414 research outputs found

    Characterization of micro-mechanical deformation systems of magnesium based on energy minimization

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    The present paper is concerned with a variationally consistent approach suitable for the modeling of rate-independent crystal plasticity at ïŹnite strains including a Taylor-type phase transition. The method relies strongly on the variational structure of crystal plasticity theory, i.e., an incremental minimization principle can be derived in case of a fully associative model which allows to compute the unknown slip rates by computing the respective stationarity conditions. More precisely, all internal variables are obtained by minimizing the stress power. For modeling twinning, which is the second important physical process governing the deformation behavior of magnesium, a simple approach for phase transition based on volume averaging is proposed. In line with the modeling of the plastic slip, the proposed method is fully variational, i.e., phase transformation occurs, if this is energetically favorable. Comparisons of numerical results predicted by the novel model to experimental results show that the Taylor-type phase transition is able to capture the hardening transition corresponding to the initial and the twin phase realistically. The same can be observed for the hardening behavior of ordinary dislocation systems of magnesium characterized by means of the channel die test

    Quality of Drinking-water at Source and Point-ofconsumption\u2014 Drinking Cup As a High Potential Recontamination Risk: A Field Study in Bolivia

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    In-house contamination of drinking-water is a persistent problem in developing countries. This study aimed at identifying critical points of contamination and determining the extent of recontamination after water treatment. In total, 81 households were visited, and 347 water samples from their current sources of water, transport vessels, treated water, and drinking vessels were analyzed. The quality of water was assessed using Escherichia coli as an indicator for faecal contamination. The concentration of E. coli increased significantly from the water source [median=0 colony-forming unit (CFU)/100 mL, interquartile range (IQR: 0-13)] to the drinking cup (median=8 CFU/100 mL; IQR: 0-550; n=81, z=-3.7, p<0.001). About two-thirds (34/52) of drinking vessels were contaminated with E. coli. Although boiling and solar disinfection of water (SODIS) improved the quality of drinking-water (median=0 CFU/100 mL; IQR: 0-0.05), recontamination at the point-of-consumption significantly reduced the quality of water in the cups (median=8, IQR: 0-500; n=45, z=-2.4, p=0.015). Home-based interventions in disinfection of water may not guarantee health benefits without complementary hygiene education due to the risk of posttreatment contamination

    Bangladesh arsenic mitigation programs: lessons from the past

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    Ensuring access to safe drinking water by 2015 is a global commitment by the Millennium Development Goals (MDGs). In Bangladesh, significant achievements in providing safe water were made earlier by nationwide tubewell-installation programme. This achievement was overshadowed in 1993 by the presence of arsenic in underground water. A total of 6 million tubewells have been tested for arsenic since then, the results of which warranted immediate mitigation. Mitigation measures included tubewell testing and replacing; usage of deeper wells; surface water preservation and treatment; use of sanitary dug wells, river sand and pond sand filters; rainwater collection and storage; household-scale and large-scale arsenic filtrations; and rural pipeline water supply installation. Shallow tubewell installation was discouraged. Efforts have been made to increase people's awareness. This paper describes the lessons learned about mitigation efforts by the authors from experience of arsenic-related work. In spite of national mitigation plans and efforts, a few challenges still persist: inadequate coordination between stakeholders, differences in inter-sectoral attitudes, inadequate research to identify region-specific, suitable safe water options, poor quality of works by various implementing agencies, and inadequate dissemination of the knowledge and experiences to the people by those organizations. Issues such as long-time adaptation using ground water, poor surface water quality including bad smell and turbidity, and refusal to using neighbor's water have delayed mitigation measures so far. Region-specific mitigation water supply policy led by the health sector could be adopted with multisectoral involvement and responsibility. Large-scale piped water supply could be arranged through Public Private Partnerships (PPP) in new national approach

    The UK's Global Health Respiratory Network: Improving respiratory health of the world's poorest through research collaborations.

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    Respiratory disorders are responsible for considerable morbidity, health care utilisation, societal costs and approximately one in five deaths worldwide [1-4]. Yet, despite this substantial health and societal burden – which particularly affects the world’s poorest populations and as such is a major contributor to global health inequalities – respiratory disorders have historically not received the policy priority they warrant. For example, despite causing an estimated 1000 deaths per day, less than half of the world’s countries collect data on asthma prevalence (http://www.globalasthmareport.org/). This is true for both communicable and non-communicable respiratory disorders, many of which are either amenable to treatment or preventable

    Centerpoints: a link between optimization and convex geometry

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    We introduce a concept that generalizes several different notions of a “centerpoint” in the literature. We develop an oracle-based algorithm for convex mixed-integer optimization based on centerpoints. Further, we show that algorithms based on centerpoints are “best possible” in a certain sense. Motivated by this, we establish several structural results about this concept and provide efficient algorithms for computing these points

    We need to talk about manels: the problem of implicit gender bias in sport and exercise medicine.

