Increasing involvement with students at the University of Namibia has indicated their overall difficulty with comprehending and recalling information from oral content lectures. It has also been observed that in general very little attention is given to the development of listening skills in L2 ESP and EAP courses. For this study, I conducted a quasi-experiment to determine whether the recognition and interpretation of discourse markers will enhance students' listening comprehension in academic lectures. Students were tested to determine their comprehension of content information in a video-taped lecture. Qualitative data were collected by means of a questionnaire. After an intervention period of eight weeks, where the experimental group received strategy training in the recognition and interpretation of discourse markers in spoken texts, both groups were again tested. Their results were statistically compared. I also looked at related findings of other researchers. Finally, aspects for possible future research will also be considered. / English Studies / MA - (Specialisation in TESOL)

This research investigates soil respiration (Rs) in a boreal jack pine (Pinus banksiana Lamb.) fire scar chronosequence at Sharpsand Creek, Ontario, Canada. During two field campaigns in 2006 and 2007, Rs was measured in a chronosequence of fire scars in the range 0 to 59 years since fire. Mean Rs adjusted for soil temperature (Ts) and soil moisture (Ms) (Rs T,M) ranged from 0.56 μmol CO2/m2/s (32 years post fire) to 8.18 μmol CO2/m2/s (58 years post fire). Coefficient of variation (CV) of Rs adjusted for Ts and Ms ranged from 20% (16 years post fire) to 56% (58 years post fire). Across the field site, there was a significant exponential relationship between Rs adjusted for soil organic carbon (Cs) and Ts (P = 1.24*10-06; Q10 = 2.21) but no effect of Ms on Rs adjusted for Cs and Ts for the range 0.21 to 0.77 volumetric Ms (P = 0.702). Rs T,M significantly (P = 0.030) decreased after burning mature forest, though no significant (P > 0.1) difference could be detected between recently burned and unburned young forest. Rs was measured in recently burned boreal jack pine fire scar age categories that differed in their burn history and there was a significant difference in Rs T,M between previously 32 v 16 year old (P = 0.000) and previously 32 v 59 year old (P = 0.044) scars. There was a strong significant exponential increase in S R T,M with time since fire (r2 = 0.999; P = 0.006) for the chronosequence 0, 16 and 59 years post fire, and for all these age categories, Rs T,M was significantly different from one another (P < 0.05). The Joint UK Land Environment Simulator (JULES) was used to model vegetation re-growth over successional time at Sharpsand Creek, though it appeared to perform poorly in simulating leaf area index and canopy height. JULES probably over estimated heterotrophic Rs at Sharpsand Creek when Ts corrected simulated values were compared with measured Rs T,M. The results of this study contribute to a better quantitative understanding of Rs in boreal jack pine fire scars and will facilitate improvements in C cycle modelling. Further work is needed in quantifying autotrophic and heterotrophic contributions to soil respiration in jack pine systems, monitoring soil respiration for extended time periods after fire and improving the ability of JULES to simulate successional vegetation re-growth.

