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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.
1

Les bases génétiques de la pigmentation dans les embryons de punaise d'eau / Genetic Basis of Extra-Ocular Pigmentation in Semi-Aquatic Embryos

Vargas Lowman, Aidamalia 24 September 2019 (has links)
Le but de ce doctorat était de comprendre les bases génétiques de la diversification de la pigmentation extra-oculaire chez les embryons des Gerromorphes. La plupart des punaises semi-aquatiques présentent une variabilité de pattern de couleur jaune ou/et rouge dans les pattes et les antennes au stade embryonnaire. La couleur rouge observée dans les appendices étant similaire à celle présente dans les yeux, nous avons émis l'hypothèse que les couleurs extra-oculaires pouvaient être produites par la co-option des voies de synthèse des pigments des yeux. Nous avons d'abord déterminé l'histoire évolutive de ce trait à partir de sa présence ou de son absence dans les embryons de 34 espèces. Grâce à l'analyse génétique par interférence ARN et hybridation in situ, nous avons identifié les voies impliquées dans la pigmentation des yeux et des organes extra-oculaires dans l'espèce Limnogonus franciscanus. Nous avons ensuite testé par interférence ARN et hybridation in situ trois gènes de la voie ptéridine dans cinq autres espèces de Gerromorphes présentant des colorations extra-oculaires différentes. Les résultats suggèrent que la même voie a été recrutée une seule fois pour produire la diversité de pattern. De plus, grâce à une analyse chimique par ultra-chromatographie couplée à de la spectrométrie de masse, nous avons identifié que la xanthopterin et l’erythropterin sont les deux pigments responsables de la couleur chez différentes espèces. Nous nous sommes aussi demandé comment le recrutement d'une seule et même voie conservée pouvait produire une telle diversité de pattern. En utilisant la technologie de transcriptomique du RNA-seq, nous avons identifié 167 facteurs de transcription co-exprimés dans les yeux, les antennes et les pattes des embryons de Limnogonus franciscanus. Ces protéines pourraient intervenir dans la régulation des gènes impliqués dans la formation des patterns de couleur embryonnaire. Nous avons initié un crible ARNi de ces facteurs de transcription. En conclusion, la pigmentation des punaises semi-aquatiques au stade embryonnaire est un bon modèle pour comprendre la co-option des voies génétiques et la question sous-jacente de la façon dont une voie conservée pourrait être réglementée pour produire divers phénotypes. / The principal aim of this doctoral thesis was to understand the genetic basis for the diversification of the extra-ocular pigmentation in Gerromorpha embryos. Most of the semi-aquatic bugs develop a variability of yellow or red colours patterns in legs and antennas during the embryonic stage. Since the red colour in appendages was similar to the one present in eyes, we hypothesized that the extra-ocular colours could be produced by the co-option of the eye pigments biosynthesis pathway. First we inferred the evolutionary history of this trait based on its presence or absence in embryos of 34 species. We found that the ancestral state of the trait in Gerromorpha was yellow and that six independent lineages evolved bright red colour, while two lineages lost the colour. Using RNAi and in situ hybridisation on homologous genes from the pteridine and ommochrome biosynthesis pathways, we described the genetic pathway involved in the production of pigments in eyes and extra-ocular tissues in Limnogonus franciscanus embryos. After that, we performed a screening of three genes from this pathway in five other species with different extra-ocular colours and patterns. We discovered that the same pathway was recruited once to produce the diversity of patterns in Gerromorpha. Furthermore, we identified by UPLC-HRMS that xanthopterin and erythropterin pigments produce the variability of colours and patterns in different species. Our next step aimed to understand how the recruitment of a conserved pathway could produce this striking diversity of colour patterns. Using RNA-Seq technology and bioinformatics tools, we identified 167 transcription factors that are co-expressed in eyes, antennas and legs of embryos in Limnogonus franciscanus. These proteins might be involved in the regulation of genes responsible for the different colour patterns. We have started an RNAi screen of these transcription factors. This project is still ongoing but in this thesis I will present the preliminary results and conclusions.In conclusion, the pigmentation of semi-aquatic bugs during the embryonic stage is a good model to understand the co-option of pre-existing genetic pathways and underlying the question of how a conserved pathway could be regulated to produce diverse morphological phenotypes.
2

