Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 114-119).

Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 427-438).

Thesis (M.A.)--University of Wisconsin--Madison. / Typescript. Includes bibliographical references (leaves 170-177).

Thesis (M.A.)--Zhong guo wen hua xue yuan. / Reproduced from typescript. Bibliography: p. 163-168.

Thesis (M.A.)--Guo li Taiwan da xue. / Cover title. Reproduced from typescript. Bibliography: leaves 68-72.

Diss.--Hamburg--Universität, 1990.

No description available.

Bacterial cell division requires formation of the cytokinetic cell division septum at the mid-cell position, a process that is determined by three Min proteins; MinC, MinD and MinE. Regulation of cell division by Min proteins occurs via a multi-step process involving interactions between various Min proteins, as well as the membrane. In this cycle, ATP-bound MinD binds to the membrane surface where it can recruit MinC to inhibit formation of the cell division septum. MinE binding to this complex displaces MinC and stimulates ATP hydrolysis, leading to the dissociation of MinD from the membrane. These interactions give rise to a dynamic pattern of Min protein localization that appears to involve a polymeric state that is designed to create a zone that is permissive to cell division at the mid-point of the cell. The interaction between MinD and the membrane is a critical aspect of this cycle, yet the role of the lipid bilayer in MinD activation, localization and polymerization is not well understood. To probe the role of membrane charge and fluidity on MinD activation and polymerization, we developed a kinetic assay of MinE-stimulated MinD ATPase activity. We found that membrane charge is essential for MinD activation and that differences in membrane fluidity give rise to changes in its activity. Moreover, a burst phase was also observed during the first few minutes of reaction, but only on the most fluid anionic lipid tested. To help determine if the observed membrane-dependent changes in MinD activity are linked to any changes in MinD polymer structure, we have begun to develop a method to identify surface exposed regions of MinD through a combination of covalent labeling and mass spectrometry. Optimization of various steps for the assay has been done, and the assay can be applied to the future characterization of MinD polymer structure. Results from this assay, in combination with those from the kinetic measurements described here, will help to improve understanding about how membrane properties modulate MinD ATPase activity, and how this can influence the Min protein oscillation that is required to ensure normal bacterial cell division.

Relações min-max são objetos centrais em otimização combinatória. Elas basicamente afirmam que, numa dada estrutura, o valor ótimo de um certo problema de minimização é igual ao valor ótimo de um outro problema de maximização. Relações desse tipo fornecem boas caracterizações e descrições poliédricas para diversos problemas importantes, além de geralmente virem acompanhadas de algoritmos eficientes para os problemas em questão. Muitas vezes, tais algoritmos eficientes são obtidos naturalmente das provas construtivas dessas relações; mesmo quando isso não ocorre, essas relações revelam o suficiente sobre a estrutura combinatória dos problemas, levando ao desenvolvimento de algoritmos eficientes. O foco principal desta dissertação é o estudo dessas relações em grafos. Nossa ênfase é sobre grafos orientados. Apresentamos o poderoso arcabouço poliédrico de Edmonds e Giles envolvendo fluxos submodulares, bem como o algoritmo de Frank para um caso especial desse arcabouço: o teorema de Lucchesi-Younger. Derivamos também diversas relações min-max sobre o empacotamento de conectores, desde o teorema de ramificações disjuntas de Edmonds até o teorema de junções disjuntas de Feofiloff-Younger e Schrijver. Apresentamos também uma resenha completa sobre as conjecturas de Woodall e sua versão capacitada, conhecida como conjectura de Edmonds-Giles. Derivamos ainda algumas relações min-max clássicas sobre emparelhamentos, T-junções e S-caminhos. Para tanto, usamos um teorema de Frank, Tardos e Sebö e um arcabouço bastante geral devido a Chudnovsky, Geelen, Gerards, Goddyn, Lohman e Seymour. Ao longo do texto, ilustramos vários aspectos recorrentes, como o uso de ferramentas da combinatória poliédrica, a técnica do descruzamento, o uso de funções submodulares, matróides e propriedades de troca, bem como alguns resultados envolvendo subestruturas proibidas. / Min-max relations are central objects in combinatorial optimization. They basically state that, in a given structure, the optimum value of a certain minimization problem equals the optimum value of a different, maximization problem. Relations of this kind provide good characterizations and polyhedral descriptions to several important problems and, moreover, they often come with efficient algorithms for the corresponding problems. Usually, such efficient algorithms are obtained naturally from the constructive proofs involved; even when that is not the case, these relations reveal enough of the combinatorial structure of the problem, leading to the development of efficient algorithms. The main focus of this dissertation is the study of these relations in graphs. Our emphasis is on directed graphs. We present Edmonds and Giles\' powerful polyhedral framework concerning submodular flows, as well as Frank\'s algorithm for a special case of this framework: the Lucchesi-Younger Theorem. We also derive several min-max relations about packing connectors, starting with Edmonds\' Disjoint Branchings Theorem and ending with Feofiloff-Younger and Schrijver\'s Disjoint Dijoins Theorem. We further derive some classical min-max relations on matchings, T-joins and S-paths. To this end, we use a theorem due to Frank, Tardos, and Sebö and a general framework due to Chudnovsky, Geelen, Gerards, Goddyn, Lohman, and Seymour. Throughout the text, we illustrate several recurrent themes, such as the use of tools from polyhedral combinatorics, the uncrossing technique, the use of submodular functions, matroids and exchange properties, as well as some results involving forbidden substructures.