In dieser Dissertation wird ein Modell des visuellen Systems untersucht, basierend auf dem Prinzip des unüberwachten Langsamkeitslernens und des SFA-Algorithmus (Slow Feature Analysis). Dieses Modell wird hier für die invariante Objekterkennung und verwandte Probleme eingesetzt. Das Modell kann dabei sowohl die zu Grunde liegenden diskreten Variablen der Stimuli extrahieren (z.B. die Identität des gezeigten Objektes) als auch kontinuierliche Variablen (z.B. Position und Rotationswinkel). Dabei ist es in der Lage, mit komplizierten Transformationen umzugehen, wie beispielsweise Tiefenrotation. Die Leistungsfähigkeit des Modells wird zunächst mit Hilfe von überwachten Methoden zur Datenanalyse untersucht. Anschließend wird gezeigt, dass auch die biologisch fundierte Methode des Verstärkenden Lernens (reinforcement learning) die Ausgabedaten unseres Modells erfolgreich verwenden kann. Dies erlaubt die Anwendung des Verstärkenden Lernens auf hochdimensionale visuelle Stimuli. Im zweiten Teil der Arbeit wird versucht, das hierarchische Modell mit Top-down Prozessen zu erweitern, speziell für die Rekonstruktion von visuellen Stimuli. Dabei setzen wir die Methode der Vektorquantisierung ein und verbinden diese mit einem Verfahren zum Gradientenabstieg. Die wesentlichen Komponenten der für unsere Simulationen entwickelten Software wurden in eine quelloffene Programmbibliothek integriert, in das ``Modular toolkit for Data Processing'''' (MDP). Diese Programmkomponenten werden im letzten Teil der Dissertation vorgestellt. / This thesis examines a model of the visual system, which is based on the principle of unsupervised slowness learning and using Slow Feature Analysis (SFA). We apply this model to the task of invariant object recognition and several related problems. The model not only learns to extract the underlying discrete variables of the stimuli (e.g., identity of the shown object) but also to extract continuous variables (e.g., position and rotational angles). It is shown to be capable of dealing with complex transformations like in-depth rotation. The performance of the model is first measured with the help of supervised post-processing methods. We then show that biologically motivated methods like reinforcement learning are also capable of processing the high-level output from the model. This enables reinforcement learning to deal with high-dimensional visual stimuli. In the second part of this thesis we try to extend the model with top-down processes, centered around the task of reconstructing visual stimuli. We utilize the method of vector quantization and combine it with gradient descent. The key components of our simulation software have been integrated into an open-source software library, the Modular toolkit for Data Processing (MDP). These components are presented in the last part of the thesis.

Florações de microalgas potencialmente nocivas têm aumentado em termos globais e causado impactos na aquicultura, no turismo, na saúde humana e em vários aspectos do funcionamento dos ecossistemas. No Brasil, uma atenção cada vez maior tem sido dada ao tema, em virtude do elevado potencial de nossas águas para o cultivo de bivalves marinhos, um dos grupos de invertebrados mais afetados. Deste modo, a preocupação com a contaminação de consumidores humanos tem gerado projetos voltados para a detecção de espécies potencialmente nocivas e de suas toxinas, mas ainda há poucos estudos sobre interações alimentares entre as espécies de fitoplâncton e zooplâncton. No presente trabalho interações entre dinoflagelados potencialmente nocivos e organismos pertencentes ao zooplâncton marinho foram investigadas em dois capítulos. Capítulo 1: O presente estudo tem como objetivo avaliar a influência do dinoflagelado potencialmente nocivo Alexandrium tamiyavanichii na alimentação e reprodução do copépode planctônico marinho Temora turbinata. Taxas de produção de ovos e sucesso de eclosão naupliar foram estimadas para fêmeas alimentadas em misturas de A. tamiyavanichii e do dinoflagelado Prorocentrum minimum, tratado aqui como alimento controle. Capítulo 2: O principal objetivo deste estudo foi analisar os efeitos de exsudatos de dinoflagelados e células intactas na sobrevivência e mobilidade de táxons zooplanctônicos de uma região subtropical (Ubatuba, Brasil). Efeitos letais foram observados em cinco dos seis táxons testados, três dos quais (náuplios de copépodes, tintinídeos e larvas de gastrópodes) quando expostos a exsudatos e dois (rotíferos e larvas de braquiúros) quando expostos a células intactas. Em adição, larvas de gastrópodes demonstraram comprometimento da mobilidade após exposição à exsudatos. Apenas larvas de poliquetas não foram aparentemente afetadas no curso dos experimentos. / Harmful algae blooms have increased globally and caused impacts in aquaculture, tourism, and human health and in various aspects of ecosystem functioning. In Brazil, increasing attention has been given to this issue, because of the high potential of our waters for marine bivalve farming. Therefore, there are risks of contamination of the crops, and consequent poisoning of the consumers. This concern has led research projects to mostly focus on the detection of potentially harmful species and their toxins, with few initiatives to understand feeding interactions among species of phytoplankton and zooplankton. In this research interactions between potentially harmful dinoflagellates and marine zooplankton were investigated in two chapters. Chapter 1 - This study aims to evaluate the influence of the potentially harmful dinoflagellate Alexandrium tamiyavanichii on Temora turbinata feeding and reproduction. Egg production rates and hatching success were estimated for females fed on mixtures of A. tamiyavanichii and P. minimum. Chapter 2: The aim of this study was to analyze the effects of dinoflagellate exudates and intact cells on the survivorship and mobility of zooplankton taxa from a subtropical location (Ubatuba, Brazil). Lethal effects were observed in five out of six taxa investigated, three of which (copepod nauplii, tintinnids and gastropod larvae) when exposed to dinoflagellate exudates and two (rotifers and brachyuran zoeae) when exposed to intact cells. In addition, gastropod larvae displayed mobility impairment during exposure to dinoflagellate exudates. Only polychaete larvae were not apparently affected during the course of the experiments.

