Ce travail s'inscrit dans le cadre d'un projet soutenu par la Région wallonne et a été réalisé en collaboration entre les unités de Chimie Organique et Médicinale (CHOM), de Chimie Structurale et des Mécanismes Réactionnels (CSTR), et de Chimie et Physique des Hauts Polymères (POLY). Il concerne la modification des propriétés du polypropylène (PP) isotactique par mise en œuvre réactive, et plus particulièrement le contrôle de sa cristallinité par l'action d'un composé bromé (N-bromosuccinimide) en présence d'un initiateur de radicaux libres à haute température (entre 180 et 260°C). L'objectif principal de cette étude est de parvenir à identifier et à contrôler les modifications induites au sein des produits, ce qui implique une compréhension fine des mécanismes chimiques intervenant lors de la mise en œuvre réactive du PP. Ces connaissances permettraient en outre de substituer la N-bromosuccinimide (qui génère des sous-produits toxiques et polluants) par un autre additif en vue d'une meilleure valorisation du procédé et des produits. La stratégie repose sur une double approche, basée d'une part sur une étude des divers paramètres qui influencent la réaction sur polymère, et d'autre part sur la synthèse d'un composé modèle du PP : le 2,4,6,8,10-pentaméthylundécane (PMU). Par extrusion réactive du polymère, nous avons obtenu des PP à cristallinité contrôlée (PPCC ; de semi-cristallin à amorphe), dont certains présentent un caractère élastomère marqué. Des études effectuées principalement par analyse thermique et par résonance magnétique nucléaire ont permis de corréler ces propriétés macroscopiques à une microstructure à stéréoblocs isotactiques/atactiques (épimérisation des carbones tertiaires du PP), combinée à la présence de branchements longs (recombinaison de macroradicaux). Par ailleurs, nous avons mis en évidence les différents paramètres susceptibles d'influencer la réaction d'épimérisation du PP. Bien que les informations découlant de ces études nous aient permis de proposer les principaux mécanismes qui entrent en jeu lors de la réaction, seule une étude sur composé modèle peut néanmoins donner accès aux méthodes d'analyses nécessaires à la confirmation de ces mécanismes. Nous avons par conséquent entrepris la synthèse d'un oligomère de propylène pour permettre cette étude sur composé modèle. La synthèse du PMU telle que rapportée dans la littérature s'est avérée plus difficile que prévu, principalement du fait d'un manque de reproductibilité au niveau de l'étape clé. Nous avons donc établi une voie de synthèse originale permettant l'obtention du PMU (mélange de stéréoisomères) avec un rendement global de 45% sur 7 étapes (à l'échelle de plusieurs grammes de produit). En outre, cette voie nous a donné accès au 6-hydroxyméthyl-2,4,8,10-tétraméthylundécane et au 6-p-toluènesulfonyloxyméthyl-2,4,8,10-tétraméthylundécane, pour lesquels des techniques chromatographiques ont permi une séparation des diastéréoisomères. La transposition de ces expériences à plus grande échelle permettra d'envisager l'obtention du (4R,6s,8S)-PMU, en vue de futures études mécanistiques relatives à l'épimérisation du PP de configuration initialement isotactique. / This work is part of a project supported by the Walloon Region, and it was performed in collaboration between the Chimie Organique et Médicinale (CHOM), Chimie Structurale et des Mécanismes Réactionnels (CSTR), and Chimie et Physique des Hauts Polymères (POLY) laboratories. Its object is the modification of the isotactic polypropylene (PP) properties by reactive processing, and more especially the control of PP crystallinity by means of a brominated additive (N-bromosuccinimide) in presence of a free radical initiator at high temperatures (between 180 and 260°C). The main objective of this study is to identify and to control the modifications induced in the products, which implies a fine understanding of the chemical mechanisms occuring during the PP reactive processing. This knowledge would allow us, subsequently, to substitute another additive for the N-bromosuccinimide (which yields toxic and polluting by-products), in order to achieve a better applicability of both the process and the products. The strategy relies on a double approach : on one side, on a study of the various parameters affecting the reaction on the polymer, and on the other side on the synthesis of a model compound of PP : 2,4,6,8,10-pentamethylundecane (PMU). By means of reactive extrusion of the polymer, we obtained controlled crystallinity PP's (from semi-crystalline to amorphous), including some with an elastomeric behaviour. Studies carried out mainly by thermal analysis and nuclear magnetic resonance allowed us to correlate these macroscopic properties to an isotactic/atactic stereoblock microstructure (epimerization of the PP tertiary carbons), combined with the presence of long chain branchings (recombination of macroradicals). Moreover, we highlighted the various parameters that are able to influence the yield of the epimerization reaction. Even if the informations arising from these studies allowed us to propose the main mechanisms involved in the PP modification, only a mechanistic study carried out on a model compound would give us access to the characterization methods required for the confirmation of these mechanisms. We undertook, subsequently, the synthesis of a propene oligomer. The PMU synthesis, as stated in the litterature, revealed itself more difficult than initially foreseen, mainly due to a lack of reproducibility concerning the key step. Therefore we established a new synthesis pathway for the PMU (as a mixture of stereoisomers) with a global yield of 45% over 7 steps (multigram scale). Moreover, this pathway gave us access to 6-hydroxymethyl-2,4,8,10-tetramethylundecane and 6-p-toluenesulfonyloxymethyl-2,4,8,10-tetramethylundecane, for which chromatographic techniques allowed a separation of the diastereoisomers. The transposition of these experiments on a larger scale would allow us to obtain the (4R,6s,8S)-PMU for future mechanistic studies relative to the epimerization reaction of initially isotactic PP.

