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Séon-Massin, Nirmala. "La radiation adaptative en environnement hétérogène : effets de la dispersion et des perturbations." Paris 6, 2006. http://www.theses.fr/2006PA066123.
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Peccoud, Jean. "Spéciation écologique et radiation adaptative dans le complexe du puceron du pois, Acyrthosiphon pisum." Rennes, Agrocampus Ouest, 2009. http://www.theses.fr/2009NSARA063.
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L’hypothèse de la spéciation écologique stipule que la sélection de traits adaptatifs à des niches écologiques différente peut engendrer un isolement reproducteur entre populations, même si ces dernières ne sont pas isolées géographiquement. Les exemples documentés de spéciation écologique dans la nature sont rares, mais les insectes phytophages spécialisés sur une gamme d’hôtes restreinte en sont de bons candidats. En effet, la spécialisation de populations d’insectes sur des plantes-hôtes différentes peut engendrer diverses formes d’isolement reproducteur, tel un isolement par l’habitat ou un isolement temporel. Ainsi, le puceron du pois, Acyrthosiphon pisum, présente à travers le monde des biotypes sympatriques génétiquement différenciés et formetement spécialisés sur certaines espèces de fabacées cultivées comme le pois, le trèfle et la luzerne. Spécifiquement, nous nous sommes intéressés (i) à la diversité écologique et au degré d’isolement reproducteur des biotypes trouvés sur de nombreuses plantes sympatriques, cultivées et sauvages (ii) à la spécialisation écologique des populations du puceron du pois dans une région d’introduction en s’interrogeant sur leur niveau de polyphagie et surs origines, (iii) à l’histoire évolutive de nombreuses populatins spécialisées à travers le monde. Nous avons enfin entrepris (iv) la recherche de symbiotes facultatifs transmis maternellement au sein des différents biotypes et pouvant éventuellement intervenir dans la spécialisation écologique de ces derniersThe hypothesis of ecological speciation states that the selection of adaptive traits in different ecological niches can causes reproductive isolation, even if populations under divergent selection are not geographically isolated. Documented examples of ecological speciation are scarce, but specialized phytophagous insects feedingon restricted host ranges are good candidates. Indeed, specialization of insect populations of different host plants can cause various forms of reproductive isolation, such as habitat isolation or temporal isolation. The pea aphid, Acyrthosiphon pisum, thus presents genetically differentiated and highly specialized sympatric biotypes feeding on restricted host ranges are good candidates. Indeed, specialization of insect populations on different host plants can cause various forms of reproductive isolation, such as habitat isolation or temporal isolation
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Ropiquet, Anne. "Etude des radiations adaptatives au sein des Antilopinae (Mammalia, Bovidae)." Paris 6, 2006. http://www.theses.fr/2006PA066407.
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Avec près de 120 espèces, les Antilopinae (Mammalia, Bovidae) posent encore de nombreux problèmes de systématique en raison des difficultés d’échantillonnage et du manque de données moléculaires disponibles. Lors de ce travail, sept gènes ont été séquencés sur tous les genres de Bovidae. Une nouvelle méthode de "superarbre" est proposée pour limiter les biais expérimentaux et méthodologiques lors de la reconstruction phylogénétique. Les résultats ont permis de présenter une classification, où sont notamment décrits deux nouveaux genres, Arabitragus et Nilgiritragus. Au sein des Caprini, l’origine de Capra apparaît liée à une hybridation inter-spécifique. Seules deux radiations sur cinq sont identifiées comme adaptatives : la radiation en tribus au Miocène moyen, et celle des genres de Caprini au Miocène supérieur. La période de 9-8 Ma apparaît cruciale pour l’évolution des Bovidae, avec de nombreux échanges entre l’Afrique et l’Eurasie et la diversification de la plupart des tribus.
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Le, Péchon Timothée. "Systématique des dombeyoideae (Malvaceae, ex-"Sterculiaceae") des Mascareignes : approches morphologique et moléculaire." Paris 6, 2009. http://www.theses.fr/2009PA066069.
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La sous-famille des Dombeyoideae (Malvaceae, « ex-Sterculiaceae ») présente dans l’archipel des Mascareignes (îles de la Réunion, Maurice et Rodrigues) une diversité spécifique importante (4 genres, 23 espèces dont 22 sont endémiques) et des traits d’histoire de vie originaux, telle la dioécie. Notre objectif a été d’étudier les relations de parenté entre les taxons mascarins et les représentants africains, malgaches et asiatiques de cette sous-famille. Des caractères morphologiques et moléculaires ont été utilisés indépendamment et conjointement pour reconstruire des scénarios phylogénétiques. Les analyses montrent que les Dombeyoideae des Mascareignes sont polyphylétiques et regroupés au sein de quatre clades ayant chacun pour origine un unique évènement de dispersion/colonisation de Madagascar vers l’archipel. L’inférence de l’évolution des systèmes de reproduction montre que la dioécie dériverait de l’hermaphrodisme. Aux Mascareignes, la séparation des sexes se serait ainsi différenciée au moins trois fois de façon convergente
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Ramdarshan, Anusha. "Adaptive radiations and ecological diversity of primates during the early Tertiary." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20127.
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Juste après son apparition au début de l'Ère Tertiaire, l'ordre des Primates connaît plusieurs phases de diversification intenses. Ces épisodes successifs sont à l'origine de l'émergence des groupes actuels. Malgré l'importance de ces évènements, leurs modalités restent peu connues, particulièrement l'importance des facteurs écologiques. En Europe et en Amérique du Nord, la transition Paléocène-Éocène est marquée par un réchauffement climatique majeur. C'est à cette époque que les primates modernes (Euprimates) apparaissent, se dispersent, et se diversifient de manière explosive au cours de l'Éocène. Ce travail a pour objectif de caractériser l'émergence de cette diversité à travers les facteurs écologiques tels que le partage des ressources, les phénomènes de compétition, et les changements paléoenvironnementaux. Dans ce but, l'étude de la structure des dents et des micro-usures laissées par le bol alimentaire permet la reconstruction du régime alimentaire des primates paléogènes (Adapiformes, Omomyiformes, Anthropoidea et Plesiadapiformes), l'un des meilleurs indicateurs de l'écologie d'un animal.En Europe, les premiers euprimates (e.g., Donrussellia [adapiformes]), bien qu'ayant un patron dentaire de type insectivore, étaient majoritairement frugivores et secondairement insectivores. Ils occupaient ainsi des niches distinctes des plésiadapiformes (folivores, frugivores et gommivores). La diversification des euprimates au cours de l'Éocène a conduit à l'augmentation des pressions de compétition au sein des communautés et à l'apparition de spécialisations écologiques. Par exemple, les adapinés, initialement frugivores, ont montré une évolution de leur régime alimentaire par l'intégration de feuilles et d'objets durs.En Asie, l'étude des communautés fossiles a mis en exergue une forte pression de compétition entre les formes de petite taille (éosimiidés, tarsiidés, adapidés), qui avaient tous un régime alimentaire à base de fruits et d'insectes. Les anthropoïdes asiatiques (amphipithècidés) montrent des spécialisations écologiques très singulières avec notamment un régime alimentaire à base d'objets durs. En Afrique, les communautés éocènes témoignent d'une diversité importante, avec la colonisation des niches insectivores (adapiformes), frugivores (adapiformes, strepsirhiniens et anthropoïdes) et folivores (adapiformes, anthropoïdes).Cette étude a mis en exergue la diversité et la variabilité du régime alimentaire qui peut exister pour une espèce donnée (actuelle ou fossile) en fonction des facteurs biotiques (compétition) et abiotiques (environnement, géographie). La comparaison entre les différents continents montre que les primates (adapiformes, omomyiformes et anthropoïdes) n'occupaient pas les mêmes niches écologiques au sein des différentes communautés. Ces différences au niveau du partage des ressources et des phénomènes de compétition se sont répercutées sur la dynamique des différentes radiationsSoon after its appearance at the beginning of the Tertiary, the Primate order underwent several successive episodes of diversification which were the basis for the emergence of the higher taxonomic groups that can be observed in nature today. Despite the importance of these events, little is known regarding the factors that governed them, in particular the importance of the ecological factors involved. The Paleocene-Eocene transition in North America and Europe was marked by a period of major global warming. It was during this time that modern primates (Euprimates) appeared and dispersed before experiencing an explosive diversification throughout the Eocene. This study aims to characterize the emergence of this diversity through the identification of ecological factors, such as environment, resource partitioning and competition. In this framework, the study of dental structure and of dental microwear is used to reconstruct the diet of Paleogene primates (Adapiformes, Omomyiformes, Anthropoidea and Plesiadapiformes), one of the best indicators of the ecology of a given animal. In Europe, although exhibiting a dental morphology better suited to insect-eating, the first euprimates (e.g., Donrussellia [adapiformes]) were fruit-eaters, only supplementing their diet with insects. They mostly occupied different niches to co-occurring plesiadapiforms (leaf-, fruit- and gum-eaters). The diversification of euprimates led to the increasing competition among primate communities and to the apparition of different dietary specializations. For example, Adapines, initially having a diet based on fruit, show a dietary shift by incorporating leaves and harder objects in their diet.In Asia, the study of fossil primate communities has highlighted resource partitioning and competition among small-bodied primates (eosimiids, tarsiids, and adapids), which all had a diet based on fruit and insects. Asian anthropoids (amphipithecids) show some singular ecological specialization towards sclerocarpic foraging.In Africa, Eocene primates show a high diversity, with the colonisation of numerous ecological niches such as insect-eating (adapiformes), fruit-eating (adapiformes, strepsirhines and anthropoids) et leaf-eating (adapiformes, anthropoides).This study highlights dietary diversity and variability which can exist for a given primate (extant or fossil) according to factors which can be biological in nature (i.e., competition) or not (i.e., environment, geography). The comparison between the different continents demonstrates that primates (Adapiformes, Omomyiformes, and Anthropoidea) occupied different niches in different primate communities. These differences in resource partitioning and competition are most probably reflected in the different paths these adaptive radiations took
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Auvinet, Juliette. "Histoire évolutive des remaniements chromosomiques en liaison avec la mobilisation d'éléments transposables chez les téléostéens antarctiques Nototheniidae : la radiation adaptative du groupe " Trematomus "." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS371/document.
