Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

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Face au contexte particulier du territoire réunionnais, avec un climat tropical cyclonique, une surface habitable réduite de plus en plus en proie à un étalement urbain grandissant, un foncier rare et cher, des matériaux pour la plupart importés, une main d'œuvre peu qualifiée, une dépendance énergétique extérieure, une demande croissante de logements, des revenus plus bas que la moyenne nationale ainsi qu'une population qui ne cesse d'augmenter, le défi architectural à relever est de proposer de nouvelles formes d'habitat économique et écologique qui soient différentes de la kaz créole traditionnelle consommatrice d'espace tout en étant respectueuses des us et coutumes réunionnaises. / Facing the context of the territory of Reunion island, with its tropical and cyclonic climate, a restricted inhabiting surface that is more and more exposed to a growing urban spreading out, a rare and costly land property, building material which are mainly imported, a low-qualified man power, an outer energetic dependence, a growing demand for housing, wages that are lower than the national average and a population which never get up increasing, the architectural challenge consists in proposing new shapes of low-cost and ecological habitat that could be different from the traditional Creole cabin very consuming of space while being respectful of the ways and customs of inhabitants of Reunion.

Transcranial direct current stimulation (TDCS) allows for the noninvasive modulation of cortical activity. In this study, the effects of cathodal and anodal TDCS treatment on baseline activity in the motor cortex of rats were investigated via translaminar electroencephalogram (EEG) recording and power spectral density analysis. Treatment with low intensity anodal TDCS for five minutes was found to increase delta and theta frequency cortical activity during and for up to five minutes following treatment. This study also assessed the interaction of TDCS with the phenomenon of cortical spreading depression (CoSD), which has been implicated in numerous disease states, including migraine and stroke. TDCS treatment was given concurrently with induction of CoSD via administration of potassium chloride to the surface of the dura. The presence of the spreading depression event, a characteristic low frequency wave observed to travel outwards from the point of CoSD induction and downwards through the cortex, was used as a proxy measure for the occurrence of CoSD. It was observed that animals treated with cathodal TDCS exhibited fewer spreading depression events relative to those treated with anodal TDCS or those receiving sham treatment. In this study, animals were segregated into groups that exhibited stimulus artifact during TDCS treatment and those that did not. Stimulus artifact was defined as a characteristic alpha and/or beta frequency activity spike lasting throughout and not longer than the period of stimulation. Those animals receiving TDCS without exhibiting stimulus artifact were considered for the purposes of this study to not have received proper TDCS treatment, and acted as a sham treatment group. Because salient differences emerged between the stimulus artifact positive and stimulus artifact negative groups, this study suggests that the presence of stimulus artifact could be used as a proxy measure for successful TDCS dosage.

Surface gravity waves exist in the oceans as multi-directional nonlinear phenomena. Understanding how these two properties interact is intrinsically important in itself. Furthermore, an understanding of this relationship may be used to gain insight into other oceanic phenomena. This thesis first describes an experimental investigation into the relationship between directionality and non-linearity (Part I). This relationship was then used as a tool to estimate the directional spreading of field data (Part II). Experiments have been conducted in which directionally spread focused wave groups were created in a wave tank. The relationship between the degree of directional spreading and the second-order bound harmonics of the wave groups was examined, in particular the formation of a `set-up'. These measurements were then compared to predictions from second-order theories, finding good agreement. The two-dimensional structure of the bound waves was explored giving new insight into the underlying physics. Experiments were then carried out for directionally spread crossing wave groups. It is believed that the crossing of two sufficiently separated wave groups may be the cause of an anomalous set-up in the second-order bound waves observed for some extreme and potentially freak waves. This set-up is reproduced experimentally. Again, the results of these test agreed very well when compared to second-order theory. The insight gained from the foregoing experiments was then utilised in the analysis of field data. A method, which requires only a single measurement to estimate the observed degree of directional spreading, was applied to a large dataset of field measurements from the North Alwyn platform in the North Sea. This method was then compared to conventional approaches, which require multiple concurrent measurements. The method that requires only a single measurement was shown to be effective, and presents a promising approach to gaining additional insight about the directional spreading of point observations.

