Suivis des réorganisations superficielles de parcelles de sols et de tepetates (Texcoco, Mexique)

La cordillère des hauts plateaux du Mexique se caractérise par la présence de sols d'origine volcanique. L'une des propriétés de ces sols appelés tepetates, inclus aussi dans la Sierra Néovolcanique est une dureté acquise lors d'un processus pédo-géologique qui les rend difficilement exploitables par les méthodes traditionnelles. De plus, ces surfaces laissées à nu sont sujettes aux phénomènes d'érosion et participent à la pollution des nappes phréatiques, constat très préoccupant dans la vallée de Mexico dont la densité de population croît considérablement. C'est dans ce contexte que s'inscrit notre étude dont la finalité globale est la réhabilitation des sols volcaniques indurés à l'agriculture. Elle consiste en un suivi des réorganisations superficielles de parcelles représentatives des techniques agricoles régionales d'un versant nord-est de la vallée de Mexico, par l'intermédiaire de mesures telles l'humidité superficielle, la fonte des agrégats, le diamètre minimum et d'observation à l'échelle parcellaire d'accidents superficiels. L'outil point quadrat nous a permis de suivre l'évolution du micro relief et de ses différentes organisations. Notre travail a montré qu'à partir d'un remaniement de la surface correspondant aux travaux d'entretien, les agrégats s'incluent dans une première croûte résultant du rejaillissement de particules sous l'impact des gouttes d'eaux. Ces particules mobilisables proviennent aussi de la dégradation des agrégats par l'alternance humectation-dissecation. Dans une dynamique dépendante des conditions climatiques, agronomiques, pédologiques et géologiques, cette croûte se différencie sur le haut des micro reliefs (hauts billons) en croûte de décantation. Le résultat étant une dégradation de l'infiltration qui aboutit à un déplacement horizontal et donc une exportation de matière vers l'aval. Un itinéraire technique approprié peut alors freiner cette perte de substrat néfaste à la bonne croissance des plantes. (Résumé d'auteur)

Suelos volcanicos endurecidos

In Mexico, there is very few informations about the soil surface crusting in relation to the rain. When creating a new soil from a indurated volcanic tuff, it is important to study the behaviour and dynamics of the new structure under the action of rain and cultivation practices. We followed 6 terraces during 3 years on different kinds of soil and tepetate, as well as different kinds of soil tillage and crops. We used the rugosimeter and a crop covermeter of 2 m2 with a precision of 10 cm2 for each mesure. We measured the humidity and thecrusting of the soil after every runoff-producing event and the vegetation covering once a week. At the same time, we followed the state of the row and their ruptures along every terrace. This study confirms and details the 4 different kinds of crusting of this new soil. They are following this dynamic: 1) a structure crust with predominance of plasma is formed; 2) then come the erosion crust; 3) then the runoff crust and nearly in the same time; 4) the deposit crust. To pass from the phase 1 to 2, the cumulated energy of the rain must be higher than 560 MJ/h. In the case of the beginning of destruction of the row, this energy is nearly the same: 530 for the tepetate and 580 MJ/ha for the soil (phoeozem). Laboratory tests and the following of agregates bigger than 5 cm show that in the case of terraces with manure, the strucutre of the soil is more stable. But in the fields, there is not such a clear difference with the other treatments. The protection of the soil by vegetation is clearly better with the other treatments. It does not only protect the aggregates but also the row. In effect, corn produces a stem flow which destrys the row at the foot of the plant, while the association of corn and string bean limitsthis influence by the captation of the rain by the string bean. In the case of barley, the erosion is laminar and diffuse but, at the base of the terrace, it is possible to notice a clear runoff concentration. In the case of corn, water is concentrated inside the row and under certain conditions occurs a movement from one row to the other one due to their rupture. Erosion is more visible but really less intense than with barley because there is runoff only during strong and exceptional rains, while with barley runoff occurs during quite all rains over 3 mm. Cleaning of the fields during the rainy season could have catastrophic results. Under this climate, we recommend rows with little rain catchment and with an association of corn and string bean to limit destruction of the furrows and soil erosion. (Résumé d'auteur)

A monoclonal antibody-based immunoassay to measure the antibody response against the repeat region of the circumsporozoite protein of Plasmodium falciparum

