Made available in DSpace on 2014-10-09T12:36:36Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:10Z (GMT). No. of bitstreams: 1 04131.pdf: 2671874 bytes, checksum: f1aecab51efb7083cb98abad64e8c2ba (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:42:39Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:34Z (GMT). No. of bitstreams: 0 / Neste trabalho se buscou criar uma base tecnológica para síntese digital e visualização virtual de microestruturas de materiais policristalinos monofásicos, visando disponibilizar software e metodologias de baixo custo aos pesquisadores da área ou de áreas correlatas. Para isso foram levantados e testados métodos, sistemas, bibliotecas e algoritmos computacionais pertinentes ao problema em questão. A técnica de síntese escolhida adotou uma simulação física de empacotamento de partículas seguida por tesselação espacial baseada no diagrama Voronoi. Para testar a abordagem uma amostra de um material real foi reconstituída digitalmente. O modelo reproduziu com grande precisão a distribuição de tamanhos de grão, o número de faces por grão e o número de vizinhos imediatos da referência. Na frente de visualização virtual buscou-se definir um modelo capaz de lidar com grandes quantidades de dados e baseado em princípios cognitivos sólidos, que permitisse maior extração de conhecimento de modelos microestruturais. A técnica de visualização em múltiplas escalas foi considerada a mais apropriada aos modelos cujos objetos e detalhes abrangem diversas escalas espaciais, permitindo ao computador lidar com vastas quantidades de dados ao alternar entre qualidade e quantidade no processo de geração de imagens. Técnicas de visualização tradicionais também foram testadas e a técnica de corte se mostrou fundamental, principalmente para a exploração direta do interior do modelo, mas também para a extração de dados voltados a análise microestrutural estereológica. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Master of Science in Biomedical Sciences / Department of Diagnostic Medicine/Pathobiology / Philip R. Hardwidge / Enterotoxigenic Escherichia coli (ETEC) is the most common cause of diarrhea in travellers and young children in developing countries. We previously characterized three vaccine candidates (MipA, Skp, and ETEC_2479) which effectively protected mice in an intranasal ETEC challenge model after immunization. However, these proteins are conserved not only in multiple ETEC isolates, but also in commensal bacteria. In this study, we examined the potential of these antigens to affect the host intestinal microbiota and subsequently found no significant impact on healthy of host after vaccination. In addition, we also optimized the types of adjuvants and forms of antigens and evaluated the efficacy in a mouse intranasal challenge model. Enterohemorrhagic Escherichia coli (EHEC) is an emerging zoonotic pathogen that cause global public health threads. EHEC possesses the potential to cause gastroenteritis, hemorrhagic colitis and hemolytic uremic syndrome (HUS), which may lead to renal failure. Type III secretion system (T3SS) is a hallmark of EHEC, characterized by the needle-like structure and a variety of effectors injected into host cells. NleB, one of T3SS effectors, is a glycosyltransferase with the ability to catalyze the transfer of N-acetyl-D-glucosamine (N-GlcNAc) to host proteins to suppress the activation of NF-kB signaling pathway. In this study, we employed luminescence-based glycosyltransferase assay and high-throughput screening using a chemical library of various compounds. A total of 128 chemicals was selected with significant inhibition on NleB glycosyltransferase activity for further pharmaceutical study as novel therapy against EHEC infection.

