Endozytose erfordert hohe Membrankrümmung und führt zu Flächenänderungen der Membranhälften. Dies kann durch eine Oberflächendifferenz zwischen den Schichten initiiert werden, die durch geänderte Lipidzusammensetzungen hervorgerufen werden kann. Daher wurde die Hypothese aufgestellt, dass Lipid-Transporter zu Beginn der Endozytose für veränderte Flächenverhältnisse verantwortlich sind. Um den Einfluss veränderter Flächen auf Endozytose zu untersuchen, wurden die Oberflächenverhältnisse der Membran durch Zugabe von Phospholipiden verändert und anschließend Endozytose gemessen. Abhängig von der Sorte wurden die Lipide nur in die äußere Schicht eingebaut oder auch auf die innere Seite transportiert, wodurch die entsprechende Seite vergrößert wurde. Die Zugabe verschiedener Aminophospholipide, die auf die innere Membranseite transportiert werden, führte zu gesteigerter „bulk flow“ Endocytose in K562-Zellen. Darüber hinaus deuten die Ergebnisse darauf hin, dass Clathrin-vermittelte Endozytose von Hep2-Zellen ebenfalls stimuliert wurde. Umgekehrt hatte die Zugabe von Lipiden, die auf der äußeren Hälfte bleiben, reduzierte „bulk flow“- oder Clathrin-vermittelte Endozytose in verschiedenen Zelllinien zur Folge. Bemerkenswert ist, dass auch Clathrin-vermittelte Endozytose durch die Lipidzugabe beeinflusst wurde, obwohl gerade in diesem Weg viele Proteine involviert sind, die Krümmung induzieren können. Dies passt zu einem neuen Modell wie Lipidtransporter in Endozytose involviert sind. Durch den Transport von Lipiden und die zusätzliche Interaktion mit Endozytoseproteinen, könnten diese Transporter zwei Mechanismen zur Erzeugung von Krümmung miteinander verbinden: Membrankrümmung induziert durch eine Flächenasymmetrie zwischen den Membranhälften und durch Wechselwirkung mit Proteinen. Die Ergebnisse dieser Arbeit deuten darauf hin, dass die für Endozytose notwendige Krümmung durch die durch Lipidtransport induzierte Flächenasymmetrie der Membranschichten unterstützt wird. / Endocytic engulfment requires high local membrane curvature and causes significant area changes of the membrane leaflets. This can be initiated by differences between the surface areas of the two monolayers related to leaflet specific modulation of lipid composition. Thus, it was proposed that lipid translocators, pumping phospholipids from the outer to the inner leaflet, account for monolayer area asymmetry as an early step in endocytosis. To elucidate the influence of this asymmetry on endocytosis, surface area relation was altered by adding exogenous phospholipids to living cells and changes in endocytic activity were quantified. Depending on the lipid species, exogenous lipids were only incorporated into the outer layer or subsequently translocated across the plasma membrane thereby increasing either the outer or inner surface area. Addition of different analogues of aminophospholipids, which are translocated to the inner leaflet, led to an enhancement of bulk flow endocytosis in K562 cells. Moreover, our data indicate that clathrin-mediated endocytosis of Hep2 cells was stimulated as well. Inversely, addition of phospholipids, which remain on the outer layer, reduced bulk flow or clathrin-mediated endocytosis in various cell lines. Notably, also clathrin-mediated endocytosis was influenced by the addition of lipids, although many proteins noted for their ability to induce membrane curvature are known to be implicated in this pathway. This corroborates a recent model how aminophospholipid translocases are implicated in endocytosis. Upon translocating lipids and additionally interacting with endocytic accessory proteins, lipid translocators could integrate two processes to generate curvature: membrane bending based on monolayer area asymmetry and protein-related mechanisms. Collectively, findings in the present study suggest that curvature generation in endocytosis is supported by the induction of monolayer area asymmetry mediated by the translocation of lipids.

