Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2003. / Bibliogr.: f. [177]-183. Document électronique également accessible en format PDF. CaQCU

La reconstruction de lésions osseuses complexes reste un défi dans le domaine de la chirurgie orthopédique et maxillo-faciale. A ce jour, la technique de référence reste la greffe d’os autologue. Cependant cette technique présente de nombreuses limites (risque d’infection, morbidité au site de prélèvement). Dans ce contexte, l’ingénierie tissulaire peut apporter des solutions de reconstruction innovantes. En effet l’utilisation de matrices ostéoconductrices et ostéoinductrices permettrait de remplacer l’autogreffe. Le premier objectif de ce travail a été de mettre au point une matrice de polysaccharides, contenant des particules d’hydroxyapatite (HA) dopées avec du strontium (Sr), afin de stimuler à la fois la régénération osseuse, mais également l’angiogenèse. Les résultats obtenus in vitro et in vivo nous ont permis d’optimiser la formulation de cette matrice, en termes de quantités de particules d’hydroxyapatite dopées par différents taux de substitution en strontium, dispersées au sein de la matrice. La deuxième partie de ce travail a été consacrée à l’application de cette matrice à la technique de Masquelet afin de remplacer l’utilisation de l’autogreffe. Cette procédure chirurgicale en deux temps, basée sur la formation d’une membrane induite, est utilisée fréquemment en chirurgie orthopédique et maxillo-faciale. Le premier temps opératoire utilise un ciment chirurgical, le (poly(méthyl)méthalcrylate, PMMA) qui entraîne la formation d’une membrane induite vascularisée. Notre travail a été de remplacer ce ciment par du silicone et d’étudier l’influence de la radiothérapie sur la qualité et la fonction de la membrane ainsi formée. Les premiers essais d’évaluation de cette matrice ont été réalisés chez le rat après résection segmentaire du fémur, suivie d’une procédure de radiothérapie. Les perspectives de ce travail sont d’évaluer la performance de cette matrice dans une lésion mandibulaire de grand volume, après irradiation, chez le gros animal. / Reconstruction of large and complex bone defects remains a challenge for orthopaedic and maxillo-facial surgery. The gold standard strategy for bone reconstruction is the autologous bone graft. However, this approach still exhibits some limitations (infection risks, morbidity at the donor site). In this context, tissue engineering can provide innovative solutions for bone reconstruction. Indeed, the use of osteoconductives and osteoinductives matrices could replace autograft. Based on previous data obtained by our laboratory, the first objective of this work was to develop a composite matrix of polysaccharides containing hydroxyapatite (HA) particles doped with strontium (Sr), to stimulate both bone formation and angiogenesis. In vitro and in vivo results allow us to optimize the amount of HA particules and the ratio of Sr-substitution within the polysaccharide-based matrix. The second part of this work was to apply this biomaterial in the context of Masquelet approach. These two time procedure surgery, based on the formation of an induced membrane, is commonly used in orthopaedic and maxillo-facial surgery. The first chirurgical step uses a surgical cement (poly(methyl)methalcrylate, PMMA) to promote around it the formation of a vascularized membrane. Our work was to replace this cement by silicone and to study the influence of radiotherapy treatment on the quality and the function of this induced membrane. The first preclinical evaluation of this matrix has been performed on a rat femoral segmental bone defect, followed by a radiotherapy procedure. The perspectives of this work are to evaluate the performances of this matrix on irradiated segmental mandibular bone defect in large animal.

