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Development and validation of in-process control test kits for biodiesel production

  • Authors: Fibi, Pumza Oscarine
  • Date: 2013
  • Subjects: Biodiesel fuels -- South Africa , Biomass energy -- South Africa
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: vital:10416 , http://hdl.handle.net/10948/d1012645 , Biodiesel fuels -- South Africa , Biomass energy -- South Africa
  • Description: The production of biodiesel from vegetable oils is not a new technology; it has been around since the 1950’s and both the research in terms of the different feedstock that can be used and the production of biodiesel has since been gaining momentum as there needs to be a new, sustainable and domestic alternative to petroleum fuels. These petroleum fuels pose enormous threats to the environment and therefore need to be replaced as they are mostly contributing to climate change and global warming not to mention the frequent price hikes which are crippling the South African economy. Biodiesel production using vegetable oils seems to be and is the future and a law has recently been passed which sanctions the production of biofuel locally.[1] South African fuel producers will instigate obligatory blending of fossil fuel with biofuel as the country moves to encourage investment in its biofuels sector. The production of biodiesel locally and the blending of biodiesel with other petroleum products will reduce the country’s dependence on imported fuel. The already established petrochemical companies like BP, Sasol and Engine are therefore mandated to purchase these biofuels if and when the biofuels meet the required South African National Standard (SANS) 1935 requirements. This is then where the challenge comes as most of these growing biofuel companies cannot afford to purchase testing equipment.The growing companiesthen discover upon completion of the biofuel manufacturing process that their product does not meet the required standard specification. The failure translates to a financial loss as the final product can possibly not be reworked. The aim of the project is then to assist these companies who are manufacturing biofuel, by providing them with in-house biofuel process methods which will allow for early detection, should there be a need to redo a step in the process and not wait until the completion of the production process. These in-house process-testing methods will range from pH determination, titration tests which will determine the soap content and the percentage free fatty acid content, water determination, density and visual testing. It is not cost-effective for these biodiesel manufacturers to send their samples for outsource testing as evidently the results obtained would be out of specification hence the need to provide these biodiesel manufacturers with in-house analytical testing techniques that will aid in monitoring of the biodiesel production.
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  • Date Issued: 2013

Diet and foraging distribution of gentoo penguins pygoscelis papua at Cow Bay, Falkland Islands

  • Authors: Handley, Jonathan Murray
  • Date: 2013
  • Subjects: Gentoo penguin -- Food -- Falkland Islands
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10724 , http://hdl.handle.net/10948/d1020377
  • Description: Knowledge of diet and distribution in marine top predators is critical in interpreting their ecological role. Furthermore, this information is required for effective management and conservation of these species. For gentoo penguins at the Falkland Islands a previous overlap in dietary items with commercial fisheries was recognised. Despite this the at-sea distribution has been poorly studied and only at a few localities. Therefore, this thesis looks to broaden the knowledge of foraging ecology for gentoo penguins at another site in the archipelago, Cow Bay. The aim was firstly, through stomach content analysis, to determine if diet changed over a large temporal scale (2002/03/04 – 2011/12/13), and between the chick guard and crèche periods of chick rearing. Secondly, through GPS loggers, to assess distribution at sea during the incubation and chick guard periods (2012/13). Additionally, foraging ecology between genders was investigated. Gentoo penguins at Cow Bay foraged primarily on fish (66-99 percent) throughout the entire study period. The principle prey item by mass was Patagonotothen spp., considered previously as discard by fisheries but now an important commercial resource, for all periods (47-78 percent) except that of the 2012/13 crèche period (19 percent). During this period Sprattus fugensis made up the bulk of the diet (52 percent). Cephalopods, particularly Loligo gahi (1-24 percent), were also prominent in the diet and crustaceans contributed negligibly. The diet indicated that gentoo penguins are capable of both a benthic and pelagic feeding strategy which likely reflects changes in local prey abundance. Birds typically conducted foraging activities during daylight hours with greater trip duration, path length, maximum distance and area utilised during the incubation period than the guard. All trips were confined to the continental shelf and within the boundaries of a marine management zone, the Falkland Islands Interim Conservation Zone (FICZ). Males and females fed on the same size and composition of prey items. Trip duration, path length and maximum distance from the colony were not significantly different, although males foraged in a slightly larger area than females marginally to the north. As at-sea distribution was confined within the FICZ this management area provides protection to food resources of gentoo penguins breeding at Cow Bay. At this site, the population is increasing, likely associated with increased prey availability as evidenced by record catches of Patagonotothen spp. in recent years at the Falkland Islands. Continued long term monitoring of gentoo penguin diet and fishery yields to allow detection of possible competition in the future is recommended. As marine sentinels, on-going monitoring of gentoo penguin populations at the Falkland Islands is likely to provide early warning signs of reduced prey availability.
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  • Date Issued: 2013

Effects of crop rotation and tillage system on the control of ryegrass (lolium multiflorum X perenne) in wheat (triticum aestivum) in the Swartland production area of South Africa's Western Cape Province

  • Authors: Nteyi, Sinovuyo Mava
  • Date: 2013
  • Subjects: Cropping systems , Conservation tillage -- South Africa -- Western Cape , Ryegrasses
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: vital:10738 , http://hdl.handle.net/10948/d1020990
  • Description: A major challenge facing agriculture today is to sustain the productivity of agricultural systems with the reduction of weed invasion. The Swartland region in the Western Cape (South Africa) is intensively cropped, producing wheat (Triticum aestivum) as the major crop. As a result of the weedy ryegrass invasion the wheat yield is reduced. In addition, ryegrass has developed resistance to grass herbicides (graminicides). This situation has increased the need to use alternative practices for controlling the invasion of ryegrass in wheat fields. In this regard, crop rotation and tillage systems were proposed as techniques to suppress the ryegrass invasion. This could thus maintain a sustainable long-term wheat production system with less application of herbicides, decreased input costs and increased total grain yield. Against this background, the effects of crop rotation and tillage were determined on ryegrass seedling emergence in a field and shade netting experiment, while seed dormancy was determined in the laboratory. The objectives were to compare the wheat production of two crop rotations with mono-cropped wheat and assess the impact on the ryegrass population in no-till and minimum tillage systems. Analyses of variance on data sets of ryegrass seeds from 2009, 2010 and 2011 were used to determine germination and dormancy percentages in laboratory experiments. The performance of laboratory treatments was evaluated on the basis of germination percentage of seeds. In the field and shade netting experiments, analyses of variance for data from 2007, 2011 and 2012 were used to determine crop rotation x tillage system response. Field and shade netting performance were evaluated on the basis of ryegrass population inhibition and stimulation respectively. Ryegrass seeds from 2009 and 2010 showed higher germination percentages (80 per cent and 73 per cent) than 2011 (42 per cent). Primary dormancy prevented high germination of newly harvested seeds as dormancy release increase with age of the seed. Results of field and shade netting experiments showed stimulation of the ryegrass weed population in wheat monoculture under minimum tillage. However, when wheat was rotated with leguminous crops under both tillage systems (minimum-till and no-till) ryegrass was significantly inhibited. It was concluded that the critical period for weed competition is the first six weeks after planting. Results from this study provide a basis for producers of cereals to make good decisions with regards to timing weed control measures. It is essential to use competitive crop sequences which will inhibit weeds. The challenge is getting this practice adopted and implemented by producers as it will promote conservation agriculture within the region. This study promotes long-term sustainable wheat production systems with an efficient weed management programme that is environmentally friendly using less herbicides within the Swartland region.
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  • Date Issued: 2013