Background: The malaria vaccine candidate RTS, S/AS01 (GSK Vaccines) induces high IgG concentration against the circumsporozoite protein (CSP) of Plasmodium falciparum. In human vaccine recipients circulating anti-CSP antibody concentrations are associated with protection against infection but appear not to be the correlate of protection. However, in a humanized mouse model of malaria infection prophylactic administration of a human monoclonal antibody (MAL1C), derived from a RTS, S/AS01-immunized volunteer, directed against the CSP repeat region, conveyed full protection in a dose-dependent manner suggesting that antibodies alone are able to prevent P. falciparum infection when present in sufficiently high concentrations. A competition ELISA was developed to measure the presence of MAL1C-like antibodies in polyclonal sera from RTS, S/AS01 vaccine recipients and study their possible contribution to protection against infection. Results: MAL1C-like antibodies present in polyclonal vaccine-induced sera were evaluated for their ability to compete with biotinylated monoclonal antibody MAL1C for binding sites on the capture antigen consisting of the recombinant protein encompassing 32 NANP repeats of CSP (R32LR). Serum samples were taken at different time points from participants in two RTS, S/AS01 vaccine studies (NCT01366534 and NCT01857869). Vaccine-induced protection status of the study participants was determined based on the outcome of experimental challenge with infected mosquito bites after vaccination. Optimal conditions were established to reliably detect MAL1C-like antibodies in polyclonal sera. Polyclonal anti-CSP antibodies and MAL1C-like antibody content were measured in 276 serum samples from RTS, S/AS01 vaccine recipients using the standard ELISA and MAL-1C competition ELISA, respectively. A strong correlation was observed between the results from these assays. However, no correlation was found between the results of either assay and protection against infection. Conclusions: The competition ELISA to measure MAL1C-like antibodies in polyclonal sera from RTS, S/AS01 vaccine recipients was robust and reliable but did not reveal the elusive correlate of protection

Synthesis of Functionalized Few-Layer Graphene Through Fast Electrochemical Expansion of Graphite

International audienc

Oxidation of Porphyrins in the Presence of Nucleophiles: From the Synthesis of Multisubstituted Porphyrins to the Electropolymerization of the Macrocycles

International audienc

Clarifications on the "Comparison Between SMOS, VUA, ASCAT, and ECMWF Soil Moisture Products Over Four Watersheds in U.S."

In a recent paper, Leroux et al. compared three satellite soil moisture data sets (SMOS, AMSR-E, and ASCAT) and ECMWF forecast soil moisture data to in situ measurements over four watersheds located in the United States. Their conclusions stated that SMOS soil moisture retrievals represent "an improvement [in RMSE] by a factor of 2-3 compared with the other products" and that the ASCAT soil moisture data are "very noisy and unstable." In this clarification, the analysis of Leroux et al. is repeated using a newer version of the ASCAT data and additional metrics are provided. It is shown that the ASCAT retrievals are skillful, although they show some unexpected behavior during summer for two of the watersheds. It is also noted that the improvement of SMOS by a factor of 2-3 mentioned by Leroux et al. is driven by differences in bias and only applies relative to AMSR-E and the ECWMF data in the now obsolete version investigated by Leroux et al

Genome-Wide Association Study in BRCA1 Mutation Carriers Identifies Novel Loci Associated with Breast and Ovarian Cancer Risk

BRCA1-associated breast and ovarian cancer risks can be modified by common genetic variants. To identify further cancer risk-modifying loci, we performed a multi-stage GWAS of 11,705 BRCA1 carriers (of whom 5,920 were diagnosed with breast and 1,839 were diagnosed with ovarian cancer), with a further replication in an additional sample of 2,646 BRCA1 carriers. We identified a novel breast cancer risk modifier locus at 1q32 for BRCA1 carriers (rs2290854, P = 2.7×10-8, HR = 1.14, 95% CI: 1.09-1.20). In addition, we identified two novel ovarian cancer risk modifier loci: 17q21.31 (rs17631303, P = 1.4×10-8, HR = 1.27, 95% CI: 1.17-1.38) and 4q32.3 (rs4691139, P = 3.4×10-8, HR = 1.20, 95% CI: 1.17-1.38). The 4q32.3 locus was not associated with ovarian cancer risk in the general population or BRCA2 carriers, suggesting a BRCA1-specific associat

Active Plasmonic Devices with Anisotropic Optical Response: A Step Toward Active Polarizer

International audienc

Conducting polymer/gold nanoparticle hybrid materials: A step toward electroactive plasmonic devices

International audienc

Tunable Electrochemical Switch of the Optical Properties of Metallic Nanoparticles

International audienc