Thesis (M. Phil.)--University of Hong Kong, 1991.

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 187-203).

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 261-262).

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 184-189).

published_or_final_version / abstract / toc / Botany / Master / Master of Philosophy

This study investigated the performance of the biomass Eichhornia crassipes plant (ECP) as an additive in water-based drilling-mud. ECP is an invasive plant of fresh water ecosystems, so its use in drilling operations provides a low-cost, sustainable option that has off-site environmental benefits. Mechanical tests were conducted on ECP fibres to determine their stiffness under dried and water-wet conditions. Initial tensile tests on nylon fibre determined potential experimental artefacts with the experimental approach. The dried fibres had a water content of 8.163 wt. % (SE 0.636), whereas the wet fibres were 93.43 wt.% (SE 0.294). Water wet fibres had a lower modulus of elasticity than dried fibres and therefore, dried fibres have less tensile strength than wet fibres (Mean = 45.16 MPa; SE = 5.023; N = 41). Rheological properties of bentonite-based drilling muds amended with ECP at different concentrations were also studied. These muds were prepared by mixing ECP fragments at various concentrations (%w/w) with bentonite-water solutions and aged under ambient conditions. Mud viscosity gradually decreased with increasing shear rate, showing characteristic shear-thinning behaviour. Lost circulation of bentonite-water solutions mixed with ECP fragments were assessed with static filtration experiments. Slots and single perforated discs were designed to mimic fractures surrounding drilled boreholes. From a broad range of testing conditions, it was found that ECP fibres significantly decrease lost circulation by bridging fractures. An optimal concentration of 0.83 % by weight of ground plant stalks mixed with 6.28% bentonite in water improved rheology and filtration properties. A bridging gap model for a single fibre showed that ground stalk was less deflected than dried fibre when bridged an opening fissure. The findings of this research create an alternative to use ECP as lost circulation material in oil and gas drilling operations.

published_or_final_version / Botany / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 146-158).

A research report submitted to the Faculty of Science,University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science. 2015. / Because water hyacinth growth is highly dependent on nutrient availability, growth of the weevil Neochetina eichhorniae, which feeds only on water hyacinth, is closely linked to the plants’ nutrient status. The aim of this research was to investigate whether the nutrient levels could influence the larval development and larval feeding on water hyacinth. To investigate this, water hyacinth plants were grown at three different nutrient concentrations (high (6 mg/l N; 0. 83 mg/l P), medium (2.8 mg/l N; 0.4 mg/l P) and low (0.7 mg/l N; 0.01 mg/l) chosen according to a range of nutrient conditions found in South African water bodies. Control plants, without larval inoculation and treatment plants, with two larvae per plant were used. Plant biomass and other plant growth parameters were measured every week. We predicted a higher larval feeding rate on plants grown at the low nutrient level and faster larval development and a higher larval survival rate at the higher nutrient levels.

Thesis (M. Phil.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 192-208).