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Thèse (Ph. D.)--Université Laval, 2004. / Titre de l'écran-titre (visionné le 28 novembre 2005). Bibliogr.

<p>Autonomous robots typically rely on internal representations of the environment, or maps, to plan and execute their tasks. Several types of maps have been proposed in the literature, and there is general consensus that different types have different advantages and limitations, and that each type is more suited to certain tasks and less to others. Because of these reasons, it is becoming common wisdom in the field of mobile robotics to use hybrid maps that integrate several representations, usually of different types. Hybrid maps provide scalability and multiple views, allowing for instance to combine robot-centered and human-centered representations. There is, however, little understanding of the general principles that can be used to combine different maps into a hybrid one, and to make it something more than the sum of its parts. There is no systematic analysis of the different ways in which different maps can be combined, and how they can be made to cooperate. This makes it difficult to evaluate and compare different systems, and precludes us from getting a clear understanding of how a hybrid map can be designed or improved.</p><p>The investigation presented in this thesis aims to contribute to fill this foundational gap, and to get a clearer understanding of the nature of hybrid maps. To help in this investigation, we develop two tools: The first one is a conceptual tool, an analytical framework in which the main ingredients of a hybrid map are described; the second one is an empirical tool, a new hybrid map that allows us to experimentally verify our claims and hypotheses.</p><p>While these tools are themselves important contributions of this thesis, our investigation has resulted in the following additional outcomes:</p><p>• A set of concepts that allow us to better understand the structure and operation of hybrid maps, and that help us to design them, compare them, identify their problems, and possibly improve them;</p><p>• The identification of the notion of synergy as the fundamental way in which component maps inside a hybrid map cooperate.</p><p>To assess the significance of these outcomes, we make and validate the following claims:</p><p>1. Our framework allows us to classify and describe existing maps in a uniform way. This claim is validated constructively by making a thorough classification of the hybrid maps reported in the literature.</p><p>2. Our framework also allows us to enhance an existing hybrid map by identifying spots for improvement. This claim is verified experimentally by modifying an existing map and evaluating its performance against the original one.</p><p>3. The notion of synergy plays an important role in hybrid maps. This claim is verified experimentally by testing the performance of a hybrid map with and without synergy.</p>

Iterative decoding and codes on graphs were first devised by Gallager in 1960, and then rediscovered by Berrou, Glavieux and Thitimajshima in 1993. This technique plays an important role in modern communications, especially in coding theory and practice. In particular, low-density parity-check (LDPC) codes, introduced by Gallager in the 1960s, are the class of codes at the heart of iterative coding. Since these codes are quite general and exhibit good performance under message-passing decoding, they play an important role in communications research today. A thorough analysis of iterative decoding systems and the relationship between maximum a posteriori (MAP) and belief propagation (BP) decoding was initiated by Measson, Montanari, and Urbanke. This analysis is based on density evolution (DE), and extrinsic information transfer (EXIT) functions, introduced by ten Brink. Following their work, this thesis considers the MAP decoding thresholds of three iterative decoding systems. First, irregular repeat-accumulate (IRA) and accumulaterepeataccumulate (ARA) code ensembles are analyzed on the binary erasure channel (BEC). Next, the joint iterative decoding of LDPC codes is studied on the dicode erasure channel (DEC). The DEC is a two-state intersymbol-interference (ISI) channel with erasure noise, and it is the simplest example of an ISI channel with erasure noise. Then, we introduce a slight generalization of the EXIT area theorem and apply the MAP threshold bound for the joint decoder. Both the MAP and BP erasure thresholds are computed and compared with each other. The result quantities the loss due to iterative decoding Some open questions include the tightness of these bounds and the extensions to non-erasure channels.