Environmentally friendly dyeing and finishing

  • Authors: Dayla, Mackraj
  • Date: 2013
  • Subjects: Dyes and dyeing -- Knit goods -- South Africa , Textile finishing -- South Africa , Bleaching industry -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10454 , http://hdl.handle.net/10948/d1020776
  • Description: The textile industry in South Africa is a significant contributor to the chemical load that public wastewater treatment plants have to process, and the discharge of toxic substances, especially to the aquatic environment. In order to address this issue at factory level, the processes at a textile plant, JMV Textiles were chosen for investigation into the possibilities of minimization of discharges of harmful substances into the environment. The study followed the principles of cleaner production, and the processes that were investigated and revised were: The conventional peroxide bleaching process employed a peroxide stabilizer that did not biodegrade easily. The bleaching process was changed, so that the prevailing conditions in the fabric and dyebath facilitated bleaching without the addition of peroxide stabilizer, and also reduced the alkali and energy requirements. Polyester‐viscose fabric was pretreated by bleaching with hydrogen peroxide, which seemed to be unnecessarily rigorous, because polyester and viscose, unlike natural fibres, are relatively clean and have good whiteness in comparison with natural fibres. The proposed alternate pretreatment was a scour with detergent and alkali. The pretreatment for all polyester‐cotton fabrics was also a hydrogen peroxide bleach. Due to the ability of medium and dark shades to mask the natural tint of cotton fibres, a simpler alternate pretreatment, consisting of an alkaline scour with sequestering agent, was trialled. An unacceptable proportion of the dyeings on polyester was rejected for dye‐stains and dye‐marks. A possible solution exploited the properties of using the finishing auxiliary chemical to alleviate dye‐stains and dye‐marks during the dyeing stage, instead of using the chemical after dyeing. The highly toxic carrier that was used to facilitate level dyeing of polyester fibres that had unacceptable variation in their dyeing properties, was replaced by a less toxic carrier. The formulation for dyeing polyester was simplified to eliminate the auxiliary chemicals that were not essential to the dyeing process. Pale reactive dyed shades on cellulose and polyester‐cellulose were washed off only with hot water instead of detergent. The revised procedures consequential to the study, offered significant environmental benefits by reducing the concentration and volume of effluent produced, substituting a highly toxic carrier with a less toxic one and saving energy and water. Implementation of the suggested changes also offered financial benefits. The management of the factory, however, accepted and implemented some changes, but wanted further investigations for others and a phased approach to the other suggested changes.
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  • Date Issued: 2013

Evaluation of eucalyptus citriodora derived p-menthane-3,8-diol-citronellal acetal as a bio-plasticizer for cosmetic application

  • Authors: Burger, Kirstin
  • Date: 2013
  • Subjects: Plasticizers , Eucalyptus citriodora
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10420 , http://hdl.handle.net/10948/d1014080
  • Description: Plasticizers are generally added to cosmetic and personal care products to improve the filmforming abilities of the product and increase flexibility of the film formed on the skin or hair surface. For example, plasticizers are present in perfumes to prolong the release of the specific scent, which is the ultimate goal in a good quality perfume. Plasticizers in nail varnishes prevent chipping, improve the aesthetics by adhering to the keratin in the nail which means the coating stays on for much longer, which is the ultimate goal in nail products. Plasticizers improve the gloss, resist chipping and allow quick drying time. Therefore it can be seen that plasticizers play a vital role in personal care products like perfumes and nail varnishes. Certain plasticizers e.g. phthalates, can cause problems associated with human health and can harm the environment. They are easily available and large volumes can be obtained at a low cost. These phthalates, for example, di-butyl phthalate (DBP) have been identified as carcinogenic. Nowadays the occurrence of cancer is rapidly increasing. The plasticizers present in a large number of consumer and personal care products, can possibly be linked to the ever increasing reports of cancer. Therefore a substitute to the traditional phthalate plasticizers must be investigated. The aim of this research is to produce a plasticizer derived from naturally occurring Eucalyptus oil, which can be used to replace the existing plasticizers in cosmetic formulations. Para-menthane-3,8-diol (PMD), occurring naturally in the oil from the tree, Eucalyptus citriodora, forms an acetal with citronellal (PMD, acetal, citronellal all occur naturally in the oil). It has been previously shown that PMD-citronellal acetal will exhibit plasticizing properties similar to conventional plasticizers. The objective was to enhance the formation of the acetal in the Eucalyptus oil by reacting it with excess PMD. An effective synthesis method for the PMD-citronellal acetal enriched oil (~73.8 percent) was determined from optimization experiments. The physical characterisation of the PMD-citronellal acetal enriched oil was done and compared with that of DBP. The acetal-enriched oil had a lower density, slightly higher solubility in water (at 25°C), lower refractive index (Brix percent) and a higher boiling point (350°C) than DBP. The physical characteristics of the Eucalyptus oil source and the acetal-enriched Eucalyptus oil were very similar. This can be expected as the Eucalyptus oil consists of ~84.3 percent Citronellal, ~ 1.3 percent PMD and 2.7 percent PMD-citronellal acetal. In this study the effectiveness of the acetal-enriched Eucalyptus oil (referred to from now on as the bio-plasticizer) was compared to a conventional plasticizer such as di-butyl phthalate (DBP), commonly used in cosmetic products. Two cosmetic formulations were produced: a nail varnish and a perfume formulation. Various tests were performed on these formulations to investigate the plasticizing properties of the bio-plasticizer. The objectives were to determine if the natural plasticizer is as effective as the potentially carcinogenic phthalate plasticizers and can be used as a substitute for the phthalates in personal care products. The results indicate that the bio-plasticizer does behave similarly to di-butyl phthalate, however, the effectiveness of the bio-plasticizer is lower than that of di-butyl phthalate. As the viscosity of the synthesized oil was high, this affected the overall consistency of the products. A more viscous nail varnish and perfume was produced in comparison to the DBP counterpart. The stability of the bio-plasticizer in the cosmetic formulations of nail varnish and perfume was also investigated. The cosmetic products were incubated at 0°C, 25°C and 40°C over a period of two months. Any changes in colour, odour, pH, refractive index, separation and plasticizer peak change in the gas chromatogram trace were recorded. It was determined that the PMD-citronellal acetal-enriched oil was relatively unstable under elevated temperatures and light intensity. Storage under higher temperatures (40°C) tends to increase the acidity. Therefore the bio-plasticizer must be placed in a closed, covered bottle and stored in an environment away from light and elevated temperatures. According to the gas chromatogram peaks, it was clear that both the bio-plasticizer and the DBP were more unstable in the perfume formulation than in the nail polish and were especially sensitive to light when in the perfume. This could possibly be due to the interaction with the fragrance molecule, p-anisaldehyde.
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  • Date Issued: 2013

Evaluation of plant extracts : artemisia afra and annona muricata for inhibitory activities against mycobacterium tuberculosis and human immunodeficiency virus

