Three-dimensional lattice gas with minimal interactions

Proceedings of the Conference ``Euromech 287: Discrete Models in Fluid-Dynamics'', 1992, Ed. P. NelsonInternational audienceAn interaction has been added to the classical lattice gas model that exchanges momentum between sites. The hydrodynamic limit of the model can be obtained from a Chapman-Enskog expansion and all the coefficients can be expressed explicitly. The interaction contributions to viscous terms are independent of the initial interaction-free model and grow like r2. When the interaction range r is large enough, the pressure acquires a negative slope for certain densities. The model then has a phase transition, observed in simulations. Some examples of a three-dimensional phase separation are shown. Whatever the dimension of space, the model can be represented by a cellular automaton with only nearest neighbor communications, using messenger particles or photons. In 2 dimensions of space, this allows fitting the model into a 16 bit table adequate for a special purpose cellular automaton machine like the RAP1

Contribution of multispectral autofluorescence imaging to histochemistry in understanding sorghum internode hydrolysis pattern

International audienceSorghum is the world’s fifth largest cereal crop and exhibits high biomass yield potentials. This cereal is suitable to support the development of biomass value chains in temperate and semi-arid environments. Digestibility of plant feedstock is one of the key properties and is largely dependent on the overall lignification of the plant which is monitored at the tissue scale by the relative amounts and composition of plant organ. To obtain details on organ anatomy and spatial distribution of main components, medium-throughput histochemical methods have been developed on maize and sorghum internodes [1,2]. FASGA staining procedure is based onthe competition between 2 dyes and reveals regions with different staining colour (essentially red and blue color) which may be interpreted in terms of tissue ligninification [3]. In addition to staining procedures, the specific spectral properties of phenolic compounds could also be exploited to map their distributions using spectral imaging technics. Multispectral autofluorescence imaging was successfully applied to maize stem internode to reveal differences in cell wall phenolic compounds distribution (lignin and hydroxycinnamic acids) [4]. The objective of this work was to evaluate the relevance of multispectral autofluorescence imaging to better understand contrasted hydrolysis patterns observed inside the sorghum stem internode. Two sorghum genotypes differing in their hydrolysis yield were selected. Internodes (at the bottom of the stem) from four healthy plants harvested at the grain filling stage were characterized for histochemistry in relation to spatial-susceptibility to enzymatic hydrolysis. Cell wall digestion was realized with a combined cellulase/hemicellulase 4% mix during 72h. The hydrolyzed sections were stained with FASGA and the hydrolysis yields were estimated by comparing the area of the section before and after hydrolysis (Figure 1A,B).. Images were analyzed with the open-source ImageJ freeware4 and a dedicated script to quantify anatomical traits. Multispectral autofluorescence images (Figure 1C) were acquired using a multi-zoom macroscope AZ100M (Nikon, Japan) equipped with 4 filter blocks to acquire images under UV, blue and green excitation lights. Emission light was recovered through long pass filters and, taking advantage of the RGB channels of the color camera, each image was split in three channels and stack alltogether to obtain a 12 channels multispectral image. In such multispectral images, each pixel is characterized by an intensity profile that can be considered as a spectral signature (Figure 1D).Observed after FASGA staining, both genotypes showed typical sorghum internode organization with two main anatomical zones: (1) a mainly red-stained peripheral zone Z1 (rind), which is rich in vascular bundles and sclerenchyma cells and is surrounded by an epidermis on the most external part, and (2) an inner zone Z2 (pith), composed of vascular bundles spread into blue-stained parenchyma. As already observed, no hydrolysis of the red-stained zone (Z1) was evidenced for these two genotypes. Different hydrolysis pattern in the low-lignified zone (Z2) was revealed. One genotype showed a limited losse of material (below 10% for two plants and up to 25 % for the other two plants). For the second genotype hydrolysis yields were about 40-50%, corresponding to an almost complete degradataion of the Z2 region. For both genotypes, the hydrolysis was more pronounced in the middle of the internode cross section. Comparison of the brightfield images with the color representation of the average multispectral images shows that all the cell wall showed autofluorescence under UV or visible excitation. Differences in color in this multispectral image highlight the main tissues with highly lignified tissue appearing as pink/orange. No visual difference between parenchyma was evidenced and more precise analysis of spectral signature was carried out. Spectral signature of blue-stained parenchyma cell walls were extracted in both hydrolysed and not hydrolysed regions. Whole spectral signatures were compared through principal component analysis. Slight differences were observed, in particular under UV-excitation light and must be faced to overall spectral variability (within a cross section and between plants). The relevance of combined classical histochemical and multispectral imaging was emphasized in this study allowing to highlight the different behaviours of constratsing genotypes and different regions of the internodes

