866 research outputs found

    Setting-up rules to characterize microsegregation

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    Characterization of chemical heterogeneities such as microsegregation resulting from solidification of metallic alloys is most often performed by EDS or WDS microanalysis with spot measurements located at corners of a regular grid. Rather than attempting a theoretical treatment of the statistics of such analyses, the quality of the procedure has been investigated by implementing “measurement” grids on numerical images that mimic solidification structures. Microstructures either with no geometrical constraints (uniform distribution of the solid nuclei) or with limited constraints that give some periodicity have been investigated. Systematic analysis of the effect of the location and size of the “measurement” grid enlightens the procedures which should be followed to minimize bias

    ModuleOrganizer: detecting modules in families of transposable elements

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    <p>Abstract</p> <p>Background</p> <p>Most known eukaryotic genomes contain mobile copied elements called transposable elements. In some species, these elements account for the majority of the genome sequence. They have been subject to many mutations and other genomic events (copies, deletions, captures) during transposition. The identification of these transformations remains a difficult issue. The study of families of transposable elements is generally founded on a multiple alignment of their sequences, a critical step that is adapted to transposons containing mostly localized nucleotide mutations. Many transposons that have lost their protein-coding capacity have undergone more complex rearrangements, needing the development of more complex methods in order to characterize the architecture of sequence variations.</p> <p>Results</p> <p>In this study, we introduce the concept of a <it>transposable element module</it>, a flexible motif present in at least two sequences of a family of transposable elements and built on a succession of maximal repeats. The paper proposes an assembly method working on a set of exact maximal repeats of a set of sequences to create such modules. It results in a graphical view of sequences segmented into modules, a representation that allows a flexible analysis of the transformations that have occurred between them. We have chosen as a demonstration data set in depth analysis of the transposable element Foldback in <it>Drosophila melanogaster</it>. Comparison with multiple alignment methods shows that our method is more sensitive for highly variable sequences. The study of this family and the two other families AtREP21 and SIDER2 reveals new copies of very different sizes and various combinations of modules which show the potential of our method.</p> <p>Conclusions</p> <p>ModuleOrganizer is available on the Genouest bioinformatics center at <url>http://moduleorganizer.genouest.org</url></p

    A Pressure Based Compressible Solver for Electric Arc-plasma Simulation

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    The electric arc discharge in a liquid medium is used in several applications such as the sterilization of the liquid by UV radiation, the fracturing of rocks by shock wave, the circuit breakers in oil bath or the forming of mechanical parts. Thus, describing the physics of the arc in a liquid and in particular its interaction with a liquid interface is an important issue to better characterize this type of configuration. However, such a challenging task requires to couple high-fidelity solver for compressible two-phase flows with liquid phase change and a plasma solver to describe the plasma and its interaction with the bubble. To study this type of medium, we use a compressible formulation of the fluid equations. For this purpose, a pressure based solver has been developed for the computation of the energy conservation equation. Moreover, our numerical model uses the immersed boundary method to simulate the solid electrodes. The numerical model is briefly described in this paper and the first results of the electric arc discharge in steam water are presented. To our knowledge this pressure based model has never been used to describe plasmas and electric arc discharge

    Why underserved patients do not consult their general practitioner for depression: results of a qualitative and a quantitative survey at a free outpatient clinic in Paris, France

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    International audienceBackground : The prevalence of depression in the general population is 5 to 10% but can exceed 50% in the most socially vulnerable populations. The perceptions of this disease are widely described in the literature, but no research has been carried out in France to explain the reasons for not consulting a general practitioner during a depressive episode, particularly in people in the most precarious situations. The objective of this study was to describe the reasons for not seeking primary care during a depressive episode in a socially vulnerable population.Methods : An exploratory sequential design with a preliminary qualitative study using a phenomenological approach. Subsequently, themes that emerged from the qualitative analysis were used in a questionnaire administered in a cross-sectional observational study at a free outpatient clinic in Paris in 2010. Lastly, a logistic regression analysis was performed.Results : The qualitative analysis revealed four aspects that explain the non-consulting of a general practitioner during a depressive episode: the negative perception of treatment, the negative perception of the disease, the importance of the social environment, and the doctor-patient relationship. The quantitative analysis showed that close to 60% of the patients who visited the free clinic were depressed and that only half of them had talked with a care provider. The results of the statistical analysis are in line with those of the qualitative analysis, since the most common reasons for not seeing a general practitioner were the negative perception of the disease (especially among the men and foreigners) and its treatments (more often among the men and French nationals).Conclusions : Close to 50% of the depressed individuals did not seek primary care during a depressive episode, and close to 80% of them would have liked their mental health to be discussed more often by a health professional. Better information on depression and its treatments, and more-systematic screening by primary care personnel would improve the treatment of depressed patients, especially those in the most precarious situations

