En matière de santé bucco-dentaire, la lutte contre les maladies parodontales est un objectif majeur. Ces maladies infectieuses d’origine multifactorielle, ayant comme étiologie principale le biofilm bactérien bucco-dentaire et se traduisant cliniquement par la formation d’une poche par destruction progressive du système d’attache de la dent, sont la cause de 30 à 40 % des extractions dentaire. C’est dans ce contexte que nous avons cherché à réaliser un dispositif résorbable à libération prolongée d’agents anti-infectieux à partir d’un support en cellulose, qui à terme pourraient servir de thérapeutique complémentaire en parodontologie. Le procédé choisi pour rendre la cellulose biorésorbable a consisté à oxyder les fonctions hydroxyles primaires de celle-ci en fonctions carboxyliques. Le phénomène de libération prolongée a quant à lui été obtenu par la fixation de cyclodextrines et de dextrines sur cette cellulose oxydée. Une fois le procédé et les paramètres de fonctionnalisation établis, des études de libération prolongée d’un agent antiseptique, le digluconate de chlorhexidine, ont été menées. De même, des études, in vitro, biologiques et microbiologiques ont été réalisées afin de vérifier l’innocuité de notre système mais également son effet antibactérien sur les principales bactéries associées à ces maladies. Nous avons montré que nos supports fonctionnalisés présentaient un réel intérêt en tant que thérapeutique complémentaire en parodontologie.. / In the field of dental health, the fight against gum disease is a major objective. These infectious diseases have many causative factors. Principle among these is the formation of biofilms by bacteria residing on the teeth and gums which in turn lead to the formation of a “periodontal pocket", where infection occurs at the gum / tooth interface. The issue is that teeth are progressively destroyed by encroaching bacteria. This accounts for 30-40% of tooth extractions performed in the world.In this context we have endeavoured to develop a biodegradable device for the prolonged release of antibacterial agents from a cellulose support, which in time should be adopted as a viable periodontological therapy.The process selected to create the biodegradable cellulose support consists of oxidation of the primary alcohol group of cellulose. The phenomenon of prolonged antibacterial agent release was obtained by the fixation of cyclodextrins and dextrins to this oxidised cellulose. The macromolecular parameters of the fully fabricated devices were established and studies of the duration of the prolonged release of chlorhexidine digluconate were performed. Furthermore biological and microbiological studies were carried out in vitro to verify the biocompatibility (non cytotoxicity) and antibacterial efficacy respectively, of our system. We have shown that our functionalised supports present a novel, effective device for use in periodontological therapy.

Bjälklag av förspända håldäckselement (HD/F) är en kostnadseffektiv lösning för byggnader med stora spännvidder där öppen planlösning eftersträvas. Den ursprungliga konstruktionen för byggnader bestod av HD/F-element och väggar som upplag. Senare blev användning av balkar som upplag allt vanligare lösning. Balkar kallas i det fallet för flexibla upplag. Den här konstruktionslösningen i sig medför sämre bärförmåga hos HD/F-element eftersom balken deformeras vid belastning, och på grund av samverkan mellan balk och HD/F-element uppstår tillkommande spänningar i håldäckselement.   Det här arbetet hade som syfte att undersöka på vilka sätt försämrad bärförmåga hos HD/F-element tas hänsyn till och hur det kan tillämpas vid dimensionering. Detta resulterade i ett beräkningexempel enligt en av de olika beräkningsmodeller som finns. I beräkningasexemplet behandlas bjälklag i ett parkeringshus, och resultatet visar att bjälklaget håller för belastningen med hänsyn till flexibla upplag. / Floor structures constructed by using prestressed precast hollow-core slabs is costeffective solution for buildings that require long span floors. Nowadays the most common design for this type of floors consists of HC slabs supported on beams. In this case beams are called flexible supports because of deflection in the beams. These deflections cause addition stresses in the HC slabs that has to be taken into accout. The purpose of this study was to find out which calculation models exist and how they can be used in design process. As s result of project a calculation example is presented in this report which describes one of possible calculation models.

