Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Numerical programs for simulating flow and reactive transport in porous media are essential tools for predicting reservoir properties changes triggered by CO2 underground injection. At reservoir scale, meshed models in which equations are solved assuming that constant macroscopic properties can be defined in each cells, are widely used. However, the parameterization of the dissolution-precipitation problem and of the feedback effects of these processes on the flow field is still challenging. The problem arises from the mismatch between the scales at which averaged parameters are defined in the meshed model and the scale at which chemical reactions occur and modify the pore network geometry. In this paper we investigate the links between the dissolution mechanisms that control the porosity changes and the related changes of the reactive surface area and of the permeability. First, the reactive surface area is computed from X-ray microtomography data obtained before and after a set of dissolution experiments of pure calcite rock samples using distinctly different brine-CO2 mixtures characterizing homogeneous to heterogeneous dissolution regimes. The results are used to validate the power law empirical model relating the reactive surface area to porosity proposed by Luquot and Gauze (2009). Second, we investigate the spatial distribution of the effective hydraulic radius and of the tortuosity, two structural parameters that control permeability, in order to explain the different porosity-permeability relationships observed for heterogeneous and homogeneous dissolution regimes. It is shown that the increase of permeability is due to the decrease of the tortuosity for homogeneous dissolution, whereas it is due to the combination of tortuosity decrease and hydraulic radius increase for heterogeneous dissolution. For the intermediate dissolution regime, identified to be the optimal regime for increasing permeability with small changes in porosity, the increase of permeability results from a large increase in the mean effective hydraulic radius of the sample.
ISSN: 0169-7722

hal-00617671
https://hal.archives-ouvertes.fr/hal-00617671
DOI : 10.1016/j.jconhyd.2010.07.004

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : Characterizing the trophic relationships between large herbivores and the outstanding plant diversity in rainforest is a major challenge because of their elusiveness. This is crucial to understand the role of these herbivores in the functioning of the rainforest ecosystems. We tested a non-invasive approach based on the high-throughput sequencing of environmental samples using small plant plastid sequences (the trnL P6 loop) and ribosomal ITS1 primers, referred to as DNA metabarcoding, to investigate the diet of the largest neotropical herbivore, the lowland tapir. Sequencing was performed on plant DNA extracted from tapir faeces collected at the Nouragues station, a protected area of French Guiana. In spite of a limited sampling, our approach reliably provided information about the lowland tapir's diet at this site. Indeed, 95.1% and 74.4% of the plant families and genera identified thanks to the trnL P6 loop, respectively, matched with taxa already known to be consumed by tapirs. With this approach we were able to show that two families and eight new genera are also consumed by the lowland tapir. The taxonomic resolution of this method is limited to the plant family and genera. Complementary barcodes, such as a small portion of ITS1, can be used to efficiently narrow identifications down to the species in some problematic families. We will discuss the remaining limitations of this approach and how useful it is at this stage to unravel the diet of elusive rainforest herbivores and better understand their role as engineers of the ecosystem.
ISSN: 1932-6203

hal-01190578
https://hal.archives-ouvertes.fr/hal-01190578
PRODINRA : 209109
PUBMED : 23560107
DOI : 10.1371/journal.pone.0060799