Dans cette thèse, nous nous intéressons à l'étude des courbes discrètes et ses applications en analyse d'images. Nous avons proposé une amélioration de l'estimation de courbure reposant sur le cercle circonscrit. Celle-ci repose sur la notion de segment flou maximal d'épaisseur [nu] et sur la décomposition d'une courbe discrète en sa séquence de segments flous maximaux. Par la suite, nousavons appliqué cette idée en 3D afin d'estimer la courbure et la torsion discrète en chaque point d'une courbe 3D. Au niveau de l'application, nous avons développé une méthode rapide et fiable pour détecter les points dominants dans une courbe 2D. Un point dominant est un point dont la courbure est localement maximale. Les points dominants jouent un rôle très important dans la reconnaissance de formes. Notre méthode utilise un paramètre qui est l'épaisseur des segments flous maximaux. Reposant sur cette nouvelle méthode de détection des points dominants, nous avons développé des méthodes sans paramètres de détection des points dominants. Celles-ci se basent sur une approche multi-épaisseur. D'autre part, nous nous intéressons particulièrement au cercles et arcs discrets. Une méthode linéaire a été développé pour reconnaître des cercles et arcs discrets. Puisnous avons fait évoluer cette méthode afin de travailler avec des courbes bruitées en utilisant une méthode de détection du bruit. Nous proposons aussi une mesure de circularité. Une méthode linéaire qui utilise cette mesure a été aussi développée pour mesurer la circularité des courbes fermées. Par ailleurs, nous avons proposé une méthode rapide pour décomposer des courbes discrètes en arcs et en segments de droite. / In this thesis, we are interested in the study of discrete curves and its applications in image analysis. We have proposed an amelioration of curvature estimation based on circumcircle. This method is based on the notion of blurred segment of width [nu] and on the decomposition of a curve into the sequence of maximal blurred segment of width [nu]. Afterwards, we have applied this idea in 3D to estimate the discrete curvature and torsion at each point of a 3D curve. Concerning the applications, we have developed a rapid et reliable method to detect dominant points of a 2D curve. A dominant point is a point whose the curvature value is locally maximum. The dominant points play an important role in pattern recognition. Our method uses a parameter: the width of maximal blurred segments. Based on this novel method of dominant point detection, we proposed free-parameter methods for polygonal representation. They are based on a multi-width approach. Otherwise, we are interested in discrete arcs and circles. A linear method has been proposed for the recognition of arcs and circles. We then develop a new method for segmentation of noisy curves into arcs based on a method of noise detection. We also proposed a linear method to measure the circularity of closed curves. In addition, we have proposed a robust method to decompose a curve into arcs and line segments

Neisseria meningitidis est une bactérie diderme qui colonise le nasopharynx humain de façon commensale. Occasionnellement, elle franchit la barrière nasopharyngée et accède à la circulation sanguine où elle peut provoquer un choc septique et/ou une méningite Le pouvoir pathogène de N. meningitidis est lié à sa capacité à interagir avec les cellules endothéliales humaines. Après avoir adhéré aux cellules grâce à des organelles filamenteux, les pili de type IV, les bactéries induisent une déformation de la membrane plasmique de la cellule hôte sous la forme de protrusions riches en actine ressemblant à des filopodes. Ces protrusions permettent aux bactéries de résister aux forces de cisaillements générées par le flux sanguin et de proliférer à la surface des cellules. Contrairement à de nombreuses autres bactéries pathogènes, cette déformation de la membrane plasmique ne nécessite pas de polymérisation d’actine. Cependant, les mécanismes cellulaires et moléculaires de cette déformation sont inconnus. Dans cette étude, nous montrons que lorsque des bactéries individuelles adhèrent à la cellule hôte, la membrane plasmique se déforme en adhérant le long des fibres de pili de type IV de façon similaire au mouillage d’un liquide sur un solide. Les pili de type IV agissent donc comme un échafaudage extracellulaire qui guide les protrusions de membrane plasmique indépendamment du cytosquelette d’actine. Nous montrons également que la capacité de la membrane plasmique à se déformer le long de structures adhésives nanométriques est