Concentric rotating cylinder and turbulent mixing devices have been frequently used in studying mixing and particle coagulation. However, these apparatus develop simple laminar flow (concentric rotating cylinders) or do not have well-defined flow (turbulent mixing devices). In this work, the eccentric rotating cylinder apparatus was investigated to find applicability for the improved study of coagulation based on the modified analytical solution of Ballal and Rivlin. Various eccentricity ratios, rotation speeds and viscosities were simulated to obtain optimum operating conditions. Inertial forces working on the fluid increased as the eccentricity ratio and rotation speed increase. As inertial forces increase, the eddy developed in wide clearance was more skewed in the direction of rotation. Both root-mean-square velocity gradient and average principal strain-rate, were increased by increasing eccentricity ratio. avaerage principal strain-rate were linearly increased as rotation speed increases, which suggested that average prinipal strain-rate can properly represent mixing intensity. Comparison of average principal strain-rate and RMS velocity gradient revealed that RMS velocity gradient overestimated mixing intensity and its error increased as eccentricity ratio increases. This study showed that the eccentric rotating cylinder apparatus has a non-uniform velocity distribution with well-defined fluid dynamics. Therefore, the eccentric rotating cylinder apparatus can be applicable as a model flocculator. However, in order to achieve reliable model predictability, the fluid Reynolds number must be below 200.

Multiple interacting mechanisms control the formation and dissolution of clots to maintain blood in a state of delicate balance. In addition to a myriad of biochemical reactions, rheological factors also play a crucial role in modulating the response of blood to external stimuli. The broad stimuli for clot formation were laid out, more than a century ago, in, what is now referred to as, Virchow’s triad. To date, a comprehensive model for clot formation and dissolution, that takes into account the biochemical, medical and rheological factors, has not been put into place, the existing models emphasizing either one or the other of the factors. In this dissertation, a model is developed for clot formation and dissolution that incorporates many of the relevant crucial factors that have a bearing on the problem. The model, though just a first step towards understanding a complex phenomenon goes further than previous models in integrating the biochemical, medical and rheological factors that come into play. The model is tested in some simple flow situations as part of an attempt to elucidate Virchow’s triad. Extensions to the model, along with detailed numerical studies, will hopefully aid in a clearer understanding of the phenomenon, and in making relevant clinical correlations.

Thèse de doctorat : sciences.Thermique-énergétique : Ecully, Ecole centrale de Lyon : 2003. / 123 réf.

Thèse de doctorat : sciences.Thermique-énergétique : Ecully, Ecole centrale de Lyon : 2003. / Titre provenant de l'écran-titre. 123 réf.

Some community water systems using sources containing elevated levels of fluoride, in the United States and worldwide, struggle to treat their drinking water to healthy fluoride concentrations. Many treatment plants in the U.S. currently use aluminum based salts, such as aluminum sulfate and polyaluminium chloride, as coagulants during conventional treatment for removal of particles from drinking water sources. Moreover, enhanced aluminum sulfate, or alum, coagulation requires higher concentrations of aluminum added to the process and has been shown to be effective for removal of disinfectant byproduct precursors, i.e., natural organic matter (NOM). The presence of fluoride may interfere with the formation of aluminum hydroxide precipitates, and interrelationships among NOM, aluminum precipitation and fluoride removal are not well understood. A fundamental understanding of how fluoride alters the properties of aluminum precipitates and how fluoride and NOM molecules compete as ligands interacting with soluble aluminum species is lacking. As a result, the development of guidelines for implementation and optimization of a treatment scheme that uses aluminum in the presence of fluoride requires a multi-faceted approach in which the development of a mechanistic understanding of these interactions is conducted in concert with macroscopic experiments to identify optimum conditions for simultaneous removal of fluoride and NOM. To date, little research has looked at the efficiency of removing both fluoride and organics from the perspective of the precipitation process. To provide a foundation for revising treatment techniques, this research evaluated the effect of co-precipitating aluminum in the presence of fluoride, organics, and in multi-ligand systems to characterize the solid precipitate and removal competition. This research verified the formation of a co-precipitate in the presence of fluoride and certain low molecular weight organics. Co-precipitation from organics and fluoride competes for removal, especially at low alum coagulant doses, complicating treatment for resource limited areas. / text

No description available.

