4,259 research outputs found

    Considerations for the development of agility during childhood and adolescence

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    Despite being recognized as an essential component of sports performance, agility development in youths is largely under-researched. this article reviews the evidence examining the effects of growth, maturation and training on both change of direction speed and cognitive processing in children and adolescents, and how combined, these factors may influence agility. training guidelines are provided to help strength and conditioning coaches prescribe agility training for youths at different stages of maturation, in a safe and effective manner

    Direct approach to the problem of strong local minima in Calculus of Variations

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    The paper introduces a general strategy for identifying strong local minimizers of variational functionals. It is based on the idea that any variation of the integral functional can be evaluated directly in terms of the appropriate parameterized measures. We demonstrate our approach on a problem of W^{1,infinity} weak-* local minima--a slight weakening of the classical notion of strong local minima. We obtain the first quasiconvexity-based set of sufficient conditions for W^{1,infinity} weak-* local minima.Comment: 26 pages, no figure

    Epitaxial Stabilization of Ultrathin Films of Rare-Earth Nickelates

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    We report on the synthesis of ultrathin films of highly distorted EuNiO3 (ENO) grown by interrupted pulse laser epitaxy on YAlO3 (YAO) substrates. Through mapping the phase space of nickelate thin film epitaxy, the optimal growth temperatures were found to scale linearly with the Goldschmidt tolerance factor. Considering the gibbs energy of the expanding film, this empirical trend is discussed in terms of epitaxial stabilization and the escalation of the lattice energy due to lattice distortions and decreasing symmetry. These findings are fundamental to other complex oxide perovskites, and provide a route to the synthesis of other perovskite structures in ultrathin-film form.Comment: 7 pages, 3 figure

    Analysis of parallel process in HVAC systems using deep autoencoders

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    P. 15-26Heating, Ventilation, and Air Conditioning (HVAC) systems are generally built in a modular manner, comprising several identical subsystems in order to achieve their nominal capacity. These parallel subsystems and elements should have the same behavior and, therefore, differences between them can reveal failures and inefficiency in the system. The complexity in HVAC systems comes from the number of variables involved in these processes. For that reason, dimensionality reduction techniques can be a useful approach to reduce the complexity of the HVAC data and study their operation. However, for most of these techniques, it is not possible to project new data without retraining the projection and, as a result, it is not possible to easily compare several projections. In this paper, a method based on deep autoencoders is used to create a reference model with a HVAC system and new data is projected using this model to be able to compare them. The proposed approach is applied to real data from a chiller with 3 identical compressors at the Hospital of LeĂłnS

    Sibling comparisons elucidate the associations between educational attainment polygenic scores and alcohol, nicotine and cannabis.

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    Background and aimsThe associations between low educational attainment and substance use disorders (SUDs) may be related to a common genetic vulnerability. We aimed to elucidate the associations between polygenic scores for educational attainment and clinical criterion counts for three SUDs (alcohol, nicotine and cannabis).DesignPolygenic association and sibling comparison methods. The latter strengthens inferences in observational research by controlling for confounding factors that differ between families.SettingSix sites in the United States.ParticipantsEuropean ancestry participants aged 25 years and older from the Collaborative Study on the Genetics of Alcoholism (COGA). Polygenic association analyses included 5582 (54% female) participants. Sibling comparisons included 3098 (52% female) participants from 1226 sibling groups nested within the overall sample.MeasurementsOutcomes included criterion counts for DSM-5 alcohol use disorder (AUDSX), Fagerström nicotine dependence (NDSX) and DSM-5 cannabis use disorder (CUDSX). We derived polygenic scores for educational attainment (EduYears-GPS) using summary statistics from a large (> 1 million) genome-wide association study of educational attainment.FindingsIn polygenic association analyses, higher EduYears-GPS predicted lower AUDSX, NDSX and CUDSX [P < 0.01, effect sizes (R2 ) ranging from 0.30 to 1.84%]. These effects were robust in sibling comparisons, where sibling differences in EduYears-GPS predicted all three SUDs (P < 0.05, R2 0.13-0.20%).ConclusionsIndividuals who carry more alleles associated with educational attainment tend to meet fewer clinical criteria for alcohol, nicotine and cannabis use disorders, and these effects are robust to rigorous controls for potentially confounding factors that differ between families (e.g. socio-economic status, urban-rural residency and parental education)

    Ginzburg-Landau model with small pinning domains

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    We consider a Ginzburg-Landau type energy with a piecewise constant pinning term aa in the potential (a2−∣u∣2)2(a^2 - |u|^2)^2. The function aa is different from 1 only on finitely many disjoint domains, called the {\it pinning domains}. These pinning domains model small impurities in a homogeneous superconductor and shrink to single points in the limit →ˇ0\v\to0; here, \v is the inverse of the Ginzburg-Landau parameter. We study the energy minimization in a smooth simply connected domain Ω⊂C\Omega \subset \mathbb{C} with Dirichlet boundary condition gg on \d \O, with topological degree {\rm deg}_{\d \O} (g) = d >0. Our main result is that, for small \v, minimizers have dd distinct zeros (vortices) which are inside the pinning domains and they have a degree equal to 1. The question of finding the locations of the pinning domains with vortices is reduced to a discrete minimization problem for a finite-dimensional functional of renormalized energy. We also find the position of the vortices inside the pinning domains and show that, asymptotically, this position is determined by {\it local renormalized energy} which does not depend on the external boundary conditions.Comment: 39 page

    Experience with chronic haemodialysis in Johannesburg

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    Since 1966 the treatment for patients with end-stage renal disease in Johannesburg has primarily been renal transplantation. This has required an adequate programme of regular dialysis. All patients were treated at the central hospital or at two small satellite units. A total of 158 patients, mean age 34,2 years (88 males) have been dialysed. The mean duration on dialysis prior to transplantation was 5,6 months (range 1 week - 23 months). The commonest cause of renal failure in males was chronic glomerulonephritis (63%), whereas in females it was analgesic nephropathy (39%). Twenty-seven patients (17%) died while on dialysis, including 6 who had had unsuccessful transplantations. Renal osteodystrophy was diagnosed in 30% of the patients. Hepatitis has been endemic among both patients and staff. Nephrectomies were done in 106 patients. Ten patients had operations for peptic ulcer and 5 parathyroidectomies were performed. The number of patients unsuccessfully transplanted, or who died, was less than the number of new patients requiring treatment. In addition, an increasing proportion of patients have become 'relatively untransplaotable'. This has led to overloading of facilities.S. Afr. Med. J., 48, 1821 (1974

    Acoustic Energy and Momentum in a Moving Medium

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    By exploiting the mathematical analogy between the propagation of sound in a non-homogeneous potential flow and the propagation of a scalar field in a background gravitational field, various wave ``energy'' and wave ``momentum'' conservation laws are established in a systematic manner. In particular the acoustic energy conservation law due to Blokhintsev appears as the result of the conservation of a mixed co- and contravariant energy-momentum tensor, while the exchange of relative energy between the wave and the mean flow mediated by the radiation stress tensor, first noted by Longuet-Higgins and Stewart in the context of ocean waves, appears as the covariant conservation of the doubly contravariant form of the same energy-momentum tensor.Comment: 25 Pages, Late
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