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L’alternance de périodes glaciaires et interglaciaires durant les 20 derniers Ma a mené à des changements environnementaux répétés au niveau du plateau continental antarctique. C’est dans ce contexte que les téléostéens de la famille des Nototheniidae se sont adaptés et diversifiés à travers plusieurs vagues de radiations (dont les Trematominae), dominant l’Ichtyofaune australe. Parmi les Nototheniidae, le groupe « Trematomus » (genres Cryothenia, Pagothenia, Trematomus et Indonotothenia) est celui où l’on observe la plus grande diversité chromosomique, avec des nombres diploïdes de chromosomes allant de 24 à 58, impliquant de nombreux réarrangements ayant accompagné les spéciations. Nous avons cherché à caractériser ces remaniements chromosomiques. Avec un caryotype ancestral inféré de 2n = 48, une conservation des unités chromosomiques entre espèces, et une constance des tailles de génome, l’hypothèse de réarrangements structuraux sans polyploïdisation préalable est la plus probable. Afin de reconstruire l’histoire évolutive de ces événements, nous avons recherché les homologies chromosomiques interspécifiques. Ceci nous a permis de reconstituer les remaniements (majoritairement des fusions) que nous avons repositionnés sur la phylogénie résolue des « Trematomus ». Contrairement à ce qui a été publié pour le genre Notothenia, nos résultats suggèrent des acquisitions multiples et indépendantes. Les éléments transposables (ETs) peuvent être impliqués dans les remaniements chromosomiques par le biais de recombinaisons ectopiques. Ils participent alors à la diversification des lignées au cours de l’évolution. En raison de leur régulation épigénétique, leur mobilisation massive peut être induite en cas de variations environnementales importantes. Nous nous sommes intéressés à trois super-familles d’ETs (DIRS, Gypsy and Copia) dans ces génomes. Les DIRS1 ont montré des patrons d’insertions en points chauds dans les régions centromériques et péricentromériques. Etant donné leur mode de transposition décrit et leur propension à s’insérer dans des copies préexistantes, nous proposons un rôle des éléments DIRS1 comme facilitateurs des fusions observées lors de la diversification des « Trematomus »In the last 20 My, multiple glacial-interglacial cycles led to strong and repeated environmental changes on the Antarctic continental shelf. In this changing environment, nototheniid fishes diversified through several rounds of species radiation (one of which within Trematominae), and now constitute the dominant group in Antarctic teleosts. Among Nototheniidae, the group « Trematomus » (genera Cryothenia, Pagothenia, Trematomus and Indonotothenia) exhibits the highest chromosomal diversity, with diploid chromosome numbers ranging between 24 and 58, involving many rearrangements probably linked to speciation. We characterized the nature of these chromosomal repatternings. With an inferred ancestral state of 2n = 48 acrocentric chromosomes, a conserved number of chromosomal structural units, and a constancy of the genomes sizes we measured; the hypothesis of structural modifications is favored rather than a whole genome duplication associated to drastic reductions. In order to reconstruct an evolutionary scenario of such chromosomal rearrangements accompanying the trematomine diversification, we identified interspecific chromosomal homologies. This allowed us to reconstruct the rearrangements events (mostly centric and tandem fusions). We plotted them on a phylogeny we reconstructed based on our own ddRAD-seq data. Contrary to what was reported for the Notothenia, our results are in favor of independent acquisitions. Transposable elements (TEs) can lead to chromosomal rearrangements through ectopic recombination events, hinting at a role as drivers of specific-lineage diversification. Moreover, due to their epigenetic regulation, TEs can be mobilized when thermic changes occur. We focused on three retrotransposon superfamilies (DIRS, Gypsy and Copia) in nototheniid genomes. The DIRS1 showed unexpected accumulation patterns of insertion in the centromeric and pericentromeric regions. Given the mechanism of DIRS1 transposition and their tendency to sometimes insert on pre-existing copies (homing), we suggest a role of DIRS1 elements as facilitators of the fusions that occurred during the trematomine radiation
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Labonne, Gaëlle. "Modèle de développement et évolution du patron dentaire chez les rongeurs actuels et fossiles : radiation adaptative et émergence de phénotype : le cas des Arvicolinae (Rodentia)." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS086/document.
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L’évolution de la dentition des mammifères se caractérise par d’importantes innovations morphologiques comme la mise à occlusion et l’hétérodontie. Parmi rongeurs, dont la formule dentaire est fortement réduite, les arvicolinés possèdent une dentition hautement dérivée, avec des molaires prismatiques et hypsodontes. L’objectif de cette thèse est d’explorer les différentes innovations morphologiques de la dentition au travers des aspects développementaux et adaptatifs. Les méthodes de morphométrie géométrique sont utilisées sur les molaires, les incisives et les mandibules afin d’explorer les dynamiques de développement et d’évolution de la dentition. Un modèle développemental permettant de prédire les proportions de molaires inférieures est examiné et validé à l’échelle de l’ordre des rongeurs ; il peut également être étendu à la prémolaire. De plus, le lien entre la morphologie dentaire, notamment les proportions de molaires, et le régime alimentaire est complexe, un caractère morphologique ne reflétant pas directement une alimentation. Cependant les covariations entre les molaires marquent le mouvement de mastication et ainsi la fonction. Nos résultats confirment une imbrication complexe des contraintes historiques, fonctionnelles et développementales dans l’interprétation des morphologies. Les différentes composantes de la mandibule présentent une organisation hiérarchique complexe. Le développement de la dentition des mammifères est gouverné par des processus similaires mais des mécanismes tels que l’hétérochronie ont pu conduire à une diversification des phénotypes au cours du tempsThe evolution of mammalian dentition is defined by profound morphological modifications as occlusion and heterodonty. Among rodents, characterized by a reduced dental formula, arvicolines have a highly derived dentition, with prismatic and hypsodont molars. The aim of this Ph.D thesis is to explore various morphological innovations through developmental and adaptive aspects. Geometric morphometric methods were used on molars, incisors and mandibles to investigate the dynamics of development and evolution of dentition. A developmental model predicting molar proportions is tested and confirmed for the rodent order; it could be also extended to the premolar. The relationship between dental morphology, in particular molar proportions, and diet is complex, diet being not directly inferred from one morphological trait. Yet, covariations between molars inform on masticatory movement and thus on function. Our results confirmed that morphologies could be understood from a complex combination of historical, functional and developmental constraints. The various structures of the mandible have a complex hierarchical organization. The development of mammalian dentition is controlled by similar processes but through times, mechanisms as heterochrony may lead to a diversification of phenotypes
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Octave, Nadia. "La radiothérapie adaptative et guidée par imagerie avec la technologie Cone-Beam CT : mise en oeuvre en vue du traitement de la prostate." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30207/document.
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L'imagerie est maintenant partie intégrante des traitements de radiothérapie. Avec la technologie CBCT embarquée sur les appareils de traitement, l'imagerie tomographique permet non seulement de repositionner fidèlement le patient tout au long de son traitement mais aussi d'adapter la planification initiale aux modifications quotidiennes de volume. C'est la radiothérapie adaptative, objet des travaux de cette thèse. Nous avons établi les limites techniques de précision de repositionnement des équipements utilisé. Ensuite, à partir des acquisitions CBCT quotidiennes de patients traités pour la prostate, nous avons élaboré une stratégie de traitement basée sur une banque de plans personnalisés. Nous avons mis au point une méthode semi-automatique de sélection du plan de traitement du jour qui a montré une efficacité supérieure à la sélection par des opérateurs expérimentés. Enfin, nous avons quantifié les doses additionnelles à la dose thérapeutique associées à l'utilisation quotidienne de l'imagerie CBCT. En conclusion, on peut dire qu'avec l'imagerie CBCT embarquée, on peut voir ce que l'on veut traiter, irradier ce que l'on a vu et contrôler ce qu'on a traitéImaging is now fully integrated in the radiation therapy process. With on-board CBCT systems, tomography imaging allows not only patient positioning but also treatment planning adaptation with patient anatomy modifications, throughout the entire treatment. This is called adaptive radiation therapy, and is the main subject of this PhD thesis. During this work, we measured the repositioning accuracy of the system used. We also developed a treatment strategy using daily CBCT images and a personalized plan database to adapt treatment plan to patient anatomy. We found a way to select the daily treatment plan that shows superiority over operator selection. Then we also quantified the additional dose delivered while using this technique and the impact with regards to the risks added to patients. As a conclusion, with CBCT imaging, radiation therapy has entered an era where one can see what need to be treated, can treat what has been seen and can control what has been treated
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CASNER, ALEXIS. "Déformations, manipulations et instabilités d'interfaces liquides induites par la pression de radiation d'une onde laser." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2002. http://tel.archives-ouvertes.fr/tel-00001637.
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Ce travail est consacré à l'étude expérimentale des effets de la pression de radiation d'une onde laser continue sur une interface liquide. Les propriétés particulières du ménisque séparant deux phases liquides en coexistence au voisinage de leur point critique de démixtion nous ont permis de visualiser directement des déformations stationnaires d'interface de taille micrométrique. Au stade linéaire, i.e pour des intensités laser modérées, une loi d'échelle exprimant la hauteur des déformations a été validée, ceci pour les deux sens de propagation du faisceau relativement à l'interface. Pour des excitations laser plus élevées, une brisure de symétrie vis à vis du sens de propagation a été mise en évidence. On observe en effet la formation de doigts de grand rapport d'aspect, ou la brisure de l'interface suite à une instabilité optohydrodynamique, suivant que le faisceau se propage du milieu le moins réfringent au milieu le plus réfringent, ou inversement. Ces caractéristiques ont été exploitées pour créer et stabiliser sous champ laser des ponts liquides de rapports d'aspect bien supérieurs à la limite de l'instabilité de Rayleigh-Plateau des colonnes liquides. Les déformations thermocapillaires, engendrées par la faible élévation de température induite par le faisceau laser, ont également été caractérisées, afin de les distinguer sans ambiguité des déformations engendrées par la pression de radiation seule.
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Mokrani, Sofiane. "Maintenance de la stabilité chromosomique des cellules souches neurales murines au cours du développement et après un stress génotoxique aiguë ou chronique Impaired brain development and behavior of Xlf null mice linked to chromosome instability-induced premature neurogenesis Higher Chromosome Stability in Mouse Embryonic Neural Stem and Progenitor Cells than in Fibroblasts in Response to Acute or Chronic Genotoxic Stress." Thesis, Institut polytechnique de Paris, 2019. http://www.theses.fr/2019IPPAX010.
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Une exposition prénatale aux radiations ionisantes est associée au développement de pathologies neurodéveloppementales liées à l’induction de dommages à l’ADN dans les cellules souches et progéniteurs neuraux (CSPN). Ainsi, la stabilité génétique des CSPN est cruciale pour le développement et l’homéostasie du cerveau. Cependant, des altérations génomiques au niveau des CSPN au cours du développement pourraient promouvoir la diversité neuronale. XLF est un composant de la voie de réparation d’ADN par NHEJ (pour Non-Homologous End-Joining). Nous avons montré une augmentation de l’instabilité des CSPN dans le cerveau embryonnaire des souris Xlf-/- qui pourrait perturber la neurogenèse au cours du développement, et ainsi être responsable d’altérations comportementales identifiées chez ces souris à l’âge adulte. A l’aide d’approches cytogénétiques, nous avons comparés la stabilité chromosomique des CSPN et des fibroblastes embryonnaires murins (MEF) exposés à un stress génotoxique aigue (irradiation γ) ou chronique (incorporation de thymidine tritiée dans l’ADN). Nos résultats démontrent que les CSPN maintiennent leur intégrité génétique de façon plus efficace que les MEF. En effet, les CSPN semblent avoir de meilleures capacités de réparation des dommages à l’ADN que les MEF, ce qui leur permet de développer une réponse adaptative à un stress génotoxique chronique. Cette réponse adaptative implique XLF et agit conjointement avec les points de contrôle du cycle cellulaire et l'apoptose pour préserver la stabilité du génome et éliminer les cellules endommagées. L’ensemble de nos résultats apporte la démonstration d’une réponse robuste aux dommages de l'ADN dans les CSPN et souligne l'importance de XLF lors du développement du cerveauPrenatal exposure to ionizing radiation has been associated with many neurodevelopmental disorders due to the DNA damage induced in neural stem and progenitors cells (NSPC). Thus, genetic stability of NSPC is crucial for brain development and homeostasis. Nevertheless, genomic alterations occurring during development in NSPC may have a potential impact on the physiological neuronal diversity. XLF is a component of the NHEJ (Non-Homologous End-Joining) repair pathway. Here, we show that NSPC from Xlf-/- embryos exhibit increased chromosome instability, leading to premature neurogenesis and consequently neurobehavioral disorders. Using cytogenetic approaches, we compared the chromosome stability of mouse embryonic NSPC and fibroblasts (MEF) exposed to acute (γ-irradiation) or chronic (incorporation of tritiated thymidine into DNA) genotoxic stress. Our results demonstrate the higher capacity of NSPC as compared to MEF to maintain their genomic integrity. We evidenced that NSPC have more efficient DNA repair activity than MEF, allowing them to develop an adaptive response to chronic genotoxic stress. This adaptive response involves XLF and acts together with apoptosis and cell cycle checkpoints to preserve the stability of the genome and to eliminate damaged cells. Altogether, our results provide new insights into the robust DNA damage response in NSPC and highlight the importance of Xlf during brain development
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Lahaye, Renaud. "Phylogénie moléculaire des secamonoideae (Apocynaceae S. L. ) : histoire biogéographique et évolution des formes de croissance." Toulouse 3, 2005. http://www.theses.fr/2005TOU30253.
