A acidez do solo é um dos principais fatores limitantes à produção vegetal. Apesar da toxicidade por alumínio ter sido extensamente investigada, pouca atenção tem sido dada ao estresse causado pelo baixo pH em si. Existem diferenças marcantes entre células quanto à sensibilidade ao pH baixo que dependem do seu estado de crescimento e desenvolvimento celular e que devem ser exploradas para se entender o que determina a sensibilidade e tolerância a pH baixo. Em alguns casos, a suscetibilidade a pH baixo está relacionada a desarranjos na parede de células em crescimento, chegando a causar o rompimento da célula, como já foi demonstrado em pêlos radiculares em expansão. Por outro lado, o metabolismo oxidativo e a geração de espécies reativas de oxigênio (ROS) na parede podem influenciar neste processo por romper ou criar ligações dentro ou entre cadeias de polissacarídeos, modulando assim a extensibilidade da parede celular. Em células de tabaco (Nicotiana tabacum) cv. BY-2, há um aumento acentuado na sensibilidade ao pH baixo no final da fase lag da cultura, que ocorrre entre 12 e 24 h de cultivo. Os objetivos deste trabalho foram: a) Investigar se a mudança na sensibilidade pH baixo ocorre durante a retomada do ciclo celular e determinar, com o uso de inibidores do ciclo celular, o período do ciclo em que isto ocorre; b) verificar se o aumento da sensibilidade a pH baixo está relacionado com a expansão celular ou com alterações no potencial osmótico da célula; c) examinar o efeito da aplicação de H2O2 ou ascorbato sobre a resposta de células sensíveis a pH baixo; d) testar a hipótese de que a sensibilidade a pH baixo pode ser revertida por meio de um choque hipo-osmótico prévio; e) avaliar o possível papel da modulação oxidativa da parede celular na reversão de sensibilidade das células a pH baixo expostas ao choque hipo-osmótico. A retomada do ciclo celular é necessária para que ocorra a alteração de sensibilidade a pH baixo, pois a remoção de auxina (2,4-D) ou a adição de bloqueadores de canais de K+ impediu ou atrasou, respectivamente, a alteração na sensibilidade a pH baixo. O uso de inibidores do ciclo celular demonstrou que as células de BY-2 se tornam mais sensíveis a pH baixo durante o final da fase G1 mas antes do ponto de checagem da transição G1/S do ciclo celular. A aplicação de H2O2, diminuiu a suscetibilidade das células a pH baixo, ao contrário da aplicação de ascorbato. Foi demonstrado que a aplicação prévia de tratamento hipo-osmótico por 60 min reverteu a sensibilidade de células a pH baixo. A aplicação de inibidores de NAPDH oxidase da membrana plasmática e de peroxidases revelou a participação destas enzimas na reversão de sensibilidade das células a pH baixo, indicando a possibilidade de geração de ROS e de modulação oxidativa da parede. Embora já tenha sido descrito que ocorre uma explosão oxidativa com choque hipo-osmótico, ainda não havia sido demonstrado a conseqüência disto. Este trabalho fornece indícios de que uma explosão oxidativa poderia modificar a parede tornando-a mais resistente e a célula menos suscetível a pH baixo / Soil acidity is a major factor limiting plant growth worldwide. Although aluminum toxicity, which occurs only at low pH, has been extensively studied, little attention has been given to stress caused by low pH. There are marked differences in the sensitivity of cells to low pH which are contingent on the growth and developmental stage of the cells. These differences should be explored to further the understanding of the factors governing sensitivity and tolerance to low pH. In at least some cases, the susceptibility of cells to low pH is related to derangements in the wall of growing cells, which can cause ruptures or bursting of the cells, as has been clearly demonstrated in expanding root hairs. On the other hand, the oxidative metabolism and generation of reactive oxygen species (ROS) can modulate cell wall extensibility by breaking or making bonds within and between cell wall polymers. In tobacco (Nicotiana tabacum) cv. BY-2 cells, there is a sharp increase in sensitivity to low pH at the end of the lag phase of the cell