Bricolage évolutif chez des drosophiles à pois noirs

Arnoult, Laurent 17 May 2013 (has links)
Au cours de mes travaux de thèse, je me suis penché sur le pendant génétique de l'adaptation. Certes, les mutations sont générées au hasard; mais quelles sont celles que l'évolution retient et pourquoi? Peut-on définir certains principes qui déterminent les chemins génétiques favoris qu'emprunte et ré-emprunte l'évolution ? Ces principes génétiques bornent-ils parfois le jeu des adaptations possibles ? Le substrat génétique qui nourrit la sélection est-il le même lorsqu'il s'agit de l'émergence d'un caractère nouveau ou bien lorsqu'il s'agit de la diversification ou le raffinement d'un caractère existant ?Pour répondre à ces questions, je me suis penché sur des drosophiles à pois noirs. En particulier, des drosophiles du groupe melanogaster, dont un ancêtre s'est paré d'une tache noire sur le bout de l'aile, il y a environ 20 millions d'années. Cette tache s'est transmise de génération en génération, en se modifiant de façon spectaculaire dans certaines lignées.J'ai d'abord tenté de mettre à jour la logique génétique du bricolage qui a fondé l'émergence puis la diversification de cette tache. Ces travaux suggèrent un modèle général dans lequel les deux versants de l'adaptation, émergence et diversification, correspondent à deux bricolages génétiques distincts.Dans un deuxième temps, je me suis concentré sur l'émergence de cette tache. Ce travail en cours a permis de dégager certaines caractéristiques génétiques du module de régulation qui sous-tend le développement de cette tache. Mon travail de thèse contribue, dans son ensemble, à une meilleure compréhension des ressorts génétiques sur lesquels repose l'adaptation. / In my thesis, I studied the genetics of adaptation. Certainly, mutations are randomly generated, yet evolutionary relevant mutations are not randomly distributed; why? Can we define some principles that determine the most favorable genetic paths, in the light of evolution? Would these principles sometimes limit the range of possible adaptations? Are mutations that feed emergence of a new character and diversification or refinement of an existing character the same? To answer these questions, I studied fruit flies with black spots. In particular, fruit flies from the melanogaster group, whose ancestor evolved a black spot on the tip of its wing, about 20 million years ago. This spot has been inherited through generations, and diversified dramatically in some lineages.I first tried to uncover the logic of genetic tinkering underlying the emergence and diversification of the spot. Our results suggest a general model in which the two sides of adaptation, emergence and diversification, correspond to two distinct genetic tinkering.Second, I focused strictly on the emergence of this spot. This ongoing work has identified some general genetic features of the regulatory module underlying the development of this spot.Overall, my thesis contributes to a better understanding of the genetics of adaptation.
3

Agency in the shadow of a co-opted state : territory, difference and democratisation in post-war Guatemala

Illmer, Patrick Josef January 2015 (has links)
This thesis examines a new form of agency for change that has surfaced in rural areas of post-war Guatemala around the defence of territory and natural resources. I argue that this new form of agency emerges in the shadow of a state co-opted by elite factions and manifests distinct qualities from previous expressions of revolutionary and democratic activism. It is localised and characterised by varied aspects of what I call ‘difference’, an antagonistic stance based on locally embedded political, economic and cultural meanings which challenges the elite-promoted reordering of relationships and spaces. This ‘difference’ is enacted through the ‘defence of territory’, which expresses a socio-political and cultural attachment to particular physical spaces and has instigated collective resistances to the implementation of projects linked to the exploitation of natural resources. The thesis analyses this form of agency through two case studies, one among indigenous communities in the Northern Quiché, the second among primarily non-indigenous communities in the municipalities of San José del Golfo and San Pedro Ayampuc. As this research demonstrates, given the firm integration of conventional channels of democratic participation into the patterns of state co-option, the primary aim of these struggles is the re-appropriation of decision-making processes and the carving out of spaces, in which their ‘difference’ can evolve. In the context of a co-opted state, these local expressions of agency create spaces in which fragile, embryonic forms of collective interaction and deliberation that represent a condition for democratic processes, are kept alive. However, their non-linear articulations and specific local character are also a testament to the complexity of the construction of democratic processes in countries like Guatemala.
4

