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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
261

A dinâmica do universo : Sir Arthur Eddington e as cosmologias relativísticas

Jurado Herrera, Nury Isabel 19 September 2002 (has links)
Orientador: Roberto de Andrade Martins / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-02T08:27:27Z (GMT). No. of bitstreams: 1 JuradoHerrera_NuryIsabel_M.pdf: 1195976 bytes, checksum: ca21c9b45a3155f88dc2049fb4dd06b3 (MD5) Previous issue date: 2002 / Resumo: A presente dissertação introduz as idéias básicas para o surgimento da teoria da relatividade geral e sua posterior aplicação na construção de modelos cosmológicos relativísticos. Desta forma é apresentado um estudo histórico detalhado do desenvolvimento das cosmologias relativísticas no período compreendido entre 1917 e 1930, começando com o próprio Albert Einstein que, em 1917, propôs o primeiro modelo desta natureza, e encerrando a análise com Sir Arthur Eddington em 1930, cujo modelo, "Lemaître-Eddington", engloba os avanços da época. A partir do modelo de Lemaître-Eddington estudamos o papel fundamental que Eddington atribui à constante cosmológica, é neste item que suas concepções epistemológicas ficam mais evidenciadas, embora elas estejam presentes desde seus primeiros trabalhos. Discutimos também sua argumentação para calcular as constantes da natureza por métodos puramente teóricos. Acompanhamos o desenvolvimento do formalismo matricial que Eddington apresenta para escrever a equação de Dirac para o elétron e, a partir desta nova notação, descrevemos os argumentos utilizados por Eddington para encontrar o valor da constante de estrutura fina, a razão entre a massa do próton e do elétron, a razão entre a força elétrica e a força gravitacional entre um próton e um elétron, a razão entre um comprimento de tipo atômico e o raio de curvatura natural do espaço. Enfim, este estudo analisa as fases do trabalho científico de Eddington estabelecendo uma ponte entre seu trabalho cosmológico e seu trabalho epistemológico / Abstract:The present dissertation introduce the basic ideas of the beginning of the general theory of relativity and its later application on the construction of relativistic cosmological models. So we present here a detailed historical study of the development of the relativistic cosmologies in the period between 1917 and 1930, starting with Albert Einstein who, in 1917, proposed the first model of this kind, and finishing the analysis with Sir Arthur Eddington in 1930, whose model, "Lemaître-Eddington", incorporate the progresses of that time. From the model of "Lemaître-Eddington" we study the basic rule Eddington gives to the cosmological constant. It is in this topic his epistemological concepts become more evident, even though it is present since his ½rst works. We also discuss Eddington's argumentation to calculate the constants of the nature by pure theoretical methods. We follow the development of the matrix formalism that Eddington presents to write the Dirac equation for the electron and from this new notation we describe the logic used by Eddington to find the value of fine structure constant, the rate between the proton and electron mass, the rate between the electrical and gravitational force between a proton and an electron, the rate between an atomic length and the natural spacial curvature radius. So, this essay analyzes the diÿerent periods of Eddington's scientific work establishing one bridge between his cosmological work and his epistemological work / Mestrado / Física / Mestre em Física
262

Um metodo Newton-GMRES globalmente convergente com uma nova escolha para o termo forçante e algumas estrategias para melhorar o desempenho de GMRES(m) / A globally convergent Newton-GMRES method with a new choice for the forcing term and some stragies to improve GMRES(m)