culture, which occurs between 12 and 24 h of subculture. The objectives of this study were: a) determine if the changes in sensitivity to low pH occurred during the restart of the cell cycle and, by employing cell cycle inhibitors, at which points of the cycle does this occur; b) examine if the changes in sensitivity to low pH are related to cell expansion or changes in osmotic potential of the cell; c) examine how the application of H2O2 or ascorbate affects the response of cells to low pH; d) test the hypothesis that sensitivity of cells to low pH can be reverted by the previous application of a hypo-osmotic shock; e) evaluate the possible role of oxidative modulation of the cell wall in hypo-osmotic-induced reversal of the sensitivity of cells to low pH. The restart of the cell cycle was shown to be necessary for the change in sensitivity to low pH occur, since the absence of auxin (2,4-D) or the addition of K+ channel blockers prevented or delayed this change, respectively. The use of cell cycle inhibitors demonstrated that BY-2 cells become sensitive to low pH at the end of G1 but before the G1/S transition restriction point of the cell cycle. Exogenous H2O2, but not ascorbate, reduced the effect of low pH on sensitive cells. Sensitive cells submitted to 60 min hypo-osmotic treatment became insensitive to low pH. This reversal of sensitivity depended on the activity of plasma membrane NADPH oxidase and peroxidase, as evidenced by the use of DPI and SHAM, inhibitors of these enzymes, respectively. This suggests that ROS is generated and that oxidative modifications of the cell wall occur. Although hypo-osmotic treatments have been shown to generate an oxidative burst, its purpose or implication has not yet been shown. This study provides evidence that an oxidative burst might modify and strengthen the cell wall, making cells less susceptible to low pH

Synthetic vascular grafts are useful to bypass diseased arteries. The long-term failure of synthetic grafts is primarily due to intimal hyperplasia at the anastomotic sites. The accelerated intimal hyperplasia may stem from a compliance mismatch between the host artery and the graft since commercially available synthetic conduits are much stiffer than an artery. The objective of this thesis is to design a method for fabricating a vascular graft that mechanically matches the patients native artery over the expected physiologic range of pressures. The creation of an optimized mechanical graft will hopefully lead to an improvement in patency rates. The mechanical equivalency between the graft and the host artery is defined locally by several criteria including the diameter upon inflation, the elasticity at mean pressure, and axial force. A single parameter mathematical for a thin-walled tube is used to describe of the final mechanical behavior of a synthetic graft. For the general problem, the objective would be to fabricate a mechanics-matching vascular graft for each host artery. Typically, fabrication parameters are set initially and the properties of the fabricated graft are measured. However, by modeling the entire fabrication process and final mechanical properties, it is possible to invert the situation and let the typical output mechanical values be used to define the fabrication parameters. The resultant fabricated graft will then be mechanically matching. As a proof-of-concept, several prototype synthetic grafts were manufactured and characterized by a single Invariant to match a canine artery. The resultant graft equaled the diameter upon inflation, the elasticity at mean pressure, and axial force of the native canine artery within 6%. An alternative to making an individual graft for each artery is also presented. A surgeon may choose the best graft from a set of pre-manufactured grafts, using a computer program algorithm for best fit using two parameters in a neighborhood. The design optimization problem was solved for both canine carotid and human coronary arteries. In conclusion, the overall process of design, fabrication and selection of a mechanics matching synthetic vascular graft is shown to be reliable and robust.

