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Investigation of the potency of topical corticosteroids using the vasoconstrictor assay

  • Authors: Zvidzayi, Kudzayi Michael
  • Date: 2017
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/65279 , vital:28717
  • Description: Expected release date-May 2019
  • Full Text:
  • Date Issued: 2017

Assessing flood vulnerability in the Nelson Mandela Bay Metro

  • Authors: Zuze, Hillary
  • Date: 2019
  • Subjects: Floods -- South Africa -- Nelson Mandela Bay Municipality , Natural disasters Hazardous geographic environments Hazardous geographic environments -- Risk assessment , Climatic changes
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/44224 , vital:37135
  • Description: Floods are the most frequent amongst all global natural disasters at present, causing problems such as bridge collapses, fatalities, building damages and traffic delays. Between 1995 and 2015, there were approximately 3062 global flood disasters which accounted for 56% of all declared natural disasters and these affected 2.3 billion people (almost a third of the world’s population at the time) (EMDAT, 2015). The cost of damages for this period incurred for buildings and other infrastructure was at an all-time high of R23.69 (US$1.891) trillion. It is postulated through various studies that the number of urban flood events reported is increasing significantly in comparison to the previous decades (Armah et al., 2010; Lóczy, 2013; Leaning and Guha-Sapir, 2013; EMDAT, 2015; Tanoue et al., 2016; Rogger et al., 2017). Some research has also noted an increase in the number of floods per year, which has ascended to an average of 171 in this decade, from an annual average of 127 in the previous one (Dozier, 2013; Guha Sapir et al., 2016). Sources such as the Centre of Research and Epidemiological Disasters (Guha Sapir et al., 2016) recorded that from 1995 to 2015, globally, millions of homes were vulnerable to weather-related disasters, along with 130,000 health and education facilities. During this period, urban floods accounted for 98% of houses damaged and 99.9% of education and health facilities demolished by a weather-related disaster (Davies, 2017). Flooding is particularly harmful in terms of fatalities in developing countries due to inadequate flood protection and mitigation measures (Di Baldassarre et al., 2010; Dozier, 2013). Some studies attribute the high fatalities in developing countries to the inadequate disaster management strategies implemented to counter the impacts of urban flooding (Egbinola et al., 2015; Pazzi et al., 2016; Mavhura et al., 2017). Other authors have attributed the high fatalities to the sheer number of people residing in areas prone to flooding, which has been the knock-on effect of rapidly expanding cities, overwhelmed government agencies, and a pre-existing political and social system that promotes marginalisation (Collins, 2008; Aboagye, 2012). The occupation of flood-prone areas by settlements, which is a common feature in developing countries, is the major contributor to the fatalities as it involves a degree of risk. Risk is exposure to an undesired event, in this case flooding, and contributes directly to differing levels of vulnerability (Samuels, 2018). Communities have differing perceptions of flood vulnerability because of a combination of factors. These include the magnitude of the flood experienced, the number of people or the value of assets potentially affected by flooding due to location, and the lack of socioeconomic capacity to do anything to alter their vulnerability to a disaster (Hall et al., 2005; Adger, 2006; Birkmann et al., 2013; Rogger et al., 2017). Some communities acknowledge that there are people residing in flood prone areas and take measures to reduce or eliminate the risk through social, political and economic networks. In other cases, communities are able to identify their exposure to flooding but do not have the capacity to reduce the effects (Bouchard et al., 2007; Agbaoye, 2012; Musungu et al., 2012; Siyongwana, Heijne, and Tele et al., 20155).
  • Full Text:
  • Date Issued: 2019

Microbial ecology of the Buffalo River in response to water quality changes

  • Authors: Zuma, Bongumusa Msizi
  • Date: 2010
  • Subjects: Water quality -- South Africa -- Buffalo River (Eastern Cape) , Microbial ecology -- South Africa -- Buffalo River (Eastern Cape) , River Health Programme (South Africa)
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:6038 , http://hdl.handle.net/10962/d1006182 , Water quality -- South Africa -- Buffalo River (Eastern Cape) , Microbial ecology -- South Africa -- Buffalo River (Eastern Cape) , River Health Programme (South Africa)
  • Description: South Africa’s freshwater quality and quantity is declining and consequently impacting on the ecological health of these ecosystems, due to increased agricultural, urban and industrial developments. The River Health Programme (RHP) was designed for monitoring and assessing the ecological health of freshwater ecosystems in South Africa, in order to effectively manage these aquatic resources. The RHP utilises biological indicators such as in-stream biota as a structured and sensitive tool for assessing ecosystem health. Although the RHP has been widely implemented across South Africa, no attempts have been made to explore microbial ecology as a tool that could be included as one of the RHP indices. This study used selected microbial responses and water physico-chemical parameters to assess the current water quality status of the Buffalo River. This study showed that water quality impairments compounded in the urban regions of King William’s Town and Zwelitsha and also downstream of the Bridle Drift Dam. The results also showed that the lower and the upper catchments of the Buffalo River were not significantly different in terms of water physico-chemistry and microbiology, as indicated by low stress levels of an NMDS plot. Though similarities were recorded between impacted and reference sites, the results strongly showed that known impacted sites recorded the poorest water physico-chemistry, including the Yellowwoods River. However, the Laing Dam provided a buffer effect on contributions of the Yellowwoods River into the Buffalo River. Multivariate analysis showed that microbial cell counts were not influenced by water physico-chemical changes, whilst microbial activity from the water and biofilm habitats showed significant correlation levels to water physico-chemical changes. This study demonstrated that further investigations towards exploitation of microbial activity responses to water physico-chemical quality changes should be channelled towards the development of microbiological assessment index for inclusion in the RHP.
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  • Date Issued: 2010

