What favors convective aggregation and why?

International audienceThe organization of convection is ubiquitous, but its physical understanding remains limited. One particular type of organization is the spatial self-aggregation of convection, taking the form of cloud clusters, or tropical cyclones in the presence of rotation. We show that several physical processes can give rise to self-aggregation and highlight the key features responsible for it, using idealized simulations. Longwave radiative feedbacks yield a radiative aggregation. In that case, sufficient spatial variability of radiative cooling rates yields a low-level circulation, which induces the upgradient energy transport and radiative-convective instability. Not only do vertically integrated radiative budgets matter but the vertical profile of cooling is also crucial. Convective aggregation is facilitated when downdrafts below clouds are weak (moisture-memory aggregation), and this is sufficient to trigger aggregation in the absence of longwave radiative feedbacks. These results shed some light on the sensitivity of self-aggregation to various parameters, including resolution or domain size

Hierarchical modelling of species sensitivity distribution: development and application to the case of diatoms exposed to several herbicides

The Species Sensitivity Distribution (SSD) is a key tool to assess the ecotoxicological threat of contaminant to biodiversity. It predicts safe concentrations for a contaminant in a community. Widely used, this approach suffers from several drawbacks: i)summarizing the sensitivity of each species by a single value entails a loss of valuable information about the other parameters characterizing the concentration-effect curves; ii)it does not propagate the uncertainty on the critical effect concentration into the SSD; iii)the hazardous concentration estimated with SSD only indicates the threat to biodiversity, without any insight about a global response of the community related to the measured endpoint. We revisited the current SSD approach to account for all the sources of variability and uncertainty into the prediction and to assess a global response for the community. For this purpose, we built a global hierarchical model including the concentration-response model together with the distribution law for the SSD. Working within a Bayesian framework, we were able to compute an SSD taking into account all the uncertainty from the original raw data. From model simulations, it is also possible to extract a quantitative indicator of a global response of the community to the contaminant. We applied this methodology to study the toxicity of 6 herbicides to benthic diatoms from Lake Geneva, measured from biomass reduction

Contribution à la prévision du méandrement du sillage des éoliennes à axe horizontal

La production éolienne industrielle s’organise sous la forme de centrales regroupant de quelques unités à la centaine d’éoliennes. Ces centrales sont disséminées sur le territoire terrestre ou maritime en des lieux soigneusement sélectionnés sur la base de nombreux critères, dont le potentiel éolien. Cela concerne la qualité des vents incidents, l’influence de la complexité géométrique du site mais aussi les interactions aérodynamiques entre éoliennes qui pourraient dégrader la qualité du vent incident et donc la production énergétique. En fonction de la direction des vents, la proximité des éoliennes organisées en parc induit très fréquemment des interactions de sillages entre deux ou plusieurs machines alignées. Le sillage généré par une éolienne se caractérise principalement par un déficit de vitesse du vent et une augmentation de la turbulence sur plusieurs centaines de mètres en aval. L’interaction du sillage d’une éolienne sur une seconde se traduit par une diminution du rendement ainsi qu’une augmentation des charges aérodynamiques fatiguant prématurément les matériaux. De plus, les grandes échelles de la turbulence atmosphérique ont tendance à modifier la trajectoire des sillages éoliens avec un caractère instationnaire, appelé méandrement (« meandering »). Ce phénomène mal quantifié jusqu’à maintenant doit être caractérisé pour être correctement modélisés dans les calculs de prévision d’effets de sillage. La modélisation physique en soufflerie est l’approche utilisée par le laboratoire PRISME pour étudier cette problématique. Cela consiste à reproduire à échelle réduite (de l’ordre du 1/500ème) les propriétés aérodynamiques (moyennes et turbulentes) de la basse couche atmosphérique. Le rotor est modélisé, sur la base du concept de disque actuateur, par un disque poreux et les propriétés stationnaires et instationnaires du sillage lointain sont étudiées par l’intermédiaire de mesures de vitesse par anémométrie fil chaud multi-points, PIV et LDV. Par le biais de ces expériences en soufflerie, des réponses sont apportées sur les causes du méandrement, son amplitude et sa prévision

Assessing Mathematical School Readiness

Early math skills matter for later formal mathematical performances, academic and professional success. Accordingly, it is important to accurately assess mathematical school readiness (MSR) at the beginning of elementary school. This would help identifying children who are at risk of encountering difficulties in math and then stimulate their acquisition of mathematical skills as soon as possible. In the present study, we present a new test that allows professionals working with children (e.g., teachers, school psychologists, speech therapists, and school doctors) to assess children’s MSR when they enter formal schooling in a simple, rapid and efficient manner. 346 children were assessed at the beginning of 1st Grade (6-to-7-year-olds) with a collective test assessing early mathematical abilities (T1). In addition, children’s math skills were evaluated with classical curriculum math tests at T1 and a year later, in 2nd Grade (T2, 7-to-8-year-olds). After assessing internal consistency, three tasks were retained for the final version of the MSR test. Test performance confirmed to be essentially unidimensional and systematically related to the scores children obtained in classical tests in 1st and 2nd Grade. By using the present MSR test, it is possible to identify pupils at risk of developing low math skills right from the start of formal schooling in 1st Grade. Such a tool is needed, as children’s level in math at school beginning (or school readiness) is known to be foundational for their future academic and professional carrier