In the canyon grasslands of Garden Creek Ranch Preserve in Idaho, where the threatened plant Silene spaldingii occurs and invasion by the exotic species Centaurea solstitialis and Bromus tectorum is proceeding rapidly, I examined environmental and community patterns of site invasion, and evaluated the apparent influence of invasion on Silene population vigor. In addition, two separate lightning fires at the preserve presented the opportunity to examine the short-term influence of late-season fire on this species and its associated bunchgrass plant community. I found that Silene-supporting sites most often invaded by exotics were on relatively gentle slopes that received more incident radiation. This pattern may relate, in part, to light requirements of Centaurea solstitialis. Invaded sites were also typically at higher elevations, which may indicate they were moister and therefore more productive. The plant communities in invaded Silene-supporting sites were similar to plant communities in uninvaded sites, although invaded sites tended to have greater legume and exotic annual grass cover. Exotic species invasion did not appear to influence negatively the vigor of Silene populations, as indicated by similar plant height and comparable levels of flowering, fruit and seed set in invaded and uninvaded populations. The similarity in Silene vigor between invaded and uninvaded sites may reflect a moderating influence of site productivity in invaded populations, or may indicate that mature Silene plants and the exotic species partition space or resources differently, potentially reducing competition between them. However, Silene recruitment may be limited by competition from weeds; my data did not allow a rigorous test of this possibility. Fire apparently decreased cover of Festuca idahoensis and increased cover of Lupinus sericeus in the first year after burning, while cover of Pseudoroegneria spicata, exotic grasses, and most other forb species did not differ between burned and unburned areas. Silene cover and abundance within populations were similar before and after fire. Burning did not appear to influence levels of flowering, change the number of flowers or capsules produced per stem, or alter the number of seeds per capsule. Burning decreased plant size slightly, and decreased the proportion of flowers that matured to seed-filled capsules. Silene and the plant communities that support this species appear well suited to late season fire, however the response to burning in other seasons or at higher frequencies remains unknown in this study area. / Graduation date: 2003

Invasive exotic species threaten the biodiversity and function of native ecosystems. Existing models, attempting to predict and control successful invaders, often emphasize isolated stages of in their life history and fail to formalize interactions between exotic species and recipient environments. In order to elucidate key mechanisms in the success of select invaders, I investigated the role of dispersal, establishment, proliferation, and persistence in their threat to natural areas. Focusing on Riding Mountain National Park, Manitoba, Canada, I integrated the native climatic range and biological traits of 251 exotic vascular plants reported inside and outside the park. Based on their climatic range in Europe, 155 among 174 exotic plant species absent from the Park were predicted to establish within its boundaries; among these, 40 clonal perennials were considered the highest threat to the Park’s biodiversity. Focusing on smooth brome (Bromus inermis Leyss.), a Eurasian perennial, threatening the structure and function of native prairies throughout the Great Plains, I extended my research to investigate the role of dispersal, establishment, proliferation, and persistence in characterizing its threat to the endemic diversity of northern fescue prairies, protected within Riding Mountain National Park. Patterns of smooth brome invasions were contingent on the type of propagules dispersed. The shallow dispersal gradient of individual florets combined with the steeper gradient of panicles and spikelets suggested that smooth brome is capable of simultaneously invading along dense fronts as well as by establishing isolated foci. While low correlations between the number of dispersed seeds and their recruitment suggested post-dispersal transport, seedling establishment remained contingent on prairie diversity. Seedling biomass increased with declining plant diversity, however, its impact depended on the availability of soil nitrogen. As a result, disturbed areas, preserving the root function of native plants, resisted smooth brome establishment. Even though low nitrogen contributed to a decline in seedling biomass, physiological integration between ramets facilitated their vegetative proliferation in low resource environments. Despite its rapid establishment and proliferation, smooth brome productivity declined at the center of invading clones. Although field and greenhouse observations failed to implicate soilborne pathogens, reasons for the observed decline remain unresolved. My research demonstrates that while Riding Mountain National Park and other natural areas in western Canada will continue to be impacted by exotic plants, integrating key stages in their life history provides an important conceptual framework in predicting their threat to natural areas and prioritizing management. / October 2008