  • Authors: Pruissen, Megan Colleen
  • Date: 2013
  • Subjects: Plant extracts , Medicinal plants -- South Africa , Tuberculosis -- Alternative treatment -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10341 , http://hdl.handle.net/10948/d1019845
  • Description: Mycobacterium tuberculosis and Human Immuno-Deficiency Virus (HIV) have a high prevalence in South Africa. The development and spread of drug resistant tuberculosis is a serious problem which is exacerbated by tuberculosis (TB) co-infection in HIV patients. Traditional medicinal plants like Annona muricata and Artemisia afra are used for respiratory ailments and antiviral therapies respectively. The aim of this study was to evaluate Annona muricata (ethanolic extract) and Artemisia afra (ethanolic and aqueous extracts) for inhibitory activities against M. tuberculosis and HIV. In vitro bioassays for anti-TB activity included: microplate alamar blue assay (MABA), flow cytometry and ρ-iodonitrotetrazolium chloride assays while anti-HIV activity was determined using an HIV-1 reverse transcriptase colorimetric ELISA kit and an HIV-1 integrase colorimetric immunoassay. Cytotoxicity of plant extracts were assessed by the MTT assay on Chang Liver and HepG2 cells. Potential synergistic effects were determined using the basis of Combination Index. Potential interactions of plant extracts with drug metabolic pathways were evaluated with the Glutathione-S-Transferase assay kit as well as the CYP3A4 assay kit. A. muricata ethanolic extract exhibited anti-TB activity with MIC 125 μg/mL. MABA was shown to be the most sensitive and effective method for the detection of anti-TB activity. Artemisia afra aqueous extract showed HIV-1 reverse transcriptase inhibition exhibiting ˃85 percent inhibition at 1 mg/mL while the ethanolic extracts of A. afra and A. muricata showed inhibition of HIV-1 integrase activity at ˃86.8 percent and ˃88.54 percent respectively at concentrations >0.5 - 4 mg/mL. The aqueous extract of A. afra displayed inhibition of HIV-1 integrase ˃52.16 percent at 0.5 mg/mL increasing to 72.89 percent at 4 mg/ml of the extract. A. muricata was cytotoxic at an IC50 of 30 μg/mL and 77 μg/mL on Chang Liver and HepG2 cells respectively, whilst A. afra aqueous and ethanol extracts were not cytotoxic to both cell lines. The ethanolic extract of A. muricata showed both antagonistic and synergistic properties at various IC values, when used in conjunction with rifampicin. A. afra ethanolic extract interrupted GST activity while aqueous extracts of A. afra and A. muricata had a slight effect. All extracts interrupted CYP3A4 activity, however the ethanolic extracts of A. muricata and A. afra showed greater inhibition than the aqueous extract of A. afra. These extracts should be investigated further as they could be an important source of compounds for treatment of M. tuberculosis and HIV respectively.
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  • Date Issued: 2013

Exploring interventions for participation of emerging farmers in the Eastern Cape ostrich-industry supply chain

  • Authors: Pittaway, Timothy
  • Date: 2013
  • Subjects: Farmers -- South Africa -- Eastern Cape , Ostrich products industry -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10596 , http://hdl.handle.net/10948/d1021008
  • Description: The changing agricultural environment (dualistic agricultural landscape, land reform programme, market liberalisation and globalisation) has caused emerging ostrich farmers to become increasingly isolated. Governmental agriculture reforms and public sector interventions have been insufficient to address all the challenges faced by rural ostrich farmers in the Eastern Cape. Participation in the ostrich supply chain for emerging farmers in the Eastern Cape is currently unsustainable as a result of avian influenza, control and registration protocols for ostriches (VPN04), structural barriers in marketing, technical constraints and a lack of market participation. People in the rural areas of the Eastern Cape are challenged by inferior infrastructure, poor site conditions, low earnings, poor access to health services and unreliable water sources. The marginal conditions and prevalent complexities in which agriculture is practised require costly resource intervention. Intensive ostrich production necessitates continuous genetic improvement, methodical record keeping, intensive egg incubation methods and highmaintenance chick rearing and ostrich handling while minimising feed costs throughout this process. Rural farmers have not embraced ostrich farming in the same way as they have done with other livestock farming because it does not offer the anthropological functions that traditional livestock farming provides. The ostrich supply chain requires a wide range of activities to bring products to the final consumer. The worth of ostrich production lies mainly in the higher returns which are achieved only through the export markets. Today the ostrich industry has become vulnerable to market cannibalism, a lack of market development, unregulated numbers of ostriches and recurring international meat bans. The deregulation of the ostrich single-channel marketing system had a substantial effect on the value chain on which farmers depended for market access and market protection. As the majority of ostrich products are being exported to the European Union, the role of intermediary agencies is becoming an important factor influencing entry into the high-end markets. This agent structure that represents the South African ostrich industry is vital for the distribution, market penetration and regulation of the ostrich products. The ostrich leather, which is today the main product line, is primarily used for luxury goods and is susceptible to economic downturn and over-supply. The ostrich meat industry has been severely influenced by outbreaks of avian influenza and processors now pre-heat the meat in order to maintain export. However, this preheating meat facility is only for export produce and available to farmers who conform to VPN04 and have officially registered farms. The relevant South African government departments played a crucial role in identifying avian influenza outbreaks and liaising with the European Union about avian influenza isolation strategies. No previous studies have been conducted on the participation of emerging farmers in the Eastern Cape ostrich-industry supply chain and on the interventions required to address the multiple constraints and forces in this sector. This led to a study with research emphasis on the required capacity for supply-chain participation and the supporting mechanisms that would be required for emerging ostrich farmers to integrate successfully into this supply chain. An exploratory research approach was chosen for the investigation, as no earlier research has been undertaken that could serve as a source of reliable data or reference. A triangulation research methodology using both the quantitative and the qualitative approach was applied. The qualitative research entailed an interpretive approach associated with using grounded theory and content analysis for interpreting data. The comparative case study design was the main qualitative research instrument for the multiple-case studies on emerging ostrich farmers in the Eastern Cape. The study was undertaken at five different sites, namely, the Peddie Ostrich Programme, the Rockhurst Ostrich Programme, the Hlumani Co-operative farm, the Zamukwanda Ostrich farm near Pearston and the Mimosadale Ostrich farm. The quantitative methods were applied to capture all the measurable components and representations of the stakeholders and participants, through interviews, questionnaires and focus group interviews. The quantitative study also included an experimental instrument to measure the capacity of emerging farmer programmes for supply chain participation. It was found that the main driver for three of the case studies pertained to land ownership and that ostrich farming was incidental and only seen as means of activity for income. These three humanitarian farming projects had limited capacity for intensive management requirements for ostrich farming. It was found that the VPN04 bio-security protocols and disease control require a higher level of record keeping for EU markets and is prohibitively expensive for poor rural emerging farmers. The study established that the emerging ostrich farming programmes contributed value to the industry and government rural development in land redistribution programmes, vehicles for reduction of poverty and job creation in the rural areas and by acting as out-grower programmes for commercial farmers. The researcher’s observation is that through strategic interventions the programmes have potential to become commercial players in the industry. The following interventions were recommended from this study: Feasibility study of programmes and review of location selection before initiation. Providing supportive interventions for programme start-ups; Improved selection of programme beneficiaries; Improved structure of emerging farmers’ co-operatives; On-going and appropriate training for emerging ostrich farmers; The role of government and mentors needs to be defined; Reducing feed costs; Establishing programmes linkages to informal markets and facilitating increased self-consumption; Developing new export markets; Alternative finance for the no-income months; Alternative marketing channels to export markets; Representation of emerging farmers in the ostrich-industry leadership structures.
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  • Date Issued: 2013