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Les relations phylogénétiques au sein de la sous-famille des Secamonoideae ont été étudiées en utilisant les régions chloroplastiques des introns 5'trnK et trnL, des espaceurs trnT-L et trnL-F, et du gène matK. Ces séquences nucléotidiques se sont révélées être phylogénétiquement congruentes. Les analyses parcimonieuses et Bayésiennes de la matrice combinée positionnent les Secamonoideae comme groupe frère des Asclepiadoideae. A l'intérieur des Secamonoideae, les genres Secamonopsis, Pervillaea, et Toxocarpus sont monophylétiques. Le genre Calyptranthera est paraphylétique et la monophylie du principal genre Secamone reste incertaine. Les phylogénies transformées par NPRS et datées à partir de l'apparition de Secamone volubilis sur l'île de La Réunion estiment l'origine des Secamonoideae à -15 millions d'années, longtemps après la fragmentation du Gondwana. Les Secamonoideae ont colonisé Madagascar à partir d'un ancêtre Africain durant le Miocène. Sur l'île, la sous-famille montre une radiation adaptative avec des spéciations rapides et une diversification morphologique importante. Durant le Pliocène, il apparaît dans le genre Secamone plusieurs dispersions à partir de Madagascar vers l'Asie et l'Afrique, ainsi que des échanges entre ces deux continents. La distribution actuelle de la sous-famille autour de l'Océan Indien serait due principalement à des dispersions sur de longues distances. Durant la radiation des Secamonoideae à Madagascar, des formes arbustives apparaissent dans cette sous-famille majoritairement lianescente, plusieurs fois et indépendamment dans différents clades. Les analyses biomécaniques, anatomiques, et développementales, d'une espèce arbustive, Secamone sparsiflora, ont montré des caractéristiques semblables aux jeunes stades de développement des lianes d'un clade frère. La forme arbustive serait due, dans ce cas, à des processus hétérochroniques avec rétention de caractéristiques juvéniles au niveau du développement du bois durant pratiquement toute la trajectoire de développement de Secamone sparsifloraPhylogenetic relationships within the subfamily Secamonoideae are inferred from four chloroplast regions: both the introns 5'trnK and trnL, the spacers trnT-L et trnL-F, and the gene matK. The study shows that these nucleotide sequences are phylogenetically congruent. Maximum parsimony and Bayesian analyses of the combined matrix support the position of the Secamonoideae as sister group to the Asclepiadoideae. Within the Secamonoideae, the genera Secamonopsis, Pervillaea, and Toxocarpus are monophyletic. The genus Calyptranthera is paraphyletic and the monophyly of the main genus Secamone remains uncertain. A Maximum Likelihood tree obtained without molecular clock constraint, transformed by NPRS, and calibrated by the appearance of Secamone volubilis on the volcanic island La Reunion, estimated the divergence of the Secamonoideae at about –15 millions years, latter than the fragmentation of the Gondwana. The subfamily has reached Madagascar from an African ancestor during the Miocene. On the island, the Secamonoideae show an adaptive radiation with rapid speciations and an important morphological diversification. During the Pliocene, the main genus Secamone shows several dispersals events from Madagascar back to Africa, and from Madagascar to Asia. There has been also exchanges within this genus between Africa and Southeast Asia in the early Pliocene. The actual distribution of the Secamonoideae around the Indian Ocean Basin would be mainly due to long-distance dispersal events. .
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Mestrovic, Ante. "Integration of daily imaging, plan adaptation and radiation delivery for near real-time adaptive radiation therapy." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/3990.
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The primary objective of this research was to develop and implement a new approach to on-line adaptive radiation therapy (ART) in which daily imaging, plan adaptation and radiation delivery are temporally integrated and performed concurrently. The advantages of this approach are: reduction of treatment time compared to conventional on-line ART; ability to perform a complete plan re-optimization with minimal extension of treatment time; ability to detect and correct for intra-fractional patient motion.
This work was motivated by an initial study which compared four radiosurgery techniques. This study was the first quantitative analysis of the correlation between patient anatomy and the quality of treatment plans produced by different radiosurgery techniques. A number of different relationships, both qualitative and quantitative, were discovered between patient anatomy and dosimetric parameters for different techniques. The results were used to successfully predetermine the optimal radiosurgery technique based on patient anatomy.
The first step in developing a new approach to on-line ART involved accelerating plan adaptation (re-optimization) using direct aperture optimization (DAO). A series of techniques for adapting the original treatment plan to correct for the deterioration of dose distribution quality caused by the anatomical deformations were investigated. Through modification of the DAO algorithm the optimization search space was reduced and the plan adaptation was significantly accelerated. Next, a new approach to on-line ART was proposed and investigated, in which accelerated plan adaptation and radiation delivery were integrated together and performed concurrently. A fundamental advantage of this approach is that most of the plan re-optimization was performed during radiation delivery, so the time spent adapting the original plan did not significantly increase the overall treatment time. Finally, daily imaging, accelerated plan adaptation and radiation delivery were all temporally integrated using an integrated Linac/Cone Beam CT system. Intra-fractional patient images were used to successfully re-optimize the original treatment plan in near real-time to account for anatomy deformations.
This thesis concludes that integration of daily imaging, plan adaptation and radiation delivery for near real-time ART is both feasible and advantageous. With further advances in related technologies, it promises to become a part of clinical practice in the near future.
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Hilton, Zoe. "Physiological adaptation in the radiation of New Zealand triplefin fishes (Family Tripterygiidae)." Thesis, University of Auckland, 2010. http://hdl.handle.net/2292/5902.
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Physiological adaptation to divergent environments is a poorly understood factor in adaptive radiation. New Zealand (NZ) triplefin fishes (Tripterygiidae) have undergone a radiation associated with habitat diversification within NZ's coastal waters, where 26 closely-related endemic species occur in overlapping but divergent habitats, partitioned by depth and exposure. By investigating the relationship between respiratory physiological traits and habitat in these fishes, this thesis examines whether there is evidence in this group to support two proposed criteria for adaptive radiation; phenotype-environment correlation and trait utility. Significant interspecific differences were observed in rates of oxygen consumption (VO2) and critical oxygen concentration (O2 crit) in 12 species of triplefin examined. O2 crit correlated with species' habitat depth, with intertidal species displaying greater hypoxia tolerance than subtidal species, thus demonstrating phenotype-environment correlation and trait utility in relation to hypoxia exposure. Interspecific differences in VO2 were significantly influenced by phylogeny, indicating a lack of strong environmental selection on VO2. However, there was some indication of lower VO2 in species occupying more exposed habitats. Mitochondrial respiration was also examined in three species; the intertidal species displayed higher cytochrome c oxidase activity and was able to maintain efficient oxidative phosphorylation at higher temperatures than the two subtidal species, further indicating phenotype-environment correlation and trait utility. Haemoglobin (Hb) isoform expression was examined in 23 species. Isoform multiplicity declined with habitat depth, supporting the hypothesis that higher multiplicity may be associated with greater environmental variability. A lack of phylogenetic signal in Hb expression, and latitudinal variation in the relative isoform abundance in some species, indicated potential selection on this trait. However, there was no pattern in expression of cathodal Hbs, and the trait utility of this multiplicity is unknown. Overall, there is strong evidence that differences between intertidal and subtidal environments in exposure to high temperatures and hypoxia may have lead to divergence in O2 crit and mitochondrial function between intertidal and subtidal species. Therefore physiological adaptation may have enabled the expansion of species into the more demanding habitats such as the intertidal zone. Hb isoform multiplicity and VO2 were correlated with habitat in both intertidal and subtidal species, however the trait utility associated with these correlations is unknown and thus there remains a lack of evidence to support a direct role of physiological adaptation in habitat divergence of subtidal species - and therefore for adaptive radiation of the group as a whole.Whole document restricted until September 2011, but available by request, use the feedback form to request access. Please note some figures of the thesis have been previously published and are subject to copyright restrictions.
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Pescheck, Frauke [Verfasser]. "Adaptation to ultraviolet radiation in marine green macroalgae : screening and tolerance / Frauke Pescheck." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1153768453/34.
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Sinquin, Jean-Christophe. "Analyse de surface d'onde infrarouge par modulateur acousto-optique." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37618580c.
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Vilela, Reíssa Alves. "Efeito do ambiente térmico na fisiologia adaptativa de bubalinos." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/74/74131/tde-05042013-153125/.