Les réseaux optiques à commutation de rafales (OBS) sont des candidats pour jouer un rôle important dans le cadre des réseaux optiques de nouvelle génération. Dans cette thèse, nous nous intéressons au routage adaptatif et au provisionnement de la qualité de service dans ce type de réseaux. Dans une première partie de la thèse, nous nous intéressons à la capacité du routage multi-chemins et du routage alternatif (par déflection) à améliorer les performances des réseaux OBS, pro-activement pour le premier et ré-activement pour le second. Dans ce contexte, nous proposons une approche basée sur l’apprentissage par renforcement où des agents placés dans tous les nœuds du réseau coopèrent pour apprendre, continuellement, les chemins du routage et les chemins alternatifs optimaux selon l’état actuel du réseau. Les résultats numériques montrent que cette approche améliore les performances des réseaux OBS comparativement aux solutions proposées dans la littérature. Dans la deuxième partie de cette thèse, nous nous intéressons au provisionnement absolu de la qualité de service où les performances pire-cas des classes de trafic de priorité élevée sont garanties quantitativement. Plus spécifiquement, notre objectif est de garantir la transmission sans pertes des rafales de priorité élevée à l’intérieur du réseau OBS tout en préservant le multiplexage statistique et l’utilisation efficace des ressources qui caractérisent les réseaux OBS. Aussi, nous considérons l’amélioration des performances du trafic best effort. Ainsi, nous proposons deux approches : une approche basée sur les nœuds et une approche basée sur les chemins. Dans l’approche basée sur les nœuds, un ensemble de longueurs d’onde est assigné à chaque nœud du bord du réseau OBS pour qu’il puisse envoyer son trafic garanti. Cette assignation prend en considération les distances physiques entre les nœuds du bord. En outre, nous proposons un algorithme de sélection des longueurs d’onde pour améliorer les performances des rafales best effort. Dans l’approche basée sur les chemins, le provisionnement absolu de la qualité de service est fourni au niveau des chemins entre les nœuds du bord du réseau OBS. À cette fin, nous proposons une approche de routage et d’assignation des longueurs d’onde qui a pour but la réduction du nombre requis de longueurs d’onde pour établir des chemins sans contentions. Néanmoins, si cet objectif ne peut pas être atteint à cause du nombre limité de longueurs d’onde, nous proposons de synchroniser les chemins en conflit sans le besoin pour des équipements additionnels. Là aussi, nous proposons un algorithme de sélection des longueurs d’onde pour les rafales best effort. Les résultats numériques montrent que l’approche basée sur les nœuds et l’approche basée sur les chemins fournissent le provisionnement absolu de la qualité de service pour le trafic garanti et améliorent les performances du trafic best effort. En outre, quand le nombre de longueurs d’ondes est suffisant, l’approche basée sur les chemins peut accommoder plus de trafic garanti et améliorer les performances du trafic best effort par rapport à l’approche basée sur les nœuds. / Optical Burst Switching (OBS) networks are candidates to play an important role in the context of next generation optical networks. In this thesis, we are interested in adaptive routing and quality of service provisioning for these networks. In the first part of the thesis, we study the capability of multi-path routing and alternative routing (deflection routing) to improve the performance of the OBS network proactively for the former and reactively for the latter. In this context, we propose a reinforcement learning-based approach where learning agents, placed in each OBS node, cooperate to learn, continuously, optimal routing paths and alternative paths according to the current state of the network. Numerical results show that the proposed approach improves the performance of the OBS network compared to existing solutions in the literature. In the second part of the thesis, we consider the problem of absolute quality of service provisioning for OBS networks where worst-case performance of high priority traffic is guaranteed quantitatively. Particularly, we are interested in the loss-free transmission, inside the OBS network, of high priority bursts, while preserving statistical multiplexing gain and high resources utilization of the OBS network. Also, we aim to improve the performance of best effort traffic. Hence, we propose two approaches: (a) the node-based approach; and (b) the path-based approach. In the node-based approach, we propose to assign a set of wavelengths to each OBS edge node that it can use to send its guaranteed traffic. This assignment takes into consideration physical distances between edge nodes. Furthermore, we propose a wavelength selection algorithm to improve the performance of best effort bursts. In the path-based approach, absolute quality of service provisioning is offered at end-to-end path level. To do this, we propose a routing and wavelength assignment approach which aims to reduce the number of wavelengths required to establish contention free paths. Nevertheless, if this objective cannot be reached because of the limited number of wavelengths in each fiber link, we propose an approach to synchronize overlapping paths without the need for additional equipments for synchronization. Here again, we propose a wavelength selection algorithm for best effort bursts. Numerical results show that both the node-based and the path-based approaches successfully provide absolute quality of service provisioning for guaranteed traffic and improve the performance of best effort traffic. Also, path-based approach could accommodate more guaranteed traffic and improve the performance of best effort traffic compared to node-based approach when the number of wavelengths is sufficient.