Foraging ecology of Cape Gannets (Morus Capensis) at Bird Island, Algoa Bay

  • Authors: Green, David Bruce
  • Date: 2013
  • Subjects: Birds of prey -- Behavior -- South Africa -- Algoa Bay , Gannets -- South Africa -- Algoa Bay , Birds -- Breeding -- South Africa -- Algoa Bay
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10725 , http://hdl.handle.net/10948/d1020790
  • Description: The Cape gannet has undergone considerable population change and redistribution over the past 50 years. This has been linked to shifts in the abundance and distribution of their dominant prey, sardine and anchovy. Five breeding colonies, along the west coast of Southern Africa, have shown rapid population declines as a result of reduced prey availability. In contrast, a single colony (Bird Island, Algoa Bay) on the south coast of South Africa has, over the same period, grown fivefold and now supports approximately two thirds of the total population. Due to its conservation importance, and isolation from other breeding localities, it is important to assess the health of the Bird Island colony, and determine how foraging distribution relates to the environment to evaluate current measures of protection. This was achieved through two related studies; a long-term dietary analysis spanning 34 years, and a spatial foraging study, which related three years of tracking data to estimates of prey availability, oceanographic features and marine protected areas (MPAs). The results of the dietary study showed that the dietary constituents of Cape gannets breeding at Bird Island have remained similar over the last three decades, but the importance of sardine and anchovy has increased significantly. For sardine, in particular, this reflects an increased availability of this species (as deduced from hydroacoustic surveys) within the foraging range of the Bird Island colony. The dietary abundance of anchovy was found to be negatively correlated with that of sardine. Surprisingly,.the dietary abundance of anchovy was also negatively correlated with estimates of its availability based on acoustic surveys. The latter is likely to be due to sardine being a preferred prey item. Recent decreases in the dietary contribution of sardine (since 2005) suggest that this species is becoming less available to gannets, with profound implications in terms of nutrient gain associated with foraging. However, this has been mediated by an increase in the dietary contribution of anchovy, which now accounts for the vast majority of prey taken. Spatially, the foraging range of the Bird Island colony expanded during the three years of study, indicating an increase in effort. This increase was likely in an effort to track a distributional change of sardine and anchovy, which showed an apparent westward shift during the study period. There was, however, no evidence of birds tracking features associated with high productivity. This may have been partly due to anomalously warm conditions during the summer of 2012/2013, in which an absence of coastal upwelling prevented surface cooling. Nonetheless, low sea surface temperatures and high chlorophyll a concentrations do not seem to be reliable indicators of important Cape gannet foragingareas. Foraging effort was largely concentrated outside of MPAs, indicating that the current MPA network provides little protection for foraging gannets. This could change with the additional protection of the proposed Greater Addo Elephant National Park MPA expansion, as prey species are allowed to recover following the removal of fishing pressure. Overall, the colony appears to be in good condition as the diet is still dominated by live prey items, and the foraging range remains smaller than many of the colonies along the west coast. However, it is important that monitoring be continued, in particular with respect to changes in the availability of sardine and anchovy. Long-term shifts of these species out of the colony‘s foraging range could negatively influence the population in the future. This might be worsened by interspecific competition for prey resources. Considering the conservation importance of this population, maintenance of healthy prey stocks within the home range of breeding Cape gannets should be prioritised in order to prevent declines similar to those observed at west coast colonies.
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  • Date Issued: 2013

High performance nonwovens in technical textile applications

  • Authors: Ogunleye, Christopher Olarinde
  • Date: 2013
  • Subjects: Nonwoven fabrics , Textile fabrics -- Technological innovations
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10356 , http://hdl.handle.net/10948/d1021011
  • Description: The aim of this research was to establish the optimum processing conditions and parameters for producing nonwoven fabrics best suited for application in disposable and protective wear for surgical gowns, drapes and laboratory coats. Carded and crosslapped webs, of three basic weights (80, 120, and 150g/m2), from greige (unscoured and unbleached) cotton, viscose and polyester fibres, were hydroentangled, using three different waterjet pressures (60, 100 and 120 bars), on a Fleissner Aquajet hydroentanglement machine. An antibacterial agent (Ruco-Coat FC 9005) and a fluorochemical water repellent agent (Ruco Bac-AGP), were applied in one bath using the pad-dry-cure technique, to impart both antibacterial and water repellent properties to the fabrics, SEM photomicrographs indicating that the finished polymers were evenly dispersed on the fabric surface. The effect of waterjet pressure, fabric weight and type and treatment on the structure of the nonwoven produced, was evaluated by measuring the relevant characteristics of the fabrics. As expected, there was an interrelationship between fabric weight, thickness, and density, the fabric thickness and mass density increasing with fabric weight. An increase in waterjet pressure decreased the fabric thickness and increased the fabric density. The water repellent and antibacterial treatment increased the fabric weight and thickness. The antimicrobial activity of the fabrics was assessed by determining the percentage reduction in Staphylococcus aureus and Escherichia coli bacteria population. The maximum percent reduction at 24hrs contact time for both bacteria ranged from 99.5 to 99.6 percent for all the fabric types. The standard spray test ratings for the three treated fabrics ranged from 80-90 percent, whereas that of the untreated water repellent fabric was zero, while the contact angles for all the fabric types exceeded 90 degrees, indicating good resistance to wetting. It was found that the tensile strength of the fabric in the cross-machine direction was higher than that in the machine direction, for both the treated and untreated fabrics, with the tensile strengths in both the MD and CD of the treated fabrics were greater than that of the untreated fabrics, the reverse being true for the extension at break. An increase in waterjet pressure increased the tensile strength but decreased the extension at break, for both the treated and untreated fabrics. The finishing treatment decreased the mean pore size of all the fabrics, the mean pore size decreasing with an increase in fabric weight and waterjet pressure. An increase in waterjet pressure and fabric weight decreased the air and water vapour permeability, as did the finishing treatment, although the differences were not always statistically significant. The polyester fabrics had the highest water and air permeability. Hence low weight fabrics of 80 g/m2, which were hydroentangled at low water jet pressures of 60 bars, were suitable for use in this study due to their higher air and water vapour permeability as well as higher pore size distribution. These group of fabrics thus meet the requirements for surgical gowns, drapes, nurses’ uniforms and laboratory coats.
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  • Date Issued: 2013