Invasive exotic species threaten the biodiversity and function of native ecosystems. Existing models, attempting to predict and control successful invaders, often emphasize isolated stages of in their life history and fail to formalize interactions between exotic species and recipient environments. In order to elucidate key mechanisms in the success of select invaders, I investigated the role of dispersal, establishment, proliferation, and persistence in their threat to natural areas. Focusing on Riding Mountain National Park, Manitoba, Canada, I integrated the native climatic range and biological traits of 251 exotic vascular plants reported inside and outside the park. Based on their climatic range in Europe, 155 among 174 exotic plant species absent from the Park were predicted to establish within its boundaries; among these, 40 clonal perennials were considered the highest threat to the Park’s biodiversity. Focusing on smooth brome (Bromus inermis Leyss.), a Eurasian perennial, threatening the structure and function of native prairies throughout the Great Plains, I extended my research to investigate the role of dispersal, establishment, proliferation, and persistence in characterizing its threat to the endemic diversity of northern fescue prairies, protected within Riding Mountain National Park. Patterns of smooth brome invasions were contingent on the type of propagules dispersed. The shallow dispersal gradient of individual florets combined with the steeper gradient of panicles and spikelets suggested that smooth brome is capable of simultaneously invading along dense fronts as well as by establishing isolated foci. While low correlations between the number of dispersed seeds and their recruitment suggested post-dispersal transport, seedling establishment remained contingent on prairie diversity. Seedling biomass increased with declining plant diversity, however, its impact depended on the availability of soil nitrogen. As a result, disturbed areas, preserving the root function of native plants, resisted smooth brome establishment. Even though low nitrogen contributed to a decline in seedling biomass, physiological integration between ramets facilitated their vegetative proliferation in low resource environments. Despite its rapid establishment and proliferation, smooth brome productivity declined at the center of invading clones. Although field and greenhouse observations failed to implicate soilborne pathogens, reasons for the observed decline remain unresolved. My research demonstrates that while Riding Mountain National Park and other natural areas in western Canada will continue to be impacted by exotic plants, integrating key stages in their life history provides an important conceptual framework in predicting their threat to natural areas and prioritizing management.

Invasive exotic species threaten the biodiversity and function of native ecosystems. Existing models, attempting to predict and control successful invaders, often emphasize isolated stages of in their life history and fail to formalize interactions between exotic species and recipient environments. In order to elucidate key mechanisms in the success of select invaders, I investigated the role of dispersal, establishment, proliferation, and persistence in their threat to natural areas. Focusing on Riding Mountain National Park, Manitoba, Canada, I integrated the native climatic range and biological traits of 251 exotic vascular plants reported inside and outside the park. Based on their climatic range in Europe, 155 among 174 exotic plant species absent from the Park were predicted to establish within its boundaries; among these, 40 clonal perennials were considered the highest threat to the Park’s biodiversity. Focusing on smooth brome (Bromus inermis Leyss.), a Eurasian perennial, threatening the structure and function of native prairies throughout the Great Plains, I extended my research to investigate the role of dispersal, establishment, proliferation, and persistence in characterizing its threat to the endemic diversity of northern fescue prairies, protected within Riding Mountain National Park. Patterns of smooth brome invasions were contingent on the type of propagules dispersed. The shallow dispersal gradient of individual florets combined with the steeper gradient of panicles and spikelets suggested that smooth brome is capable of simultaneously invading along dense fronts as well as by establishing isolated foci. While low correlations between the number of dispersed seeds and their recruitment suggested post-dispersal transport, seedling establishment remained contingent on prairie diversity. Seedling biomass increased with declining plant diversity, however, its impact depended on the availability of soil nitrogen. As a result, disturbed areas, preserving the root function of native plants, resisted smooth brome establishment. Even though low nitrogen contributed to a decline in seedling biomass, physiological integration between ramets facilitated their vegetative proliferation in low resource environments. Despite its rapid establishment and proliferation, smooth brome productivity declined at the center of invading clones. Although field and greenhouse observations failed to implicate soilborne pathogens, reasons for the observed decline remain unresolved. My research demonstrates that while Riding Mountain National Park and other natural areas in western Canada will continue to be impacted by exotic plants, integrating key stages in their life history provides an important conceptual framework in predicting their threat to natural areas and prioritizing management.