Résumé : La tuberculose, maladie très ancienne, est plus que jamais présentée sur la scène sanitaire mondiale avec 9 millions de nouveaux cas par an. Cette maladie, qui demeure une cause majeure de mortalité, est un des problèmes les plus difficiles à résoudre en santé publique et à échelle internationale. Les diverses programmes de lutte, lancés par l’Organisation Mondiale de la Santé (OMS), pour prévenir et garantir la guérison des patients tuberculeux, se heurtent à des difficultés qui hypothèquent leur efficacité. En effet, l'expansion du virus de rinimunodéficience humaine (VIII) et son influence néfaste sur la susceptibilité à la tuberculose, l'accroissement rapide de la tuberculose multirésistante, la pauvreté ainsi que la croissance démographique, sont un ensemble de facteurs préjudiciables à l'application des mesures préventives et curatives. Les contextes économiques difficiles conduisant indubitablement au cumul de ces facteurs, ont fait une césure entre les pays riches et les pays pauvres quant à l'incidence et la révolution de la tuberculose à échelle mondiale. Pour atténuer la disparité des résultats des luttes antituberculeuses, les méthodologies employées en épidémiologie de la tuberculose doivent s'inscrire dans une démarche d'efficacité. Les marqueurs moléculaires, indispensables à l'identification et à la classification des souches appartenant au complexe Mycobacterium tuberculosis (MTC) ont chacun des potentialités qui leur sont propres dont il convient de cerner pour une utilisation adéquate dans les études épidémiologiques et phylogénétiques. Le but de cette thèse consiste à extraire des connaissances nouvelles des résultats de génotypage stockées dans les bases de données, connaissances relatives au polymorphisme du support génomique pour estimer la contribution de chaque marqueur dans la classification de MTC. Le recours à différentes méthodes de reconstruction phylogénétique et de modélisation des données fut indispensable. A la lumière des résultats obtenus, cette thèse propose une nouvelle méthodologie de classification, pour rétablissement d'une phylogéographie robuste de MTC en relation avec l'histoire des migrations humaines qui aurait débutée en Afrique subsaharienne. Chaque méthode de génotypage ayant une efficience et un cout propres, qu'il convient de mesurer par rapport aux moyens disponibles et aux résultats escomptes, il est donc intéressant de renforcer la connaissance des marqueurs et de proposer différentes alternatives menant à la classification des mycobactéries. Ainsi, les résultats obtenus dans cette thèse apportent plus de cohérence aux solutions proposées pour la caractérisation des clones de MTC circulant dans le monde.
Tuberculosis, very old disease, is more than ever presented on the global health scene with 9 million new cases per year. This disease, which remains a major cause of mortality is one of the most intractable public health and international issues. The various control programs, launched by the World Health Organization (WHO) to prevent and guarantee the cure of tuberculosis patients face difficulties that undermine their effectiveness. Indeed, the expansion of human virus rinimunodéficience (VIII) and its negative influence on susceptibility to tuberculosis, the rapid growth of multidrug-resistant tuberculosis, poverty and population growth, are a set of factors detrimental to application of preventive and curative measures. The difficult economic circumstances undoubtedly leading to accumulation of these factors have a break between rich and poor countries about the impact and the revolution of tuberculosis worldwide. To address the disparity of the results of tuberculosis struggles, the methodologies used in epidemiology of tuberculosis must be part of a process efficiency. Molecular indispensable to the identification and classification of strains belonging to the Mycobacterium tuberculosis complex (MTC) markers each have their own potentials that need to be identified for proper use in epidemiological and phylogenetic studies. The purpose of this thesis is to extract new knowledge of the results of genotyping data stored in databases, knowledge of the polymorphism of genomic carrier to estimate the contribution of each marker in the classification of TCM. The use of different methods of phylogenetic reconstruction and modeling data was essential. In light of the results obtained, the thesis proposes a new classification methodology for a robust recovery phylogeography of TCM in connection with the history of human migration have started in sub-Saharan Africa. Each genotyping method with cost efficiency and equity, should be measured in relation to the resources available and discounts results, it is interesting to strengthen the knowledge of markers and propose alternatives leading to the classification of mycobacteria. Thus, the results obtained in this thesis bring more coherence to the proposed characterization of clones MTC circulating worldwide solutions.

