139 research outputs found

    Détection améliorée du Staphylococcus aureus résistant à la méticilline (SARM) et de l’entérocoque résistant à la vancomycine (ERV)

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    Le SARM et l’ERV sont deux bactéries responsables d’infections nosocomiales importantes. Elles sont retrouvées au sein des différents centres hospitaliers à travers le monde et leur présence cause de grands problèmes en santé publique. Elles constituent notamment une cause majeure de complication des soins de santé avec, en conséquence, une augmentation de la mortalité et de la morbidité, une prolongation de l’hospitalisation et une hausse importante des coûts de santé (INSPQ). La détection rapide du SARM et de l’ERV permettrait un meilleur contrôle de ces maladies nosocomiales. Présentement, le dépistage se fait séparément. Afin de réduire le temps d’exécution des analyses, nous proposons de combiner le dépistage des 2 microorganismes. Le projet consistait au développement d’une méthode d’analyse diagnostique pour la détection simultanée du SARM et de l’ERV par PCR. Par la suite, nous avons procédé à la validation de la méthode sur 99 spécimens de patients. La réalisation de ce projet de recherche se scinde en trois étapes importantes : 1) l’élaboration d’un nouveau bouillon de culture permettant la croissance du SARM et de l’ERV, 2) la mise au point de la PCR en temps réel et finalement, 3) la validation de cette méthode grâce à un nombre significatif de spécimens de patients. Nous avons trouvé qu’un nouveau bouillon de culture, contenant 25 g/L de NaCl, d’aztréonam et de céfotaxime permettait la croissance concomitante du SARM et de l’ERV tout en inhibant la croissance du SASM et des entérobactéries. Notre PCR multiplex permet l’amplification du SARM traditionnel et SARM-AC, de la souche récemment découverte en Europe ainsi que les 2 principaux génotypes d’ERV. Nous avons validé ces deux innovations auprès de 99 participants. Analysées par la méthode de référence, la sensibilité et la spécificité de notre bouillon sont de 50% et de 95% respectivement pour le SARM. Analysée par notre PCR multiplex, la sensibilité augmente à 92,8%. La sensibilité et la spécificité de notre bouillon avec notre PCR multiplex ERV sont de 100%. La validation du nouveau bouillon (1D) a démontré qu’il est aussi efficace voire plus que le bouillon utilisé actuellement. La nouvelle PCR permet l’amplification du SARM et de l’ERV simultanément dans un même programme PCR

    Contribution of epilithic diatoms to benthic−pelagic coupling in a temperate river

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    Water residence time in the middle course of rivers is often too short to allow substantial phytoplankton development, and primary production is essentially provided by benthic phototrophic biofilms. However, cells occurring in the water column might derive from biofilm microalgae, and, reciprocally, sedimenting microalgae could represent a continuous source of colonizers for benthic biofilms. A comparative study of biofilm and pelagic microphytic communities (with special focus on diatoms) was carried out over 15 mo in the Garonne River, France. Diatoms dominated both biofilm and pelagic microphytic communities. Typically benthic diatoms were found in high abundance in the water column, and their biomass in the water was correlated with their biomass in the biofilm, indicating the benthic origin of these cells. Variations in river discharge and temperature drove the temporal distribution of benthic and pelagic communities: under high flow mixing (winter) communities showed the greatest similarity, and during low flow (summer)they differed the most. Even during low flow, typical benthic species were observed in the water column, indicating that benthic−pelagic exchanges were not exclusively due to high water flow. Moreover, during low flow periods, planktonic diatoms typically settled within biofilms, presumably because of higher water residence times, and/or upstream reservoir flushing

    Bitwise Regularity Coefficients as a Tool for Deception Analysis of a Genetic Algorithm

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    Projet FRACTALESWe present in this paper a theoretical analysis that relates an irregularity measure of a fitness function to the so-called GA-deception. This approach is a con­ti­nua­tion of a work that has presented a deception a­na­ly­sis of Hölder functions. The analysis developed here is a generalization of this work in two ways¸: we first use a «bitwise regularity» instead of a Hölder exponent as a basis for our deception analysis, second, we perform a similar deception analysis of a GA with uniform crossover. We finally propose to use the bitwise regularity coefficients in order to analyze the influence of a chromosome encoding on the GA efficiency, and present experiments with bits permutations and Gray encoding