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O objetivo do estudo foi a avaliação dos mecanismos termorreguladores, baseada numa abordagem temporal em função de diferentes armazenamentos de calor, proporcionados por diferentes tipos de ambientes térmicos (com e sem radiação solar). Foram utilizadas 12 búfalas da raça Mediterrânea que foram submetidas a quatro experimentos durante o verão de 2010 a 2012 delineados para o comprimento dos objetivos específicos. Nos vários experimentos os parâmetros meteorológicos registrados foram: temperatura de bulbo seco, temperatura de bulbo úmido, umidade relativa do ar, velocidade do vento e temperatura de globo negro. Os parâmetros fisiológicos avaliados foram: temperatura retal, temperatura da base da cauda, temperatura da epiderme, temperatura de superfície do pelame, frequência respiratória e taxa de sudação. As análises estatísticas foram realizadas com auxílio do programa Statistical Analysis System, versão 9.1.3 (SAS Institute Inc., Cary, NC, USA), utilizando-se os procedimentos PROC MIXED. No experimento 1 que visou verificar as reações termorreguladoras ao ambiente aquecido em unidade biometeorológica, o aumento da temperatura do ar em ambiente controlado influenciou todas as variáveis fisiológicas ao longo do dia (P<0,01). O incremento na taxa de sudação durante o período de estresse térmico determinou a depleção na concentração plasmática de potássio (P=0,0051). No experimento 2que avaliou as reações termorreguladoras na presença de radiação solar direta averiguamos que houve influência da exposição ao sol sobre todas as variáveis fisiológicas ao longo do dia (P<0,01). O gradiente térmico favorável no período noturno atenuou os efeitos do estresse térmico não constatando o efeito da exposição a radiação solar direta sobre os constituintes sanguíneos. No experimento 3que objetivou quantificar a velocidade de aquisição de calor ao sol comparando-a posteriormente com a velocidade de dissipação do calor à sombra, constatamos que a exposição por uma hora ao sol incrementou a frequência respiratória em 189,24 % e a temperatura retal em 1,46 %, após o retorno a sombra, por uma hora, verificamos uma redução de 191,75 % e 0,57 %, respectivamente. No experimento 4avaliamos a dinâmica da termólise evaporativa e o balanço térmico de radiação e convecção em condições de radiação solar direta. À medida que reduz a temperatura radiante média, os animais passam a perder o calor armazenado por radiação, reduzem as perdas por polipnéia térmica ao passo que as perdas por sudação permanecem altas.The aim of the study was to evaluate the thermoregulatory mechanisms, based on a temporal approach, in relation to different heat storages provided by different types of thermal environments (with and without solar radiation). Twelve Mediterranean buffalo heifers were submitted to four experiments during the summer of 2010 to 2012 outlined to achieve specific objectives. Environmental parameters dry bulb temperature; wet bulb temperature; relative humidity; winds speed and black globe temperature were measured. Physiological parameters rectal temperature; base of tail temperature; skin temperature; hair coat surface temperature; respiratory rate and sweating rate were measured. The statistical analysis were done with the assistance of the Statistical Analysis System, version9.1.3(SAS Institute Inc., Cary, NC, USA), using procedures UNIVARIATE,CORR, GLM and MIXED. The first experiment aimed to verify the thermoregulatory reactions of the warm environment in the climatic chamber. Increasing the air temperature in a controlled environment influenced all physiological variables throughout the day (P<0,01). The increase in the sweating rate during heat stress led to the depletion of plasma potassium (P=0,0051). In experiment 2, which assessed the thermoregulatory reactions in the presence of direct solar radiation, it was observed the influence of sun exposure on all physiological variables throughout the day (P<0.01). The favorable thermal gradient at night attenuated the effects of heat stress without identifying the effect of direct sun exposure on blood constituents. In experiment 3, that aimed to measure the heat acquisition rate under the sun subsequently comparing it with the speed of heat dissipation under the shade, it was observed that one hour exposure to the sun increased respiratory rate at 189,24 % and rectal temperature at 1,46 %. After returning the shade for one hour, it was found reductions of 191,75 % and 0,57 %, respectively. The Experiment 4 evaluated the dynamics of evaporative thermolysis and thermal balance of radiation and convection under conditions of direct solar radiation. Reducing the mean radiant temperature, the animals started to lose the stored heat by radiation, reduced losses by thermal polipneia while the losses by sweating remain high.
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MacLean, Roderick Craig. "Adaptive radiation and the evolution of resource specialization in experimental populations of Pseudomonas fluorescens." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85576.
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Understanding the origins of biological diversity is a fundamental goal of evolutionary biology. A large body of theory attributes ecological and genetic diversification to divergent natural selection for resource specialization. This thesis examines adaptive radiation in response to selection for resource specialization in microcosm populations of the asexual bacterium Pseudomonas fluorescens. The general protocol for these experiments is to introduce a clonal population of Pseudomonas into a novel environment and to allow evolution to occur through the spontaneous appearance of novel genotypes carrying beneficial mutations. Adaptation can then be quantified through direct comparisons between evolved populations and their clonal ancestors. These experiments show that resource heterogeneity generates divergent natural selection for specialization on alternative resources, irrespective of the spatial structure of the environment. Adaptive radiation is possible in sympatry because of genetic trade-offs in the ability to exploit different resources, but these trade-offs are often not the result of antagonistic pleiotropy among loci that determine fitness on alternative resources. The rate of phenotypic diversification declines during adaptive radiation, apparently because the ecological opportunities required to support specialist lineages disappear as a consequence of initial diversification. The ultimate outcome of repeated instances of adaptive radiation is the evolution of a community of ecologically equivalent specialists that share similar adaptive traits, despite differences in the underlying genetic basis of specialization in replicate radiations. Comparisons with the literature on experimental evolution in microbial populations illustrate the results of this thesis are well-supported by experiments in a wide range of microbial microcosms.
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DeRuvo, Sharon Lynn Speidel 1956. "Nursing diagnoses using Roy's Adaptation Model for persons with cancer receiving external beam radiation therapy." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278123.
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The purpose of this secondary analysis was to identify and describe the nursing diagnoses and associated defining characteristics for outpatient radiation therapy clients with either head and neck cancer (n = 15) or digestive organs cancer (n = 15). Based on patients' self-reported symptoms, a series of three panels clustered defining characteristics with adaptive modes, next formulated nursing diagnoses based on those characteristics, and lastly validated the compiled list of nursing diagnoses, defining characteristics, and adaptive modes. The findings of 28 nursing diagnoses generated for head and neck cancer and 25 diagnoses for digestive organs cancer indicated that radiation clients experience a gamut of patient care needs which require nursing management. Results of the comparison between the original study using Gordon's Functional Health Patterns and this one using Roy's Adaptation Model as the conceptual framework suggest that a universal set of nursing diagnoses exist for the cancer client experiencing external beam radiation therapy.
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Vijverberg, Catharina Adriana. "Adaptive radiation of Australian and New Zealand Microseris (Asteraceae) a case study based on molecular and morphological markers /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2001. http://dare.uva.nl/document/57719.
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Lettieri, Liliana B. "The evolution of cleaning mutualism and predator cooperation in a radiation of Caribbean fishes." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34690.
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The steps by which neutral, random and/or negative biological interactions evolve into mutualistic ones remain poorly understood. Here, we study Elacatinus gobies and the fishes from which they clean parasites, termed 'clients'. Colorful stripes are common to mutualist cleaners and non-cleaning sister species. Blue stripes are unique to obligate cleaners. We quantified the contrast potential of ancestral and novel stripe colors, using fish color vision models, and determined that color stripes have become more visible to clients over evolutionary time. In turn, we focused on the role of color as a potentially specialized signal. We show that cleaners possess a putative chemical defense (one multimedia file in .mov format included) and demonstrate that stripes are sufficient to elicit client stereotypical posing behavior and to deter attack. Analysis of previously published records show that yellow cleaners tend to predators less than expected, compared to green and blue cleaners. Our results highlight evolution from predator avoidance to tolerance with conspicuous advertising reinforced by chemical defense in cleaners. Similar trajectories, via recognizable signals to risky partners, may be common in other diffuse mutualisms. We discuss the generality of defense and signal traits in other species rich lineages of mutualists.
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Grosset, Lucas. "Observations extragalactiques avec optique adaptative : polarisation dans les noyaux actifs de Galaxie et étude des super amas d'étoiles." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEO004/document.
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Malgré l’existence de modèles précis, notre connaissance des structures à petite échelle des galaxies est toujours limitée par le manque de preuves observationnelles. Les progrès instrumentaux ont permis d’atteindre une haute résolution angulaire à l’aide des nouvelles générations de télescopes, mais celle-ci est restreinte à un faible nombre de cibles extragalactiques à causes des besoins de l’Optique Adaptative (OA). En effet, afin de permettre une mesure efficace du front d’onde, l’OA requiert une source brillante et ponctuelle proche de la cible scientifique, typiquement en dessous de 30 . La partie principale de cette thèse porte sur l’analyse de la dizaine de parsecs centrale des Galaxies à Noyaux Actifs (NAG) à l’aide de différentes techniques observationnelles et numériques. Nous avons dans ce contexte développé un code de transfert radiatif nous permettant d’analyser les données polarimétriques. La seconde partie de ce travail est dédiée à l’analyse d’images en proche infrarouges de galaxies à flambée d’étoiles afin de contraindre les paramètres décrivant les super amas stellaires, jeunes cocons de poussière très massifs abritant une formation d’étoiles très soutenue, à l’aide de données obtenues avec l’instrument CANARY, démonstrateur de nouvelles technologies d’OADespite having strong theoretical models, the current limitation in our understanding of the small-scale structures of galaxies is linked to the lack of observational evidences. Many powerful telescopes and instruments have been developed in the last decades, however one of these strongest tools, namely Adaptive Optics (AO), can only be used on a very limited number of targets. Indeed, for AO to be efficient, a bright star is required close to the scientific target, typically under 30 . This is mandatory for the AO systems to be able to measure the atmospheric turbulence and this condition is rarely satisfied for extended extragalactic targets such as galaxies. The main part of this thesis work consisted in going deeper in the analysis of the inner tens of parsecs of Active Nuclei (AGN) by combining different techniques to obtain and to interpret new data. In this context, we developed a new radiative transfer code to analyse the polarimetric data. A second part of my work was dedicated to a high angular resolution study of Super Star Clusters (SSC) in a new system, thanks to data obtained with the AO demonstrator CANARY instrument
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SIGNORATO, RICCARDO. "Optiques réflectives pour les lignes de lumière ESRF en mode actif/adaptatif." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10302.
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Apres l'avenement des machines dites de troisieme generation (esrf, aps, spring-8, elettra. . . ) le defi principal pour l'optique en reflexion est la conservation de la tres faible emittance du faisceau x. Cette these presente le developpement de plusieurs types de miroirs concus pour maitriser les contraintes techniques imposees par la necessite de ne pas degrader la qualite optique des faisceaux x. On a particulierement soigne : (i) la possibilite de varier le rayon de courbure (miroirs actifs) et (ii) la precision dans l'obtention de profils spheriques ou aspheriques pour les surfaces reflechissantes. Cette these se compose de cinq chapitres. Le premier consiste en une breve introduction aux sources de rayonnement synchrotron, principalement les onduleurs. Le chapitre deux traite des aspects theoriques, analytiques de l'optique x en reflexion et presente la methode numerique du trace de rayons, souvent utilisee pour etudier l'optique d'une ligne de lumiere. Une procedure permettant de tenir compte des profils reels mesures des miroirs x dans les simulations numeriques, a ete developpee et mise au point. Le chapitre trois est dedie a un dispositif a deux miroirs focalisant dans le plan vertical. L'instrument a ete caracterise optiquement et mis en service sous faisceau x. Le chapitre quatre decrit l'etude de l'optique reflective et de sa mecanique pour une ligne de lumiere dediee a la spectroscopie x. Les instruments ont ete specifies, fabriques et sont maintenant testes in-situ. Le dernier chapitre est dedie a la partie la plus originale de mon travail de recherche : un type nouveau de longs miroirs (entre 0. 5 et 1 m) segmentes a courbure variable, bases sur l'effet piezo-electrique direct. Deux prototypes ont ete concus, fabriques et experimentes avec succes dans le laboratoire de metrologie optique, montrant un potentiel prometteur concernant la compensation adaptative.
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Andersson, Emma. "Adaptive trait utility in the feeding apparatus of European whitefish (Coregonus lavaretus) : Relationships between feeding morphology and maximum and minimum prey size in the diet of whitefish." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-104986.
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Whitefish (Coregonus lavaretus) populations diverge into morphs that differ in body size along a benthic-limnetic axis and throughout the depth of the water column. This process is assumedly initiated by the presence of northern pike (Esox lucius) and is followed by morphological adaptations to available food resources. In this study eight populations of whitefish was studied with the purpose of increasing the knowledge about adaptive trait utility in the feeding apparatus of whitefish. This was done by analyzing the mean and absolute maximum and minimum prey size ingested by fish along four morphological trait gradients. The morphological traits was body size, gill raker number and density, and gape size. The results show clear evidence of morphological adaptations in both the benthic and limnetic habitat, furthermore, when comparing the two prey size responses (mean and absolute values) it becomes clear that none of the studied whitefish is physically constrained in terms of the largest prey they can ingest. However, large fish seem to be limited in eating small prey sizes. Interestingly, I also found strong indicators for filter feeding adaptation for one of the studied populations.