Synthesis and evaluation of arylpyrrole-chalcone hybrids as antiplasmodial and antitrypanosomal agents

  • Authors: Zulu, Ayanda Ignatia
  • Date: 2017
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/65268 , vital:28716
  • Description: Expected release date-May 2019
  • Full Text:
  • Date Issued: 2017

Tolerance of selected riverine indigenous macroinvertebrates from the Sabie River (Mpumalanga), and Buffalo River (Eastern Cape) to complex saline kraft and textile effluents

  • Authors: Zokufa, T S
  • Date: 2001
  • Subjects: Water quality management -- South Africa -- Sabie River , Water -- South Africa -- Analysis , Water -- Toxicology -- South Africa , Mayflies -- South Africa , Freshwater invertebrates -- South Africa -- Ecology
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5787 , http://hdl.handle.net/10962/d1005475
  • Description: Whole Effluent Toxicity (WET) testing has been identified as one of the tools in the management of complex effluents in aquatic ecosystems. In South Africa, toxicity testing has not been required for regulatory purposes. Recently, the Department of Water Affairs and Forestry has adopted WET testing as a tool to evaluate the suitability of hazardous effluent for discharge into receiving environments. This has necessitated suitable procedures to be established for use in the South African situation. With the implementation of the new National Water Act (No 36 of 1998), industries have to comply with set standards to protect the aquatic environment. However, the South African Water Quality Guidelines for Aquatic Ecosystems have been set using international toxicity data, and it is not known if they are comparable with South African conditions. The aim of this study was to investigate the tolerances of selected indigenous riverine invertebrates to complex saline effluents. The study investigated the effects of kraft mill effluent to Tricorythus tinctus, a tricorythid mayfly from the Sabie River, Mpumalanga, and the effects of a textile effluent to baetid mayflies of the Buffalo River, Eastern Cape. Indigenous riverine invertebrates were chosen as test organisms, as there is no toxicity data in South Africa which could be used to evaluate the level of protection afforded by the South African Water Quality Guidelines for Aquatic Ecosystems. The use of indigenous riverine invertebrates added the challenge of variability of a wild population, and the use of a complex effluent as toxicant added the variability of effluent composition. In this study, WET testing was used to determine the dilution of whole effluents required for discharge. Hazard-based guidelines were developed for the disposal of kraft and textile effluents. The level of environmental hazard posed by different effluent concentrations was ranked, and was related to the River Health Class. This indicated effluent concentrations that may be allowed to enter the aquatic environment, e.g. 3% effluent concentration guideline for both general kraft effluent and general textile effluent for the protection of a Class A river. This approach could contribute to the use of an Environmental Risk Assessment, approach for the management of complex effluents. A number of acute 96 hour toxicity tests were conducted following an unreplicated regression design, using kraft and textile effluents as toxicants, mayfly nymphs as test organisms, and river water as diluent and control. Test organisms were sampled from unimpacted, flowing-water riffle areas, and were exposed in recirculating artificial streams (or channels) to a range of effluent concentrations. Mortality was selected as end-point and observed twice daily. The experimental results showed the variability and acute toxicity of both kraft and textile mill effluents. Baetids were more sensitive (mean LC50=16% effluent concentration) to General Textile Effluent (GTE), but less sensitive to Post Irrigation Textile Effluent (PITE). Textile effluent (PITE) held in a holding dam were therefore less variable and less toxic; suggesting that stabilization of the effluent could have contributed to reduced toxicity. Effluent composition, e.g. higher calcium levels, may also have contributed to lowering toxicity. T. tinctus was sensitive to kraft effluents, but showed less variable responses to Irrigation Kraft Effluent than General Kraft Effluent. Toxicity test data indicated that GKE, IKE and GTE should not enter the aquatic environment without treatment, as they can cause adverse effects to aquatic biota. Both kraft and textile effluents must therefore be treated before discharge. Different responses to different effluent batches were probably due to effluent variability. The use of indigenous organisms, and not a standard laboratory organism, could also have contributed to variability. A hazard-based approach could be useful, as it will provide a consistent basis for deciding on the acceptability of impacts, while allowing natural site-specific differences to be taken into account.
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  • Date Issued: 2001

Machine learning methods for calibrating radio interferometric data

  • Authors: Zitha, Simphiwe Nhlanhla
  • Date: 2019
  • Subjects: Calibration , Radio astronomy -- Data processing , Radio astronomy -- South Africa , Karoo Array Telescope (South Africa) , Radio telescopes -- South Africa , Common Astronomy Software Application (Computer software)
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/97096 , vital:31398
  • Description: The applications of machine learning have created an opportunity to deal with complex problems currently encountered in radio astronomy data processing. Calibration is one of the most important data processing steps required to produce high dynamic range images. This process involves the determination of calibration parameters, both instrumental and astronomical, to correct the collected data. Typically, astronomers use a package such as Common Astronomy Software Applications (CASA) to compute the gain solutions based on regular observations of a known calibrator source. In this work we present applications of machine learning to first generation calibration (1GC), using the KAT-7 telescope environmental and pointing sensor data recorded during observations. Applying machine learning to 1GC, as opposed to calculating the gain solutions in CASA, has shown evidence of reducing computation, as well as accurately predict the 1GC gain solutions representing the behaviour of the antenna during an observation. These methods are computationally less expensive, however they have not fully learned to generalise in predicting accurate 1GC solutions by looking at environmental and pointing sensors. We call this multi-output regression model ZCal, which is based on random forest, decision trees, extremely randomized trees and K-nearest neighbor algorithms. The prediction error obtained during the testing of our model on testing data is ≈ 0.01 < rmse < 0.09 for gain amplitude per antenna, and 0.2 rad < rmse <0.5 rad for gain phase. This shows that the instrumental parameters used to train our model more strongly correlate with gain amplitude effects than phase.
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  • Date Issued: 2019