    Composition and Diversity of Ant Species into Leaf Litter of Two Fragments of a Semi-Deciduous Seasonal Forest in the Atlantic Forest Biome in Barra do Choça, Bahia, Brazil

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    We present here the preliminary results of a study of leaf litter ant diversity in remnant areas of semi-deciduous seasonal forests in the Atlantic Forest biome. Standardized collections were made in 2011, using pitfall and Winkler traps in two fragments of native forest belonging to the municipality of Barra do Choça in the micro-region of the Planalto da Conquista, in Southwestern Bahia State, Brazil; 107 species from 37 ant genera and 9 subfamilies were collected. The observed richness was high, and the diversity indices (Shannon-Wiener) of the two fragments suggest that in spite of being strongly impacted by anthropogenic actions, they maintained a high faunal diversity levels, similar to those observed in other original Atlantic Forest sites in Bahia State. Analyses of the accumulated species richness curves and estimated richnesses (Jackknife 2), however, demonstrated that the survey efforts expended were not sufficient to capture all of the species present. The high observed numbers of unique species, smooth curves of the accumulated richness graphs, and high values of estimated richness suggested that the survey areas were quite heterogeneous. These results furnished new information concerning regional biodiversity that will be useful as initial references for continuing studies of fragmentation processes in the region

    Effect of vortex generator on the boundary layer detachment on NACA0015 2D foil

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    Control of detachment of the boundary layer around a foil found many applications in various configurations for aircraft the ability to suppress or delay the separation phenomenon leads to enhanced levels of lift, reduce noise and drag. Many studies have been experimentally conducted to test the effectiveness of different actuators. For example, regarding the methods called "active" which introduce external energy into the fluid, it distinguishes the use of movable walls Modi et al. [1], methods based on suction or blowing Wygnanski [2], McCormick [3], acoustic methods Collins [4], thermal Chang [5] or electromagnetic Gad-el-Hak [6]. In recent years, synthetic jets have been used to control flow separation and to stabilize the boundary layer by adding/removing momentum with the formation of vortical structures Wygnanski [7]. More recently, Gilarranz et al. [8] performed a study of flow separation over NACA0015 airfoil with synthetic jets control, but the modification by the control of the boundary layer has not been clearly identify

    Elaboration of a biotic index of pollution using macroinvertebrates for the monitoring of Lake Nokoué in Benin

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    A study on the relationships between the physicochemical parameters and of the macroinvertebrates of the Lake Nokoué was carried out for the purpose of developing a biotic index of pollution. A total of 96 stations were prospected twice during the flooding and the dry seasons from September 2004 to February 2006. At each station, seven physicochemical parameters were measured and macroinvertebrates were collected. Canonical analyses of correspondence were used to show the relations between the parameters of the environment and the macroinvertebrates. A self-organizing map (SOM) of Kohonen allows the categorization of the studied stations into four groups according to different degrees of pollution. Rough scores were allotted to each taxon according to its abundance in the various groups of stations determined by the SOM for each campaign. A synthesis of the data obtained from the four field surveys allows the assignment of a score to each taxon according to its abundance in the different groups of stations. A biotic index was developed and used for the evaluation of the level of pollution of the stations studied. It then emerged that the borders of the lake present a «poor quality» of water; however, during the dry season there is slight improvement.© 2015 International Formulae Group. All rights reserved.Keywords: Biotic index, pollution, invertebrates, lagoons, Benin, West Afric
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