Étude de l’adhésion fibre/matrice d’un matériau composite expansé lors du moussage

Dans une optique d’allégement des structures, les polymères et matériaux composites à matrice organique expansés font leur apparition dans l’industrie. Cependant, leur optimisation est plus complexe que celle de leurs homologues denses, car il faut obtenir une adéquation entre les réactions de polymérisation du polymère et de moussage de l’agent gonflant. De plus, une bonne adhésion fibre/matrice est nécessaire pour obtenir des structures homogènes en termes de répartition et de diamètre de porosités. Une mauvaise adhésion des fibres peut être responsable d’une nucléation hétérogène du polymère, avec l’apparition de grosses porosités, responsables d’une diminution des propriétés mécaniques du matériau

Screening of Phytophagous and Xylophagous Insects Guts Microbiota Abilities to Degrade Lignocellulose in Bioreactor

Microbial consortia producing specific enzymatic cocktails are present in the gut of phytophagous and xylophagous insects; they are known to be the most efficient ecosystems to degrade lignocellulose. Here, the ability of these consortia to degrade ex vivo lignocellulosic biomass in anaerobic bioreactors was characterized in term of bioprocess performances, enzymatic activities and bacterial community structure. In a preliminary screening, guts of Ergates faber (beetle), Potosia cuprea (chafer), Gromphadorrhina portentosa (cockroach), Locusta migratoria (locust), and Gryllus bimaculatus (cricket) were inoculated in anaerobic batch reactors, in presence of grounded wheat straw at neutral pH. A short duration fermentation of less than 8 days was observed and was related to a drop of pH from 7 to below 4.5, leading to an interruption of gas and metabolites production. Consistently, a maximum of 180 mgeq.COD of metabolites accumulated in the medium, which was related to a low degradation of the lignocellulosic biomass, with a maximum of 5 and 2.2% observed for chafer and locust gut consortia. The initial cell-bound and extracellular enzyme activities, i.e., xylanase and β-endoglucanase, were similar to values observed in the literature. Wheat straw fermentation in bioreactors leads to an increase of cell-bounded enzyme activities, with an increase of 145% for cockroach xylanase activity. Bacterial community structures were insect dependent and mainly composed of Clostridia, Bacteroidia and Gammaproteobacteria. Improvement of lignocellulose biodegradation was operated in successive batch mode at pH 8 using the most interesting consortia, i.e., locust, cockroaches and chafer gut consortia. In these conditions, lignocellulose degradation increased significantly: 8.4, 10.5, and 21.0% of the initial COD were degraded for chafer, cockroaches and locusts, respectively in 15 days. Consistently, xylanase activity tripled for the three consortia, attesting the improvement of the process. Bacteroidia was the major bacterial class represented in the bacterial community for all consortia, followed by Clostridia and Gammaproteobacteria classes. This work demonstrates the possibility to maintain apart of insect gut biological activity ex vivo and shows that lignocellulose biodegradation can be improved by using a biomimetic approach. These results bring new insights for the optimization of lignocellulose degradation in bioreactors

The GEOTRACES Intermediate Data Product 2014

The GEOTRACES Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEIs) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The IDP2014 covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The TEI data in the IDP2014 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including ASCII spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the IDP2014 also contains data quality flags and 1-? data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2014 data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes

Pour une histoire culturelle de l’architecture. Essais offerts à Anne-Marie Châtelet

International audienceEn architecture, l’histoire culturelle confronte la connaissance du bâti, de ses dispositions architecturales et de son inscription urbaine à l’exploration des milieux socioculturels qui l’ont façonné. Suivant une telle approche, cet ouvrage offre des regards variés autour de quatre thèmes: les types d’édifices; les figures et les groupes professionnels du champ architectural; la circulation et les transferts des formes et des idées; l’écriture de l’histoire et l’enseignement de l’architecture. Concentré sur l’Europe occidentale de la période contemporaine, Pour une histoire culturelle de l’architecture traverse les époques et les lieux, révélant l’ampleur de ce domaine de recherche.La quarantaine d’essais rassemblés dans ce volume rend ainsi hommage à la riche carrière d’enseignante-chercheure d’Anne-Marie Châtelet. Ayant contribué de manière remarquable au développement de l’histoire et à l’enseignement de l’architecture, la destinataire de ces mélanges est ici saluée par ses étudiants, ses collègues et ses amis, avec des textes qui reflètent la profondeur et la subtilité de sa vision

Pour une histoire culturelle de l’architecture. Essais offerts à Anne-Marie Châtelet

International audienceEn architecture, l’histoire culturelle confronte la connaissance du bâti, de ses dispositions architecturales et de son inscription urbaine à l’exploration des milieux socioculturels qui l’ont façonné. Suivant une telle approche, cet ouvrage offre des regards variés autour de quatre thèmes: les types d’édifices; les figures et les groupes professionnels du champ architectural; la circulation et les transferts des formes et des idées; l’écriture de l’histoire et l’enseignement de l’architecture. Concentré sur l’Europe occidentale de la période contemporaine, Pour une histoire culturelle de l’architecture traverse les époques et les lieux, révélant l’ampleur de ce domaine de recherche.La quarantaine d’essais rassemblés dans ce volume rend ainsi hommage à la riche carrière d’enseignante-chercheure d’Anne-Marie Châtelet. Ayant contribué de manière remarquable au développement de l’histoire et à l’enseignement de l’architecture, la destinataire de ces mélanges est ici saluée par ses étudiants, ses collègues et ses amis, avec des textes qui reflètent la profondeur et la subtilité de sa vision

Iron isotopes reveal distinct dissolved iron sources and pathways in the intermediate versus deep Southern Ocean

As an essential micronutrient, iron plays a key role in oceanic biogeochemistry. It is therefore linked to the global carbon cycle and climate. Here, we report a dissolved iron (DFe) isotope section in the South Atlantic and Southern Ocean. Throughout the section, a striking DFe isotope minimum (light iron) is observed at intermediate depths (200–1,300 m), contrasting with heavier isotopic composition in deep waters. This unambiguously demonstrates distinct DFe sources and processes dominating the iron cycle in the intermediate and deep layers, a feature impossible to see with only iron concentration data largely used thus far in chemical oceanography. At intermediate depths, the data suggest that the dominant DFe sources are linked to organic matter remineralization, either in the water column or at continental margins. In deeper layers, however, abiotic non-reductive release of Fe (desorption, dissolution) from particulate iron—notably lithogenic—likely dominates. These results go against the common but oversimplified view that remineralization of organic matter is the major pathway releasing DFe throughout the water column in the open ocean. They suggest that the oceanic iron cycle, and therefore oceanic primary production and climate, could be more sensitive than previously thought to continental erosion (providing lithogenic particles to the ocean), particle transport within the ocean, dissolved/particle interactions, and deep water upwelling. These processes could also impact the cycles of other elements, including nutrients