There are several reasons for reducing particulate formation as a result of combustion processes and to date, a number of approaches have been proposed to numerically predict soot. There is a trade-off between accuracy and computational cost and processing time. Two equation semi-empirical models have been used, with some success, to reconcile the need for fast solution turn around and accuracy. However, these models do not account for the mass balance between the gas phase and soot. In this study, the effects of mass conservation of the soot precursors in the gas phase were investigated in an ethylene-air laminar flame simulation at atmospheric pressure. Soot formation was predicted with a two-equation model. Then the model was modified for predicting soot in a turbulent ethylene-air flame operating at 1 atm. The new model is a [2+1]-equation model which accounts for the mass conservation of soot precursors.

In this study, two new Multi-Objective Optimization (MOO) techniques are developed. The two new techniques, the Objective-Based Gradient Algorithm (OBGA) and the Principal Component Grid Algorithm (PCGA), were developed with the goals of improving the accuracy and efficiency of the Pareto domain approximation relative to current MOO techniques. Both methods were compared to current MOO techniques using several test problems. It was found that both the OBGA and PCGA systematically produced a more accurate Pareto domain than current MOO techniques used for comparison, for all problems studied. The OBGA requires less computation time than the current MOO methods for relatively simple problems whereas for more complex objective functions, the computation time was larger. On the other hand, the efficiency of the PCGA was higher than the current MOO techniques for all problems tested. The new techniques were also applied to complex chemical engineering problems. The OBGA was applied to an industrial reactor producing ethylene oxide from ethylene. The optimization varied four of the reactor input parameters, and the selectivity, productivity and a safety factor related to the presence of oxygen in the reactor were maximized. From the optimization results, recommendations were made based on the ideal reactor operating conditions, and the control of key reactor parameters. The PCGA was applied to a PI controller model to develop new tuning methods based on the Pareto domain. The developed controller tuning methods were compared to several previously developed controller correlations. It was found that all previously developed controller correlations showed equal or worse performance than that based on the Pareto domain. The tuning methods were applied to a fourth order process and a process with a disturbance, and demonstrated excellent performance.

There has been a growing demand for specific linear alpha olefins in the polyethylene industry in order to control polymer rheology. This growing demand thereby increases the need for highly active and selective ethylene oligomerization catalysts. Chromium-based catalysts continue to be of high interest for this application due to this metal’s versatility in both selective and non selective ethylene oligomerization. Ligand design is an important consideration in oligomerization chemistry: the ability of the ligand to stabilize low valent chromium and to support a two-electron redox process will allow the catalytic systems to follow the selective ring expansion mechanism for oligomerization. Chelating aminophosphane based ligands, previously studied by our group, have been shown to support both tri- and tetramerization of ethylene. We have explored modifications of one of the NP arms by replacing with a different coordinating group in an attempt to further stabilize the monovalent state of chromium and increase selectivity. Other ligands explored in this work are pyrrole based ligands, which have shown high activity and selectivity towards ethylene oligomerization. One example of this is the commercial Chevron-Phillips system. Recently, the co-polymerization of CO2 with epoxides has been studied as an environmentally friendly route to convert CO2 into biodegradable polymers. The first successful catalytic system to achieve these results consisted of a diethyl-zinc complex. More recently, aluminum, chromium, cadmium and cobalt have been studied as polycarbonate catalysts. To date, the only reported chromium catalysts for CO2-epoxide copolymerization are Cr-salen and Cr-porphyrin complexes, studied by Darrensbourg and Holmes, respectively. We were particularly interested in finding new chromium-based complexes able to catalyze epoxide/CO2 copolymerization by using molecules with the nitrogen donor motif embedded in different functions such as neutral pyridines with anionic pendants, pyrroles with either imine or amine pendants, or a combination of these.

Nowadays, cancer treatment and tissue regeneration have attracted large amount of attention. Single Wall Carbon Nanotubes (SWNT) possess large surface area and outstanding optical and electrical performance, making it a promising component in cancer therapy and tissue reengineering systems. In this study, four disease treating systems based on SWNT are developed. They are pH-sensitive poly(ethylene glycol)-doxorubicin(PEG-DOX)@SWNT drug release system, temperature sensitive SWNT hydrogel, SWNT based biocompatible magnetic hydrogel and biocompatible SWNT-gelatin-F127-cysteamine hydrogel for tissue engineering. The successfully synthesized target compounds are characterized by FTIR. The in vitro release of drugs from the drug release systems is evaluated upon changes of pH values and the laser scanning. The effect of cancer treatment systems on specific kind of cells are examined by confocal laser scanning microscopy (CLSM). The results indicate that all of the four systems show great potential in the biomedical applications especially in disease therapy applications.

Bacteria that provide benefit to plants are considered to be plant growth-promoting bacteria (PGPB) and can facilitate plant growth by a number of different mechanisms. Plant growth-promoting bacteria that are able to utilize the plant compound 1-aminocyclopropane-1-carboxylate (ACC) as a sole source of nitrogen, as a consequence of possessing the enzyme ACC deaminase, can protect host plants from a number of environmental stresses. In addition to ACC deaminase, PGPB may utilize other mechanisms to facilitate plant growth including IAA synthesis, siderophore production, phosphate solubilization activity, ammonia production, and antibiotic production. Plant growth-promoting bacterial endophytes employ similar plant growth promotion mechanisms to those used by rhizospheric PGPB. In fact, bacterial endophytes are PGPB that go one step further and colonize the inside of the plant tissues and provide more efficient and prompted protection to their hosts compared to those that bind exclusively to the plant’s rhizosphere. Therefore, it is likely that endophytic plant growth-promoting bacteria will be superior to similar non-endophytic bacterial strains in promoting plant growth under a wide range of environmental conditions. In the work reported here, new bacterial endophytes were isolated and characterized. Among twenty-five ACC deaminase positive strains, two best strains were selected and ACC deaminase deficient mutants were constructed. The ability of two newly isolated 1-aminocyclopropane-1-carboxylate (ACC) deaminase-containing plant growth-promoting bacterial endophytes Pseudomonas fluorescens YsS6, Pseudomonas migulae 8R6 and their ACC deaminase deficient mutants was shown to 1) delay the senescence of mini carnation cut flowers and 2) to facilitate tomato plant growth under salinity stress. In the mini carnation flower senescence evaluation, the only difference between wild-type and mutant bacterial endophytes was ACC deaminase activity, our results demonstrate that this enzyme is directly responsible for a significant delay in flower senescence. Despite containing ACC deaminase activity, the rhizosphere-binding PGPB Pseudomonas putida UW4 was not taken up by the cut flowers and therefore had no effect on prolonging flower shelf life. In evaluating the effect of bacterial endophytes under salt stress, tomato plants treated with either of the wild-type strains of the two selected bacterial endophytes demonstrated early flowering and fruiting and had significantly greater numbers of flowers, buds, and fruits than either the corresponding ACC deaminase mutant strain-treated plants or the control plants. Although both bacterial endophytes P. fluorescens YsS6 and P. migulae 8R6 showed significant plant growth-promotion capabilities, P. migulae 8R6 demonstrated better plant growth facilitation under salt stress than did P. fluorescens YsS6. P. migulae 8R6 treated tomato plants demonstrated the least sodium uptake, the highest chlorophyll content, and highest fresh and dry biomass. The results of the work presented here suggest that ACC deaminase containing selected bacterial endophytes could be employed as environmentally friendly adjuncts to agricultural and horticultural practice.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 59-60) Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 263-287) Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 263-287) Also available online.

Thesis (M.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 119-125). Also available in electronic format on the Internet.