Pancreatic islet cells isolation and transplantation into the bone marrow

Bone marrow is currently being considered as an alternative site for pancreatic islet transplantation. The goal of the present review is to report preclinical and clinical studies taking advantage of this new implantation site. Preclinical studies in mice demonstrated that syngeneic islets could survive in bone marrow indefinitely with a higher success in providing euglycemia compared to islets transplanted into the traditionally used implantation site, namely, the liver. In concordant and discordant xenogeneic models, the immune response was more stringent when islets were transplanted to the bone marrow as compared to the traditional implantation site in rodents, the kidney capsule. As demonstrated by histology, cellular and humoral rejection was prevented by islets protected by micro-encapsulation in calcium-alginate beads, and a similar degree of fibrotic reaction was induced at both site, although functional studies in diabetic animals are still needed. In clinical settings, a pilot study of four patients who received islet auto-transplantation into the bone marrow after a total pancreatectomy had been showed to be safe and feasible. Three out of four patients had a functioning graft, as measured by serum C-peptide, at an average follow-up of 545 ± 369 days. In conclusion, islet transplantation into the bone marrow may be a viable alternative to the liver as an implantation site, particularly with the perspective of transplanting encapsulated xenogeneic islets. Meanwhile, the efficacy of immunosuppressive drugs would still require to be evaluated in allogeneic and xenogeneic preclinical models of islet transplantation into the bone marrow

PECAM-1 engagement counteracts ICAM-1-induced signaling in brain vascular endothelial cells

Interactions between leukocytes and vascular endothelial cells are mediated by a complex set of membrane adhesion molecules which transduce bi-directional signals in both cell types. Endothelium of the cerebral blood vessels, which constitute the blood–brain barrier, strictly controls adhesion and trafficking of leukocytes into the brain. Investigating signaling pathways triggered by the engagement of adhesion molecules expressed on brain endothelial cells, we previously documented the role of ICAM-1 in activation of the tyrosine phosphorylation of several actin-binding proteins and subsequent rearrangements of the actin cytoskeleton. In the present study, we show that, whereas PECAM-1 is known to control positively the trans-endothelial migration of leukocytes via homophilic interactions between leukocytes and endothelial cells, PECAM-1 engagement on brain endothelial surface unexpectedly counteracts the ICAM-1-induced tyrosine phosphorylation of cortactin and rearrangements of the actin cytoskeleton. We present evidence that the PECAM-1-associated tyrosine phosphatase SHP-2 is required for ICAM-1 signaling, suggesting that its activity might crucially contribute to the regulation of ICAM-1 signaling by PECAM-1. Our findings reveal a novel activity for PECAM-1 which, by counteracting ICAM-1-induced activation, could directly contribute to limit activation and maintain integrity of brain vascular endothelium

Reemergence of Syphilis in Martinique, 2001–2008

Syphilis reemerged in Martinique in 2004 and initially affected 3 HIV-infected patients. By March 2008, syphilis was diagnosed for 37 men and 18 women. As of October 31, 2009, this outbreak had not yet been brought under control. It initially affected mainly men who had sex with men before it spread to heterosexual persons, minority group members, and crack cocaine users

Family-focused contextual factors associated with lifestyle patterns in young children from two mother-offspring cohorts : GUSTO and EDEN

Background Integrated patterns of energy balance-related behaviours of preschool children in Asia are sparse, with few comparative analyses. Purpose Using cohorts in Singapore (GUSTO) and France (EDEN), we characterized lifestyle patterns of children and investigated their associations with family-focused contextual factors. Methods Ten behavioural variables related to child's diet, walking, outdoor play and screen time were ascertained by parental questionnaires at age 5-6 years. Using principal component analysis, sex-specific lifestyle patterns were derived independently for 630 GUSTO and 989 EDEN children. Contextual variables were organised into distal (family socio-economics, demographics), intermediate (parental health, lifestyle habits) and proximal (parent-child interaction factors) levels of influence and analysed with hierarchical linear regression. Results Three broadly similar lifestyle patterns were identified in both cohorts: "discretionary consumption and high screen time", "fruit, vegetables, and low screen time" and "high outdoor playtime and walking". The latter two patterns showed small differences between cohorts and sexes. The "discretionary consumption and high screen time" pattern was consistently similar in both cohorts; distal associated factors were lower maternal education (EDEN boys), no younger siblings (GUSTO boys) and Malay/Indian ethnicity (GUSTO), while intermediate and proximal associated factors in both cohorts and sexes were poor maternal diets during pregnancy, parents allowing high child control over food intake, snacking between meals and having television on while eating. Conclusions Three similar lifestyle patterns were observed among preschool children in Singapore and France. There were more common associated proximal factors than distal ones. Cohort specific family-focused contextual factors likely reflect differences in social and cultural settings. Findings will aid development of strategies to improve child health.Peer reviewe