Showing items 541 - 560 of 1292

Your selections:

Using ambient noise tomography to image the Eastern Cape-Karoo and Karoo regions, South Africa

  • Authors: Bezuidenhout, Lucian John-Ross
  • Date: 2018
  • Subjects: Geometric tomography -- South Africa , Geobiology Geology -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , DPhil
  • Identifier: http://hdl.handle.net/10948/23602 , vital:30585
  • Description: The primary aim of this thesis was to explore the use of ambient seismic noise as a tool to map the subsurface of the Cape-Karoo and Karoo region of South Africa. The Karoo is an ideal laboratory to use ambient seismic signal to map the shallow subsurface, as it is a quiet and pristine environment with a relatively well known geology. Ambient seismic signals were continuously recorded at three independent networks (ArrayA, ArrayB and ArrayC). ArrayA and ArrayB comprised 17 temporary stand-alone seismic stations each and recorded ambient noise wavefields for a ten week period between August and October 2015. ArrayC comprised 19 temporary stand-alone seismic stations, recording ambient seismic noise for a period of six weeks between June and July 2016. ArrayA and ArrayB were installed in the south-eastern Cape-Karoo region, near the town of Jansenville and ArrayC was installed near the Cradock-Tarkastad region of South Africa. This thesis is made up of two separate studies. Firstly, the retrieval and coherency of Rayleigh surface waves extracted from the vertical component recordings. For the first time in the south-eastern Cape-Karoo and Karoo area, estimates of Green’s function from cross-correlating ambient noise data between stations pairs were reconstructed and shown, which can be successfully used to image the subsurface. The stacked cross-correlations between all station pairs show clear arrivals of the Rayleigh surface waves. The group velocities of the Rayleigh waves in the 2 to 7 seconds period range were picked and inverted to compute the 2-D group velocity maps. For ArrayA and ArrayB, the resulting 2-D group velocity maps at different periods resulted in a group velocity model from approximately 2 to 7 km depth, which generally show a high velocity anomaly in the north of the study area, most likely imaging the denser, thick sedimentary basin of the Karoo (Carboniferous-Permian). To the south, the low velocity anomaly likely corresponds to the overlying Jurassic- Cretaceous sequences of the younger Algoa Basin (Uitenhage Group). For ArrayC, the group velocity maps showed high velocity regions, which is consistent with the dolerite sill intrusions in the Karoo and the low velocity structures, which was interpreted as the Karoo sediments. Secondly, the study comprised of characterizing the ambient seismic noise source. The first order analysis of the symmetry of the cross-correlation function showed that, although the ambient noise sources are relatively homogeneously distributed in the study area, most (energetic) of the ambient seismic noise propagates from the coast of South Africa. This was verified by analyzing the azimuthal distribution of the ambient seismic noise.
  • Full Text:
  • Date Issued: 2018

Vanadium-based catalysts for oxidation of organosulfur compounds: synthesis, catalysis and mechanistic studies

