Abstract A boundary element method numerical scheme is developed to study the dynamic response and the wave damping characteristics of a floating structure under an incident wave approaching. The coupled surge, heave and pitch motion of a floating structure are included in the model. The equation of motion of the numerical model has been set up; meanwhile the solution of equations has been solved through the Runge-Kutta fifth order method. The hydrodynamic physical model tests have been carried out to verify the goodness of the numerical model. The numerical solutions and the experimental results have good agreements. It means that the BEM developed by this paper has its own accuracy. The study results show that the wave with shorter period has better effect on wave damping. In general, a floating breakwater, which is deeper under the water and wider in width, has smaller transmission coefficients. Practically when designing a floating structure, it suggests that the designer should increase the width rather than deepen the depth of structure. It is because the effects of dissipating wave energy are more obvious when increasing the width than the depth.

Extr. de--Uppsala (Suède)--Université d'Uppsala, 2000. / Bibliogr. p. 87-91. Index.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

Thesis (M. Agr. St.)--University of Queensland, Gatton, 2002. / Includes bibliographical references.

V. 1. Single particle motion -- v. 2. Nuclear deformations. / Originally published as 2 separate volumes. Title from ebook title screen. Includes bibliographical references (v. 2, p. 693-730) and index.

In prokaryotic cells, the nucleoid contains almost all the genetic materials as well as a number of nucleoid structuring factors. The nucleoid-associated proteins (NAPs) are known to have low molecular weight and the ability to form dimer or oligomer, and most of them can bind to DNA for regulation of gene expression. The Histone-like nucleoid structuring protein H-NS, well studied as one of the NAPs, acts as a global transcriptional repressor. It has independent functional N-terminal domain for oligomerization and C-terminal domain for DNA binding, joined by a flexible linker. H-NS contributes to horizontal genes transfer and responses to environmental factors like temperature or pH, which would influence the oligomerization ability of H-NS and DNA binding. The α-hemolysin expression-modulating protein Hha is a member of the Hha-YmoA family, expressed only in Gram-negative Enterobacteriaceae as a modulator of virulence factors expression. In E. coli, the binding of Hha to H-NS can modulate the expression of α-hemolysin operon, which is essential for the H-NS-regulated gene expression. In this study, both Hha and the oligomerization domain of H-NS (H-NS64) were expressed in E. coli and the purified proteins were crystallized. The Hha crystals diffracted to 2.2 Å; and the HhA/H-NS complex crystals diffracted to 1.8 Å. Both structures were successfully determined by molecular replacement method. Comparisons were carried out between the published apo Hha and H-NS structures and our complex structures. The structures showed the binding details between H-NS and Hha and also conformational changes of each protein, which may indicate how Hha regulates gene expressions through H-NS. / published_or_final_version / Physiology / Master / Master of Philosophy

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Organophosphonates are characterized by a very stable carbon-phosphorus bond. Eshcherichia coli and many other strains of bacteria possess a multi-enzyme system called carbon-phosphorus (C-P) lyase that enables these organisms to cleave the C-P bond of organophosphonates when inorganic phosphate is scarce in the local environment. Genetic studies have demonstrated that C-P lyase is encoded by the fourteen-gene phn operon, phnCDEFGHIJKLMNOP. However, the mechanism for C-P bond cleavage is still unclear. We have expressed, purified, and characterized phnP from this operon. PhnP is a phosphodiesterase which will hydrolyze both bis-(p-nitrophenyl) phosphate and 2’:3’-cyclic nucleotides as substrates. In collaboration with Dr. Zongchao Jia and Katarenya Podzelinska (Queen’s Biochemistry), we have crystallized phnP and solved the crystal structure at a resolution of 1.3 Å. The structure displayed similarity to zinc-dependent metallo-β-lactamase family proteins. However, phnP displays unique structural features with two metal binding sites per monomer: the active site containing potentially two manganese ions, and a ‘structural’ site coordinating one zinc ion. Potential active site residues were identified and corresponding point mutations were generated by site-directed mutagenesis. Studies based on the importance of these residues and the knowledge from our high resolution structure will help elucidate the mechanism of phnP as well as its function in the C-P lyase pathway. Furthermore, we performed a broad range of ligand screening for phnH, another key member from the C-P lyase pathway, by ITC experiments, co-crystallization and high throughput ligand screening. However, all the trials for the identification of the true physiological substrate for phnH proved unsuccessful. Although the mechanism of C-P bond cleavage by C-P lyase still remains unclear, we synthesized a fluorescently labelled organophosphonate (FPn) and utilized it for probing the in vivo degradation of the C-P bond by wild type E. coli and various mutants. Analysis by TLC and mass spectrometry demonstrated the production of the expected alkane product. With this promising fluorescent probe, potential intermediates and substrates can be identified for individual C-P lyase enzymes. Taken together, our studies on the C-P lyase pathway will contribute to elucidate the still unknown mechanism of the cleavage of the stable C-P bond. / Thesis (Master, Chemistry) -- Queen's University, 2008-08-29 12:11:55.179

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