Representation of ethnic groups in subnational political institutions: The case of the Democratic Republic of Congo

Samuel, Matemane Iraguha January 2017 (has links)
Magister Legum - LLM (Public Law and Jurisprudence) / With approximately 450 tribes and 250 ethnic groups in a territory of 2 345 095 km2,1the Democratic Republic of Congo (DRC) is one of the world's largest, populous, and multiethnolinguistic countries. Since the departure of the Belgian coloniser in 1960, this Member State of the Southern Africa Development Community (SADC) is facing a myriad of institutional crises, bloody conflicts and wars, mainly caused by the design of political institutions and the side-lining of some ethnic groups from political institutions. For many decades, Congolese provinces have seen numerous violent ethnic-driven conflicts, which led to institutional instability, political crisis, secessions, massacres and wars. The bloodiest of them all were the first and second Congolese wars. From 1996 to 2002, these so-called "African first world war" cost the DRC the lives of millions of people, divided it into many small "republics" and destroyed the few political and economic infrastructures that survived four decades of institutional instability and dictatorship.
5

Caracterização estrutural e de expressão do gene exuperantia (exu) em Anastrepha fraterculus (Diptera, Tephritidae) e evidências de seleção positiva em Cyclorrhapha

Oliveira, Janaína Lima de 27 February 2014 (has links)
Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-10-10T13:11:28Z No. of bitstreams: 1 DissJLO.pdf: 1924288 bytes, checksum: 2b2ce6a9b82a3dfb41ddb5f343fde1b7 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T19:39:32Z (GMT) No. of bitstreams: 1 DissJLO.pdf: 1924288 bytes, checksum: 2b2ce6a9b82a3dfb41ddb5f343fde1b7 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T19:39:39Z (GMT) No. of bitstreams: 1 DissJLO.pdf: 1924288 bytes, checksum: 2b2ce6a9b82a3dfb41ddb5f343fde1b7 (MD5) / Made available in DSpace on 2016-10-20T19:39:46Z (GMT). No. of bitstreams: 1 DissJLO.pdf: 1924288 bytes, checksum: 2b2ce6a9b82a3dfb41ddb5f343fde1b7 (MD5) Previous issue date: 2014-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The genus Anastrepha (Tephritidae) has several species of great economic importance due to their impact in fruticulture. We are particularly interested in the evolutionary history of Anastrepha fraterculus, the most relevant species in the closely related group of species fraterculus, which has undergone recent divergence and holds the majority of species of economic importance in the genus. To better understand the differentiation process and identification in the group, we need to find molecular and morphological markers that are involved with the differences between species. Reproductive genes have, in general, been very informative in this regard due to their rapid evolutionary rates, although few of them have been studied and characterized in this species so far. Therefore, the present study focuses on the exuperantia gene (exu), which participates in both oogenesis (localization of bicoid and oskar mRNAs) and spermatogenesis, since exu embryos from mutant mothers are unviable and males are sterile. Thus, the first step was to use Next generation sequencing strategies (RNA-seq) to structurally characterize and define expression patterns of this gene between sexes in the cephalic and reproductive tissues of A. fraterculus. A. fraterculus has similar structural and expression patterns to Drosophila melanogaster in reproductive tissues, in which the transcripts differ between sexes for the 5’ and 3’ untranslated regions (UTRs). We describe for the first time the expression of exu in cephalic tissues, involving a new isoform that is common to