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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.
11

Investigações sobre o controle motor e postural nas assimetrias em membros inferiores / Investigations about motor and postural control during asymmetries in lower limbs

Paulo Henrique Marchetti 15 December 2009 (has links)
Durante diferentes atividades cotidianas ou esportivas o ser humano é submetido a desafios unilaterais que podem estar relacionados à performance de uma tarefa específica ou a própria manutenção de sua postura. Portanto, é natural o desenvolvimento motor de um membro em relação ao outro para tarefas específicas, desde que estas sejam repetidas de forma não simétrica. Desta forma, pode-se supor que sujeitos que possuam maiores estresses físicos unilaterais apresentem maior probabilidade em desenvolver assimetrias funcionais e morfológicas. O presente trabalho apresenta três diferentes experimentos visando investigar as assimetrias funcionais e morfológicas relacionadas ao controle de movimento para tarefas dinâmicas e estáticas em diferentes condições e grupos. O primeiro experimento visou investigar as diferenças, entre os membros inferiores, no controle de movimento entre sedentários e atletas, utilizando para isto a postura ereta quieta e o salto com contra-movimento nas condições bipedais e unipedais. O segundo experimento visou investigar o efeito da fadiga neuromuscular unilateral e bilateral no controle de movimento, entre membros, durante o salto com contra-movimento e a postura ereta quieta bipedal. O terceiro experimento objetivou investigar o efeito prolongado da temporada esportiva no controle de movimento, entre membros, de atletas, utilizando o salto com contra-movimento e a postura ereta quieta nas condições unipedal e bipedal. Inicialmente, o presente trabalho concluiu que não parece existir relação entre as diferenças antropométricas e funcionais. Indivíduos sedentários e atletas possuem diferenças entre os membros inferiores, entretanto supõe-se que os mecanismos relacionados à tais fenômenos não sejam os mesmos, como no caso dos sedentários, onde as assimetrias poderiam estar relacionadas ao pobre controle de força, sinergismo e padrão de coordenação.. Analisando as diferenças entre sedentários e atletas foram observadas semelhanças em relação ao nível de assimetria para algumas variáveis analisadas. Deve-se considerar que os atletas analisados estavam no início da temporada esportiva, e possivelmente sem grande influência dos efeitos do treinamento prolongado. Para testar a hipótese do efeito prolongado, o terceiro experimento foi realizado e observou-se que a temporada esportiva não afetou todas as variáveis relacionadas ao controle de movimento estático e dinâmico em atletas e os maiores efeitos foram verificados durante as tarefas bipedais. Além disto, a fadiga neuromuscular também influenciou o controle de movimento em sedentários, produzindo ajustes compensatórios em algumas variáveis, principalmente nos ângulos articulares. Entretanto, as assimetrias previamente observadas não parecem serem alteradas durante as diferentes condições de fadiga neuromuscular. Para a tarefa dinâmica bipedal, observou-se que para todas as variáveis analisadas (ângulos articulares, parâmetros de desempenho e atividade muscular) apresentaram assimetrias. Curiosamente, se observa tendência à maior ativação do membro contra-lateral em função do membro fatigado. Portanto, o presente estudo ressalta o efeito do nível de condicionamento, o efeito da fadiga e do treinamento prolongado no controle de movimento dos membros inferiores em tarefas com diferentes demandas motoras bipedais e unipedais / The human body is exposed to different unilateral challenges during different daily and sportive tasks. These challenges may either be related to specific-task performance or posture maintenance. Thus, it is natural the increase of motor control in one limb related to another during specific tasks and movements. It can be assumed that individuals exposed to higher physical unilateral stress show greater probability to develop functional and morphological asymmetries. The present study shows three different experiments in order to investigate the functional and morphological asymmetries related to the motor control for dynamic and static tasks in different conditions and groups. The first experiment aimed to investigate the differences between the lower limbs, related to the motor control between sedentary and athletes during two tasks: quiet stance and countermovement jump in bi- and unipedal conditions. The second experiment aimed to investigate the effect of neuromuscular fatigue on uni- and bilateral tasks related to the motor control between lower limbs during both double-leg tasks: countermovement jump and quiet stance. The third experiment aimed to investigate the effect of prolonged sportive season in motor control, between lower limbs, during two tasks: quiet stance and countermovement jump in bi- and unipedal conditions. We concluded that there was no correlation between the anthropometric and functional asymmetries. Both sedentary and athlete groups had differences between the lower limbs in several variables, however it is assumed that the mechanisms related to such phenomena are not the same. There were similarities between sedentary and athlete groups related to the level of asymmetry for some variables. We must consider that the athletes were analyzed at the beginning of the sportive season, without the training influence. To verify the prolonged effect hypothesis, the third experiment was conducted and it was observed that the sportive season did not affect all the variables related to the motor control and the greatest effects were observed during the bipedal tasks. In addition to that, the neuromuscular fatigue influenced the control of movement in the sedentary group, showing compensatory adjustments in some variables, especially in the maximal joint angles. However, we observed that the asymmetries did not change during different neuromuscular fatigue conditions. During the bipedal dynamic task it was observed asymmetries in all variables (joint angles, performance parameters and muscle activity). Interestingly, it was also observed the trend to higher activation of the contra-lateral lower limb during the fatigued limb. So, this study highlights the effect of the conditioning levels, the neuromuscular fatigue effect and the prolonged training to the motor control of the lower limbs in different tasks and conditions
12

