Programmes et objectifs du cours d’EP au secondaire inférieur

La majorité des responsables de formations initiales des enseignants sont conscients que la confrontation avec le terrain – à travers les stages – des notions développées en école supérieure est primordiale pour l’appropriation de ces dernières par les étudiants. Parmi celles-ci, la connaissance et l’application des programmes officiels d’éducation physique (EP) sont des points centraux de la formation. Mais force est de constater que nos étudiants ne peuvent parfois ne compter que sur eux-mê..

Les rêves colonialistes allemands échouent à Tabora

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Silicon isotopes record dissolution and re-precipitation of pedogenic clay minerals in a podzolic soil chronosequence.

By providing the largest part of the reactive surface area of soils, secondary minerals play a major role in terrestrial biogeochemical processes. The understanding of the mechanisms governing neo(trans-)formation of pedogenic clay minerals in soils is therefore of the utmost importance to learn how soils evolve and impact the chemistry of elements in terrestrial environments. Soil-forming processes governing the evolution of secondary aluminosilicates in Podzols are however still not fully understood. The evolution of silicon (Si) isotope signature in the clay fraction of a podzolic soil chronosequence can provide new insight into these processes, enabling to trace the source of Si in secondary aluminosilicates during podzol-forming processes characterized by the mobilization, transport and precipitation of carbon, metals and Si. The Si isotope compositions in the clay fraction (comprised of primary and secondary minerals) document an increasing light 28Si enrichment and depletion with soil age, respectively in illuvial B horizons and eluvial E horizon. The mass balance approach demonstrates that secondary minerals in the topsoil eluvial E horizons are isotopically heavier with δ30Si values increasing from -0.39 to +0.64‰ in c.a. 200years, while secondary minerals in the illuvial Bhs horizon are isotopically lighter (δ30Si=-2.31‰), compared to the original "unweathered" secondary minerals in BC horizon (δ30Si=-1.40‰). The evolution of Si isotope signatures is explained by the dissolution of pedogenic clay minerals in the topsoil, which is a source of light 28Si for the re-precipitation of new clay minerals in the subsoil. This provides consistent evidence that in strong weathering environment such as encountered in Podzols, Si released from secondary minerals is partially used to form "tertiary clay minerals" over very short time scales (ca. 300years). Our dataset demonstrates the usefulness to measure Si isotope signatures in the clay fraction to discern clay mineral changes (e.g., neoformation versus solid state transformation) during soil evolution. This offers new opportunity to better understand clay mineral genesis under environmental changes, and the short-term impact of the dissolution and re-precipitation of pedogenic clay minerals on soil fertility, soil carbon budget and elemental cycles in soil-plant systems. © 2014 Elsevier B.V

Evaluation of a New Fully Automated Assay for Plasma Intact FGF23.

Several FGF23 immunoassays are available. However, they are reserved for research purposes as none have been approved for clinical use. We evaluated the performances of a new automated assay for intact FGF23 on the DiaSorin Liaison platform which is approved for clinical use. We established reference values in 908 healthy French subjects aged 18-89 years, and measured iFGF23 in patients with disorders of phosphate metabolism and in patients with chronic kidney disease (CKD). Intra-assay CV was 1.04-2.86% and inter-assay CV was 4.01-6.3%. The limit of quantification was <10 ng/L. Serum iFGF23 concentrations were considerably lower than EDTA values highlighting the importance of using exclusively EDTA plasma. Liaison iFGF23 values were approximately 25% higher than Immutopics values. In the 908 healthy subjects, distribution of the Liaison iFGF23 values was Gaussian with a mean +/- 2SD interval of 22.7-93.1 ng/L. Men had a slightly higher level than women (60.3 +/- 17.6 and 55.2 +/- 17.2 ng/L, respectively). Plasma iFGF23 concentration in 11 patients with tumour-induced osteomalacia, 8 patients with X-linked hypophosphatemic rickets, 43 stage 3a, 43 stage 3b, 43 stage 4, 44 stage 5 CKD patients, and 44 dialysis patients were 217.2 +/- 144.0, 150.9 +/- 28.6, 98.5 +/- 42.0, 130.8 +/- 88.6, 130.8 +/- 88.6, 331.7 +/- 468.2, 788.8 +/- 1306.6 and 6103.9 +/- 11,178.8 ng/L, respectively. This new iFGF23 assay available on a platform that already allows the measurement of other important parameters of the mineral metabolism is a real improvement for the laboratories and clinicians/researchers involved in this field

Crystal structure, band structure and electrical properties of kappa-(BEDT-TTF)(2)SbF6 grown on a Si(001) electrode

The new kappa-(BEDT-TTF)(2)SbF6 phase was grown by electrodeposition on a Si(0 0 1) electrode. This new phase was characterized by X-ray diffraction (XRD) and electronic conductivity measurements, accompanied by calculations of electronic band structures and Fermi surfaces. Below T = 120 K, a decrease in the electronic conductivity suggests a phase transition, attributed to anion ordering. (C) 2009 Elsevier B.V. All rights reserved

Triggering Anionic Redox Activity in Li 3 NbS 4 Through Cationic Disordering or Substitution

International audienceExtensive utilization of Li-ion batteries for varieties of applications necessitates ceaseless improvements of electrode materials for achieving higher energy density. Towards this goal, Li-rich layered oxides exhibiting high capacity due to cumulated cationic and anionic redox activities are under study for nearly a decade. Still, several unanswered questions remain with respect to these Li-driven anionic redox reactions in terms of the activation process and long-term consequences upon cycling. Here, the Li-rich Li3NbS4 phase is focused, and synthesized as two different polymorphs, namely ordered and disordered phases. From analyses of their chemical and electrochemical properties, a crystal-electronic structure relationship is unraveled that triggers the anionic redox activity in these compounds. Moreover, through complementary theoretical calculations, the capability of cationic disorder to trigger anionic redox activity via the hybridization of cationic and non-bonding anionic energy levels is shown. This finding is further supported by the appearance of anionic redox activity by introducing the disorder through cationic substitution. Altogether, the insights derived can help in designing new anionic redox materials with optimum performances for practical applications

Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li3IrO4

International audienceThe Li-rich rocksalt oxides Li2MO3 (M = 3d/4d/5d transition metal) are promising positive-electrode materials for Li-ion batteries, displaying capacities exceeding 300 mAh g–1 thanks to the participation of the oxygen non-bonding O(2p) orbitals in the redox process. Understanding the oxygen redox limitations and the role of the O/M ratio is therefore crucial for the rational design of materials with improved electrochemical performances. Here we push oxygen redox to its limits with the discovery of a Li3IrO4 compound (O/M = 4) that can reversibly take up and release 3.5 electrons per Ir and possesses the highest capacity ever reported for any positive insertion electrode. By quantitatively monitoring the oxidation process, we demonstrate the material’s instability against O2 release on removal of all Li. Our results show that the O/M parameter delineates the boundary between the material’s maximum capacity and its stability, hence providing valuable insights for further development of high-capacity materials