Hydrothermal liquefaction of scenedesmus obliquus in a continuous reactor system

  • Authors: Kaufmann, Gideon
  • Date: 2013
  • Subjects: Biomass chemicals Microalgae -- Biotechnology , Supercritical fluids
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: http://hdl.handle.net/10948/47878 , vital:40393
  • Description: In 2009 InnoVenton, a research institute at the Nelson Mandela Metropolitan University (NMMU) set out to establish a technological concept of micro-algae to fuel, at which point an algae farm was established. The overall research strategy is envisaged to focus on a number of potential uses of algae biomass and related processes such as water treatment can take place, the binding of the biomass to coal fines to create briquettes are possible, and bio crude production from direct liquefaction. This project will focus on the latter. In 2010 a partnership between NMMU and the University of Cape Town’s (UCT) Department of Chemical Engineering was established to design, construct and commission a test unit that could convert the algae biomass into a pumpable bio crude by the liquefaction process. During the initial operation of this test unit, flow problems of the reaction product were observed. As such, the aim of this study is to investigate a number of process conditions and develop strategies to minimise or alleviate this problem. As part of this study, UCT will replicate the NMMU test unit in Cape Town in order to start focussing on finding relevant solutions to the problems which exist. Presently continuous reactor systems are not used for the liquefaction of micro-algae. According to Toor, et al(2011)¹ Other feedstocks have been placed in continuous reactor systems with good end results. They continue to write in their review that batch systems were used in most experiments. If micro-algae are to become a competitive alternative to crude oil then batch systems are not the way forward. From a commercial and efficiency standpoint, there are significant advantages to move from typical batch reactors to continuous reactors, specifically in terms of downtime and loading/unloading of vessels. From the evidence gathered in Port Elizabeth, the nature of the reaction product caused typical plugflow reactor systems to block. The aim of this study is to investigate possible solutions to the problem of the reactor system blockage and thus pave the way for the implementation of a continuous reactor system. There are many variables which can be manipulated to achieve success for example the use of catalysts, co-feeding of reactant gases like hydrogen, residence time, temperature or pressure. Manipulating these variable can help to change conversion and/or product spectrum. The results of this study will be compared to results obtained by typical batch experimentation conducted at NMMU. This research varied temperature only. This variation was effective enough to find solutions to the obstacles that were present. Once the algae feedstock was being diverted to the vent pot via the safety relief valve, it was understood that something was blocked. Once the reactor was cooled and removed, it was apparent that the reactor was not blocking up however the exit line to the product catch pot was. To solve this problem a new heated zone was created. This heated the exit line and the top of the product catch pot to around 50°C below the reaction temperature. This upgrade to the system made the oil liquor less vicous and flow easier. The exit line never blocked up again during the research. Energy values of the product were comparable to that of coal. Higher reaction temperatures favoured the production of paraffins and olefins while lower reaction temperatures favoured the production of oxygenates. An ampoule sampler was introduced to take samples of the gas exit line. The comprehensive gas chromatography analysis of the gas in the ampoules revealed that eventhough the concentration of the products present were low, there were significant quantities of paraffins present in the gas stream. More research and the variation of variables discussed previously need to be conducted. It is also apparent that the test unit needs to be upgraded to a bigger reactor and possibly to use materials of construction which do not corrode easily. A computer model could be developed in conjunction with the current test unit and then a bigger reactor might not be needed. The reducing of the oxygen content in the final bio crude also needs to be investigated. Overall the research is very promising in the fact that the final bio crude that was produced is comparable to coal. With further research it will be possible to create a product that is comparable to fossil crude oil and then could be used as a supplement to crude oil.
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  • Date Issued: 2013

In silico and in vitro screening of marrubiin and marrubiin derivatives for antidiabetic activity on PTP1ß, C2C12 myocytes, chang liver hepatocytes and 3T3-L1 adipocytes

  • Authors: Nicholas, Rudi Berto
  • Date: 2013
  • Subjects: Hypoglycemic agents , Diabetes -- Treatment -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10347 , http://hdl.handle.net/10948/d1020638
  • Description: Diabetes mellitus (DM) is a life changing disease which affects a large portion of the population and the economy through high medical costs and loss of productivity. Marrubiin (MAR), a diterpenoid isolated from Leonotis leonurus, a plant indigenous to Southern Africa, is used by traditional healers to alleviate DM symptoms. This study aims to screen the inhibitory potential of MAR and MAR derivatives on PTP1β and glucose uptake properties of Chang liver, C2C12 and 3T3-L1 cells. Marrubiin and 19 of its derivatives were tested to determine the inhibition constants for PTP1β. A Ki of 21 μM and 0.047 μM was detected for oleanolic acid in silico and in vitro, respectively. All other diterpene derivatives did not display substantial levels of inhibition of PTP1β. Treatment of Chang liver cells with the various MAR derivatives (10 μM) did not significantly increase glucose uptake beyond metformin, a known antidiabetic drug. The various treatments showed a protective/proliferative effect on the C2C12 muscle cells with two MAR treatments (DC16 and DC18) significantly increasing glucose uptake as compared to metformin in C2C12 muscle cells. It was noted that DC17, DC18 and MAR significantly increased glucose uptake in 3T3-L1 adipocytes, relative to the control. Contrary to cytotoxicity studies with Chang liver and C2C12 muscle cells, adipocytes displayed no cytotoxicity to treatments while a significant increase in cell viability was seen for DC9 and DC15. To unravel the mechanism of action, Western blotting analysis was completed and an increased expression of PTP1β was observed for treatments with DC17 and DC6 was seen in adipocytes, while DC18 and metformin decreased expression significantly. This correlated with a significant decrease of Ser 612 phosphorylation of insulin receptor substrate (IRS1) for DC17. Real time qPCR of IRS1 and GLUT4 highlighted that DC17 and MAR were able to significantly increase expression of IRS1 and GLUT4, respectively. The results show that MAR and the selected derivatives (DC6, DC17, DC18) have been found to increase glucose uptake in peripheral tissue types with IRS1, GLUT4 and PTP1β being associated with the mechanism of action. However, a complete understanding of the mechanisms is yet to be established.
  • Full Text:
  • Date Issued: 2013

Influence of predicted sea-level rise on the salt marsh of the Swartkops, Kromme and Knysna estuaries

  • Authors: Schmidt, Jadon
  • Date: 2013
  • Subjects: Sea-level -- South Africa , Salt marshes -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/3765 , vital:20462
  • Description: Salt marshes are coastal wetlands that are highly productive and biologically diverse ecosystems. These systems are under threat from rising sea levels which are predicted to accelerate in the future. Salt marsh habitats of the Swartkops, Kromme and Knysna estuaries were examined to determine their structure along an elevation gradient and how this structure has changed over the past six decades, what the primary drivers of this structure were and whether the salt marsh surface is stable, rising or declining relative to predicted sea level rise. During this study the following main hypothesis was tested: The environmental drivers of salt marsh zonation are elevation above mean sea level (AMSL), soil moisture and soil salinity, all of which will be impacted by the predicted rise in sea level of 1.48 mm.y-1, unless the salt marshes are able to accrete at a rate such that surface elevation gain is sufficient to offset the rate of sea level rise. The results showed that the salt marsh vegetation structure followed a predictable pattern down the elevation gradient with distinct supratidal, intertidal and subtidal habitats identified for each estuary. These three zones occurred between elevations around Mean Sea Level of -0.86 to 2.42 AMSL for Swartkops, -0.3 to 2.95 m AMSL for Kromme and -0.48 to 3.14 m AMSL for Knysna. A floodplain component was also identified in the Swartkops estuary, which was restricted to the upper reaches. During the last 60 years, losses of intertidal and supratidal salt marsh for Swartkops were 74.31 ha and 30.23 ha respectively, 17.01 ha of intertidal and supratidal salt marsh was lost in Kromme while intertidal salt marsh in Knysna has diminished by 168 ha. These losses were mainly attributed to developmental pressure, although there are indications that rising sea levels are becoming more influential in the lower reaches. The main environmental drivers for salt marsh structure in the Swartkops were shown to be soil moisture content and elevation, soil moisture and organic content for Kromme while elevation and soil redox potential were dominant in Knysna. In a comparison of all three systems, soil moisture content and redox potential were found to be the most important drivers of vegetation distribution. Elevation dictates tidal inundation periodicity and frequency, and thus acts to influence all edaphic factors driving vegetation distribution. Results indicated that the salt marsh surface elevation of the lower and middle sections of the Swartkops, Kromme and Knysna estuaries are generally declining relative to current sea level rise. Where increases in surface elevation (relative to current sea level rise) were recorded, the majority of the accretion occurred after episodic flooding in winter 2011. These increases typically occurred in the upper reaches and were attributed to the deposition of fluvial sediments as a result of these floods. Results for Knysna indicate that while a majority of the salt marsh surface is accreting vertically, only three areas are increasing their elevation at a rate at least equal to current sea level rise. In these areas, developmental pressures will prevent a landward transgression of the salt marsh, forming an artificial “coastal squeeze”. Geomorphological limitations (steep hills adjacent to the salt marsh) will prevent any transgression in the upper reaches of the Kromme Estuary. Supratidal habitat in the upper reaches of the Swartkops estuary, if undeveloped, will provide the only viable habitat for the salt marsh to migrate into, given sufficient surface elevation.
  • Full Text:
  • Date Issued: 2013