une propriété intrinsèque des cellules endothéliales. Ces travaux décrivent le mécanisme d’une étape importante de la pathophysiologie de N. meningitidis et mettent en évidence des propriétés nouvelles de la membrane plasmique des cellules humaines qui pourraient être impliquées dans d’autres processus fondamentaux de biologie cellulaire. / Neisseria meningitidis is a diderm bacterium that is naturally found in the human nasopharynx as a commensal. Occasionally, it can cross the mucosa and reach the underlying blood vessels where it enters the circulation. Once in the bloodstream, it can cause severe septic shock and/or meningitis. The ability of N. meningitidis to cause disease is tightly linked to its ability to interact with human endothelial cells. In particular, upon bacterial adhesion via filamentous organelles called type IV pili, bacteria remodel the host cell plasma membrane in the form of actin-rich, filopodia-like protrusions. These protrusions allow bacteria to resist blood flow-generated shear stress and proliferate on top of the host cells. Unlike many other bacterial pathogens, plasma membrane remodeling induced by N. meningitidis does not require actin polymerization. Yet, the cellular and molecular mechanisms of this process are unknown. Here, we show that upon adhesion of individual bacteria, the host cell plasma membrane deforms by adhering along type IV pili fibers in a wetting-like fashion. Therefore, type IV pili act as an extracellular scaffold that guide plasma membrane protrusions in an F-actin-independent manner. We further show that the ability of the plasma membrane to deform along nanoscale adhesive structures is an intrinsic property of endothelial cells. Therefore, this study uncovers the mechanism of a key step of N. meningitidis pathophysiology and reveals novel properties of human cell plasma membrane that could be at play in other fundamental cellular processes.

A second-order Lagrangian system is a generalization of a classical mechanical system for which the Lagrangian action depends on the second derivative of the state variable. Recent work has shown that the dynamics of such systems c:an be substantially richer than for classical Lagrangian systems. In particular, topological properties of the planar curves obtained by projection onto the lower-order derivatives play a key role in forcing certain types of dynamics. However, the application of these techniques requires an analytic restriction on the Lagrangian that it satisfy a twist property. In this dissertation we approach this problem from the point of view of curve shortening in an effort to remove the twist condition. In classical curve shortening a family of curves evolves with a velocity which is normal to the curve and proportional to its curvature. The evolution of curves with decreasing action is more general, and in the first part of this dissertation we develop some results for curve shortening flows which shorten lengths with respect to a Finsler metric rather than a Riemannian metric. The second part of this dissertation focuses on analytic methods to accommodate the fact that the Finsler metric for second-order Lagrangian system has singularities. We prove the existence of simple periodic solutions for a general class of systems without requiring the twist condition. Further; our results provide a frame work in which to try to further extend the topological forcing theorems to systems without the twist condition. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Orientador: Glaucia Amorim Faria / Resumo: O eucalipto é difundido em várias regiões brasileiras e no mundo. Os Estados brasileiros com maiores áreas de plantio do eucalipto são Minas Gerais, Mato Grosso do Sul, São Paulo e Paraná. Com crescente contribuição ao longo dos anos, o seu cultivo tem gerado empregos tanto na área rural quanto na área urbana. O que torna de suma importância maiores pesquisas que visem a melhoria das áreas de plantio, maiores informações para condução e melhoria de produção, o que acarretará em maiores ofertas para o mercado nacional. Neste cenário, estudos que auxiliem o pesquisador a conhecer a variabilidade desta cultura, definir o tamanho ideal de parcela e as curvas de crescimento que melhor representem o conjunto de dados ao longo do tempo, serão essenciais para que se faça a inferência correta, se tenha maior precisão e maximização das informações, garantindo maior eficiência do procedimento experimental, como redução do tempo de espera, permitindo ao pesquisador a comparação do comportamento da planta e seus componentes mais relevantes. Para tanto, o trabalho tem por objetivo: a recomendação de uma tabela de classificação de variação (utilizando os métodos de Garcia, Pimentel-Gomes e Costa, Seraphin e Zimmermann); o tamanho ótimo de parcelas (utilizando o método da máxima curvatura modificada) em experimentos em casa de vegetação; o modelo não-linear (Logístico, Gompertz e Von Bertalanffy) que melhor se adeque ao padrão de crescimento ao longo do tempo, em experimentos com a cultura d... