the polymer ferroelectric dielectric are applicable for a wide range of polymeric and organic transistors

    Identifying research priorities for effective retention strategies in clinical trials

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    Background The failure to retain patients or collect primary-outcome data is a common challenge for trials and reduces the statistical power and potentially introduces bias into the analysis. Identifying strategies to minimise missing data was the second highest methodological research priority in a Delphi survey of the Directors of UK Clinical Trial Units (CTUs) and is important to minimise waste in research. Our aim was to assess the current retention practices within the UK and priorities for future research to evaluate the effectiveness of strategies to reduce attrition. Methods Seventy-five chief investigators of NIHR Health Technology Assessment (HTA)-funded trials starting between 2009 and 2012 were surveyed to elicit their awareness about causes of missing data within their trial and recommended practices for improving retention. Forty-seven CTUs registered within the UKCRC network were surveyed separately to identify approaches and strategies being used to mitigate missing data across trials. Responses from the current practice surveys were used to inform a subsequent two-round Delphi survey with registered CTUs. A consensus list of retention research strategies was produced and ranked by priority. Results Fifty out of seventy-five (67%) chief investigators and 33/47 (70%) registered CTUs completed the current practice surveys. Seventy-eight percent of trialists were aware of retention challenges and implemented strategies at trial design. Patient-initiated withdrawal was the most common cause of missing data. Registered CTUs routinely used newsletters, timeline of participant visits, and telephone reminders to mitigate missing data. Whilst 36 out of 59 strategies presented had been formally or informally evaluated, some frequently used strategies, such as site initiation training, have had no research to inform practice. Thirty-five registered CTUs (74%) participated in the Delphi survey. Research into the effectiveness of site initiation training, frequency of patient contact during a trial, the use of routinely collected data, the frequency and timing of reminders, triggered site training and the time needed to complete questionnaires was deemed critical. Research into the effectiveness of Christmas cards for site staff was not of critical importance. Conclusion The surveys of current practices demonstrates that a variety of strategies are being used to mitigate missing data but with little evidence to support their use. Six retention strategies were deemed critically important within the Delphi survey and should be a primary focus of future retention research

    The role of social capital in participatory arts for wellbeing: findings from a qualitative systematic review

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    BACKGROUND:Social capital is often cited as shaping impacts of participatory arts, although the concept has not been systematically mapped in arts, health and wellbeing contexts. In wider health inequalities research, complex, differential, and sometimes negative impacts of social capital have been recognised. METHODS:This paper maps of social capital concepts in qualitative research as part of the UK What Works for Wellbeing evidence review programme on culture, sport and wellbeing. RESULTS:Studies often cite positive impacts of bonding and, to a lesser extent, bridging social capital. However, reported challenges suggest the need for a critical approach. Forms of linking social capital, such as reframing and political engagement to address social divisions, are less often cited but may be important in participatory arts and wellbeing. CONCLUSIONS:Future research should further specify dimensions of social capital as well as their nuanced effects in arts, and wellbeing contexts

    What works for wellbeing in culture and sport? Report of a DELPHI process to support coproduction and establish principles and parameters of an evidence review

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    Aims: There is a growing recognition of the ways in which culture and sport can contribute to wellbeing. A strong evidence base is needed to support innovative service development and a 3-year research programme is being undertaken to capture best evidence of wellbeing impacts and outcomes of cultural and sporting activities in order to inform UK policy and practice. This article provides an overview of methods and findings from an initial coproduction process with key stakeholders that sought to explore and agree principles and parameters of the evidence review for culture, sport and wellbeing (CSW). Methods: A two-stage DELPHI process was conducted with a purposeful sample of 57 stakeholders between August and December 2015. Participants were drawn from a range of culture and sport organisations and included commissioners and managers, policy makers, representatives of service delivery organisations (SDOs) and scholars. The DELPHI 1 questionnaire was developed from extensive consultation in July and August 2015. It explored definitions of wellbeing, the role of evidence, quality assessment, and the culture and sport populations, settings and interventions that are most likely to deliver wellbeing outcomes. Following further consultation, the results, presented as a series of ranked statements, were sent back to participants (DELPHI 2), which allowed them to reflect on and, if they wished, express agreement or disagreement with the emerging consensus. Results: A total of 40 stakeholders (70.02%) responded to the DELPHI questionnaires. DELPHI 1 mapped areas of agreement and disagreement, confirmed in DELPHI 2. The exercise drew together the key priorities for the CSW evidence review. Conclusion: The DELPHI process, in combination with face-to-face deliberation, enabled stakeholders to engage in complex discussion and express nuanced priorities while also allowing the group to come to an overall consensus and agree outcomes. The results will inform the CSW evidence review programme until its completion in March 2018