Des anomalies nucléosynthétiques ont été observées dans des météorites pour plusieurs éléments. L’ampleur de ces anomalies ainsi que leur répartition entre les objets du système solaire renseigne sur le degré d’hétérogénéité de la nébuleuse solaire. L’étude des phases porteuses de ces anomalies procure des informations sur les processus à l’origine de cette hétérogénéité. Les datations par radiochronomètres de courte période reposent sur la répartition hétérogène des éléments père et fils. L’utilisation de ces outils nécessite donc l’étude parallèle des variations nucléosynthétiques de ces éléments. / Nucleosynthetic anomalies have been observed in meteorites for many elements. The magnitude and repartition of these anomalies provide information about the degree of heterogeneity of the solar nebula. The study of the nucleosynthetic anomalies carriers could also give insight into the processes responsible for this heterogeneity. The presence or absence of small variations in nucleosynthetic processes is a key for the use of the short-lived radiochronometers. Small variations in the repartition of the parent or daughter isotope can lead to misinterpretations of relative ages.

Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Le ranélate de strontium, prescrit dans le traitement de l'ostéoporose ménopausique, possède 2 atomes de strontium stable pouvant se fixer au minéral osseux. Le strontium a un effet dissociant sur le remodelage osseux, diminuant la résorption tout en augmentant la formation. Cependant, ses effets osseux ne sont pas complètement élucidés, en particulier ses interactions avec le minéral. Chez le singe, le strontium maintient à un niveau physiologique les propriétés intrinsèques majeures du tissu osseux, que ce soit aux niveaux tissulaire global ou des unités de remodelage. Chez la femme ostéoporotique ménopausée traitée par le ranélate de strontium, les caractéristiques du cristal d'apatite sont maintenues à un niveau physiologique. Par ailleurs, quelle que soit la durée du traitement (2 à 96 mois), le strontium est toujours distribué de façon hétérogène, présent principalement dans l'os récent formé pendant le traitement, les aires osseuses contenant du strontium augmentent progressivement mais de moins en moins avec la durée du traitement. Le contenu osseux focal en strontium est stable de 2 à 60 mois puis augmente de 60 à 96 mois, et la minéralisation secondaire est maintenue à un niveau physiologique. Enfin, après 6 et 12 mois de traitement, le ranélate de strontium maintient normaux les principaux paramètres reflétant la minéralisation secondaire, et ses effets sont similaires à ceux de l’alendronate. En conclusion, le ranélate de strontium maintient une qualité normale de la minéralisation secondaire, que ce soit à court ou à long terme, et quel que soit le modèle étudié. Le ranélate de strontium maintient également la microdureté osseuse, les caractéristiques minérales et organique tissulaires, ainsi que la structure du cristal d'apatite / Strontium ranelate, a treatment of postmenopausal osteoporosis, contains 2 atoms of stable strontium which interact with bone mineral. Strontium have a dissociating effect on bone remodeling, decreasing resorption while increasing formation. However, its bone effects are not fully clarified, in particular its interactions with mineral. In monkeys, strontium maintains the major intrinsic properties of bone at a physiological level, either at the global tissue or the bone structural units levels. In postmenopausal women treated with strontium ranelate, the characteristics of apatite crystals are maintained at a physiological level. Moreover, whatever the duration of treatment (2 to 96 months), strontium is always heterogeneously distributed, mainly present in recent bone formed during treatment, bone areas containing strontium progressively increase but less and less with the duration of the treatment. Focal bone strontium content remains stable from 2 to 60 months and then increase from 60 to 96 months, and secondary mineralization is maintained at a physiological level. Finally, after 6 and 12 months of treatment, strontium ranelate maintains normal the main parameters reflecting secondary mineralization, and its effects are similar to those of alendronate. To conclude, strontium ranelate maintains a normal quality of secondary mineralization, either after a shortterm or a long-term treatment, and whatever the model studied. Strontium ranelate also maintains bone microhardness, tissular mineral and organic characteristics, as well as the structure of apatite crystals