Florações de microalgas potencialmente nocivas têm aumentado em termos globais e causado impactos na aquicultura, no turismo, na saúde humana e em vários aspectos do funcionamento dos ecossistemas. No Brasil, uma atenção cada vez maior tem sido dada ao tema, em virtude do elevado potencial de nossas águas para o cultivo de bivalves marinhos, um dos grupos de invertebrados mais afetados. Deste modo, a preocupação com a contaminação de consumidores humanos tem gerado projetos voltados para a detecção de espécies potencialmente nocivas e de suas toxinas, mas ainda há poucos estudos sobre interações alimentares entre as espécies de fitoplâncton e zooplâncton. No presente trabalho interações entre dinoflagelados potencialmente nocivos e organismos pertencentes ao zooplâncton marinho foram investigadas em dois capítulos. Capítulo 1: O presente estudo tem como objetivo avaliar a influência do dinoflagelado potencialmente nocivo Alexandrium tamiyavanichii na alimentação e reprodução do copépode planctônico marinho Temora turbinata. Taxas de produção de ovos e sucesso de eclosão naupliar foram estimadas para fêmeas alimentadas em misturas de A. tamiyavanichii e do dinoflagelado Prorocentrum minimum, tratado aqui como alimento controle. Capítulo 2: O principal objetivo deste estudo foi analisar os efeitos de exsudatos de dinoflagelados e células intactas na sobrevivência e mobilidade de táxons zooplanctônicos de uma região subtropical (Ubatuba, Brasil). Efeitos letais foram observados em cinco dos seis táxons testados, três dos quais (náuplios de copépodes, tintinídeos e larvas de gastrópodes) quando expostos a exsudatos e dois (rotíferos e larvas de braquiúros) quando expostos a células intactas. Em adição, larvas de gastrópodes demonstraram comprometimento da mobilidade após exposição à exsudatos. Apenas larvas de poliquetas não foram aparentemente afetadas no curso dos experimentos. / Harmful algae blooms have increased globally and caused impacts in aquaculture, tourism, and human health and in various aspects of ecosystem functioning. In Brazil, increasing attention has been given to this issue, because of the high potential of our waters for marine bivalve farming. Therefore, there are risks of contamination of the crops, and consequent poisoning of the consumers. This concern has led research projects to mostly focus on the detection of potentially harmful species and their toxins, with few initiatives to understand feeding interactions among species of phytoplankton and zooplankton. In this research interactions between potentially harmful dinoflagellates and marine zooplankton were investigated in two chapters. Chapter 1 - This study aims to evaluate the influence of the potentially harmful dinoflagellate Alexandrium tamiyavanichii on Temora turbinata feeding and reproduction. Egg production rates and hatching success were estimated for females fed on mixtures of A. tamiyavanichii and P. minimum. Chapter 2: The aim of this study was to analyze the effects of dinoflagellate exudates and intact cells on the survivorship and mobility of zooplankton taxa from a subtropical location (Ubatuba, Brazil). Lethal effects were observed in five out of six taxa investigated, three of which (copepod nauplii, tintinnids and gastropod larvae) when exposed to dinoflagellate exudates and two (rotifers and brachyuran zoeae) when exposed to intact cells. In addition, gastropod larvae displayed mobility impairment during exposure to dinoflagellate exudates. Only polychaete larvae were not apparently affected during the course of the experiments.