Les patients décrits initialement par J. Noonan se ressemblent et ont une cardiopathie congénitale : soit une sténose valvulaire pulmonaire (SVP), soit une persistance du canal artériel. Avant la découverte du premier gène responsable de ce qui est devenu le syndrome de Noonan, cinq études de cohortes décrivant ces patients ont répertorié la prévalence de SVP mais le spectre des cardiopathies semble large, n’a pas été décrit de manière exhautive et aucune hypothèse n’est émise ou ne fait de lien entre ces différentes manifestations cardiaques et une compréhension intégrée du développement embryonnaire. Le gène PTPN11 est le premier gène identifié chez 40% de ces patients. Une corrélation existe entre la présence d’une mutation et la survenue de SVP de même qu’entre l’absence de mutation et la présence d’une cardiomyopathie hypertrophique. Six études de cohortes ont repris la description des mutations identifiées au sein du gène PTPN11 et les phénotypes associés, mais les cardiopathies n’ont pas été systématiquement ou spécifiquement analysées (tant au sein des groupes de patients porteurs de mutation que de ceux sans mutation). Le syndrome LEOPARD est allélique du syndrome de Noonan depuis que des mutations spécifiques au sein des exons 7,12 et 13 du gène PTPN11 ont été identifiées chez 95% des patients. Afin d’appréhender les implications possibles du gène PTPN11 dans la survenue des cardiopathies chez les patients porteurs de ces deux syndromes, nous avons conduit une étude chez 272 patients au syndrome de Noonan et une étude chez 19 patients porteurs du syndrome LEOPARD. Parmi la cohorte de patients atteints du syndrome de Noonan, 104 ont été diagnostiqués porteurs d’une mutation du gène (38%). Une prévalence de survenue de cardiopathies affectant les structures droites du cœur se dégage chez les patients identifiés porteurs d’une mutation avec une différence significative pour la SVP, une tendance est relevée pour le canal atrio-ventriculaire et la communication inter-auriculaire de type Ostium Secundum. L’absence de mutation est corrélée avec la survenue de cardiomyopathie hypertrophique et de cardiopathies du cœur gauche. Parmi les patients atteints du syndrome LEOPARD, il n’existe pas de différence statistiquement significative pour les patients porteurs d’une mutation ou non et/ou pour une cardiopathie particulière. Toutes les mutations identifiées du gène PTPN11 sont des mutations ‘faux-sens’. Ce gène appartient à la famille des gènes codant pour une protéine tyrosyl phosphatase, SHP-2, ne possédant pas de récepteur trans-membranaire. Cette phosphatase est impliquée dans la voie de signalisation cellulaire des MAP (‘Mitogen-activated protein’) kinases dont l’expression est ubiquitaire et inclut le coeur. Depuis nos travaux, le concept de syndrome « neuro-cardio-facio-cutané » est établi puisque, à ce jour, 9 gènes (SOS1, RAF1, BRAF, KRAS, NRAS, HRAS, NF1, SPRED1 et SHOC2), tous impliqués dans la voie de signalisation RAS (voie des MAP kinases) sont identifiés. Un spectre phénotypique existe avec des signes communs mais aussi distinctifs chez les patients présentant le syndrome de Noonan, le syndrome LEOPARD, le syndrome de Costello, le syndrome Cardio-Facio-Cutané (CFC), le syndrome « Noonan-NF1 », le syndrome de Legius et le syndrome « Noonan/Multiple Giant Cell Lesion ». Nous rapportons enfin l’observation d’une patiente atteinte du syndrome CFC et porteuse d’une mutation (p.R257Q) au sein du gène BRAF ayant développé une cardiomyopathie hypertrophique. Ces travaux de cohortes de patients au phénotype du syndrome de Noonan, du syndrome LEOPARD et cette dernière description d’une patiente au syndrome CFC ont permis de participer à la découverte de l’implication d’une voie de signalisation cellulaire dont l’origine génétique est maintenant démontrée. Les résultats de nos travaux réalisés depuis 2002 auront permis, avec les équipes travaillant sur le même sujet, d’orienter les investigations et les nouveaux projets de recherche qui étudient spécifiquement le rôle du gène PTPN11 dans l’embryologie du cœur. Les études des orthologues (zebrafish, murin et Drosophila) porteurs à l’état hétérozygote d’une mutation du gène PTPN11 permettent d’intégrer les anomalies phénotypiques et cardiaques observées. Ces études permettent de postuler les effets cellulaires produits par les mutations chez les patients atteints du syndrome de Noonan et chez les patients atteints du syndrome LEOPARD engendrant in vitro une activation de la phosphatase (effet « gain de fonction ») pour les premiers ou une réduction de l’activité phosphatase (« dominant négatif ») mais engendrant un effet gain de fonction in vivo. Nous discutons les connaissances acquises, les compréhensions obtenues et intégrées et traçons enfin les perspectives offertes par ces travaux.

Vaccination is one of the major strategies available for combating viral infections in humans. However, currently available vaccines are not without pitfalls; they are laborious to produce, could potentially be unsafe, and in the case of the highly variable influenza virus need to be reformulated each season. The use of synthetic peptides thus represents an exciting alternative to traditional vaccines. However, these synthetic peptides are not highly immunogenic without the use of potent adjuvants. The lack of immunogenicity might be addressed by conjugation between T or B cell epitopes with universal or immunodominant T-helper epitopes. The construction of branched peptides, lipidated peptides, or designs combining both of these elements might also enhance the immunogenicity, as they might target Toll-like receptors and/or mimic the 3-dimensional structure of epitopes within the native protein. In this study, a recognized T-B peptide based on the hemagglutinin protein of the A/Puerto Rico/8/34 influenza virus was chosen as a backbone and modified to evaluate if the construction of branched peptides, lipidation, the addition of cysteine residues, or mutations could indeed alter reactivity. Screening the different designs with various antibody binding and cellular assays revealed that combining a branched design with the addition of lipid moieties leads to a greatly enhanced activity as compared to other similar T-B diepitope constructs.