This Ph.D. dissertation processes and analyzes signals from the neonatal intensive care units (NICUs) for the study of maturity, systemic infection (sepsis) and the influence of immunization in the premature newborn. A special attention is payed to the electroencephalography and the breathing signal. The former is often contaminated by several sources of noise, thus methods based on the signals decomposition and optimal noise cancellation, adapted to the characteristics of the immature EEG, were proposed and evaluated objectively on real and simulated signals. By means of the EEG and delta burst analysis, detected automatically by a proposed classifier, infant's maturation and the effects of vaccination are studied. Concerning the second signal, breathing, non-linear and fractal methods are adapted to evaluate maturity and sepsis. A robustness study of estimation methods is also conducted, showing that the Hurst exponent, estimated on respiratory variability signals, is a good detector of infection.

Red alder (Alnus rubra Bong.) is the only tree in British Columbia and the Northwest US to engage in actinorhizal symbiosis to fix atmospheric nitrogen. This study was conducted to explore the plasticity in growth and physiology among 58 17-year-old red alder families in response to variation in climate in two common garden plots, one at Bowser, BC and one at Terrace, BC. Physiological assessments included height and diameter growth, bud flush, water use efficiency as measured by δ13C, cold hardiness as measured by controlled freezing and electrolyte leakage, autumn leaf senescence, and instantaneous and seasonally integrated rates of nitrogen fixation as measured by acetylene reduction and natural abundance δ15N isotope analysis, respectively. Significant differences were identified among families for growth (height and diameter), bud burst stage, leaf senescence, cold hardiness, and bud nitrogen content. No significant differences among families were identified for water use efficiency as measured by δ13C, or for rates of nitrogen fixation as measured by either acetylene reduction or natural abundance δ15N. This study identified possible adaptive differences among red alder genotypes, especially in traits such as bud flush timing, cold hardiness, or nitrogen fixation and their respective contributions to growth. These differences often reflected a tradeoff between growth and the ability to tolerate an extreme environment. Cold hardiness results indicate that red alder families are well adapted to their climate of origin, and may not be able to acclimate sufficiently to a northward assisted migration of genotypes. Nitrogen fixation results demonstrated gaps in our current knowledge of Frankia distribution and impact on the actinorhizal symbiosis in British Columbia. / Graduate

Thesis (Ph. D.)--Uniformed Services University of the Health Sciences, 2005. / Typescript (photocopy).