L'apparition récente de nouveaux matériaux dans les structures de chaussée associée à une diminution de l'épaisseur des couches de surface et une augmentation du chargement des poids lourds et de leur fréquence de passage a entrainé de nouvelles pathologies de dégradation. Outre les problèmes d'orniérage bien connus, apparaissent désormais des fissures descendantes (top down cracking) ainsi que des problèmes de décohésion aux interfaces. Ces nouvelles pathologies entrainent des dépenses considérables sur l'ensemble du réseau (environ 15 milliards d'euros par an), particulièrement en zones urbanisées plus sujettes aux dégradations de surface et ne permettent pas d'estimer convenablement les durées de vie de la chaussée, le plus souvent surestimée dans les méthodes de dimensionnement actuelles. Ce travail de doctorat propose une nouvelle approche du contact pneu-chaussée permettant de mieux appréhender les contraintes principales et résiduelles dans une structure de chaussée bitumineuse. A l'aide d'un outil numérique rapide de calcul basé sur une approche semi-analytique (« Semi-Analytical Methods » (SAM)), la géométrie précise du pneumatique est intégrée afin d'obtenir une répartition de pression de contact ainsi qu'un cisaillement surfacique réelle sur la chaussée. Dans un premier temps, un modèle de contact roulant tractif élastique est implémenté pour des cas théoriques simples et validé par des résultats analytiques et numériques de la littérature. Ensuite, ce modèle est étendu pour prendre en compte le comportement élasto-plastique des corps en contact. Ce dernier est comparé à un résultat numérique basé sur la méthode des éléments finis issu de la littérature. Les résultats, pour une application contact pneu-chaussée, montrent une répartition non homogène des contraintes dans la structure et principalement dans les premiers centimètres sous la surface avec des niveaux beaucoup plus importants que peuvent le prédire les modèles actuels qui utilisent une charge uniformément répartie. La pression de contact est comparée aux mesures effectuées par un système nommé TekScan et les champs mécaniques en sous couches sont comparés à ceux d'Alizé-LCPC dans le cas d'une structure simple. Les cisaillements surfaciques sont déterminés dans le cas du roulement tractif. Une application est effectuée sur la modélisation des dégradations des chaussées en surface. Dans un premier temps, des analyses sur le comportement de la chaussée en surface sont effectuées pour une couche de béton bitumineux semi grenu (BBSG) semi-infinie supposée élastique, homogène sous conditions d'accélération, de freinage et de virage. Pour des études sur le top down cracking, des déformations et directions principales sont déterminées et analysées. Ensuite, le modèle de contact élasto-plastique est appliqué sur une couche semi-infinie de grave bitume GB3. Des déformations et contraintes résiduelles générées dans la structure sont déterminées en vue d'une analyse sur les ornières d'instabilité. Une fois validés, ces résultats permettront d'estimer plus fidèlement la durée de vie résiduelle des chaussées mais également de comprendre et d'éviter les mécanismes de dégradation en surface ou proche de la surface. / The recent appearance of new materials in road structures associated with surface layers thickness decreasing and the increasing of trucks loading and their passage frequency has led to new pathologies of degradation. In addition to the well-known rutting problems, top down cracking is now appearing as well as problems of decohesion at the interfaces. These new pathologies led to considerable expenditure on the entire network (around 15 billion euros per year), particularly in urbanized areas that are more prone to surface damage and do not make it possible to adequately estimate the lifetimes of the roadway, most often overestimated in current design methods. This doctoral work proposes a new approach of the tire-road contact allowing for better apprehend of the main and residual stresses in a bituminous pavement structure. Using a fast numerical tool based on a semi-analytical approach ("Semi-Analytical Methods" (SAM)), the precise geometry of the tire is integrated in order to obtain a real contact pressure distribution as well as surface shear on the pavement surface. Initially, an elastic tractive rolling contact model is implemented for simple theoretical cases and validated by analytical and numerical results from the literature.Then, this model is extended to take into account the elastoplastic behavior of the bodies in contact. This is compared to a numerical result based on the nite element method from the literature. The application for tire-pavement contact results, show a non-uniform distribution of stresses in the structure and mainly in the rst centimeters below the surface with much higher levels than can be predicted by current models that use a uniformly distributed load. The contact pressure is compared to the measurements made by a system called TekScan and the mechanical elds in sublayers are compared to those of Alizé-LCPC in the case of a simple structure. The surface shears are determined in the case of tractive rolling. An application is carried out on the modeling of surface pavement damage. Firstly, analyzes of the behavior of the surface pavement are carried out for a semi-innite semi-grit asphalt concrete layer supposed to be elastic, homogeneous under conditions of acceleration, braking and turning. For studies on top down cracking, principals deformations and directions are determined and analyzed. Then, the elastoplastic contact model is applied on a semi-innite asphalt agragate layer. Deformations and residuals stresses generated in the structure are determined for an analysis on the instability ruts. Once validated, these results will make it possible to more accurately estimate the residual life of pavements but also to understand and avoid surface or near surfacedegradation mechanisms.