Using the larval parasitoid, Agathis bishopi (Nixon) (Hymenoptera: Braconidae), for early detection of false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) infested fruit

  • Authors: Zimba, Kennedy Josaya
  • Date: 2015
  • Subjects: Cryptophlebia leucotreta , Citrus -- Diseases and pests -- South Africa , Pests -- Biological control -- South Africa , Cryptophlebia leucotreta -- Detection , Parasitoids -- Hosts , Braconidae
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5919 , http://hdl.handle.net/10962/d1017186
  • Description: Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is one of the major citrus pests of economic importance for South Africa’s citrus industry. It is endemic to Africa, and therefore a phytosanitary pest with zero tolerance by most export markets. The cryptic nature of T. leucotreta makes visual inspection an inefficient method for detecting neonate larvae in fruit in the packhouse. Therefore, a more accurate method for sorting infested fruit at the packhouse, particularly for newly infested fruit could ensure market access. A recent study showed that fruit infested by T. leucotreta emit a chemical profile different from that of a healthy fruit. Several studies provide evidence that parasitoids locate their hosts feeding on fruit by exploiting the novel chemical profiles produced due to host herbivory. The aim of this study was to evaluate the potential of using the naturally occurring behaviour of a larval parasitoid Agathis bishopi (Nixon) (Hymenoptera: Braconidae) for detection of T. leucotreta infested fruit, by determining which compound in infested fruit is attractive to parasitoids. Ytube olfactometer and flight-tunnel bioassays with healthy and T. leucotreta infested fruit showed a significantly stronger response of A. bishopi female parasitoids to infested fruit. Among the volatile compounds associated with T. leucotreta infested fruit, D-limonene elicited the strongest attraction to A. bishopi female parasitoids. Attraction of mated A. bishopi female parasitoids to T. leucotreta infested fruit and D-limonene significantly increased after oviposition experience. Behavioural responses of A. bishopi female parasitoids that were associated with T. leucotreta infested fruit were investigated to determine which behaviours are distinct and interpretable. Probing and oviposition behaviours were the most noticeable and were only elicited on infested fruit when parasitoids contacted T. leucotreta frass, indicating that chemical compounds in frass are short-range cues used for final host location. Since production of D-limonene by fruit is elevated due to herbivory by different pests including mechanical injury on fruit, response of A. bishopi female parasitoids to compounds in frass offers a more specific and potentially useful mechanism for development of a detection system for T. leucotreta infested fruit. Chemical analysis of T. leucotreta frass and conditioning A. bishopi parasitoids to respond behaviourally to compounds in frass is proposed.
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  • Date Issued: 2015

Characterization of the distribution of platinum group elements in sulphide ores within the Merensky Reef at Modikwa and Two Rivers Platinum Mines, Eastern Bushveld Complex, South Africa

  • Authors: Zilibokwe, Nosibulelo Julie
  • Date: 2017
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/7938 , vital:21326
  • Description: The distribution of the platinum group element (PGE), in the Merensky Reef was characterized by, first determining the occurrence of the platinum group minerals (PGM), then by establishing the PGE concentration in the base metal sulphides (BMS) associated with the PGE mineralization in the Merensky Reef from selected borehole intersections, at the Two Rivers (TRP) and Modikwa Platinum Mines in the Eastern Bushveld Complex. A mineral liberation analyser (MLA) was then used to identify the PGM phases; their silicate and base metal associations; and their grain size distribution. Electron microprobe quantitative analysis and mapping were then used to determine the compositional variation of the PGM and the PGE elemental distribution in the BMS, respectively. The study showed that the BMS including pyrrhotite, pentlandite, and chalcopyrite were the principal sulphides, where pyrrhotite was most prominent with minor quantities of pyrite. Orthopyroxene, clinopyroxene and plagioclase were the most abundant primary silicate minerals identified, while secondary silicates identified included talc, serpentine and amphibole. Platinum group minerals showed three distinct groups with respect to the mineralogical association with the PGE; (i) BMS association; (ii) chromite association; and (iii) silicate association. Of the BMS, chalcopyrite showed the most dominant association with the PGMs. All samples from both mines exhibited a wide range of PGMs, including maslovite, braggite, cooperate, laurite and PGE alloys such as ferroplatinum as well as other unidentified platinum and palladium sulphides, arsenides and bismuthides, while gold was present as electrum. The PGMs ranged in size from less than a micron to about 125 microns with an average of 20 microns. The close association of PGM with BMS along the margins of sulphides indicates that the PGMs were derived from the sulphide melt. PGE distribution in the sulphides at Modikwa showed pentlandite contained the highest concentrations of palladium (up to 379 ppm) and chalcopyrite hosting the highest rhodium concentrations (up to 793 ppm). Samples from Two Rivers revealed pentlandite as the principal host to both palladium and rhodium, with concentrations reaching up to 695 and 930 ppm, respectively. Magnetite at both Modikwa and Two Rivers showed significant rhodium content, reaching up to 982 and 930 ppm, respectively. The pyrrhotite compared to other sulphides contained all the elements found in the platinum group (PPGE), namely, platinum, palladium and rhodium, with all the platinum identified found in the pyrrhotite. The concentrations for the iridium group (IPGE) namely, iridium, osmium, and ruthenium were below the detection limit. The PGE mineralization in the stratigraphy varied within each mine. The mineralization revealed top loading in the central sector (Modikwa) and bottom loading in the southern sector (Two Rivers). The sequence of the Merensky Reef at the two sectors of the Eastern Bushveld Complex showed a remarkable similarity in their mineralogy suggesting that these two sectors were formed from the same liquid or formed simultaneously within a single magma chamber; however the PGE distribution within the stratigraphy may have been controlled by the presence of cumulate sulphides.
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  • Date Issued: 2017

