80 research outputs found
A New Method for Structural Simulation
In this paper structural change is defined and a tool to simulate structural changes is introduced which consists of a new simulation language which allows to deal separately with quantitative changes and structural qualitative changes. Two strategies of structural simulation are described. In the first one, the user defines the possible structures and conditions of change. In this case, the simulation process finds the structural paths through successive structures. In the second strategy, the structures are generated by the simulation process based on the model of creative thinking proposed by Poincare and Hadamard. AI and genetic programming techniques are used to implement the model. A simple example is given to illustrate the method of the second strategy
Transcriptional Regulation Is a Major Controller of Cell Cycle Transition Dynamics
DNA replication, mitosis and mitotic exit are critical transitions of the cell cycle which normally occur only once per cycle. A universal control mechanism was proposed for the regulation of mitotic entry in which Cdk helps its own activation through two positive feedback loops. Recent discoveries in various organisms showed the importance of positive feedbacks in other transitions as well. Here we investigate if a universal control system with transcriptional regulation(s) and post-translational positive feedback(s) can be proposed for the regulation of all cell cycle transitions. Through computational modeling, we analyze the transition dynamics in all possible combinations of transcriptional and post-translational regulations. We find that some combinations lead to âsloppyâ transitions, while others give very precise control. The periodic transcriptional regulation through the activator or the inhibitor leads to radically different dynamics. Experimental evidence shows that in cell cycle transitions of organisms investigated for cell cycle dependent periodic transcription, only the inhibitor OR the activator is under cyclic control and never both of them. Based on these observations, we propose two transcriptional control modes of cell cycle regulation that either STOP or let the cycle GO in case of a transcriptional failure. We discuss the biological relevance of such differences
A cluster randomized trial of a transition intervention for adolescents with congenital heart disease: rationale and design of the CHAPTER 2 study
Plastic input from the Seine River into the oceans: first results from the MacroPLAST project
International audienceMost recent studies state between 0.4 and 4 Million t/yr of plastic enter the ocean each year, most of it being transported by rivers. Those global estimations are associated with great uncertainties due to methodological difficulties to accurately quantify fluxes of macroplastic from continent into oceans. In addition, only few studies at the basin scale exist and no standard methods are applied to quantify those plastic fluxes. In this context, the Ministry of the Ecological and Solidarity Transition of France, in response to European directives, has initiated the MacroPLAST project to quantify macroplastic input from the Seine River into the oceans. But, most importantly, the aim of this study is to develop a methodology replicable in other rivers. Different methods are investigated including modeling, field methods, cameras, nets, etc. In this presentation, modeling and field methods using statistical data, floating booms or data from association collecting plastic litter are presented. The modeling method is based on Jambeck's approach applied to the Seine basin. Statistical and field approaches give similar order of magnitude, i.e. 1 800-6 300 t/yr entering the oceans from the Seine River (Figure 1). But, they are associated with large uncertainties and rough extrapolations. To avoid such extrapolations and statistical weaknesses, a new methodology has been developed and is actually in progress. It focuses on a probabilistic approach combining the tracking of floating debris using GPS, tagged plastic litter and data from plastic litter collection along the riverbanks of the Seine estuary operated since 2008. First results at the mid of June 2018 lead to fluxes ~800 t/yr of plastic, an order of magnitude lower than the two other approaches. The results will be progressively improved as long as new data will be available and by investigating the potential hiding plastic flux within the water column, below the surface
A multiplex culture system for the long-term growth of fission yeast cells: fission yeast long-term cultures
International audienceMaintenance of long-term cultures of yeast cells is central to a broad range of investigations, from metabolic studies to laboratory evolution assays. However, repeated dilutions of batch cultures lead to variations in medium composition, with implications for cell physiology. In Saccharomyces cerevisiae, powerful miniaturized chemostat setups, or ministat arrays, have been shown to allow for constant dilution of multiple independent cultures. Here we set out to adapt these arrays for continuous culture of a morphologically and physiologically distinct yeast, the fission yeast Schizosaccharomyces pombe, with the goal of maintaining constant population density over time. First, we demonstrated that the original ministats are incompatible with growing fission yeast for more than a few generations, prompting us to modify different aspects of the system design. Next, we identified critical parameters for sustaining unbiased vegetative growth in these conditions. This requires deletion of the gsf2 flocculin-encoding gene, along with addition of galactose to the medium and lowering of the culture temperature. Importantly, we improved the flexibility of the ministats by developing a piezo-pump module for the independent regulation of the dilution rate of each culture. This made it possible to easily grow strains that have different generation times in the same assay. Our system therefore allows for maintaining multiple fission yeast cultures in exponential growth, adapting the dilution of each culture over time to keep constant population density for hundreds of generations. These multiplex culture systems open the door to a new range of long-term experiments using this model organism. © 2017 The Authors. Yeast published by John Wiley & Sons, Ltd
Estimation des flux de plastiques transitant en Seine : quelles méthodes pour quels résultats ?