In this thesis I study several deductive systems for linear logic, its fragments, and some noncommutative extensions. All systems will be designed within the calculus of structures, which is a proof theoretical formalism for specifying logical systems, in the tradition of Hilbert's formalism, natural deduction, and the sequent calculus. Systems in the calculus of structures are based on two simple principles: deep inference and top-down symmetry. Together they have remarkable consequences for the properties of the logical systems. For example, for linear logic it is possible to design a deductive system, in which all rules are local. In particular, the contraction rule is reduced to an atomic version, and there is no global promotion rule. I will also show an extension of multiplicative exponential linear logic by a noncommutative, self-dual connective which is not representable in the sequent calculus. All systems enjoy the cut elimination property. Moreover, this can be proved independently from the sequent calculus via techniques that are based on the new top-down symmetry. Furthermore, for all systems, I will present several decomposition theorems which constitute a new type of normal form for derivations.

Ce travail de thèse porte sur l'organisation de nanoparticules sur des surfaces grâce à une approche originale basée sur le dépôt à faible énergie d'agrégats, préformés en phase gazeuse (approche Bottom-up), sur substrats de graphite HOPG, fonctionnalisés par des réseaux 2D de défauts créés par faisceau d'ions focalisés nano-FIB (approche Top-down). L'obtention de réseaux 2D d'amas d'agrégats est conditionnée par la diffusion des agrégats déposés et leur sensibilité aux défauts artificiels FIB. Le développement de cette approche passe tout d'abord par des simulations Monte-Carlo réalisées dans le cadre du modèle DDA (Dépôt-Diffusion-Agrégation). Ensuite, sa faisabilité expérimentale est testée avec succès en déposant des agrégats d'or. En particulier, cette étude montre la dépendance des propriétés morphologiques et structurales des défauts FIB en fonction de la dose d'ions. Par ailleurs, la sensibilité des agrégats aux défauts FIB, ainsi que la possibilité de contrôler la taille des amas, la période du réseau et sa géométrie sont analysées. Enfin, en se plaçant dans les conditions optimales permettant la meilleure organisation, notre approche est étendue aux agrégats magnétiques Co50Pt50, candidats potentiels au stockage d'information à ultra-haute densité. Une étude de l'influence du recuit sur les réseaux d'agrégats Co50Pt50 montre une amélioration de la qualité de l'organisation, et surtout une transition de phase des agrégats de la structure<br />A1 vers la structure L10.