Toledo Benavides, Julia Victoria 17 June 2005 (has links)
Orientadores: Marcia A. Gomes Ruggiero, Vera Lucia da Rocha Lopes / Tese (doutorado) - Universidade Estadual de Campinas. Instituto de Matematica, Estatistica e Computação Cientifica / Made available in DSpace on 2018-08-04T14:53:24Z (GMT). No. of bitstreams: 1 ToledoBenavides_JuliaVictoria_D.pdf: 2835915 bytes, checksum: 1b77270a65a21cc42d9aa81819e4acc4 (MD5) Previous issue date: 2005 / Resumo: Neste trabalho, apresentamos um método de Newton inexato através da proposta de uma nova escolha para o termo forçante. O método obtido é globalizado através de uma busca linear robusta e suas propriedades de convergência são demonstradas. O passo de Newton inexato é obtido pela resolução do sistema linear através do método GMRES com recomeços, GMRES(m). Em testes computacionais observamos a ocorrência da estagnação em GMRES(m) e um acréscimo inaceitável na norma da função nas primeiras Iterações do método. Para contornar estas dificuldades são propostas estratégias de implementação computacional simples e que não exigem alterações internas no algoritmo do GMRES, possibilitando a interação com softwares já disponíveis. Exaustivos testes numéricos foram realizados, os quais nos permitiram concluir que a proposta para o termo for¸cante e as estratégias introduzidas foram bem sucedidas, resultando em um algoritmo robusto, com propriedade de convergência global e taxa superlinear de convergência / Abstract: In this work it is presented an inexact Newton method by a new choice for the forcing term. A globalization of the new method is done by introducing a robust line search strategy. Convergence properties are proved. The inexact Newton step is obtained through the restarted GMRES, GMRES (m), applied for solving the linear systems. Numerical experiments showed a stagnation of the GMRES (m) and also an occurrence of a great increase in the norm of the function at the initial iterations. Some strategies were proposed to avoid these drawbacks. These strategies are characterized by their simplicity of implementation and also by the fact that they do not need internal modifications of the GMRES algorithm. So, the interaction with available softwares are trivial. A bunch of numerical experiments were performed. With them it can be concluded that the new choice for the forcing term and the strategies incorporated in the algorithm were successfull. The resulting algorithm is then robust and has global convergence property with supelinear convergence rate / Doutorado / Doutor em Matemática Aplicada
263

Exploring the plasticity of chromosomal domains upon overexpression of silencing factors in Saccharomyces cerevisiae / Exploration de la plasticité de domaines chromosomiques sur la surexpression de facteurs silencieux dans Saccharomyces cerevisiae

Hocher, Antoine 29 September 2017 (has links)
La présence de domaines chromosomiques heterochromatiniens associé à des effets de position est une propriété communes à de nombreux génomes eukaryotes. L'intensité et l'étendue de la variégation liée aux effets de position sont généralement sensibles à la dose des protéines effectrices de l'hétérochromatine. Les propriétés d'auto-propagation des complexes d'hétérochromatine a un cout, qui est la nécessité d'établir des mécanismes stoppant la propagation de la répression transcriptionelle. Cette thèse explore la dose-dépendance de l'effet de position télomérique en étudiant le complexe SIR de la levure du boulanger. La caractérisation du groupement des télomères en foyers, de la localisation de Sir3 et de la transcription dans des souches sur-exprimant Sir3 a permis d'établir l'étendue maximale des domaines silencieux présent aux subtelomeres. L'étude de jeux de données publiés a révélé que ces domaines terminent généralement au niveau de zones correspondant où les propriétés de la chromatine montrent une transition importante. Ces transitions chromatiniennes sont requises pour survivre en présence d'un excès de protéines Sir3 puisque nous avons démontré que les mutants dot1 ne survivent pas un tel excès. En outre nous avons conduit un crible génétique qui a révélé de nombreux gènes requis pour la survie en présence d'une surdose de Sir3. Ce travail caractérise la réponse du génome à une surdose d'hétérochromatine et a permis de révéler des domaines subtélomeriques associés à des propriétés chromatiniennes particulières. En conséquence nous démontrons comment l'effet de position télomerique est efficacement restreint au subtelomere chez la levure. / A shared property of several eukaryotic genomes is the presence of heterochromatic chromosomal domains experiencing transcriptional variegation. The intensity and the extent of position effect variegation are sensitive to the dosage of silencing effectors in many systems. The self-propagating properties of heterochromatin machineries come with a cost, which is the requirement for mechanisms preventing ectopic spreading of silencing. This thesis explores the dose-dependency of telomere position effect, using the budding yeast SIR system as a model for chromatin based heterochromatic silencing. To assess the dose-dependency of telomere position effect in budding yeast, we systematically characterized the impact of Sir3 overexpression by quantifying the clustering of telomeres, the genome wide binding of Sir3 and its impact on coding and non coding transcription. Analysis of published data sets enabled to uncover candidates potentially responsible for the limitation of subtelomeric silent domains. Our study reveals that extension of silent domains can reach saturation, associated with the anti-silencing properties of histone marks deposited by the conserved enzyme Dot1. In addition we discovered genes required for viability upon SIR3 overexpression by conducting a genetic screen. Our work describes the dynamics of the dose dependency of heterochromatin propagation in budding yeast. It uncovers previously uncharacterized discrete chromosomal domains associated with specific chromatin features and demonstrates how telomere position effect is efficiently restricted to subtelomeres by the preexisting chromatin landscape.
264

