Submitted in fulfilment of the Degree of Master of Engineering in Chemical Engineering, Durban University of Technology, Durban, South Africa, 2017. / A pertinent issue facing the materials industry is that of the lifespan of materials when exposed to certain solvents/ environments. Limitations to the applications of materials require further research into understanding their failure mechanisms and how such problems can be addressed in terms of re-engineering such materials to be more durable. PVC and HDPE are two common polymers used extensively in industrial applications. Gibbs ensemble Monte Carlo simulations were used to simulate systems of PVC and HDPE with methanol, respectively. The temperatures used in this work were 25, 30 and 40 oC and all systems were at atmospheric pressure. Laboratory tests were used to complement simulations for analysis purposes. Results showed an increase in temperature resulted in a decrease in the overall clustering in both polymers although PVC displayed a greater decrease than HDPE. Linear clustering dominated over other forms of clustering with increases in temperature, with dimers being the most prevalent topology type. The results of this study suggest that the presence of chlorine atoms in PVC may not directly affect clustering of absorbed methanol, and their effect may instead be indirect by means of altering the accessible free volume within the polymer. Swelling was also investigated in the simulated systems and it was found that PVC displayed a greater degree of swelling than HDPE despite its lower rate of clustering. The effect of cluster radius on the cluster analysis was also considered. / M

Analog and digital structures can be written into thin surface layers of semiconductors by using focused ion beams of submicron dimensions. By inducing the phase transition from the crystalline (c) to the amorphous state (a) optical contrast is generated between areas of different exposure. The aim of this study was to investigate the properties of diamond as a high-density optical recording medium and to determine the corresponding irradiation parameters. To this end, single crystals of diamond were irradiated with self-ions of 75 key energy with fluences between F=0.3-l0xlO15 C/cm2 at about 100 K. The radiation damage, persisting after annealing treatments between 300-1700 K, was studied by Raman measurements, monitoring changes in the atomic bonding arrangements. Since the scattering cross-section of C sp2 bonds is 50x that of C sp3 bonds, this is an extremely sensitive technique in detecting changes in the initially purely sp3 state. The position and linewidth of the characteristic first-order phonon of crystalline diamond at 1332 cm-l reflect crystallinity and stress level, while bands between 1350-1700 cm-l indicate disorder. In utilizing the microscopic resolution of a Raman facility additional information was obtained on the spatial variation of the damage level. The optimum annealing temperature was found to be 1500 K. For F > 3xlO15C/cm2, the damage was irreversible, for F = 3xlO15C/cm2 the damage was only partly repaired after annealing at 1500 K and, for F < 3xlO15C/ cm2, the crystalline/amorphous contrast was reversible. For F < lxl015C/ cm2 Raman spectroscopy was not sensitive enough to detect the incurred damage. Infrared spectroscopy was used to classify the diamond samples according to type. / Dissertation (MSc (Chemistry))--University of Pretoria, 2006. / Chemistry / unrestricted

The synthesis of proteins bearing unnatural amino acids has the potential to enhance and elucidate many processes in biochemistry and molecular biology. There are two primary methods for site specific unnatural amino acid incorporation, both of which use the cell’s native protein translating machinery: in vitro chemical acylation of suppressor tRNAs and the use of orthogonal amino acyl tRNA synthetases. Total chemical synthesis is theoretically possible, but current methods severely limit the maximum size of the product protein. In vivo orthogonal synthetase methods suffer from the high cost of the unnatural amino acid. In this thesis I sought to address this limitation by increasing cell density, first in shake flasks and then in a bioreactor in order to increase the yield of protein per amount of unnatural amino acid used. In a parallel project, I used the in vitro chemical acylation system to incorporate several unnatural amino acids, key among them the fluorophore BODIPYFL, with the aim of producing site specifically fluorescently labeled protein for single molecule FRET studies. I demonstrated successful incorporation of these amino acids into the trial protein GFP, although incorporation was not demonstrated in the final target, FEN1. This also served to confirm the effectiveness of a new procedure developed for chemical acylation.