Les problèmes de pollution chimique de l'eau sont devenus une source de préoccupation importante et un enjeu prioritaire pour les industriels du nucléaire. L'objectif principal de cette thèse est d'étudier certains minéraux échangeurs ioniques utilisables pour une décontamination liquide en strontium (radioisotope toxique pour l'homme). Mais également de relier les propriétés physico-chimiques de ces matériaux avec leurs propriétés de rétention du radioisotope. Ce mémoire présente donc la synthèse de deux matériaux choisis pour leurs propriétés de sorption spécifique et quantitative du strontium : le nonatitanate de sodium et la zéolithe A. Une seconde partie du travail est dédiée à l'étude des capacités d'échange spécifique de ces matériaux vis-à-vis du strontium en présence d'autres éléments comme le sodium et le calcium. Le nonatitanate de sodium et la zéolithe A ont également été testés sur des effluents réels. Les performances d'un monolithe de zéolithe A ont été évaluées pour un procédé de traitement en colonne. Ce matériau semble prometteur pour la décontamination d'effluents car il permet de cumuler les avantages de la poudre de zéolithe A avec ceux d'un transfert de matière sans perte de charge du solide. / The problems of chemical pollution of water have become a major concern and a priority for the nuclear industry.The aim of this work is to study some ion exchangers used for the removal of strontium ions because 90Sr is one of a major pollutant in nuclear liquid wastes. This study allows linking the physical and chemical properties of these materials and their sorption properties. This work presents therefore the synthesis of two materials - sodium nonatitanate and zeolite A - selected for their specific sorption properties of strontium: A second part of this work is dedicated to the study of specific exchange capacities of these materials for the strontium in presence of other elements such as sodium and calcium. Batch experiments were performed and kinetic and ion exchange models have been applied to understand the selectivity of the materials for strontium removal. Sodium nonatitanate and zeolite A are also studied in actual effluents.Monoliths of zeolite A have been also tested in dynamic ion exchange process. This material is promising for the treatment of radioactive effluents in continuous flow because it joins the sorption properties of the zeolite powder with the advantage of a solid with a macroporous network.

published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

The conservation of freshwater resources is fundamental in supporting modern society and preserving natural habitats and ecosystems. Deterioration of water quality in urban landscapes and loss of municipal water to leaky water distribution infrastructure are two substantial challenges to water-resource sustainability. I examine the geochemistry of streamwater, municipal water, wastewater, soil, and bedrock from the Bull Creek watershed, a rapidly urbanizing watershed in Austin, Texas, to achieve a better understanding of the processes of geochemical evolution as anthropogenically-sourced water recharges natural systems. Urbanization patterns in the Bull Creek watershed have created a contiguous expanse of urban development that covers roughly two thirds of the watershed, whereas the remaining third is rural, enabling direct comparison between urban and rural streamwater from a single watershed. Results indicate that Na, Cl, K, and SO₄ in urban springs and tributaries are elevated more than two-fold in comparison with rural springs and tributaries. A comparison of Sr concentration and Sr isotopic composition for spring and tributary samples indicates that municipal water and wastewater provide a substantial contribution to the urbanized stream branches of Bull Creek. This water is reactive in the subsurface after it leaks from the municipal system, evolving via a pathway of water-rock interaction with limestone. / text

Thesis advisor: Corinne I. Wong / Investigating controls on past variability of South American hydroclimate is critical to assessing its response to future warming scenarios. δ¹⁸O records from South America offer insight into past variability of the South American Monsoon System (SAMS). The controls on precipitation δ¹⁸O values, however, can be decoupled from precipitation amount and thereby limit investigations of variability in local moisture conditions. Here we use a principle components analysis to assess the coherence of speleothem and lake core Holocene δ¹⁸O records in tropical South America to evaluate the extent to which δ¹⁸O variability reflects changes in SAMS intensity at different sites across the region. The main mode of variability across Holocene δ¹⁸O records (PC1) closely tracks austral summertime insolation, consistent with existing work. PC1 is strongly expressed at sites towards the periphery of the continent, while variability at interior sites bear little similarity that implicates controls, in addition to monsoon intensity, on these δ¹⁸O records. Further, we develop speleothem ⁸⁷Sr/⁸⁶Sr records spanning the Holocene from Tamboril Cave (Brazilian Highlands), Paraíso Cave (eastern Amazon Basin), Jaraguá Cave (Mato Grosso Plateau), and Botuverá Cave (Atlantic coastal plain) to investigate coupling between reconstructed monsoon variability and local moisture conditions. Speleothem ⁸⁷Sr/⁸⁶Sr variability is interpreted as a proxy of local moisture conditions, reflecting the degree of water-rock interaction with the cave host rock as driven by variations in water residence time. Speleothem ⁸⁷Sr/⁸⁶Sr records from all the sites, except Botuverá cave, do not co-vary with PC1, suggesting that local moisture conditions do not necessary follow variations in monsoon intensity at these interior sites. These speleothem ⁸⁷Sr/⁸⁶Sr records, however, generally suggest dry mid-Holocene conditions, consistent with interpretations of other paleo-moisture records in the region. These results highlight that dynamics, in addition to SAMS variability, might influence δ¹⁸O variability as well as local moisture conditions at interior sites, and highlight the need for δ¹⁸O-independent reconstructions of moisture conditions. / Thesis (MS) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