Markov-modulated processes: Brownian motions, option pricing and epidemics

Simon, Matthieu 24 April 2017 (has links)
This thesis is devoted to the study of different stochastic processes which have a common feature: they are Markov-modulated, which means that their evolution rules depend on the state occupied by an underlying Markov process. In the first part of this thesis, we analyse the stationary distribution and various first passage problems for Markov-modulated Brownian motions (MMBMs) as well as for two extensions: MMBMs with jumps and MMBMs modified by a temporary change of regime upon visits to level zero. The second part of this thesis is devoted to the use of Markov-modulated processes in mathematical finance, more precisely for the calculation of different option prices. We use a Fourier transform approach to price different European options (vanilla, exchange and quanto options) in the case where the value of the considered risky assets evolves like the exponential of a Markov-modulated Lévy process. The third part of this thesis is devoted to the study of some stochastic epidemic processes, namely the SIR processes. In our models, a Markov process is used to modulate the behaviour of the individuals who bring the disease. We use different martingale approaches as well as matrix analytic methods to obtain various information about the state of the population when the epidemic is over. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
265

Modeling of Epizootics on Four Genera of Arabian Gulf Corals

Kluge, John Alexander 01 July 2015 (has links)
Coral colonies, from a reef near Abu Dhabi, United Arab Emirates (UAE), were counted and assessed for condition using photo-transects. An epidemic model, used to track how a communicable disease moves through a population, was constructed to help predict the future condition of this coral reef. In situ data from a disease outbreak that occurred in September 2011 provided a baseline for the model. Coral Populations of Porites, Platygyra, Acropora and Dipsastrea were modelled using condition categories that included Healthy, Black Band Disease Infected, Cyanobacteria Infected, Recovered, Recruits or Dead. Results from the modelling indicate that populations of Platygyra and Dipsastrea are healthy and growing, even with continued presence of diseases, due to the high rates of recovery (chance for host colony to overcome infection; high recovery rate = high chance of colony recovering from the infection) and low mortality rates (chance of dying from an infection; low mortality rate = low chance of a infected colony dying from the infection) in the genus. Porites showed no signs of population growth, but stabilized near its initial population size, despite having a high infection rate because population growth (recruitment) and recovery rate were canceled by a high mortality rate. Acropora showed a loss in population numbers over time, losing 25% of its population before the disease was eliminated. Diseases may have been eliminated from the Acropora population because population density was low and coral died quickly after becoming infected with a disease, due to the high mortality rate of this genus, before infecting other colonies. Acropora was the only genus to display what seems to be a density dependent infection rate, since chance of infection was reduced and then eliminated by the rapid mortality of infected colonies, if the population was higher disease spread may have been higher. In addition to results obtained using in situ data, higher modified infection rates were used to assess how they might impact these coral populations. Results suggest that all four genera seem to be resilient, shown by in situ modeling and parameters extracted from the phototransects, and able to withstand acute (rapid increase of infection rate which was then again quickly brought back to normal infection rate, an infection “spike”) increases of disease infection, which is shown by either a high recovery rate (Dipsastrea and Platygyra), a high recruitment/low mortality rate (Porites), or a high mortality rate (Acropora) that may not allow for the diseases to spread. However, all four genera would be slowly driven to extinction by a sustained (chronic) increase of disease infection rate brought on by growing stressors such as an increase in average water temperature or pollutants within the Gulf. These results demonstrate fragility of Gulf coral genera when exposed to chronic episodes of disease, which over time causes total collapse of the coral populations.
266