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    In 2015, a website (www.allmalepanels.tumblr. com/) began documenting instances of all-male panels (colloquially known as a ‘manel’). This, along with the Twitter hashtag #manel, has helped drive recognition of the persistent and pervasive gender bias in the composition of experts assembled to present at conferences and other events. Recent social media discussions have similarly highlighted the prevalence of all-male panels in Sport and Exercise Medicine (SEM). While, to our knowledge, all-male panel trends in SEM have not yet formally been documented or published, one need look no further than SEM conference committees, keynote speaker lists, panels and other events to see that it exists in practice. Why, in 2018, is SEM and its related disciplines still failing to identify and acknowledge the role that implicit bias plays in the very structure of our own research, practice and education? SEM is, after all, a profession that contains experts, and serves populations, of all genders. This editorial will introduce the definition, implications and manifestations of implicit gender bias and then explore how the SEM community can begin to address this issue, advance the discussion and develop a more equitable global community

    Hip strength and range of motion: normal values from a professional football league

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    To determine the normal profiles for hip strength and range of motion (ROM) in a professional football league in Qatar, and examine the effect of leg dominance, age, past history of injury, and ethnicity on these profiles.Cross-sectional cohort study.Participants included 394 asymptomatic, male professional football players, aged 18-40 years. Strength was measured using a hand held dynamometer with an eccentric test in side-lying for hip adduction and abduction, and the squeeze test in supine with 45° hip flexion. Range of motion measures included: hip internal and external rotation in 90° flexion, hip IR in prone, bent knee fall out and hip abduction in side-lying. Demographic information was collected and the effect on the profiles was analysed using linear mixed models with repeated measures.Strength values (mean±SD) were: adduction=3.0±0.6Nm/kg, abduction=2.6±0.4Nm/kg, adduction/abduction ratio=1.2±0.2, Squeeze test=3.6±0.8N/kg. Range of motion values: internal rotation in flexion=32±8°, external rotation=38±8°, internal rotation in prone=38±8°, bent knee fall out=13±4.4cm, abduction in side-lying=50±7.3°. Leg dominance had no clinically relevant effect on these profiles. Multivariate analysis demonstrated that age had a minor influence on squeeze strength (-0.03N/kg/year), external rotation (-0.30°/year) and abduction range (-0.19°/year) but past history of injury, and ethnicity did not.Normal values are documented for hip strength and range of motion that can be used as reference profiles in the clinical assessment, screening, and management of professional football players. Leg dominance, recent past injury history and ethnicity do not need to be accounted for when using these profiles for comparison purposes

    Oxford consensus on primary cam morphology and femoroacetabular impingement syndrome: part 1—definitions, terminology, taxonomy and imaging outcomes

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    Introduction Primary cam morphology is a mostly benign bony prominence that develops at the femoral head-neck junction of the hip, but it is highly prevalent in many athlete populations. In the small proportion of athletes for whom it is not benign, the resulting hip osteoarthritis can be debilitating. Clinicians, athletes, patients and researchers do not yet agree on important primary cam morphology elements. We aimed to ascertain and improve the level of agreement on primary cam morphology definitions, terminology, taxonomy and imaging outcome measures. Methods To collect and aggregate informed opinions, an expert panel—the Young Athlete’s Hip Research Collaborative—rated primary cam morphology definition, terminology, taxonomy and imaging outcome statements through an online Delphi exercise followed by an online meeting to explore areas of tension and dissent. Reporting followed Conducting and REporting DElphi Studies. Results A diverse and inclusive Delphi panel (n=65 for rounds 1 and 2, representing 18 countries; 6 stakeholder groups; 40% women) agreed on 35 of 47 statements in 4 domains, while surfacing areas of tension and dissent. This Delphi panel agreed on four key issues essential to moving research and clinical care forward around primary cam morphology. They agreed on: (1) definition, confirming its conceptual attributes (tissue type, size, location, shape and ownership); (2) terminology—use ‘morphology’ and not terms with a negative connotation like ‘lesion’, ‘abnormality’ or ‘deformity’; (3) taxonomy, distinguishing between primary and secondary cam morphology, and (4) imaging outcomes, a continuous bone/cartilage alpha angle on radial femoral head-neck MRI for primary cam morphology aetiology research. Conclusion This consensus provides athletes, patients, clinicians and researchers with a strong foundation to guide more precise communication, better clinical decision-making and higher value research about primary cam morphology and its natural history

    Supermodular Functions on Finite Lattices

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    The supermodular order on multivariate distributions has many applications in financial and actuarial mathematics. In the particular case of finite, discrete distributions, we generalize the order to distributions on finite lattices. In this setting, we focus on the generating cone of supermodular functions because the extreme rays of that cone (modulo the modular functions) can be used as test functions to determine whether two random variables are ordered under the supermodular order. We completely determine the extreme supermodular functions in some special cases.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43343/1/11083_2005_Article_9026.pd
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