1,637 research outputs found
L'eĢconomie de mouvement en course aĢ pied : comparaison entre mesures objectives et eĢvaluations subjectives par l'entraineur speĢcialiseĢ
L'eĢconomie de mouvement en course aĢ pied est un parameĢtre essentiel pour la performance et de nouvelles meĢthodes d'entrainement essaient aujourd'hui de le cibler. La mesure de cette eĢconomie de course se fait habituellement en laboratoire par la consommation d'oxygeĢne neĢcessaire au deĢplacement aĢ une vitesse donneĢe sous-maximale. La question de cette eĢtude est de voir dans quelle mesure l'oeil averti d'un entraineur en course aĢ pied peut estimer l'eĢconomie de course, en comparaison aĢ une mesure objective de la consommation d'oxygeĢne.
Au total, 22 coureurs de niveaux diffeĢrents et 9 entraineurs ont pris part aĢ cette eĢtude. Elle s'est dans un premier temps deĢrouleĢe avec les coureurs sur le site du Stade de Coubertin aĢ Vidy (VD). Cette eĢtape a permis les enregistrements videĢo et la mesure de leur eĢconomie de course respective ainsi que l'eĢtablissement des notes d'eĢconomies de reĢfeĢrence. Dans un second temps, les eĢvaluations par les entraineurs ont eĢteĢ faites en ligne sur la base des videĢos.
Les reĢsultats ont eĢteĢ traiteĢs de telle manieĢre aĢ obtenir des coefficients (correĢlation intraclasse et kappa de Cohen) estimant la concordance des eĢvaluations de chaque entraineur avec les notes de reĢfeĢrence. La concordance au sein du groupe d'entraineurs a aussi eĢteĢ eĢvalueĢe.
L'eĢtude preĢsente en conclusion des reĢsultats eĢtonnants, remettant en question la capaciteĢ des entraineurs aĢ eĢvaluer l'eĢconomie de course de coureurs issus d'un groupe de performances heĢteĢrogeĢnes par rapport aĢ des mesures objectives. En revanche, l'eĢtude preĢsente des reĢsultats indiquant une bonne concordance des entraineurs entre eux
Atomic Energy Relations. I
A simple method for the calculation of approximate energies of atomic levels is presented in this paper. It is based on the derivation of linear relations which express the unknown energy in terms of observed energy values of the atom and its ions. It is shown that the degree of approximation increases with the amount of experimental data available for use in the calculation and also how the best formulas can be obtained for each case. Several tables are given containing formulas for configurations involving s and p electrons. They are applied to the spectra of carbon, nitrogen and oxygen and the energy values so determined are compared with those known from observations. In an appendix the method of approximation is compared with the quantum mechanical perturbation method
Two-body effects in the decay rate of atomic levels
Recoil corrections to the atomic decay rate are considered in the order of
Zm/M . The expressions are treated exactly without any expansion over Z alpha.
The expressions obtained are valid both for muonic atoms (for which they
contribute on the level of a few percent in high Z ions) and for electronic
atoms. Explicit results for Lyman-alpha transitions for low-Z of the order
(Zm/M)(Z alpha)^2 are also presented.Comment: 5 pages, 1 table, email: [email protected]
The Nuclear Moments of Indium and Gallium
We have studied the resonance lines of indium using a Fabry-Perot interferometer and find indeed that Ī»4101 (5p^2P_(1/2)ā6s^2'S_(1/2) has four distinct components as reported by Jackson, which, while it does not determine the nuclear moment, requires that it be greater than 1/2
Projecting the continental accumulation of alien species through to 2050
Biological invasions have steadily increased over recent centuries. However, we still lack a clear expectation about future trends in alien species numbers. In particular, we do not know whether alien species will continue to accumulate in regional floras and faunas, or whether the pace of accumulation will decrease due to the depletion of native source pools. Here, we apply a new model to simulate future numbers of alien species based on estimated sizes of source pools and dynamics of historical invasions, assuming a continuation of processes in the future as observed in the past (a businessāasāusual scenario). We first validated performance of different model versions by conducting a backācasting approach, therefore fitting the model to alien species numbers until 1950 and validating predictions on trends from 1950 to 2005. In a second step, we selected the best performing model that provided the most robust predictions to project trajectories of alien species numbers until 2050. Altogether, this resulted in 3,790 stochastic simulation runs for 38 taxonācontinent combinations. We provide the first quantitative projections of future trajectories of alien species numbers for seven major taxonomic groups in eight continents, accounting for variation in sampling intensity and uncertainty in projections. Overall, established alien species numbers per continent were predicted to increase from 2005 to 2050 by 36%. Particularly, strong increases were projected for Europe in absolute (+2,543 Ā± 237 alien species) and relative terms, followed by Temperate Asia (+1,597 Ā± 197), Northern America (1,484 Ā± 74) and Southern America (1,391 Ā± 258). Among individual taxonomic groups, especially strong increases were projected for invertebrates globally. Declining (but still positive) rates were projected only for Australasia. Our projections provide a first baseline for the assessment of future developments of biological invasions, which will help to inform policies to contain the spread of alien species