Current problems on the interaction of complex liquids (i.e. droplets or foams) with complex surfaces (i.e. soft deformable or porous surfaces) are addressed in the following areas: (1) wetting of deformable substrates and surface forces, (2) kinetics of wetting and spreading of non-Newtonian liquids over porous substrates, (3) kinetics of spreading of non-Newtonian solutions over hair, (4) free drainage of foams produced from non-Newtonian solutions, and (5) foam drainage placed on porous substrates. Equilibrium of liquid droplets on deformable substrates was investigated and the effect of disjoining pressure action in the vicinity of the apparent three phase contact line was taken into account. It was proven that the deformation of soft solids is determined by the action of surface forces inside the transition zone. Spreading/imbibition of blood, which is a power law shear thinning non-Newtonian liquid, over a dry porous layer was investigated from both theoretical and experimental points of view. It was found that blood droplet spreading/imbibition over porous substrates shows two different behaviours: (i) partial wetting case with three subsequent stages: initial fast spreading, constant maximum droplet base and the shrinkage of the droplet base; (ii) complete wetting case with only two stages: initial fast spreading and the shrinkage of the droplet base. The wetting of hair tresses by aqueous solutions of two commercially available polymers, AculynTM 22 (A22) and AculynTM 33 (A33) was investigated experimentally. Both A22 and A33 solutions demonstrate well pronounced shear thinning behaviour. Initial contact angle of the A22 and A33 solutions on hair tresses was about 100o. The A22 droplets remained on the hair tress after spreading for at least half an hour. However, a fast penetration of the A33 droplets inside the hair tresses was observed when advancing contact angle in the course of spreading reached a critical value of about 60o. This could be explained by Cassie-Wenzel wetting transition which is caused by filling the pores inside the porous media by liquid. The influence of non-Newtonian rheology of A22 and A33 solutions on foam drainage was also investigated experimentally and a new theory of foam drainage was presented for the case of free drainage. For lowly viscous polymeric solutions and under the assumption of rigid surface of the Plateau border, the predicted values of the time evolution of the foam height and liquid content were in good agreement with the experimental data. However, in the case of highly viscous solutions an interfacial mobility at the surface of the Plateau border has to be taken into account. A completely new theory of foam drainage placed on porous substrate was developed. It was found that there are three different regimes of the process: (i) a rapid imbibition, the imbibition into the porous substrate dominates as compared with the foam drainage; (ii) an intermediate imbibition, that is, the imbibition into the porous substrate and the rate of drainage are comparable; (iii) a slow imbibition, the rate of drainage inside the foam is higher than the imbibition into the porous substrate for a period of time and a free liquid layer is formed over the porous substrate.

La recherche d’information sémantique (RIS), cherche à proposer des modèles qui permettent de s’appuyer, au delà des calculs statistiques, sur la signification et la sémantique des mots du vocabulaire, afin de mieux caractériser les documents pertinents au regard du besoin de l’utilisateur et de les retrouver. Le but est ainsi de dépasser les approches classiques purement statistiques (de « sac de mots »), fondées sur des appariements de chaînes de caractères sur la base des fréquences des mots et de l’analyse de leurs distributions dans le texte. Pour ce faire, les approches existantes de RIS, à travers l’exploitation de ressources sémantiques externes (thésaurus ou ontologies), procèdent en injectant des connaissances dans les modèles classiques de RI de manière à désambiguïser le vocabulaire ou à enrichir la représentation des documents et des requêtes. Il s’agit le plus souvent d’adaptations de ces modèles, on passe alors à une approche « sac de concepts » qui permet de prendre en compte la sémantique notamment la synonymie. Les ressources sémantiques, ainsi exploitées, sont « aplaties », les calculs se cantonnent, généralement, à des calculs de similarité sémantique. Afin de permettre une meilleure exploitation de la sémantique en RI, nous mettons en place un nouveau modèle, qui permet d’unifier de manière cohérente et homogène les informations numériques (distributionnelles) et symboliques (sémantiques) sans sacrifier la puissance des analyses. Le réseau sémantico-documentaire ainsi modélisé est traduit en graphe pondéré. Le mécanisme d’appariement est assuré par une propagation d’activation