Polymeric materials are widely used in diverse applications. However, a major weakness in the majority of the thermoplastic polymers is their lack of ability to resist fire. Most of the chemicals and additives currently used to improve fire retardancy have deleterious effects on the environment. This research focuses on developing an environmentally safe and effective fire-retardant system for high density polyethylene (HDPE), using cellulose nanocrystals (CNCs) and zinc oxide (ZnO). The effect of CNCs coated with nano ZnO has been investigated for improving the fire resistance properties of the HDPE. Improved dispersion of CNCs into HDPE matrix was achieved by employing maleic anhydride as a coupling agent. It was found that addition of CNCs-ZnO can introduce a reasonable level of flame retardancy in HDPE matrix in addition to improving the maximum tensile strength and elongation at break.

The electricity generation composition in the South African national grid has changed in recent years from mostly thermal generation to a combination of thermal generation plants and a variety of plants owned and operated by Renewable Energy Independent Power Producers (REIPPs). The need arises to determine whether the existing planning and design guidelines of distribution networks in South Africa are sufficient in terms of equipment specifications and general sizing and rating principles, used during the network planning process, under increasing penetration levels of embedded generation. The correlation between increases in embedded generation penetration levels and voltage variation, unbalance and harmonic emissions are determined by simulating various operating scenarios of varying load and short circuit level for penetration levels of 10%, 25% and 40%. The existing distribution grid planning standard NRS 097 allows for a 25% penetration level where several consumers share one feeder or distribution transformer. Some of the limits contained in the South African power quality standards NRS 048 and the distribution grid planning guidelines NRS 097 are exceeded when penetration levels of grid connected Photovoltaic (PV) generation exceeds certain levels. - Switching embedded generation in or out of service does not cause voltage variations that exceed the planning limit of 3% at the shared feeder. - Voltage unbalance due to embedded generation connected to the same phase does not cause the compatibility limit of 3% to be exceeded. - Current unbalance should be monitored as it is very likely that equipment ratings may be exceeded when the integration of embedded generation is not coordinated. - Voltage harmonic limits of the odd harmonic which are multiples of 3 are exceeded. - Current harmonic planning limits of several harmonics are exceeded for penetration levels of 25%. The criteria and limits contained in the standards and guidelines relating to current unbalance and harmonic currents should be reviewed to ensure that future grids with high penetration levels of embedded generation can withstand the inherent power quality challenges without having an adverse effect on distribution equipment. Distribution transformers can age faster when they are subjected to harmonic currents and voltages exceeding their design parameters [12]. The distribution transformer isolates the Medium Voltage (MV) distribution grid from the 400 V residential grid. The voltage harmonics and voltage unbalance on the Low Voltage (LV) grid therefore do not permeate to the MV grid. Proposed future work includes translating the qualitative suggestions made in this dissertation into quantitative terms that can be included in revisions of the distribution equipment standards and grid planning guidelines. / Dissertation (MEng)--University of Pretoria, 2017. / Electrical, Electronic and Computer Engineering / MEng / Unrestricted

Magister Pharmaceuticae - MPharm / Cardiovascular diseases (CVDs) such as ischaemic heart diseases, heart failure and stroke remain a major cause of death globally. Various deep-rooted factors influence CVD development; these include but are not limited to elevated blood lipids, high blood pressure, obesity and diabetes. A considerable number of proteins are involved directly and indirectly in the transport, maintenance and elimination of plasma lipids, including high and low-density lipoprotein cholesterol (HDL-C and LDL-C). There are several mechanisms involved in the removal of LDL particles from systemic circulation. One such mechanism is associated with the gene that encodes proprotein convertase subtilisin/kexin type 9 (PCSK9), which has become an exciting therapeutic target for the reduction of residual risk of CVDs. Currently, statins are the mainstay treatment to reduce LDL-C, and a need exists to further develop more effective LDL-C-lowering drugs that might supplement statins.

