Social and environmental justice for a growing and developing global population requires significant increases in energy use. A possible means of contributing to this energy increase is to incinerate plutonium from spent fuel of pressurised light water reactors (Pu(PWR)) in high-temperature reactors such as the Pebble Bed Modular Reactor Demonstration Power Plant 400 MWth (PBMR-DPP-400). Previous studies showed that at low temperatures a 3 g Pu(PWR) loading per fuel sphere or less had a positive uniform temperature reactivity coefficient (UTC) in a PBMR DPP-400. The licensing of this fuel design is consequently unlikely. In the present study it was shown by diffusion simulations of the neutronics, using VSOP-99/05, that there is a fuel design containing thorium and plutonium that achieves a negative maximum UTC. Further, a fuel design containing 12 g Pu(PWR) loading per fuel sphere achieved a negative maximum UTC as well as the other PBMR (Ltd.) safety limits of maximum power per fuel sphere, fast fluence and maximum temperatures. It is proposed that the low average thermal neutron flux, caused by reduced moderation and increased absorption of thermal neutrons due to the higher plutonium loading, is responsible for these effects. However, to fully understand the mechanisms involved a detailed quantitative analysis of the roll of each factor is required. A 12 g Pu(PWR) loading per fuel sphere analysis shows a burn-up of 180.7 GWd/tHM which is approximately double the proposed PBMR (Ltd.) low enriched uranium fuel burn-up. The spent fuel has only a decrease of 24.5 % in the Pu content which is sub-optimal with respect to proliferation and waste disposal objectives. Incinerating Pu(PWR) in the PBMR-DPP 400 MWth is potentially licensable and economically feasible and should be considered for application by industry. / MIng (Nuclear Engineering), North-West University, Potchefstroom Campus, 2012

The increasing growth of mobile devices in the whole world, and the forecasts for the coming years has been indicated by several reports. Nonetheless, this need for ubiquitous collaboration has brought new possibilities and challenges to the scientific community. Mobile Ad hoc Networks (MANETs) emerges in this scenario allowing devices to interconnect autonomously, without the need of a fixed infrastructure, in order to provide communication and information services. Due to such decentralization and the natural constraints of mobile devices, it remains, to this day, a challenge to provide efficient routing for MANETs. In this dissertation we propose new routing enhancements based on policies for MANETs running the HTR protocol. We consider the role(s) a user associated to a device performs within an organization. Hence our policies can guide the routing based on these roles. With this scheme we improve communication according to different business needs and scenario requirements. To this end, we propose a set of policies that affects the routing behavior and present four case studies to present each policy. Then we analyze two policies in terms of end-to-end delay, and nodes’ lifetime. Through simulation we evaluate these metrics while varying parameters such as the amount of nodes participating in the network, the mobility characteristics, and the number of traffic sources. Our results show that it is possible to achieve these goals without causing great impact on the average end-to-end delay and energy consumption, two important metrics in any MANET evaluation. We explore the results in several scenarios and detail our findings, which can provide a different perspective for future MANET applications. / Submitted by João Arthur Martins (joao.arthur@ufpe.br) on 2015-03-10T18:42:15Z No. of bitstreams: 2 Dissertação Gabriela Coutinho.pdf: 1701782 bytes, checksum: 113328c2efdd1ba97f7a237d03cab574 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-11T17:46:06Z (GMT). No. of bitstreams: 2 Dissertação Gabriela Coutinho.pdf: 1701782 bytes, checksum: 113328c2efdd1ba97f7a237d03cab574 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2013-09-13 / O crescimento das vendas de aparelhos móveis em todo o mundo, bem como as previsões para os próximos anos são apontadas em diversos relatórios. No entanto, essa necessidade de colaboração ubíqua trouxe novas possibilidades e desafios para a comunidade científica. Redes móveis ad hoc (Mobile Ad hoc Networks - MANETs) surgem diante deste cenário e permite que dispositivos se comuniquem de forma autônoma, sem a necessidade de uma infraestrutura predefinida para fornecer comunicação e serviços. Porém, essa descentralização junto com as restrições naturais dos dispositivos móveis, proporcionar roteamento eficiente para MANETs permanece um desafio. Este trabalho propõe novas melhorias para o roteamento em MANETs que utilizam o protocolo HTR. Também considera o papel que usuários associados aos dispositivos desempenham dentro de uma organização. Desta forma, as políticas desenvolvidas podem guiar o roteamento também com base nestes papéis. Com este esquema, é possível melhorar a comunicação de acordo com necessidades de negócio e requerimentos de cenário. Para este fim, esta dissertação propõe um conjunto de políticas que afetam o comportamento do roteamento e analisa os impactos em termos de atraso, energia gasta e tempo de vida dos nós. Através de simulações, essas métricas são avaliadas também com variação de parâmetros como a quantidade de nós que participam da simulação, as características de mobilidade e o número de fontes de tráfego. Resultados mostram que é possível atingir esses objetivos sem causar grande impacto negativo no atraso fim a fim e no consumo de energia, duas métricas importantes em avaliações de redes MANET. Nós exploramos esses resultados em diversos cenários e detalhamos nossas descobertas, que podem servir como uma perspectiva diferente para futuras aplicações de redes MANET.

