[Formulae and special characters can only be approximated here. Please see the pdf version of the Abstract for an accurate reproduction.] Since the damping functions employed by most of the low-Reynolds-number models are related to the non-dimensional distance y+[ special character ??? near-wall non-dimensional distance in y direction], which is based on local wall shear stress, these models become invalid for separated flows, because the wall shear stress is zero at the reattachment point. In addition, the pressure-velocity correlation term is neglected in most of these models, although this term is shown in this thesis to be important in the near-wall region for simple flows and large pressure gradient flows. In this thesis, two main efforts are made to improve the k ??? [special character - dissipation rate] model. First, based on Myong and Kasagi???s (1990) low-Reynolds-number model (hereafter referred to as MK model), a more general damping function [special character - turbulent viscosity damping function in LRN turbulent model] is postulated which only depends on the Reynolds numbers [formula ??? near-wall turbulence Reynolds number]. Second, a form for the pressure-velocity correlation term is postulated based on the Poisson equation for pressure fluctuations. This modified model predicts the turbulent flow over a flat plate very well. It is found that the inclusion of the pressure-velocity correlation term leads to significant improvement of the prediction of near-wall turbulence kinetic energy. When the model is applied to turbulent flow over a backward-facing step, it produces better predictions than the traditional k ??? [special character - dissipation rate] model, FLUENT???s two-layer model and the MK model. Again, the pressure-velocity correlation term improves the turbulence kinetic energy prediction in the separated region over that of other models investigated here. The studies of numerical methods concerning computational domain size and grid spacing reveal that a very large domain size is required for accurate flat plate flow computation. They also show that a fine grid distribution in the near-wall region upstream of the step is necessary for acceptable flow prediction accuracy in the downstream separated region.

[Truncated abstract] The feasibility of using interlocked light gauge sheet piles to form a deep cross-sectional wall embedded in a residual slope or with a berm support is explored. This thesis compares the performance of a large section modulus sheet pile wall as an alternative to a concrete diaphragm wall, acting as an embedded cantilever wall on a slope (ECWS) by means of experimental centrifuge tests, numerical models and analytical methods. Abaqus (Hibbitt, Karlsson and Sorensen Inc, 1997) was used to conduct extensive numerical trials on the structural performance of the sheet pile wall model prior to the actual physical testing. The Abaqus results showed that the integrity of the interlock and reduced modulus action (RMA) due to slippage along the interlocked joint did not cause premature buckling of the thin wall even at the ultimate load. Further, a comparative study using centrifuge tests on 1:30 scaled models and Plaxis analysis demonstrated that under the worst condition with high water table, the rigid sheet pile wall of 1.32 m cross-sectional width carried a higher ultimate surcharge load with a much lower top of wall deflection, compared to a more flexible 0.6 m thick cracked concrete diaphragm wall. The analysis of the wall/soil/slope interactions for an ECWS involves many inter-dependent variables in addition to the complications of considering an adjacent slope or a berm support. It is difficult for existing analytical approaches to take all these factors into account, and some form of numerical analysis, calibrated through field data and results from centrifuge model tests is necessary. From the observations of the centrifuge tests and finite element analysis, major assumptions about the failure of a stiff ECWS in a rotational mode were deduced and adopted in the proposed limiting equilibrium method (Leq). The plane strain Leq ECWS Abstract ii analysis is based on the framework of minimum upper bound limiting equilibrium with planar failure planes and a Mohr-Coulomb soil model. As compared to the traditional limit equilibrium analysis, the Leq method is a fully coupled analysis using the shear strength reduction technique (SSR). New formulations are proposed for the development of horizontal active and passive pressure distributions based on the experimental and FE models. The proposed active pressure profile used is derived by combining the Coulomb and Krey method, and empirically back-figured to curve-fit the centrifuge tests by Morris (2005). The proposed passive pressure profile of a rigid rotational wall in failure is adjusted to allow for an adjacent slope or berm support through a presumed elasto-plastic deformation instead of a linear rigid translation of the passive wedge. ... A parametric study was later undertaken using the Leq method to develop a series of non-dimensionalised graphs to study and draw summarised conclusions on the behaviour of the ECWS. The final conclusions on the comparative study of the centrifuge tests, Plaxis and Leq analyses demonstrated that the alternative light gauge steel sheet pile performed very well as an ECWS. A key factor in the performance of the sheet pile wall was attributed to the large 1.32 m cross-sectional width of the interlocked sections. This provided high bending stiffness and high moment stability from shear stresses acting on the back and front faces of the wall.

This thesis is concerned with phytoestrogenic isoflavones, which are a group of plant-derived compounds that can be consumed in the diet or as over-the-counter preparations for self-medication, and have been associated with a wide range of health benefits. However, unlike the extract of St John's wort and grapefruit juice, little is known about the potential for phytoestrogenic isoflavones to be involved in pharmacokinetic interactions. This thesis describes a series of experiments that investigate that potential by assessing the effects of the isoflavones on intestinal P-glycoprotein-mediated transport, hepatic metabolism, and hepatic cell membrane transport of conventional drugs.

