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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Appendage development and early distal-less regulation in arthropods : a study of the chelicerate Tetranychus urticae (Acarida)

Cyrus-Kent, Chlo January 2007 (has links)
A major goal of evolutionary developmental biology is to explore mechanisms and events underlying evolution of the myriad body plan morphologies expressed both genetically and phenotypically within the animal kingdom. Arthropods exhibit an astounding array of morphological diversity both within and between representative sub-phyla, thus providing an ideal phylum through which to address questions of body plan innovation and diversification. Major arthropod groups are recognised and defined by the distinct form and number of articulated appendages present along the antero-posterior axis of their segmented bodies. A great deal is known about the developmental genetics of limb development in the model insect Drosophila melanogaster, added to which, much comparative gene expression data and a growing body of functional genetic data is emerging for other arthropod species. Arthropod limb primordia are consistently marked by expression of the homeobox gene Distal-less (Dll), and the focus of this thesis is to compare signalling mediated by early Dll regulatory genes activity along antero-posterior and dorso-ventral embryonic axes during limb specification in Drosophila, with the activity of their orthologs in the widely disparate chelicerate, the spider mite Tetranychus urticae - interpreting new data with that available for other arthropods. Having made a detailed study of spider mite embryonic (and post-embryonic) development, to provide a basis for understanding mRNA transcription and protein activity patterns, I confirmed typical expression of Tetranychus Dll in prosomal limb primordia. I obtained limited results for the candidate antero-posterior positioning genes wingless and engrailed, although one of the two engrailed paralogs I identified is reportedly expressed in posterior segmental compartments, consistent with possible conservation of Engrailed-Wingless interactions in metameric patterning and positive regulation of Dll in arthropod limb specification. In Drosophila, wingless-dependent Dll transcription is restricted along the dorso-ventral axis by dorsal Dpp-mediated and ventral EGFR-mediated signalling gradients. Based on data from Tetranychus and other arthropods, neither dorsal nor ventral signalling regimes appear conserved outside the Drosophila system. Dll suppression in fly abdominal segments occurs due to powerful Hox (Ubx/AbdA) repression of the early Dll cis-regulatory element; this is discussed in relation to the independently evolved limbless chelicerate opisthosoma, informed by hypothetical scenarios of cis (regulatory DNA) and trans (coding sequence) evolution. Given practical difficulties and limitations encountered while working with spider mites, I offer a final assessment of the place of Tetranychus urticae as a non-model, and yet still valuable chelicerate species to consider carrying into the exciting future of evolutionary developmental biology.
82

Identification de gènes impliqués dans la variation morphologique des fleurs entre deux espèces du genre Rhytidophyllum