L’innovation technologique face au changement climatique : quelle est la position de la France ?

Technological Innovation and Climate Change : Where Does France Stand ? We analyse France’s position on global warming mitigation technology. The methodology draws on a database describing all patents filed between 1980 and 2008 in 17 climate-related technological classes. France is the fifth largest innovator in theworld, with 5.2% of patented inventions, including 20% from the public sector. More than half of French inventions are protected abroad, 1.5 times more than the global average. France’s position is relativelyweak in renewable energy, and strong in sectorsmarked by the presence of national industrial champions and public research organisations.Cet article propose une analyse du positionnement de la France en matière de technologies de lutte contre le réchauffement climatique. La méthodologie s’appuie sur une base de données décrivant l’ensemble des dépôts de brevets entre 1980 et 2008 dans 17 classes technologiques liées au climat. La France est au cinquième rang mondial, avec 5,2% des inventions brevetées dont 20 % proviennent du secteur public. Plus de la moitié des inventions françaises sont protégées à l’étranger, soit 1,5 fois plus que la moyenne mondiale. Le positionnement technologique de la France est faible dans les énergies renouvelables et fort dans des secteurs marqués par la présence de champions nationaux industriels et des organismes publics de recherche.Ménière Yann, Glachant Matthieu, Dechezleprêtre Antoine, Pot Cécile, Carrère Fabrice, Le Blanc Gilles. L’innovation technologique face au changement climatique : quelle est la position de la France ?. In: Économie & prévision, n°202-203, 2013. Economie du droit. pp. 53-80

Plasticity of sorghum stem biomass accumulation in response to water deficit: A multiscale analysis from internode tissue to plant level

Sorghum is increasingly used as a biomass crop worldwide. Its genetic diversity provides a large range of stem biochemical composition suitable for various end-uses as bioenergy or forage. Its drought tolerance enables it to reasonably sustain biomass production under water limited conditions. However, drought effect on the accumulation of sorghum stem biomass remains poorly understood which limits progress in crop improvement and management. This study aimed at identifying the morphological, biochemical and histological traits underlying biomass accumulation in the sorghum stem and its plasticity in response to water deficit. Two hybrids (G1, G4) different in stem biochemical composition (G4, more lignified, less sweet) were evaluated during 2 years in the field in Southern France, under two water treatments differentiated during stem elongation (irrigated; 1 month dry-down until an average soil water deficit of -8.85 bars). Plant phenology was observed weekly. At the end of the water treatment and at final harvest, plant height, stem and leaf dry-weight and the size, biochemical composition and tissue histology of internodes at 2-4 positions along the stem were measured. Stem biomass accumulation was significantly reduced by drought (in average 42% at the end of the dry-down). This was due to the reduction of the length, but not diameter, of the internodes expanded during water deficit. These internodes had more soluble sugar but lower lignin and cellulose contents. This was associated with a decrease of the areal proportion of lignified cell wall in internode outer zone whereas the areal proportion of this zone was not affected. All internodes for a given genotype and environment followed a common histochemical dynamics. Hemicellulose content and the areal proportion of inner vs. outer internode tissues were set up early during internode growth and were not drought responsive. G4 exhibited a higher drought sensitivity than G1 for plant height only. At final harvest, the stem dry weight was only 18% lower in water deficit (re-watered) compared to well-watered treatment and internodes growing during re-watering were similar to those on the well-watered plants. These results are being valorized to refine the phenotyping of sorghum diversity panels and breeding populations