both sexes. All these alternative spliced transcripts share a common coding region, resulting in the same protein. We used the exu coding region, along with sequences from several Diptera to investigate the molecular evolution of exu in Cyclorrhapha. This group has experienced an enormous adaptive radiation, associated with molecular and morphological changes, and by comparing the dN/dS ratio between Cyclorrhapha and other Diptera we found that exu was subjected to positive selection in Cyclorrhapha for at least two sites in the coding region. One of the sites is present in the RNA exonuclease-like domain of exu. The second site is located in a not characterized region that is conserved and under purifying selection in Diptera, suggesting that it may be an important region of the protein. The adaptive changes found in exu may reflect an evolutionary gain that allowed its co-option for a new function the gene performs in Cyclorrhapha: the localization of bicoid in the anterior region of the oocyte, since bcd is a gene exclusive of Cyclorrhapha. / O gênero Anastrepha (Tephritidae) é de grande importância econômica devido ao seu impacto na fruticultura nacional. Estudamos aqui a história evolutiva de Anastrepha fraterculus, a espécie mais relevante do grupo fraterculus, o qual sofreu divergência recente e contém a maioria das espécies de importância econômica do gênero. Para entender melhor o processo de especiação nesse grupo, e auxiliar no processo de identificação taxonômica, precisamos estabelecer marcadores morfológicos e moleculares envolvidos com as diferenças entre as espécies. Genes envolvidos com a reprodução têm se mostrado bastante informativos para estes propósitos, devido às rápidas taxas evolutivas que apresentam, embora poucos tenham sido estudados e caracterizados nessas espécies até o momento. Nesse sentido, esse trabalho tem como foco o gene exuperantia (exu), que participa tanto da ovogênese (localização dos mRNAs bicoid e oskar) quanto da espermatogênese, uma vez que embriões formados a partir de fêmeas mutantes exu são inviáveis e machos mutantes exu são estéreis. Assim, o primeiro passo foi caracterizar estruturalmente e definir padrões de expressão desse gene entre os sexos nos tecidos cefálicos e reprodutivos em A. fraterculus. Utilizando sequenciamento de próxima geração (RNA-seq), identificamos um padrão estrutural e de expressão semelhante àquele de Drosophila melanogaster em tecidos reprodutivos: os transcritos diferem nas regiões não traduzidas (UTRs) 5’ e 3’ entre os sexos. Pela primeira vez identificamos a expressão de exu em tecidos cefálicos, envolvendo uma nova isoforma que é igual nos dois sexos. Em todos os casos, as regiões codificadoras são iguais, resultando na sequência proteica. Utilizamos essa região codificadora de exu junto com sequências de outras espécies de Diptera para investigar a evolução molecular de exu em Cyclorrhapha, que sofreu uma grande radiação adaptativa associada com alterações morfológicas e moleculares. Comparando a relação dN/dS entre Cyclorrhapha e outros Diptera, encontramos dois sítios sob seleção positiva em Cyclorrhapha, um deles presente no domínio semelhante à RNA exonuclease de exu. O segundo está presente em uma região não caracterizada para domínios proteicos, mas que é bem conservada e está sob seleção purificadora em Diptera, sugerindo ser uma região importante da proteína. As mudanças adaptativas encontradas em exu podem refletir um ganho evolutivo que permitiu sua co-optação para uma nova função em Cyclorrhapha: a de localização de bicoid na região anterior do ovócito, visto que bcd é um gene exclusivo de Cyclorrhapha.
6

Peace in whose time? : ripeness and local negotiated agreements : the Sangin Accord, Helmand Province, Afghanistan, 2006-2011