  • Authors: Dembaremba, Tendai , Ogunlaja, Adeniyi
  • Date: 2018
  • Subjects: Organosulfur compounds
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/30248 , vital:30909
  • Description: A series of oxidovanadium(IV) complexes based on the ligand, 2-(2’-hydroxyphenyl)imidazole, with substituent groups of different electronegativities on the phenolic para position, were successfully synthesized, characterized and investigated for their catalytic activities in the oxidation of dibenzothiophene (DBT), a typical refractory sulfur compound found in fuel. It was observed from catalytic oxidation studies that the presence of an electron withdrawing group on the phenolic para position of the ligand results in higher catalytic activity. SC-XRD data and DFT studies were used to explain the trends in activity observed. The highest activity was observed with 6.5 nmol of the nitro derivative catalyst [VO(PIMNO2)2] when 100% of 100 mg (0.543 mmol) of DBT was converted to its sulfone derivative dibenzothiophene sulfoxide (DBTO2) using 2.0 mL (1.05 mmol) of t-BuOOH. Potential to immobilize the complex catalysts was demonstrated through the synthesis of oxidovanadium(IV) copolymer nanofibers. The oxidovanadium nanofibers were successfully employed in the oxidation of sulfur compounds in a real fuel sample (diesel 500) which were then removed through solvent extraction using acetonitrile to give clean fuel. SC-XRD, EPR and UV-Vis spectroscopy were instrumental in providing insight into the mechanism of the catalyzed reaction. Vanadium oxides were also investigated as a cheaper alternative for the catalytic oxidation reaction. Phases of different vanadium oxides were synthesized by calcining NH4VO3 in air at different temperatures with an intention to investigate them for their catalytic activities. The catalyst obtained from calcination at 600⁰C was predominantly the orthorhombic phase of V2O5. Potential to immobilize the vanadium oxides was demonstrated using a silica support where NH4VO3 was impregnated onto silica and calcined in air at 600⁰C. The catalyst showed good potential in the oxidation of DBT to DBTO2, with 10 mg (43.9 μmol) of catalyst successfully converting 100% of 100 mg (0.543 mmol) DBT to DBTO2 using 2.0 mL (1.05 mmol) of t-BuOOH. The catalyst was also employed for a real fuel sample (diesel 500) with good results. The mechanistic aspects of vanadium oxides were also investigated in this study.
  • Full Text:
  • Date Issued: 2018

Synthesis and biolgical screening of potential plasmodium falciparum DXR inhibitors

  • Authors: Adeyemi, Christiana Modupe
  • Date: 2017-04
  • Subjects: Plasmodium falciparum , Enzyme inhibitors , Malaria , Antimalarials , Drug development , Malaria -- Chemotherapy , Isopentenoids -- Synthesis , Fosmidomycin , 1-Deoxy-D-xylulose 5-phosphate
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/61790 , vital:28060
  • Description: The non-mevalonate isoprenoid pathway, also known as the 1-deoxy-D-xylulose-5- phosphate DXP pathway, is absent in humans, but present in the anopheles mosquito responsible for the transmission of malaria. DXP reductoisomerase - a key enzyme in the DXP pathway in Plasmodium falciparum (PfDXR) has been identified as a target for the design of novel anti-malarial drugs. Fosmidomycin and its acetyl analogue (FR900098) are known to be inhibitors of PfDXR and, in this study, synthetic variations of the fosmidomycin scaffold have led to four series of novel analogues. Particular attention has been centred on the introduction of various substituted benzyl groups in each of these series in order to occupy a recently discovered vacant pocket in the PfDXR active-site and thus enhance ligand-enzyme binding. In the process 160 ligands and precursors have been prepared, no less than 119 of them novel. Fistly, a series of C-benzylated phosphonate esters and phosphonic acids were synthesised, in which the fosmidomycin hydroxamate Mg2+- coordinating moiety was replaced by an amide funtionality and the number of methylene groups in the “hydrophobic patch” between the phosphonate and the hydroxamate moiety was decreased from two to one. Several approaches were explored for this series, the most successful involving reaction of 3- substituted anilines with a-bromo propanoic acid in the presence of the coupling agent 1,1'- carbonyldiimidazole (CDI), followed by Michaelis-Arbuzov phosphonation using triethyl phosphite. Reaction of the resulting chiral phosphonate esters with bromotrimethylsilane gave the corresponding phosphonic acids in good yields. In order to obviate chirality issues, a second series of potential “reverse” fosmidomycin analogues was synthesised by replacing the methylene group adjacent to the the phosphonate moiety with a nitrogen atom. Deprotonation, alkylation and phosphorylation of various amines gave diethyl #-benzylphosphoramidate ester intermediate. Aza-Michael addition of these intermediates, followed by hydrolysis gave the corresponding carboxylic acids which could be reacted with different hydroxylamine hydrochloride derivatives to afford the novel hydroxamic acid derivatives in good yields. Thirdly, a series of a novel #-benzylated phosphoramidate derivatives were prepared as aza- FR900098 analogues. Alkylation of different amines using bromoacetalde-hyde diethylacetal gave a series of N-benzyl-2,2-diethoxyethylamine compounds, which were then elaborated via a futher six steps to afford novel #-benzylated phosphoramidate derivatives. Finally, in order to ensure syn-orientation of the donor atoms in the Mg - coordinating group and, at the same time, introduce conformational constraints in the ligand, the hydrophobic patch and the hydroxamate moiety were replaced by cyclic systems. Several approaches towards the synthesis of such conformationally constrained phosphoramidate analogues from maleic anhydride led to the unexpected isolation of an unprecedented acyclic furfuryl compound, and 1H NMR and DFT-level theoretical studies have been initiated to explore the reaction sequence. A series of #-benzylated phosphoramidate derivatives containing dihydroxy aromatic rings (as the conformationally constrained groups) to replace the hydroxamate moiety, were successfully obtained in six steps from the starting material, 3,4-dihydroxylbenzaldehyde. While in vitro assays have been conducted on all of the synthesised compounds, and some of the ligands show promising anti-malarial inhibitory activity - most especially the conformationally constrained cyclic #-benzylated phosphoramidate series. Interestingly, a number of these compounds has also shown activity against T.brucei - the causative agent of sleeping sickness. In silico docking studies of selected compounds has revealed the capacity of some of the ligands to bind effectively in the PfDXR active-site with the newly introduced benzyl group occupying the adjacent vacant pocket. The physico-chemical properties of these ligands were also explored in order to predict the oral-bioavailability. Most of the ligands obeyed the Lipinski rule of 5, while QSAR methods have been used in an attempt to correlate structural variations and calculated molecular properties with the bioassay data. , Thesis (PhD) -- Faculty of Science, Chemistry, 2017
  • Full Text:
  • Date Issued: 2017-04

