Search results for "ground"
showing 10 items of 2432 documents
Variational Bethe ansatz approach for dipolar one-dimensional bosons
2020
We propose a variational approximation to the ground state energy of a one-dimensional gas of interacting bosons on the continuum based on the Bethe Ansatz ground state wavefunction of the Lieb-Liniger model. We apply our variational approximation to a gas of dipolar bosons in the single mode approximation and obtain its ground state energy per unit length. This allows for the calculation of the Tomonaga-Luttinger exponent as a function of density and the determination of the structure factor at small momenta. Moreover, in the case of attractive dipolar interaction, an instability is predicted at a critical density, which could be accessed in lanthanide atoms.
Decreasing Phanerozoic extinction intensity as a consequence of Earth surface oxygenation and metazoan ecophysiology
2021
The decline in background extinction rates of marine animals through geologic time is an established but unexplained feature of the Phanerozoic fossil record. There is also growing consensus that the ocean and atmosphere did not become oxygenated to near-modern levels until the mid-Paleozoic, coinciding with the onset of generally lower extinction rates. Physiological theory provides us with a possible causal link between these two observations-predicting that the synergistic impacts of oxygen and temperature on aerobic respiration would have made marine animals more vulnerable to ocean warming events during periods of limited surface oxygenation. Here, we evaluate the hypothesis that chang…
Leaching of glyphosate and AMPA under two soil management practices in Burgundy vineyards (Vosne-Romanée, 21-France)
2005
Some drinking water reservoirs under the vineyards of Burgundy are contaminated with herbicides. Thus the effectiveness of alternative soil management practices, such as grass cover, for reducing the leaching of glyphosate and its metabolite, AMPA, through soils was studied. The leaching of both molecules was studied in structured soil columns under outdoor conditions for 1 year. The soil was managed under two vineyard soil practices: a chemically treated bare calcosol, and a vegetated calcosol. After 680 mm of rainfall, the vegetated calcosol leachates contained lower amounts of glyphosate and AMPA (0.02% and 0.03%, respectively) than the bare calcosol leachates (0.06% and 0.15%, respectiv…
Exposition des eaux souterraines peu profondes à Escherichia coli résistant aux antibiotiques : approche hydrochimique pour identifier les sources et…
2016
L'antibiorésistance est une préoccupation croissante en termes de santé humaine et animale au niveau international. Le but du travail est de suivre l'impact sur la qualité de l'eau dans le bassin versant de l’Ouche et évaluer la capacité des E. coli productrices de BLSE de type CTX-M à se propager et survivre dans les eaux. Une stratégie pour l’échantillonnage des eaux de surface et souterraines a été déployée selon les contextes hydrogéologiques, l'utilisation des terres et les STEP. L’approche hydrochimique s’appuie sur l’analyse des paramètres tels que les nitrates et le bore complétés par l’analyse de Terres rares dont le gadolinium et le suivi de produits pharmaceutiques (caféine, carb…
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…
Définition d’un événement de poussières désertiques au Sahel : apport de nouvelles mesures de PM10 au Burkina Faso.
2015
This study isdedicated to the desert dust of the dry season in an inhabited Sahelian rural area whose populations are widely exposed tosanitary risks such as meningitis outbreaks (Martiny & Chiapello, 2013). Here, the objective is to give a definition of a dust“event”, a concept describing the dustiest moments in a dusty environment, but that remains rather unclear, notably becauseof the lack of ground-truth measurements. The analysis of new PM10 measurements in Burkina Faso has enabled us to definethe dust events as episodes which experience concentrations greater than 189μg/m3 for at least 10h. Five types of dust eventshave been defined depending on the concentrations measured. On the fir…
Elucidating the genetic determinism of the plasticity of seed proteins in response to the environment using Medicago truncatula
2019
International audience; Legumes are able to produce high-protein seeds without nitrogen fertilizer through root symbiosis with nitrogen-fixing rhizobia. Rich in lysine, these proteins are used for human nutrition and animal feed. However, instability of seed protein yield and quality due to environmental fluctuations limits the wide adoption of legumes in Europe. Breeding efforts are needed to optimize and stabilize seed nutritional quality. We have studied the plasticity of protein content and composition of seeds from a collection of 200 ecotypes of Medicago truncatula grown under four controlled conditions (optimal, drought, and winter/spring sowing). A quantitative analysis of one-dimen…
A landscape-scale approach for linking farming strategies to weed communities and their contribution to ecosystem services
2019
National audience; Weeds present in agricultural fields provide habitats and trophic resources and as such contribute to the provision of ecosystem services such as pollination (quantity and quality of pollen and nectar in flowers) and biological control (seeds for pest natural enemies). The nature and amount of services provided depends on the floral composition of weed communities and this composition is driven by the combination of farming practices. Linking farming strategies to services is thus an important step to provide management guidelines for enhancing ecosystem services. We report here on such an analysis, based on agronomical and weed data collected annually in 70 field cores a…
Symbiotic underground biodiversity and plant productivity
2007
National audience
Résistance aux inhibiteurs de l’ALS chez le séneçon commun (Senecio vulgaris) : la situation en vigne et en grandes cultures
2016
Resistance to ALS-inhibiting herbicides in common groundsel (Senecio vulgaris) : situation in franch vineyards and major field crops. Common groundsel (Senecio vulgaris) is a ubiquitous weed that is highly mobile and which seeds can germinate almost all year long. It also is the only weed species today in France that is officially acknowledged to have evolved a resistance to one same herbicide mode of action both in vineyards and major field crops. The purpose of this paper is to provide a picture of a few major aspects of this resistance: underlying mechanisms, detection, seed viability, spread and geographical extent of the resistance.