Comparison of the distribution of combined immunological and virological responses in adult HIV positive patients across Antiretroviral Therapy (ART)providers in Tshwane : a multilevel analysis

Wandai, Elia Muchiri January 2014 (has links)
Background: Immunological and virological responses to ART are important outcome indicators that are mostly used to evaluate the success of an ART program. A comparative performance between ART providers based on the two outcomes can be useful in optimising resources to underperforming providers and advising quality improvement plans. Aim: To compare immunological and virological responses of ART for adult HIV positive patients between providers in Tshwane District, Gauteng Province, South Africa. Methodology: This study was an analytical observational study that retrospectively compared patient treatment outcomes on immunological and virological responses between 16 Antiretroviral Therapy (ART) providers. The analysis compared baseline patients’ status on these two outcomes with their statuses after 6 and12 months on ART. Ordinary logistic regression was used to calculate Standardised Incidence Ratios (SIR), while multilevel model analysis was used to calculate specific provider random effects of poor immunological and virological responses. Results: After 6 months of treatment, the SIR of poor immunological outcome for all clinics under study, as predicted by the unadjusted logistic regression models was 0.29 (95% CI: 0.27-0.31), but varied from a low of 0.14 (95% CI: 0.00-0.40) to a high of 0.66 (95% CI: 0.13-1.20) between the clinics. Two clinics had a Standardised Incidence Ratio (SIR) of poor immunological response that was significantly below 1 (poor immunological rate below average), while three clinics had an SIR above 1 (poor immunological rate above average) under the unadjusted logistic models. After adjusting for the effects of gender, age, drug combination, religion and present virological status, no clinic had a SIR that was significantly below 1, but two clinics had a SIR that was significantly above 1. xi Under the logistic multilevel (MLLR) analysis, the unadjusted model flagged two clinics whose clinic specific effects were below zero (lower rate of poor immunological outcome below that of the total sample) and one clinic whose clinic specific effect was above zero (higher rate of poor immunological outcome below the total sample rate). The adjusted model showed that no clinic had residual effects that were significantly below or above zero. The confidence intervals for MLLR model were found not to be wider than those of the logistic regression (LR) models particularly for clinics with small sample sizes. A number of clinics changed the relative order of their SIR/random effects after case-mix adjustments under both the LR and MLLR modelling. For poor virological response, both the LRD and MLLR models indicated no clinic specific effects. The predicted poor virological response rate by the case-mix unadjusted LR model was 0.12 (95% CI 0.11 - 0.13). All clinics except one had SIRs that were not significantly different from 1. After adjusting for CD4 count and age, no clinic had an SIR that was significantly different from 1. Conclusions: Case-mix or patients baseline characteristics explained much of the variation in the Standardised Incidence Ratios (SIR) of poor immunological outcome after 6 months of patient treatment, while provider (clinic) specific effects explained much of the variation after 12 months of treatment. After 6 months of treatment, the results also showed that there were significant differences in the SIR between the clinics before case-mix adjustments, but the differences disappeared after case-mix adjustments. This shows that comparison of treatment outcomes between providers (clinics) can be misleading if no proper adjustment are made for confounding factors. Differences in the SIRs for poor virological outcome, after 6 months of patient treatment were no longer significant between clinics after taking account of CD4 count and age. / Dissertation (MSc)--University of Pretoria, 2014. / gm2014 / School of Health Systems and Public Health / unrestricted
267

Architecture and landscape design : an investigation into the harmonising of these two aspects of design as exemplified by the collaboration of Gertrude Jekyll and Sir Edwin Landseer Lutyens

