90 research outputs found
Investigating the association between strategic and pathological gambling behaviors and substance use in youth: Could religious faith play a differential role?
Objectives: This study investigated the link between gambling behaviors and the use of alcohol, drugs, and nonprescribed prescription medications, while exploring the moderating role of distinct religious faiths. Methods:: In 2010, 570 students from the American University of Beirut completed a self-reported, anonymous English questionnaire, which included lifetime gambling and past-year substance use measures. Results: Half (55%) were lifetime gamblers, of whom, 12% were probable pathological gamblers. About 60% were strategic gamblers. Lifetime gamblers were more than twice as likely as nongamblers to report past-year illegal drug use and alcohol abuse. Probable pathological gamblers were also more than four times as likely as nongamblers to report nonmedical prescription drug use, illegal drug use, and alcohol abuse. Compared to nonstrategic gamblers, strategic gamblers had more than three times the odds of illegal drug and cigarette use. The link between alcohol abuse and gambling was stronger among Christians than Muslims. Conversely, Muslims were more likely to report the co-occurrence of various gambling behaviors (lifetime, probable pathological, and strategic gambling) with both illegal drug use and cigarette use. Conclusions: Gambling and substance use behaviors were strongly linked in this sample of youth from Lebanon, corroborating the evidence from North America. Particularly novel are the co-occurrence of pathological gambling and nonmedical prescription drug use and the potential differential role of religion
Supercritical carbon dioxide extraction and fractionation of lipids from freeze-dried microalgae Nannochloropsis oculata and Chlorella vulgaris
This study deals with the selective extraction of neutral lipids from microalgae. We investigated the consequences of bypassing cell-wall disintegration before supercritical carbon dioxide extraction. Different operating parameters (use of co-solvent, pressure, and time) were tested on freeze-dried Chlorella vulgaris and Nannochloropsis oculata. The solid phase extraction technique (SPE) was used throughout the extraction process to assess variations in the yield of liberated neutral lipids, glycolipids, and phospholipids. Under operating conditions, 97% of neutral lipids were extracted from C. vulgaris using ethanol (10% v/v) as co-solvent. Neutral lipids from N. oculata represented most of the extracts (83%), whereas the proportion of glycolipids and phospholipids did not exceed 12.1% and 5.3%, respectively. Microscopic observation showed that cell wall integrity was maintained during the extraction process
Coupling a simple irradiance description to a mechanistic growth model to predict algal production in industrial-scale solar-powered photobioreactors
Continuous cultivation of photosynthetic microorganisms: approaches, applications and future trends
The possibility of using photosynthetic microorganisms, such as cyanobacteria and microalgae, for converting light and carbon dioxide into valuable biochemical products has raised the need for new cost-efficient processes ensuring a constant product quality. Food, feed, biofuels, cosmetics and pharmaceutics are among the sectors that can profit from the application of photosynthetic microorganisms.
Biomass growth in a photobioreactor is a complex process influenced by multiple parameters, such as photosynthetic light capture and attenuation, nutrient uptake, photobioreactor hydrodynamics and gas-liquid mass transfer.
In order to optimize productivity while keeping a standard product quality, a permanent control of the main cultivation parameters is necessary, where the continuous cultivation has shown to be the best option. However it is of utmost importance to recognize the singularity of continuous cultivation of cyanobacteria and microalgae due to their dependence on light availability and intensity.