Les télomères sont raccourcis à chaque cycle de réplication de l’ADN à cause du problème de réplication des extrémités. Leur longueur dicte la capacité proliférative des cellules eucaryotes. Des télomères trop courts, aillant atteints la limite de Hayflick, feront entrer les cellules en sénescence réplicative. Pourtant dans les cellules progénitrices ainsi que 90% des cellules cancéreuses la longueur des télomères est maintenue par un complexe ribonucléoprotéique, la télomérase. L’assemblage de ce complexe ainsi que son recrutement aux télomères son des processus dynamiques sous le contrôle d’une régulation fine. Toutefois, comment cette régulation à un impact sur la dynamique de la télomérase dans le noyau n’est toujours pas complétement compris. Dans ce projet nous avons développé une nouvelle méthode se basant sur le système MS2 permettant d’observer pour la première des particules uniques d’ARN de télomérase (hTR) par microscopie à fluorescence sur cellules cancéreuse humaines vivantes. Le suivi en temps réel de ces particules aux télomères a permis de révéler que la télomérase scanne activement les télomères via des interactions courtes avec la protéine télomérique TPP1. Des interactions plus stables nécessaires à l’allongement des télomères peuvent être formées grâce à l’appariement entre hTR et l’ADN simple brin du télomère sous contrôle du domaine OB-fold de la protéine télomérique POT1. Le suivi de ces particules au cours du cycle cellulaire a révélé que ces interactions ne sont pas restreintes à la phase S, la phase d’élongation des télomères. La mesure de la dynamique de hTR dans les corps de Cajal (CBs) couplé à des expériences de photo-activation ont pu montrer que hTERT joue un rôle dans la sortie de hTR des CBs. Enfin des mesures d’intensités de fluorescence de hTR aux télomères montrent qu’une seule particule est recruté sur un télomère en phase S. / Telomeres are shortened at each DNA replication cycle, due to the end replication problem. Their length dictates the proliferative capacity of eukaryotic cells. Too short telomeres, reaching the Hayflick limit, will lead the cells to replicative senescence. However, in stem cells and 90% of cancer cells telomere length is maintained by a ribonucleoproteic complex named telomerase. The assembly of this complex and its recruitment to telomeres are process under a fine regulation. Yet, how this regulation impacts the nuclear dynamics of telomerase is not fully understood. In this project, we developed a new method based on the MS2 system to image for the first time telomerase RNA (hTR) particles in living human cancer cells by fluorescence microscopy. The real time tracking of these particles at telomeres revealed that telomerase actively scan all telomeres by short interactions with the TPP1 shelterin protein. Long stable interaction needed for telomere elongation can be made by the pairing of hTR template and single stranded telomeric DNA under the control of the OB-fold domains of the shelterin protein POT1. By tracking telomerase particle during the cell cycle, we revealed that telomerase recruitment to telomeres is not restricted to S phase, when telomeres are elongated. By measuring the dynamics of hTR in Cajal bodies (CBs) with photo-activation and photo-bleaching technics we showed that hTERT play a role in the hTR exit from CBS. Finally, fluorescence intensity measures of hTR at telomeres showed the recruitment of only one particle on a telomere.

Where there has been a steady development of Optical Character Recognition (OCR) techniques for printed documents, the instruments that provide good quality for hand-written manuscripts by Hand-written Text Recognition  methods (HTR) and transcriptions are still some steps behind. With the main focus on historical ciphers (i.e. encrypted documents from the past with various types of symbol sets), this thesis examines the performance of two machine learning architectures developed within the DECRYPT project framework, a clustering based unsupervised algorithm and a semi-supervised few-shot deep-learning model. Both models are tested on seen and unseen scribes to evaluate the difference in performance and the shortcomings of the two architectures, with the secondary goal of determining the influences of the datasets on the performance. An in-depth analysis of the transcription results is performed with particular focus on the Alchemic and Zodiac symbol sets, with analysis of the model performance relative to character shape and size. The results show the promising performance of Few-Shot architectures when compared to Clustering algorithm, with a respective SER average of 0.336 (0.15 and 0.104 on seen data / 0.754 on unseen data) and 0.596 (0.638 and 0.350 on seen data / 0.8 on unseen data).

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