Search results for "Universe"
showing 10 items of 2171 documents
La recherche publique en France en 2019 : Diagnostic et propositions du Comité national
2019
Projet porté par le Comité National du CNRS.; Dans le contexte de la préparation d’une loi de programmation pluriannuelle de la recherche, ce document présente la contribution du Comité national de la recherche scientifique à l’analyse de la situation de la recherche publique en France, de son évolution récente (depuis la loi LRU de 2008) et de ses perspectives, ainsi qu’un ensemble de propositions qui ont été finalisées et ont fait l’objet d’une approbation solennelle lors de la session plénière du Comité national organisée à Paris le 4 juillet 2019.
Etude de l'évolution de la pollution atmosphérique par le CO2 dans la ville de Cotonou utilisant la signature isotopique des graminées C4
2007
8 pages; International audience
Evolution rétrospective du risque gélif hivernal en climat tempéré suite au réchauffement climatique
2018
Prod 2019-139 BAP POLE EA GEAPSI INRA AGROSUP; National audience; Les modalités du réchauffement climatique sur l’Europe de l’ouest montrent pour les températures une rupture nette en 1987/1988. Deux régimes distincts de température ont eu cours de part et d’autre de cette rupture. Cela offre une opportunité pour évaluer un impact du réchauffement en Bourgogne Franche-Comté. Peu de travaux documentent néanmoins les conséquences du réchauffement hivernal sur la végétation en général et les cultures en particulier. Pourtant, ces dernières années, des travaux suggèrent une augmentation du risque gélif présentée comme un effet paradoxal du réchauffement climatique. En combinant, sur la période …
Loss in microbial diversity affects nitrogen cycling in soil
2013
International audience; Microbial communities have a central role in ecosystem processes by driving the Earth's biogeochemical cycles. However, the importance of microbial diversity for ecosystem functioning is still debated. Here, we experimentally manipulated the soil microbial community using a dilution approach to analyze the functional consequences of diversity loss. A trait-centered approach was embraced using the denitrifiers as model guild due to their role in nitrogen cycling, a major ecosystem service. How various diversity metrics related to richness, eveness and phylogenetic diversity of the soil denitrifier community were affected by the removal experiment was assessed by 454 s…
Evolution et transformation des sols viticoles en lien avec l’évolution et la dynamique des paysages et parcellaires viticoles
2018
International audience; Les sols et les paysages évo- luent conjointement sous l’effet combiné de facteurs naturels et humains. Cette coévolution se retrouve dans l’analyse des terroirs viticoles, construits et transformés au cours du temps. Ainsi les sols viticoles obser- vés aujourd’hui sont l’héritage d’une construction multiphasée et d’occupations successives qui ont transformé progressi- vement les paysages viticoles. Aussi, la compréhension des sols ne peut être dissociée de celle de la structuration du pay- sage, à un tel point que des dif- férences entre terroirs peuvent s’expliquer, entre autres, par des trajectoires agraires différentes. Les paysages viticoles sont des mosaïques d…
Le réchauffement climatique diminue-t-il le risque de dégâts par le gel pour les cultures de climat tempéré ?
2014
Does global warming reduce the freezing injury risk to temperate climate crops? Winter crop response to a temperature increase is complex. Recent works point out, for cold climate vegetation, a paradoxical increase in freezing injury in a warming climate. Complementary works are needed to support these results for winter crops in temperate areas. To achieve this goal, five climatic records spanning a fifty years-long period for both daily minimum and maximum temperatures were analyzed with a model predicting frost hardiness and freezing damage for the winter pea crop. The methodological approach was based on three main steps: 1) the climate warming analysis of the 1987/1988 temperature shif…
Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei
2008
Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the ighest-energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) [Pierre Auger Collaboration, Science 318 (2007) 938]. The correlation has maximum significance for cosmic rays with energy greater than ~6 x 1019 eV and AGN at a distance less than ~75 Mpc. We have confirmed the anisotropy at a confidence level of more than 99% through a test with parameters specified a priori, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest-energies originate fro…
INTEGRAL serendipitous detection of the gamma-ray microquasar LS 5039
2006
LS 5039 is the only X-ray binary persistently detected at TeV energies by the Cherenkov HESS telescope. It is moreover a gamma-ray emitter in the GeV and possibly MeV energy ranges. To understand important aspects of jet physics, like the magnetic field content or particle acceleration, and emission processes, such as synchrotron and inverse Compton (IC), a complete modeling of the multiwavelength data is necessary. LS 5039 has been detected along almost all the electromagnetic spectrum thanks to several radio, infrared, optical and soft X-ray detections. However, hard X-ray detections above 20 keV have been so far elusive and/or doubtful, partly due to source confusion for the poor spatial…
Observation of the suppression of the flux of cosmic rays above 4x10^19eV
2008
The energy spectrum of cosmic rays above 2.5 × 10¹⁸ eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index γ of the particle flux, J ∝ E-γ, at energies between 4 × 10¹⁸ eV and 4 × 10¹⁹ eV is 2.69 ± 0.02(stat) ± 0.06(syst), steepening to 4.2 ± 0.4(stat) ± 0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min.
Upper limit on the diffuse flux of ultrahigh energy tau neutrinos from the Pierre Auger Observatory
2008
The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth’s crust. Tau leptons from ντ charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of ντ at EeV energies. Assuming an E−2ν differential energy spectrum the limit set at 90% C.L. is E2νdNντdEν<1.3×10−7 GeV cm−2 s−1 sr−1 in the energy range 2×1017 eV<E<2×1019 eV.