A vegetation monitoring study was conducted from 1998 to 2013 at Camp Grafton South (CGS) in Eddy County, North Dakota to assess how climatic, grazing, and military training disturbance affects plant community composition. The objectives of this study were to 1) describe the prairie vegetation at CGS across three topographic positions and 2) explore any shifts in plant community composition in correlation with time. Frequency data was collected at 45 randomly selected transects on lowland, midland, and upland grassland plant communities on native prairie. Plant communities were compared using non-metric multidimensional scaling (NMS) ordination. NMS ordination showed that the three plant communities were distinct from one another, and that the frequency of the invasive graminoids Kentucky bluegrass (Poa pratensis L.) and smooth brome (Bromus inermis Leyss.) increased. Increases in precipitation, temperature, and growing season days appear to be the primary influence on the changes in plant communities from 1998-2013.

No description available.

This thesis seeks to place drama of the Caroline commercial theatre in its contemporary political and legal context; particularly, it addresses the ways in which the struggle for supremacy between the royal prerogative, common law and local custom is constructed and negotiated in plays of the period. It argues that as the reign of Charles I progresses, the divine right and absolute power of the monarchy on stage begins to lose its authority, as playwrights, particularly Massinger and Brome, present a decline from divinity into the presentation of an arbitrary man who seeks to impose and increase his authority by enforcing obedience to selfish and wilful actions and demands. This decline from divinity, I argue, allows for the rise of a competing legitimate legal authority in the form of common law. Engaging with the contemporary discourse of custom, reason and law which pervades legal tracts of the period such as Coke’s Institutes and Reports and Davies’ ‘Preface Dedicatory’ to Le Primer Report des Cases & Matters en Ley resolues & adiudges en les Courts del Roy en Ireland, drama by Brome, Jonson, Massinger and Shirley presents arbitrary absolutism as madness, and adherence to customary common law as reason which restores order. In this climate, the drama suggests, royal manipulation of the law for personal ends, of which Charles I was often accused, destabilises law and legal authority. This destabilisation of legal authority is examined in a broader context in plays set in areas outwith London, geographically distant from central authority. The thesis places these plays in the context of Charles I’s attempts to centralise local law enforcement through such publications as the Book of Orders. When maintaining order in the provinces came into conflict with central legislation, the local officials exercised what Keith Wrightson describes as ‘two concepts of order’, turning a blind eye to certain activities when strict enforcement of law would create rather than dissolve local tensions. In both attempting to insist on unity between the centre and the provinces through tighter control of local officials, and dividing the centre from the provinces in the dissolution of Parliament, Charles’s government was, the plays suggest, in danger not only of destabilising and decentralising legal authority but of fragmenting it. This thesis argues that drama provides a medium whereby the politico-legal debates of the period may be presented to, and debated by, a wider audience than the more technical contemporary legal arguments, and, during Charles I’s personal rule, the theatre became a public forum for debate when Parliament was unavailable.