Assimetrias posturais, demandas musculares e gasto energético em jovens e idosos na postura ereta / Postural asymmetry, muscular demands and energetic cost in young and elderly individuals during upright standing

Janina Manzieri Prado Rico 05 March 2015 (has links)
A permanência em pé por um determinado período de tempo exige que os indivíduos produzam periodicamente mudanças posturais, que podem favorecer a adoção de posturas mais assimétricas. Diante da deterioração do sistema de controle postural, é possível que idosos tenham uma dificuldade em permanecerem assimétricos em atividades do cotidiano. Em adição, variações no padrão de ativação muscular podem aumentar o gasto energético e levar os idosos a fadiga, o que resulta em sérias consequências como aumento no risco de quedas. Acredita-se que mudanças posturais durante a postura relaxada ocorram distintamente em adultos jovens e idosos, podem exigir esforços musculares variados e assim influenciar no gasto energético. O presente estudo investigou as assimetrias posturais, ativações musculares e gasto energético em adultos jovens e idosos saudáveis na postura ereta. Cinquenta e três jovens e 16 idosos permaneceram em diferentes posturas enquanto registrou-se as assimetrias na distribuição de peso ao longo do tempo (ADPm). Todos os idosos e 12 jovens submeteram-se ao registro eletromiográfico para análise dos padrões de ativação muscular de músculos da coxa e perna, e 7 indivíduos de cada grupo foram submetidos ao registro de gases para análise do gasto energético, consumo de oxigênio (VO2), quociente respiratório (R) e medida de frequência cardíaca. Os idosos apresentaram dificuldade na transferência de peso em posturas mais assimétricas e ambos os grupos apresentaram ligeira assimetria na postura ereta quieta (em torno de 5±4% de ADPm). Na postura relaxada a maior parte do tempo os indivíduos permaneceram em faixas de pequenas assimetrias, seguido de um tempo menor em posturas significativamente assimétricas. Em geral, as ativações musculares foram maiores em idosos, porém eles foram capazes de recrutar músculos de modo similar aos jovens. O aumento da atividade do músculo gastrocnêmio foi proporcional às posturas mais assimétricas em ambos os grupos. O gasto energético não sofreu grandes variações em condições de simetria ou assimetria posturais em jovens e idosos, porém parece que o aumento do gasto energético nos idosos está relacionado com o aumento da atividade muscular, o que poderia justificar a adoção de posturas menos assimétricas por parte desses indivíduos. Os resultados do presente estudo levantam a questão da possibilidade de haver maior gasto energético, principalmente em idosos, e abre novas possibilidades para que futuros estudos possam compreender a demanda metabólica envolvida na manutenção da postura ereta / To remain standing for a certain period of time we periodically produce postural changes, which may favouring the adoption of more asymmetric postures. In face of the postural control system deterioration, it is possible that older people find it difficult to adopt more asymmetrical postures during daily life activities. In addition, changes in muscle activation pattern may increase energy cost to stand in asymmetric posture, which would lead to muscle fatigue and as consequence increase in fall risk in this population. Thus, postural changes during relaxed postures and the muscular demand necessary to perform such changes may differ among young and older adults, resulting in different energy cost. The present study investigated body weight asymmetries, muscle activations and energy cost in healthy young and elderly adults during sanding tasks with different constrains. Fifty-three young and sixteen elderly subjects remained at different positions while we recorded the body weight asymmetry over time (ADPm). All the elderly participants and twelve young adults undergone to electromyographic record of the thigh and leg muscles, and 7 subjects in each group to gas record in order to quantify the energy cost, oxygen consumption (VO2) and respiratory quotient (R) and registered heart rate. During quiet standing task, both age groups showed a slight and similar WDA (mean values around 5%). However, the elderly had difficulty in maintaining more asymmetric postures - they were less asymmetrical than young in tasks that required great WDA. In the relaxed position, most of the time the subjects remained in small asymmetry ranges, followed by a shorter period in more asymmetric postures. In general, muscle activation level was higher in the elderly, but they were able to recruit muscle in a similar way to young subjects. In addition, gastrocnemius activity increased proportionally to body weight support in both age groups - it was greater in the supportive limb in the most asymmetric postures. Although in this study the energy cost was not significantly affected by the asymmetry in body weight distribution in young and old individuals, it seems that the increased energy cost in the elderly is associated with an increase in muscle activity, which might explain the adoption of less asymmetric postures by these individuals. The results of this study raise the question of the possibility of higher energy expenditure in more asymmetric postures, especially in the elderly, and opens new possibilities for future studies to understand the metabolic demands during upright standing
13