Formation of even-numbered hydrogen cluster cations in ultracold helium droplets
Neutral hydrogen clusters are grown in ultracold helium nanodroplets by successive pickup of hydrogen molecules. Even-numbered hydrogen cluster cations are observed upon electron-impact ionization with and without attached helium atoms and in addition to the familiar odd-numbered H(n)(+). The helium matrix affects the fragmentation dynamics that usually lead to the formation of overwhelmingly odd-numbered H(n)(+). The use of high-resolution mass spectrometry allows the unambiguous identification of even-numbered H(n)(+) up to n congruent to 120 by their mass excess that distinguishes them from He(n)(+), mixed He(m)H(n)(+), and background ions. The large range in size of these hydrogen cluster ions is unprecedented, as is the accuracy of their definition. Apart from the previously observed magic number n = 6, pronounced drops in the abundance of even-numbered cluster ions are seen at n = 30 and 114, which suggest icosahedral shell closures at H(6)(+)(H(2))(12) and H(6)(+)(H(2))(54). Possible isomers of H(6)(+) are identified at the quadratic configuration interaction with inclusion of single and double excitations (QCISD)/aug-cc-pVTZ level of theory (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3035833
Genes or Culture: Are Mitochondrial Genes Associated with Tool Use in Bottlenose Dolphins ( Tursiops sp.)?
Some bottlenose dolphins use marine sponges as foraging tools (āsponging'), which appears to be socially transmitted from mothers mainly to their female offspring. Yet, explanations alternative to social transmission have been proposed. Firstly, the propensity to engage in sponging might be due to differences in diving ability caused by variation of mitochondrial genes coding for proteins of the respiratory chain. Secondly, the cultural technique of sponging may have selected for changes in these same genes (or other autosomal ones) among its possessors. We tested whether sponging can be predicted by mitochondrial coding genes and whether these genes are under selection. In 29 spongers and 54 non-spongers from two study sites, the non-coding haplotype at the HVRI locus was a significant predictor of sponging, whereas the coding mitochondrial genes were not. There was no evidence of selection in the investigated genes. Our study shows that mitochondrial gene variation is unlikely to be a viable alternative to cultural transmission as a primary driver of tool use in dolphin
Application of the Socio-Economic Impact Classification for Alien Taxa (SEICAT) to a global assessment of alien bird impacts
We use a recently proposed framework, the Socio-Economic Impact Classification for Alien Taxa (SEICAT) to undertake the first global assessment of the impacts of alien birds on human well-being. A review of the published literature and online resources was undertaken to collate information on the reported socio-economic impacts of 415 bird species with self-sustaining alien populations worldwide. These data were then categorised following the SEICAT guidelines. Impact data were found for 57 (14%) of the 415 alien bird species in this study. All but two of these species were found to have minor impacts on human well-being. The most significant threat to human well-being posed by alien birds may be associated with their impacts on aviation safety. About two-thirds of the impact data found described agricultural impacts. No data were found describing disease transmission impacts on humans. We lack data for developing regions of the world: this is of concern as alien species can threaten livelihoods in developing countries, particularly by affecting agricultural production and hence food security. Most assessments were allocated a āLowā confidence score. This may be because SEICAT is a new framework, requiring data on the way in which alien species affect human well-being, as measured by changes to human activities: even where we do have data describing an alien bird impact, information on how profoundly this impact affects peopleās activities is currently rarely available
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