An investigation into development of a stable aqeous suspension of Metronidazole Benzoate for oral use

  • Authors: Zietsman, Sharon Lynne
  • Date: 2005
  • Subjects: Metronidazole -- Testing , Excipients -- South Africa -- Testing , Rheology -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10158 , http://hdl.handle.net/10948/456 , Metronidazole -- Testing , Excipients -- South Africa -- Testing , Rheology -- South Africa
  • Description: Metronidazole is a synthetic, nitroimidazole-derivative antibacterial and antiprotozoal agent (ed. McEvoy, 2001). It has been reported that crystallization occurs in aqueous suspensions of metronidazole benzoate, a bland-tasting prodrug of metronidazole, as a result of conversion from the anhydrous to the monohydrate form, thereby compromising the stability and clinical efficacy of the substance due to the particle size growth (Hoelgaard & Moller, 1983). A generic South African based pharmaceutical company commenced formulation of an aqueous metronidazole benzoate suspension and experienced problems with crystallization that occurred in products stored at 2 to 8 °C. This study aimed to continue development of the product in order to identify a formulation that prevents formation of the hydrate form of metronidazole benzoate and the accompanying crystal growth. A variety of metronidazole benzoate suspensions were manufactured on a laboratory scale using a number of natural and synthetic suspending agents, including magnesium aluminium silicate, povidone K90, xanthan gum and Avicel® RC-591 (microcrystalline cellulose and carboxymethylcellulose sodium), over a range of concentrations. Analytical quantification methods were developed and validated, and the physicochemical properties of the raw material and finished products were fully characterized. Rheological tests were performed in order to characterize the suspension flow properties. Real-time and accelerated stability studies and a temperature cycle study were conducted in accordance with the International Conference on Harmonization (ICH) guidelines. Conversion of metronidazole benzoate to the monohydrate form took place in suspensions containing xanthan gum 0.65 percent m/v under real-time and accelerated storage conditions. The suspensions containing Avicel® RC-591 were found to be physically and chemically stable after the temperature cycle and over the 12-week period whilst stored at 25 ºC / 60 percent RH and 5 ºC. The suspensions were chemically stable whilst stored at 40 ºC / 75 percent RH but showed sedimentation at this accelerated condition. The metronidazole benzoate contained in these products remained in the anhydrous state under all storage conditions and were consequently concluded to be the most stable formulations out of all the products analyzed in the current study. The suspending agent system consisting of microcrystalline cellulose and carboxymethylcellulose sodium thus shows promise in preventing the conversion of metronidazole benzoate from the anhydrate to the monohydrate form, thereby inhibited the subsequent increase in particle size due to crystal growth.
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  • Date Issued: 2005

Testing the application of coastal altimetry in two South-Eastern African bights: the relationship between mesoscale features and chlorophyll-a, cyclonic eddies in the Indian Ocean

  • Authors: Ziegler, Lisa
  • Date: 2018
  • Subjects: Oceanography -- Remote sensing -- Indian Ocean
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/15225 , vital:28188
  • Description: Enhanced coastal altimetry, adaptive Leading-Edge Subwaveform(ALES), was used to study wo well known eddies along the southeastern African coast, namely the Delagoa Bight Lee Eddy and the Durban Lee Eddy. I address a two part problem. Firstly, how well does the application of coastal altimetry techniques behave in the coastal region? Secondly, is there a relationship between the eddies’ presence and chlorophyll-a (chl-a). Sea level anomalies (SLA) were computed from the re-tracked ALES data of two satellite missions — Envisat (used for Delagoa Bight eddy) and Jason -2 (for the Durban eddy) with geophysical corrections removed. These datasets were compared with the original satellite, 1 Hz RADS, AND AVISO gridded data. Two regions were selected to see if there was a biophysical link. A centre region of the eddy and an outside region of the eddy were taken. Results indicate that coastal altimetrywas successful in delimiting both features. ALES was less noisey and able to recover more data that were missed by the 1 Hz RADS dataset. Hovmöller plots showed the Delagoa Bight eddy to be more of a transient feature than semi-permanent, as had previously been suggested. Results from the linear model indicate a negative correlation between SLA and chl-a. This influence could be through facilitation of chl-a in the bight or just retaining chla. This is hard to elucidate without in situ data. These results show a promising indication that coastal altimetry will be a useful and reliable product to further biophysical coupling research along the coast.
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  • Date Issued: 2018

Geology, regional diamond exploration and diamond provenance of the proterozoic diamondiferous Umkondo conglomerates, Umkondo group, eastern Zimbabwe