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Eucalyptus is widespread in several Brazilian regions and in the world. The Brazilian states with the largest eucalyptus plantation areas are Minas Gerais, Mato Grosso do Sul, São Paulo, and Paraná. With growing contribution over the years, its cultivation has generated jobs in both rural and urban areas. This makes more important research to improve the planting areas, greater information for conducting and improving production, which will lead to greater offers for the domestic market. In this scenario, studies that help the researcher to know the variability of this crop, to define the ideal plot size and the growth curves that best represent the data set over time, will be essential for correct inference, if greater accuracy and maximization of information, guaranteeing greater efficiency of the experimental procedure, such as reduction of waiting time, allowing the researcher to compare the behavior of the plant and its most relevant components. To do so, the objective of the study is: to recommend a variation classification table (using the methods of Garcia, Pimentel-Gomes and Costa, Seraphin and Zimmermann); the optimal size of plots (using the modified maximum curvature method) in greenhouse experiments; the non-linear model (Logistic, Gompertz and Von Bertalanffy) that best fit the pattern of growth over time, in experiments with the Eucalyptus crop. / Mestre

Os modelos de Toda admitem uma representação de suas equações de movimento em termos da curvatura nula, isto é, existem potenciais que são funcionais dos campos da teoria e pertencem a uma álgebra de Kac-Moody tal que a condição de curvatura nula seja equivalente às equações de movimento. Para a construção das soluções solitônicas e cargas conservadas são necessários a gradação inteira da álgebra de Kac-Moody e a existência de soluções de vácuo, de forma que os potenciais assumam valores em uma subálgebra abeliana quando calculados nestas soluções de vácuo. A gradação da álgebra é de extrema importância pois garante que o potencial transformado tenha a mesma estrutura que o potencial de vácuo. As cargas conservadas são então construídas partindo de soluções da órbita do vácuo por meio de transformações de dressing, que consistem na aplicação da decomposição de Gauss para a produção de um potencial transformado a partir de duas transformações de Gauge. Nesta dissertação calculamos as infinitas cargas conservadas dos modelos de Toda sl(3) e também sl(N), avaliadas nas soluções pertencentes à órbita do vácuo sob transformações de dressing. As soluções de interesse físico, como sólitons e breathers pertencem a esta órbita, e as cargas conservadas para tais soluções são escritas como uma soma sobre os sólitons. Mostramos que a energia e o momento proveem de termos de superfície. / The Toda models admit a zero curvature representation of their equations of motion, i.e. there exist potentials, (A), wich are functionals of the fields of the theory and which belong to a Kac-Moody algebra G such that the zero curvature condition is equivalent to the equations of motion. For the construction of the solitons solutions and conserved charges is required an integer gradation of the Kac-Moody algebra and a ``vacuum solution\'\', such that the potentials evaluated on it belong to an abelian subalgebra. The gradation of the algebra is of extreme importance since it guarantees that the transformed potential have the same structure as the vacuum potential. The conserved charges are then constructed using the dressing method, that through the Gauss decomposition, leads to the transformed potentials by two gauge transformations. In this dissertation we calculate the infinite conserved charges of models Toda sl (3) and also sl (N) evaluated on the solutions belonging to the orbit of the vacuum under dressing transformations. The solutions of physical interest, like solitons and breathers belong to this orbit and the conserved charges for such solutions are written as a sum over the number the solitons. We show that the energy and momentum are boundary terms.

