Oscillations in the expression of a self-repressed gene induced by a slow transcriptional dynamics

We revisit the dynamics of a gene repressed by its own protein in the case where the transcription rate does not adapt instantaneously to protein concentration but is a dynamical variable. We derive analytical criteria for the appearance of sustained oscillations and find that they require degradation mechanisms much less nonlinear than for infinitely fast regulation. Deterministic predictions are also compared with stochastic simulations of this minimal genetic oscillator

Oscillations in the expression of a self-repressed gene induced by a slow transcriptional dynamics

We revisit the dynamics of a gene repressed by its own protein in the case where the transcription rate does not adapt instantaneously to protein concentration but is a dynamical variable. We derive analytical criteria for the appearance of sustained oscillations and find that they require degradation mechanisms much less nonlinear than for infinitely fast regulation. Deterministic predictions are also compared with stochastic simulations of this minimal genetic oscillator

Détection et localisation d'objets stationnaires par une paire de caméras PTZ

Session "Articles"National audienceDans ce papier, nous proposons une approche originale pour détecter et localiser des objets stationnaires sur une scène étendue en exploitant une paire de caméras PTZ. Nous proposons deux contributions principales. Tout d'abord, nous présentons une méthode de détection et de segmentation d'objets stationnaires. Celle-ci est basée sur la réidentification de descripteurs de l'avant-plan et une segmentation de ces blobs en objets à l'aide de champs de Markov. La seconde contribution concerne la mise en correspondance entre les deux PTZ des silhouettes d'objets détectées dans chaque image

Un nouvel indicateur intégré d’évaluation des dégâts occasionnés aux grappes par des bioagresseurs majeurs au vignoble

Communication faite au cours du colloque DinABio2013, 13 et 14 novembre 2013; Tours, FranceAn original and integrative evaluation indicator has been developed to quantify the cumulated damage from major pests and diseases affecting grape bunches: downy mildew, powdery mildew, gray mould and tortricid moths. It made it possible to estimate the associated crop losses and to relate them to the plant protection strategy in different modes of production (organic farming, in-transition, conventional). Thus, overall plant losses were higher in 2012 than in 2011. The in-transition growers’ strategy, with reduced copper doses but increased numbers of sprays, led to a 20% increase in average severity on bunches (essentially due to Downy mildew). The more pragmatic approach of experienced organic growers and conventional ones (higher doses and fewer sprays) reduced the yield losses. The proposed indicator is used for two purposes, i) evaluating the quantitative losses due to pest attacksand ii) differentiating them from other non-pest ones. A more detailed analysis including the impact on performance will be achieved and published soon.Un indicateur d’évaluation, l’IEDG (Indicateur d’Evaluation des Dégâts sur Grappes), a été mis au point pour quantifier les dégâts cumulés dus aux principaux bioagresseurs affectant les grappes de raisin : mildiou, oïdium, pourriture grise et tordeuses. Il permet d’estimer la perte de récolte imputable au cortège parasitaire et de faire le lien avec la stratégie phytosanitaire adoptée (caractérisée ici par l’IFT) et le mode de production (AB, conversion, conventionnel). Ainsi, les pertes sanitaires ont été supérieures en 2012 par rapport à 2011. La stratégie phytosanitaire des viticulteurs en conversion, basée sur des réductions de dose de cuivre de près de 80% et des passages plus nombreux dans les parcelles, n’a pas été efficiente en 2012 avec des sévérités proches de 20% sur grappe, essentiellement dues au mildiou. L’utilisation de doses d’applications supérieures et moins de passages dans les parcelles limite les dommages chez les autres viticulteurs. L’indicateur proposé permet d’évaluer les pertes quantitatives générées par les attaques de bioagresseurs et de les différencier des autres pertes non parasitaires. Une analyse plus fine incluant l’effet région et l’impact sur le rendement devra être réalisée

Characterization of new Co and Ru on WC catalysts for Fischer-Tropsch reaction. Influence of the carbide surface state.