Solid oxide fuel cells with graded electrodes consisting of multiple composite layers yield generally lower polarization resistances than single layer composite electrodes. Optimization of the performance of solid oxide fuel cells with graded electrode composition and/or microstructure requires an evaluation of both the three phase boundary length per unit volume and the effective diffusion coefficient in order to provide insight into how these properties vary over the design space. A numerical methodology for studying the three phase boundary length and effective diffusivity in composite electrode layers with controlled properties is developed. A three dimensional solid model of a sintered composite electrode is generated for which the mean particle diameter, composition, and total porosity may be specified as independent variables. The total three phase boundary length for the modeled electrode is calculated and tomographic methods are used to estimate the fraction of this length over which the electrochemical reactions can theoretically occur. Furthermore, the open porosity of the modeled electrode is identified and the effective diffusion coefficient is extracted from the solution of the concentration of the diffusing species within the open porosity. Selected example electrode models are used to illustrate the application of the methods developed, and the resulting connected three phase boundary length and diffusion coefficients are compared. A significant result is the need for thickness-specific effective diffusivity to be determined, rather than the general volume averaged property, for electrodes with porosity between the upper and lower percolation thresholds. As the demand for current increases, more of the connected three phase boundaries become active, and therefore a greater fraction of the electrode layer is utilized for a given geometry, resulting in a higher apparent effective diffusivity compared to the same electrode geometry operating at a lower current. The methods developed in this work may be used within a macroscopic electrode performance model to investigate optimal designs for solid oxide fuel cell electrodes with stepwise graded composition and/or microstructure. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Hanshan Deqing 憨山德清 (1546-1623), est l’un des « Quatre moines bouddhistes éminents » de la fin de dynastie Ming, en Chine qui avaient pris conscience de l’importance et de la nécessité d’une conciliation entre les trois enseignements chinois que sont le bouddhisme, le confucianisme et le taoïsme. Ses annotations du Zhuangzi, du Daode jing, de l’Invariable Milieu et de La Grande Étude demeurent très importantes pour l’étude des tentatives de syncrétisme des trois enseignements. Il fut en effet le premier moine à avoir rédigé autant de commentaires des classiques taoïstes et confucéens afin de montrer que de nombreuses idées de ces deux enseignements d’origine chinoise sont similaires à celles de la pensée bouddhiste. Il est aussi l’auteur d’une dissertation qui démontre la possibilité du rapprochement entre les trois enseignements, tout en maintenant la précellence du bouddhisme. En étudiant de près tous ses commentaires non-bouddhistes et sa dissertation à propos des trois enseignements, nous avons constaté que le moine avait transformé la pensée taoïste et la pensée confucéenne en des doctrines quasi bouddhistes, proches tantôt du Grand Véhicule, tantôt du Petit Véhicule, en fonction des passages examinés. Certains concepts bouddhistes sont très récurrents dans ses commentaires non-bouddhistes. Hanshan Deqing montre que les auteurs des classiques taoïstes et confucéens qu’il annote avaient déjà pressenti l’importance des concepts qui sont au cœur de la pensée bouddhiste et permettent d’atteindre l’illumination ou de conduire des pratiques sotériologiques. À travers ces commentaires, on décèle l’intention de Hanshan Deqing : porter à la connaissance des lettrés, des taoïstes, voire des adeptes bouddhistes eux-mêmes, les procédures permettant d’accéder à l’Éveil, pour ensuite aider d’autres êtres à sortir de leur égarement et de leur attachement au monde. / Hanshan Deqing 憨山德清 (1546-1623) is one of the “Four Eminent Buddhist monks” of the late Ming dynasty in China who realized the importance and the necessity of the reconciliation between the three Chinese philosophies: Buddhism, Confucianism and Taoism. His annotations of the Zhuangzi, of the Daode jing, of the Doctrine of the Mean, of the Great Learning are of seminal importance in the attempt to fusion the three philosophies. He was indeed the first monk to have written so many commentaries of the Taoist and the Confucian classics in order to show that numerous thoughts of these two philosophies originating from China are similar to the ones of Buddhism. He is also the writer of a dissertation that demonstrates the possibility of establishing bridges between the three philosophies, even if he considers Buddhism as superior. Studying closely all his non-Buddhist commentaries and his dissertation about the three philosophies, we noticed that the monk had transformed the Taoist thought and the Confucian thought nearly into Buddhist doctrines, sometimes close to the Mahāyāna, sometimes close to the Hīnayāna, depending on the examined passages. Some Buddhist concepts are very recurrent in his non-Buddhist commentaries. Hanshan Deaing points out that the writers of the Taoist and Confucian classics that he annotates had already sensed the importance of the concepts which are at the heart of the Buddhist mind and enable to reach the enlightenment or the realization of the soteriological practices.Through these commentaries, we can discover Hanshan Deqing’s intention: to make the lettered persons, the Taoists or even the Buddhist disciples themselves aware of the procedures allowing them to reach the Awakening and then to help others beings to be released from their blindness and their attachment to the world.