A Study of the Relationships Between Hemispheric Asymmetries and Intellectual Abilities

McShane, Anne 01 May 1987 (has links)
This study investigated the functional significance of cerebral asymmetries. Width measurements of the human brain were derived from computerized tomographic (CT) films and related to intellectual variables as determined by the Wechsler Adult Intelligence Scale Revised (WAIS-R). Subjects were adults of both sexes who had been referred for neurologic examination and were diagnosed as having no abnormalities (N=28). Reasons for referral included headache, dizziness, or to rule out central nervous system damage following various types of trauma. The asymmetry of hemispheric widths (left minus right) in the frontal, temporoparietal, and occipital areas was correlated with Verbal IQ minus Performance IQ scores within subjects. The difference between verbal and performance IQ scores was used because it reflected an IQ imbalance (IQ-I). Correlations obtained were -.30, -.26, and .06 (respectively). None of these correlations were significant by means of a two-tailed test. There were relationships between particular width asymmetries and individual subtest scores (p≤.05). The Verbal 1 (V1) subtest (Information) was correlated -.50, -.39 and -.47 with brain width asymmetries at 25%, 33% and 50% of the AP distance respectively. V1 correlated .39 with width asymmetry at 80%. Verbal 3 (Vocabulary), verbal 4 (Arithmetic) and verbal 5 (Comprehension) correlated .53 .38, and .39 with width asymmetry at 60% of the AP distance. Performance 1 (Picture Completion) correlated .46 with the width asymmetry at 20% of the AP length. In summary, there does appear to be some specific correlation between individual variation in brain asymmetry and cognitive processing. Relative size of the area of the brain that is involved in a key aspect of a particular cognitive processing may be a factor in the effectiveness of that processing. Further research appears warranted to confirm and clarify a possible relation between anatomical asymmetry and patterns of intellectual ability.
14