Large-Scale Modeling Approach Reveals Functional Metabolic Shifts during Hepatic Differentiation

International audienceBeing able to explore the metabolism of broad metabolizing cells is of critical importance in many research fields. This article presents an original modeling solution combining metabolic network and omics data to identify modulated metabolic pathways and changes in metabolic functions occurring during differentiation of a human hepatic cell line (HepaRG). Our results confirm the activation of hepato-specific functionalities and newly evidence modulation of other metabolic pathways, which could not be evidenced from transcriptomic data alone. Our method takes advantage of the network structure to detect changes in metabolic pathways that do not have gene annotations and exploits flux analyses techniques to identify activated metabolic functions. Compared to the usual cell-specific metabolic network reconstruction approaches, it limits false predictions by considering several possible network configurations to represent one phenotype rather than one arbitrarily selected network. Our approach significantly enhances the comprehensive and functional assessment of cell metabolism, opening further perspectives to investigate metabolic shifts occurring within various biological contexts

Integrated Modelling of pesticide fate in agricultural landscapes

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Modélisation Intégrée du devenir des Pesticides dans les Paysages agricoles (projet MIPP)

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Modélisation intégrée du devenir des pesticides dans les paysages agricoles

L'utilisation des pesticides en agriculture entraîne une contamination de la plupart des compartiments des écosystèmes (sol, eau, air) comme en témoignent les différents monitoring mis en place. Pour estimer le risque de contamination de ces compartiments et identifier les moyens de limiter cette contamination, il est nécessaire de développer une approche de modélisation qui décrive complètement les dynamiques et les voies de transfert des pesticides depuis l'échelle de la parcelle jusqu'à l'échelle du paysage, intégrant l'ensemble des compartiments. Jusque-là, le plus souvent, les approches de modélisation sont partielles car se focalisant chacune sur des dynamiques et compartiments spécifiques comme la dispersion atmosphérique d'une part, le transport par ruissellement de surface d'autre part ou encore la percolation vers les nappes souterraines. Cette communication présente un projet collaboratif pour la modélisation du devenir des pesticides qui rassemble six unités de recherche, soit une vingtaine de chercheurs et ingénieurs, pour développer un modèle intégré du devenir des pesticides à l'échelle du paysage. Ce modèle intégré permettra de prédire les concentrations en pesticides dans le sol, l'eau et l'air ainsi que les échanges dans et entre les différents compartiments sous l'influence conjointe de l'organisation spatio-temporelle des paysages et des pratiques agricoles à l'échelle d'un bassin versant. Le principe fondamental de cette démarche collaborative n'est pas de développer un nouveau modèle mais de réutiliser les approches de modélisation déjà développées dans chaque groupe de recherche et de les coupler via des plateformes de modélisation et simulation conçues pour faciliter la modélisation des agroenvironnements (plateformes OpenFLUID, SolVirtuel et RECORD). Cette communication présente alors les principes de la modélisation intégrée des pesticides à l'échelle du paysage qui est actuellement en cours de développement, et plus particulièrement les choix retenus pour i) la représentation spatiale des paysages agricoles (objets spatiaux, propriétés et connectivité spatiale), ii) les principaux processus considérés (distribution entre sol, culture et atmosphère ; transferts dans le sol et à la surface ; équilibres physico-chimiques ; émission vers l'atmosphère par volatilisation et dérive ; dispersion atmosphérique de la fraction volatile ; déposition gazeuse ; …) et iii) leur couplage spatio-temporel. Un des enjeux clés est de réussir le couplage à l'échelle du paysage de la modélisation de la dispersion atmosphérique avec la modélisation mise en oeuvre pour la modélisation des processus hydrologiques, et de représenter les échanges à l'interface surface/atmosphère à cette échelle. Les premiers résultats obtenus sur un bassin-versant viticole seront présentés

Modélisation intégrée du devenir des pesticides dans le paysage

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Modélisation intégrée du devenir des pesticides dans le paysage

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