Such a seemingly self-apparent notion as "risky sports" is widely used in social science literature. Through the in-depth analysis of this term, the purpose of this article is to examine a crucial ...step of the sociological research process: definition of concepts. After having underlined simplifications and paradoxes inherent in the common sense use of this term, we present an overview of its scientific uses and definitions. Some terminological difficulties soon appear, along with differing points of view and plural available conceptualizations. The critical, structural, subjectivist, culturalist, and systemic approaches can thus be differentiated. The choice made between these options entail methodological consequences that are also discussed. Two epistemological positions can eventually be adopted. On one hand, one can be in favour of the abandon of such a category, on account of its intrinsic shakiness, and because it is merely impossible to reach by consensus the one and only definition of "risky sports". On the other hand, one can acknowledge the polythetic nature of this term. The latter will then be easily observed through the specific constructions of "risky sports", as a scientific object, according to each research problematics. Cet article propose une réflexion sur l'acte de définition en sociologie, à travers l'analyse approfondie de la notion de « sport à risque ». Fréquemment mobilisée dans la littérature en sciences sociales, celle-ci semble généralement aller de soi, notamment parce qu'elle repose sur quelques sous-entendus empruntés au sens commun. Après avoir souligné les simplifications et paradoxes inhérents à cet usage spontané de l'appellation « sport à risque », nous avons entrepris un recensement de ses utilisations et définitions scientifiques. Apparaissent dès lors certaines difficultés terminologiques, des divergences de vue, et la pluralité des conceptualisations disponibles. Les approches critique, structurelle, subjectiviste, culturaliste et systémique ont ainsi pu être différentiées. Les conséquences méthodologiques des choix notionnels opérés par les chercheurs sont également présentées. Au terme de cette analyse, deux positions peuvent être adoptées : renoncer à l'usage d'une catégorie jugée fragile, en constatant l'impossibilité de parvenir à une définition sinon générique, partagée du risque sportif; ou admettre le caractère polythétique de cette appellation, se traduisant par des constructions spécifiques de l'objet « sport à risque » en fonction de chaque problématique de recherche.
The electronic band structures of Be and BeO have been measured by transmission electron momentum spectroscopy (EMS). The low atomic number of beryllium and the use of ultrathin solid films in these ...experiments reduce the probability of electron multiple scattering within the sample, resulting in very clean ‘benchmark’ measurements for the EMS technique. Experimental data are compared to tight-binding (LCAO) electronic structure calculations using Hartree–Fock , and local density (LDA-VWN), gradient corrected (PBE) and hybrid (PBE0) density functional theory. Overall, DFT calculations reproduce the EMS data for metallic Be reasonably well. PBE predictions for the valence bandwidth of Be are in excellent agreement with EMS data, provided the calculations employ a large basis set augmented with diffuse functions. For BeO, PBE calculations using a moderately sized basis set are in reasonable agreement with experiment, slightly underestimating the valence bandgap and overestimating the O(2s) and O(2p) bandwidths. The calculations also underestimate the EMS intensity of the O(2p) band around the Γ-point. Simulation of the effects of multiple scattering in the calculated oxide bandstructures do not explain these systematic differences.
Longitudinal population-based surveys are widely used in the health sciences to study patterns of change over time. In many of these data sets unique patient identifiers are not publicly available, ...making it impossible to link the repeated measures from the same individual directly. This poses a statistical challenge for making inferences about time trends because repeated measures from the same individual are likely to be positively correlated, i.e., although the time trend that is estimated under the naive assumption of independence is unbiased, an unbiased estimate of the variance cannot be obtained without knowledge of the subject identifiers linking repeated measures over time. We propose a simple method for obtaining a conservative estimate of variability for making inferences about trends in proportions over time, ensuring that the type I error is no greater than the specified level. The method proposed is illustrated by using longitudinal data on diabetes hospitalization proportions in South Carolina.
Molecular dynamics simulations of the diffusion process in ordered B2 NiAl at high temperature were performed using an embedded atom interatomic potential. Diffusion occurs through a variety of ...cyclic mechanisms that accomplish the motion of the vacancy through nearest neighbor jumps restoring order to the alloy at the end of the cycle. The traditionally postulated six-jump cycle is only one of the various cycles observed and some of these are quite complex. A detailed sequential analysis of the observed six-jump cycles was performed and the results are analyzed in terms of the activation energies for individual jumps calculated using molecular statics simulations.
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