Perceptual Asymmetries in a Diatonic Context

Woloszyn, Michael Richard 07 1900 (has links)
When investigating the perceived similarity of two musical stimuli, systematic asymmetries emerge which depend on the nature of the two elements being compared, relative to the musical context in which they appear. At the level of individual tones, Krumhansl (1979) found that if the order of presentation was diatonic/nondiatonic (relative to a tonal context), similarity ratings were lower than if that order was reversed. She concluded that when a change results in an element becoming less stable in terms of it's position on the tonal hierarchy, similarity perception will be lower than if a change increases it's stability. At the level of melodies, Bartlett and Dowling ( 1988) obtained a similar result, but claimed the asymmetry was due to violations of scalar structure, having little or nothing to do with the tonal hierarchy. To test between these different accounts, a series of experiments was conducted in which pairs of diatonic melodies were presented for similarity ratings. Each melody consisted of a context sequence and a target sequence. The context sequences were designed to promote either a C-major or a D-minor tonal hierarchy. These respective keys share similar notes in their scales, but the tonal hierarchies are inverted with respect to one another. According to Krumhansl's account of the asymmetry, noticeable changes in one key context should not be noticeable in the other, due to the reversal in stability of the component tones of the alteration. According to Bartlett and Dowling, no differential sensitivity should be observed, since all changes were within the scale structure of both contexts. In the first experiment, repetition of the tonic was employed as the key-instantiating stimulus, the result being that strong asymmetrical perception arose, both on the measures of similarity ratings, as well as alteration detection ability. Subsequent experiments employed triadic contexts (suggested by Krumhansl and others to be strongly key-instantiating), and note-frequency controlling contexts (to rule out the possibility of note repetition playing a role in the similarity ratings). The results supported the hypothesis that asymmetric perception is a result of the dynamic tone quality differences between scale degrees in a tonal melody. Two subsequent control studies ruled out the possibility oftarget sequences themselves being responsible for the asymmetries, and confirmed that listeners perceived the melodies in the keys specified in the experiment. A model based loosely on Tversky's explanation of asymmetric perception was put forth to explain these data, as well as those of Bartlett and Dowling. / Thesis / Doctor of Philosophy (PhD)
15

Pressures and Flows for a Convergent and Divergent Oblique Glottis of 15 Degrees

Whitfield, Jason A. 04 April 2012 (has links)
No description available.
16

Detecção computacional de assimetrias entre mamogramas / Computational detection of asymmetries between mammograms