In this sense, this review provides comprehensive information on recent breakthroughs and possible future trends regarding technological and process improvements in continuous cultivation systems of microalgae and cyanobacteria, that will directly affect cost-effectiveness and product quality standardization. An overview of the various applications, techniques and equipment (with special emphasis on photobioreactors) in continuous cultivation of microalgae and cyanobacteria are presented. Additionally, mathematical modelling, feasibility, economics as well as the applicability of continuous cultivation into large-scale operation, are discussed.This research work was supported by the grant SFRH/BPD/98694/2013 (Bruno Fernandes) from Fundacao para a Ciencia e a Tecnologia (Portugal). The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013. The authors also thank the Project "BioInd Biotechnology and Bioengineering for improved Industrial and Agro-Food processes, REF. NORTE-07-0124-FEDER-000028" Co-funded by the Programa Operacional Regional do Norte (ON.2-O Novo Norte), QREN, FEDE
Simulating cyanobacterial phenotypes by integrating flux balance analysis, kinetics, and a light distribution function
Metabolic modeling of Chlamydomonas reinhardtii: energy requirements for photoautotrophic growth and maintenance
Vers le Transport Multi-Echelles de Panaches Fins
The distribution of aerosols and trace gases in the atmosphere resultsfrom the emission of primary gaseous and particulate matter, as well astheir transport, sedimentation and (photo-)chemical transformations.Understanding and quantifying these processes in the atmosphere can beaddressed through the use of global-scale or regional-scalechemistry-transport numerical models.CHIMERE is a chemistry-transport model developed mainly at LMD (Mailleret al., 2017). Initially targeted to urban and regional scales, it wasrecently extended to hemispheric scales in order to address theseprocesses on a wider range. While theoretically possible, it isimpractical to use this model to represent interactions betweensmall-scale processes (e.g. pollution in the urban atmospheric boundarylayer) and large-scale processes (e.g. intercontinental transport)controlling dense plumes of gas and aerosols, resulting for instancefrom massive emissions by volcanic eruptions, forest fires and desertaerosol tempests. Indeed such studies requiring both large domains andhigh resolution have a prohibitive numerical cost due to the formulationof CHIMERE on a regular Cartesian mesh. This limitation is shared by allcurrently operational chemistry-transport models. Additionally,traditional Cartesian longitude-latitude meshes pose a numericalsingularity at the poles, where the longitude lines converge.One way to lift these limitations would be to replace CHIMEREâsCartesian mesh by a fully unstructured mesh. Unstructured meshes supportvariable resolution in space, allowing computational resources to befocused in those few key regions (e.g. volcanic eruption) where highspatial resolution is really required. Allowing such multi-scalecapacity would be a significant step forward in the modelling of scaleinteractions in atmospheric chemistry, and would potentially allowbreakthrough for the understanding of such interactions.DYNAMICO, the atmospheric general circulation model recently developedat LMD and LSCE (Dubos et al., 2015) supports unstructured sphericalVoronoi meshes. It is the goal of this PhD project to contribute to theassessment of the viability of numerical methods borrowed from DYNAMICO forlarge-scale transport of sharp plumes. To this end, we compare thenumerical performance of transport schemes formulated on sphericalunstructured meshes (Dubey et al., 2015) with schemes formulated onCartesian spherical meshes avoiding the poles. Schemes of various orderand different treatments of time integration are implemented in eachmesh framework. A suite of test cases is used to evaluate differentproperties