L'économie de mouvement en course à pied : comparaison entre mesures objectives et évaluations subjectives par l'entraineur spécialisé

L'économie de mouvement en course à pied est un paramètre essentiel pour la performance et de nouvelles méthodes d'entrainement essaient aujourd'hui de le cibler. La mesure de cette économie de course se fait habituellement en laboratoire par la consommation d'oxygène nécessaire au déplacement à une vitesse donnée sous-maximale. La question de cette étude est de voir dans quelle mesure l'oeil averti d'un entraineur en course à pied peut estimer l'économie de course, en comparaison à une mesure objective de la consommation d'oxygène. Au total, 22 coureurs de niveaux différents et 9 entraineurs ont pris part à cette étude. Elle s'est dans un premier temps déroulée avec les coureurs sur le site du Stade de Coubertin à Vidy (VD). Cette étape a permis les enregistrements vidéo et la mesure de leur économie de course respective ainsi que l'établissement des notes d'économies de référence. Dans un second temps, les évaluations par les entraineurs ont été faites en ligne sur la base des vidéos. Les résultats ont été traités de telle manière à obtenir des coefficients (corrélation intraclasse et kappa de Cohen) estimant la concordance des évaluations de chaque entraineur avec les notes de référence. La concordance au sein du groupe d'entraineurs a aussi été évaluée. L'étude présente en conclusion des résultats étonnants, remettant en question la capacité des entraineurs à évaluer l'économie de course de coureurs issus d'un groupe de performances hétérogènes par rapport à des mesures objectives. En revanche, l'étude présente des résultats 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

Separations in Hyperfine Structure

The quantum mechanics conception of a spinning electron in an s state makes it probable that its interaction energy with a nuclear moment i is simply proportional to the average of is cos (is). Expressions for this average cosine have been obtained and applied to different examples. In more complicated cases it can only be said that the interaction energy is proportional to ij cos (ij), which makes the interval rule hold for hyperfine structure

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 λ4101 (5p^2P_(1/2)—6s^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 business‐as‐usual scenario). We first validated performance of different model versions by conducting a back‐casting 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 taxon–continent 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 ± 237 alien species) and relative terms, followed by Temperate Asia (+1,597 ± 197), Northern America (1,484 ± 74) and Southern America (1,391 ± 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

Exciton lifetime in InAs/GaAs quantum dot molecules

The exciton lifetimes $T_1$ in arrays of InAs/GaAs vertically coupled quantum dot pairs have been measured by time-resolved photoluminescence. A considerable reduction of $T_1$ by up to a factor of $\sim$ 2 has been observed as compared to a quantum dots reference, reflecting the inter-dot coherence. Increase of the molecular coupling strength leads to a systematic decrease of $T_1$ with decreasing barrier width, as for wide barriers a fraction of structures shows reduced coupling while for narrow barriers all molecules appear to be well coupled. The coherent excitons in the molecules gain the oscillator strength of the excitons in the two separate quantum dots halving the exciton lifetime. This superradiance effect contributes to the previously observed increase of the homogeneous exciton linewidth, but is weaker than the reduction of $T_2$. This shows that as compared to the quantum dots reference pure dephasing becomes increasingly important for the molecules

The generic impact scoring system (GISS): a standardized tool to quantify the impacts of alien species.

Alien species can exert negative environmental and socio-economic impacts. Therefore, administrations from different sectors are trying to prevent further introductions, stop the spread of established species, and apply or develop programs to mitigate their impact, to contain the most harmful species, or to eradicate them if possible. Often it is not clear which of the numerous alien species are most important in terms of damage, and therefore, impact scoring systems have been developed to allow a comparison and thus prioritization of species. Here, we present the generic impact scoring system (GISS), which relies on published evidence of environmental and socio-economic impact of alien species. We developed a system of 12 impact categories, for environmental and socio-economic impact, comprising all kinds of impacts that an alien species may exert. In each category, the intensity of impact is quantified by a six-level scale ranging from 0 (no impact detectable) to 5 (the highest impact possible). Such an approach, where impacts are grouped based on mechanisms for environmental impacts and receiving sectors for socio-economy, allows for cross-taxa comparisons and prioritization of the most damaging species. The GISS is simple and transparent, can be conducted with limited funds, and can be applied to a large number of alien species across taxa and environments. Meanwhile, the system was applied to 349 alien animal and plant species. In a comparison with 22 other impact assessment methods, the combination of environmental and socio-economic impact, as well as the possibility of weighting and ranking of the scoring results make GISS the most broadly applicable system