dans le graphe. Ce nouveau modèle permet à la fois de répondre à des requêtes exprimées sous forme de mots clés, de concepts oumême de documents exemples. L’algorithme de propagation a le mérite de préserver les caractéristiques largement éprouvéesdes modèles classiques de recherche d’information tout en permettant une meilleure prise en compte des modèles sémantiques et de leurs richesse. Selon que l’on introduit ou pas de la sémantique dans ce graphe, ce modèle permet de reproduire une RI classique ou d’assurer en sus certaines fonctionnalités sémantiques. La co-occurrence dans le graphe permet alors de révélerune sémantique implicite qui améliore la précision en résolvant certaines ambiguïtés sémantiques.L’exploitation explicite des concepts ainsi que des liens du graphe, permettent la résolution des problèmes de synonymie, de term mismatch et de couverture sémantique. Ces fonctionnalités sémantiques, ainsi que le passage à l’échelle du modèle présenté, sont validés expérimentalement sur un corpus dans le domaine médical. / Semantic information retrieval (SIR) aims to propose models that allow us to rely, beyond statistical calculations, on the meaning and semantics of the words of the vocabulary, in order to better represent relevant documents with respect to user’s needs, and better retrieve them.The aim is therefore to overcome the classical purely statistical (« bag of wordsé») approaches, based on strings’ matching and the analysis of the frequencies of the words and their distributions in the text.To do this, existing SIR approaches, through the exploitation of external semantic resources (thesauri, ontologies, etc.), proceed by injecting knowledge into the classical IR models (such as the vector space model) in order to disambiguate the vocabulary or to enrich the representation of documents and queries.These are usually adaptations of the classical IR models. We go so to a « bag of concepts » approach which allows us to take account of synonymy. The semantic resources thus exploited are « flattened », the calculations are generally confined to calculations of semantic similarities.In order to better exploit the semantics in RI, we propose a new model, which allows to unify in a coherent and homogeneous way the numerical (distributional) and symbolic (semantic) information without sacrificing the power of the analyzes of the one for the other. The semantic-documentary network thus modeled is translated into a weighted graph. The matching mechanism is provided by a Spreading activation mechanism in the graph. This new model allows to respond to queries expressed in the form of key words, concepts or even examples of documents. The propagation algorithm has the merit of preserving the well-tested characteristics of classical information retrieval models while allowing a better consideration of semantic models and their richness.Depending on whether semantics is introduced in the graph or not, this model makes it possible to reproduce a classical IR or provides, in addition, some semantic functionalities. The co-occurrence in the graph then makes it possible to reveal an implicit semantics which improves the precision by solving some semantic ambiguities. The explicit exploitation of the concepts as well as the links of the graph allow the resolution of the problems of synonymy, term mismatch, semantic coverage, etc. These semantic features, as well as the scaling up of the model presented, are validated experimentally on a corpus in the medical field.

One of the primary tasks of the mobile system designers in order to support high density of devices in a CDMA system is to create a code sequence with a capacity for large number of spreading code sequences having low cross-correlation values between them, in order to ensure accommodation of large number of users and to minimise the effect of multiple access interference. In this research, the design for a novel hybrid orthogonal very large set (HOVLS) code sequence is proposed for high density mobile application scenarios. The design and development of both fixed and variable spreading factor code sequences are presented in this thesis. Both type of code sequences have been implemented via simulation using Matlab/Simulink. The performance of the code sequences has been evaluated and compared with that of existing code sequences. The proposed code sequences are more advantageous for high density mobile networks. The unique feature of the fixed length HOVLS code sequence is that its ACF, CCF, and BER performances are similar to that of orthogonal Gold code sequence and orthogonal m-sequence under Rayleigh flat and frequency selective fading channel conditions while having a significantly higher capacity than those orthogonal code sequences. The proposed HOVLS code sequence could support 134 different cells which is more than twice than that of