In a large scale environment humans rely on their mental representations cognitive maps to solve navigational problems. To approach the understanding of how humans acquire, process, and utilize information from the environment, three groups of participants in this study performed several experiments associated with finding their way in a previously unknown environment. Experimental tasks included route retracing, pointing to previously visited locations, and a questionnaire regarding wayfinding strategies and cognitive map development. Each of three groups of participants was in one of three unique conditions: 1. learning and retracing with navigational landmarks indicating right and left turns at decision points; 2. during route retracing only generic landmarks were present at decision points (landmarks indicating left and right were present during learning but replaced during retracing); and 3. no landmarks were present during route retracing (landmarks indicating left and right were present during learning but removed before retracing started). Results supported the hypothesis that during the initial stages of visiting an unknown environment we build metric knowledge together with non-metric knowledge associated with the broad categories of landmark and route knowledge. In addition, the environment plays an important role in wayfinding performance and that characteristics of the environment contribute differently to the development of our cognitive map. Last but not least, the strategies humans use to solve wayfinding problems in a novel environment are not based on an individual type of environmental knowledge; in fact, we switch between different types of environmental knowledge when necessary. Shifting between strategies appears to be from more familiar environmental knowledge to less familiar knowledge. In particular, participants from group 3 (no landmarks during the retracing period) were more likely to walk off-route during retracing but exhibited more accurate metric knowledge of the environment. Based on the results of this experiment, they combined route- and survey-based strategies in wayfinding and switched from the most familiar knowledge to a less familiar strategy.

Vaccination is one of the major strategies available for combating viral infections in humans. However, currently available vaccines are not without pitfalls; they are laborious to produce, could potentially be unsafe, and in the case of the highly variable influenza virus need to be reformulated each season. The use of synthetic peptides thus represents an exciting alternative to traditional vaccines. However, these synthetic peptides are not highly immunogenic without the use of potent adjuvants. The lack of immunogenicity might be addressed by conjugation between T or B cell epitopes with universal or immunodominant T-helper epitopes. The construction of branched peptides, lipidated peptides, or designs combining both of these elements might also enhance the immunogenicity, as they might target Toll-like receptors and/or mimic the 3-dimensional structure of epitopes within the native protein. In this study, a recognized T-B peptide based on the hemagglutinin protein of the A/Puerto Rico/8/34 influenza virus was chosen as a backbone and modified to evaluate if the construction of branched peptides, lipidation, the addition of cysteine residues, or mutations could indeed alter reactivity. Screening the different designs with various antibody binding and cellular assays revealed that combining a branched design with the addition of lipid moieties leads to a greatly enhanced activity as compared to other similar T-B diepitope constructs.

This study assessed the principles of ecosystem management and utilized the Northern Map turtle, a species at risk, as a key indicator species to illustrate the importance of preserving riparian habitats and island complexes on an ecosystem scale. Overall, the study explored the population characteristics and use of habitat of the Northern Map turtle (Graptemys geographica) within a small bay within the Gananoque River system in South Eastern Ontario. Results from field observations showed that the bay population of Northern Map turtles appeared to be female biased. Use of habitat features differed by females, males and juveniles at different times throughout the summer (May-August). Females were frequently observed basking within the bay in May and June while males were more frequently observed throughout July and August. Nesting by female Northern Map turtles appeared to be concentrated atop small islands scattered throughout the bay. Nest sites were located within narrow bands of soils. The most prominent difference between site conditions at the monitored nests was soil moisture; this was likely the result of different soil materials at each site. Air and soil temperature did not differ significantly between sites. Additional research could be pursued on the bay population of Northern Map turtles looking at the following: movement patterns by females out of the bay post-nesting, genetic linkages to other satellite populations of Northern Map turtles in the Thousand Islands, hatchling success and sex composition, overall species health due to food availability and lastly the effects of anthropogenic stressors.

This study assessed the principles of ecosystem management and utilized the Northern Map turtle, a species at risk, as a key indicator species to illustrate the importance of preserving riparian habitats and island complexes on an ecosystem scale. Overall, the study explored the population characteristics and use of habitat of the Northern Map turtle (Graptemys geographica) within a small bay within the Gananoque River system in South Eastern Ontario. Results from field observations showed that the bay population of Northern Map turtles appeared to be female biased. Use of habitat features differed by females, males and juveniles at different times throughout the summer (May-August). Females were frequently observed basking within the bay in May and June while males were more frequently observed throughout July and August. Nesting by female Northern Map turtles appeared to be concentrated atop small islands scattered throughout the bay. Nest sites were located within narrow bands of soils. The most prominent difference between site conditions at the monitored nests was soil moisture; this was likely the result of different soil materials at each site. Air and soil temperature did not differ significantly between sites. Additional research could be pursued on the bay population of Northern Map turtles looking at the following: movement patterns by females out of the bay post-nesting, genetic linkages to other satellite populations of Northern Map turtles in the Thousand Islands, hatchling success and sex composition, overall species health due to food availability and lastly the effects of anthropogenic stressors.