Quality play is fundamental to the healthy development of a child. Children living in high-density residential areas in Pretoria are deprived of necessary play experiences, due to the nature of the existing playgrounds. This dissertation investigates how a playscape (natural playground) can be designed in such a way as to facilitate the social, emotional, cognitive and physical development of children. The research argues that quality play is possible when children have loose parts to play with, and are able to manipulate their environment. Playing in more natural areas offers a host of physical and psychological health benefits for children. A playscape is therefore proposed in the high-density residential area of Sunnyside in Pretoria along the Walker Spruit, to serve the play needs of the children in the area, incorporating a toy library and other economic initiatives. The design solution aims at creating a safe park which would be used by all members of the public, not only children. The proposal shows that employing natural materials in a play area could provide healthy, stimulating play opportunities for children. / Dissertation (ML(Prof))--University of Pretoria, 2011. / Architecture / unrestricted

The Coalfields of the Republic of South Africa (RSA) discharge approximately 360 Ml d-1 of mine impacted water, referred to as Acid Mine Drainage (AMD), requiring neutralization to reduce risk to the environment. High Density Sludge Process (HDSP) is commonly used to treat AMD, and neutralization is typically with either limestone (CaCO3) alone to save costs, or with limestone plus hydrated lime (Ca(OH)2) to effectively reduce acidity and improve metal removal. This water either needs to be further treated to reduce metal content and salinity, or a potential option is to use it for irrigation. Since, it would be possible to lime a soil and irrigate directly with AMD as this would be potentially easy to manage than an HDS plant and save costs on the plant. The treatment process produces a circum-neutral mine water that requires further treatment with reverse osmosis to potable water. Suitability of these waters for irrigation can be evaluated with the Irrigation Water Quality Decision Support System (IWQDSS) for RSA. This study therefore evaluated the two specific mine impacted waters for irrigation. The treatment process also generates gypseous products, referred to as High Density Sludges (HDS), which may be classified as hazardous, based on metal (Mn, Ni, Pb) content, in which case expensive waste storage is required. However, these sludges may have some value for use in agriculture since they are gypseous. Four out of six sludges considered in this study were investigated for potential use in agriculture since their chemical characteristics depend on the quality of AMD and the treatment process. If hazardous, a potential approach was to add phosphate to them since this has been shown before to immobilize metals. The influence of phosphate on the availability of elements in sludges was therefore investigated. Hence, the objectives were to investigate; 1) the fitness for use of AMD and circum-neutral mine impacted waters for irrigation with IWQDSS, 2) chemical and physical properties of sludges, 3) hazardous status of sludges using the RSA waste classification system including those of the United States Environmental Protection Agency (USEPA), Australia, China and Canada, 4) phosphate potential in reducing the solubility of metals in sludges, 5) crop and soil response to sludges applied on their own as soil amendments and when co-applied with phosphate, 6) the influence of phosphate co-applied with sludges to the phyto-availability and uptake of Ni and Pb, including food safety. Assessment with IWQDSS showed that both waters were not fit for irrigation because of some quality issues. However, AMD can only be used if the soil can be limed and used as a reactor and further showed that there would be no leaf scorching. The circum-neutral mine water was found to be not effectively saline. Micro irrigation should not be considered for these waters due to suspended solids they contain. Four of the six sludges assessed for agricultural use included; a Ferriferrous Gypseous sludge (GypFeMnNi) with Fe, Mn and Ni from a limestone process, and three others generated from three stages of a limestone plus hydrated lime process; Ferriferrous Gypseous sludge with Mn (GypFeMn), Gypseous sludge with Brucite (GypB) and Gypseous sludge (Gyp) with Fe removed. Chemically, the sludges, GypFeMn, GypB and Gyp showed pH values of 8.2, 9.4 and 9.5, exhibiting CaCO3 equivalents (CCE) of 510, 601, 617 mg kg-1. The sludge, GypFeMnNi, had a pH of 5.5 and a CCE of 250 mg kg-1. All four sludges showed to be largely gypsum (72 – 95 %) composed. Physically, all sludges had particle sizes falling between 0.4 to 906 µm. These four sludges were further considered for hazardous assessment, including two sludges; GypFeNi and GypFe from a different limestone process. USEPA rated all six sludges non-hazardous, while Canada and China found GypFeNi as hazardous based on Ni solubility, Australia found GypFeMn as hazardous. RSA considered GypFeMnNi and GypFeNi hazardous, based on Ni and Mn solubility. Limestone was therefore less effective in reducing the solubility of Ni and Mn in the sludges than limestone plus hydrated lime. The sludges found hazardous (GypFeMnNi and GypFeMn) were then phosphated to reduce Mn and Ni solubility. Their solubility was reduced in both sludges. GypFeMnNi and Gyp, were further considered for use as soil amendments and selection was based on differences in the treatments that generates them. A pot trial was conducted where both were applied at 10 and 20 t ha-1 each to a soil with pH 3.75 and co-applied with phosphate at application rates of 40 and 100 kg ha-1. Maize (Zea mays) was planted and harvested at physiological maturity. Effect on soil showed that both sludges marginally increased pH, with Gyp at 20 t ha-1 and 100 kg ha-1 P increasing it the most by 0.46 units. This pH was still not suitable for plant growth. The sludge, Gyp increased soil salinity the most from 7.8 mS m-1 to 728 mS m-1, suitable only for salt tolerant crops. The effect on the maize showed that both sludges on their own marginally increased plant height and biomass, but co-application with phosphate increased these parameters. Grain was present only in treatments where phosphate was co-applied with either sludge. The highest grain yield was obtained when Gyp was applied at 20 t ha-1 with 100 kg ha-1 P. With food safety, Ni and Pb concentrations in the grain were below thresholds regarded as toxic. It is suggested that irrigation with AMD may be possible on condition that the soil is limed and used as treatment reactor to prevent the reduction of soil pH. Also, micro irrigation systems are to be avoided when irrigating with AMD and circum-neutral mine impacted waters because they contain suspended solids that can clog them. Irrigation should be with an appropriate leaching fraction to reduce accumulation of salts in the soil profile. It can also be concluded that two of the sludges from a limestone only HDSP were found to be hazardous by the RSA waste classification system due to Mn and Ni solubility., whereas international systems felt these materials were non-hazardous. The RSA waste classification system was found to be overly cautious compared to international systems and should be revisited. Sludges from HDSP can rather be used as soil amendments instead of being classified hazardous and destined to expensive waste management sites. If certain trace elements are excessively available, the study demonstrated that phosphating reduces mobility and toxicity, ensuring the safety of produce from soils treated with HDS. Keywords: AMD, HDS, Circum-neutral mine water, waste classification, amendment / Thesis (PhD (Soil Science)--University of Pretoria, 2020. / WRC / Plant Production and Soil Science / PhD (Soil Science) / Unrestricted

