Formats techniques, formats communautaires, formats d’engagement : le cas d’une communauté diasporique

A l'image des communautés virtuelles traitées par Howard Rheingold, la plupart des travaux sur cette thématique partent de l'offre technique pour analyser la communauté qui se développe autour de (sur, dans, avec, grâce à) cette infrastructure (l'incertitude sur la préposition qui va qualifier la relation est significative). A partir de cette approche, on débouche aisément sur une adéquation peu interrogée entre offre technique et communauté sans possibilité de comparer les différentes communautés entre elles. Il est en effet impossible à partir de ce point de départ de penser la diversité des supports techniques qui peuvent concourir à faire tenir la communauté en question et à redéfinir ses frontières pertinentes (...)

Characterization of the glass transition in vitreous silica by temperature scanning small-angle X-ray scattering

The temperature dependence of the x-ray scattering in the region below the first sharp diffraction peak was measured for silica glasses with low and high OH content (GE-124 and Corning 7980). Data were obtained upon scanning the temperature at 10, 40 and 80 K/min between 400 K and 1820 K. The measurements resolve, for the first time, the hysteresis between heating and cooling through the glass transition for silica glass, and the data have a better signal to noise ratio than previous light scattering and differential thermal analysis data. For the glass with the higher hydroxyl concentration the glass transition is broader and at a lower temperature. Fits of the data to the Adam-Gibbs-Fulcher equation provide updated kinetic parameters for this very strong glass. The temperature derivative of the observed X-ray scattering matches that of light scattering to within 14%.Comment: EurophysicsLetters, in pres

Analyse de la situation de la Consultation de santé sexuelle Planning familial de Profa

Le présent rapport est structuré de la manière suivante : le chapitre 2 décrit la méthode utilisée ; le chapitre 3 est consacré à l'activité de consultation et le chapitre 4 à l'action communautaire. Le chapitre 5 concerne la notion de centre de référence. Une analyse ciblée de la littérature, ainsi que les consultations de santé sexuelle dans les autres cantons romands sont présentés au chapitre 6. Les conclusions et recommandations sont exposées au chapitre 7

Platelet aggregating activity of lysophosphatidic acids is not related to their calcium ionophore properties

AbstractThe calcium ionophore properties of A23187 and of two lysophosphatidic acid (LPA) analogs (1-palmitoyl- and 1-hexadecyl-sn-glycero-3-phosphate or P-GPA and H-GPA, respectively) were compared using platelet membrane vesicles loaded with 45Ca. Half maximal effect (HME) was obtained at 5 μM and 10 μM for H-GPA and P-GPA, respectively, against 0.7 μM for A23187, which released 2 times more Ca. The three compounds also induced platelet aggregation with a HME at 0.5 μM, 0.3 μM and 0.01 μM for A23187, P-GPA and H-GPA, respectively. The clear dissociation between the two effects appearing for both LPA raises some doubt about the general idea that (lyso) PA participate in cell activation through their calcium ionophore properties

The three lipocalins of egg-white: only Ex-FABP inhibits siderophore-dependent iron sequestration by Salmonella Enteritidis