orthogonal Gold code sequence and orthogonal m-sequence. To the knowledge of the author, this is the largest reported family size in the literature for an orthogonal code sequence for CDMA applications. In order to support variable data rate, fixed length HOVLS code sequence was developed into orthogonal variable spreading factor code sequence. It is shown that the proposed OVSF code sequence has slightly better CCF than those of OVSF Gold code sequence and m-sequence in terms of CM (correlation margin). The ACF of the proposed OVSF code sequence is similar to those of OVSF Gold code sequence and m-sequence. The proposed OVSF code sequence possesses comparable BER performance to those of orthogonal Gold code sequence and orthogonal m-sequence under flat fading channel condition. Whereas, the BER performance of the proposed OVSF code sequence is slightly better than that of Gold code sequence and OVSF m-sequence under frequency selective fading channel. Therefore, the proposed HOVLS code sequence is appropriate code sequence in CDMA systems than those of orthogonal Gold code sequence and orthogonal m-sequence for both fixed and variable rate high density network applications.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-04-27T14:10:38Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Dout_Lima_DSCL_2016.pdf: 2341451 bytes, checksum: e4310955dbc4f0c3af7730606a09c7f3 (MD5) / Made available in DSpace on 2017-04-27T14:10:39Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Dout_Lima_DSCL_2016.pdf: 2341451 bytes, checksum: e4310955dbc4f0c3af7730606a09c7f3 (MD5) Previous issue date: 2016-07-29 / O aminoácido glutamina (Gln) é precursor dos neurotransmissores cerebrais glutamato e GABA. O aumento de sua disponibilidade pode modular a excitabilidade cerebral. O objetivo deste trabalho foi descrever os efeitos do tratamento com diferentes doses de Gln, durante o desenvolvimento cerebral, sobre o comportamento de ansiedade, a depressão alastrante cortical (DAC) e a ativação da microglia no córtex de ratos recém-desmamados (D) e adultos (A). Os animais foram amamentados em ninhadas com 9 (L9; lactação normal) e com 15 filhotes (L15; lactação desfavorável). Do 7º ao 27º dia de vida pós-natal (P7-P27), os filhotes machos receberam por gavagem 250, 500 ou 750 mg/kg/dia de Gln (grupos Gln250, Gln500 e Gln750, respectivamente). Os grupos controles foram formados por animais que receberam o veículo (água destilada) no qual a Gln foi dissolvida por gavagem e por animais que não receberam gavagem (grupo ingênuo). Aos P28-P30 (D) e P88-P90 (A), os animais foram submetidos aos testes para comportamentos sugestivos de ansiedade no labirinto em cruz elevado (LCE) e no campo aberto. Dos P30-35 (D) ou P90-120 (A), registrou-se a DAC, obtendo-se dados de sua velocidade de propagação, duração e amplitude. Em seguida, os cérebros de alguns animais foram processados para imunomarcação com anticorpos anti-Iba1, específicos para microglia. No grupo D, os ratos tratados com Gln apresentaram um comportamento menos ansioso, tanto no LCE quanto no campo aberto. Este efeito ansiolítico da Gln foi mais evidente nos animais da condição L15. Na idade adulta (A), os grupos Gln500 e Gln750 da condição L15 percorreram uma maior distância e apresentaram menor tempo de imobilidade no LCE. Em relação à DAC, os animais da condição L15 apresentaram maior velocidade de propagação do que os correspondentes L9. Com exceção do grupo Gln250 da condição L15 na idade adulta, todos os grupos tratados com Gln apresentaram maior velocidade de propagação quando comparados aos respectivos controles. Além disso, esse efeito acelerador foi dependente da dose, uma vez que os grupos Gln500 e Gln750 apresentaram maiores velocidades de propagação do que os correspondentes Gln250. Quanto à reação da microglia, os animais tratados com Gln apresentaram maior imunorreatividade, tanto no córtex parietal quanto no hipocampo dos grupos D e A. Nos animais A da condição L9, a imunorreatividade da microglia e o percentual de área marcada foram maiores no grupo Gln500 do que no grupo Gln250. A partir desses resultados, sugere-se que o tratamento com Gln durante o período neonatal module a excitabilidade cerebral, resultando nas alterações eletrofisiológicas, comportamentais e imunohistoquímicas descritas neste estudo. Essas alterações persistem até a idade adulta e são dependentes da dose e da condição nutricional do animal. / The amino acid glutamine (Gln) is precursor of the brain neurotransmitters glutamate and GABA. Therefore, the increase of its availability can modulate brain excitability. The aim of this study was to describe the effects of treatment with different doses of Gln during brain development on anxiety-like behavior, cortical spreading depression (CSD) and microglial reaction in the cortex of developing (D) and adults (A) rats. Wistar rats were suckled