of the mesh-scheme pairings. Various metrics are used tostudy stability, monotonicity, convergence and numerical diffusion.While it could be anticipated that Cartesian schemes perform better thantheir unstructured counterpart of similar complexity, we find that ascheme of the Van Leer family on the unstructured mesh has a comparableperformance to a similar scheme on a Cartesian mesh, which is the defaultscheme used operationally by CHIMERE. Beyond these idealizedtwo-dimensional numerical experiments, we compare the performance of thetwo schemes in a realistic, three-dimensional setting mimicking theeruption of the Puyehue volcano in 2011. This necessary milestone is tobe complemented by experiments with variable-resolution meshes leadingto a full assessment of the merits of multi-scale-modellingchemistry-transport applications.La distribution dâaĂ©rosols et de gaz trace dans lâatmosphĂšre rĂ©sulte delâĂ©mission dâespĂšces gazeuses et particulaires primaires, ainsi que deleur transport, de leur sĂ©dimentation et de leurs transformations(photo)chimiques. La modĂ©lisation de ces processus dans lâatmosphĂšrepeut sâaborder au travers de modĂšles de chimie-transport dâĂ©chelleglobale ou rĂ©gionale.Le modĂšle CHIMERE, dĂ©veloppĂ© en grande partie au LMD (Mailler et al.,2017), est un modĂšle de chimie-transport rĂ©gional, rĂ©cemment Ă©tendu auxĂ©chelles hĂ©misphĂ©riques, qui permet dâaborder ces phĂ©nomĂšnes sur unegrande gamme dâĂ©chelles, allant de lâĂ©chelle dâune ville Ă celle dâunhĂ©misphĂšre. Il est toutefois difficile dâutiliser ce modĂšle pourreprĂ©senter les interactions entre phĂ©nomĂšnes de petite Ă©chelle(pollution de la couche limite urbaine) et de grande Ă©chelle (transportĂ lâĂ©chelle continentale ou hĂ©misphĂ©rique) de panaches denses de gaz etdâaĂ©rosols, issus par exemple dâĂ©missions de panaches volcaniques, defeux de forĂȘt, ou dâaĂ©rosols dĂ©sertiques. Cette limitation est un effetde lâimpossibilitĂ© dâutiliser le modĂšle sous sa forme actuelle avec undomaine Ă maille non structurĂ©e, seul type de maillage permettant unerĂ©elle variation de la rĂ©solution en fonction de zones dâintĂ©rĂȘtdĂ©finies par le modĂ©lisateur (zones urbaines, zones dâĂ©mission). Cettelimitation est commune Ă la totalitĂ© des modĂšles de chimie-transportexistants Ă lâheure actuelle, pouvoir la lever serait donc un importantpas en avant pour la comprĂ©hension des interactions dâĂ©chelle dans ledomaine de la chimie atmosphĂ©rique.Une façon de lever ces limitations serait de remplacer le maillagecartĂ©sien de CHIMERE par un maillage non-structurĂ©. En effet lesmaillages non-structurĂ©s permettent de faire varier la rĂ©solution dansl'espace et de concentrer les ressources de calcul dans les quelquesrĂ©gions clĂ©s (p.ex. prĂšs d'une Ă©ruption volcanique) oĂč une hauterĂ©solution spatiale est rĂ©ellement nĂ©cessaire. Introduire une telleflexibilitĂ© multi-Ă©chelle reprĂ©senterait un pas important pour lamodĂ©lisation des interactions d'Ă©chelles en chimie atmosphĂ©rique, etpermettrait potentiellement des percĂ©es dans la comprĂ©hension de cesinteractions.DYNAMICO, le modĂšle de circulation gĂ©nĂ©rale atmosphĂ©rique dĂ©veloppĂ©rĂ©cemment au LMD et au LSCE (Dubos et al., 2015) est basĂ© sur desmaillages de Voronoi non-structurĂ©s sphĂ©riques. L'objectif de cettethĂšse est de contribuer Ă l'Ă©valuation de mĂ©thods numĂ©riques empruntĂ©esĂ DYNAMICO pour le transport Ă grand Ă©chelle de panaches fins. A cettefin nous comparons la performance numĂ©rique de schĂ©mas de transportformulĂ©s sur maillage non-structurĂ© (Dubey et al., 2015) Ă celle deschĂ©mas similaires formulĂ©s sur un maillage cartĂ©sien sphĂ©rique Ă©vitantles pĂŽles. Des schĂ©mas d'ordre variĂ© et avec diffĂ©rents traitements del'intĂ©gration temporelle sont implĂ©mentĂ©s pour chacun des deux types demaillage. Un jeu de cas-test est utilisĂ© pour Ă©valuĂ© diffĂ©rentespropriĂ©tĂ©s des paires maillage-schĂ©ma. DiffĂ©rentes mĂ©triques permettentd'Ă©tudier les propriĂ©tes de