A best practice e-learning environment for software training

  • Authors: Esterhuyse, Maxine Pier
  • Date: 2017
  • Subjects: Internet in education Computer-assisted instruction Web-based instruction -- Education
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/12165 , vital:27039
  • Description: The incorporation of best practice in e-learning environments can increase the probability of success for companies and learners alike. By identifying and understanding the barriers that potential learners may face when interacting with e-learning products, the potential for e-learning failure may be alleviated. There are a variety of benefits that may be realised by companies incorporating e-learning opportunities into their management strategies. However, certain pedagogical principles, metrics and components need to be investigated and implemented in order for a corporate e-learning environment to be successful. The aim of this research is to prototype and evaluate a practical e-learning environment for software training (eLESTP) with e-learning components consisting of interactive learning objects that can guide the development and management of online training in the corporate context. The eLESTP is based on a theoretical contribution that is conceptualised in the form of an e-learning environment for software training (eLESTT). Hence, this study followed a research methodology that is appropriate for educational technologies, namely the Design-Based Research (DBR) methodology, which was applied in iterative cycles. Quantitative and qualitative data was collected by means of a case study, interviews, a focus group and survey. The proposed eLESTP underwent several iterations of feedback and improvement and the result is a real-world solution to the problem at hand. With the purpose of determining the success of corporate e-learning, the barriers and critical success factors for e-learning as well as evaluation criteria were explored. Interviews, a focus group and a survey were conducted in order to validate the investigated literature in a real-world context. Informal interviews enabled a better understanding of the organisational context of this study. The focus group was conducted with customers who were undergoing face-to-face training using conveyancing software developed by Korbitec. Many of the issues faced by learners identified in literature regarding e-learning in developing countries were identified by the participants from the case study. An e-learning survey was used to gather information regarding the intention of Korbitec’s customers to use e-learning as well as their satisfaction with using e-learning. From the survey, it was found that respondents were positive regarding intention to use and satisfaction toward e-learning usage. DBR Cycle 1: Problem Investigation and Proposal entailed the initial problem investigation by conducting a literature review, focus group and survey. DBR Cycle 2: Design Alternative 1 of this study involved a design alternative for eLESTP, namely Prototype 1. DBR Cycle 3: Design and Evaluate Alternative 2 involved the design and prototyping of Prototype 2 for eLESTP as well as the improvement of Prototype 2 through sub-cycles of testing and refinement. The suggestions for improvement were obtained from the relevant stakeholders at Korbitec who are content developers and subject-matter experts. The criteria used to evaluate the success of eLESTP, including its e-learning components, were synthesised and adapted from literature and a new set of evaluation criteria for e-learning environments in software training contexts was proposed. The evaluated eLESTP consists of the technology basis of the Modular Object Oriented Dynamic Learning Environment (Moodle), design guidelines for e-learning components, certification and competency-based training, pedagogical principles and best practice. Overall, eLESTP was positively received by various evaluator groups in formative and summative evaluations. The research results indicate that the use of an e-learning environment for software training purposes was useful and necessary. In support of this Masters dissertation, the following three conference papers have been published and presented at one local conference and two international conferences. In addition, an article has been published in an accredited journal: 1. IDIA 2015, Conference Paper – Zanzibar (Tanzania); 2. Conf-IRM 2016, Conference Paper – Cape Town (South Africa); 3. MCIS 2016, Conference Paper – Cyprus (Europe); and 4. IJIKM 2016, Journal Article.
  • Full Text:
  • Date Issued: 2017