Les cellules adhérentes, dont les cellules souches, sont très prometteuses pour de nombreuses applications dans le domaine des biotechnologies. Toutefois, leur culture représente un défi puisque les méthodes enzymatiques et mécaniques, couramment utilisées pour l’étape de détachement du support de culture, présentent des inconvénients majeurs. Le but de ce travail de thèse a été de développer un support pour la culture de cellules adhérentes permettant leur détachement par modification de la température. Pour cela, nous avons produit des échantillons thermo-associatifs de xyloglucane, un polysaccharide naturel, par réaction avec une enzyme, la ß-galactosidase. Les échantillons obtenus ont été caractérisés par rhéologie, viscosimètrie, diffusion de la lumière et chromatographie par perméation de gel. Nous nous sommes aussi intéressés à l’évaluation de méthodes de stérilisation efficaces capables de préserver les propriétés du polymère. De plus, afin de rendre ce polymère bioadhésif, nous avons étudié son activation et sa fonctionnalisation par un peptide contenant le motif arginine-glycine-aspartate (RGD). Nous avons montré que des cellules modèles A375 surexprimant le récepteur pour le RGD sont capables d’adhérer et de proliférer à 37°C sur des films formés à partir de xyloglucane modifié par du RGD. Leur détachement est possible à température ambiante. L'utilisation de ce nouveau support pour la culture de cellules souches embryonnaires humaines, la production d’un système pour la libération contrôlée de facteurs de croissance ainsi que la conception de billes de taille micrométrique à base de xyloglucane font partie des perspectives de cette thèse. / Adherent cells, including stem cells, hold great promise for many applications in biotechnology. However, cell detachment from standard culture surfaces remains a challenging task since both commonly used enzymatic and mechanical methods have major drawbacks. The aim of my PhD work was to develop a thermoresponsive culture surface supporting cell attachment and survival while enabling a temperature-assisted cell detachment. In order to achieve this goal, thermoresponsive xyloglucan was initially produced by partial galactose removal after reaction with the β-galactosidase enzyme. Samples were characterized by rheology, viscosimetry, light scattering analysis and size-exclusion chromatography. We were also interested in evaluating sterilization methods and their effect on the properties of the polymer. Additionally, in order to obtain a bioadhesive polymer from partially degalactosylated xyloglucan, we studied its functionalization with a peptide containing the arginine-glycine-aspartate (RGD) groupment motif. We have shown that A375 model cells overexpressing the RGD receptor were able to adhere and proliferate at 37 °C on xyloglucan-derived films grafted with RGD and their detachment at room temperature was also demonstrated. The culture of human embryonic stem cells, as well as the introduction of a controlled release system for growth factors and the development of thermoresponsive beads for cell culture comprise the perspectives of this thesis.

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Th. univ.--Chimie--Paris 6, 1994. / 1994 d'après la déclaration de dépôt légal. Bibliogr. p. 169-176. Résumé en français et en anglais.