O objetivo deste trabalho foi o de otimizar a adição de estrôncio em liga A356 visando obter as melhores propriedades mecânicas de ductilidade. Foram estudados diferentes níveis de adição de estrôncio em ligas A356 com dois níveis de fósforo residual. Além disto, foi estudado o efeito de adições crescentes de magnésio na morfologia do silício em liga Al-7%Si modificada. Para a realização deste estudo, foram produzidos corpos de prova de tração segundo ASTM B108 com velocidade de resfriamento de 8°C/s. Os corpos de prova foram endurecidos por precipitação via tratamento térmico e tracionados. Além de uma avaliação quantitativa das propriedades mecânicas, amostras de todas as condições passaram por uma avaliação metalográfica qualitativa. Foi feito também ataque profundo para observação das morfologias das partículas de silício em microscópio eletrônico. O efeito da adição crescente de estrôncio na liga A356 em um intervalo de 0 a 256 ppm de estrôncio foi o de aumento do alongamento até teores de 50 a 60 ppm, seguido de uma diminuição do mesmo até 256 ppm. O teste de adição crescente de estrôncio foi repetido para uma liga A356 com teor residual de fósforo de aproximadamente 10 ppm. A curva de alongamento segue o mesmo formato da curva levantada para amostras que não continham fósforo, embora tenha sido encontrada uma sensível queda nos valores de alongamento na presença de fósforo. A presença de magnésio em ligas Al-Si modificadas por estrôncio foi responsável por uma mudança na morfologia de crescimento das partículas de silício nas regiões de contornos de células eutéticas, além do aparecimento de partículas intermetálicas nesta mesma região. Deste trabalho, concluiu-se que as melhores propriedades mecânicas de ductilidade foram obtidas para a adição de estrôncio de 50 a 60 ppm. / This work has, as its main objective, the optimization of the strontium addition in A356 alloy, in order to obtain the best ductility results. The addition of several different strontium amounts in alloys containing two phosphorous amounts was studied. Besides, the effect of increasing magnesium content on the morphology of the silicon particles of Al-7%Si modified alloy was also studied. Test bars were produced from ASTM B108 cooled at a rate of 8°C/s. The samples were heat treated and then tested. The mechanical properties were evaluated and the microstructures were analyzed. The silicon morphology was observed in deep etched samples at SEM. Strontium additions of 0 to 256 ppm increased the elongation up to 50-60 ppm. Above 75 ppm, the addition of strontium caused the elongation to decrease up to 256 ppm. The same test was reproduced for an alloy containing approximately 10 ppm P and, although the best results were achieved at strontium additions of 50-60 ppm, the elongation results were clearly lower. The presence of magnesium in Al-7%Si modified alloys was responsible for a change in the growth morphology of the silicon particles, especially near grain boundaries, and also for the formation of intermetallic particles in those areas. From this work, it was possible to conclude that the best ductility properties are achieved for strontium additions of 50-60 ppm.