Ferrari, Ricardo José 01 April 2002 (has links)
Neste trabalho foram propostas técnicas para a segmentação automática de mamogramas e para a detecção de assimetrias entre mamogramas esquerdo e direito. A segmentação é realizada através de três técnicas computacionais para a identificação de três importantes regiões anatômicas nos mamogramas: borda da mama, músculo peitoral e disco fibro-glandular. O primeiro método focaliza a identificação da borda da mama através do uso de um modelo de contorno ativo especialmente projetado para esse propósito. Neste estágio, a borda da mama é automaticamente demarcada, todos os artefatos fora dessa região são eliminados, e a região de interesse usada para a detecção do músculo peitoral é definida. No próximo estágio, a borda do músculo peitoral é determinada usando uma técnica multiresolução baseada na representação Gabor wavelets. Finalmente, um modelo de densidades da mama, baseado no modelo da mistura finita de Gaussianas, é proposto para a representação de quatro categorias de tecidos mamários com diferentes densidades. O disco fibro-glandular é identificado através da aplicação de um limiar sob as classes de densidades determinadas no modelo. Os métodos propostos foram aplicados em 84 imagens de mamogramas de projeções médio-laterais oblíqüas da base de dados Mini-MIAS (\"Mammographic Image Analysis Society\", London, UK). A avaliação dos resultados dos procedimentos de segmentação da borda da mama e borda do músculo peitoral foi realizada com base no percentual de pixels falso-positivos (FPs) e falso-negativos (FNs) determinados por comparação entre os contornos verdadeiros e os contornos automaticamente identificados. As taxas médias de FPs e FNs para as bordas da mama e do músculo peitoral foram, respectivamente, de 0,41% e 0,58%, e 1,78% e 5,77%. A segmentação dos discos fibro-glandulares foi subjetivamente classificada por radiologistas e os resultados indicaram que em mais de 80% dos casos a segmentação foi ) considerada aceitável para o uso em sistemas de auxílio ao diagnóstico. A detecção de assimetrias foi realizada usando informações direcionais, obtidas a partir da representação multiresolução Gabor wavelets, e de informações de forma e densidade, extraídas dos discos fibro-glandulares dos mamogramas esquerdo e direito. No procedimento de análise direcional, uma representação wavelet formada por filtros de Gabor bidimensionais com variação em freqüência e orientação, especialmente projetadas para reduzir a redundância na representação, é aplicada para uma dada imagem. As respostas dos filtros para diferentes escalas e orientações são analisadas através da transformada de Karhunen-Loève (KL) e pelo método de limiarização de Otsu. A transformada KL é aplicada para selecionar os componentes principais das respostas dos filtros, preservando apenas os elementos direcionais mais relevantes que aparecem em todas as escalas. Os componentes principais selecionados e limiarizados pela técnica de Otsu são usados para obter as imagens de magnitude e fase dos componentes direcionais da imagem. Medidas estatísticas extraídas dos diagramas de rosa calculados a partir das imagens de fase são usadas para a análise quantitativa e qualitativa dos padrões orientados. Um total de 11 atributos é extraído dos discos fibro-glandulares segmentados dos mamogramas esquerdo e direito, e a diferença calculada para cada par de atributos é usada como uma medida para a detecção de assimetrias. Um total de 88 imagens (22 casos normais, 14 casos de densidades assimétricas e 8 casos de distorções de arquitetura) da base de dados Mini-MIAS foram usadas para avaliar o método proposto. A combinação exaustiva dos atributos juntamente com a análise de componentes principais foi usada para selecionar o melhor subgrupo de atributos. A classificação foi realizada através de classificadores de Bayes (linear e quadrático) ) e usando o método \"leave-one-out\". Uma taxa de classificação correta de 84,44% foi alcançada. / In this work, techniques are proposed for the automatic segmentation of mammograms and detection of asymmetries between left and right mammograms. The segmentation is performed by using three computational techniques for the identification of three important anatomical regions of mammograms: the skin-air boundary, the pectoral muscle, and the fibro-glandular disc. The first method focuses on the identification of the skin-air boundary by using an active contour model algorithm specially tailored for this purpose. In this stage, the skin-air boundary is demarcated, all artefacts outside the breast region are eliminated, and the region of interest for detection of the pectoral muscle is defined. In the next stage, the edge of the pectoral muscle is determined by using a multiresolution technique based upon a Gabor wavelets representation. Finally, a density breast model based upon a Gaussian mixture model is proposed for the representation of four categories of different density tissues in the breast. The fibro-glandular disc is identified by thresholding the density categories of the model. The methods proposed were applied to 84 images of medio-lateral oblique mammograms from the Mini-MIAS (Mammographic Image Analysis Society, London, U.K.) database. The evaluation of the skin-air boundary and the pectoral muscle edge were performed based upon the percentage of false-positive (FP) and false-negative (FN) pixels determined by comparison between the true contours and the contours automatically identified. The FP and FN average rates for the skin-air boundary and the pectoral muscle edge were, respectively, 0.41% and 0.58%, and 1.78% and 5.77%. Two radiologists subjectively rated the segmentation of the fibro-glandular disc and the results indicate that in more than 80% of the cases, the segmentation was considered acceptable for a Computer Aided Diagnosis purposes. Detection of asymmetries (continua) (continuação) is performed by using directional information, obtained from a multiresolution Gabor wavelets representation, and shape and density information, extracted from the fibro-glandular discs of left and right mammograms. In the directional procedure, a particular wavelet scheme with 2-D Gabor filters as elementary functions with varying tuning frequency and orientation, specifically designed in order to reduce the redundancy in the wavelet-based representation, is applied to the given image. The filter responses for different scales and orientation are analyzed by using the Karhunen-Loève (KL) transform and Otsu\'s method of thresholding. The KL transform is applied to select the principal components of the filter responses, preserving only the most relevant directional elements appearing at all scales. The selected principal components are thresholded by using Otsu\'s method and used to obtain the magnitude and phase of the image directional components. Rose diagrams computed from the phase images and statistical measures computed thereof are used for quantitative and qualitative analysis of the oriented patterns. A total of 11 features are also extracted from the segmented fibro-glandular discs of left-right mammograms, and the difference of each feature pair is used as a measure for detecting asymmetries. A total of 88 images from 22 normal cases, 14 asymmetric cases, and 8 architectural distortion cases from the Mini-MIAS database were used to evaluate the scheme. An exhaustive combination of the features along with the principal components analysis was used to select the best feature set. The classification was performed by using two Bayes\' classifiers (linear and quadratic) and the leave-one-out methodology. Average classification accuracy up to 84.44% was achieved.
17

