Reconstructing the Cosmic Expansion History up to Redshift z=6.29 with the Calibrated Gamma-Ray Bursts

Recently, Gamma-Ray Bursts (GRBs) were proposed to be a complementary cosmological probe to type Ia supernovae (SNIa). GRBs have been advocated to be standard candles since several empirical GRB luminosity relations were proposed as distance indicators. However, there is a so-called circularity problem in the direct use of GRBs. Recently, a new idea to calibrate GRBs in a completely cosmology independent manner has been proposed, and the circularity problem can be solved. In the present work, following the method proposed by Liang {\it et al.}, we calibrate 70 GRBs with the Amati relation using 307 SNIa. Then, following the method proposed by Shafieloo {\it et al.}, we smoothly reconstruct the cosmic expansion history up to redshift $z=6.29$ with the calibrated GRBs. We find some new features in the reconstructed results.Comment: 12 pages, 4 figures, 1 table, revtex4; v2: title changed, accepted by Eur. Phys. J. C; v3: published versio

Validation d'une batterie destinée aux candidats à l'admission (anticipée ou retardée) à l'école primaire.

Following the administration of a battery of tests at the beginning of the first school year, the predictive validities of these tests vs. the school grades of the first and second years were studied on three samples of students. Success in arithmetics is best predicted, but success in reading, writing, spelling and vocabulary is also predictible, even in the two selected samples. The use of an abridged battery of four tests is recommanded.A partir d'une batterie de tests appliquée à l'entrée de la première année primaire, on a étudié la validité prédictive de ces tests à court terme ( notes de première année) et moyen terme {notes de deuxième année), sur trois échantillons d'élèves. La réussite en arithmétique est celle qui est le mieux prédite et par le plus grand nombre de tests ; cependant , les réussites en lecture, écriture, grammaire, vocabulaire et composition sont aussi prédictibles à partir de ces tests, même dans les groupes déjà sélectionnés. Une batterie réduite à quatre tests peut être préconisée.Gendre F., Dupont J.-B., Parisod A., Descombes J.P. Validation d'une batterie destinée aux candidats à l'admission (anticipée ou retardée) à l'école primaire.. In: Enfance, tome 29, n°4-5, 1976. pp. 467-479

L'hydrodynamique du lagon sud-ouest

La circulation des eaux dans le lagon sud-ouest Nouvelle-Calédonie est due à trois agents principaux : la marée, le vent local et le déferlement la houle par-dessus le récif-barrière

Circulation and suspended sediment transport in a coral reef lagoon: The south-west lagoon of New Caledonia

International audienceThe south-west lagoon of New Caledonia is a wide semi-open coral reef lagoon bounded by an intertidal barrier reef and bisected by numerous deep inlets. This paper synthesizes findings from the 2000-2008 French National Program EC2CO-PNEC relative to the circulation and the transport of suspended particles in this lagoon. Numerical model development (hydrodynamic, fine suspended sediment transport, wind-wave, small-scale atmospheric circulation) allowed the determination of circulation patterns in the lagoon and the charting of residence time, the later of which has been recently used in a series of ecological studies. Topical studies based on field measurements permitted the parameterisation of wave set-up induced by the swell breaking on the reef barrier and the validation of a wind-wave model in a fetch-limited environment. The analysis of spatial and temporal variability of suspended matter concentration over short and long time-scales, the measurement of grain size distribution and the density of suspended matter (1.27 kg l−1), and the estimation of erodibility of heterogeneous (sand/mud, terrigenous/biogenic) soft bottoms was also conducted. Aggregates were shown to be more abundant near or around reefs and a possible biological influence on this aggregation is discussed. Optical measurements enabled the quantification of suspended matter either in situ (monochromatic measurements) or remotely (surface spectral measurements and satellite observations) and provided indirect calibration and validation of a suspended sediment transport model. The processes that warrant further investigation in order to improve our knowledge of circulation and suspended sediment transport in the New Caledonia lagoon as well as in other coral reef areas are discussed, as are the relevance and reliability of the numerical models for this endeavour