stabilitĂ©, monotonocitĂ©, convergence etdiffusion numĂ©rique. Alors que l'on pouvait s'attendre Ă une meilleureperformance des schĂ©mas cartĂ©siens par rapport Ă aux schĂ©masnon-structurĂ©s de complexitĂ© similaire, nous trouvons qu'un schĂ©ma de lafamille des schĂ©mas de Van Leer a une performance comparable Ă un schĂ©masimilaire sur maillage cartĂ©sien, schĂ©ma qui est proposĂ© par dĂ©faut parle modĂšle CHIMERE de façon opĂ©rationnelle. Au-delĂ de ces expĂ©riencesnumĂ©riques bidimensionnelles idĂ©alisĂ©es, nous comparons la performancede ces deux schĂ©mas dans un contexte tridimensionnel rĂ©aliste inspirĂ© del'Ă©ruption du volcan Puyehue en 2011. Ce nĂ©cessaire jalon doit ĂȘtrecomplĂ©tĂ© par des expĂ©rience Ă rĂ©solution variable pour mener Ă uneĂ©valuation complĂšte des mĂ©rites de la modĂ©lisation multi-Ă©chelles pourles applications en chimie-transport
Vers le Transport Multi-Echelles de Panaches Fins
The distribution of aerosols and trace gases in the atmosphere resultsfrom the emission of primary gaseous and particulate matter, as well astheir transport, sedimentation and (photo-)chemical transformations.Understanding and quantifying these processes in the atmosphere can beaddressed through the use of global-scale or regional-scalechemistry-transport numerical models.CHIMERE is a chemistry-transport model developed mainly at LMD (Mailleret al., 2017). Initially targeted to urban and regional scales, it wasrecently extended to hemispheric scales in order to address theseprocesses on a wider range. While theoretically possible, it isimpractical to use this model to represent interactions betweensmall-scale processes (e.g. pollution in the urban atmospheric boundarylayer) and large-scale processes (e.g. intercontinental transport)controlling dense plumes of gas and aerosols, resulting for instancefrom massive emissions by volcanic eruptions, forest fires and desertaerosol tempests. Indeed such studies requiring both large domains andhigh resolution have a prohibitive numerical cost due to the formulationof CHIMERE on a regular Cartesian mesh. This limitation is shared by allcurrently operational chemistry-transport models. Additionally,traditional Cartesian longitude-latitude meshes pose a numericalsingularity at the poles, where the longitude lines converge.One way to lift these limitations would be to replace CHIMEREâsCartesian mesh by a fully unstructured mesh. Unstructured meshes supportvariable resolution in space, allowing computational resources to befocused in those few key regions (e.g. volcanic eruption) where highspatial resolution is really required. Allowing such multi-scalecapacity would be a significant step forward in the modelling of scaleinteractions in atmospheric chemistry, and would potentially allowbreakthrough for the understanding of such interactions.DYNAMICO, the atmospheric general circulation model recently developedat LMD and LSCE (Dubos et al., 2015) supports unstructured sphericalVoronoi meshes. It is the goal of this PhD project to contribute to theassessment of the viability of numerical methods borrowed from DYNAMICO forlarge-scale transport of sharp plumes. To this end, we compare thenumerical performance of transport schemes formulated on sphericalunstructured meshes (Dubey et al., 2015) with schemes formulated onCartesian spherical meshes avoiding the poles. Schemes of various orderand different treatments of time integration are implemented in eachmesh framework. A suite of test cases is used to evaluate differentproperties of the mesh-scheme pairings. Various metrics are used tostudy stability, monotonicity, convergence and numerical diffusion.While it could be anticipated that Cartesian schemes perform better thantheir unstructured counterpart of similar complexity, we find that ascheme of the Van Leer family on the unstructured mesh has a comparableperformance to a similar scheme on a Cartesian mesh, which is the defaultscheme used operationally by CHIMERE. Beyond these