Impacto de crises sobre investimentos e financiamentos de empresas brasileiras: abordagem no contexto de restrições financeiras / Impact of crisis on investments and financing of brazilian companies: approach in the context of financial constraints

Franzotti, Tatiane Del Arco 31 August 2018 (has links)
Em momentos de crises financeiras, problemas decorrentes de assimetrias informacionais são intensificados, prejudicando a canalização de recursos para detentores das melhores oportunidades de investimento, conforme Mishkin (1992). Nesse sentido, crises tendem a intensificar restrições financeiras, podendo impactar investimentos e financiamentos das empresas de formas distintas. Dito isso, este estudo tem por objetivo investigar os impactos de crises financeiras sobre investimentos e financiamentos de empresas brasileiras restritas e não restritas, analisando, especificamente, o impacto da crise do subprime de 2008 e da recente crise de 2015. As empresas foram classificadas em restritas e não restritas segundo dois critérios: interseção entre tamanho e idade e existência ou não de rating, contando com 203 empresas de capital aberto no modelo de investimentos e 192 empresas no modelo de financiamentos. Foram utilizados dados trimestrais entre o primeiro trimestre de 2007 e o terceiro trimestre de 2016, adotando como método a análise de dados em painel. Os resultados indicam que, tanto pelo critério tamanho e idade quanto pelo critério de rating, somente a crise de 2015 impactou, negativamente, os investimentos das empresas, sendo esse impacto maior sobre empresas restritas. Analisando a sensibilidade dos investimentos ao caixa em momentos de contração na oferta de recursos, há indícios de que, pelo critério tamanho e idade, caixa foi mais relevante para as empresas restritas nas crises de 2008 e 2015 em comparação às empresas não restritas, enquanto, pelo critério de rating, somente na crise de 2015. O impacto de crises sobre a alavancagem foi mais evidente pelo critério de rating, em que a crise de 2008 mostrou impacto maior, negativamente, sobre a alavancagem de empresas restritas, acompanhado de um aumento na proporção das dívidas de curto prazo principalmente para essas empresas. A crise de 2015 não impactou de forma diferente a alavancagem e a maturidade das dívidas de empresas restritas e não restritas. Em suma, há indícios de impactos maiores de crises sobre investimentos e financiamentos de empresas restritas em comparação a empresas não restritas, sendo que a crise de 2008 apresentou impactos mais relevantes sobre a alavancagem e a crise de 2015 apresentou impactos mais relevantes sobre investimentos. / In times of financial crisis, problems stemming from informational asymmetries are intensified, hampering the channeling of resources to those with the best investment opportunities, according to Mishkin (1992). In this sense, crisis tend to intensify financial constraints, and may impact companies\' investments and financing differently. That said, this study aims to investigate the impact of financial crisis on investments and financing of financially constrained and unconstrained Brazilian companies, specifically analyzing the impact of subprime crisis of 2008 and the recent crisis of 2015. Companies were classified as constrained and unconstrained according to two criteria: intersection between size and age and existence or not of rating, counting with 203 public companies in the investment model and 192 companies in the financing model. Quarterly data were used between the first quarter of 2007 and the third quarter of 2016, adopting the method of panel data analysis. The results indicate that, by both the size and age criteria and the rating criterion, only the crisis of 2015 negatively impacted the investments of the companies, being the impact greater on constrained companies. Analyzing the sensitivity of the investments to the cash in times of contraction in the supply of resources, there are indications that, by the criterion of size and age, cash was more relevant for constrained companies in the crisis of 2008 and 2015 compared to unconstrained companies, and by the criterion of rating, only in the crisis of 2015. The impact of crisis on leverage was more evident by the rating criterion, in which the crisis of 2008 showed a larger negative impact on the leverage of constrained companies, accompanied by an increase in proportion of short-term debt mainly to these companies. The crisis of 2015 did not have a different impact on the leverage and maturity of the debts of constrained and unconstrained companies. In summary, there are indications of greater impacts of crisis on investments and financing of constrained companies compared to unconstrained companies, and the crisis of 2008 had more relevant impacts on leverage and the crisis of 2015 had more relevant impacts on investments.
18

