Search results for "Universe"
showing 10 items of 2171 documents
The organic carbon derived from sewage sludge as a key parameter determining the fate of trace metals.
2007
8 pages; International audience; In a sandy agricultural soil of south-west of France, continuously cultivated with maize and amended with sewage-sludge over 20 years, the behavior of three trace metals (Cu, Pb, and Zn) was studied during the sludge applications (1974-1993) and after its cessation (1993-1998). Using the delta13C analysis, the dynamics of different sources of organic matter were followed in order to elucidate the influence of the sludge-derived organic matter on the fate of trace metals in the soil and its particle size fractions. This study revealed that sludge-derived organic matter contributed to the formation of macroaggregates through the binding of preexisting microagg…
Nuclear liquid-gas phase transition and supernovae evolution
2004
It is shown that the large density fluctuations appearing at the onset of the first order nuclear liquid-gas phase transition can play an important role in the supernovae evolution. Due to these fluctuations, the neutrino gas may be trapped inside a thin layer of matter near the proto-neutron star surface. The resulting increase of pressure may induce strong particle ejection a few hundred milliseconds after the bounce of the collapse, contributing to the revival of the shock wave. The Hartree-Fock+RPA scheme, with a finite-range nucleon-nucleon effective interaction, is employed to estimate the effects of the neutrino trapping due to the strong density fluctuations, and to discuss qualitat…
On the role of shock waves in galaxy cluster evolution
1998
Numerical simulations of galaxy clusters including two species -- baryonic gas and dark matter particles --are presented. Cold Dark Matter spectrum, Gaussian statistics and flat universe are assumed. The dark matter component is evolved numerically by means of a standard particle mesh method. The evolution of the baryonic component has been studied numerically by using a multidimensional (3D) hydrodynamical code based on modern high resolution shock capturing techniques. These techniques are specially designed for treating accurately complex flows in which shocks appear and interact. With this picture, the role of shock waves in the formation and evolution of rich galaxy clusters is analyze…
Probing the radio emission from air showers with polarization measurements
2014
The emission of radio waves from air showers has been attributed to the so-called geomagnetic emission process. At frequencies around 50 MHz this process leads to coherent radiation which can be observed with rather simple setups. The direction of the electric field induced by this emission process depends only on the local magnetic field vector and on the incoming direction of the air shower. We report on measurements of the electric field vector where, in addition to this geomagnetic component, another component has been observed which cannot be described by the geomagnetic emission process. The data provide strong evidence that the other electric field component is polarized radially wit…
Une carte et une base de données pour les formations à silex dans le Sud de la France.
2012
Programme et résumés, page 139; Une carte est en cours de réalisation pour figurer les principales formations contenant des silex dans le Sud de la France. Elle est le fruit d'une collaboration entre des acteurs impliqués dans la problématique de caractérisation de la provenance des silex. Elle regroupe les résultats de leurs prospections systématiques ou ciblées dans cinq régions (Auvergne, Rhône-Alpes, Provence Alpes Côte-d'Azur, Aquitaine, Midi-Pyrénées). Elle intègre le dépouillement d'un nombre considérable de documents : - 529 cartes géologiques au 1/50 000 et leurs notices ; - Plus de 200 fiches issues de la base de données du sous-sol BSS du BRGM, qui permettent de visualiser des lo…
Molecular Selectivity of CH 4 –C 2 H 6 Mixed Hydrates: A GCMC Study
2021
International audience; In this paper, we report the first grand canonical Monte Carlo simulation study aiming at characterizing the competitive trapping of CH4 and C2H6 molecules into clathrate hydrates under temperature conditions typical of those encountered at the surface of Titan. Various compositions of the fluid in contact with the clathrate phase have been considered in the simulations, including pure methane, pure ethane, and mixed fluids made of various methane/ethane ratios. The trapping isotherms obtained from the simulations clearly show that ethane molecules can be enclathrated at lower pressures than methane molecules. In addition, they provide evidence that the methane molec…
Long-term effects of metal-containing farmyard manure and sewage sludge on soil organic matter in a fluvisol
2005
Abstract Our aim was to establish the long-term effects of repeated applications after 20 y of organic amendments (farmyard manure at 10 t ha −1 y −1 , and urban sewage sludge at two different rates, 10 t ha −1 y −1 and 100 t ha −1 every 2 y) on the quality of a sandy and poorly buffered soil (Fluvisol, pH 6). Chemical characteristics and biodegradability of the labile organic matter, which is mainly derived from microbial biomass and biodegradation products of organic residues, were chosen as indicators for soil quality. The organic C content had reached a maximal value (30.6 g C kg −1 in the 100 t sludge-treated soil), i.e. about 2.5 times that in the control. Six years after the last a…
Contamination of soil by copper affects the dynamics, diversity, and activity of soil bacterial communities involved in wheat decomposition and carbo…
2009
ABSTRACT A soil microcosm experiment was conducted to evaluate the influence of copper contamination on the dynamics and diversity of bacterial communities actively involved in wheat residue decomposition. In the presence of copper, a higher level of CO 2 release was observed, which did not arise from greater wheat decomposition but from a higher level of stimulation of soil organic matter mineralization (known as the priming effect). Such functional modifications may be related to significant modifications in the diversity of active bacterial populations characterized using the DNA stable-isotope probing approach.
Analyse cartographique de données pédologiques et hydrogéologiques appliquée à la gestion responsable de produits phytosanitaires
2014
BASF launched a Responsible Bentazone Management plan in 2011, in order to preserve water resources and sustain its bentazon based herbicide solutions. This molecule is commercialized by the company for several years and is found at concentrations above the standard for drinking water in about 1% of groundwater catchments in France. The action plan aims to reduce contamination situations with recommendations on the use of bentazone (dose, timing of application, restrictions on vulnerable soils on groundwater catchment areas) that complement the commercialization authorization. The study carried out during the internship focused on the diagnosis of a groundwater catchment area located in the…
Link between microbial diversity, stability of microbial communities and soil organic matter turnover
2014
Soil microbial communities act as important agents of the biological soil functioning, particularly through their involvements in the transformations of biogeochemical cycles (C, N, P…). In agro-ecosystems, the diversity of these communities is affected by perturbations associated to agricultural practices, and the significance of these modifications in terms of preservation of biological functioning and sustainability of agricultural systems has emerged as a central issue in the environmental sciences. Whereas the role of biodiversity has been well studied for macroorganisms, in particular for plants; the biodiversity/activity relationship is still largely unknown for soil microorganisms. …