  • Authors: Zhou, Takawira
  • Date: 2016
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/3598 , vital:20528
  • Description: The Umkondo Sedimentary Basin in eastern Zimbabwe has been studied by various individuals and organizations since 1901. Their interest had been in finding limestone and beryl and base metal deposits, especially copper, iron and uranium, but these occurrences had proved to be of no economic value (Watson, 1969). The recent discovery of placer diamonds within the Proterozoic basal conglomerates of the Umkondo Sedimentary Basin has now attracted worldwide interest in the basin’s diamond economic potential, in understanding of the geology, and the diamond provenance of the Umkondo conglomerates. The Umkondo Sedimentary Basin basal conglomerate placer deposit might narrowly be defined as a mega-placer because of its sheer large size and high grades, especially on the 70,000 hectare western margin diamond dispersion halo where alluvial diamonds are being mined. Bluck, et al., (2005, pp 213) defines a diamond mega-placer as: . . . a number of linked deposits that are a result of one or a continuous process of transportation and deposition and holds or have held at least >= 50 million carats at >= 95% gem quality, for example, the Orange-Vaal dispersal, off the Kaapvaal craton in South Africa. On craton placers are residual, and transient placers are eroded and deposited into the exit drainage, while terminal placers, the final depositories of diamonds with the highest chances of being mega-placers are deposited into terminal basins like oceans and foreland basins. Though data is limited at the moment, the Umkondo conglomerates caratage is likely to run into hundreds of millions of carats, with a diamond gem content of between twenty and twenty-five percent, as is indicated from recent diamond production data. The greater part of the Umkondo diamonds are likely to be lodged beneath the deep gravels of the Middle and Lower Save River basin, because small remnant tilted mountain blocks and inselbergs forming the caps of hills are what remains of the host conglomerate on the western margin of the Umkondo Basin. Areas to be examined in this document will be the geology; the mode of formation of the Umkondo basin and its sedimentary system; the regional kimberlite exploration around the basin; and diamond production in the Marange diamond field, in order to come up with indications of the provenance of the diamonds within the Umkondo conglomerates. The kimberlite clusters in and around the Umkondo sedimentary basin have all proved to be barren or only nominally diamondiferous and that the kimberlites are between 200Ma and 500Ma and thus much younger than the greater than 1.1Ga Umkondo diamondiferous conglomerates. Studies so far undertaken have not managed to point to the origin, or provenance, of the Umkondo or Marange diamonds, which were discovered on the western edge of the Umkondo Basin and in the east of the basin below the Chimanimani Mountains along the Haroni River. This paper is an attempt to clear up some of the misconceptions surrounding the Marange diamond deposit and to raise interest in the urgent rquirement to study and understand the Umkondo Basin and the origin of its diamonds. The only meaningful studies on diamond occurrence and diamond exploration of the basin were undertaken from 1996 to 2006 by Kimberlitic Searches Zimbabwe (Pvt) Ltd, the then Zimbabwe kimberlite exploration arm of De Beers, Zimbabwe, in their quest to find kimberlites, which were thought to be related to the Umkondo alluvial diamond deposit. As will be shown in the following chapters, many of the discovered kimberlites range from very low grade to non-diamondiferous, and are much younger than the Umkondo conglomerates, whose diamonds are in turn a great deal older. Thus the basic question concerning the origin or provenance of the Umkondo placer diamonds still remains unresolved. Because of the sheer size of the basin, modern, wide-area-coverage, geophysical exploration methods become appropriate to effectively generate diamond potential targets for further examination. This document will attempt to collate various data available to paint a true picture of the state of exploration within the Umkondo Basin.
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  • Date Issued: 2016

The reactions of ruthenium (ii) polypyridyl complexes

  • Authors: Zheng, Sipeng
  • Date: 2009
  • Subjects: Ruthenium , Ruthenium compounds , Chemical reactions
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10374 , http://hdl.handle.net/10948/1089 , Ruthenium , Ruthenium compounds , Chemical reactions
  • Description: Ruthenium (II) polypyridine complexes in general have been extensively studied because of their unique redox and photochemical properties. A typical example of such complexes is tris(2,2’-bipyridyl) ruthenium (II). In this study, this complex was synthesized and then characterized using electronic spectroscopy and cyclic voltammetry. It was also shown that the ruthenium concentration could be accurately determined using ICP-MS. It was found that the complex is very stable in various chemical environments. It was observed from spectrophotometric investigations that persulphate and lead dioxide easily oxidize Ru(bpy)3 2+ to Ru(bpy)3 3+ in the presence of heat and H2SO4, respectively. It was also observed that the oxidation between Ru(bpy)3 2+ and cerium (IV) occurred at approximately 3:2 [Ce(IV)]/[Ru(II)] mole ratio. The resultant Ru(bpy)3 3+ solution was unstable in the presence of light and recovery of Ru(bpy)3 2+ occurred gradually. The regeneration of Ru(bpy)3 2+ from Ru(bpy)3 3+ was found to be a multistep process, which appears to involve the formation of an intermediate species. The following reaction model was found to best explain the kinetic data obtained: Ru(bpy)3 2+ + Ce(IV) → Ru(bpy)3 3+ Ru(bpy)3 3+ → Ru(bpy)3 2+ Ru(bpy)3 3+ → Ru* intermediate Ru* intermediate → Ru(bpy)3 2+ Theoretical rate constants were also calculated for the same process under the experimental conditions. The comparison between the experimental and theoretical results gave good agreement. In addition, the factors that influence the rate of the regeneration of Ru(bpy)3 2+ from Ru(bpy)3 3+ were also discussed.
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  • Date Issued: 2009