idealizedtwo-dimensional numerical experiments, we compare the performance of thetwo schemes in a realistic, three-dimensional setting mimicking theeruption of the Puyehue volcano in 2011. This necessary milestone is tobe complemented by experiments with variable-resolution meshes leadingto a full assessment of the merits of multi-scale-modellingchemistry-transport applications.La distribution dâaĂ©rosols et de gaz trace dans lâatmosphĂšre rĂ©sulte delâĂ©mission dâespĂšces gazeuses et particulaires primaires, ainsi que deleur transport, de leur sĂ©dimentation et de leurs transformations(photo)chimiques. La modĂ©lisation de ces processus dans lâatmosphĂšrepeut sâaborder au travers de modĂšles de chimie-transport dâĂ©chelleglobale ou rĂ©gionale.Le modĂšle CHIMERE, dĂ©veloppĂ© en grande partie au LMD (Mailler et al.,2017), est un modĂšle de chimie-transport rĂ©gional, rĂ©cemment Ă©tendu auxĂ©chelles hĂ©misphĂ©riques, qui permet dâaborder ces phĂ©nomĂšnes sur unegrande gamme dâĂ©chelles, allant de lâĂ©chelle dâune ville Ă celle dâunhĂ©misphĂšre. Il est toutefois difficile dâutiliser ce modĂšle pourreprĂ©senter les interactions entre phĂ©nomĂšnes de petite Ă©chelle(pollution de la couche limite urbaine) et de grande Ă©chelle (transportĂ lâĂ©chelle continentale ou hĂ©misphĂ©rique) de panaches denses de gaz etdâaĂ©rosols, issus par exemple dâĂ©missions de panaches volcaniques, defeux de forĂȘt, ou dâaĂ©rosols dĂ©sertiques. Cette limitation est un effetde lâimpossibilitĂ© dâutiliser le modĂšle sous sa forme actuelle avec undomaine Ă maille non structurĂ©e, seul type de maillage permettant unerĂ©elle variation de la rĂ©solution en fonction de zones dâintĂ©rĂȘtdĂ©finies par le modĂ©lisateur (zones urbaines, zones dâĂ©mission). Cettelimitation est commune Ă la totalitĂ© des modĂšles de chimie-transportexistants Ă lâheure actuelle, pouvoir la lever serait donc un importantpas en avant pour la comprĂ©hension des interactions dâĂ©chelle dans ledomaine de la chimie atmosphĂ©rique.Une façon de lever ces limitations serait de remplacer le maillagecartĂ©sien de CHIMERE par un maillage non-structurĂ©. En effet lesmaillages non-structurĂ©s permettent de faire varier la rĂ©solution dansl'espace et de concentrer les ressources de calcul dans les quelquesrĂ©gions clĂ©s (p.ex. prĂšs d'une Ă©ruption volcanique) oĂč une hauterĂ©solution spatiale est rĂ©ellement nĂ©cessaire. Introduire une telleflexibilitĂ© multi-Ă©chelle reprĂ©senterait un pas important pour lamodĂ©lisation des interactions d'Ă©chelles en chimie atmosphĂ©rique, etpermettrait potentiellement des percĂ©es dans la comprĂ©hension de cesinteractions.DYNAMICO, le modĂšle de circulation gĂ©nĂ©rale atmosphĂ©rique dĂ©veloppĂ©rĂ©cemment au LMD et au LSCE (Dubos et al., 2015) est basĂ© sur desmaillages de Voronoi non-structurĂ©s sphĂ©riques. L'objectif de cettethĂšse est de contribuer Ă l'Ă©valuation de mĂ©thods numĂ©riques empruntĂ©esĂ DYNAMICO pour le transport Ă grand Ă©chelle de panaches fins. A cettefin nous comparons la performance numĂ©rique de schĂ©mas de transportformulĂ©s sur maillage non-structurĂ© (Dubey et al., 2015) Ă celle deschĂ©mas similaires formulĂ©s sur un maillage cartĂ©sien sphĂ©rique Ă©vitantles pĂŽles. Des schĂ©mas d'ordre variĂ© et avec diffĂ©rents traitements del'intĂ©gration temporelle sont implĂ©mentĂ©s pour chacun des deux types demaillage. Un jeu de cas-test est utilisĂ© pour Ă©valuĂ© diffĂ©rentespropriĂ©tĂ©s des paires maillage-schĂ©ma. DiffĂ©rentes mĂ©triques permettentd'Ă©tudier les propriĂ©tes de stabilitĂ©, monotonocitĂ©, convergence etdiffusion numĂ©rique. Alors que l'on pouvait s'attendre Ă une meilleureperformance des schĂ©mas cartĂ©siens par rapport Ă aux schĂ©masnon-structurĂ©s de complexitĂ© similaire, nous trouvons qu'un schĂ©ma de lafamille des schĂ©mas de Van Leer a une performance comparable Ă un schĂ©masimilaire sur maillage cartĂ©sien, schĂ©ma qui est proposĂ© par dĂ©faut parle modĂšle CHIMERE de façon opĂ©rationnelle. Au-delĂ de ces expĂ©riencesnumĂ©riques bidimensionnelles idĂ©alisĂ©es, nous comparons la performancede ces deux schĂ©mas dans un contexte tridimensionnel rĂ©aliste inspirĂ© del'Ă©ruption du volcan Puyehue en 2011. Ce nĂ©cessaire jalon doit ĂȘtrecomplĂ©tĂ© par des expĂ©rience Ă rĂ©solution variable pour mener Ă uneĂ©valuation complĂšte des mĂ©rites de la modĂ©lisation multi-Ă©chelles pourles applications en chimie-transport