International audienceGlobal estimations state between 1 and 10 million metric tons of plastic entering the oceans each year. But, they are associated with great uncertainties due to methodological difficulties to accurately quantify plastic fluxes from continent into oceans. New studies at basin scale are thus needed to improve model calibrations. Here, a modelling approach based on JAMBECKâs statistical method and a field approach are compared in order to (i) quantify plastic fluxes in the Seine River and (ii) constrain uncertainties and their origins of the both approaches. Despite the simplicity of the statistical approach and rough extrapolations, both methods yield similar results, i.e. between 1,800 and 5,900 t/yr of plastic flowing into the Seine River. Whereas about 100 t/yr of plastic litter are removed by involved NGOs, which is a small fraction of the estimated flux. According to the MSFD (2008), actions are undertaken to quantify plastic fluxes entering the oceans. Among different methods, a better use of the data from the waste collection by NGOs should be considered. The development of a national and homogenous platform listing all the collects could be a first step in that direction.Des estimations globales Ă©tablissent des flux de plastiques entrant en mer entre 1 et 10 millions de tonnes chaque annĂ©e. Mais elles sont associĂ©es Ă de grandes incertitudes liĂ©es Ă des difficultĂ©s mĂ©thodologiques pour quantifier les flux de plastiques du continent vers les ocĂ©ans. Travailler Ă lâĂ©chelle des bassins versants sâavĂšre nĂ©cessaire afin de mieux calibrer ces approches globales. Dans cette Ă©tude, une approche de modĂ©lisation conceptuelle, basĂ©e sur lâapproche statistique de JAMBECK et al., et une approche de terrain sont comparĂ©es avec pour objectif (i) de quantifier les flux de plastiques transitant en Seine et (ii) de prĂ©ciser les incertitudes des deux approches et leur origine. MalgrĂ© la simplicitĂ© des approches statistiques et des techniques dâextrapolation utilisĂ©es, les deux mĂ©thodes donnent des rĂ©sultats du mĂȘme ordre de grandeur, câest-Ă -dire entre 1800 et 5900 t/an de plastiques transitant en Seine. Les principaux acteurs de la gestion des dĂ©chets sauvages sur le fleuve ne collectent quâenviron 100 t/an de plastiques, soit une faible fraction du flux estimĂ©. Dans le cadre de la directive cadre stratĂ©gie pour le milieu marin (DCSMM) de 2008, des actions sont mises en oeuvre afin de quantifier les flux de plastique dĂ©versĂ©s en mer. Parmi les diffĂ©rentes mĂ©thodes, une meilleure exploitation des donnĂ©es issues des collectes des associations pourrait ĂȘtre une aubaine avec, par exemple, la crĂ©ation dâune base de donnĂ©es nationale et homogĂšne rĂ©pertoriant les opĂ©rations de collecte
PremiÚres tentatives de quantification des flux de macro déchets plastiques en Seine