A comparative analysis of Java and .NET mobile development environments for supporting mobile services

  • Authors: Zhao, Xiaogeng
  • Date: 2003 , 2013-05-23
  • Subjects: Microsoft .NET , Java (Computer program language) , Mobile computing , Wireless communication systems
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4578 , http://hdl.handle.net/10962/d1003064 , Microsoft .NET , Java (Computer program language) , Mobile computing , Wireless communication systems
  • Description: With the rapid development of wireless technologies, traditional mobile devices, such as pagers and cellular phones, have evolved from a purely communications and messaging-oriented medium to one that supports mobile data communication in general and acts as an application platform. As shown in a recent survey conducted by MDA, easy access to the present-day wireless Internet has resulted in mobile devices gaining more and more attention and popularity. The growth of and demand for mobile Web applications is expected to increase rapidly in the near future, as a range of software companies and mobile device manufacturers release increasingly accessible tools for creating mobile Web application and services. From a variety of possible development environments of this kind, the author has selected and examined two leading contenders, the J2ME and the Microsoft .NET mobile Web application development environments. This document reports the product life cycle of pilot mobile web applications, designed and implemented in each host environment in tum. A feature-by-feature investigation and comparison of the J2ME and .NET environments was carried out, covering the range of issues necessary for a complete mobile Web application development life cycle. The resulting analysis addresses features and efficiencies of the application development environment and the target deployment environment, the degree to which the resultant services are compatible on a variety of platforms, and the ease with which applications can be designed to be extensible. The thesis offers an objective evaluation of the J2ME and the .NET mobile development environments, which highlights their strengths and weaknesses, and suggests guidelines for designing, creating, and deploying high quality mobile Web applications. The research uncovers no clear winner across all categories assessed. J2ME currently favours situations in which bandwidth is limited and client side processing power is relatively sufficient, it exerts the processing power of mobile devices over distributed network environments. .NET requires a less constrained network throughput, but performs adequately on clients with more limited processing power, supports a more diverse target platform range, and offers a more efficient, in terms of development time, development environment. Both technologies are likely to receive significant user support for some time. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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  • Date Issued: 2003

Development framework in the Mdantsane central business district

  • Authors: Zenani, Pumzile
  • Date: 2020
  • Subjects: Central business district -- South Africa -- East London , City planning -- South Africa -- East London Public utilities -- Management
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/47292 , vital:39840
  • Description: The study sought to investigate a development performance and management of Mdantsane CBD. The performance measurement framework may enhance the chances of economic success in the CBD. The study was conducted by means of a review of related literature and by conducting an empirical study. The empirical study was conducted using a quantitative approach by distributing research questionnaires to members falling within the sample population. The primary objective of the study was to develop a framework for perceived enhanced development for the Mdantsane CBD. A descriptive survey was conducted among the population within Mdantsane Township. The framework includes strategic factors of planning during apartheid era, reviewed strategic planning during democratic era and it provides an understanding of the current spatial and physical characteristics of the study area. Key issues such as spatial planning, infrastructure, environment, health, safety, economics and management of the CBD were also identified. Findings were based on the survey’s results from the community members. Findings suggest that the following variables: strategic factors (democratic); spatial development framework and infrastructure implementation; budget alignment; PESTEL factors (Political, Economic, Social, Technological, Ecological and Legal); environmental health and safety, transport and transport engineering, project management (body of knowledge) and the National Development Plan positively influenced the perceived enhanced development of Mdantsane CBD. All these variables were identified in the empirical framework affecting the perceived enhanced development of Mdantsane CBD. This study may contribute to the South African spatial and development planning body of knowledge by addressing factors which are faced by planners in development of the settlements.
  • Full Text:
  • Date Issued: 2020

A mathematical study on optimal prevention and control strategies for tuberculosis: case study for Port Elizabeth, South Africa

  • Authors: Zembe, Pumelela Vincent
  • Date: 2016
  • Subjects: Tuberculosis -- South Africa -- Port Elizabeth -- Prevention Tuberculosis -- Mathematical models , Tuberculosis -- Case studies
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/12823 , vital:27124
  • Description: In this treatise a SEIR model for the transmission of tuberculosis was proposed. It assumes that the latent infected individuals progress to active tuberculosis through endogenous reactivation and exogenous re-infection and that the individuals who have recovered from the disease through treatment are not immune to tuberculosis re-infection. While most features of the original model were kept, the model was modified to incorporate two control measures in the form of post-exposure tuberculosis prophylaxis for the treatment of latent individuals and tuberculosis therapeutics for the treatmentof individuals with active tuberculosis. Mathematical analysis of the modelwas done under the assumption that the two control measures are positiveconstants. The disease-free equilibrium point was locally asymptotically stable when the basic reproduction number was less than unity and unstable when this epidemic threshold exceeds unity. An optimal control problem was formulated and the necessary conditions for optimality were derived.The numerical results based on data from Port Elizabeth suggest that using both forms of control measures simultaneously is more effective in reducing the total number of infected individuals than applying single controls separately.
  • Full Text:
  • Date Issued: 2016

The influence of aspirations on changing livelihood strategies in rural households of Ndabakazi villages in the Eastern Cape