Dynamical Impacts of Rotating Convective Asymmetries on Tropical Cyclones

Moon, Yumin 01 January 2008 (has links)
Although a tropical cyclone may conceptually be regarded as an axisymmetric vortex, there is substantial evidence that asymmetric dynamics play an important role. In this thesis, dynamical impacts of rotating convective asymmetries are examined in this thesis. Two types of rotating convective asymmetries are considered: rotating eyewall convective maximum which is located in the core region of the storm and spiral bands which are located outside the core. Both of them can be characterized as rotating asymmetric convective heat sources, and they are superimposed on a balanced, axisymmetric vortex to approximate the effect of rotating eyewall convective maximum and spiral bands on tropical cyclone by using a simple nonhydrostatic three-dimensional, but linear model that is based on vortex anelastic equations. The evolution of rotating convective asymmetric heat sources on a balanced, axisymmetric vortex, which is modeled after tropical cyclones, is investigated to examine angular momentum transport by gravity waves that radiate away from the core region. Results show that gravity waves can transport angular momentum away from a tropical cyclone, but a very small amount, which is several orders of magnitude smaller than the estimate by recent studies. The significantly large difference may largely be due to the difference between two-dimensional and three-dimensional adjustment processes. Assuming that the effects of spiral bands on tropical cyclone wind field are caused by the response to diabatic heating in their convection, rotating asymmetric heat sources are constructed to reflect observations of spiral bands. These heat sources are rotated around a realistic but idealized balanced axisymmetric vortex. Simulation results show that the response of tropical cyclone wind field to idealized spiral band heat sources can successfully capture a number of observed well-known features of spiral band circulation, such as overturning secondary circulation, descending mid-level inflow, and cyclonic tangential acceleration. Comparison to full-physics numerical simulations confirms the validity of this method which provides a simple dynamical framework to better understand the impact of spiral bands in tropical cyclone.
19

Interdisciplinary studies on information structure : ISIS ; Working papers of the SFB 632. - Vol. 10

January 2008 (has links)
The 10th volume of the working paper series contains two papers contributed by SFB-members. The first paper “Single prosodic phrase sentences” by Caroline Féry (A1) and Heiner Drenhaus (C6, University of Potsdam) investigates the prosody of Wide Focus Partial Fronting in a series of production and perception experiments. The second paper “Focus Asymmetries in Bura” by Katharina Hartmann, Peggy Jacob (B2, Humboldt University Berlin) and Malte Zimmermann (A5, University of Potsdam) explores the strategies of marking focus in Bura (Chadic).
20

Focus asymmetries in Bura

Hartmann, Katharina, Jacob, Peggy, Zimmermann, Malte January 2008 (has links)
(Chadic), which exhibits a number of asymmetries: Grammatical focus marking is obligatory only with focused subjects, where focus is marked by the particle án following the subject. Focused subjects remain in situ and the complement of án is a regular VP. With nonsubject foci, án appears in a cleft-structure between the fronted focus constituent and a relative clause. We present a semantically unified analysis of focus marking in Bura that treats the particle as a focusmarking copula in T that takes a property-denoting expression (the background) and an individual-denoting expression (the focus) as arguments. The article also investigates the realization of predicate and polarity focus, which are almost never marked. The upshot of the discussion is that Bura shares many characteristic traits of focus marking with other Chadic languages, but it crucially differs in exhibiting a structural difference in the marking of focus on subjects and non-subject constituents.

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