    The relationship between epilithic biofilm stability and its associated meiofauna under two patterns of flood disturbance

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    Habitat stability is an important driver of ecological community composition and development. River epilithic biofilms are particularly unstable habitats for the establishment of benthic communities because they are regularly disturbed by floods. Our aim was to determine the influence of habitat instability on meiobenthic organisms. We hypothesized that hydrologic variables are the most important predictors of meiofauna distribution. We monitored epilithic communities (meiofauna and microalgae) with a high sampling frequency during 2 sampling periods with contrasting hydrodynamic patterns in a temperate river (the Garonne, France). Nematodes and rotifers dominated meiofaunal assemblages. The critical flow velocity threshold for their maintenance in the biofilm was ,30 cm/s, a result suggesting that meiofauna can resist higher flow velocity within the biofilm than within sediments. Nematode distribution was primarily influenced by the duration of undisturbed periods, whereas rotifer distribution was also correlated with the thickness of the biofilm. During the periods after floods, rotifers were faster colonizers than nematodes. Collectively, our results show that flow regime was an essential driver for biofilm community development

    Long proleptic and sylleptic shoots in peach (Prunus persica L. Batsch) trees have similar, predetermined, maximum numbers of nodes and bud fate patterns

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    Background and Aims In peach (Prunus persica) trees, three types of shoots can be distinguished depending on the time of their appearance: sylleptic, proleptic and epicormic. On proleptic shoots, an average of ten phytomers are preformed in dormant buds prior to shoot growth after bud-break, whereas all phytomers are considered neoformed in sylleptic and epicormic shoots. However, casual observations indicated that proleptic and sylleptic shoots appear quite similar in number of phytomers and structure in spite of their different origins. The goal of this research was to test the hypothesis that both proleptic and sylleptic shoots exhibit similar growth characteristics by analysing their node numbers and bud fate patterns. If their growth characteristics are similar, it would indicate that the structure of both types of shoots is primarily under genetic rather than environmental control. Methods The number of phytomers and bud fate patterns of proleptic and sylleptic shoots of four peach cultivars grown in the same location (Winters, California) were analysed and characterized using hidden semi-Markov models. Field data were collected during winter 2016, just prior to floral bud-break. Key Results Sylleptic shoots tended to have slightly fewer phytomers than proleptic shoots of the same cultivars. The bud fate patterns along proleptic and sylleptic shoots were remarkably similar for all the cultivars, although proleptic shoots started growing earlier (at least 1 month) in the spring than sylleptic shoots. Conclusions This study provides strong evidence for the semi-deterministic nature of both proleptic and sylleptic shoots across four peach cultivars in terms of number of phytomers and bud fate patterns along shoots. It is apparent that the overall structure of shoots with similar numbers of phytomers was under similar genetic control for the two shoot types. Understanding shoot structural characteristics can aid in phenotypic characterization of vegetative growth of trees and in providing a foundation for vegetative management of fruit trees in horticultural settings.info:eu-repo/semantics/acceptedVersio

    Etude expérimentale à l'échelle intra-cerne de propriétés mécaniques du bois vert de peuplier au cours de sa maturation par des essais de tractions cycliques

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    Les arbres régulent l'orientation de leurs axes afin d'assurer leur stabilité mécanique et l'acquisition de la lumière. Pour ce faire, ils adaptent les propriétés mécaniques du bois qu'ils créent (formation de bois de réaction). L'objet de ce travail est d'étudier l'évolution des propriétés mécaniques du bois d'arbres inclinés au cours du processus de maturation. Les résultats issus d'une large campagne expérimentale mettent en évidence le comportement mécanique singulier du bois vert (rigidification sous contrainte) ainsi que des phénomènes de maturation complexes