International audienceMacroplastiques, bassin de la Seine, barrages flottants, taux de fuite CHAPĂ Le projet MacroPLAST, soutenu et financĂ© par le ministĂšre de la transition Ă©cologique et solidaire, est issu de la mise en oeuvre de la Directive Cadre de Surveillance du Milieu Marin, qui initie diverses actions relatives aux macrodĂ©chets marins afin de rĂ©duire Ă la source leurs quantitĂ©s en mer et sur le littoral. CONTEXTE Pas un jour ne passe sans la diffusion d'images chocs de la pollution marine Ă travers le monde par le plastique. Bien que le plus grand nombre de fragments soient des microplastiques ( 5 mm). Les stocks Ă la surface des ocĂ©ans sont estimĂ©s Ă 300 000 tonnes alors que des modĂšles statistiques Ă l'Ă©chelle mondiale prĂ©disent des flux entrant de l'ordre de 1-10 millions de tonnes/an (Eriksen et al., 2014; Jambeck et al., 2015). Les fonds ocĂ©aniques pourraient quant Ă eux constituer la destination finale des plastiques (Galgani et al., 2000). Alors que les dĂ©chets plastiques ne reprĂ©sentent que 10% de l'ensemble des dĂ©chets gĂ©nĂ©rĂ©s par les activitĂ©s humaines, leur durĂ©e de vie (siĂšcles Ă millĂ©naires) en fait les dĂ©chets les plus reprĂ©sentĂ©s dans des zones trĂšs Ă©loignĂ©es de leur origine, i.e. les grandes agglomĂ©rations urbaines (Barnes et al., 2009). Ce n'est que trĂšs rĂ©cemment que la communautĂ© scientifique a pris conscience que 1) les fleuves et riviĂšres sont des vecteurs majeurs de la pollution plastique des continents vers les ocĂ©ans (le chiffre de 80 % des dĂ©chets provenant des continents est souvent citĂ©), et 2) les macroplastiques sont des gisements de microplastiques secondaires dont le rĂ©el impact Ă©cologique est Ă peine connu aujourd'hui. Encore plus que pour les microplastiques, les connaissances concernant les flux de macroplastiques dans les eaux de riviĂšre ainsi que leur dynamique de transfĂšre et leurs sources sont trĂšs lacunaires. Pourtant, elles sont essentielles pour calibrer les modĂšles statistiques de flux de plastiques en mer Ă l'Ă©chelle mondiale. Dans ce contexte, le projet MacroPLAST, financĂ© par le MinistĂšre de la Transition Ăcologique et Solidaire, a pour objectif d'Ă©valuer les flux de macrodĂ©chets dĂ©versĂ©s en mer Ă l'Ă©chelle du bassin de la Seine. Bien que l'ensemble des dĂ©chets soit considĂ©rĂ© (dĂ©bris plastiques, mĂ©talliques, bois manufacturĂ©s, verre), l'Ă©tude s'oriente principalement sur les macroplastiques. Cette synthĂšse prĂ©sente les rĂ©sultats obtenus ou en cours d'obtention dans le cadre des programmes de recherche PIREN-Seine, OPUR et MacroPLAST. Ils proviennent en partie de la thĂšse de Rachid Dris (Dris, 2016) complĂ©tĂ©s des donnĂ©es rĂ©centes de l'ORDIF (Observatoire RĂ©gional des DĂ©chets d'Ăle de France) et du site sinoe.org (ADEME). VERS LES PREMIERES ESTIMATIONS DE FLUX DE MACROPLASTIQUES EN SEINE L'estimation des flux de dĂ©chets peut ĂȘtre abordĂ©e selon deux approches : une approche de modĂ©lisation conceptuelle (AMC) et une approche expĂ©rimentale (AE). La premiĂšre considĂšre un taux de fuite de dĂ©chets plastiques dans l'environnement constituant une quantitĂ© de dĂ©chets mal gĂ©rĂ©s dĂ©pendante de la pression anthropique (Jambeck et al., 2015). Elle a l'avantage d'ĂȘtre globale et d'intĂ©grer toutes les tailles de plastique
Neurodevelopmental evaluation for school-age children with congenital heart disease: recommendations from the cardiac neurodevelopmental outcome collaborative.
Solid state coordination chemistry of the copper(ii)-terpyridine/oxovanadium organophosphonate system: hydrothermal syntheses, structural characterization and magnetic properties
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