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Kautt, Andreas F. [Verfasser]. "Genome-wide Patterns of Adaptation and Speciation and Demographic Histories of Young Radiations of Cichlids / Andreas F. Kautt." Konstanz : Bibliothek der Universität Konstanz, 2016. http://d-nb.info/1156533872/34.
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Souza, José Eduardo Pereira. "Proposta de filtragem adaptativa de pulsos transientes para proteção de circuitos integrados sob efeito da radiação." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/99334.
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Esta dissertação propõe a utilização da técnica de filtragem adaptativa de pulsos transientes de modo a proteger os circuitos integrados sob efeito da radiação ionizante. Para garantir o uso desta técnica é necessária a utilização de um flip-flop tolerante à radiação que possua a capacidade de ter um ajuste de atraso configurável. O objetivo do uso do flip-flop programável é ter a opção de selecionar o atraso mais apropriado para filtragem temporal de pulsos de SET para cada circuito. Sendo assim, cada flip-flop pode filtrar SETs pelo uso de diferentes atrasos, baseado no atraso de propagação de cada caminho lógico. A variação nos atrasos de propagação entre múltiplos caminhos combinacionais pode ser usada para aumentar ou reduzir o atraso da filtragem de SET. Esta abordagem foi validada com o estudo de caso através de simulação elétrica e pela injeção de milhares de pulsos de SET com diferentes larguras em um circuito com filtragem adaptativa de pulsos tolerantes, os quais foram injetados de forma randômica no circuito. Os resultados mostraram o uso eficiente desta técnica de filtragem de SET em circuitos integrados. De modo a maximizar os resultados, um novo elemento de atraso programável foi desenvolvido e inserido no flip-flop. Para validação deste novo elemento, um segundo estudo de caso, utilizando o conjunto de circuitos dos benchmarks do ISCAS'85 foi também avaliado com a injeção de falhas. Os resultados mostraram que o uso do método proposto, reduz o número de erros sem perda de desempenho e com baixo incremento de área.This dissertation proposes the use of an adaptive filtering technique of transient pulses in order to protect the integrated circuit under the effect of radiation. To ensure this technique it is necessary to use a tolerant radiation flip-flop having the ability to have a configurable delay adjustment. The purpose of the use a programmable radiation hardened flip-flop is having option of to select the most appropriate delay in the SET temporal filtering for each flip-flop in a circuit. Thus, each flip-flop can filter SETs by using different delays based on the propagation-delay of its logical path. The propagation-delay variances among multiple paths can be used to increase or reduce the delay of the SET filtering. This approach was validated in a case-study by electrical simulation with injection of thousands of SET pulses of different widths, which were randomly injected in a circuit with adaptive filtering technique and the results showed efficient use of this SET filtering technique in integrated circuits. In order to maximize the results of this technique a new programmable delay element was developed and inserted into the flip-flop. This approach of the new element was validated in a second case-study, using a set of benchmark circuits from ISCAS’85 was also evaluated by injecting faults. Results showed that using the proposed method, the number of errors can be reduced without decreasing the performance and with low area overhead.
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Agogué, Hélène. "Diversité des bactéries de la microcouche de surface de l'eau de mer : spécificité, adaptation et résistance aux radiations solaires." Lyon 1, 2004. http://www.theses.fr/2004LYO10085.
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La microcouche de surface est souvent enrichie en matières organiques d'origine naturelle et anthropique. La densité de microorganismes, qui constituent le bactérioneuston, est souvent très supérieure à celle trouvée dans la colonne d'eau. Des échantillons de microcouche de surface et d'eau sous-jacente ont été collectés pour isoler et analyser la diversité des bactéries cultivables. Le séquençage de l'ADNr 16S a révélé une grande diversité parmi les bactéries isolées de la microcouche. Parmi les souches isolées, certaines étaient très éloignées taxonomiquement d'espèces connues. Une majorité des souches a présenté une résistance importante face aux radiations solaires et ceci quelque soit leur localisation dans la colonne d'eau. L'ensemble des données obtenues nous a apporté des informations concernant la diversité et les stratégies d'adaptation du bactérioneuston à l'environnement particulier de la microcouche de surface
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Schmid, Quentin. "Modélisation du rayonnement thermique en immersion de volume." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM086/document.
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Dans le cadre des procédés de chauffage et de trempe réalisés lors d’opération de mise en forme des matériaux, le rayonnement thermique joue un rôle prépondérant. Lors de l’élaboration de modèles numériques permettant la simulation de ces procédés, il est donc nécessaire de disposer d’outils performants pour simuler ce phénomène.La simulation numérique de tels procédés soulèvent de nombreuses problématiques, comme la représentation d’un environnement complexe impliquant plusieurs composants (pièces, bruleurs, buses d’injection, parois), la gestion des divers phénomènes physiques couplés (écoulement, transfert thermiques, ébullition, rayonnement). Dans cette perspective, les méthodes dites « d’immersion », permettant un traitement généraliste de ces divers problèmes, rencontrent depuis quelques années un intérêt grandissant dans la communauté scientifique.C’est dans ce contexte que s’inscrit le projet Thost, au sein duquel est réalisée cette thèse. L’objectif est donc de développer des outils pour la modélisation du rayonnement dans le contexte d’immersion de volume propre au logiciel Thost. Deux approches sont développées : l’une consistant en l’adaptation d’une méthode existante au contexte de l’immersion de volume, l’autre explorant l’élaboration d’une formulation pour un modèle particulier de rayonnement. Les outils développés sont ensuite mis à l’épreuve sur des simulations de cas industriels fournis par nos partenairesFor heating and quenching operations occurring during material forming processes, thermal radiation is the the predominant physical phenomenon. Hence, when one tries to simulate such processes, it is important to have at disposal powerful tools for the numerical modelling of thermal radiation.The numerical simulation of these processes often rises numerous problems and questions, as the representation of a complex environment, involving several components ( ingots, burners, nozzles, walls), to deal with different coupled physical phenomena ( flow, heat transfer, boiling, thermal radiation). In this regard, some “immersed” numerical methods, allows a generalist treatment of these different problems, have gained popularity and drag interest of the scientific community in the recent years.The Thost project, aiming to produce a software for heat transfer during material forming processes, fits in the framework, and this PhD is part of this project. The goal is therefore to design tools for numerical modelling of thermal radiation within the immersed volume method of the Thost software. Two approaches are presented: one consisting in the adaptation of an existing method to the context of the immersed volume method, another concerning the development of a formulation for a specific model of radiation. These methods are then tested on industrial applications provided by our partners
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Braunschweig, Suzanne Hill. "The acclimation ability of the shale barren endemic Eriogonum alleni to light and heat." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40037.
Full textAbstract:
Shale barrens are unique habitats located throughout the southern Appalachians. They are characterized by a south or south west aspect, a steep slope, and an exposed rocky surface (Platt, 1951). They have a high total irradiance and can
experience temperatures higher than the surrounding deciduous forest.
A variety of plant species, several of which are rare or endangered, are endemic to the shale barren habitat. One reason proposed fc)r their endemism is that the plants are obligate heliophyt:es (Keener, 1983). The purpose of this dissertation is tel examine the acclimation ability of the shale barren endemic Eriogonum alIeni to shade and high temperature.Ph. D.
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Teselkin, Oleksiy. "Repeatability of the Adaptation of Pseudomonas fluorescens to Low Glucose." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30986.
Full textAbstract:
Inspired by Gould, who claimed life would be arriving at a different outcome each time it were allowed to run from the same beginning, I have attempted to determine the repeatability of the adaptive course of one Pseudomonas fluorescens lineage. In addition, my study aimed to establish whether the likelihood of parallel evolution of the two synonymous single-nucleotide substitutions was contingent upon a prior motility-impairing deletion or a prior increase in fitness. Further, the study was designed to provide empirical data addressing the long-standing question of the effect of starting fitness on the ensuing rate of adaptation.
Although no exact replay of the initial evolutionary trajectory was observed, I have demonstrated that gtsB, but not gtsC gene, is likely to be a mutational hotspot under the low glucose with a recovery of two undescribed mutations in gtsB. My data are consistent with a notion that substitutions in gtsB may be contingent upon Δ35kB(fliJ-PFLU4466) motility-impairing deletion, but not the fitness increase associated with it.
Finally, the features of the adaptive landscape of P. fluorescens in the minimal glucose provide languid support for Fisher’s hypothesis of a decrease in adaptation rate with the rise in the starting fitness.
Taken together, these original results reinforce the non-negligible role of history in shaping the outcomes of biological evolution and call for caution in attempting a formulation of rigid predictive models of evolutionary change.
Inspiré par les travaux de Stephen J. Gould qui affirmait que la vie sur terre arriverait à une forme différente si elle repartait à zéro, je présente ici mes travaux où je teste la reproductibilité du cours adaptatif d’une lignée expérimentale de Pseudomonas fluorescens. L’objectif de cette étude était de déterminer si la probabilité que deux mutations synonymes évoluent en parallèle est affectée par la présence d’une délétion affectant la motilité de la bactérie ou de l’augmentation de la valeur sélective de celle-ci. De plus, le design expérimental de cette étude permet de tester si la valeur sélective initiale d’une population affecte le taux d’adaptation de cette même population.
Bien d’une reproductibilité exacte du cours adaptatif initial ne fut pas observée, je démontre que le gène gtsB est probablement un « hotspot »mutationnel permettant l’adaptation à de bas niveau de glucose, ayant trouvé deux mutations dans ce site; alors que le gène gtsC ne l’est pas. Mes données sont également conséquentes avec le fait que les mutation dans le gène gtsB dépendent de l’effet de la délétion Δ35kB(fliJ-PFLU4466) affectant la motilité de la bactérie, mais non de l’augmentation de la valeur sélective qui y est associée. Finalement, la forme du plateau adaptative associé à de bas niveaux de glucose chez P. fluorescens supporte l’hypothèse émise par Fisher qui stipule que le taux d’adaptation d’un organisme diminue avec la valeur sélective initiale qui y est associée.
L’ensemble de ces résultats supporte le rôle non-négligeable de l’histoire de vie d’une population en ce qui attrait à l’évolution future de cette même population. Aussi, ces résultats appelle à la prudence quand vient le temps de formuler des modèles prédictifs des changements évolutifs d’une population.
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Soulard, Chantal. "Description du caryotype de cinq espèces de Tellinacea, Mollusques, Bivalves : comparaisons interspécifiques et étude des relations entre les données chromosomiques et les principales radiations adaptatives dans la superfamille des Tellinacea et dans la classe des Bivalves." Bordeaux 1, 1990. http://www.theses.fr/1990BOR10515.