Poulin, Valérie 08 1900 (has links)
Les adaptations florales à des pollinisateurs comme les changements de forme de la corolle entraînent souvent un isolement reproducteur et donc la spéciation. Malgré leur importance écologique, les mécanismes génétiques à l'origine de cette diversité de caractères sont encore mal compris, surtout en dehors des espèces modèles. L’objectif de mon projet de maîtrise était donc d'identifier les gènes impliqués dans la variation de la forme de la corolle entre deux espèces du genre Rhytidophyllum (famille des Gesneriaceae), qui ont des modes de pollinisation différents. La première, R. rupincola, a des fleurs tubulaires et est strictement pollinisée par les colibris, tandis que la seconde, R. auriculatum, a des fleurs plus ouvertes et est pollinisée par les colibris et les chauves-souris. Dans cette étude, nous avons fait une revue de littérature et utilisé une approche de transcriptomique comparative pour identifier des gènes candidats qui pourraient expliquer la variation de la forme florale entre R. auriculatum et R. rupincola. Nous avons ensuite testé leur association avec la variation de la forme de la corolle en utilisant la cartographie de loci de traits quantitatifs (QTLs) pour une population hybride F2. Les résultats ont montré que 7 des 29 gènes candidats étaient associés à 8 QTLs différents. La répartition et la fonction supposée de ces gènes suggèrent que la forme de la corolle est un trait complexe. Ce type d'étude est rarement entrepris chez des espèces non-modèles, mais il est important afin d'intégrer la génétique du développement floral dans une perspective évolutive. / Floral adaptations to specific pollinators like corolla shape changes often result in reproductive isolation and thus speciation. But despite their ecological importance, the genetic mechanisms behind this diversity of traits are still poorly understood, especially outside model species. Hence, our goal is to identify genes involved in corolla shape variation between two species of the Rhytidophyllum genus (Gesneriaceae family) from the West Indies, which is characterized by shifts in pollination modes during its evolution. The first one, R. rupincola, has a tubular corolla and is strictly pollinated by hummingbirds. The second one, R. auriculatum, has more open flowers and is pollinated by both hummingbirds and bats. We know from previous work that the variation in morphological floral traits between these species is explained by a few quantitative trait loci (QTLs) of moderate to small effect (Alexandre et al., 2015), but we still do not know which genes underly these loci. In this study, we surveyed the literature and used a comparative transcriptomic approach to identify candidate genes that could explain floral variation between R. auriculatum and R. rupincola. We then tested their association with corolla shape variation using QTL mapping for a F2 hybrid population. Results showed that 7 out of 29 candidate genes were included within 8 different QTL. The number, repartition and putative function of these genes suggest that corolla shape is a complex trait. This sort of investigation is rarely undertaken in non-model species, but is important to integrate developmental genetics with an evolutionary perspective.
83

Systémové řešení pro energetické využití zdravotnických odpadů / Systematic approach for medical waste-to-energy processing

Hanus, Jan January 2019 (has links)
This master thesis deals with the current situation of medical waste management in the Czech Republic and available medical waste treatment methods. The first part summarises the legislation of waste treatment and contains an analysis of the current situation of medical waste management in the Czech Republic and comparison to the situation in the European Union. The second part describes medical waste treatment methods and following technologies for energy utilization when thermal treatment method is applied. In the main part of this thesis, a complex medical waste-to-energy system in a model region is designed according to the input data. The design includes description of the collecting and transportation system of the waste, capacity of the unit and suitable thermal treatment and heat utilization technology choice. A calculation model is created for the proposed unit and based on this model, an analysis on energy utilization effectivity is made. As a result of the thesis, environmental, technical and economical assessment is created based on the estimation of the investment and operating costs.
84

Las relaciones bilaterales de Bolivia y Estados Unidos durante el gobierno de Evo Morales: una lectura desde el constructivismo

García Ramírez, Elmer Alejandro 15 June 2018 (has links)
La presente tesis tiene como objetivo central demostrar mediante el uso del enfoque constructivista de las relaciones internacionales el factor que condujo al deterioro histórico de las relaciones diplomáticas entre Bolivia y Estados Unidos durante los gobiernos de Evo Morales Ayma. Del mismo modo, los objetivos secundarios son analizar las relaciones bilaterales entre Washington y la Paz desde 1952 hasta 2005, lo cual permite apreciar nítidamente los procesos de interacción entre estos Estados y con base en ello poder determinar cómo se crearon y moldearon las relaciones bilaterales entre ambos países. Así como también analizar las características de la política exterior implementada por el país altiplánico a partir de la administración de Evo Morales, con la finalidad de determinar las características de la nueva configuración de la identidad de Bolivia. En la presente investigación se postula que a raíz de la llegada al poder de Evo Morales la identidad de Bolivia experimentó una severa transformación. La nueva identidad adoptada por el país altiplánico se caracteriza por asumir una postura revisionista que pretende empoderar y rescatar elementos de la cultura andina boliviana, además de erigirse en contraposición a Estados Unidos. De esta manera, Washington pasó a percibir como una verdadera amenaza a La Paz. Lo cual por su parte explica el inusitado deterioro de relaciones diplomáticas entre ambas naciones.
85

Evidence for a dual origin of insect wings via cross-wiring of ancestral tergal and pleural gene regulatory networks

Deem, Kevin David 06 April 2022 (has links)
No description available.

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