Vers le Transport Multi-Echelles de Panaches Fins
The distribution of aerosols and trace gases in the atmosphere resultsfrom the emission of primary gaseous and particulate matter, as well astheir transport, sedimentation and (photo-)chemical transformations.Understanding and quantifying these processes in the atmosphere can beaddressed through the use of global-scale or regional-scalechemistry-transport numerical models.CHIMERE is a chemistry-transport model developed mainly at LMD (Mailleret al., 2017). Initially targeted to urban and regional scales, it wasrecently extended to hemispheric scales in order to address theseprocesses on a wider range. While theoretically possible, it isimpractical to use this model to represent interactions betweensmall-scale processes (e.g. pollution in the urban atmospheric boundarylayer) and large-scale processes (e.g. intercontinental transport)controlling dense plumes of gas and aerosols, resulting for instancefrom massive emissions by volcanic eruptions, forest fires and desertaerosol tempests. Indeed such studies requiring both large domains andhigh resolution have a prohibitive numerical cost due to the formulationof CHIMERE on a regular Cartesian mesh. This limitation is shared by allcurrently operational chemistry-transport models. Additionally,traditional Cartesian longitude-latitude meshes pose a numericalsingularity at the poles, where the longitude lines converge.One way to lift these limitations would be to replace CHIMEREâsCartesian mesh by a fully unstructured mesh. Unstructured meshes supportvariable resolution in space, allowing computational resources to befocused in those few key regions (e.g. volcanic eruption) where highspatial resolution is really required. Allowing such multi-scalecapacity would be a significant step forward in the modelling of scaleinteractions in atmospheric chemistry, and would potentially allowbreakthrough for the understanding of such interactions.DYNAMICO, the atmospheric general circulation model recently developedat LMD and LSCE (Dubos et al., 2015) supports unstructured sphericalVoronoi meshes. It is the goal of this PhD project to contribute to theassessment of the viability of numerical methods borrowed from DYNAMICO forlarge-scale transport of sharp plumes. To this end, we compare thenumerical performance of transport schemes formulated on sphericalunstructured meshes (Dubey et al., 2015) with schemes formulated onCartesian spherical meshes avoiding the poles. Schemes of various orderand different treatments of time integration are implemented in eachmesh framework. A suite of test cases is used to evaluate differentproperties of the mesh-scheme pairings. Various metrics are used tostudy stability, monotonicity, convergence and numerical diffusion.While it could be anticipated that Cartesian schemes perform better thantheir unstructured counterpart of similar complexity, we find that ascheme of the Van Leer family on the unstructured mesh has a comparableperformance to a similar scheme on a Cartesian mesh, which is the defaultscheme used operationally by CHIMERE. Beyond these idealizedtwo-dimensional numerical experiments, we compare the performance of thetwo schemes in a realistic, three-dimensional setting mimicking theeruption of the Puyehue volcano in 2011. This necessary milestone is tobe complemented by experiments with variable-resolution meshes leadingto a full assessment of the merits of multi-scale-modellingchemistry-transport applications.La distribution dâaĂ©rosols et de gaz trace dans lâatmosphĂšre rĂ©sulte delâĂ©mission