Isocyanide complexes of rhenium

  • Authors: Schoultz, Xandri
  • Date: 2013
  • Subjects: Isocyanides , Rhenium , Complex compounds
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10360 , http://hdl.handle.net/10948/d1021069
  • Description: This study investigates the synthesis of rhenium(III)-isocyanide complexes with potentially bidentate ligands, as well as the reactivity of isocyanide ligands toward rhenium(I) and (V). The crystal structures of all the complexes have been determined by X-ray diffraction methods. The coordination behaviour of trans-[ReIIICl3(t-BuNC)(PPh3)2] with aniline and its derivatives were investigated. The isocyanide-containing rhenium(V) complexes [ReCl3(t-BuNC)(L)(PPh3)] were isolated, with the ligands H2L (aniline, o-phenylenediamine and anthranilic acid). In all these complexes the dianionic ligands L are coordinated monodentately as the imide. However, with 2-aminophenol the complexes [ReVCl2(t-BuNC)(L)(PPh3)2](ReO4) and [ReIIICl2(t-BuNC)(ibq)(PPh3)2] (ibq- = 2-iminobenzoquinonate) were identified as the products. [ReCl2(t-BuNC)(L)(PPh3)2](ReO4) is the product of a disproportionation reaction from Re(III) to Re(VII) and Re(V). All the above complexes show a distorted octahedral geometry around the rhenium. The products of the reaction of the Re(I) complex [Re(CO)5Cl] with isocyanides (tert-butyl- and cyclohexylisocyanide) are reported. Rhenium(I) tricarbonyl complexes of the form [Re(CO)3(CNR)2Cl] were isolated and they were characterized structurally and spectroscopically. The tricarbonyls are coordinated in the typical facial-fashion, whereas the isocyanides are coordinated cis to each other. The reaction of [Re(CO)3(t-BuNC)2Cl] with H2O led to the formation of the rhenium(I) complex [Re(CO)3(t-BuNC)2(OH2)] in which the aquo ligand can readily be substituted by a more complex ligand. The reaction of the rhenium(V) complexes cis-[ReO2I(PPh3)2] and mer-[ReOCl3(SMe2)(OPPh3)] with isocyanides were studied. The seven-coordinate trigonal prismatic, square faced monocapped rhenium(III) complex [ReI3(t-BuNC)3(PPh3)] was surprisingly isolated upon reacting cis-[ReO2I(PPh3)2] with tert-butyl isocyanide. The dimeric complex (μ-O)[ReOCl2(CNC6H11)2]2 was obtained from the reaction of mer-[ReOCl3(SMe2)(OPPh3)] with cyclohexyl isocyanide.
  • Full Text:
  • Date Issued: 2013

Microcystin enhances the fitness of microcystin producing cyanobacteria at high light intensities by either preventing or retarding photoinhibition

  • Authors: Phelan, Richard Reginald
  • Date: 2013
  • Subjects: Microcystins , Microcystis , Cyanobacterial toxins
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10354 , http://hdl.handle.net/10948/d1020957
  • Description: Several genera of cyanobacteria produce microcystin, a monocyclic peptide, with a unique chemical structure. To date, there have been over a 100 different structural variants of microcystin which have been identified. Microcystin production is affected by numerous environmental factors. However, the primary modulating factor for intracellular microcystin quota is the intracellular N:C ratio. No clearly defined biological role has been described for microcystin. Proposed roles for microcystin include defence against plankton grazers, metal chelation, an infochemical and a protectant against oxidative stress. There is sufficient evidence to support a biological role for microcystin in photosynthesis: microcystin is predominantly located in the thylakoid membranes, the microcystin gene cluster is differentially expressed as a function of light and a growth advantage for the microcystin producer in saturating light intensities. The purpose of this study is to investigate a possible biological role for microcystin in preventing photoinhibition and thus explaining the growth advantage observed in toxin-producers over non-toxin-producers. The uptake of exogenous microcystin was observed in Synechocystis PCC 6803 which was internalized and located in the thylakoid membranes and caused the inhibition of photosynthesis. Microcystin variants and increasing concentrations of microcystin-LR had no effect on the fluidity of the thylakoid membranes. The exposure of thylakoid membranes from Synechocystis PCC 6803 to physiologically relevant concentrations of different microcystin variants resulted in the inhibition of photosystem II activity but not photosystem I activity. The inhibition of photosystem II was variant dependent and concentration dependent for microcystin-LR and microcystin-RR. Chlorophyll a fluorescence data showed that photosystem II inhibition was caused by the inhibition of the oxygen evolving complex. Furthermore, a completion study revealed that the microcystin-producing Microcystis PCC 7806 had a competitive advantage over the non-microcystin producing ΔmcyA mutant of Microcystis PCC 7806 at high light intensities. The data indicates that microcystin protects the toxin-producer by either retarding or preventing photoinhibition and thus identifying the first data supported function for microcystin in cyanobacteria.
  • Full Text:
  • Date Issued: 2013

Molecular signaling in colorectal carcinogenesis : the roles and relationships of beta-catenin, PPARgamma and COX-2