A comparison of the comfort properties, measured with a sweating manikin (WalterTM), of clothing containing different fibres

  • Authors: Britz, Lizaan
  • Date: 2017
  • Subjects: Textile chemistry Cotton fabrics , Cotton textiles
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/14752 , vital:27842
  • Description: The main objective of the present study was to determine the relative role and importance of worsted suiting fabric fibre blend vis-à-vis fabric structural parameters, on the comfort related properties of 12 clothing ensembles, each comprising a different man’s suit, but the same wool/nylon underwear and cotton shirt. To achieve the objective, the comfort related properties, namely thermal resistance (Rt) and water vapour resistance (Ret) and water vapour permeability index (Im), of the clothing ensembles, as determined by means of WalterTM, a thermal sweating fabric manikin, were subjected to multi-linear and multi-quadratic analysis, as dependent variables, with the various suiting fabric parameters, namely weight, thickness, density, porosity, air permeability and wool content, as independent variables. It was found that the multi-quadratic regression analysis was able to best explain the observed differences in the clothing ensemble comfort related properties, in terms of the differences in suiting fabric properties. The regression analyses were used to isolate and quantify the effects of the various fabric and fibre content variables on the above mentioned comfort related properties of the various clothing ensembles. This study indicated that the suiting fabric structural properties (notably air permeability), had a more significant influence than either fibre blend or suiting fabric, as measured on WalterTM, a thermal sweating fabric manikin.
  • Full Text:
  • Date Issued: 2017

A fibre utilisation comparison of two harvesting systems in eucalyptus grandis in the Kwa-Zulu natal forestry region of South Africa