Abstract The thesis deals with numerical methods designed for the modeling and inversion of geophysical electromagnetic (EM) measurements using a conductive thin plate model. The main objectives are to study the EM induction problem in general and to develop practical interpretation tools for mineral prospecting in particular. The starting point is a linearized inversion method based on the singular value decomposition and a new adaptive damping method. The inversion method is introduced to the interpretation of time-domain EM (TEM) measurements using a thin plate in free-space. The central part of the thesis is a new approximate modeling method, which is based on an integral equation approach and a special lattice model. At first the modeling method is applied to the interpretation of frequency-domain EM (FEM) data using a thin plate in conductive two-layered earth. After this time-domain responses are modeled applying a Fourier-sine transform of broadband FEM computations. The results demonstrate that the approximate computational method can model the geophysical frequency and time-domain EM responses of a thin conductor in conductive host medium with sufficient accuracy, and that the inversion method can provide reliable estimates for the model parameters. The fast forward computation enables interactive interpretation of FEM data and feasible forward modeling of TEM responses. The misfit function mapping and analysis of the singular value decomposition have provided additional information about the sensitivity, resolution, and the correlation behavior of the thin plate parameters.

M.Sc. / Important ideas from dynamical systems theory and the restricted three-body problem are introduced. The intention is the application of dynamical systems theory techniques to the restricted three-body problem to better understand the phenomenon of gravitational capture. Chapter 1 gives a much deeper review of the purpose of this dissertation. Chapter 2 introduces and reviews important concepts from dynamical systems. Chapter 3 reviews the restricted three-body problem and all important aspects of the problem. In chapter 4 we define and study the phenomenon of gravitational capture. We take a novel approach by applying a symplectic method, namely the implicit midpoint method, to model trajectories in the restricted three-body problem. As far as we know, this is the first time such a method has actually been applied, with other authors preferring to apply explicit methods in trajectory modelling. In the closing of this chapter we review our whole discourse and suggest topics for future research. The disseration is concluded with two appendix chapters. In the first chapter we list all the computer code we have written for this dissertation. The second appendix chapter reviews the n-body problem and we show a full solution of the two-body problem.

Ph.D. / In this thesis we undertake a study of formal three-dimensional representational and acceptor methods. In lieu hereof then, we give a short overview of such strategies existing in the literature. Graph and graph grammar theory present us with a powerful two dimensional representational method, and we propose to extend these concepts to the three-dimensional case. We therefore give a short discussion on the theory of graphs and graph grammars. As point of departure, we review the concepts of a structure parameter and structure graph (SG) introduced by us in [BEH,93] and show that these concepts enable us to describe objects in three-dimensional space. We propose various modified graph grammar extensions that generates structure graphs, referred to as Structure Graph Grammar extensions (SGG's) by combining context provisions with the rewriting rules of the various grammar systems. This proposed methodology of ours culminates in the combination of production rule bounded contexts and globally specified contexts, thus defining Structure Graph Grammar extension 7 (SGG-7). We show the applicative value of the three dimensional generative abilities of SGG's by considering the generation of various chemical structural formulae. Brandenburg and Skodinis mentions in [BS,95] that there is a shortcoming in the theory of graph grammars in the sense that in general, there exists no accepting device for graph grammar systems. The following quote from [BS,95,p.336] illustrates this point: "There are no graph automata, which fit to the major classes of graph languages. This is a gap in the theory of graph languages." Regarding the class of languages generated by SGG-7, we propose to fill this gap by introducing an Structure Graph Automaton (SGA) to accept this class of languages.

La télomérase est essentielle pour le maintien des télomères. Elle compense le problème de réplication de l’ADN télomérique par l’ajout de séquences d’ADN aux extrémités des chromosomes. Chez l’humain, elle est très active dans les premiers stades du développement (embryon, fœtus). Puis, son activité est réprimée pour devenir indétectable dans la plupart des cellules. Ceci conduit au raccourcissement de l’ADN télomérique, à la déprotection de l’ADN et à un arrêt de division cellulaire, appelé senescence. Par contre, dans 90% des cellules de type cancéreux, elle est suractivée. Elle contribue donc à une capacité continue de la prolifération de ces cellules et à leur immortalisation. Notre organisme d’étude est la levure bourgeonnante, Saccharomyces cerevisiae. En plus de ses nombreux avantages d’utilisation, chez cette levure, la télomérase est exprimée constitutivement, ce qui signifie qu’elle nous rapproche le plus du contexte de cellule cancéreuse. Mon projet de maîtrise vise à étudier un des composants de la télomérase chez la levure S. cerevisiae, c’est-à-dire la sous-unité ARN, appelée Tlc1, et plus particulièrement une sous-partie de cet ARN, formant une