in litters with 9 (L9; normal condition) or 15 (L15; unfavorable condition) pups. From 7th to 27th postnatal day (P7-P27), male rats received Gln by gavage at the doses of 250 mg/kg/day or 500 mg/kg/day or 750 mg/kg/day (respectively Gln250, Gln500 and Gln750 groups). The control groups were formed by animals that received vehicle which Gln was dissolved (distilled water) and animals that were not submitted to the gavage procedure (naive group). At P28-P30 (D) and P88-P90 (A), animals were tested in elevated plus maze (EPM) and open field. At P30-35 (D) and P90-120 (A), we recorded the CSD, obtaining data from its velocity of propagation, duration and amplitude. The brains of some animals were processed for microglial immunolabeling with anti-Iba-1 antibodies to analyze cortical microglia. In the D group, Gln treated rats showed less anxious behavior, both in EPM and open field. This anxiolytic effect of Gln was more evident in L15 condition. In adult rats (A), Gln500 and Gln750 groups of L15 condition traveled a greater distance and displayed shorter immobility time in the LCE when compared to controls. Regarding CSD, L15 animals presented with higher propagation velocity than the corresponding L9. Except for the Gln250 group of L15 condition in adulthood, all groups treated with Gln showed higher CSD velocity when compared to their respective controls. Moreover, the accelerating effect was dose dependent, since Gln500 and Gln750 groups displayed higher CSD velocity than the corresponding Gln250. Gln treated groups had greater immunoreactivity in both the parietal cortex and hippocampus. In adult rats of L9 condition, Gln500 group had greater immunoreactivity and higher percentage of labeled area when compared Gln250 group. Our findings suggest that neonatal treatment with Gln modulates brain excitability, resulting in the electrophysiological, behavioral and microglial alterations here described. These alterations persist into adulthood and are modulated by dose and lactation conditions.

Made available in DSpace on 2016-03-15T19:38:12Z (GMT). No. of bitstreams: 1 Douglas Nunes de Oliveira.pdf: 2639611 bytes, checksum: aa451c77b140c40c8a504474462ded1e (MD5) Previous issue date: 2008-09-17 / Probabilistic cellular automata can be used to model the spreading of contagious diseases in a population composed by susceptible, infected and recovered individuals. At each time step, a susceptible individual can either remain susceptible or contract the disease from infected individuals, where the probability related to the contagion depends on the number of infected individuals in contact with this susceptible individual. At each time step, an infected individual may (probabilistically) either remain infected or recuperate or die by the disease or die by other causes. A recovered individual, at each iteration, can either remain as he/she is or die. When an infected or recovered individual dies, a susceptible one appears in his/her place; thus, the population remains constant. Here, genetic algorithms are employed to identify the probability values concerning the processes of infection, cure and death, from epidemiological data from Arizona (USA) for measles. The goal is to obtain a model based on probabilistic rules of state transitions able of reproducing this time series and to verify the quality of the model prediction. This work reveals that the predictions are strongly influenced by the lattice dimension of the cellular automaton and by limitations imposed to the probability values. / Autômatos celulares probabilistas podem ser usados para modelar a propagação de doenças contagiosas numa população composta por indivíduos suscetíveis, infectados e recuperados da infecção. A cada passo de tempo, um indivíduo suscetível pode ou permanecer suscetível ou contrair a doença de infectados, sendo a probabilidade associada ao contágio dependente do número de infectados em contato com esse suscetível. A cada passo de tempo, um indivíduo infectado pode (probabilisticamente) permanecer infectado, ou se recuperar, ou morrer pela doença ou morrer de outras causas. Um indivíduo recuperado pode, a cada iteração, ou permanecer como está ou morrer. Quando um indivíduo infectado ou recuperado morre, nasce, em seu lugar, um suscetível, de modo que a população permanece constante. Aqui, algoritmos genéticos são empregados para identificar os valores das probabilidades associadas aos processos de infecção, recuperação e morte, a partir de dados epidemiológicos do Arizona (EUA) para catapora. O objetivo é obter um modelo baseado em regras probabilistas de transição de estados capaz de reproduzir essa série temporal e verificar a qualidade da previsão do modelo. Este trabalho revela que as previsões são fortemente influenciadas pelo tamanho do reticulado do autômato celular e por restrições impostas aos valores das probabilidades.