http://www.theses.fr/2012AGUY0518/document

Résumé : La dengue constitue actuellement l'arbovirose la plus répandue sur la planète avec 40% de la population mondiale exposée, soit environ 2,5 milliards de personnes. La maladie est endémique dans tous les continents excepté l'Europe même si les premiers cas de transmission autochtone ont été observés en France métropolitaine et en Croatie en 2010. L'augmentation régulière de son incidence fait actuellement de la dengue un problème de santé publique majeur dans les pays tropicaux et une menace pour d'autres pays du monde. En raison de son mode de transmission, la dengue constitue une maladie étroitement liée à l'environnement. L'urbanisation constitue un facteur important dans l'émergence ou la réémergence d'épidémies de dengue dans les pays tropicaux. Cette étude menée a pour objet d'analyser les liens existant entre le domaine de la santé (situation sanitaire et épidémiologique de la dengue) et de celui de l'environnement (évolution de l'urbanisation) en Guadeloupe continentale entre 2000 et 2008.Pour ce faire, les cas suspects et confirmés de dengue ont été recueillis. L'incidence pour ces deux types de cas a été calculée puis représentée à deux échelles administratives différentes: communes et sections. Les facteurs environnementaux comprenant les variables physiques et socio-démographiques ont été pris en compte pour la définition, l'identification et l'analyse de l'évolution des contextes d'habitation durant la période étudiée. Deux méthodes ont été utilisées: la classification «Raster» consistant en une analyse régulière basée sur des mailles de taille identique et la classification « Vecteur» s'appuyant sur les limites administratives des sections. Ces classifications ont permis de décrire la répartition des différents contextes d'habitation sur le territoire de la Guadeloupe et d'obtenir des indicateurs qui ont été analysés en relation avec les données sanitaires. Il a été mis en évidence que la situation épidémiologique de la dengue dans le département s'est significativement aggravée au cours de la période étudiée. Des épidémies majeures sont apparues en 2001, 2005/2006 et 2007. Le nord Basse-Terre, la région Pointoise ainsi que le sud-est de la Grande-Terre, de la ville du Gosier à Saint-François le long de la côte, sont les régions les plus concernées par l'augmentation d'incidence de la maladie. Concernant les contextes d'habitation, huit contextes distincts ont été identifiés: touristique, naturel, intermédiaire, agricole, résidentiel, rural, périurbain et urbain. Le contexte intermédiaire correspond à des régions de transition entre les autres contextes d'habitation. La différence entre les contextes agricoles et ruraux réside dans la prédominance de surface agricole pour le premier alors que le contexte rural est caractérisé par les espaces cultivés habités. L'évolution surfacique de ces contextes au cours du temps a été analysée en relation avec les incidences. Les résultats montrent que les contextes d'habitation sont statistiquement.associés à l'incidence de la dengue en Guadeloupe. En particulier, les contextes touristiques, résidentiels et ruraux possèdent une association positive élevée avec l'incidence de la dengue.
At present, dengue fever has become the arbovirose the most wide-spread worldwide with 40 % ofthe exposed population, 2,5 billion people. The disease is endemie in all the continents excepted Europe even though the fust cases ofautochthonoustransmissionwere observedinmetropolitanFranceandCroatiain2010.Because oftherecentincrease of its incidence, dengue fever is now a major public health problem in the tropical countries and a threat for the other countries in the worldwide. Due to its mode oftransmission, the disease is closely linked to the environment. Urbanization is an important factor ofthe emergence or the re-emergence of dengue in the tropical countries. This study aims to analyze the links between health and environment domains, which correspond to the epidemiological situation of the dengue and the evolution ofthe urbanization in Guadeloupe.Information about suspect and confirmed cases of dengue were collected. The incidence of suspect and confirmed cases has been estimated, then represented at two different administrative boundaries: communes and sections. Environmental factors including the physical and socio-demographic variables were taken into account to the definition, the identification and the analyze ofevolution of the housing patterns during the studied period. Two methods were used: Il Raster" consisting of a regular analysis based on squares units and "Vector" based on the administrative limits of sections. These classifications allowed to describe the distribution ofthe different housing patterns ofGuadeloupe and to estimate indicators for the analyzing of sanitary data. The results highlight a worsening ofepidemiological situation ofthe dengue over the time in the department. Major outbreaks occurred in 2001,2005/2006 and 2007. The north Basse-Terre, the Pointe-à-Pitre urban area as weIl as the whole coast (frOID the city of Gosier to Saint-François) ofthe southeast ofGrande-Terre were the most affected regions by the increase ofincidence of dengue. Concerning the housing classes, eight different patterns were identified: tourist, natural, intermediate, agricultural, residential, rural, suburban and urban. The intermediate class corresponds to buffer regions between the other patterns. The difference between the agricultural and rural contexts lies in the predominance ofagricultural surface for the first one while the rural context is characterized by the inhabited farmland. The evolution over time of spatial extend ofthese patterns was described in relation with incidence. Results showed that the housing patterns are statically associated with the incidence ofdengue in Guadeloupe. In particular, the touristic, residential and rural patterns have a high positive association with dengue incidence.

http://www.theses.fr/2012AGUY0565/document

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The 40Ar/39Ar geochronological technique has significantly contributed to the study of crustal deformation. However, the frequent occurrence of extraneous argon in high-pressure terrains can make the interpretation of 40Ar/39Ar ages problematic. This contribution attempts to: i) characterize the distribution and origin of extraneous argon in the Cycladic Blueschist Unit (CBU, Greece) by applying the 40Ar/39Ar dating technique on three Cycladic islands, Syros, Tinos and Ios, which span a complete transect of the CBU and ii) discuss regional implications for the tectonometamorphic evolution of the CBU. Our results, combined with ages available in the literature, show that periods of peak-burial conditions (55–49 Ma) and syn- (45–38 Ma) to post-orogenic exhumation (37–21 Ma) are well constrained in the CBU by the 40Ar/39Ar method. Moreover, Variscan apparent ages are preserved in the Cycladic basement of Ios, indicating that the 40Ar/39Ar system was not completely reset during the Eocene metamorphic episode. Additionally, our 40Ar/39Ar data show that the occurrence of extraneous argon is heterogeneously distributed in the CBU. While high-pressure rocks of Syros and Tinos are only locally affected, extraneous argon is clearly evidenced in the CBU of Ios, yielding geologically meaningless ages up to 900 Ma. On each island, the most affected ages were obtained in microstructures where fluid circulation is enhanced such as shear bands or strain shadows around garnets. We suggest that the Cycladic Basement, a polymetamorphic continental unit, behaved as an argon reservoir that has been mobilized by fluid circulation at the Eocene. These argon-enriched fluids have then heterogeneously contaminated metamorphic rocks when percolating through the CBU. Finally, we claim that a minimum closure temperature of 550 °C must be accepted for the phengites of the CBU and conclude that volume diffusion is not the main process resetting the argon isotopic system in high-pressure rocks compare to recrystallization enhanced by fluid circulation and deformation.
ISSN: 0024-4937

Droits : http://creativecommons.org/licenses/by-nc-nd/
insu-01424268
https://hal-insu.archives-ouvertes.fr/insu-01424268
https://hal-insu.archives-ouvertes.fr/insu-01424268/document
https://hal-insu.archives-ouvertes.fr/insu-01424268/file/Valentin-Lithos-Accepted-2016.pdf
DOI : 10.1016/j.lithos.2016.12.013