No description available.

Hypersol-Macronet™ polymers have been evaluated for the adsorption of organic pollutants from aqueous solution. The adsorption performance of the polymers was compared with a commercial activated carbon, Chemviron F -400. Investigation into the physical structure of the adsorbents was performed using microscopy and the adsorption of nitrogen at liquid nitrogen temperatures. A critical analysis of the adsorption isotherm data reduction models is given. The polymers possess a bimodal pore size distribution of micropores, approximately l3A in diameter, and macropores, greater than 200A. The surface functionality of the Macronets, determined by diffuse reflectance IR, 13C NMR and X-ray photoelectron spectroscopy, is presented. Elemental analysis and direct titration techniques were also investigated. Relatively high concentrations of oxygen containing functional groups were observed on the polymers, attributed to ethers, alcohols and ketones formed during polymer production. Adsorption isotherms are given for the removal of phenol and three chlorophenols substituted in the ortho, meta and para position. The greater hydrophobicity of the chlorinated phenols resulted in stronger interaction energies and larger adsorption capacities. Batch kinetic data for the above adsorbates was modelled using the homogeneous surface diffusion correlations. Analytical techniques were developed and validated for the determination of trace levels (0.1 parts per billion) of five pesticides; atrazine, simazine, isoproturon, diuron and chlorotoluron. Single and multi-component adsorption isotherms are presented for trace concentrations of pesticides in aqueous solution. Mini-column breakthrough curves are presented for MN-200 and F-400. Selectivity of the polymers for the various pesticides was explained by differences in molecular size and the hydrophobicity of the adsorbates. The primary adsorption mechanism is hydrophobic interaction enhanced by hydrogen bonding. The negative influence of natural organic matter (NOM) on the removal of pesticides was investigated using batch and column techniques. The uptake of NOM on activated carbon is much greater than that on MN-200. Total regeneration ofMN-200 using a variety of organic solvents was achieved for high and low solid phase concentrations of pesticides. Regeneration of F-400 was ineffective. The breakthrough point of a regenerated mini-column containing MN-200 was identical to the virgin polymer data. The potential commercial application of the resin for the purification of drinking water is discussed.

Two dietary polyphenols, delphinidin and resveratrol, were selected for this study; delphinidin, an anthocyanin flavonoid, was found to elicit cardioprotective properties from a pilot study and resveratrol, a stilbene flavonoid, one of the most studied of the polyphenols and was chosen as a worthy comparator. <i>In vitro</i> studies using cultured endothelial cells exposed to a variety of reactive oxygen species (ROS) were used to determine if delphinidin and resveratrol could protect these cells from oxidative damage. It was found that physiological concentrations of delphinidin protected these cells from hydroxyl-radical damage. However, resveratrol failed to show any protective effects. Oxidative stress was induced in porcine coronary artery using diethyldithiocarbamate (DETCA), an inhibitor of the superoxide dismutase (SOD). Sensitivity to nitric oxide (NO) was preserved in endothelium-denuded vessels that were pre-treated with delphinidin, but not with resveratrol. However, studies where a balloon catheter was used to induce injury to the endothelium, delphinidin pre-treatment did not preserve sensitivity to NO in these vessels. Taken together, these results suggest that delphinidin, but not resveratrol, has potential to protect the endothelium from oxidative stress by preserving/protecting NO bioavailability and by acting directly as an antioxidant or indirectly upregulating antioxidant systems.

Digitized by Kansas Correctional Industries

Typescript. / Digitized by Kansas Correctional Industries

Graduation date: 1995

Thesis (M. Sc.(Agric.))(Food Science)--University of Pretoria, 2005. / Includes summary. Includes bibliographical references). Available on the Internet via the World Wide Web.

No description available.

Thesis (M.Sc.(Food Science))--University of Pretoria, 2008. / Abstract in English. Includes bibliographical references.

Thesis (PhD.(Food Science))-University of Pretoria, 2009. / Includes English summary. Includes bibliographical references.