Cette thèse est consacrée à l'étude expérimentale du phénomène de transfert de spin. Ce mécanisme, introduit théoriquement en 1996 par J. Slonczewski, permet d'orienter l'aimantation d'un matériau ferromagnétique sans champ appliqué, mais seulement par injection d'un courant polarisé en spin et transfert de spin vers le matériau considéré. Les fortes densités de courant à injecter pour observer l'effet, de l'ordre de 107 A.cm-2, imposent le recours à des nanostructures. Nous avons suivi deux voies pour caractériser cet effet nouveau de transfert de spin depuis un courant vers une aimantation. D'une part, à l'instar des tout premiers résultats expérimentaux obtenus à Cornell University en 2000, nous avons étudié cet effet dans des piliers magnétiques submicroniques de Co/Cu/Co. Nous avons pu clairement mettre en évidence le renversement d'aimantation par un courant polarisé en spin a champ nul. Ensuite, nous nous sommes intéressés à la dépendance en champ des courants critiques. Cette étude approfondie nous a permis de tracer le diagramme de phase champ-courant, nous fournissant des informations importantes quant aux mécanismes microscopiques à l'origine du phénomène de renversement d'aimantation par injection de spin. La deuxième partie de ma thèse concerne le cas des barreaux de vanne de spin Co/Cu/NiFe dans lesquels la modification d'aimantation est due au déplacement de paroi magnétique induit par transfert de spin à partir d'un courant polarisé en spin. Pour des champs proche de zéro, une paroi magnétique peut être déplacée uniquement sous l'action du courant entre des centres de piégeage et, en accord avec les conclusions du modèle de Berger, le déplacement s'effectue dans des directions opposées pour des courants opposés. La densité de courant critique requise pour déplacer la paroi est de l'ordre de quelques 106 A/cm², un ordre de grandeur plus faible que les courants nécessaires pour entraîner un renversement d'aimantation dans les structures multicouches de type piliers. Ces mesures constituent la première mise en évidence directe et en temps réel de déplacement de parois par transfert de spin dans des nanostructures magnétiques.

<p>Invasive Candida infection is an increasing cause of morbidity and mortality in the immunocompromised patient. Molecular diagnosis based on genomic amplification methods, such as real time PCR, has been reported as an alternative to conventional culture for early detection of invasive candidiasis. The template DNA extraction step has been the major limitation in most reported nucleic acid based assays, due to problems in breaking fungal cell walls and incomplete purification in PCR inhibitor substances.</p><p>The aim of this study was to compare enzymatic cell wall disruption using recombinant lyticase with mechanical disruption using glass beads. The QIAamp tissue kit was compared with two automated DNA extraction robots, the BioRobot M48 and NucliSens easyMAG, to determine their sensitivity, reliability and duration for DNA release of C. albicans. Mechanical cell wall disruption shortened and facilitated the extraction procedure, but the quantity of released DNA was significantly lower than when enzymatic cell wall disruption was used. Use of robots did not significantly shorten the DNA extraction time, compared with manual DNA extraction. However the NucliSens easyMAG resulted in a higher yield of target DNA compared to the BioRobot M48 and the manual QIAamp tissue kit.</p> / <p>Invasiva svampinfektioner är ett stort problem hos patienter med dåligt immunförsvar. Förekomst av invasiva svampinfektioner har ökat under senare år och medför hög dödlighet. En svampinfektion som inte snabbt diagnostiseras och behandlas kan bli livshotande om patientens kondition är dålig. Candida albicans är den vanligaste orsaken till invasiva svampinfektioner. Med traditionell svampidentifiering kan det ta dagar till veckor att isolera och artbestämma svampen. En snabbare metod att detektera Candida är att använda sig av molekylärbiologiska metoder som påvisar svampens arvsmassa, DNA. Svampar har en cellvägg som är svår att bryta ner och därför är DNA extraktionssteget ett av de mest rapporterade problemen vid DNA svampdiagnostik.</p><p>Syftet med denna studie var att jämföra enzymatisk och mekanisk cellväggsnedbrytning av C. albicans med hjälp av enzymet lyticase respektive glaskulor. Vi jämförde också en manuell metod med två automatiska robotar för att bestämma deras känslighet, tillförlitlighet och tidsåtgång för DNA-extraktion från C. albicans. De slutsatser som nåtts är att den enzymatiska cellväggsnedbrytningen var känsligare men betydligt mer tidskrävande än den mekaniska cellväggsnedbrytningen. Denna studie visade även att en av de automatiska systemen extraherade signifikant mer DNA än den manuella metoden.</p>

The thesis deals with the problem of friction during rapid transient 1-D flows in a pipe caused by water hammers. The evolution of the wall shear stress is interpreted in terms of two steps. The first step is the dramatic change of the wall shear stress during the passage of the pressure wave; the corresponding new value of the shear stress is much greater than the value predicted in steady-state. The second step, which begins after the passage of the pressure wave, is a relaxation process; here the shear stress decreases, tending to the new steady-state value corresponding to the new average velocity. The Extended Irreversible Thermodynamics theory is proposed as a tool to model the wall shear stress during the relaxation process. The Friction Relaxation Model presented in this thesis describes both steps of the evolution of the wall shear stress during water hammers, and therefore it enables to take into account the information about the velocity gradient at the wall, which is otherwise not available in 1D modelling.