  • Authors: Nxumalo, Sikhumbuzo Khethukuthula , McEwan, Andrew
  • Date: 2017
  • Subjects: Eucalyptus grandis -- South Africa -- KwaZulu-Natal Harvesting -- South Africa -- KwaZulu-Natal
  • Language: English
  • Type: Thesis , Masters , Degree
  • Identifier: http://hdl.handle.net/10948/20592 , vital:29331
  • Description: Global timber demand is increasing as the level of technology continues to improve in many parts of the world. There needs to be more focus on renewable energy resources which will have a reduced negative impact on the environment. There is limited land area for timber plantations and this necessitates effective use of land from both an environmental and a commercial point of view. This research aimed at quantifying and comparing the fibre utilisation of two harvesting systems operating in Eucalyptus grandis pulpwood plantations. This was done using a general linear model, whereby the fibre loss areas were identified and used as the dependent variables, whilst diameter at breast height (DBH), site and harvesting systems were used as the independent variables. The research also aimed at determining the amount of fibre each system could recover, where fibre is lost or gained in each harvesting system and also whether one of the harvesting systems is able to recover more fibre than the other. The research investigated two harvesting systems in Eucalyptus grandis pulpwood plantations. These systems consisted of the full tree chain flail delimber debarker and chipper (FT CFDD&C) system and the cut-to-length (CTL) motor-manual system. These systems operated close to one another to ensure that the research was carried out on comparable paired plots. Two sites were identified to carry out research after a pilot study was done to test the feasibility. Using the FT CFDD&C system, trees were felled by means of a feller buncher. A grapple skidder was used for extraction to the landing, a chain flail delimber debarker (CFDD) for debarking and debranching and a roadside chipper for converting the boles into chips. The second CTL motor-manual system was modified into a tree length system to suit the conditions of the study due to infield chipping requiring longer lengths. Therefore, trees were felled with a chainsaw and debranched and topped infield before tree lengths were extracted to the landing site with the grapple skidder. The CFDD was used for debarking and the chipper converted boles into chips.
  • Full Text:
  • Date Issued: 2017

A new synthetic approach for preparation of Efavirenz

  • Authors: Chada, Sravanthi
  • Date: 2017
  • Subjects: Antiretroviral agents , Asymmetric synthesis , Enzyme inhibitors , HIV (Viruses) -- Enzymes
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10948/15512 , vital:28265
  • Description: Efavirenz, a drug that is still inaccessible to millions of people worldwide, is potent non nucleoside reverse transcriptase inhibitor (NNRTI), is one of the preferred agents used in combination therapy for first-line treatment of the human immunodeficiency virus (HIV). NNRTIs attach to and block an HIV enzyme called reverse transcriptase, by blocking reverse transcriptase; NNRTIs prevent HIV from multiplying and can reduce the amount of HIV in the body. Efavirenz can't cure HIV/AIDS, but taken in combination with other HIV medicines (called an HIV regimen) every day helps people with HIV live longer healthier lives. Efavirenz also reduces the risk of HIV transmission and can be used by children who are suffering from HIV/AIDS. All the above therapeutic uses of efavirenz prompted us to identify the novel and hopefully cost efficient synthetic methodology for the preparation of efavirenz. In this thesis a new synthetic method for asymmetric synthesis of efavirenz is described. This route started from commercially available starting materials and it is first established in traditional batch chemistry and further the parameters transferred to a semi continuous flow protocol for optimization.
  • Full Text:
  • Date Issued: 2017

A sedimentological and structural study of the lower Ecca Group, with a focus on facies analysis of the Collingham Formation, north of Grahamstown, SE Karoo Basin, South Africa