III-V nanostructures have attracted substantial research effort due to their interesting physical properties and their applications in new generation of ultrafast and high efficiency nanoscale electronic and photonic components. The advances in nanofabrication methods including growth/synthesis have opened up new possibilities of realizing one dimensional (1D) nanostructures as building blocks of future nanoscale devices. For processing of semiconductor nanostructure devices, simplicity, cost effectiveness, and device efficiency are key factors. A number of methods are being pursued to fabricate high quality III-V nanopillar/nanowires, quantum dots and nano disks. Further, high optical quality nanostructures in these materials together with precise control of shapes, sizes and array geometries make them attractive for a wide range of optoelectronic/photonic devices. This thesis work is focused on top-down approaches for fabrication of high optical quality nanostructures in III-V materials. Dense and uniform arrays of nanopillars are fabricated by dry etching using self-assembly of colloidal SiO2 particles for masking. The physico-chemistry of etching and the effect of etch-mask parameters are investigated to control the shape, aspect ratios and spatial coverage of the nanopillar arrays. The optimization of etch parameters and the utilization of erosion of etch masks is evaluated to obtain desired pillar shapes from cylindrical to conical. Using this fabrication method, high quality nanopillar arrays were realized in several InP-based and GaAs-based structures, including quantum wells and multilayer heterostructures. Optical properties of these pillars are investigated using different optical spectroscopic techniques. These nanopillars, single and in arrays, show excellent photoluminescence (PL) at room temperature and the measured PL line-widths are comparable to the as-grown wafer, indicating the high quality of the fabricated nanostructures. The substrate-free InP nanopillars have carrier life times similar to reference epitaxial layers, yet an another indicator of high material quality. InGaAs layer, beneath the pillars is shown to provide several useful functions. It effectively blocks the PL from the InP substrate, serves as a sacrificial layer for generation of free pillars, and as a “detector” in cathodoluminescence (CL) measurements. Diffusion lengths independently determined by time resolved photoluminescence (TRPL) and CL measurements are consistent, and carrier feeding to low bandgap InGaAs layer is evidenced by CL data. Total reflectivity measurements show that nanopillar arrays provide broadband antireflection making them good candidates for photovoltaic applications.  A novel post etch, sulfur-oleylamine (S-OA) based chemical process is developed to etch III-V materials with monolayer precision, in an inverse epitaxial manner along with simultaneous surface passivation. The process is applied to push the limits of top-down fabrication and InP-based high optical quality nanowires with aspect ratios more than 50, and nanostructures with new topologies (nanowire meshes and in-plane wires) are demonstrated.  The optimized process technique is used to fabricate nanopillars in InP-based multilayers (InP/InGaAsP/InP and InP/InGaAs/InP). Such multilayer nanopillars are not only attractive for broad-band absorption in solar cells, but are also ideal to generate high optical quality nanodisks of these materials. Finally, the utility of a soft stamping technique to transfer free nanopillars/wires and nanodisks onto Si substrate is demonstrated. These nanostructures transferred onto Si with controlled densities, from low to high, could provide a new route for material integration on Si. / <p>QC 20130205</p>

Elasmobranchs are among the oldest and most successful predators in the ocean, yet one of the most vulnerable to the direct and indirect effects of fishing. Many populations are rapidly declining around the world, and an increasing number is listed as threatened or endangered. The broader ecosystem consequences of these declines, and whether other marine predators can replace sharks, are open questions. In this thesis, I used a diverse set of data and modeling techniques to analyze long-term changes in elasmobranch populations in the Mediterranean Sea, and the consequences of shark declines on marine ecosystems. Because of its long history of fishing, the Mediterranean offers a unique perspective on the response of marine communities to exploitation over long time scales. Here, I reconstructed the history of elasmobranch exploitation over the past 200 years in pelagic, coastal and demersal communities. Results were combined meta-analytically to derive a general pattern of change for the entire region. Overall, I detected multiple cases of regional species extirpations, a strong correlation between historical intensity of exploitation and the stage of community degradation, and some cases of compensatory species increases. My results suggest that compared to other marine ecosystems worldwide, the Mediterranean Sea might be in an advanced stage of overexploitation. To gain more general conclusions about the patterns and consequences of shark declines in the ocean, I reviewed and reanalyzed documented changes in exploited elasmobranch communities around the world, and synthesized the effects of sharks on their prey and wider communities. This work revealed that sharks are abundant and diverse in little exploited or unexploited marine ecosystems but vulnerable to even light levels of fishing. The decline in large sharks has reduced natural mortality in a range of their prey, contributing to changes in abundance, distribution, and behaviour of marine megafauna that have few other predators. In some cases, this has resulted in cascading changes in prey populations and food-web structure. Overall, my thesis greatly enhanced our knowledge about the critical state of elasmobranchs in the Mediterranean Sea and the consequences of the declines of these important marine predators on marine ecosystems.