dâespĂšces gazeuses et particulaires primaires, ainsi que deleur transport, de leur sĂ©dimentation et de leurs transformations(photo)chimiques. La modĂ©lisation de ces processus dans lâatmosphĂšrepeut sâaborder au travers de modĂšles de chimie-transport dâĂ©chelleglobale ou rĂ©gionale.Le modĂšle CHIMERE, dĂ©veloppĂ© en grande partie au LMD (Mailler et al.,2017), est un modĂšle de chimie-transport rĂ©gional, rĂ©cemment Ă©tendu auxĂ©chelles hĂ©misphĂ©riques, qui permet dâaborder ces phĂ©nomĂšnes sur unegrande gamme dâĂ©chelles, allant de lâĂ©chelle dâune ville Ă celle dâunhĂ©misphĂšre. Il est toutefois difficile dâutiliser ce modĂšle pourreprĂ©senter les interactions entre phĂ©nomĂšnes de petite Ă©chelle(pollution de la couche limite urbaine) et de grande Ă©chelle (transportĂ lâĂ©chelle continentale ou hĂ©misphĂ©rique) de panaches denses de gaz etdâaĂ©rosols, issus par exemple dâĂ©missions de panaches volcaniques, defeux de forĂȘt, ou dâaĂ©rosols dĂ©sertiques. Cette limitation est un effetde lâimpossibilitĂ© dâutiliser le modĂšle sous sa forme actuelle avec undomaine Ă maille non structurĂ©e, seul type de maillage permettant unerĂ©elle variation de la rĂ©solution en fonction de zones dâintĂ©rĂȘtdĂ©finies par le modĂ©lisateur (zones urbaines, zones dâĂ©mission). Cettelimitation est commune Ă la totalitĂ© des modĂšles de chimie-transportexistants Ă lâheure actuelle, pouvoir la lever serait donc un importantpas en avant pour la comprĂ©hension des interactions dâĂ©chelle dans ledomaine de la chimie atmosphĂ©rique.Une façon de lever ces limitations serait de remplacer le maillagecartĂ©sien de CHIMERE par un maillage non-structurĂ©. En effet lesmaillages non-structurĂ©s permettent de faire varier la rĂ©solution dansl'espace et de concentrer les ressources de calcul dans les quelquesrĂ©gions clĂ©s (p.ex. prĂšs d'une Ă©ruption volcanique) oĂč une hauterĂ©solution spatiale est rĂ©ellement nĂ©cessaire. Introduire une telleflexibilitĂ© multi-Ă©chelle reprĂ©senterait un pas important pour lamodĂ©lisation des interactions d'Ă©chelles en chimie atmosphĂ©rique, etpermettrait potentiellement des percĂ©es dans la comprĂ©hension de cesinteractions.DYNAMICO, le modĂšle de circulation gĂ©nĂ©rale atmosphĂ©rique dĂ©veloppĂ©rĂ©cemment au LMD et au LSCE (Dubos et al., 2015) est basĂ© sur desmaillages de Voronoi non-structurĂ©s sphĂ©riques. L'objectif de cettethĂšse est de contribuer Ă l'Ă©valuation de mĂ©thods numĂ©riques empruntĂ©esĂ DYNAMICO pour le transport Ă grand Ă©chelle de panaches fins. A cettefin nous comparons la performance numĂ©rique de schĂ©mas de transportformulĂ©s sur maillage non-structurĂ© (Dubey et al., 2015) Ă celle deschĂ©mas similaires formulĂ©s sur un maillage cartĂ©sien sphĂ©rique Ă©vitantles pĂŽles. Des schĂ©mas d'ordre variĂ© et avec diffĂ©rents traitements del'intĂ©gration temporelle sont implĂ©mentĂ©s pour chacun des deux types demaillage. Un jeu de cas-test est utilisĂ© pour Ă©valuĂ© diffĂ©rentespropriĂ©tĂ©s des paires maillage-schĂ©ma. DiffĂ©rentes mĂ©triques permettentd'Ă©tudier les propriĂ©tes de stabilitĂ©, monotonocitĂ©, convergence etdiffusion numĂ©rique. Alors que l'on pouvait s'attendre Ă une meilleureperformance des schĂ©mas cartĂ©siens par rapport Ă aux schĂ©masnon-structurĂ©s de complexitĂ© similaire, nous trouvons qu'un schĂ©ma de lafamille des schĂ©mas de Van Leer a une performance comparable Ă un schĂ©masimilaire sur maillage cartĂ©sien, schĂ©ma qui est proposĂ© par dĂ©faut parle modĂšle CHIMERE de façon opĂ©rationnelle. Au-delĂ de ces expĂ©riencesnumĂ©riques bidimensionnelles idĂ©alisĂ©es, nous comparons la performancede ces deux schĂ©mas dans un contexte tridimensionnel rĂ©aliste inspirĂ© del'Ă©ruption du volcan Puyehue en 2011. Ce nĂ©cessaire jalon doit ĂȘtrecomplĂ©tĂ© par des expĂ©rience Ă rĂ©solution variable pour mener Ă uneĂ©valuation complĂšte des mĂ©rites de la modĂ©lisation multi-Ă©chelles pourles applications en chimie-transport
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