Les glycosaminoglycanes (GAGs) sont des polymères de sucres linéaires, présents chez tous les animaux. Certaines bactéries pathogènes synthétisent également des polysaccharides identiques ou très similaires aux GAGs humains. Cette thèse a porté en particulier sur la synthèse de la chondroïtine sulfate et de l’héparosan qui font partie de cette famille de polysaccharides. L’intérêt pour ces deux GAGs est grandissant dans l’industrie pharmaceutique du fait des nombreuses applications médicales qu’ils pourraient permettre. La chondroïtine sulfate est d’ores et déjà extraite de tissus animaux ce qui peut engendrer des problèmes sanitaires, notamment des contaminations virales ou aux prions. En revanche, le procédé de production pour l’héparosan reste à mettre en place. Il est donc nécessaire de développer des procédés de production pour ces deux molécules. La synthèse enzymatique est une voie particulièrement prometteuse pour la production de la chondroïtine sulfate et de l’héparosan, et a fait l’objet de ce travail de thèse. / Glycosaminoglycans (GAGs) are long linear polysaccharide chains, found in all animals. Some pathogenic bacteria also synthesize polysaccharides identical or similar to human GAGs. This thesis deals with chondroitin sulfate and heparosan syntheses, members of the GAGs family. There is a growing interest in these two GAGs in the pharmaceutical industry due to numerous potential applications they offer. Chondroitin sulfate is currently extracted from animal tissues which can lead to sanitary problems such as viral or prion contaminations. On the other hand, a production process still needs to be developed for heparosan. Therefore, it is necessary to develop new methods for the production of these two polymers. Enzymatic synthesis, which is a promising alternative for the production of chondroitin sulfate and heparosan, was the subject of this thesis.

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