Impact du broyage des granulats de PET sur les propriétés à l'état frais d'un composite cimentaire

National audienceThe works presented herein deal with the recycling of post-consumer packaging made of polyethylene terephthalate (PET) without further transformation beyond crushing. Several crushers are used to obtain PET aggregates with different sizes. The PET particles are substituted to sand according a same volume fraction. 25, 50 and 75% are the substitution rates chosen. Each composition contains only one type of PET grain size. Optical imaging has allowed to observe that the 2 mm-crushed PET exhibited lots of fine particles. Moreover the water absorption rate of industrial PET is lower than 2 mm-crushed PET one. The Water/Cement (W/C) rate decreases with the volume percentage of industrial PET increase while this rate increases with the increase in volume percentage of 2 mm-crushed PET.Les travaux présentés ici portent sur la recyclabilité d'emballages de post consommation à base de polyéthylène téréphtalate (PET) avec comme seule technique de transformation le broyage. Différents broyeurs sont utilisés pour obtenir des granulats de PET de différentes tailles. Les particules de PET ont été substituées au sable selon une même fraction volumique. Les taux de substitution choisis sont 25, 50 et 75%. Un seul type de granulométrie de PET a été utilisé dans chaque composition. On a observé par imagerie optique que le PET broyé à 2 mm présentait beaucoup de fines particules. De plus l'absorption d'eau du PET industriel est plus faible que celle du PET broyé à 2 mm. Le rapport Eau/Ciment (E/C) diminue lorsque le pourcentage volumique du PET industriel augmente tandis que ce rapport augmente avec l'augmentation du pourcentage volumique du PET broyé à 2 mm

ADAPTATION D'UNE MÉTHODOLOGIE DE CYCLES GEL-DÉGEL POUR DES COMPOSITES CIMENTAIRES À BASE DE GRANULATS DE PET

International audienceLes plastiques sont utilisés en grande quantité dans les emballages alimentaires. Leur recyclage est une préoccupation majeure. Une des voies intéressantes est leur valorisation matière au sein de matériaux de construction, elle est la mieux adaptée au Développement Durable. Depuis une dizaine d'années plusieurs études ont été réalisées pour utiliser ces déchets comme granulats dans des matrices cimentaires mais la durabilité de ces composites est encore mal connue. Ce travail est une contribution à l'étude de la durabilité des matériaux formulés avec des granulats issus d'emballages de post consommation à base de polyéthylène téréphtalate (PET) avec comme seule technique de transformation le broyage. Les particules de PET ont été substituées au sable selon une même fraction volumique. Les taux de substitution choisis sont 25, 50 et 75%. Il s'agit de bétons légers présentant une porosité importante et variable suivant le taux de substitution. Une méthodologie de cycles gel-dégel a dû alors être adaptée à ce type de composite cimentaire. Les travaux réalisés ont conduit à choisir la procédure A de la norme ASTM C 666 03. Les différents essais ont permis, pour chacun des taux de substitution, d'établir les couples temps-température permettant de respecter au mieux cette norme

Unraveling the Stratification of an Iron-Oxidizing Microbial Mat by Metatranscriptomics

International audienceA metatranscriptomic approach was used to study community gene expression in a naturally occurring iron-rich microbial mat. Total microbial community RNA was reversely transcribed and sequenced by pyrosequencing. Characterization of expressed gene sequences provided accurate and detailed information of the composition of the transcriptionally active community and revealed phylogenetic and functional stratifications within the mat. Comparison of 16S rRNA reads and delineation of OTUs showed significantly lower values of metatranscriptomic-based richness and diversity in the upper parts of the mat than in the deeper regions. Taxonomic affiliation of rRNA sequences and mRNA genome recruitments indicated that iron-oxidizing bacteria affiliated to the genus Leptothrix, dominated the community in the upper layers of the mat. Surprisingly, type I methanotrophs contributed to the majority of the sequences in the deep layers of the mat. Analysis of mRNA expression patterns showed that genes encoding the three subunits of the particulate methane monooxygenase (pmoCAB) were the most highly expressed in our dataset. These results provide strong hints that iron-oxidation and methane-oxidation occur simultaneously in microbial mats and that both groups of microorganisms are major players in the functioning of this ecosystem

A Shift from Cellular to Humoral Responses Contributes to Innate Immune Memory in the Vector Snail Biomphalaria glabrata

International audienceDiscoveries made over the past ten years have provided evidence that invertebrate anti-parasitic responses may be primed in a sustainable manner, leading to the failure of a secondary encounter with the same pathogen. This phenomenon called " immune priming " or "innate immune memory" was mainly phenomenological. The demonstration of this process remains to be obtained and the underlying mechanisms remain to be discovered and exhaustively tested with rigorous functional and molecular methods, to eliminate all alternative explanations. In order to achieve this ambitious aim, the present study focuses on the Lophotrochozoan snail, Biomphalaria glabrata, in which innate immune memory was recently reported. We provide herein the first evidence that a shift from a cellular immune response (encapsulation) to a humoral immune response (biomphalysin) occurs during the development of innate memory. The molecular characterisation of this process in Biompha-laria/Schistosoma system was undertaken to reconcile mechanisms with phenomena

La meilleure façon de risquer: Vers une exploration des représentations et perceptions du risque propres aux animateurs volontaires