Full textAbstract:
Les nombres diploides de chromosomes de cinq especes de bivalves: donax trunculus scrobicularia plana, abra ovata, tellina tenuis et macoma balthica appartenant a la superfamille des tellinacea ont ete determines apres adaptations specifiques de la technique des suspensions afin d'obtenir des metaphases ou les chromosomes sont distincts et exploitables. A partir des mesures des bras chromosomiques et le calcul de trois parametres: rapport des bras, longueur absolue et longueur relative, caracteristiques des paires de chromosomes, une etude morphometrique suivie par une analyse statistique ont permis de decrire de facon precise les morphologies chromosomiques. Les caryotypes presentent un nombre diploide 2n. =. 38 chromosomes. Les morphologies different entre les especes par la repartition dans les quatre categories basees sur la position du centromere et par la repartition des longueurs relatives. Tellina tenuis est l'espece la plus telocentrique tandis que les quatre autres sont plus metacentriques. Des comparaisons interspecifiques montrent des analogies ou des differences des caracteres caryologiques. Ces donnees sont ensuite comparees avec des etudes phylogenetiques chez les tellinacea. Ayant rassemble les donnees cytogenetiques disponibles pour l'ensemble de la classe des bivalves et en s'appuyant sur les principales radiations adaptatives determinees par l'analyse de l'ethologie alimentaire, des hypotheses ont ete formulees sur la composition du caryotype ancestral chez les bivalves et les mecanismes eventuels d'evolution du nombre et de la morphologie chromosomique
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Gazave, Julien. "Contribution à la mise en œuvre de moyens de simulation numérique pour l’étude de la vulnérabilité des systèmes électriques soumis à l’environnement radiatif et électromagnétique du Laser Mégajoule." Limoges, 2007. https://aurore.unilim.fr/theses/nxfile/default/26195fe5-1740-4532-a7b9-e1658e3c2248/blobholder:0/2007LIMO4045.pdf.
Full textAbstract:
Les expériences de fusion par confinement inertiel qui seront réalisées dans l’enceinte de la chambre d’expériences du Laser Mégajoule (LMJ) engendreront une ambiance radiative et électromagnétique à laquelle seront sensibles tous les équipements électriques situés à proximité. La première partie du travail a été de mettre en oeuvre une démarche de simulation numérique permettant d’évaluer l’intensité des signaux parasites qui seront induits dans les câbles coaxiaux, puis de la confronter à l’expérience. La seconde partie a consisté à évaluer la possibilité de modélisation numérique d’une grande structure 3D, telle que la chambre d’expérience du LMJ, en électromagnétisme transitoire par la méthode FDTD. Ce type de modélisation nécessitant des ressources informatiques trop importantes pour la méthode FDTD classique, on propose l’utilisation d’un algorithme de raffinement de maillage spatio-temporel stable pour la FDTD en 3D ainsi que la réalisation de calculs massivement parallèlesWhen fusion ignition will be attained inside the target chambers of high energy laser facilities (LMJ-France and NIF-USA), a harsh environment, composed of nuclear particles and an electromagnetic pulse (EMP) will be induced. All electronic devices located in the vicinity will be sensitive to this environment. In the first part of this work, a simulation method has been developed to evaluate transient currents that will be induced in coaxial cables. The relevance of this model is then discussed thanks to comparisons with experimental results. In a second part, the possibility to simulate the propagation of the EMP, inside and outside such a big structure as a target chamber, using the FDTD method is evaluated. The use of a classic FDTD method is impossible for this kind of simulation because of the huge computer resources needs. It is the reason why a 3D space-time subgridding method for FDTD has been developed and some massively parallel FDTD calculations have also been performed
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Levy, Antonin. "Impact of microbiota on intestinal stem cells survival after irradiation." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC321.
Full textAbstract:
L'épithélium intestinal est un tissu à renouvellement rapide impliquant l’activité de cellules souches intestinales (CSIs) identifiées par le marqueur LGR5. L'épithélium intestinal doit faire face à des agressions continues en relation avec ses fonctions digestives et de barrière. Le microbiote intestinal, y compris les agents pathogènes et les bactéries commensales, influence l'intégrité et la physiologie de l'épithélium intestinal. L'interaction des molécules dérivées du microbiote avec les récepteurs immunitaires innés de l'hôte est nécessaire à l'homéostasie intestinale et son rôle est encore plus important dans des conditions de stress, en particulier celles induisant un fort stress oxydatif. Les CSIs LGR5+ expriment le récepteur immunitaire inné cytosolique NOD2. Le ligand de NOD2, le muramyl-dipeptide (MDP), un motif du peptidoglycane commun à toutes les bactéries, favorise la survie des CSIs suite à un stress oxydatif, autrement mortel. Cependant, les mécanismes de protection sous-jacents demeurent encore inconnus. L'exposition de souris axéniques ou conventionnelles aux rayonnements ionisants conduit à différents résultats. Cependant, les mécanismes conférant la radiorésistance des souris axéniques sont mal compris. Des données préliminaires de notre groupe ont indiqué que les CSIs axéniques sont résistantes aux dommages induits par la chimiothérapie, suggérant que le microbiote pourrait être impliqué dans l'initiation de la sensibilité des CSIs aux agents générant un stress oxydatif. Afin de caractériser l'interaction microbiote-CSIs après irradiation ionisante, nous avons utilisé des modèles murins in vivo et in vitro (culture d’organoïde intestinaux). Nous avons constaté qu’après irradiation in vitro (i) la transcription de Nod2 était augmentée dans les CSIs et (ii) que le MDP favorisait spécifiquement la protection des CSIs. Nous avons ensuite montré que l'addition du MDP induisait une forte diminution des espèces réactives de l’oxygène (ROS) totales et mitochondriales au sein des CSIs après irradiation. Les CSIs LGR5+ présentent une activité mitochondriale élevée et les mitochondries sont une source majeure de ROS. Nous avons démontré que la mitophagie intrinsèque aux CSIs, un mécanisme important pour l’homéostasie, est activée par le MDP, ce qui suggère un rôle pour son récepteur NOD2. De plus, les organoïdes dépourvus d’une protéine impliquée dans l’autophagie (ATG16L1 KO) ne bénéficiaient pas de la protection du MDP après irradiation in vitro. La cytoprotection médiée par le MDP a cependant pu être restaurée dans le contexte ATG16L1 KO en ajoutant un agent antioxydant. Nous avons également confirmé des défauts dans le processus de mitophagie chez les organoides de souris NOD2 KO. Ces résultats permettent une meilleure compréhension des mécanismes de cytoprotection induits par le MDP et soulignent les liens entre NOD2 et autophagie.Nous avons également démontré la radiorésistance relative des cryptes des souris axéniques, comparativement aux souris témoins in vivo. De plus, les organoides de souris axéniques conservaient leur résistance relative aux rayonnements ionisants par rapport aux organoides de souris conventionnelles. Le niveau basal de ROS était plus faible dans les CSIs des animaux axéniques par rapport aux souris conventionnelles. Nous avons particulièrement montré que l'expression de la sous-unité NADPH oxydase 1 (Nox1) est régulée par le microbiote au sein des CSIs. Par conséquent, l'activation de récepteurs de reconnaissance de motifs moléculaires (PRR) est impliquée dans l’activation de Nox1 par le microbiote.Nos données suggèrent que le microbiote joue un double rôle sur les CSIs: il régule la machinerie ROS, permettant par exemple aux CSIs de répondre aux agents pathogènes et exerce un effet cytoprotecteur après une agressionThe intestinal epithelium is a fast self-renewing tissue implicating an active intestinal stem cells (ISCs) pool uniquely identified by the LGR5 marker. The gut epithelium needs to cope with continuous stressors in relation with its digestive and barrier functions. The gut microbiota, including pathogens and commensal bacteria, influences the integrity and physiology of the gut epithelium. The interaction of microbiota-derived molecules with host innate immune receptors is required for gut homeostasis and its role is even more important upon stress conditions, particularly those inducing strong oxidative stress. LGR5+ ISCs express the cytosolic innate immune sensor NOD2. The NOD2 ligand muramyl-dipeptide (MDP), a peptidoglycan motif common to all bacteria, promotes ISCs survival over an otherwise lethal oxidative stress-mediated signal. Yet, the underlying protective mechanisms remained unknown. Exposure of axenic or conventional mice to ionizing radiation leads to different outcomes. Axenic animals display less radiation enteritis than their conventional counterparts. However, the mechanisms conferring radioresistance to axenic mice are poorly understood. Preliminary data from our group indicated that axenic-ISCs are resistant to chemotherapy-induced damages, suggesting that the microbiota might be involved in initiating the sensitivity of ISCs to oxidative-stress generating agents.To characterize the microbiota-ISCs interaction after ionizing radiation, we used both in vivo and in vitro (mini-gut organoid culture) mice models. We found that, following irradiation in vitro, (i) Nod2 transcription was increased in ISCs and (ii) MDP specifically promoted ISCs protection. We then showed that the addition of MDP induced a strong reduction of total and mitochondrial reactive oxygen species (ROS) within ISCs after irradiation. LGR5+ ISCs display high mitochondrial activity and mitochondria are the richest source of ROS. We demonstrated that ISCs-intrinsic mitophagy, an important mechanism for ISCs homeostasis, is activated by MDP, suggesting a role for its receptor NOD2. Moreover, organoids lacking autophagy protein 16 (ATG16L1 KO) did not benefit from MDP cytoprotection following irradiation in vitro. MDP-mediated cytoprotection, however, could be restored in the ATG16L1 KO context by adding a ROS-scavenging agent. We also confirmed defects in the mitophagy process in organoids from NOD2 KO mice. These findings elucidate the mechanisms of cytoprotection induced by MDP and highlight the NOD2-autophagy links. We also showed the relative radioresistance of crypts in axenic animals, compared to control mice in vivo. Additionally, organoids from axenic mice were relatively resistant to ionizing radiation in comparison with organoids from conventional mice. On the other hand, organoids from conventionalized mice (axenic mice displaced in conventional animal facilities) and antibiotic-treated mice were not relatively radioresistant. Basal level of ROS in the gut epithelium was reduced in axenic animals. We confirmed transcriptional differences in the activation of the ROS-producing machinery in ISCs from axenic mice (at basal level and after irradiation), as compared to control mice. We particularly showed that expression of the NADPH oxidase 1 subunit (Nox1) is regulated by the microbiota within ISCs. Hence, specific pattern recognition receptors activation is implicated in Nox1 priming by the microbiota.Our data suggest that the microbiota plays a dual role on ISCs: it regulates the ROS machinery, for instance allowing ISCs to respond to pathogens and it exerts a cytoprotective effect after aggression. These findings open the way to dissect additional molecular pathways involved in ISCs homeostasis and to new prospects for translation into clinical practice
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Souza, Laura Barreto de Paula. "Diversificação e evolução fenotípica em peixes cascudos (Siluriformes: Loricariidae: Loricariinae)." Pós-Graduação em Ecologia e Conservação, 2018. http://ri.ufs.br/jspui/handle/riufs/8003.