  • Authors: Slamang, Shereen
  • Date: 2017
  • Subjects: Formations (Geology) -- South Africa -- Grahamstown Facies (Geology) -- South Africa -- Grahamstown
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/21099 , vital:29439
  • Description: A study of the Collingham Formation was conducted in the area of the Ecca Pass and Committees Drift Road some 20km north of Grahamstown, Eastern Cape. The study incorporates outcrops of the lower Ecca Group, with a focus on the Collingham Formation. The structural and sedimentological characteristics have been documented, and a detailed description and facies outcrop characterization of the Collingham Formation has been undertaken. The combined thickness of the Prince Albert (~55m), Whitehill (~12m), and Collingham (~20m) Formations is approximately 85m. These formations are composed of fine grained parallel laminated mudrocks of mostly silt- and clay-size particles. A general north-easterly dip direction is recorded with three prominent joint directions striking NNE, NNW, and ESE. Intense small scale folding is evident in the Whitehill Formation, and is likely linked to local décollement structures; while north-verging duplex faults in the Prince Albert Formation is possibly linked to a sole thrust/detachment fault rooted in rocks of the Cape Supergroup. The foreland model has been proposed for these deformational structures. Six lithofacies have been recognised in the Collingham Formation, namely; claystone facies, mudstone facies, siltstone facies, chert facies, tuff facies, and shale facies. The Collingham Formation is comprised of an upward fining sequence of sediments; seen from the gradual change from siltstone facies in the lower layers, to mudstone facies, and claystone facies in the upper layers. This was created in a delta environment whereby clay particles were held in suspension in a hypopycnal mouth bar, and slowly settled to form claystone facies. An influx of sediment caused silt particles to settle further out to sea under the influence of gravity in a hyperpycnal mouth bar, thereby forming siltstone facies. Mudstone facies formed as the sediment supply gradually depleted, subsequently reducing the concentration of silt particles. The dominance of clay particles present suggests deposition to have occurred in tranquil waters, in a possible intracratonic basin setting, where the water depth is known to be a lot shallower. An upward decrease in organic content is seen by the colour change of mudrocks from dark grey near the base to dark green grey in the upper layers. Chlorite is commonly found in thin section, SEM, and XRD, and is an indication that the formation was later subject to low grade greenschist facies metamorphism.
  • Full Text:
  • Date Issued: 2017

A smart home environment to support safety and risk monitoring for the elderly living independently

  • Authors: Chiridza, Tongai
  • Date: 2017
  • Subjects: Multisensor data fusion , Raspberry Pi (Computer) -- Programming Adaptive computing systems
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/14851 , vital:27880
  • Description: The elderly prefer to live independently despite vulnerability to age-related challenges. Constant monitoring is required in cases where the elderly are living alone. The home environment can be a dangerous environment for the elderly living independently due to adverse events that can occur at any time. The potential risks for the elderly living independently can be categorised as injury in the home, home environmental risks and inactivity due to unconsciousness. The main research objective was to develop a Smart Home Environment (SHE) that can support risk and safety monitoring for the elderly living independently. An unobtrusive and low cost SHE solution that uses a Raspberry Pi 3 model B, a Microsoft Kinect Sensor and an Aeotec 4-in-1 Multisensor was implemented. The Aeotec Multisensor was used to measure temperature, motion, lighting, and humidity in the home. Data from the multisensor was collected using OpenHAB as the Smart Home Operating System. The information was processed using the Raspberry Pi 3 and push notifications were sent when risk situations were detected. An experimental evaluation was conducted to determine the accuracy with which the prototype SHE detected abnormal events. Evaluation scripts were each evaluated five times. The results show that the prototype has an average accuracy, sensitivity and specificity of 94%, 96.92% and 88.93% respectively. The sensitivity shows that the chance of the prototype missing a risk situation is 3.08%, and the specificity shows that the chance of incorrectly classifying a non-risk situation is 11.07%. The prototype does not require any interaction on the part of the elderly. Relatives and caregivers can remotely monitor the elderly person living independently via the mobile application or a web portal. The total cost of the equipment used was below R3000.
  • Full Text:
  • Date Issued: 2017

A technical and economic evaluation of a passive underground mine-water purification system (PUMPS): a geothermally powered geo-engineering system designed for in-situ bio-remediation of acid mine water