International audienceCet article d’étayage vise à élaborer un cadre, afin de faciliter l’exploration des représentations et perceptions du risque chez les animateurs volontaires. Les Accueils Collectifs de Mineurs (ACM) sont le siège de risques divers, et l’appréhension des risques ne s’engage pas ex nihilo. Nous observons celle-ci sous le prisme de deux dimensions de l’environnement de l’animateur, macro et microsystémiques, intégrant le modèle écologique de développement humain de Bronfenbrenner (1979, 1986) et dont nous tâchons de dessiner les contours. Ce modèle est composé de trois autres sous-ensembles, qu’il conviendra d’explorer ultérieurement

Valorization of Beet Pulps Issued from Sugar Extraction in Cementitious Matrices. Effect of Original Pulp State

Beet sugar manufacturing generates considerable flows of co products among which pulps. At the end of the extraction of sugar, they are rich in water and hard to preserve. They generally undergo an over pressing bringing the proportion of dry matter about 30% and then can be thermally dehydrated and granulated. Over pressed pulps, still wet, keeps very well when sheltered from air. Granulated dried pulps occupy little volume and keep well away from moisture. However, the drying consumes significant amounts of energy. Currently, the main outlet of the pulps is animal feed. But, besides the decline in livestock production connected to the new sugar regulation and to energy problems make indispensable, to maintain the turnover of beet farmhouses, to find new applications to beet pulps. Different ways have been explored. The advantage of a valorization in the form of aggregates in cementitious matrix materials is the use of the co product in its entirety and the improving of the bio based character of construction. However, because energy problems, it was useful to determine the best way to introduce the beet pulp in the process. A comparative study was therefore conducted from over pressed pulps and pellets of the same origin. It appears, at the optimum water content, that mechanical and thermal behavior are little influenced by the original pulp state whatever cement/pulp proportion used. This allows envisaging a valorization of these pulps without going through the stage of thermal dehydration. The results were also compared to those obtained with already marketed ligno cellulosic aggregates. It appears that beet pulps lead to competitive materials

Pulse characterization of optically triggered SiC thyristors

International audienceThis paper deals with the pulse capabilities of 4H-SiC optically triggered thyristors. The device structure and the fabrication process are presented. The results of pulse characterizations are shown. Two types of current pulses were used, a short (pulse width of 10 μs) and a long (pulse width of 650 μs). Peak current densities of 17 kA.cm -2 and 4 kA.cm -2 were attained with short and long pulses respectively. The failures and degradation caused by these experiments are also shown in this paper

Development of a Pacific oyster (Crassostrea gigas) 31,918-feature microarray: identification of reference genes and tissue-enriched expression patterns

Background: Research using the Pacific oyster Crassostrea gigas as a model organism has experienced rapid growth in recent years due to the development of high-throughput molecular technologies. As many as 56,268 EST sequences have been sequenced to date, representing a genome-wide resource that can be used for transcriptomic investigations. Results: In this paper, we developed a Pacific oyster microarray containing oligonucleotides representing 31,918 transcribed sequences selected from the publicly accessible GigasDatabase. This newly designed microarray was used to study the transcriptome of male and female gonads, mantle, gills, posterior adductor muscle, visceral ganglia, hemocytes, labial palps and digestive gland. Statistical analyses identified genes differentially expressed among tissues and clusters of tissue-enriched genes. These genes reflect major tissue-specific functions at the molecular level, such as tissue formation in the mantle, filtering in the gills and labial palps, and reproduction in the gonads. Hierarchical clustering predicted the involvement of unannotated genes in specific functional pathways such as the insulin/NPY pathway, an important pathway under study in our model species. Microarray data also accurately identified reference genes whose mRNA level appeared stable across all the analyzed tissues. Adp-ribosylation factor 1 9arf1) appeared to be the most robust reference for normalizing gene expression data across different tissues and is therefore proposed as a relevant reference gene for further gene expression analysis in the Pacific oyster. Conclusions: This study provides a new transcriptomic tool for studies of oyster biology, which will help in the annotation of its genome and which identifies candidate reference genes for gene expression analysis

Avalanche Diodes with Low Temperature Dependence in 4H-SiC Suitable for Parallel Protection

International audienceAvalanche diodes have been fabricated on 4H-SiC substrate. These diodes show an abrupt avalanche voltage of about 59 V which corresponds to the calculated theoretical one using our previously determined impact ionization coefficients. This avalanche voltage increases by as small as 3.7 mV/K over the investigated temperature range (150K-420K)

Parasite Microbiome Project: Systematic Investigation of Microbiome Dynamics within and across Parasite-Host Interactions.

Understanding how microbiomes affect host resistance, parasite virulence, and parasite-associated diseases requires a collaborative effort between parasitologists, microbial ecologists, virologists, and immunologists. We hereby propose the Parasite Microbiome Project to bring together researchers with complementary expertise and to study the role of microbes in host-parasite interactions. Data from the Parasite Microbiome Project will help identify the mechanisms driving microbiome variation in parasites and infected hosts and how that variation is associated with the ecology and evolution of parasites and their disease outcomes. This is a call to arms to prevent fragmented research endeavors, encourage best practices in experimental approaches, and allow reliable comparative analyses across model systems. It is also an invitation to foundations and national funding agencies to propel the field of parasitology into the microbiome/metagenomic era