    Atelier "Vivre en Ville" : modes de vie en périphérie : les pratiques dans les centres commerciaux, modes d'habiter en péri-urbain

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    Parmi tous les phénomènes de centralité et de périphérie, sources de multiples observations depuis ces dernières décennies, nous avons choisi d'évoquer au cours de la journée d' atelier « Vivre en Ville » du mois de juillet 1999 , deux points précis qui concernent les pratiques et les modes de vie :-dans les centres commerciaux de périphérie en abordant le thème selon trois entrées :•une étude réalisée dans l'agglomération nantaise visant à appréhender les pratiques et les perceptions d'usagers de centres commerciaux,•une approche par I'ETHOLOGIE, visant à étudier les comportements des utilisateurs d'un centre commercial de région parisienne•une entrée par la SEMIOTIQUE permettant de rendre compte des types de parcours des individus dans l'espace commercial-les modes d' habiter en péri-urbain : à partir d'une étude réalisée dans le pays d'Aix qui a permis de mettre en évidence certaines valeurs, certains attributs de ces nouveaux lieux de centralité.Comment vivent les habitants du péri-urbain ? Qu'est-ce qu'ils en pensent ? Qu'est-ce qu'ils en disent ?Quelle est la place du local ? de l'agglomération ?Ce document reprend dans sa totalité les interventions de la journée sur ces thèmes

    Multi-scale high-throughput phenotyping of apple architectural and functional traits in orchard reveals genotypic variability under contrasted watering regimes

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    Despite previous reports on the genotypic variation of architectural and functional traits in fruit trees, phenotyping large populations in the field remains challenging. In this study, we used high-throughput phenotyping methods on an apple tree core-collection (1000 individuals) grown under contrasted watering regimes. First, architectural phenotyping was achieved using T-LiDAR scans for estimating convex and alpha hull volumes and the silhouette to total leaf area ratio (STAR). Second, a semi-empirical index (IPL) was computed from chlorophyll fluorescence measurements, as a proxy for leaf photosynthesis. Last, thermal infrared and multispectral airborne imaging was used for computing canopy temperature variations, water deficit, and vegetation indices. All traits estimated by these methods were compared to low-throughput in planta measurements. Vegetation indices and alpha hull volumes were significantly correlated with tree leaf area and trunk cross sectional area, while IPL values showed strong correlations with photosynthesis measurements collected on an independent leaf dataset. By contrast, correlations between stomatal conductance and canopy temperature estimated from airborne images were lower, emphasizing discrepancies across measurement scales. High heritability values were obtained for almost all the traits except leaf photosynthesis, likely due to large intra-tree variation. Genotypic means were used in a clustering procedure that defined six classes of architectural and functional combinations. Differences between groups showed several combinations between architectural and functional traits, suggesting independent genetic controls. This study demonstrates the feasibility and relevance of combining multi-scale high-throughput methods and paves the way to explore the genetic bases of architectural and functional variations in woody crops in field conditions

    A Tale of Two Oxidation States: Bacterial Colonization of Arsenic-Rich Environments

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    Microbial biotransformations have a major impact on contamination by toxic elements, which threatens public health in developing and industrial countries. Finding a means of preserving natural environments—including ground and surface waters—from arsenic constitutes a major challenge facing modern society. Although this metalloid is ubiquitous on Earth, thus far no bacterium thriving in arsenic-contaminated environments has been fully characterized. In-depth exploration of the genome of the β-proteobacterium Herminiimonas arsenicoxydans with regard to physiology, genetics, and proteomics, revealed that it possesses heretofore unsuspected mechanisms for coping with arsenic. Aside from multiple biochemical processes such as arsenic oxidation, reduction, and efflux, H. arsenicoxydans also exhibits positive chemotaxis and motility towards arsenic and metalloid scavenging by exopolysaccharides. These observations demonstrate the existence of a novel strategy to efficiently colonize arsenic-rich environments, which extends beyond oxidoreduction reactions. Such a microbial mechanism of detoxification, which is possibly exploitable for bioremediation applications of contaminated sites, may have played a crucial role in the occupation of ancient ecological niches on earth
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