A acidez do solo é um dos principais fatores limitantes à produção vegetal. Apesar da toxicidade por alumínio ter sido extensamente investigada, pouca atenção tem sido dada ao estresse causado pelo baixo pH em si. Existem diferenças marcantes entre células quanto à sensibilidade ao pH baixo que dependem do seu estado de crescimento e desenvolvimento celular e que devem ser exploradas para se entender o que determina a sensibilidade e tolerância a pH baixo. Em alguns casos, a suscetibilidade a pH baixo está relacionada a desarranjos na parede de células em crescimento, chegando a causar o rompimento da célula, como já foi demonstrado em pêlos radiculares em expansão. Por outro lado, o metabolismo oxidativo e a geração de espécies reativas de oxigênio (ROS) na parede podem influenciar neste processo por romper ou criar ligações dentro ou entre cadeias de polissacarídeos, modulando assim a extensibilidade da parede celular. Em células de tabaco (Nicotiana tabacum) cv. BY-2, há um aumento acentuado na sensibilidade ao pH baixo no final da fase lag da cultura, que ocorrre entre 12 e 24 h de cultivo. Os objetivos deste trabalho foram: a) Investigar se a mudança na sensibilidade pH baixo ocorre durante a retomada do ciclo celular e determinar, com o uso de inibidores do ciclo celular, o período do ciclo em que isto ocorre; b) verificar se o aumento da sensibilidade a pH baixo está relacionado com a expansão celular ou com alterações no potencial osmótico da célula; c) examinar o efeito da aplicação de H2O2 ou ascorbato sobre a resposta de células sensíveis a pH baixo; d) testar a hipótese de que a sensibilidade a pH baixo pode ser revertida por meio de um choque hipo-osmótico prévio; e) avaliar o possível papel da modulação oxidativa da parede celular na reversão de sensibilidade das células a pH baixo expostas ao choque hipo-osmótico. A retomada do ciclo celular é necessária para que ocorra a alteração de sensibilidade a pH baixo, pois a remoção de auxina (2,4-D) ou a adição de bloqueadores de canais de K+ impediu ou atrasou, respectivamente, a alteração na sensibilidade a pH baixo. O uso de inibidores do ciclo celular demonstrou que as células de BY-2 se tornam mais sensíveis a pH baixo durante o final da fase G1 mas antes do ponto de checagem da transição G1/S do ciclo celular. A aplicação de H2O2, diminuiu a suscetibilidade das células a pH baixo, ao contrário da aplicação de ascorbato. Foi demonstrado que a aplicação prévia de tratamento hipo-osmótico por 60 min reverteu a sensibilidade de células a pH baixo. A aplicação de inibidores de NAPDH oxidase da membrana plasmática e de peroxidases revelou a participação destas enzimas na reversão de sensibilidade das células a pH baixo, indicando a possibilidade de geração de ROS e de modulação oxidativa da parede. Embora já tenha sido descrito que ocorre uma explosão oxidativa com choque hipo-osmótico, ainda não havia sido demonstrado a conseqüência disto. Este trabalho fornece indícios de que uma explosão oxidativa poderia modificar a parede tornando-a mais resistente e a célula menos suscetível a pH baixo / Soil acidity is a major factor limiting plant growth worldwide. Although aluminum toxicity, which occurs only at low pH, has been extensively studied, little attention has been given to stress caused by low pH. There are marked differences in the sensitivity of cells to low pH which are contingent on the growth and developmental stage of the cells. These differences should be explored to further the understanding of the factors governing sensitivity and tolerance to low pH. In at least some cases, the susceptibility of cells to low pH is related to derangements in the wall of growing cells, which can cause ruptures or bursting of the cells, as has been clearly demonstrated in expanding root hairs. On the other hand, the oxidative metabolism and generation of reactive oxygen species (ROS) can modulate cell wall extensibility by breaking or making bonds within and between cell wall polymers. In tobacco (Nicotiana tabacum) cv. BY-2 cells, there is a sharp increase in sensitivity to low pH at the end of the lag phase of the cell culture, which occurs between 12 and 24 h of subculture. The objectives of this study were: a) determine if the changes in sensitivity to low pH occurred during the restart of the cell cycle and, by employing cell cycle inhibitors, at which points of the cycle does this occur; b) examine if the changes in sensitivity to low pH are related to cell expansion or changes in osmotic potential of the cell; c) examine how the application of H2O2 or ascorbate affects the response of cells to low pH; d) test the hypothesis that sensitivity of cells to low pH can be reverted by the previous application of a hypo-osmotic shock; e) evaluate the possible role of oxidative modulation of the cell wall in hypo-osmotic-induced reversal of the sensitivity of cells to low pH. The restart