  • Authors: Zantsi, Siphe
  • Date: 2016
  • Subjects: Households -- Economic aspects -- South Africa -- Eastern Cape Rural development projects -- South Africa -- Eastern Cape Sustainable development -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10353/5653 , vital:29357
  • Description: The objective of this study is to explore the role of aspirations on changing livelihood strategies of rural households of Ndabakazi villages in the Eastern Cape. A sample of 80 respondents was chosen randomly for the household survey and semi-structured questionnaires were used to collect the data. Focus group discussions were also used to supplement the household survey. The data was descriptively analysed using a triangulation method. The findings show that social grants, mainly pensions and non-farm employment, and child support grants are the major sources of income. The majority of the households own five hectares of land and more, in which they grow crops only in gardens adjacent to their homes. However, 29 percent do not produce any crops at all. Farming contributes a small portion to the household income. The choice of farming is more powerful than the external factors. Interest in farming is minimal and can be related to the declining farming activities; therefore, household aspirations have an influence on changing livelihood aspirations. In the case of the rural areas of Ndabakazi – as indeed in many other parts of South Africa - policies of rural development mostly take a top-down approach; as a result most of these policies do not become effective in achieving the intended outcome. Development practitioners should incorporate beneficiaries when planning so as to tailor the development initiatives with the aspirations of local people for them to be effect and achieve intended goals thus a bottom-up approach. The notion that rural household farming activities have declined because they lack inputs, farming implements other necessary support is not always true. Some households are not interested in farming and they cannot be forced.
  • Full Text:
  • Date Issued: 2016

Reactivity of Rhenium (iii) and Rhenium (V) with multidentate NN-and no-donor ligands

  • Authors: Yumata, Nonzaliseko Christine
  • Date: 2010
  • Subjects: Rhenium , Ligands
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10373 , http://hdl.handle.net/10948/1085 , Rhenium , Ligands
  • Description: The reaction of the potentially tridentate Schiff-base chelate Hhaep [Haep = N’-(1- (2-hydroxyphenyl)ethylidene)benzohydrazide] with [ReCl3(benzil)(PPh3)] and trans-[ReOCl3(PPh3)2] produced the neutral oxorhenium(V) complexes cis- [ReOCl2(mep)] [Hmep = 2-(1-iminoethyl)phenol] and cis-[ReOCI2(meb)(PPh3)] [Hmeb = N’-(propan-2-ylidene)benzohydrazide] in ethanol and acetone respectively. In both reactions the Hhaep molecule cleaves to give different coordinated bidentate NO-donor chelates coordinated to the rhenium(V) centers. The X-ray studies reveal that mep is present as a bidentate, monoanionic Schiffbase coordinating through the neutral imino nitrogen and the deprotonated phenolate oxygen in cis-[ReOCl2(mep)]. The bond distances and angles in cis- [ReOCI2(meb)(PPh3)] confirm that meb coordinates to the metal in the enolate form. The distorted octahedral complex fac-[ReCl3(dpa)(PPh3)] was prepared by the reaction of trans-[ReCl3(MeCN)(PPh3)2] with a twofold molar excess of dpa in acetonitrile under a nitrogen atmosphere. The compound dpa.HCl.2H2O was obtained as a by-product in the reaction of dpa with trans-[ReCI3(MeCN)(PPh3)2] in acetonitrile. The reaction of trans-[ReCl3(MeCN)(PPh3)2] with a twofold molar excess of 6- amino-3-methyl-1-phenyl-4-azahept-2-ene-1-one (Hamp) in acetonitrile led to the isolation of cis-[ReCl2(bat)(PPh3)2]. On complexation to the metal center Hamp decomposed to give the coordinated benzoylacetone (bat). Bat is present as a monoanionic bidentate chelate. The complexes [ReVOCI(had)] and [ReIVCl(had)(PPh3)](ReO4) were prepared from the reaction of trans-[ReCl3(MeCN)(PPh3)2] with N,N-bis((2-hydroxybenzyl)-2- aminoethyl)dimethylamine (H2had) in ethanol under various reaction conditions. The treatment of [ReCl3(benzil)(PPh3)] with 2-[((2- pyridinylmethyl)amino)methyl]phenol (Hham) in a 2:1 molar ratio in acetonitrile led to the isolation of the hydrogen-bonded dimer [ReOCl2(ham)]2. The distorted octahedral complex [ReOCl(hap)] [H2hap = N,N-bis(2- hydroxybenzyl)aminomethylpyridine] was prepared from the reaction of trans- [ReCl3(MeCN)(PPh3)2] with a twofold molar excess of H2hap in acetonitrile. The X-ray crystal structure analysis shows that the chloride is coordinated trans to the tripodal tertiary amino nitrogen, with a phenolate oxygen trans to the oxo oxygen.
  • Full Text:
  • Date Issued: 2010

Use of recycled rubber tyres as an alternative ingredient in cementitious building materials