    Metabolic Signatures of Lung Cancer in Biofluids: NMR-Based Metabonomics of Blood Plasma

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    In this work, the variations in the metabolic profile of blood plasma from lung cancer patients and healthy controls were investigated through NMR-based metabonomics, to assess the potential of this approach for lung cancer screening and diagnosis. PLS-DA modeling of CPMG spectra from plasma, subjected to Monte Carlo Cross Validation, allowed cancer patients to be discriminated from controls with sensitivity and specificity levels of about 90%. Relatively lower HDL and higher VLDL + LDL in the patients' plasma, together with increased lactate and pyruvate and decreased levels of glucose, citrate, formate, acetate, several amino acids (alanine, glutamine, histidine, tyrosine, valine), and methanol, could be detected. These changes were found to be present at initial disease stages and could be related to known cancer biochemical hallmarks, such as enhanced glycolysis, glutaminolysis, and gluconeogenesis, together with suppressed Krebs cycle and reduced lipid catabolism, thus supporting the hypothesis of a systemic metabolic signature for lung cancer. Despite the possible confounding influence of age, smoking habits, and other uncontrolled factors, these results indicate that NMR-based metabonomics of blood plasma can be useful as a screening tool to identify suspicious cases for subsequent, more specific radiological tests, thus contributing to improved disease management.ERDF - Competitive Factors Thematic Operational ProgrammeFCT/PTDC/ QUI/68017/2006FCOMP-01-0124-FEDER-007439SFRH/BD/ 63430/2009National UNESCO Committee - L'Oréal Medals of Honor for Women in Science 200Portuguese National NMR Network - RNRM

    Qualitative findings from a systematic review: Visual arts engagement for adults with mental health conditions

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    This article reports on an investigation of the effects of ‘visual arts’-based programmes on subjective well-being (SWB) outcomes for adults with mental health conditions. In a systematic review, electronic databases were searched for articles published from January 2007 to April 2017. Grey literature completed from January 2014 to April 2017 was also considered. Six published articles of mostly moderate quality and six evaluation reports (grey literature) covering a wide range of visual arts practice, population groups and settings were included. Key themes emerged connected to the concept of ‘bonding’, sense of belonging, appreciation of self-identity and the confidence that engagement in visual arts can facilitate. The overall conclusion supports that visual arts have the potential to enhance the SWB of adults with mental health conditions. The evidence is relatively limited in terms of scope and quality ‐ increased funding across sectors should be secured to support more extensive and long-term research.ESRC, UK Research and Innovation Project. Project Reference: ES/N003721/

    Sport and dance interventions for healthy young people (15-24 years) to promote subjective wellbeing: A systematic review

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    © Article author(s) (or their employer(s). Objective: to review and assess effectiveness of sport and dance participation on subjective wellbeing outcomes among 15-24 year olds. Design: Systematic review. Methods: We searched for studies published in any language between January 2006 and September 2016 on PsychINFO, Ovid MEDLINE, Eric, Web of Science (Arts and Humanities Citation Index, Social Science and Science Citation Index), Scopus, PILOTS, CINAHL, SPORTDiscus, and International Index to Performing Arts. Additionally, we searched for unpublished (grey) literature via an online call for evidence, expert contribution, searches of key organisation websites and the British Library EThOS database, and a keyword Google search. Published studies of sport or dance interventions for healthy 15-24-year olds where subjective wellbeing was measured were included. Studies were excluded if participants were paid professionals or elite athletes, or if the intervention was clinical sport/dance therapy. Two researchers extracted data and assessed strength and quality of evidence using criteria in the What Works Centre for Wellbeing methods guide and GRADE, and using standardised reporting forms. Due to clinical heterogeneity between studies, meta-analysis was not appropriate. Grey literature in the form of final evaluation reports on empirical data relating to sport or dance interventions were included. Results: Eleven out of 6587 articles were included (7 RCTs and 1 cohort study, and three unpublished grey evaluation reports). Published literature suggests meditative physical activity (yoga and Baduanjin Qigong) and group-based or peer-supported sport and dance has some potential to improve subjective wellbeing. Grey literature suggests sport and dance improve subjective wellbeing but identify negative feelings of competency and capability. The amount and quality of published evidence on sport and dance interventions to enhance subjective wellbeing is low. Conclusions: Meditative activities, group and peer supported sport and dance may promote subjective wellbeing enhancement in youth. Evidence is limited. Better designed studies are needed.Economic and Social Research Council (ES/ NOO3721/1)
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