  • Authors: Ntholi, Thakane Thato Prudence
  • Date: 2017
  • Subjects: Water -- Purification -- South Africa Water -- Purification -- Biological treatment , Mine water -- South Africa -- Evaluation Acid mine drainage -- South Africa Environmental geochemistry -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , DPhil
  • Identifier: http://hdl.handle.net/10948/19586 , vital:28900
  • Description: PUMPS mimics natural geothermal vents as a conceptual model designed for the remediation of acid mine water (AMW) in voids of abandoned gold mines of the Witwatersrand Basin in South Africa. In this system, a reaction chamber containing Desulfotomaculum kuznetsovii sulfate reducing bacteria will be set at the bottom of a 3-4 km deep mine that will be flooded. A geothermal system with at least one (1) doublet will be drilled from the bottom of the mine to the depth of 8km, where the temperatures are sufficient for geothermal energy harvesting. AMW, used as a geothermal fluid, will be pumped down the injection well and circulate through hot rock. The hot water is then used to generate electricity and then channelled into the reaction chamber to undergo bio-remediation. Following treatment, the water flows back into the mine voids where it will improve the quality of untreated AMW through dilution. Eventually, the mine will be flooded with clean water that can be stored underground and/or pumped up to surface for social and ecosystem services. Following an introduction and proof of concept for the PUMPS, the research builds further on the technical and economic evaluation of the PUMPS in order to assert its viability and sustainability. The technical viability includes testing the ability for Desulfotomaculum kuznetsovii to survive in high pressure condition; quantifying the amount of energy that can be drawn from the geothermal reservoir; determining the placement and scheme of the geothermal wells; and, finally, developing a robust economic model of the system. Experiments show that Desulfotomaculum Kuznetsovii can tolerate high pressure conditions in of at least 100bar at their ideal sulfate reducing temperature of 63°C. Geochemical modelling shows that AMW can be used effectively as a geothermal fluid for PUMPS. To achieve highest efficiency and minimal fluid loss, the geothermal wells should be placed along the SSE-NNW direction, based on the known stress field across the Witwatersrand Basin. With a flow rate of 30l/s the energy drawn from the geothermal reservoir is sufficient to drive PUMPS and the surplus energy is determined by the volume of AMW treated per day. All results indicate that the PUMPS is technically and economically viable. The economic model shows that the value and viability of the PUMPS is best reflected with a comprehensive inclusion of potential revenue (for example from chemical solution mining of deep seated gold) and financial/environmental incentives.
  • Full Text:
  • Date Issued: 2017

Adjusting lion diet estimates to assess lion impacts on small prey in Addo Elephant National Park