Orientador: Luzia Aparecida Trinca / Resumo: A classe dos modelos de regressão incorporando polinômios fracionários - FPs (Fractional Polynomials), proposta por Royston & Altman (1994), tem sido amplamente estudada. O uso de FPs em modelos mistos constitui uma alternativa muito atrativa para explicar a dependência das medidas intra-unidades amostrais em modelos em que há não linearidade na relação entre a variável resposta e variáveis regressoras contínua. Tal característica ocorre devido aos FPs oferecerem, para a resposta média, uma variedade de formas funcionais não lineares para as variáveis regressoras contínuas, em que se destacam a família dos polinômios convencionais e algumas curvas assimétricas e com assíntotas. A incorporação dos FPs na estrutura dos modelos mistos tem sido investigada por diversos autores. Porém, não existem publicações sobre: a exploração da problemática da modelagem na parte fixa e na parte aleatória (principalmente na presença de várias variáveis regressoras contínuas e categóricas); o estudo da influência dos FPs na estrutura dos efeitos aleatórios; a investigação de uma adequada estrutura para a matriz de covariâncias do erro; ou, um ponto de fundamental importância para colaborar com a seleção do modelo, a realização da análise de diagnóstico dos modelos ajustados. Uma contribuição, do nosso ponto de vista, de grande relevância é a investigação e oferecimento de estratégias de ajuste dos modelos polinômios fracionários com efeitos mistos englobando os pontos citados acima com o objetiv... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The class of regression models incorporating Fractional Polynomials (FPs), proposed by Royston & Altman (1994), has been extensively studied. The use of FPs in mixed models is a very attractive alternative to explain the within-subjects’ measurements dependence in models where there is non-linearity in the relationship between the response variable and continuous covariates. This characteristic occurs because the FPs offers a variety of non-linear functional forms for the continuous covariates in the average response, in which the family of the conventional polynomials and some asymmetric curves with asymptotes stand out. The incorporation of FPs into the structure of the mixed models has been investigated by several authors. However, there are no works about the following issues: the modeling of the fixed and random effects (mainly in the presence of several continuous and categorical covariates), the study of the influence of the FPs on the structure of the random effects, the investigation of an adequate structure for the covariance of the random errors, or, a point that has central importance to the selection of the model, to perform a diagnostic analysis of the fitted models. In our point of view, a contribution of great relevance is the investigation and the proposition of strategies for fitting FPs with mixed effects encompassing the points mentioned above, with the goals of filling these gaps and to awaken the users to the great potential of mixed models, now even mor... (Complete abstract click electronic access below) / Doutor

Orientador: Sueli Irene Rodrigues Costa / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-09-11T21:20:45Z (GMT). No. of bitstreams: 1 Bressan_JoaoPaulo_D.pdf: 1164660 bytes, checksum: 4825edafe6fbea5e3bc43934bc528376 (MD5) Previous issue date: 2012 / Resumo: A partir das desigualdades de Hamming e Gilbert-Varshamov obtém-se um limitante superior e um limitante inferior para o número de pontos de um código numa variedade flag geométrica. Isto é feito tomando-se uma estimativa para o volume de bolas geodésicas, que resulta de cálculos envolvendo a curvatura seccional destas variedades. Em particular, são derivados limitantes para empacotamentos de esferas numa variedade de Grassmann complexa. Um limitante superior para a distância mínima também é obtido através da inversa da função que calcula o volume de um chapéu esférico. Esta técnica geométrica também é aplicada no estudo de limitantes para empacotamentos em alguns casos particulares de variedades flag maximais. Através de procedimentos computacionais, tais limitantes são implementados numericamente em alguns exemplos. Uma motivação para este trabalho foi à busca de possíveis extensões de alguns resultados sobre as grassmanianas complexas, cujo interesse na área de comunicações vem de uma interpretação que pode ser feita da transmissão em