  • Authors: Fredericks, Ernst
  • Date: 2013
  • Subjects: Colon (Anatomy) -- Cancer , Cyclooxygenase 2 , Peroxisomes
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10357 , http://hdl.handle.net/10948/d1021014
  • Description: Colorectal cancer (CRC) is a common disease with significant morbidity and mortality. In spite of significant advances in understanding the molecular signaling in this disorder, unanswered questions remain. Cyclooxygenase-2 (COX-2) and β-catenin have established roles in colorectal carcinogenesis, with both being upregulated early in the disease course. The role of peroxisome proliferator-activated receptor γ (PPARγ) is less clear, but has been shown to be downregulated in colon cancer models. Butyrate, a short chain fatty acid, produced by colon microbiota and transported into the colonocyte by transporter proteins, appears to be important in early carcinogenesis. The butyrate concentration is reduced in CRC and so are its transporters. Interleukin-17 (IL-17) plays a role in colitis-associated colorectal cancer (CAC), but its function in sporadic CRC is less clear. Similarly, Protein kinase C (PKC) has proven involvement in many solid tumours, including CRC, but its exact mechanistic role is still speculative. AIM: To investigate the role and possible signaling pathways of the major role players, β-catenin, COX-2 and PPARγ in early CRC. Further, to elucidate the mechanistic pathways of butyrate and its transporters, IL-17 and PKC in CRC. METHOD: Informed consent was obtained for all patients. Patients were recruited in various disease categories, including normal, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD) and CRC. Colon biopsy specimens were obtained during colonoscopy and used for immunohistochemistry (IHC) and gene expression analysis of the above genes by quantitative polymerase chain reaction (qPCR). RESULTS: β-catenin mRNA and protein expression was increased in CRC and the IBD groups compared to the normal group, while it was reduced in the IBS groups. COX-2 mRNA expression showed a steady increase from normal, through IBS, IBD and CRC groups to a statistically significant degree. The COX-2 protein expression, however, did not match the mRNA expression with increased COX-2 protein expression in normal and IBS groups and reduced expression in IBD and CRC groups. PPARγ mRNA expression was unchanged in IBD and CRC groups, but significantly increased in the IBS group compared to normal. Butyrate transporter, SLC16A1 mRNA was significantly reduced in CRC, but also in the IBS groups, which was unexpected. In the IBD group, SLC16A1 mRNA was unchanged in Crohn’s disease (CD) but significantly reduced in ulcerative colitis (UC). Similarly, SLC5A8 mRNA expression was significantly reduced in the CRC as well as the IBS groups. In the IBD groups, SLC5A8 was unchanged in UC but significantly increased in CD. IL-17 mRNA expression was significantly reduced in CRC and IBS groups, but unchanged in the IBD groups. PKCε mRNA was significantly increased in CRC as expected. In the IBD groups, PKCε mRNA was unchanged in CD but significantly increased in UC. In the IBS groups, PKCε mRNA in constipation –IBS (C-IBS) was significantly reduced, but unchanged in diarrhoea – IBS (D-IBS). CONCLUSIONS: β-catenin mRNA and protein expression was increased in CRC and the CRC promoting IBD groups. COX-2 protein expression was incongruent with the COX-2 mRNA expression and this may reflect homeostatic control mechanisms. High COX-2 mRNA expression in CRC and CRC promoting IBD groups may be a secondary phenomenon reflecting the inflammatory milieu, rather than a true carcinogenesis-related event. PPARγ does not appear to play a central role in early colon carcinogenesis, in spite of available literature suggesting otherwise. Butyrate transporters showed inconsistent results and for now no firm conclusions can be drawn from this. IL-17 may play a role in CAC as confirmed in this and other studies, but its role in sporadic CRC is tenuous and requires further investigation. Likewise for PKCε, upregulation is associated with increased tumourigenecity as shown in this study, however, the mechanistic pathway(s) involved is still speculative and requires further study.
  • Full Text:
  • Date Issued: 2013

Monitoring carbon stocks in the sub-tropical thicket biome using remote sensing and GIS techniques : the case of the Great Fish River Nature Reserve and its environs, Eastern Cape province, South Africa

  • Authors: Nyamugama, Adolph
  • Date: 2013
  • Subjects: Fragmented landscapes -- South Africa -- Eastern Cape -- Remote sensing , Environmental degradation -- South Africa -- Eastern Cape , Remote sensing , Geographic information systems
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10672 , http://hdl.handle.net/10948/d1020303
  • Description: The subtropical thicket biome in the Eastern Cape Province of South Africa has been heavily degraded and transformed due overutilization during the last century. The highly degraded and transformed areas exhibit a significant loss of above ground carbon stocks (AGC) and loss of SOC content. Information about land use /cover change and fragmentation dynamics is a prerequisite for measuring carbon stock changes. The main aim of this study is to assess the trends of land use/cover change, fragmentation dynamics, model the temporal changes of AGC stocks in the Great Fish River Nature Reserve and its environs from 1972 to 2010, quantify and map the spatial distribution of SOC concentrations in the partial subtropical thicket cover in the Great Fish River Nature Reserve and environs (communal rangelands). Multi-temporal analyses based on 1972 Landsat MSS, 1982 and 1992 Landsat TM, 2002 Landsat ETM and 2010 SPOT 5 High Resolution images were used for land use/cover change detection and fragmentation analysis. Object oriented post-classification comparison was applied for land use/cover change detection analysis. Fragmentation dynamics analysis was carried out by computing and analyzing landscape metrics in land use/cover classes. Landscape fragmentation analyses revealed that thicket vegetation has increasingly become fragmented, characterized by smaller less linked patches of intact thicket cover. Landscape metrics for intact thicket and degraded thicket classes reflected fragmentation, as illustrated by the increase in the Number of Patches (NP), Patch Density (PD), Landscape Shape Index (LSI), and a decrease in Mean Patch Size (MPS). The use of remote sensing techniques and landscape metrics was vital for the understanding of the dynamics of land use/cover change and fragmentation. Baseline land use/cover maps produced for 1972, 1982, 1992 2002 and 2010 and fragmentation analyses were then used for analyzing carbon stock changes in the study area. To model the temporal changes of AGC stocks in the Great Fish River Nature Reserve and its environs from 1972 to 2010, a method based on the integration of RS and GIS was employed for the estimation of AGC stocks in a time series. A non-linear regression model was developed using NDVI values generated from SPOT 5 HRG satellite imagery of 2010 as the independent variable and AGC stock estimates from field plots as the dependent variable. The regression model was used to estimate AGC stocks for the entire study area on the 2010 SPOT 5 HRG and also extrapolated to the 1972 Landsat MSS, 1982 and 1992 Landsat TM, and 2002 Landsat ETM. The AGC stocks for the period 1972 -1982, 1982-1992, 1992-200) and 2002-2010 were compared by means of change detection analysis. The comparison of AGC stocks was carried out at subtropical thicket class level. The results showed a decline of AGC stocks in all the classes from 1972 to 2010. Degraded and transformed thicket classes had the highest AGC stock losses. The decline of AGC stocks was attributed to thicket transformation and degradation which were caused by anthropogenic activities. To map and quantify SOC concentration in partial (fractional) thicket vegetation cover, the spectral reflectance of both thicket vegetation and bare-soils was measured in situ. Soil samples were collected from the sampling sites and transported to the laboratory for spectral reflectance and SOC measurements. Thicket vegetation and bare soil reflectance were measured using spectroscopy both in situ and under laboratory conditions. Their respective endmembers were extracted from ASTER imagery using the Pixel Purity Index (PPI). The endmembers were validated with in situ and laboratory thicket and bare-soil reflectance signatures. The spectral unmixing technique was applied to ASTER imagery to discriminate pure pixels of thicket vegetation and bare-soils; a residual spectral image was produced. The Residual Spectral Unmixing (RSU) procedure was applied to the residual spectral image to produce an RSU soil spectrum image. Partial Least Squares Regression (PSLR) model was developed using spectral signatures of a residual soil spectrum image as the independent variable and SOC concentration measured from soil samples as the dependent variable. The PSLR prediction model was used to predict SOC concentration on the RSU soil spectral image. The predicted SOC concentration was then validated with SOC concentration measured from the field plots. A Strong correlation (R2 = 0.82) was obtained between the predicted SOC concentration and the SOC concentration measured from field samples. The PSLR was then used to generate a map of SOC concentration for the Great Fish River Nature Reserve and its environs. Areas with very low SOC concentrations were found in the degraded communal villages, as opposed to the higher SOC values in the protected area. The results confirmed that RS techniques are key to estimating and mapping the spatial distribution of SOC concentration in partial subtropical thicket vegetation. Partial thicket vegetation has a huge influence on the soil spectra; it can influence the prediction of SOC concentration. The use of the RSU approach eliminates partial thicket vegetation cover from bare soil spectra. The residual soil spectrum image contains enough information for the mapping of SOC concentration. The technique has the potential to augment the applicability of airborne imaging spectroscopy for soil studies in the sub-tropical thicket biome and similar environments.
  • Full Text:
  • Date Issued: 2013

Nonlinear effects with a focus on cross phase modulation and its impact on wavelength division multiplexing optical fibre networks