Full textAbstract:
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESOne of the major causes of the phylogenetic, temporal and spatial variation of species richness is attributed to the processes of differential speciation and extinction of lineages, named diversification. There is also a great phenotypic diversity among species that may be related to diversification. The development of phylogenetic comparative methods allowed the study of the diversification and evolution of species traits. The aim of this study is to investigate the pattern of diversification and trait evolution of the suckermouth armored catfish, Loricariinae subfamily, and to investigate if these attributes are related to the diversification rates within the clade. We used a phylogeny containing 114 representatives of subfamily species and their attributes body size, climatic niche and microhabitat (substrate) - position and width for both - to evaluate the evolutionary rates and test the relationship between these different axes of the species niche and their evolutionary rates. We estimated diversification rates with BAMM and performed phylogenetic correlation analyzes (STRAPP) to address the question of whether the attributes are related to the diversification process in the subfamily. We also performed analyzes of disparity through time (DTT) to explore the temporal pattern of phenotypic evolution. The diversification analysis showed that the subfamily had high rates of diversification. Body size presented heterogeneous rates among clades, presenting a shift of diversification in which the specie Paraloricaria agastor had the smallest size of the clade. Climatic niche position presented a heterogeneous pattern of diversification rates, with a shift involving six species of Rineloricaria that retained their niche position. Diversification of the climatic niche width revealed the most heterogeneous pattern, presenting four shifts occurring in clades in which some species possessed greater climatic niche widths. However, the rates of diversification of both micro-habitat position and width did not show any shift. The STRAPP test revealed no correlation between any of the traits studied with diversification, showing that evolutionary process of Loricariinae seems to be independent of the phenotypic attributes investigated. The DTT revealed that in most of the Loricariinae’s evolutionary history, the averages of disparity of the studied attributes evolved under neutral evolution, although they presented peaks of phenotypic disparity within the clades in the most recent time. The results showed that Loricarinae evolved through a non-adaptive radiation where vicariant events would have promoted allopatric speciation and the high diversification rates. In fact, it is known that the radiation of Neotropical fishes was closely related to geological processes of basin formation (hydrogeological hypothesis). DTTs analyzes reinforces this claim, because in most of the evolutionary history the attributes evolved neutrally, without association with diversification, as expected in non-adaptive radiation. Although the subfamily evolved under non-adaptive radiation, divergent selection processes possibly occurred in species independently, promoting significant disparity of attributes within the clades at the present time. The results obtained highlights a peculiar evolutionary history for Loricariinae and a unique known example of nonadaptive radiation for the Neotropics, which can be enlighten the understanding of the yet little known processes that led to the extraordinary diversification of the Neotropical fishes.
Uma das causas da variação filogenética, temporal e espacial da riqueza das espécies são atribuídas aos processos de especiação e extinção diferencial das linhagens, chamado de diversificação. Existe também uma grande diversidade fenotípica entre as espécies que pode estar relacionada à diversificação. O desenvolvimento de métodos filogenéticos comparativos permitiu o estudo da diversificação e evolução de atributos das espécies. O objetivo do presente estudo é investigar os padrões de diversificação e evolução de atributos de peixes Cascudos da subfamília Loricariinae, e investigar se esses atributos estão correlacionados com as taxas de diversificação. Foi utilizada uma filogenia contendo 114 representantes de espécies da subfamília e os atributos tamanho corporal, posição e largura de nicho climático de microhábitat (substrato), para avaliar as taxas evolutivas e relação entre esses diferentes eixos do nicho das espécies e as taxas evolutivas da subfamília. As taxas de diversificação da subfamília e dos atributos foram estimadas através do BAMM e foram realizadas análises de correlação filogenética (STRAPP) a fim de detectar se os atributos estão moldando o processo de diversificação na subfamília. Foram realizadas também análises de disparidade ao longo do tempo (DTT) para explorar o padrão temporal de evolução fenotípica. A análise de diversificação mostrou que a subfamília possui altas taxas de diversificação. O tamanho corporal apresentou taxas heterogêneas entre os subclados, apresentando um shift de diversificação no clado em que a espécie Paraloricaria agastor apresentou o menor tamanho do clado. A posição de nicho climático apresentou um padrão heterogêneo de taxas de diversificação, apresentando um shift envolvendo seis espécies de Rineloricaria que conservaram sua posição de nicho. A diversificação da largura de nicho climático revelou o padrão mais heterogêneo, apresentando quatro shifts que ocorreram em clados que contém espécies com maiores larguras de nicho climático. Já as taxas de diversificação da posição e largura de micro-hábitat não apresentaram shifts. Os testes STRAPP revelaram não haver correlação entre nenhum dos atributos considerados no presente estudo e a diversificação, mostrando que o processo evolutivo de Loricariinae parece ser independente dos atributos fenotípicos investigados. O DTT revelou que na maior parte da história evolutiva da subfamília as médias de disparidade dos atributos estudados evoluíram de forma neutra, porém apresentaram picos de disparidade fenotípica dentro dos clados no tempo mais recente. Os resultados mostram que provavelmente os Loricaríneos evoluíram através de uma radiação não adaptativa onde eventos vicariantes teriam promovido especiação alopátrica e as altas taxas de diversificação. De fato, acredita-se que a radiação dos peixes Neotropicais esteve intimamente relacionada aos processos geológicos de formação de bacias (hipótese hidrogeológica). O DTT reforça essa conclusão, pois em boa parte da história evolutiva os atributos evoluíram neutramente, sem associação com a diversificação, como seria esperado em uma radiação não adaptativa. Entretanto, apesar de a subfamília ter evoluído sob radiação não adaptativa, processos de seleção divergente possivelmente ocorreram em espécies independentemente, promovendo disparidade significativa dos atributos dentro dos clados no tempo presente. Os resultados obtidos revelam uma história evolutiva peculiar para os Loricaríneos e um exemplo raro de radiação não adaptativa nos Neotrópicos, que pode elucidar o entendimento dos processos que levaram a extraordinária diversificação dos peixes Neotropicais, ainda pouco conhecidos.
São Cristóvão, SE
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Maestri, Renan. "Evolução morfológica na radiação dos roedores sigmodontíneos : ecologia e história evolutiva." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/163695.
Full textAbstract:
Radiações evolutivas estão entre os eventos mais fascinantes da evolução. Grande parte da diversidade da vida, tanto de espécies como ecológica, surgiu nos breves intervalos temporais de rápida especiação que configuram as radiações. As causas ecológicas e não-ecológicas do surgimento da diversidade em radiações evolutivas, em especial nas radiações adaptativas, são tema de pesquisa há muito tempo, pelo menos desde que Darwin observou a imensa diversidade de um grupo de pássaros nas ilhas Galápagos. Desde então, as ilhas têm sido os ambientes ideais para o estudo desse fenômeno, e foi a partir das observações e experimentos em ilhas que toda a teoria ecológica das radiações evolutivas surgiu. Contudo, as causas ecológicas das radiações explosivas ocorridas em amplas escalas continentais permanecem tema de constante debate. Nesta tese, foram investigados os determinantes ecológicos e não-ecológicos (e.g., geografia, contingências históricas, efeitos filogenéticos) da evolução morfológica dos roedores sigmodontíneos durante sua radiação na região Neotropical, em especial no continente sul-americano. Para isso, foi quantificada a morfologia do crânio e mandíbula de mais de dois mil exemplares do grupo, e foram investigadas variações ecomorfológicas nos níveis interespecífico (I), intraespecífico (II), e entre assembleias de sigmodontíneos (III). Na Parte I da tese, foram investigadas duas predições da teoria da radiação adaptativa, a correlação-fenótipo ambiente (capítulo 1) e a funcionalidade do fenótipo através da força da mordida (capítulo 2), permitindo determinar o papel da divergência ecológica na evolução morfológica das espécies. Na Parte II (capítulo 3), foram investigadas as contribuições relativas de processos determinísticos e neutros sobre a variação morfológica entre populações de uma espécie de roedor sigmodontíneo amplamente distribuída, Akodon cursor. Na Parte III, a influência da variação ambiental e da distribuição espacial das linhagens filogenéticas de sigmodontíneos sobre o tamanho corporal (capítulo 4) e forma do crânio e mandíbula (capítulo 5), foram investigados no contexto biogeográfico da variação no tamanho e forma média entre assembleias de sigmodontíneos. As contribuições originais desta tese foram: (i) mostrar que a radiação evolutiva dos roedores sigmodontíneos foi guiada principalmente por fatores históricos e geográficos ao invés de fatores ecológicos; (ii) sugerir que radiações evolutivas ocorridas em escalas continentais, especialmente de roedores, têm um componente geográfico e histórico mais determinante do que o componente ecológico; (iii) revelar que a força da mordida varia pouco entre roedores sigmodontíneos herbívoros e granívoros, o que provavelmente é resultado do fenótipo generalista desses roedores; (iv) apontar que sigmodontíneos com dieta insetívora têm uma taxa de evolução mais rápida, e parecem estar evoluindo sua forma do crânio/mandíbula e sua força da mordida em uma direção diferente das demais espécies; (v) demonstrar que, dentro de uma espécie de sigmodontíneo (Akodon cursor), fluxo gênico e deriva genética explicam melhor a forma do crânio entre populações, enquanto a variação ambiental explica melhor o tamanho do crânio, indicando que o tamanho é uma característica mais lábil e mais sujeita a pressões ambientais do que a forma do crânio; (vi) mostrar que a variação biogeográfica, tanto do tamanho quanto da forma média do crânio/mandíbula entre assembleias de sigmodontíneos, está sob influência da distribuição diferencial das linhagens filogenéticas ao longo do espaço geográfico, bem como de variáveis ambientais; o que indica conservação filogenética de nicho à nível de metacomunidades. De modo geral, ao investigar as contribuições relativas dos componentes adaptativo e não-adaptativo da evolução morfológica, foram obtidas informações importantes para conhecer as causas da diversificação morfológica em Sigmodontinae, aumentando nosso conhecimento sobre as origens de toda a diversidade biológica.Evolutionary radiations are among the most fascinating phenomena of evolution. Most of the biological diversity on the planet, both in terms of species and ecological diversity, appeared during these brief intervals of rapid speciation. The ecological and non-ecological causes of the emergence of diversity in evolutionary radiations, especially in adaptive radiations, have long been the subject of research, beginning with Darwin and his notice of the astonishing diversity of bird forms in the Galapagos Islands. Islands have since been ideal environments in which to study evolutionary and adaptive radiations, and indeed it was from observations and experiments on islands that all ecological theory of evolutionary radiations arose. However, the ecological causes of explosive radiations occurring on large continental scales are still a matter of debate. In this dissertation, I investigated the ecological and non-ecological (e.g., geography, historical contingencies, phylogenetic effects) determinants of morphological evolution in sigmodontine rodents during their radiation in the Neotropical region, particularly on the South-American continent. The skull and mandible morphology of more than two thousand specimens was quantified, and ecomorphological variation was investigated on three levels: interspecific (I), intraspecific (II), and among sigmodontine assemblages (III). In part I, two predictions from the ecological theory of adaptive radiation were investigated: the phenotype-environment correlation (chapter 1), and the trait utility through the bite force (chapter 2). This approach enabled determination of the role of ecological divergence in species morphological evolution. In part II (chapter 3), I investigated the relative contributions of deterministic and neutral processes to morphological variation among populations of one widely distributed sigmodontine species, Akodon cursor. In part III, I investigated the influence of environmental variation and spatial distribution of phylogenetic lineages on body size (chapter 4) and on shape of the skull and mandible (chapter 5), in the context of biogeographical variation of mean size and shape in sigmodontine assemblages. The original contributions of this dissertation are as follows: (i) to demonstrate that the evolutionary radiation of sigmodontines was driven mainly by historical and geographical factors instead of ecological factors; (ii) to suggest that evolutionary radiations on continental scales, especially rodent radiations, have a more determinant historical and geographical component than an ecological one; (iii) to show small variation in bite force between sigmodontine herbivores and granivores, which is likely a consequence of the generalist phenotype of these rodents; (iv) to highlight that insectivorous sigmodontines have a faster rate of morphological evolution than other diet groups, and that skull and mandible morphology and bite force are evolving in different directions than in other species; (v) to demonstrate that within a sigmodontine species (Akodon cursor), gene flow and genetic drift better explain variation in skull shape among populations, while environmental variation better explains variation in skull size, which suggests that size is more labile feature than shape and thus more prone to change with environmental pressures; and (vi) to show that biogeographical variation in mean body size, mean skull shape, and mean mandible shape across sigmodontine assemblages is influenced by the different distributions of phylogenetic lineages over geographical space, as well by environmental variables, which indicates phylogenetic niche conservatism at the metacommunity level. These results shed light on some of the factors driving morphological diversification in Sigmodontinae. Further, the analytical approach(es) utilized may be useful for general investigations of the relative contributions of adaptive and non-adaptive components of morphological evolution, thereby potentially increasing our knowledge of the origins of all biological diversity.