Mobilité, désir d’accéder à une meilleure qualité de vie, attraction de la campagne s’accélèrent depuis une trentaine d’années au Québec, comme ailleurs en occident. La campagne et les usages que l’on en fait se diversifient et se complexifient, à l’instar des populations qui l’habitent. Dans ce contexte, cette thèse se penche sur l’expérience géographique de la campagne, en tant qu’espace social. Elle met en lumière l’expérience géographique des ruraux, plus particulièrement les modalités de leur rencontre dans divers lieux qui marquent leur quotidien. Le matériel empirique de la thèse consiste surtout en des témoignages recueillis lors d’entrevues qualitatives menées auprès de nouveaux résidents et des ruraux de longue date dans deux municipalités régionales de comté (MRC) contrastées au Québec : Brome-Missisquoi et Arthabaska. La démarche privilégiée et les principales contributions qui en découlent se déclinent en trois temps. D’abord, une comparaison directe des deux populations rurales étudiées fait ressortir que leurs pratiques de mobilité et leurs sens des lieux se rejoignent dans une certaine mesure, mais affichent aussi des différences. Par exemple, elles partagent toutes deux un sentiment d’appartenance marqué à leur milieu de vie, mais pas nécessairement avec la même intensité et pour les mêmes raisons. En outre, leurs pratiques d’engagement local convergent, favorisées par un même désir de contribuer au bien-être de leur milieu. La thèse démontre aussi que certains lieux de sociabilité rapprochent ces deux groupes au quotidien, quoique subsistent des tensions notamment liées à leurs origines rurale ou urbaine, leur classe sociale, leurs expériences antérieures des lieux, la durée vécue dans leur milieu de vie, leur historique familial, leurs représentations et usages de la campagne... Se décèle aussi un effet de milieu entre les deux MRC à cet égard. Dans l’ensemble, leur rencontre s’avère timide et surtout réservée à l’espace public. Enfin, en se basant sur leurs représentations de l’avenir, la thèse illustre que l’espace de leur rencontre représente un espace d’opportunités pour le dialogue sur la campagne, bien que celui-ci ne se produise pas sans affrontements et heurts. Ainsi, au-delà du binarisme traditionnel et antagonique lié aux statuts de « nouveaux » et « anciens » ruraux, l’espace de rencontre, celui à l’intérieur duquel s’opèrent à la fois tensions, négociations, compromis et nouvelles alliances, participe à construire la nouvelle ruralité contemporaine.

Mobilité, désir d’accéder à une meilleure qualité de vie, attraction de la campagne s’accélèrent depuis une trentaine d’années au Québec, comme ailleurs en occident. La campagne et les usages que l’on en fait se diversifient et se complexifient, à l’instar des populations qui l’habitent. Dans ce contexte, cette thèse se penche sur l’expérience géographique de la campagne, en tant qu’espace social. Elle met en lumière l’expérience géographique des ruraux, plus particulièrement les modalités de leur rencontre dans divers lieux qui marquent leur quotidien. Le matériel empirique de la thèse consiste surtout en des témoignages recueillis lors d’entrevues qualitatives menées auprès de nouveaux résidents et des ruraux de longue date dans deux municipalités régionales de comté (MRC) contrastées au Québec : Brome-Missisquoi et Arthabaska. La démarche privilégiée et les principales contributions qui en découlent se déclinent en trois temps. D’abord, une comparaison directe des deux populations rurales étudiées fait ressortir que leurs pratiques de mobilité et leurs sens des lieux se rejoignent dans une certaine mesure, mais affichent aussi des différences. Par exemple, elles partagent toutes deux un sentiment d’appartenance marqué à leur milieu de vie, mais pas nécessairement avec la même intensité et pour les mêmes raisons. En outre, leurs pratiques d’engagement local convergent, favorisées par un même désir de contribuer au bien-être de leur milieu. La thèse démontre aussi que certains lieux de sociabilité rapprochent ces deux groupes au quotidien, quoique subsistent des tensions notamment liées à leurs origines rurale ou urbaine, leur classe sociale, leurs expériences antérieures des lieux, la durée vécue dans leur milieu de vie, leur historique familial, leurs représentations et usages de la campagne... Se décèle aussi un effet de milieu entre les deux MRC à cet égard. Dans l’ensemble, leur rencontre s’avère timide et surtout réservée à l’espace public. Enfin, en se basant sur leurs représentations de l’avenir, la thèse illustre que l’espace de leur rencontre représente un espace d’opportunités pour le dialogue sur la campagne, bien que celui-ci ne se produise pas sans affrontements et heurts. Ainsi, au-delà du binarisme traditionnel et antagonique lié aux statuts de « nouveaux » et « anciens » ruraux, l’espace de rencontre, celui à l’intérieur duquel s’opèrent à la fois tensions, négociations, compromis et nouvelles alliances, participe à construire la nouvelle ruralité contemporaine.