No description available.

published_or_final_version / Botany / Master / Master of Philosophy

No description available.

published_or_final_version / Botany / Master / Master of Philosophy

This microcosm study demonstrated the enhanced anaerobic transformation of vinyl chloride (VC) to ethylene. A previous microcosm study from Point Mugu site showed the accumulation of VC due to the slow transformation step of VC to ethylene. To overcome the rate-limiting step, two laboratory experiments tested the effect of trichloroethylene (TCE) additions on the rate enhancement, repeated low TCE additions and high TCE concentration additions. TCE (2 ��mol) was repeatedly added over a two week interval. In a parallel study, an equal amount of VC was added to another set of microcosms. TCE addition increased VC transformation to ethylene, with nearly 19% VC conversion to ethylene compared to 4% VC conversion in the VC added controls. However, the increased VC transformation rates were not sufficient enough to avoid VC accumulation. Rate of VC transformation decreased once TCE addition was stopped. This indicated the mixed culture required the transformation of TCE to maintain VC transformation rates. With TCE added at high concentrations (100 mg/L and 200 mg/L), nearly complete transformation of TCE to ethylene was observed. After the addition of high TCE concentrations, low concentration TCE (3 ��mol) was added and near 95% transformed to ethylene in 45 days. Two different low hydrogen yielding substrates, butyrate and propionate, were tested. Both were equally effective in promoting TCE dechlorination. Methanogenesis was inhibited at high TCE concentration with both substrates. Kinetic analysis of VC transformation data showed VC transformation followed the first order kinetics with respect to concentrations using a modified Monod equation. First-order kinetic constants increased after the addition of high ICE concentrations. After 200 mg/L of TCE addition, the first-order kinetic constant increased by factor of six compared to the rate obtained from the earlier low TCE concentration addition. However, reintroduction of TCE at low concentration maintained similar enhanced kinetic constants, as achieved at high concentration. This indicated the enhancement of VC transformation to ethylene was likely due to the growth of microorganisms using TCE as a terminal electron acceptor. These microorganisms were likely responsible for the transformation of VC to ethylene. / Graduation date: 2001

Lettuce is a cool-seasoned vegetable, which is very fragile and should therefore be handled with great care. Processed lettuce (loose leaves and shredded lettuce), is more prone to handling damage than intact lettuce crisp heads. Lettuce produces very little ethylene (less than 0,1 ul/kg-1/h-1), but is extremely sensitive to damage from ethylene. In lettuce, ethylene induces a postharvest physiological disorder known as russet spotting. Due to its climacteric nature, lettuce is very sensitive to ethylene. Ethylene sets in motion a programmed series of events that accelerates senescence in lettuce. Besides causing russet spotting, ethylene also stimulates cell membrane and cell wall damage. In wounded (lightly processed) tissue ethylene production increases, resulting in increased russet spotting and accelerated senescence. Reactive oxygen species are likely role-players involved in membrane damage. Hydrogen peroxide is the primary mediator in membrane degradation; hydrogen peroxide levels remained constantly high during storage. Plant free radical scavengers, such as ascorbate peroxidase, catalase and superoxide dismutase protect membranes from damage by free oxygen radicals. The activities of ascorbate peroxidase and catalase was determined during storage and was found not to increase during senescence. Applying different postharvest treatments such as controlled atmospheric storage, 1-MCP, and short heat-shocks to iceberg lettuce significantly suppressed the negative effects of ethylene. These treatments were effective in suppressing russet spotting and senescence as indicated by reduction in moisture loss and ion leakage. Treatment with electro-activated water, did not affect ethylene sensitivity, but did limit moisture loss by lowering the rate of transpiration by increasing stomatal resistance, thus contributing to the retention of crispness and improved longevity. / Prof. C.S. Whitehead

published_or_final_version / abstract / Botany / Master / Master of Philosophy

published_or_final_version / Botany / Master / Master of Philosophy

Ph.D. (Chemistry) / Compounds 3-ferrocenylpyrazole (L1) 3-ferrocenyl-5-methylpyrazole (L2) and 4- ferrocenyl-1-methyl diketone (L7) were synthesized according to literature procedure, while compounds 3-ferrocenylpyrazolyl-methylenepyridine (L3), 3-ferrocenyl-5- methylpyrazolyl-methylenepyridine (L4), 3-ferrocenylpyrazolyl-ethyl amine (L5) and 3- ferrocenyl-5-methylpyrazolyl-ethylamine (L6) were prepared by phase transfer alkylation of the 2,6-bis(bromomethyl)pyridine or 2-bromoethylamine with the appropriate ferrocenylpyrazole L1 or L2 in a 1:1 ratio. These compounds L3-L6 show structural isomers labelled a and b. The isomers were in a ratio of 4:1 for L3 and L4 while for L5 and L6 the isomers were 2:1 ratio...

M.Tech. / In this study, ethylene vinyl acetate-fly ash (EVA-FA) composites were explored for the removal of phenols from water. The composites were prepared from EVA and untreated and acid treated fly ash via the melt-mixing technique using a rheomixer. The fly ash was characterised by X-ray fluorescence (XRF), X-ray diffraction (XRD) scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) surface area measurement. Fly ash is composed mainly of SiO2, Al2O3, CaO and Fe2O3. Modified fly ash gave a better specific surface area of 0.4180 m2/g, while 0.0710 m2/g was obtained for unmodified fly-ash due to the disintegration of the outer layer which resulted in smaller particles, hence a larger surface area. EVA-FA composites were prepared from fly ash loadings of 3 to 20% and further characterised by XRD, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and SEM. XRD showed successful incorporation of fly ash into the EVA matrix through the appearance of fly ash diffraction peaks on the EVA-FA composite diffraction pattern. The incorporation of fly ash into the EVA matrix resulted in an improvement in the thermal stability of EVA, but did not have an effect on the melting temperature of the composites. However, a decrease in crystallisation temperature was observed. SEM micrographs revealed uniform dispersion of fly ash particles in the polymer matrix. Adsorption studies were performed using p-chlorophenol (PCP), 2,4,6-trichlorophenol (TCP) and p-nitrophenol (PNP) as model pollutants. An increase in adsorption efficiency of EVA-FA composites was observed as fly ash loading was increased from 3 to 10%. Between 10 and 20% fly-ash loading the removal efficiencies remained constant. The effect of contact time, pH and initial concentration was investigated. Polymer composites prepared from unmodified fly ash resulted in a higher adsorption capacity of phenols. The maximum uptake of PCP was 0.18 mg/g and that for TCP was 0.19 mg/g over a pH range of pH 3 to 5 and after contact time of 8 h. However, the adsorption capacity of 0.30 mg/g for PNP was achieved at pH 5 after a period of 10 h. Equilibrium adsorption data were evaluated using Langmuir and Freundlich adsorption isotherm models. There was no significant difference in the correlation coefficients (R2) from both models for the adsorption of PCP and TCP. However, the equilibrium adsorption data for PNP were better described by the Langmuir adsorption isotherm model. The kinetics data were analysed by pseudo-first-order and pseudo-second-order kinetic models. The pseudo-second-order kinetics model gave better correlation coefficients (> 0.9) for the adsorption of the phenols and the amount adsorbed at equilibrium was comparable to that calculated from the pseudo-second-order equation. Desorption studies were performed using NaOH solution with varying concentrations (0.1 to 0.3 M) and the studies revealed that PNP was the most difficult to be desorbed. Approximately 75% of PNP was recovered while 82% of PCP and 84% of TCP were recovered.