International audienceAn investigation of the performances in Fischer-Tropsch reaction of 1 wt% M/WC(X) (M = Co, Ru; X=A, B), where A is a tungsten carbide protected by free carbon and B is a clean tungsten carbide, was carried out. Supported catalysts performances were compared to those of the parent tungsten carbides at 473K and 20 bar. It was found that WC(A) produces mainly hydrocarbons but also 20–40% alcohols, whereas WC(B) activity is only towards linear alkanes. Before catalytic test, a reduction in pure hydrogen allows obtaining Co0 and Ru0 dispersed on layers of free carbon covering the WC core for the WC(A), and on a surface free of oxygen for WC(B). Co as Ru dispersions are improved on WC(B) compared to WC(A). A direct consequence is that Co/WC(B) has a better activity than Co/WC(A). Ru–W alloy formation could be responsible of the inobservance of a better activity for Ru/WC(B). On contrary, addition of Ru on WC(A) highly increases the activity and the production of heavy hydrocarbons. This beneficial effect, not observed with cobalt, could be attributed to a better dispersion of ruthenium on a carbon polymeric surface of WC

Study of cobalt and ruthenium supported on WC catalysts for FT reaction.

An investigation of bulk and cobalt or ruthenium supported tungsten carbide was carried out for their use in the Fischer-Tropsch reaction. Two types of WC were studied : tungsten carbide protected by free carbon and clean tungsten carbide, respectively noticed WC(A) and WC(B). XPS analysis shows that after air exposure, the WC(A) carbide surface is protected from the excess carbon whereas a surface W6+ phase is induced during the passivation step for WC(B). However WC(A) is inert towards aqueous impregnation, whereas WC(B) starts to corrode. A reduction in hydrogen at 673 K for Ru and 773K for Co supported catalysts allows obtaining Co0 and Ru0 dispersed on layers of free carbon covering the WC core for WC(A) and on a surface free of oxygen for WC(B). All the catalysts were active for the FT reaction. WC(A) produces mainly light alkanes (78%) and alcohols (22%), whereas no alcohol production is observed for WC(B). Co/WC(B) has a better activity than Co/WC(A), due to a better dispersion of cobalt on WC(B). The addition of Ru on WC(A) allow to obtain an high active catalyst with production of heavy hydrocarbons. On the contrary, formation of a Ru-W alloy could be consider to explain the low activity of Ru/WC(B) catalyst

New first trimester crown-rump length's equations optimized by structured data collection from a French general population

--- Objectives --- Prior to foetal karyotyping, the likelihood of Down's syndrome is often determined combining maternal age, serum free beta-HCG, PAPP-A levels and embryonic measurements of crown-rump length and nuchal translucency for gestational ages between 11 and 13 weeks. It appeared important to get a precise knowledge of these scan parameters' normal values during the first trimester. This paper focused on crown-rump length. --- METHODS --- 402 pregnancies from in-vitro fertilization allowing a precise estimation of foetal ages (FA) were used to determine the best model that describes crown-rump length (CRL) as a function of FA. Scan measures by a single operator from 3846 spontaneous pregnancies representative of the general population from Northern France were used to build a mathematical model linking FA and CRL in a context as close as possible to normal scan screening used in Down's syndrome likelihood determination. We modeled both CRL as a function of FA and FA as a function of CRL. For this, we used a clear methodology and performed regressions with heteroskedastic corrections and robust regressions. The results were compared by cross-validation to retain the equations with the best predictive power. We also studied the errors between observed and predicted values. --- Results --- Data from 513 spontaneous pregnancies allowed to model CRL as a function of age of foetal age. The best model was a polynomial of degree 2. Datation with our equation that models spontaneous pregnancies from a general population was in quite agreement with objective datations obtained from 402 IVF pregnancies and thus support the validity of our model. The most precise measure of CRL was when the SD was minimal (1.83mm), for a CRL of 23.6 mm where our model predicted a 49.4 days of foetal age. Our study allowed to model the SD from 30 to 90 days of foetal age and offers the opportunity of using Zscores in the future to detect growth abnormalities. --- Conclusion --- With powerful statistical tools we report a good modeling of the first trimester embryonic growth in the general population allowing a better knowledge of the date of fertilization useful in the ultrasound screening of Down's syndrome. The optimal period to measure CRL and predict foetal age was 49.4 days (9 weeks of gestational age). Our results open the way to the detection of foetal growth abnormalities using CRL Zscores throughout the first trimester