Structures spatiales en hydrographie continentale

La compréhension de l'effet des hétérogénéités spatio-temporelles de surface sur la réponse hydrologique et l'adaptation par l'homme de ces hétérogénéités représentent un des enjeux majeurs de l'hydrologie tout en dépassant le cadre de la seule recherche académique. Les recherches en géographie quantitative que j'ai réalisées au cours de ces dix dernières années au sein de l'ENGREF puis d'AgroParisTech s'inscrivent dans cette problématique générale et se sont focalisées sur les hétérogénéités spatiales des supports de transfert des flux hydriques de surface concentrés : les réseaux hydrographiques au sens large (cours-d'eau, plans d'eau, ravines, etc). Les approches développées relèvent de modèles de représentation d'hétérogénéités spatiales sur réseau qui combinent des approches métrologiques (télédétection) et de modélisation spatiale stochastique (géostatistique), pour combler les données manquantes et estimer les incertitudes de représentation. Ainsi, comme je tenterai de l'illustrer, ces modèles de représentation spatiale stochastiques contribuent soit à mesurer l'effet de la précision de la représentation des réseaux sur la réponse hydrologique (finalité méthodologique) soit à explorer numériquement l'effet des hétérogénéités spatiales de réseaux sur la réponse hydrologique ainsi que leurs lois d'échelle (finalités cognitives et prédictives). Parce que les capacités d’adaptation des hétérogénéités spatio-temporelles de ces réseaux dans les paysages cultivés sont un enjeu fort agro-environnemental, j'envisage pour mon projet d'étendre ces modèles à la dynamique des propriétés des réseaux hydrographiques des agrosystèmes

Revisiting No-Scale Supergravity Inspired Scenarios

We consider no-scale supergravity inspired scenarios, emphasizing the possible dynamical determination of the soft supersymmetry-breaking parameters as triggered by the radiative corrections that lift an essentially flat tree-level potential in the hidden sector. We (re)emphasize the important role played by the scale-dependent vacuum energy contribution to the effective potential for the occurrence of consistent no-scale minima. The most relevant input parameters are introduced as $B_0$ (the soft breaking mixing Higgs parameter) and $\eta_0$ (the cosmological constant value at high energy) instead of \mhalf and $\tan \beta$, the latter being determined through a (generalized) potential minimization at electroweak scales. We examine the theoretical and phenomenological viability of such a mechanism when confronted with up-to-date calculations of the low energy sparticle spectrum and with present constraints from the LHC and other observables. The tight dark matter relic density constraint for a neutralino LSP scenario can be considerably relaxed for a gravitino LSP scenario possible in this framework.Comment: Proceedings of the 2011 Europhysics Conference on High Energy Physics, EPS-HEP 2011, July 21-27, 2011 Grenoble, Rh\^one-Alpes, Franc

Comparison of two extraction methods for ergosterol determination in vegetal feeds

Ergosterol is the principal sterol of fungi in which it plays an essential role in cell membrane and other cellular constituents. This sterol is considered as a good marker of fungal contamination and of mycotoxin production. After validation of ergosterol quantification by HPLC-UV system (linearity range: 0.2 to 20.0 mg/ml, repeatability: 3.27%, between day precision: 4.75%), 2 extraction methods of ergosterol from 3 vegetal matrixes (maize, barley and wheat) were compared: the first one, normalized by the AFNOR, is based on solid phase extraction (SPE), while the other is based on liquid/liquid extraction (LLE). The LLE procedure allowed ergosterol extraction gains of around 20% for high initial sterol contents (3 to 5 mg/kg) in naturally contaminated matrixes or in spiked samples, and of 86% for low initial sterol contents (1-2 mg/kg) in maize. Moreover, the precision of ergosterol determination was comparable for the 2 methods even if it was slightly lower using LLE and was more affected by the initial ergosterol contents in vegetal matrix than by its nature. These results suggest that ergosterol contents in vegetal feeds would be underestimated with the official method (SPE) and emphasize the importance of the extraction step

Production and purification of fumonisins from a highly toxigenic Fusarium verticilloides strain

Fumonisins are the major mycotoxins produced by Fusarium verticilloides and F. proliferatum fungi which are widely found as contaminants in corn and corn screenings. These molecules are hepatotoxic and nephrotoxic for several species and carcinogenic in rodents. Moreover their consumption was linked to high prevalence of human oesophageal cancer in certain geographic areas. The aim of this work was to improve FB1 production and purification procedures in laboratory conditions in order to produce large quantities of semi-purified toxin that may be used in experimental intoxications of farm animals. We used a highly toxigenic strain of Fusarium verticilloides (NRRL-3428) isolated from feeds. Influence of substrate, temperature, water content, culture recipient size and screen analysis of the substrate on fumonisin production was tested. Optimal production was obtained when strain was grown on coarsely cracked corn with 50% water content at 21°C during 5 weeks. This allowed the production of 3 to 4 g of fumonisin B1 per kg of culture material. The composition of the extracts was found to be as follow : 54% FB1, 8% FB2, 9% FB3 and 29% of pigments coming from corn. The ratio observed between FB1 and FB2 is comparable to the one reported in naturally contaminated corn. Further purification of these extracts on SAX columns led to the removal of pigments and to obtain of fumonisins extracts pure enough to be used for intra-venous or intra-peritoneal injection

Testing for Consistency in Tourists' Willingness to Pay for New Nature Reserves in the Gulf of Morbihan (France)