  • Authors: Yuill, Robert Mark
  • Date: 2018
  • Subjects: Building materials , Building materials -- Environmental aspects Sustainable construction Recycled products
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/29783 , vital:30777
  • Description: The need to incorporate recycled materials in building products is becoming more important than ever before. There is an abundance of waste rubber tyres which in turn results in a waste management issue. The use of waste rubber tyres in cementitious building material provides a possible solution to the problem (Kathomi, 2009:10). Previous research has shown the introduction of recycled rubber tyre crumb can improve the durability, thermal and acoustic performance in residential and commercial buildings. This could result in lives of dwellers in concrete block buildings in South Africa improving due to these characteristics whilst potentially creating a cost-effective, sustainable building material. A grading analysis, loose and compacted bulk densities and relative densities were determined to provide a mix design. Three tests were conducted for this study namely compressive strength, fire and thermal performance and acoustic performance. The testing was conducted on 100mmx100mm cubes at varying rubber replacement percentages. The replacement values were 10%, 20% and 30% tested against a control of ordinary concrete. The waste rubber crumb was a replacement for sand. The research of this study showed 20 % decrease of compression strength at 10 % rubber replacement compared to the control, 55 % decrease at 20 % rubber replacement and 75% decrease at 30 % rubber replacement. The thermal performance test showed a 24 % lower temperature for 10 % rubber replacement compared to the control, 39 % lower temperature at 20 % rubber replacement and 52 % lower temperature at 30 % rubber replacement. All rubber replacement % samples and the control performed adequately in the flame resistance test. The smoke density test showed that all rubber replacement % samples did not release a quantity of smoke which would be deemed dangerous. The acoustic performance test showed the values at 10% rubber replacement was 6 % lower; at 20% rubber replacement; 4% lower and at 30% rubber replacement 14 % lower. Based on these results, the acoustic performance regarding transmission increases with a rubber replacement % higher than 20 %.
  • Full Text:
  • Date Issued: 2018

Secondary effects of oral contraceptives

  • Authors: Yuen, E Ho
  • Date: 1978
  • Subjects: Oral contraceptives , Oral contraceptives -- Side effects
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3847 , http://hdl.handle.net/10962/d1012296
  • Description: Norethynodrel, a common progestin in oral contraceptives, produces in female rats several significant physiological, cytological and biochemical changes at dose levels of 1 mg and 20 mg per kg: 1) a relative increase in liver mass 2) modification of appearance and extent of the endoplasmic reticulum 3) augmentation of the protein content of the liver 4) increase of the level of cytochrome P- 450 in the liver as determined by : a) difference spectroscopy b) increases in biotransformation of aniline and aminopyrine in vitro and c) reduction of sleeping times of rats dosed with phenobarbital The significance of these findings becomes evident when it is realized that norethynodrel affects and is affected by the same enzyme system which oxidizes medicaments in general in the body: induction of cytochrome P-450 by administration of norethynodrel may interfere with the action of other drugs . Ethinyl estradiol alone showed none of the inductive effects. At high dose levels (20 mg per kg) both norethynodrel and ethinyl estradiol caused a marked inhibition of growth of the animals, producing a net loss of body mass over the 30- day experimental period. Electron micrographic evidence implies that there is also a lowering of glycogen content and a chemical change in the lipids of adrenocortical and liver cells accompanying the use of these agents.
  • Full Text:
  • Date Issued: 1978

The spatial evolution of the chemotaxis proteins of the Bacillus subtilis group

  • Authors: Yssel, Anna Elizabeth Johanna
  • Date: 2011
  • Subjects: Chemotaxis , Bacillus subtilis , Bacillus (Bacteria) , Homology (Biology) , Plants -- Microbiology
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4027 , http://hdl.handle.net/10962/d1004087 , Chemotaxis , Bacillus subtilis , Bacillus (Bacteria) , Homology (Biology) , Plants -- Microbiology
  • Description: The aim of this work was to study spatial evolution of the chemotaxis proteins of a group of plant-associated soil-dwelling bacteria vernacularly referred to as the B. subtilis group. This was achieved by creating homology models for the chemotaxis proteins if a suitable template was available, and by analysing the selective forces (positive, purifying or neutral) acting upon the chemotaxis proteins. Chemotaxis is the phenomenon in which bacteria direct their movement towards more favourable conditions, and is critical for processes such as obtaining nutrients, escaping toxic compounds, host colonization and bio-film formation. Members of the B. subtilis group exhibit different preferences for certain host plants, and it is therefore feasible that their chemotactic machinery are fine-tuned to respond optimally to the conditions of the various niches that the strains inhabit. Homology models were inferred for the plant growth promoting B. amyloliquefaciens FZB42 proteins CheB, CheC, CheD, CheR, CheW and CheY. The interactions between: CheC-CheD, the P1 and P2 domains of CheA with CheY and CheB, and the P4 and P5 domains of CheA with CheW were also modelled. The hydrophobic interactions contributing to intra- and inter-protein contacts were analysed. The models of the interactions between CheB and the various domains of CheA are of particular interest, because to date no structures have been solved that show an interaction between a histidine kinase (such as CheA) and a multidomain response regulator (such as CheB). Furthermore, evidence that phospho-CheB may inhibit the formation of phospho-CheY by competitively binding to the P2 domain of CheA is also presented. Proteins were analysed to determine if individual amino acid sites are under positive, neutral or purifying selection. The Methyl Accepting Chemotaxis Proteins (MCPs), CheA and CheV were also analyzed, but due to a lack of suitable templates, no homology models were constructed. Site-specific positive and purifying selection were estimated by comparing the ratios of non-synonymous to synonymous substitutions at each site in the sequences for the chemotaxis proteins as well as for the receptors McpA, McpB, and McpC. Homology models were coloured according to intensity of selective forces. It was found that the chemotaxis proteins of member of the B. subtilis group are under strong evolutionary constraints, hence it is unlikely that positive selection in these proteins are responsible for the differences in habitat preference that these organism exhibit.
  • Full Text:
  • Date Issued: 2011
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