Beautement, Mark January 2016 (has links)
Sangin District, in Helmand Province, was once described by US Defense Secretary Robert Gates as “the most dangerous not only in Afghanistan but maybe the whole world.” Nevertheless, Afghan Government officials received a written offer of peace from the principal local grouping aligned to the Taliban on the 29th May 2010, before NATO’s surge, or Sangin’s handover from U.K. to U.S. forces. This offer evolved into the local negotiated agreement known as the Sangin Accord, announced in January 2011. This is the first academic study of that agreement. This work also considers relationships between motivations for negotiation at the local level, and international policy and actions: military power, stabilisation activities, and reconciliation (including the co-option and legitimation of enemies). It compares explanations for negotiated agreements from academic theory and military doctrine, especially I. William Zartman’s ripeness theory and its evolutions, and offers suggestions for other local reintegration or reconciliation scenarios. The conclusions offer observations on applying Ripeness theory when intervening to seek political reconciliation in a local area removed from centralised authority, and without a permanent military advantage – which I term ‘fringe areas’. It highlights the impact of history (both received and remembered), and traumatic experiences, on memory, perception and rationality; vital factors for Ripeness theory. Finally, it explores the paradox between policymakers’ desire to negotiate from a position of strength, and Ripeness theory’s contradictory requirement for a mutually perceived hurting stalemate – simultaneously alongside a political Way Out – as essential preconditions to genuine negotiation.
7

Exploring morphological innovation and diversification: Analysis of genes involved in gin-trap formation and antenna remodeling during metamorphosis in Tribolium castaneum

Hu, Yonggang 11 August 2017 (has links)
No description available.
8

Co-opted boards and voluntary disclosure

Ha Yoon Yee (11205408) 29 July 2021 (has links)
<p>This study examines whether directors appointed after a Chief Executive Officer (CEO) assumed office (“co-opted” directors) affect corporate voluntary disclosure. I find evidence that firms issue management earnings forecasts less frequently when directors are co-opted. These results hold even when these directors are considered independent by regulatory definitions. Cross-sectional tests indicate that my results are stronger when firms disclose bad news, provide higher pay to co-opted directors, CEOs have greater ability to withhold disclosure, and co-opt directors early in the CEO’s tenure. I use NASDAQ/NYSE listing requirements as an exogenous shock to board co-option and find that director co-option has a causal link to less voluntary disclosure. I further show that the effect was robust to the effect of CEOs’ disclosure preferences and experience inside the firm. This study suggests that boards that appear independent using the conventional measures may fail to elicit adequate voluntary disclosure to monitor managers. </p>
9

Agency in the Shadow of a co-opted State: Territory, Difference and Democratisation in post-war Guatemala

Illmer, Patrick Josef January 2015 (has links)
This thesis examines a new form of agency for change that has surfaced in rural areas of post-war Guatemala around the defence of territory and natural resources. I argue that this new form of agency emerges in the shadow of a state co-opted by elite factions and manifests distinct qualities from previous expressions of revolutionary and democratic activism. It is localised and characterised by varied aspects of what I call ‘difference’, an antagonistic stance based on locally embedded political, economic and cultural meanings which challenges the elite-promoted reordering of relationships and spaces. This ‘difference’ is enacted through the ‘defence of territory’, which expresses a socio-political and cultural attachment to particular physical spaces and has instigated collective resistances to the implementation of projects linked to the exploitation of natural resources. The thesis analyses this form of agency through two case studies, one among indigenous communities in the Northern Quiché, the second among primarily non-indigenous communities in the municipalities of San José del Golfo and San Pedro Ayampuc. As this research demonstrates, given the firm integration of conventional channels of democratic participation into the patterns of state co-option, the primary aim of these struggles is the re-appropriation of decision-making processes and the carving out of spaces, in which their ‘difference’ can evolve. In the context of a co-opted state, these local expressions of agency create spaces in which fragile, embryonic forms of collective interaction and deliberation that represent a condition for democratic processes, are kept alive. However, their non-linear articulations and specific local character are also a testament to the complexity of the construction of democratic processes in countries like Guatemala.
10

Untersuchungen zur Angiogenese des Burkitt-Lymphoms unter besonderer Berücksichtigung des Lymphocyte enhancer-binding factor-1 / Examination of Burkitt lymphoma´s angiogenesis with special consideration of Lymphocyte enhancer binding factor-1

Wilming, Pia Josefa 29 November 2017 (has links)
No description available.

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