Salmonella Enteritidis is the most prevalent food-borne pathogen associated with egg-related outbreaks in the European Union. During egg colonization, S. Enteritidis must resist the powerful anti-bacterial activities of egg white (EW) and overcome ovotransferrin-imposed iron-restriction (the most important anti-bacterial mechanism of EW). Many pathogens respond to iron restriction by secreting iron-chelating chemicals called siderophores but EW contains a siderophore-sequestering “lipocalin” protein (Ex-FABP) that is predicted to limit the usefulness of siderophores in EW. S. Enteritidis produces two siderophores: enterobactin, which is strongly bound by Ex-FABP; and the di-glucosylated enterobactin-derivative, salmochelin (a so-called “stealth” siderophore), which is not recognized by Ex-FABP. Thus, production of salmochelin may allow S. Enteritidis to escape Ex-FABP-mediated growth inhibition under iron restriction although it is unclear whether its EW concentration is sufficient to inhibit pathogens. Further, two other lipocalins (Cal-γ and α-1-ovoglycoprotein) are found in EW but their siderophore sequestration potential remains unexplored. In addition, the effect of EW lipocalins on the major EW pathogen, S. Enteritidis, has yet to be reported. We overexpressed and purified the three lipocalins of EW and investigated their ability to interact with the siderophores of S. Enteritidis, as well as their EW concentrations. The results show that Ex-FABP is present in EW at concentrations (5.1 μM) sufficient to inhibit growth of a salmochelin-deficient S. Enteritidis mutant under iron restriction but has little impact on the salmochelin-producing wildtype. Neither Cal-γ nor α-1-ovoglycoprotein bind salmochelin or enterobactin, nor do they inhibit iron-restricted growth of S. Enteritidis. However, both are present in EW at significant concentrations (5.6 and 233 μM, respectively) indicating that α-1-ovoglycoprotein is the 4th most abundant protein in EW, with Cal-γ and Ex-FABP at 11th and 12th most abundant. Further, we confirm the preference (16-fold) of Ex-FABP for the ferrated form (Kd of 5.3 nM) of enterobactin over the iron-free form (Kd of 86.2 nM), and its lack of affinity for salmochelin. In conclusion, our findings show that salmochelin production by S. Enteritidis enables this key egg-associated pathogen to overcome the enterobactin-sequestration activity of Ex-FABP when this lipocalin is provided at levels found in EW

L'apparition de systèmes informatiques autorégulés

National audienceLa conception intégrée de l'automatique avec l'informatique temps réel a renouvelé la science de la régulation des systèmes, qu'il s'agisse d'avions, de machines outils ou d'ordinateurs. Elle est à l'origine d'une technologie invisible aux utilisateurs mais qui permet d'améliorer le contrôle, les performances et la consommation énergétique des dispositifs informatisé

Optimizing Repetitive Computations of Database Triggers Within a Transaction

Projet RODINWe study the problem of optimizing costly repetitive evaluations of database triggers within a transaction. We first show that well known incremental rule evaluation algorithms such as RETE or TREAT are inappropriate for that because they do not consider how repetitive triggerings of rules can be caused by the structure of transaction programs. Therefore, their decision of precomputing and caching some expressions in rule conditions for a later reuse can be erroneous. We assume that transaction programs are represented by their flow graph. We then propose an algorithm that, given a transaction's flow graph, and a set of triggers, constructs a compact data structure called a triggering graph. First, for each possible transaction execution, this graph indicates which rules may be triggered. Second, for every rule $r$ capable of being triggered and fired several times, the graph represents the real «influence» of both the transaction and the rules on $r$. This provides the necessary information for deciding which subexpressions of $r$ are most profitable to cache for the considered transaction

Global gene-expression analysis of the response of Salmonella Enteritidis to egg-white exposure reveals multiple egg-white-imposed stress responses

Chicken egg white protects the embryo from bacterial invaders by presenting an assortment of antagonistic activities that combine together to both kill and inhibit growth. The key features of the egg-white anti-bacterial system are iron restriction, high pH, antibacterial peptides and proteins, and viscosity. Salmonella enterica serovar Enteritidis is the major pathogen responsible for egg-borne infection in humans, which is partly explained by its exceptional capacity for survival under the harsh conditions encountered within egg white. However, at temperatures up to 42 ˚C, egg white exerts a much stronger bactericidal effect on S. Enteritidis than at lower tempertaures, although the mechanism of egg-white-induced killing is only partly understood. Here, for the first time, the impact of exposure of S. Enteritidis to egg white under bactericidal conditions (45 ˚C) is explored by global-expression analysis. A large-scale (18.7% of genome) shift in transcription is revealed suggesting major changes in specific aspects of S. Enteritidis physiology: induction of egg-white related stress-responses (envelope damage, exposure to heat and alkalinity, and translation shutdown); shift in energy metabolism from respiration to fermentation; and enhanced micronutrient provision (due to iron and biotin restriction). Little evidence of DNA damage or redox stress was obtained. Instead, data are consistent with envelope damage resulting in cell death by lysis. A surprise was the high degree of induction of hexonate/hexuronate utilisation genes, despite no evidence indicating the presence of these substrates in egg white