Evaluation of modelling approaches for predicting the spatial distribution of soil organic carbon stocks at the national scale

Soil organic carbon (SOC) plays a major role in the global carbon budget. It can act as a source or a sink of atmospheric carbon, thereby possibly influencing the course of climate change. Improving the tools that model the spatial distributions of SOC stocks at national scales is a priority, both for monitoring changes in SOC and as an input for global carbon cycles studies. In this paper, we compare and evaluate two recent and promising modelling approaches. First, we considered several increasingly complex boosted regression trees (BRT), a convenient and efficient multiple regression model from the statistical learning field. Further, we considered a robust geostatistical approach coupled to the BRT models. Testing the different approaches was performed on the dataset from the French Soil Monitoring Network, with a consistent cross-validation procedure. We showed that when a limited number of predictors were included in the BRT model, the standalone BRT predictions were significantly improved by robust geostatistical modelling of the residuals. However, when data for several SOC drivers were included, the standalone BRT model predictions were not significantly improved by geostatistical modelling. Therefore, in this latter situation, the BRT predictions might be considered adequate without the need for geostatistical modelling, provided that i) care is exercised in model fitting and validating, and ii) the dataset does not allow for modelling of local spatial autocorrelations, as is the case for many national systematic sampling schemes

Systematic InSAR tropospheric phase delay corrections from global meteorological reanalysis data

6p.International audienceDespite remarkable successes achieved by Differential InSAR, estimations of low tectonic strain rates remain challenging in areas where deformation and topography are correlated, mainly because of the topography‐related atmospheric phase screen (APS). In areas of high relief, empirical removal of the stratified component of the APS may lead to biased estimations of tectonic deformation rates. Here we describe a method to correct interferograms from the effects of the spatial and temporal variations in tropospheric stratification by computing tropospheric delay maps coincident with SAR acquisitions using the ERA‐ Interim global meteorological model. The modeled phase delay is integrated along vertical profiles at the ERA‐I grid nodes and interpolated at the spatial sampling of the interferograms above the elevation of each image pixel. This approach is validated on unwrapped interferograms. We show that the removal of the atmospheric signal before phase unwrapping reduces the risk of unwrapping errors in areas of rough topography

Recherches sur la toxicité et les propriétés anthelminthiques de la Dithiazanine

Guillot Jacques, Jolivet Gilbert. Recherches sur la toxicité et les propriétés anthelminthiques de la Dithiazanine. In: Bulletin de l'Académie Vétérinaire de France tome 112 n°7, 1959. pp. 413-419

Action de la Dithiazanine sur Strongyloides papillosus

Guilhon Jean, Jolivet Gilbert. Action de la Dithiazanine sur Strongyloides papillosus. In: Bulletin de l'Académie Vétérinaire de France tome 114 n°7, 1961. pp. 263-265

Structural insights into Clostridium perfringens delta toxin pore formation

Clostridium perfringens Delta toxin is one of the three hemolysin-like proteins produced by C. perfringens type C and possibly type B strains. One of the others, NetB, has been shown to be the major cause of Avian Nectrotic Enteritis, which following the reduction in use of antibiotics as growth promoters, has become an emerging disease of industrial poultry. Delta toxin itself is cytotoxic to the wide range of human and animal macrophages and platelets that present GM2 ganglioside on their membranes. It has sequence similarity with Staphylococcus aureus β-pore forming toxins and is expected to heptamerize and form pores in the lipid bilayer of host cell membranes. Nevertheless, its exact mode of action remains undetermined. Here we report the 2.4 Å crystal structure of monomeric Delta toxin. The superposition of this structure with the structure of the phospholipid-bound F component of S. aureus leucocidin (LukF) revealed that the glycerol molecules bound to Delta toxin and the phospholipids in LukF are accommodated in the same hydrophobic clefts, corresponding to where the toxin is expected to latch onto the membrane, though the binding sites show significant differences. From structure-based sequence alignment with the known structure of staphylococcal α-hemolysin, a model of the Delta toxin pore form has been built. Using electron microscopy, we have validated our model and characterized the Delta toxin pore on liposomes. These results highlight both similarities and differences in the mechanism of Delta toxin (and by extension NetB) cytotoxicity from that of the staphylococcal pore-forming toxins

Considérations sur l’emploi des organo-phosphorés dans le traitement interne de la démodexose canine

Guilhon Jean, Jolivet Gilbert, Marchand A. Considérations sur l’emploi des organo-phosphorés dans le traitement interne de la démodexose canine. In: Bulletin de l'Académie Vétérinaire de France tome 128 n°4-5, 1975. pp. 243-251

Utilisation d’un nouvel antigène pour le séro-diagnostic de la Toxoplasmose des animaux domestiques, par la méthode d’agglutination de FULTON

Guilhon Jean, Jolivet Gilbert, Marchand A. Utilisation d’un nouvel antigène par le séro-diagnostic de la Toxoplasmose des animaux domestiques par la méthode d’agglutination de Fulton. In: Bulletin de l'Académie Vétérinaire de France tome 126 n°4, 1973. pp. 161-165

Action du diamphénétide sur Dicrocoelium lanceolatum

Jolivet G., Lafay E., Nicolas J. A. Action du diamphénétide sur Dicrocoelium lanceolatum. In: Bulletin de l'Académie Vétérinaire de France tome 127 n°7, 1974. pp. 303-308