No description available.

The use of dissolved air flotation (DAF) for drinking water treatment has steadily grown in popularity in Atlantic Canada for the treatment of low turbidity water supplies with high levels of algae or dissolved organic matter. Runoff from high intensity rainfall events may cause a rapid increase in turbidity and dissolved organic matter in rivers and lakes used for drinking water. A technical evaluation of a DAF water treatment plant (WTP) was conducted to determine the contributing factors to clearwell turbidity increases resulting from increased raw water turbidity and colour during intense rainfall and runoff events. The effect of chemical and operational factors on treatment of a low turbidity and colour water source as well as a high turbidity and colour water source were examined, including coagulant dose, coagulation pH, polyaluminum chloride (PACl) coagulant basicity and DAF recycle rate. In response to deteriorating water quality, it was found that increased coagulant addition inadvertently caused the loss of coagulation pH control in a full-scale DAF WTP, resulting in potentially elevated dissolved aluminum residuals entering the clearwell. This would have led to excessive aluminum hydroxide precipitation in the clearwell, and resulted in turbidity increases above the acceptable limit of 0.2 NTU. Turbidity was found to be better removed, and dissolved aluminum residuals minimized, when coagulation pH was set to the pH of minimum aluminum solubility vs. a lower pH of 6.0 during bench-scale DAF testing. A higher dose of coagulant was required to produce optimal removal of turbidity and dissolved organics at the pH of minimum solubility. The difference in bench-scale DAF treatment performance was found to be minimal when comparing sulphated PACl coagulants with 50 and 70+ % basicity. Charge analysis parameters zeta potential and streaming current were found to have a strong correlation in bench-scale testing, though the relationship between the two was affected by the coagulation pH. The results suggest that utilizing streaming current for coagulant dose control at a full-scale WTP would be best accomplished by establishing a consistent relationship between raw water quality, pH and other factors with streaming current experimentally before relying streaming current targets for dose control. Equivalent or improved DAF efficacy for solid-liquid separation was found when the recycle rate was lowered from 12 to 6 % in bench-scale tests and 12 to 8% in full-scale tests. The results suggested that maintaining an optimum air:solids ratio improved treatment performance, possibly by providing adequate bubble contact opportunities while minimizing excess shearing of the sludge blanket. The most significant finding of this research was that maintaining the coagulation pH in WTPs utilizing PACl coagulants is of utmost importance during source water quality deterioration in order to optimize treatment performance as well as prevent excess dissolved and precipitated aluminum from entering a public drinking water supply.

Thrombin-activatable fibrinolysis inhibitor (TAFI) is a human plasma zymogen that acts as a molecular link between the coagulation and fibrinolytic cascades. TAFI can be activated by thrombin and plasmin but the reaction is enhanced significantly when thrombin is in a complex with the endothelial cofactor thrombomodulin (TM). The in vitro properties of TAFI have been extensively characterized. Activated TAFI (TAFIa) is a thermally unstable enzyme that attenuates fibrinolysis by catalyzing the removal of basic residues from partially degraded fibrin. The in vivo role of the TAFI pathway, however, is poorly defined and very little is known about the role of different activators in regulating the TAFI pathway. In the present study, we have constructed and characterized various TAFI mutants that are resistant to activation by specific activators. Based on peptide sequence studies, these mutants were constructed by altering key amino acid residues surrounding the scissile R92-A93 bond. We measured the thermal stabilities of all our mutants and found them to be similar to wild type TAFI. We have identified that the TAFI mutants P91S, R92K, and S90P are impaired in activation by thrombin or thrombin-TM, thrombin alone, and thrombin alone or plasmin, respectively. The TAFI mutants A93V and S94V were predicted to be resistant to activation by plasmin but this was not observed. The triple mutant, DVV was not activated by any of the aforementioned activators. Finally, we have used in vitro fibrin clot lysis assays to evaluate the antifibrinolytic potential of our variants and were able to correlate their effectiveness with their respective activation kinetics. In summary, we have developed activation resistant TAFI variants that can potentially be used to explore the role of the TAFI pathway in vivo. / Thesis (Master, Biochemistry) -- Queen's University, 2009-01-30 11:44:37.191

No description available.