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Londoño-Flórez, Beatriz Elena. "Ultracold stable ground state RbCs molecules through photoassociation below the Rb(5s)Cs(6p 1/2) dissociation limit." Paris 11, 2010. http://www.theses.fr/2010PA112263.
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Le but de cette thèse est l'exploration théorique, sur l'exemple de la molécule RbCs, de la formation par voie optique de dimères alcalins hétéronucléaires dans leur niveau d'énergie le plus bas, à partir d'atomes ultrafroids. On a analysé le spectre lié et le continuum près du seuil de dissociation des états électroniques stables X et a, ainsi que les derniers niveaux liés des états 0+,0- et 1 sous la limite de dissociation Rb(5s)Cs(6p 1/2). Une description 'universelle' des résonances de forme de molécules diatomiques montre le rôle crucial de la longueur de diffusion en onde s. Les facteurs de Franck-Condon (FCF) liés aux processus de photoassociation (PA) ou de désexcitation par émission spontanée (RS) sont calculés de façon systématique. Comme observé expérimentalement, le niveau le plus peuplé par PA suivie de RS est le niveau v=37 de l'état triplet le plus bas. Le rôle important du couplage 'résonnant' est mis en évidence. Les durées de vie des niveaux 0+ sont calculées de façon systématique. Les FCF liés au transfert de population du niveau v=37 vers l'état fondamental absolu sont calculés : le chemin par un niveau intermédiaire 0+ est le plus efficace. L'emploi de sources femtoseconde et de trains d'impulsions femtoseconde pour le transfert de population vers des niveaux très liés des états électroniques stables à été exploré en analysant, dans une approche dépendant du temps, la dynamique de l'excitation depuis le régime champ faible jusqu'au régime champ fort. La Méthode de Représentation de l'Hamiltonien sur une Grille de Fourier à pas ajusté a été étendue avec succès à l'étude de la dynamique des transitions entre niveaux liés et états de diffusionThe main goal of this thesis is to explore theoretically, on the example of the RbCs molecule, the formation, by optical means, of heteronuclear dialkali molecules in the lowest vibrational level of the ground electronic state, starting from ultracold atom pairs. The bound spectrum and the continuum close to threshold of the ground and lowest triplet electronic states are analyzed together with the levels 0+, 0- and 1 below the Rb(5s)Cs(6p 1/2) limit. A 'universal' description of the profiles of shape resonances, valid for any diatomic molecule, points out the crucial role of the s-wave scattering length. Calculations of Franck-Condon factors (FCF) relevant to photoassociation (PA) and spontaneous radiative decay (RS) are presented, showing, in agreement with experiment, that the v=37 level of the triplet electronic state is most favorably populated after PA followed by RS. The so-called 'resonant' coupling is examined in great detail, underlying its crucial influence on PA and RS. Radiative lifetimes are systematically calculated. The FCF associated with optical two-color population transfer from the triplet v=37 level toward the absolute ground level are also calculated, showing that the path through levels of 0+ symmetry is the most efficient. The possibilities offered by femtosecond sources for the population transfer toward deeply bound levels are explored and the dynamics is analyzed, from the low field up to the high field regime. Trains of femtosecond pulses are considered. The Mapped Fourier Grid Hamiltonian method, cornerstone of this study, proves its efficiency to accurately analyze the dynamics of transition processes between bound and scattering levels
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Payne, Stephanie. "Phenotypic variation and thermoregulation of the human hand." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/285561.
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The hand has the highest surface area-to-volume ratio of any body part. This property offers the potential for the hand to serve an important function in thermoregulation through radiative heat loss. Theoretically, the capacity for heat loss may be influenced by hand and digit proportions, but the extent to which these proportions influence the hand's radiative properties remains under-investigated. Although hand morphology is highly constrained by both integration and functional dexterity, phenotypic variation in hand and digit proportions across human populations shows broad ecogeographic patterns. These patterns have been associated with climate adaptation. However, the theory linking climate adaptation to such ecogeographic patterns is based on underlying assumptions relating to thermodynamic principles, which have not been tested in vivo. This study sought to determine the influence of hand and digit proportions on heat loss from the hands directly, the additional anthropometric factors that may affect this relationship, and the impact of variation in hand proportions on dexterity in the cold. The relationship between hand proportions and thermoregulation was tested through both laboratory-based investigation and a field study. The laboratory investigation assessed the relationship between hand proportions and heat loss, the influence of body size and composition on this relationship, and the effect of morphological variation on manual dexterity. Participants (N=114; 18-50 years of age), underwent a 3-minute ice-water hand-immersion. Thermal imaging analysis was used to quantify heat loss. Hand and digit proportions were quantified using 2D and 3D scanning techniques; body size and composition were measured using established anthropometric methods and bio-impedance analysis. After accounting for body size, hand width, digit-to-palm length ratio, and skeletal muscle mass were significant predictors of heat loss from the hand, whilsthand length and fat mass were not. A separate set of participants (N=40) performed a Purdue pegboard dexterity test before and after the immersion test, which demonstrated that digit width alone negatively correlated with dexterity. The field study tested whether phenotypic variation in upper limb proportions could be attributed to cold adaptation or selection for dexterity in living populations exposed to significant energetic stress. Upper limb segment lengths were obtained from participants (N=254; 18-59 years of age), from highland and lowland regions of the Nepalese Himalayas using established anthropometric methods, and relative hand proportions were assessed in relation to severe energetic stress associated with life at high altitude. Relative to height, hand length and hand width were not reduced with altitude stress, whilst ulna length was. This indicates that cold adaptation is not shaping hand proportions in this case, although phenotypic variation in other limb segments may be attributed to cold adaptation or a thrifty phenotype mechanism. The current study provides empirical evidence to support the link between surface area-to-volume ratio, thermodynamic principles and ecogeographical patterns in human hand morphology. However, this research also demonstrates the complexity of the hand's role in thermoregulation; not only do other factors such as muscularity affect heat loss from the hand, but hand morphology is also highly constrained by integration and dexterity.
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Sron, Seng thail. "Algorithmes intelligents de pilotages d'antennes reconfigurables à partir de données en bande de base pour la norme LTE." Thesis, Limoges, 2015. http://www.theses.fr/2015LIMO0138.
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Le développement des antennes modales, qui sont des antennes actives reconfigurables en diagramme de rayonnement mais pas en réseaux, a commencé pour pouvoir implémenter le dépointage électronique dans les téléphones portables. Cette solution est généralement réalisée par un réseau d’antennes, ce qui est très difficile, voire impossible, dans un téléphone portable. Le dépointage permettrait d’améliorer le bilan de liaison et d’augmenter le débit des données.Le premier objectif de cette thèse est donc de développer des antennes modales pour la norme LTE. Trois concepts d’antennes modales ont été présentés. Le premier est une antenne de type « folded loop » active reconfigurable par permutation des points d’alimentation et de retour à la masse. Le deuxième propose une architecture pour rassembler l’antenne principale et l’antenne diversité en bas du téléphone, tout en supportant le MIMO et l’agrégation de porteuses, deux des spécificités de la LTE. Le dernier optimise l’utilisation de la seconde antenne des systèmes LTE MIMO pour procéder au dépointage électronique.Ces antennes modales ne peuvent délivrer leur réel potentiel qu’en étant utilisées avec un algorithme de pilotage, qui choisira la configuration ou le mode approprié(e) à la situation. Le second objectif de cette thèse est donc le développement d’algorithmes intelligents de pilotage d’antennes modales. Le premier algorithme développé et breveté par la société Ethertronics a la particularité de prédire à chaque instant quel sera le meilleur mode à l’instant suivant, à l’aide de données en bande de base pour la LTE. Le second algorithme est déterministe et permet d’estimer et de suivre la direction d’arrivée du signal. Il sélectionne ensuite le mode qui possède le meilleur gain dans cette direction, dans le but d’améliorer le bilan de liaisonThe development of modal antennas which are radiation pattern reconfigurable active antennas, but not arrays, started in order to implement beam forming in cellphones. This solution is generally made with an antenna array, which is very difficult, even impossible, in a mobile phone. Beam forming could improve the link budget and increase the data rate. The first aim of this thesis is the development of modal antennas for LTE standard. Three modal antennas concepts were presented. The first one is a reconfigurable “folded loop” active antenna by permutation of feed and ground points. The second one is a solution to gather the main and the diversity antenna in the bottom part of the phone, and to support MIMO and carrier aggregation, which are two features of LTE. The last one optimizes the use of the second antenna in LTE MIMO systems in order to perform beam forming. These modal antennas will provide their real potential only by being used by a driving algorithm which will choose the best mode or configuration according to the situation. So, the second aim of this thesis is the development of smart modal antenna driving algorithms. The first algorithm, developed and patented by Ethertronics, has the specificity to predict, at each moment, which mode will be the best for the next moment, by using baseband data for LTE. The second algorithm is deterministic and can estimate and track the direction of arrival of the signal. Then, it selects the mode which has the best gain in this direction in order to improve the link budget
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Latry, Olivier. "Théorie des modes locaux dans les guides perturbés application : couplage fibre optique - photodiode PIN." Rouen, 1995. http://www.theses.fr/1995ROUE5001.
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La réduction des dimensions des composants optoélectroniques constitue une contrainte importante pour un couplage optimal avec la fibre optique. Le but recherché étant de focaliser le maximum de lumière à l'intérieur de la couche intrinsèque de la photodiode, il faudrait donc envisager de réduire le diamètre de la fibre optique. Une étude du bout de la fibre est également menée et montre que pour une forme lentillée appropriée, il est possible d'adapter la distribution d'énergie entre fibre optique et photodiode. Le calcul du champ le long de ce guide de dimensions lentement décroissantes utilise la méthode des modes locaux. Cette méthode est employée car il n'y a pas de solutions exactes aux équations de Maxwell. En réalité, le champ total est la superposition des champs locaux et du champ radiatif. Les pertes d'énergie le long de ce guide sont analysées avec la théorie du couplage des modes locaux. On obtient alors un bilan le long de ce guide que l'on cherche à optimiser. La comparaison de ces résultats avec la simulation numérique quasi 3 D de la propagation optique guidée sur ALCOR est également réalisée. Ceci permet de définir la structure la mieux adaptée pour un couplage optimum entre la fibre et le composant
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Kuchma, Oleksandra. "Genetic processes in Scots pine (Pinus sylvestris L.) in the Chernobyl exclusion zone." Thesis, 2010. http://hdl.handle.net/11858/00-1735-0000-0006-B145-6.
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