jonction à trois branches (« Three Way Junction »). Jusqu’à présent, cette structure a été considérée comme étant non essentielle. Pourtant, cette structure très conservée a été démontrée comme étant essentielle à l’assemblage de la télomérase et à son activité, chez une grande variété d’espèces. Avec ce projet, j’ai tenté de déterminer si cette structure à trois branches a un quelconque rôle à jouer que ce soit dans l’assemblage ou dans l’activité de la télomérase. J’ai exploré cette structure en y réalisant des mutations et en analysant leurs effets sur la croissance cellulaire et sur la longueur des télomères. Parmi tous les mutants, la simple substitution d’un nucléotide spécifique, l’adénine 119, conduit à des télomères plus courts qui demeurent stables au fil des générations et les levures sont viables. De plus, ce raccourcissement est de l’ordre de la centaine de paires de bases lorsque la délétion d’une partie ou de la structure au complet est réalisée. C’est donc un raccourcissement significatif, représentant près d’un tiers de la longueur normale des télomères. Par ailleurs, sur des cellules présentant des télomères anormalement courts, l’ajout de ces mutations de la TWJ de TLC1 crée un phénotype létal. / Abstract : Telomerase is essential for telomere maintenance. It compensates for the End-replication problem by adding DNA sequences to the ends of chromosomes. In humans, telomerase is very active in the early stages of development (embryos, foetus). Later, its activity is repressed, and in most cells its activity becomes undetectable. This leads to telomere shortening, a deprotection of chromosome ends and to an arrest of cellular divisions, a highly regulated process also called cellular senescence. However, in cancer cells of 90% of all subtypes, telomerase is up-regulated. Hence, this enzyme promotes the proliferative capacity of cancer cells and their immortalization. The budding yeast Saccharomyces cerevisiae is our organism of study. In addition to its ease of access, telomerase is constitutively expressed in this yeast, which makes it a useful and inexpensive model of cancer cells. My master’s project aims at studying one of the telomerase components in S. cerevisiae, namely the RNA subunit Tlc1, and more specifically a part of this RNA, forming a Three-Way Junction (TWJ). So far, this structure was considered as non-essential for cell viability. However, this structure is highly conserved among species, and in diverse species it was shown to be crucial for telomerase assembly and activity. My project hence consisted in trying to determine whether or not this structure plays a role in telomerase assembly or activity. The requirements on this structure were explored by creating mutations and by analyzing their effects on cell growth and telomere length. Of all the mutants, a specific nucleotide substitution, Adenine 119 in the TWJ, leads to shortened telomeres, and this shortening is stable during further outgrowth. Furthermore, a telomere shortening of up to 100 base pairs is observed when a part or the complete TWJ structure is deleted. This shortening is quite significant as it represents about one third of the normal length of telomeres. Moreover, expressing these mutants of the TWJ in cells with short telomeres creates a synthetic lethal effect.

This study investigates learning difficulties involving volumes of solids of revolution (VSOR) at two FET colleges in Gauteng province, in South Africa. The research question for this study was: Why do students have difficulty when learning about volumes of solids of revolution? In order to answer the research question five skill factors were identified as the conceptual framework, subdivided into 11 elements. The five skill factors are: I. Graphing skills and translating between visual graphs and algebraic equations/expressions, II. Three-dimensional thinking, III. Moving between discrete and continuous representations, IV. General manipulation skills and V. Consolidation and general level of cognitive development. Before collecting the main data for this study, a preliminary study and a pilot study were conducted. The data for the main study were then collected in six different investigations. The investigations consisted of two runs of a questionnaire, classroom observations, examination analysis; detailed examination responses and an interview with one student. The results from the questionnaire runs as well as the pilot study reveal that students performed poorly in tasks involving three-dimensional thinking (Skill factor II), moving between discrete and continuous representations (Skill factor III), and consolidation and general level of cognitive development (Skill factor V). Students' performance was satisfactory in tasks involving graphing skills and translating between visual graphs and algebraic equations/expressions (Skill factor I) and general manipulation skills (Skill factor IV). Students were also more competent in solving problems that involved procedural skills than those that required conceptual skills. The challenges that students were faced with in class, evident from the classroom observations allude to the fact that the topic of VSOR is difficult to teach and to learn. It is recommended that VSOR be taught and assessed more conceptually in line with the five skill factors; that curriculum developers must communicate with other stakeholders like industries and other institutions of higher learning and that the Department of Education must provide adequate training for these teachers and liaise with industry in this regard. It is also recommended that the suitability of this topic for the particular cohort of students be reconsidered as it appears to be of too high cognitive demand. / Thesis (PhD)--University of Pretoria, 2012. / Mathematics and Applied Mathematics / unrestricted