Judge, Stephen Michael January 1996 (has links)
Sir Edwin Lutyens and Miss Gertrude Jekyll were part of the 'Art's and Crafts' movement, which advocated the use of local techniques and materials. They grew up separately, both in the Surrey country-side and both among creative people. Jekyll later worked with Edward Hudson (the author of 'Country Life') who persuaded her to be a garden designer . Lutyens was inspired first by the architecture of Surrey (mostly that of Norman Shaw), then by his friend, Herbert Baker, at architectural school, and lastly, by his long - time partner Jekyll. Munstead Wood, Surrey, England, was the partners' first project and it embodies nearly all of their ideals; the natural and indigenous use of flowers and plants, with an ordered colour scheme ; graded colour schemes without discord; the use of entirely local materials ; the sole use of local craftsmen and local techniques; a garden of 'rooms'; the intergration of architecture and garden design. A revival of interest in the partners work has helped to recreate some of the lost gardens of Jekyll. This interest has in turn put a spotlight on the ideals employed by the partners. Their wide influence has also produced many great buildings and gardens, most notably through the work of Sir Herbert Baker in South Africa. The Union Buildings are a perfect example of Baker's work, and much of it has the stamp of Lutyens' style and ideals. Through my own interest in Lutyens and Jekyll I have created my own Jekyll-style border in Grahamstown, Eastern Cape, to try and prove that her ideals can be translated into climates other than that of England. In this experiment, I succeeded in using indigenous South African plants and flowers with a colour scheme in the style of Jekyll, proving that the ideals to which she aspired could be applied in other countries.
268

The political career of Sir Richard McBride

Hunt, Peter Roberts January 1953 (has links)
During recent years the Canadian political scene has suffered from a dearth of colour. Indeed, it has almost been forgotten how politically influential and successful a colourful figure can be. This thesis constitutes in part a reminder of this fact. Here is the story of the most popular premier in the history of the province of British Columbia, Richard McBride, the man who came to his high office at the age of thirty-two (the youngest premier in our history), and stayed in power over twelve years (the longest term of office in our history). He was the man who introduced party government to the province and thereby headed the first Conservative government in B.C. history. At the head of this government he directed provincial affairs during the greatest boom, bar the present one, to ever hit this province. At his last election he accomplished the remarkable success of sweeping from the Legislature every representative of the hitherto chief Opposition party, the Liberals. Forty Conservatives faced two Socialists. In federal affairs McBride became one of the leading figures in the Conservative party and, in 1911, Robert Borden's closest rival for the right to lead the Conservatives to victory in the Reciprocity Election. He thus came closer than any other West Coast politician to becoming Prime Minister of Canada. In imperial affairs he also achieved considerable prominence. He cut a striking figure in London and became personally acquainted with many important imperial figures such as Winston Churchill. It was as ambassador for his province that he found his most effective role. This man from New Westminster does on the above record bulk larger than any other figure in the history of local politics. Another purpose of this thesis is to discover to what extent McBride's ability and achievement made him worthy of this prestige. In chapter one, McBride's rise to power is described; from the early days in law in New Westminster, through his first political plunge (a failure), his first political success (in 1898), his first cabinet position (with Premier Dunsmuir in 1900), his resignation from that cabinet and leadership of the Opposition to the Dunsmuir and Prior governments, to his call to the premiership in June, 1905. Chapter two deals with his difficulties in forming and carrying out the decision to form a government along strict party lines. This decision was put to the test in the election of October, 1905. Chapter three tells of the governmental success in combating financial insolvency, a success resulting from a strict retrenchment policy which was the work of McBride's first rate Finance Minister, R.G. Tatlow, and aided to at least some small extent by the Premier's attempt to get Better Terms out of Ottawa (in other words an increased financial subsidy). McBride became more widely known through his role in the Better Terms fight, the climax of which was reached at Ottawa in October, 1906. Chapter four attempts to explain those railway entanglements, which the McBride government found impossible to avoid in the period 1903 to 1906, and to estimate the results these entanglements in terms of the 1907 election. Chapter five records a change in government policy, with the Premier acting more boldly on the basis of better times and a larger majority. A discussion of his trip to England in the interests of Better Terms, is followed by an appreciation of the significance of the 1907 cabinet changes, and of some of the policies affected by these changes. The chapter concludes with an account of the government's decision to guarantee the bonds of the Canadian Northern Railway Company in order to persuade that Company to build to the Pacific, and an analysis of the results of this decision, results which included two resignations and another election, in November, 1909. Chapter six deals with the peak of the boom and concomitantly the peak of Conservative success and popularity. The second phase of McBride's railway policy is described as is his electoral triumph in 1912. The Premier's activities in the federal field and in England are also discussed. All these activities show him at the zenith of his personal success in this period, Chapter seven deals with the depression and the decline in popularity suffered by the McBride government from 1913 to 1915. This decline takes place in three stages as the outbreak of war provides an imperialistic interlude, a hesitation before the final collapse. At the end of this chapter is an analysis of Sir Richard's decision to resign. Chapter eight is a short appreciation of McBride as a colourful figure whose very virtues as a man constituted his worst failings as a statesman. Nevertheless it is concluded that as a man of vision he had an important role in the development of the province. / Arts, Faculty of / History, Department of / Graduate
269