of the cell cycle was shown to be necessary for the change in sensitivity to low pH occur, since the absence of auxin (2,4-D) or the addition of K+ channel blockers prevented or delayed this change, respectively. The use of cell cycle inhibitors demonstrated that BY-2 cells become sensitive to low pH at the end of G1 but before the G1/S transition restriction point of the cell cycle. Exogenous H2O2, but not ascorbate, reduced the effect of low pH on sensitive cells. Sensitive cells submitted to 60 min hypo-osmotic treatment became insensitive to low pH. This reversal of sensitivity depended on the activity of plasma membrane NADPH oxidase and peroxidase, as evidenced by the use of DPI and SHAM, inhibitors of these enzymes, respectively. This suggests that ROS is generated and that oxidative modifications of the cell wall occur. Although hypo-osmotic treatments have been shown to generate an oxidative burst, its purpose or implication has not yet been shown. This study provides evidence that an oxidative burst might modify and strengthen the cell wall, making cells less susceptible to low pH

In this thesis we provide a model for a bufferless optical burst switching (OBS) and an optical packet switching (OPS) network. The thesis is divided in three parts. <p><p>In the first part we introduce the basic functionality and structure of OBS and OPS networks. We identify the blocking probability as the main performance parameter of interest. <p><p>In the second part we study the statistical properties of the traffic that will likely run through these networks. We use for this purpose a set of traffic traces obtained from the Universidad Politécnica de Catalunya. Our conclusion is that traffic entering the optical domain in future OBS/OPS networks will be long-range dependent (LRD). <p><p>In the third part we present the model for bufferless OBS/OPS networks. This model takes into account the results from the second part of the thesis concerning the LRD nature of traffic. It also takes into account specific issues concerning the functionality of a typical bufferless packet-switching network. The resulting model presents scalability problems, so we propose an approximative method to compute the blocking probability from it. We empirically evaluate the accuracy of this method, as well as its scalability. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Ce mémoire de thèse porte sur le traitement et l'analyse des signaux issus des unités de soins intensifs néonatales (USIN) pour l'étude de la maturité, de l'infection généralisée et de l'influence de l'immunisation chez le nouveau-né prématuré. Une attention particulière est portée sur l'électroencéphalographie et le signal de respiration. Pour le premier, ce signal est souvent bruité en USIN et des méthodes de décomposition du signal et d'annulation optimale du bruit, adaptées aux particularités des EEG immatures, ont été proposées et évaluées objectivement sur signaux réels et simulés. L'analyse de l'EEG et des bouffées delta, repérées automatiquement par un classificateur proposé, ont permis d'étudier la maturation et les effets de la vaccination. Pour la seconde modalité, la respiration, des méthodes non-linéaires et fractales sont retenues et adaptées pour évaluer la maturité et l'infection généralisée. Une étude de robustesse des méthodes d'estimation est menée et on montre que l'exposant de Hurst, estimé sur des signaux de variabilité respiratoire, est un bon détecteur de l'infection. / This Ph.D. dissertation processes and analyzes signals from the neonatal intensive care units (NICUs) for the study of maturity, systemic infection (sepsis) and the influence of immunization in the premature newborn. A special attention is payed to the electroencephalography and the breathing signal. The former is often contaminated by several sources of noise, thus methods based on the signals decomposition and optimal noise cancellation, adapted to the characteristics of the immature EEG, were proposed and evaluated objectively on real and simulated signals. By means of the EEG and delta burst analysis, detected automatically by a proposed classifier, infant's maturation and the effects of vaccination are studied. Concerning the second signal, breathing, non-linear and fractal methods are adapted to evaluate maturity and sepsis. A robustness study of estimation methods is also conducted, showing that the Hurst exponent, estimated on respiratory variability signals, is a good detector of infection.

The master’s thesis deals with the noise diagnostic in the solar cells. Describes the main kinds of noises. The samples were quality and reliability screened using noise reliability indicators. The samples were surveyed by measuring the I-V characteristics, the noise spectral density as a function of forward voltage and frequency. It was calculated the noise spectral density as a function of forward current.