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Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 4 uppsatser.

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Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2002. / Härtill 5 uppsatser.

Récemment, dans le domaine de la reconstruction tissulaire, des substituts osseux ou scaffold, ont été utilisés comme alternative aux autogreffes. La complexité de l'ostéogenèse au sein d'une structure poreuse rend son observation expérimentale difficile et par conséquent le développement et l'optimisation des scaffolds sont loin d'être achevés. En complément d'expérimentations animales, il est donc nécessaire de développer des modèles numériques afin de mieux comprendre ce processus. L'objectif de ce travail était de développer un modèle numérique capable de reproduire l'ostéogenèse au sein d'un scaffold poreux en titane, implanté sur la partie non dentée d'une hémimandibule de brebis durant 12 semaines. Cette thèse était donc basée sur une approche à la fois expérimentale et numérique, ce qui constituait l'élément clé du projet. En effet, la plupart des modèles existants n'ont pas été validés expérimentalement ou l'ont été à l'aide d'expérimentations réalisées sur de petits animaux (i.e. lapin, rat) puisque leur taille et leur coût facilitaient le protocole. Néanmoins, contrairement au mouton, leurs processus de régénération osseuse sont très éloignés de celui de l'homme. L'étude a été organisée en trois tâches. Tout d'abord, les expérimentations animales ont été réalisées en collaboration avec le Dr Thomas Schouman (Hôpital de la Pitié-Salpêtrière), et OBL, une PME française fabriquant les scaffolds en titane. Puis, un modèle numérique en éléments finis décrivant l'activité cellulaire au sein du scaffold durant les 12 semaines d'implantation a été conçu. Enfin, des examens histologiques et micro-tomographiques et des tests mécaniques réalisés sur chaque hémimandibule explantée ont permis de: i) quantifier le pouvoir ostéo-conducteur du scaffold en titane et ii) valider le modèle numérique d'ostéogénèse. / Recently, in the tissue reconstruction field, bone substitutes or scaffolds have been used as an alternative to autograft. The complexity of osteogenesis within a scaffold makes its experimental observation difficult and the development and optimization of scaffolds are thus far from being complete. In addition to animal experiments, it is then necessary to develop numerical models to better understand such process. The objective of this work was to develop a numerical model able to reproduce osteogenesis within a porous titanium scaffold implanted on the non-toothed part of a ewe hemimandible for 12 weeks. Therefore, this thesis was based on both an experimental and a numerical approach, which constituted the key element of the project. Indeed, most of the existing models have not been validated or have been validated using experiments performed on small animals (i.e. rabbit, rat) since their size and cost make the protocol easier. Nevertheless, unlike the sheep, their bone regeneration process is quite different from human's. The study was organized into three tasks. First, animal experiments were carried out in collaboration with Dr. Thomas Schouman (Pitié-Salpêtrière hospital) and OBL, a french company manufacturing the porous titanium scaffolds. Then, a numerical model describing cellular activity within the scaffold during the 12 weeks of implantation was developed. Finally, histological and micro-tomographic analyses and mechanical tests performed on each hemimandible have enabled to: i) quantify the osteoconductive potential of the scaffold and ii) validate the numerical results.

A key challenge of the learning sciences is moving research results into practice. Educators on the front lines perceive little value in the outputs of education research and demand more “usable knowledge”. This work explores the potential instead of usable artifacts to translate knowledge into practice, adding scientists as stakeholders in an interaction design process. The contributions are two effective systems, the scientific and contextual principles in their design, and a research model for scientific research through interaction design. College student study practices are the domain chosen for the development of these methods. Iterative ethnographic fieldwork identified two systems that would be likely to advance both learning in practice and knowledge for applying the employed theories in general. Nudge was designed to improve students’ study time management by regularly emailing students with explicit recommended study activities. It reconceptualizes the syllabus into an interactive guide that fits into modern students' attention streams. Examplify was designed to improve how students learn from worked example problems by modularizing them into steps and scaffolding their metacognitive behaviors though problem-solving and self-explanation prompts. It combines these techniques in a way that is exceedingly easy to author, using existing answer keys and students' self-evaluations. Nudge and Examplify were evaluated experimentally over a full semester of a lecture-based introductory chemistry course. Nudge messages increased students’ sense of achievement and interacted with students’ existing time management skills to improve exam grades for poorer students. Among students who could choose whether to receive them, 80% did. Students with access to Examplify had higher exam scores (d=0.26), especially on delayed measures of learning (d=0.40). A key design decision in Examplify was not clearly resolvable by existing theory and so was tested experimentally by comparing two variants, one without prompts to solve the steps. The variant without problem solving was less effective (d=0.77) and less used, while usage rates of the variant with problem solving increased over time. These results support the use of the design methods employed and provide specific empirical recommendations for future designs of these and similar systems for implementing theory in practice.