Idealized world of Malory's "Morte Darthur" : a study of the elements of myth, allegory, and symbolism in the secular and religious milieux of Arthurian Romance

Whitaker, Muriel A. I. January 1970 (has links)
Towards the end of the Middle Ages, Sir Thomas Malory synthesized the diverse elements of British chronicle history, Celtic myth, French courtoisie, and Catholic theology which over a period of six hundred years or more had gathered about the legendary figure of King Arthur. Furthermore, Malory presented in definitive form the kind of idealized milieu that later writers in English came to regard as romantic. Malory's Morte Darthur presents dramatically the activities of a mythic aristocratic society living in a golden age. It preserves the "history" of a British king who defeats the Emperor of Rome and establishes an empire stretching from Ireland and Scandinavia to the Eastern Mediterranean. It portrays the adventures of heroic knights whose prowess is inspired by idealized ladies and whose achievements are helped or hindered by such supernatural agents as fays, magicians, giants, dwarfs, angels and devils. The actions of the knights conform to a ritualistic pattern of quest and combat determined by stereotyped chivalric conventions and performed in a symbol-studded environment. Colours, numbers, costumes, metals, arms, armour, and horses have symbolic significances which may be hierarchic, emotive or moral. Castles and perilous forests represent the antithetical values of security and danger, peace and combat, civilization and primitivism, love and hate. In this antipodal environment occur encounters which often adumbrate a struggle between forces of good and forces of evil. In the religious milieu of the Grail quest, elements of the secular milieu are adopted for the purpose of expressing truths of Catholic faith and morality. The Grail Knight's search for Corbenic is an allegory of the soul's search for God. Arms and armour, dress and colours, animals and plants have symbolic significances drawn from Biblical exegesis and Christian art. The unifying element in the historical, romantic and religious milieux is the quest motif; it is the means by which the ideals of the Malorian world are revealed. The historical quest for the crown of Rome shows Malory's view of sovereignty and the ideal of the good king. The romantic quest for fame and fair ladies shows his view of chivalry and the ideal of the good knight. The spiritual quest for the Holy Grail shows his view of religion and the ideal of the good Christian. It is a measure of Malory's art that the wishfulfilling dream world of romance projects an illusion of reality. / Arts, Faculty of / English, Department of / Graduate
270

Appropriating the Restoration: Fictional Place and Time in Works by Daniel Defoe, Sir Walter Scott and Rose Tremain

Slagle, Judith Bailey 19 March 2015 (has links)
While authors have appropriated literary works for centuries, they have also appropriated historical settings and places well outside their own realities, creating new works in historical settings that reflect a new cultural purpose. The Restoration and eighteenth century are frequent subjects of popular formula-fiction romances due to the distinctive, easily replicated atmospheres; but the period has also inspired serious, traditional historical fiction and fictionalized biography as well as productions of novels from the period. This panel focuses on the long eighteenth century and the period’s intrigue for filmmakers, TV producers and audiences in a modern-day culture

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