  • Authors: Gamatham, Romeo Reginald Gunther
  • Date: 2013
  • Subjects: Wavelength division multiplexing , Optical communications , Fiber optics
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10948/6302 , vital:21071
  • Description: The demand for faster data transmission is ever increasing. Wavelength division multiplexing (WDM) presents as a viable solution to increase the data transmission rate significantly. WDM systems are based on the ability to transmit multiple wavelengths simultaneously down the fibre. Unlike time division multiplexing (TDM) systems, WDM systems do not increase the data transfer by increasing the transmission rate of a single channel. In WDM systems the data rate per channel remains the same, only multiple channels carry data across the link. Dense wavelength division multiplexing (DWDM) promises even more wavelengths packed together in the same fibre. This multiplication of channels increases the bandwidth capacity rapidly. Networks are looking into making use of technology that will ensure no electronic signal regeneration at any point within the DWDM network. Examples are; reconfigurable optical add/drop multiplexers (ROADM) and optical cross connect (OXC) units. These components essentially enable network operators to split, combine and multiplex optical signals carried by optical fibre. WDM allows network operators to increase the capacity of existing networks without expensive re-cabling. This provides networks with the flexibility to be upgraded to larger bandwidths and for reconfiguration of network services. Further, WDM technology opens up an opportunity of marketing flexibility to network operators, where operators not only have the option to rent out cables and fibres but wavelengths as well. Cross phase modulation (XPM) poses a problem to WDM networks. The refractive index experienced by a neighbouring optical signal, not only depends on the signal’s intensity but on the intensity of the co-propagating signal as well. This effect leads to a phase change and is known as XPM. This work investigates the characteristics of XPM. It is shown that, in a two channel WDM network, a probe signal’s SOP can be steered by controlling a high intensity pump signal’s SOP. This effect could be applied to make a wavelength converter. Experimental results show that the degree of polarization (DOP) of a probe signal degrades according to a mathematical model found in literature. The pump and probe signals are shown to experience maximum interaction, for orthogonal probe-pump SOP vector orientations. This may be problematic to polarization mode dispersion compensators. Additionally, experimental results point out that the SOP of a probe signal is much more active in the presence of a high intensity pump, as compared to the single signal transmission scenario.
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  • Date Issued: 2013

On meshless methods : a novel interpolatory method and a GPU-accelerated implementation

  • Authors: Hamed, Maien Mohamed Osman
  • Date: 2013
  • Subjects: Engineering mathematics , Numerical analysis
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10509 , http://hdl.handle.net/10948/d1018227
  • Description: Meshless methods have been developed to avoid the numerical burden imposed by meshing in the Finite Element Method. Such methods are especially attrac- tive in problems that require repeated updates to the mesh, such as problems with discontinuities or large geometrical deformations. Although meshing is not required for solving problems with meshless methods, the use of meshless methods gives rise to different challenges. One of the main challenges associated with meshless methods is imposition of essential boundary conditions. If exact interpolants are used as shape functions in a meshless method, imposing essen- tial boundary conditions can be done in the same way as the Finite Element Method. Another attractive feature of meshless methods is that their use involves compu- tations that are largely independent from one another. This makes them suitable for implementation to run on highly parallel computing systems. Highly par- allel computing has become widely available with the introduction of software development tools that enable developing general-purpose programs that run on Graphics Processing Units. In the current work, the Moving Regularized Interpolation method has been de- veloped, which is a novel method of constructing meshless shape functions that achieve exact interpolation. The method is demonstrated in data interpolation and in partial differential equations. In addition, an implementation of the Element-Free Galerkin method has been written to run on a Graphics Processing Unit. The implementation is described and its performance is compared to that of a similar implementation that does not make use of the Graphics Processing Unit.
  • Full Text:
  • Date Issued: 2013

Production of recombinant human CD21 and CD23 : towards a better understanding of their interaction

  • Authors: Van Zyl, Dwain George
  • Date: 2013
  • Subjects: Immunoglobulins , Fc receptors
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10365 , http://hdl.handle.net/10948/d10211135
  • Description: The prevalence of allergic diseases has dramatically increased over the last three decades. Presently, it is estimated that 20-30 per cent of the developed world suffers from allergic diseases. The majority of allergic diseases are rooted in the activities of IgE; an immunoglobulin which exerts its effector functions by interacting with a network of proteins. This network includes its low affinity receptor CD23. Cross linking of membrane IgE and CD21 by soluble CD23 results in an increase in IgE synthesis. This marks the interaction between CD23 and CD21 as an attractive therapeutic target. However, details regarding this interaction are inadequate for rational drug design. To obtain a deeper understanding of the CD23-CD21 interaction recombinant human CD21 (SCR1-2 and SCR5-8) and CD23 (16 kD and 25 kDa) were produced. The cloning, expression and purification of recombinant proteins comprised a significant portion of this study. Recombinant CD23 was expressed as inclusion bodies, refolded by rapid dilution and purified by size exclusion chromatography. Conversely, recombinant CD21 was expressed as soluble MBP-fusions and purified with an amylose affinity resin. The interaction between recombinant CD23 and CD21 was analysed by flow cytometry and ELISA experiments. Flow cytometry showed that 16 kDa and 25 kDa CD23 interacted with SCR5-8 to the same extent. Semi-quantitative ELISA experiments showed that both SCR1-2 and SCR5-8 were able to interact with 16 kDa and 25 kDa CD23. This suggests that the binding sites of SCR1-2 and SCR5-8 occur on 16 kDa CD23. Furthermore, since proteins were expressed in E. coli it suggests that the CD23-CD21 interaction does not require glycosylation. Furthermore, considering what is known about the SCR1-2-CD23 interaction from previous NMR studies; i.e. that the C-terminal tail (residues residues 289-298) of CD23 is responsible for binding SCR1-2, indicates that SCR5-8 binds somewhere within the lectin domain of CD23. This indicates that the CD23-CD21 interaction involves C-terminal tail-SCR1-2 and lectin domain-SCR5-8 interactions.
  • Full Text:
  • Date Issued: 2013

Propagating some commonly-used South African medicinal plants with compost and vermitea

  • Authors: Faulconbridge, Steven Craig
  • Date: 2013
  • Subjects: Medicinal plants -- Propagation -- South Africa , Compost -- South Africa
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: vital:10736 , http://hdl.handle.net/10948/d1020316
  • Description: The use of many of South Africa’s medicinal plants has shown marked increase with over 27 million users in South Africa alone. Most plants are still being unsustainably wild-harvested, a major concern for biodiversity conservation. Commercial interest in certain more commonly-used species has increased, with potential to cultivate medicinal plants on a more sustainable basis. Focus has shifted from conventional use of synthetic fertilisers, pesticides and fungicides to more organic methods of plant propagation. Aqueous extract derived from earthworm composted food waste (vermitea) was used to study the germination and rooting success of selected species. Also survival and growth performance of selected plants grown in a medium amended with commercial NPK fertiliser was compared to those grown in the same medium amended with compost and to those grown in the same medium amended with compost with weekly applications of vermitea. No change in germination success was noted. Vermitea showed promising results on the rooting of cuttings. The application of NPK improved growth performance (biomass) significantly for all species tested. However, they had lower root:shoot ratios as well as lower survival rates compared to plants under the compost and compost/vermitea treatments. The improved survival of these plants highlights the potential of these organic treatments on the propagation of selected medicinal plants.
  • Full Text:
  • Date Issued: 2013
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