L’objectif de cette étude, portée sur une solution catalytique hétérogène, est de rechercher les meilleures propriétés texturales de supports siliciques pour améliorer les performances catalytiques des solides Pt/SiO2. Des travaux rapportés en littérature ont étudiés les paramètres qui influencent la réduction catalytique des ions nitrites et nitrates en fonction de la nature du support catalytique utilisé, les métaux nobles, l’agent réducteur ou l’influence de pH de la solution. Dans ce travail, le paramètre de diffusion de catalyseur est étudié afin d’améliorer l’accessibilité aux sites actifs pour favoriser la conversion des ions nitrite en azote en évitant la production des ions d’ammonium. Pour atteindre cet objectif, des silices à porosité hiérarchisée sont élaborées en adaptant une méthode par double structuration permettant un contrôle indépendant des diamètres de pores. Ainsi, en ajustant simplement la taille des billes de polymères (entre 400 et 50nm), il est possible de générer des macropores ou de larges mésopores. En couplant ces objets avec un surfactant non ionique (P123) comme agent structurant, des supports siliciques à double porosité, présentant des volumes poreux bien supérieurs aux supports parents ont été obtenus. Les supports ont été imprégnés par le précurseur de Platine par voie humide et calcinés sous air, afin d’obtenir 1% en masse de catalyseur. / The aim of this work focused on a heterogeneous catalytic solution to seek the best textural properties of silicic materials to improve the catalytic performance of Pt/SiO2 solids. Many works were reported in the literature have examined parameters influencing the catalytic reduction of nitrate and nitrite ions as the nature of the catalytic support used , the noble metal , the reducing agent or the influence of solution pH . In this work, the diffusion parameter of catalyst was studied in order to improve the accessibility to the active sites to promote the conversion of nitrite to nitrogen ions avoiding the production of ammonium ions. To achieve this objective, silica materials with hierarchical porosity are developed by adapting the dual templating method to give an independent control of pore diameters. Thus, by simply adjusting the size of the polymer beads (between 400 and 50 nm); it is possible to generate large mesopores and macropores. By combining these objects with a nonionic surfactant (P123) as a structuring agent, with dual porous silicic supports were obtained with pore volumes higher than the parent supports. The supports were impregnated with platinum precursor by wet route and calcined in air to obtain 1% by weight of catalyst.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. October 2013. Johannesburg, South Africa. / We report the role of a double step heat treatment process in the synthesis of novel GaN nanostructures (NSs) using a two stage furnace following a catalyst free vapour-solid growth mechanism. Morphological analysis revealed that GaN NSs were composed of rod-like structures with average diameter of 250 nm and accumulated particulates of GaN with diameter of ~ 12 – 16 nm providing enhanced surface area. The wurtzite phase of GaN nanorods of agglomerated nanoclusters was synthesized at temperatures as low as 750 °C. An X-ray photoelectron spectroscopic study confirmed formation of GaN. The surface areas of the GaN NSs were high at ~20 m2/g with respect to that expected for solid nanorod structures. The GaN NSs were of high crystallinity and purity as revealed by structural studies. Raman spectral analysis showed stronger intensity of the A1(LO) mode with respect to that for E2(high) mode indicating the high electronic quality of the sample. A photoluminescence study revealed the dominant presence of a defect band around 1.7-2.1 eV corresponding to nitrogen di-vacancies. Subsequent annealing in NH3 has demonstrated a compensation of the defect state and evolution of a band edge peak with possible hydrogen compensation of surface states. We also report the role of activated carbon on Ga2O3 to make GaN/C nanostructure composites using a single stage furnace. TEM analysis showed that GaN/C nanostructures gave different morphologies with different ratios of GaN/C. The surface areas of these materials showed an increase as the ratio of activated carbon was increased. PXRD showed that a ratio of Ga2O3: C of 1:0.5 (w/w) was sufficient to form GaN. TGA revealed that the ratios of Ga2O3: C of 1:0.5 – 1:2 gave materials that were thermally stable. Raman spectra showed that the material had excellent electronic properties. The material with a Ga2O3/C 1:2 ratios showed a poor gas response due to the change in reference value of resistance with the variation of hydrogen concentration. iv This study also provides the first investigation of GaN as a catalyst support in hydrogenation reactions. The GaN NSs were synthesized via chemical vapour deposition (CVD) in a double stage furnace (750 ºC) while nitrogen doped carbon spheres (NCSs) were made by CVD in a single stage furnace (950 ºC). TEM analysis revealed that the GaN NSs were rod-like with average diameters of 200 nm, while the NCSs were solid with smoother surfaces, and with diameters of 450 nm. Pd nanoparticles (1 and 3% loadings) were uniformly dispersed on acid functionalized GaN NSs and NCSs. The Pd nanoparticles had average diameters that were influenced by the type of support material used. The GaN NSs and NCSs were tested for the selective hydrogenation of cinnamaldehyde in isopropanol at 40 and 60 °C under atmospheric pressure. A comparative study of the activity of the nanostructured materials revealed that the order of catalyst activity was 3% Pd/GaN >3% Pd/NCSs > 1% Pd/NCSs > 1% Pd/GaN. However, 100% selectivity to hydrocinnamaldehyde (HCALD) was obtained with 1% Pd/GaN at reasonable conversion rates.

Each year 300 million people ride roller coasters at amusement parks across the United States. Although they are meant for joy and entertainment, the design is very crucial and regulated. Understanding the interaction between components and humans can help create a more thrilling and safer ride. This study researched the design of the course and the structural supports. A unique roller coaster was designed, investigating the relationship between velocity and G forces. With the profile design complete, the corresponding forces resulting from the track and train weight and train movement were calculated to determine the required dimensions of the structural support columns. This work investigated the relationship between the features of the roller coaster and the material properties of the structural supports, determining which are most impactful for the loading conditions. These results can be used to determine the required properties of a roller coaster’s structural system to maximize the material usage to minimize resources and cost.

Thèse de doctorat : Électrochimie : Strasbourg : 2009. / Titre provenant de l'écran-titre. Bibliogr. 10 p.

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