canais MIMO não coerentes via códigos em tais variedades / Abstract: Upper and lower bounds for the number of points of codes in geometric flag manifolds are obtained from Hamming and Gilbert-Varshamov inequalities. This is done by taking an estimate for the volume of geodesic balls, as a result of calculations involving the sectional curvature of such manifolds. As a particular case, sphere packing bounds in complex Grassmann manifolds are derived. An upper bound on the minimum distance is also obtained through the inverse mapping for the volume of spherical caps. This geometric technique is also applied in the study of sphere packing bounds in some particular cases of full-flag manifolds. Such bounds are numerically implemented in some examples. One motivation for this work was the search for possible extensions of some results on complex Grassmann manifolds, which interest in communications comes from a model for the transmition on non-coherent MIMO channels via codes in such manifolds / Doutorado / Matematica Aplicada / Doutor em Matemática Aplicada

Made available in DSpace on 2015-04-22T22:16:06Z (GMT). No. of bitstreams: 1 Geziel Damasceno.pdf: 743020 bytes, checksum: 0001ac62bcb357c87e266dd4d0de7a3b (MD5) Previous issue date: 2012-12-31 / FAPEAM - Fundação de Amparo à Pesquisa do Estado do Amazonas / Admits that in a complete surface, connected and oriented immersed in R3 with non-zero constant mean curvature, there is a geodesic triangle whose interior angles satisfy a relationship involving the integral mean curvature and the angle formed by unit vector parallel to a coordinate axis of either R3 and the unit vector normal to the surface, and in such cases shows that the immersion is a surface of revolution, ie, a surface Delaunay. Then give a characterization of the sphere is changing some hypotheses on the previous result. / Admite-se que, numa superfície completa, conexa e orientada imersa no espaço euclidiano tri-dimensional com curvatura média constante não nula, existe um triângulo geodésico cujos ângulos internos satisfazem uma relação integral envolvendo a curvatura média e o ângulo formado pelo vetor unitário paralelo a um eixo coordenado qualquer do espaço ambiente e o vetor unitário normal a superfície, e sob tais hipóteses mostra-se que a imersão é uma superfície de revolução, ou seja, uma superfície de Delaunay. Em seguida darse uma caracterização da esfera alterando-se algumas hipóteses no resultado anterior.

Thin films and multilayers are widely used in many applications, ranging from X-ray optics to microelectronic devices. In service, the X-ray optics elements are exposed to the X-ray beam, which heats up the structure resulting in the thermal deformations, and consequently in distortions of the reflective surface. In addition, the excessive heating may activate interdiffusion in the multilayers coatings and result in degradation of their reflective performance and even film cracking. Therefore, analysis of the thermally-induced deformations and stresses in the X-ray optical elements is important. The presented work is organized in two major parts. The first part examines formation of the peculiar periodic crack patterns observed in the thermally loaded Mo/Si multilayers. Film stress evolution during thermal cycling of the multilayers on Si substrate is analyzed. Results of the high-speed microscopic observations of crack propagation in the annealed Mo/Si multilayers are presented. The observations provide experimental evidence of the mechanism underlying formation of the periodic crack patterns. In the second part, thermal deformations and the resulting surface curvature changes in the X-ray optics elements are analyzed. Finite element modeling is used to assess the potential to thermally control curvature in the X-ray mirrors consisting of the Mo/Si multilayers on a Si substrate. Influence of heating due to the X-ray beam irradiation on thermal deformations in the X-ray mirror bonded to a thick substrate is analyzed in-depth. The detailed consideration includes analysis of the thermal and structural mechanics simulations. Based on simulations of different model configurations, influence of structural composition on thermal distortions of the optics elements is addressed. Results of this analysis can be used to mitigate distortions of the X-ray optics caused by the X-ray beam and provide basis for further studies of thermally controlling surface curvature in the optical elements.