A new method is proposed for correctly modeling the long range interaction between a fluid and a bounding wall in atomistic simulations. This method incorporates the molecular structure of the solid substrate while allowing for a finite interaction cutoff by making a proper estimation of long range correction for the fluid-wall interaction. The method is then applied to a molecular dynamic simulation of a spreading droplet. Conparison to simulations using several other previously used methods shows that the long range correction can be significant in some circumstances. / Singapore-MIT Alliance (SMA)

Ductile steel plate shear walls are an established lateral load resisting system. Past research indicates that cold-rolled infill panels less than 1 mm in thickness present one solution to an overstrength problem arising from selecting an infill panel thickness based on ease of welding and handling. This research program examines several possible welding procedures and joint geometry to connect the thin infill panel to the thick boundary elements. Primary welding parameters include short-circuiting gas metal arc welding process, electrode and shielding gas selection, heat input, and use of a chill strip. Four configurations of the infill panel-to-boundary element joint and two configurations of a lap splice joint between two sheets of thin steel in the infill panel were tested in monotonic tension and cyclic tension-compression. A quasi-static cyclic test of a single-storey moment resisting frame steel plate shear wall validated the use of one welding procedure and joint geometry. / Structural Engineering

The behavior of steel plate shear walls under the effects of lateral loads depends on the stiffness of the surrounding frame members. Previous research has quantified the minimum required stiffness of columns in the middle stories of steel plate shear wall systems. As the columns of the steel plate shear wall system are subjected to both large axial forces and bending moments, use of composite columns is a viable option in this system. Among the different types of composite columns, the recently developed partially encased composite columns with built-up steel sections have some advantages over other types of composite columns and thus their performance as columns in steel plate shear wall systems needs to be studied. In the first part of this research, a numerical and analytical study has developed a new design parameter and determined the minimum required stiffness of end beams in end panels of the steel plate shear wall system. The effect of the rigidity of the frame connections on the uniformity of the tension field has also been studied in this part. The second part of this research includes two large scale tests on steel plate shear walls with built-up partially encased composite (PEC) columns. One of the test specimens was modular and the other one used reduced beam sections in the frame. The results of the tests show that the columns were stiff enough to anchor the infill plate. The PEC columns in these tests performed in a ductile manner. The overall system behavior was ductile, stable and the specimens showed good seismic behavior and redundancy. Based on the results and observations of this research, design recommendations for PEC columns used as the vertical boundary members of steel plate shear walls are provided. / Structural Engineering

The soil-borne filamentous fungus Trichoderma virens is a biocontrol agent with a well known ability to produce antibiotics, parasitize pathogenic fungi and induce systemic resistance in plants. Here we report the identification, purification and characterization of an elicitor secreted by T. virens; a small protein designated Sm1 (small protein 1). Confrontation and disk assays demonstrated that Sm1 lacks toxic activity against plants and microbes. Native, purified Sm1 triggers production of reactive oxygen species in rice (Oryza sativa) and cotton (Gossypium hirsutum), and induces the expression of defense related genes both locally and systemically in cotton. Gene expression analysis revealed that SM1 is expressed throughout fungal development and is transcriptionally regulated by nutrient conditions and the presence of a host plant. When T. virens was co-cultured with cotton in an axenic hydroponic system, SM1 expression and secretion of the protein was significantly higher than when the fungus was grown alone. These results indicate that Sm1 is involved in plant-Trichoderma recognition and the induction of resistance by activation of plant defense mechanisms. Following the cloning of SM1, strains disrupted in or over-expressing SM1 were generated. Targeted gene disruption revealed that SM1 was not involved in fungal development. Expression of defense related genes in cotton and maize (Zea mays) was induced locally and systemically following colonization by T. virens in the hydroponic system. Low levels of expression of cotton or maize defense genes were found when seedlings were grown with a T. virens strain disrupted in SM1, ssupporting the Sm1-elicitor hypothesis. Additionally, unique proteins in T.virens-cotton/maize interaction were identified. Thus, the induction of defense responses in two agriculturally important crops appears to be microbially mediated. Functional analysis of a cell wall degrading enzyme, beta-1,6-glucananse (Tv-bgn3) from T. virens, demonstrated involvement of this enzyme indirectly in mycoparasitic activity of T. virens. Protein extracts from the strain disrupted in TV-BGN3 displayed reduced capability to inhibit growth of Pythium ultimum as compared to the wild-type. Additionally, protein extracts from the strains co-expressed with TV-BGN2 (beta-1,3-glucananse) from T. virens showed a significantly increased capability to inhibit growth of P. ultimum and Rhizoctonia solani hyphae.