In this paper, we develop an empirical test of consistency in contingent willingness to pay (WTP) responses, which is based on the following a priori expectation. In economics, when an individual considers paying for public goods, his decision to pay, and his WTP are based on utility-maximising behaviour. Accordingly, supposing other factors are identical, if individual A expresses greater interest in paying for public goods in general than individual B, that is because A receives more benefits from the use and/or the non-use of these goods than B. Continuing with this logic, if both individuals are asked about their WTP for a precise public good, A should logically be more likely to pay and should be willing to pay more than B. Thus, the test consists in measuring the degree to which people are likely to give money for public goods in general, and including it as a covariate in WTP models for the specific public good. If this covariate is significantly positive, then WTP responses are considered consistent. If this is not the case, then future research might focus on motives behind inconsistent WTP responses. To assess the robustness of the test, we consider 3 situations 1) the covariate is exogenous 2) it is endogenous and uncorrelated with the choice to pay or not for the specific good 3) it is endogenous and correlated with this choice. Using a contingent valuation study estimating tourists’ willingness to pay for future nature reserves in the Gulf of Morbihan, we find that WTP responses are consistent in all situations considered.contingent valuation, consistency, endogeneity, Consumer/Household Economics, Resource /Energy Economics and Policy, C24, D12, Q26,

Reducing Ammonia Losses By Adding FeCI3 During Composting Of Sewage Sludge

The release of ammonia nitrogen during composting of sewage sludge mixed with a lignocellulosic bulking agent leads to a reduction in the agronomic value of the final compost and to harmful effects on the environment. We propose adding a cheap salt FeCl3 which can be used without special precaution to reduce ammonia losses by decreasing pH conditions. An in-vessel co-composting experiment was conducted in a large reactor (100 L) in which FeCl3 was added to sludge mixed with a bulking agent (pine shavings and sawdust) and compared with a control mixture without FeCl3. Temperature, oxygen consumption and pH were monitored throughout the composting of both mixtures. The final balance of organic matter, organic and inorganic nitrogen permitted to conclude that the addition of FeCl3 reduced nitrogen loss (by a factor of 2.4 in relation to the control) and increased mineralisation of the organic nitrogen by 1.6

Chemical and spectroscopic analysis of olive mill waste water during a biological treatment

The treatment of olive mill waste water was studied on the laboratory scale. Physico–chemical analyses showed the final products had a mean pH of 5.4 without neutralisation and 5.7 when lime was added to the process. Raising the pH by adding lime had a positive outcome on the degradation of phenols, whose levels were reduced by over 76%. The lime also changed the structure of the organic matter, as seen in the infra-red spectra. Combining the FT-IR and 13C NMR data showed that with addition of lime, the density of aliphatic groups decreased to the benefit of aromatic groups, indicating that polymerisation of the organic matter occurred during the bioprocess. Under our experimental conditions, the biotransformation of olive mill waste water appears to favour the stabilisation of the organic matter through mechanisms analogous to those that lead to the formation of humus in the soil

Toxicokinetics of fumonisin B1 in turkey poults and tissue persistence after exposure to a diet containing the maximum European tolerance for fumonisins in avian feeds

The kinetic of fumonisin B1 (FB1) after a single IV and oral dose, and FB1 persistence in tissue were investigated in turkey poults by HPLC after purification of samples on columns. After IV administration (single-dose: 10 mg FB1/kg bw), serum concentration–time curves were best described by a three-compartment open model. Elimination half-life and mean residence time of FB1 were 85 and 52 min, respectively. After oral administration (single-dose: 100 mg FB1/kg bw) bioavailability was 3.2%; elimination half-life and mean residence time were 214 and 408 min, respectively. Clearance of FB1 was 7.6 and 7.5 ml/min/kg for IV and oral administration respectively. Twenty four hours after the administration of FB1 by the intravenous route, liver and kidney contained the highest levels of FB1 in tissues, level in muscle was low or below the limit of detection (LD, 13 µg/kg). The persistence of FB1 in tissue was also studied after administration for nine weeks of a feed that contained 5, 10 and 20 mg FB1+FB2/kg diet. Eight hours after the last intake of 20 mg FB1+FB2/kg feed (maximum recommended concentration of fumonisins established by the EU for avian feed), hepatic and renal FB1 concentrations were 119 and 22 µg/kg, level in muscles was below the LD

Cheminement des eaux superficielles et télédétection pour la modélisation hydrologique distribuée

Communication invitée lors du 13. International Symposium on Spatial Data Handling: 2008; Montpellier, France: 2008/07/23-25Les cheminements superficiels des eaux sont de mieux en mieux décrits à partir des informations spatiales. En particulier les MNT à très haute résolution spatiale apportent des données nouvelles qui autorisent une description fine des réseaux d'écoulement superficiel et donc l'intégration de ces structures dans les modélisations hydrologiques distribuées. Mais si les techniques numériques d'observation ont fait de grands progrès dans les années passées, par contre il n'en est pas de même pour les concepts en modélisation et les expérimentations de terrain, ce qui provoque un point de blocage pour une réelle utilisation des données de télédétection finement résolues dans les modèles. Le développement de nouvelles techniques de mesure sur le terrain, de type low cost et réseaux communicants, est porteur de renouveau dans ce domaine. / Water paths are better and better described through spatial data. High resolution DTM are a good solution for mapping fine water networks and their integration into hydrological modelling. But if, in past years, big progresses concerned spatial data techniques, on the other hand they did concern concepts in modelling and ground experiments. And this is a difficulty for a real use of remote sensing data into finely resolved models. New possibilities are carrying revival in this field, through development of low cost ground techniques and communicating wireless networks