  • Authors: Gerber, Amarein Judith
  • Date: 2017
  • Subjects: Wildlife conservation -- South Africa -- Addo Elephant National Park , Lion -- Behavior -- South Africa -- Addo Elephant National Park Lion -- Conservation -- South Africa -- Addo Elephant National Park
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/14311 , vital:27542
  • Description: Populations of small prey species (< 92 kg) can be regulated by competition, habitat-mediated responses, climate change, disease and predation. Populations of small prey species have declined in the Addo Elephant National Park Main Camp Section since the reintroduction of apex predators (lion and spotted hyaena). One possible explanation is predation by lion and spotted hyaena. However, small prey species are not generally considered preferred prey items of these predators, hence their contribution to predator diets needs to be explored. Global Positioning System (GPS) cluster analysis has emerged as a viable approach to locate lion kills for lion diet estimation in AENP, however this technique is known to bias diet estimates to large prey species. Understanding the impact of lion predation on populations of small prey in Main Camp therefore requires better estimates of lion diets. This study investigated the potential underestimation of small prey species in lion diet estimates by combining the data from scat analysis and carcasses located at GPS clusters. The adjusted lion diets were then used to investigate if the impact of lion predation could explain declines in small prey, by relating lion prey preferences to prey population trends in Nyathi. Using the results from Nyathi, it could then be inferred whether lions could have been responsible for the declines observed in Main Camp. Six GPS-collared lions provided location data used to construct individual movement paths, along which spatio-temporal clusters of GPS locations (n = 4896) were identified for ground investigation. Carcasses (n = 643) were recorded at the GPS clusters and scats (n = 256) were collected at GPS clusters with or without carcasses. Data from the located carcasses and scat collections were then used to create a history of feeding events for each collared lion in Main Camp-Colchester and Nyathi from a) carcasses alone or b) a combination of scats and carcasses, based on an estimated short and long lion throughout period. Relative prey availability was estimated based on camera trapping in Nyathi in high lion, low lion and no lion use areas, as lions may encounter some prey species more than other prey species. Jacobs’ index prey preference was used to investigate the importance of prey species to lion diets at three landscape scales: 1) Nyathi, 2) lion UD and 3) core lion UD. Lastly, prey population trends were investigated in Nyathi to provide an indication of possible changes in prey populations. Large prey species dominated the adjusted diets of lions in Main Camp-Colchester and Nyathi. However, when comparing the GPS carcass-derived lion diet estimate to the combined lion diet estimate, small prey were underestimated more often than large prey in the GPS carcass-derived lion diet estimate. Missed feeding events were therefore a function of prey body size. In addition, missed feeding events were also representative of the lion diets based on carcasses, with the tendency for species more often consumed to be missed more often in the diet record. However, even though small prey species were underestimated, they represented the minority of species consumed by lions and were predominantly avoided by lions in Nyathi. Lion prey preferences thus did not correlate to the declines in small prey species in Naythi, suggesting other potential drivers are important for small population trends in Nyathi. Lion predation cannot be ruled out as a driver of the decline in small prey species in Main Camp, due to different ecological conditions (e.g. vegetation density) in Main Camp compared to Nyathi, during the observed small prey population declines. Lion prey preferences in Nyathi revealed fine-scale variations in species specific preferences by lions, as well as site-specific differences in prey preferences when compared to published lion prey preference meta-analyses. These findings suggest that metaanalysis studies should be used as a guideline from which hypotheses about local predatorprey interactions can be developed rather than as an absolute measure of prey preference.
  • Full Text:
  • Date Issued: 2017

Agribusiness challenges to effectiveness of contract farming in commercialisation of small-scale vegetable farmers

  • Authors: Khapayi, Musa
  • Date: 2017
  • Subjects: Farms, Small -- South Africa -- Eastern Cape , Agriculture -- Economic aspects -- South Africa -- Eastern Cape , Agricultural industries -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Doctoral , DTech
  • Identifier: http://hdl.handle.net/10948/13981 , vital:27363
  • Description: The spread of contract farming in South Africa in recent years has provoked an ideological debate in literature. Linking small-scale vegetable farmers with lucrative agricultural markets through agribusiness value chains is seen as one of the foremost emerging agricultural practices to develop the subsistence farming sector into a mainstream economic sector – thereby revitalising the rural economy and alleviating poverty levels in the developing rural areas of South Africa. However, the challenges agribusiness and small-scale farmers experience in contract farming engagement and the prospects for enhancing the inclusion of small-scale farmers into modern value chains remain open to debate – two decades after transition to democracy. Yet the factors and mechanisms influencing the effective application of contract farming in the transition to commercial farming by small-scale farmers have not been thoroughly explored in South African research. Despite the efforts and the substantial investments made and the various policies and initiatives instigated to fast-track the linkages of small-scale farmers into high-value markets, the success stories of previously disadvantaged farmers operating in commercial agri-food chains are rare. Given the millions of small-scale farmers in former homelands alone, the negligible number of small-scale farmers successfully operating in commercial agri-food chains shows that the objectives to enable small-scale farmers to improve their livelihoods through participation in commercial agri-food chains have not yet been met. The broad objectives of the study were therefore to investigate the agribusiness challenges inherent in contract farming and the conditions and incentives required by agribusiness firms to engage small-scale vegetable farmers in contract farming programmes. Furthermore, the study examined the role played by the South African government to reduce the high transaction costs incurred by agribusinesses when engaging small-scale farmers in contractual arrangements. The Amathole and Sarah Baartman (formerly Cacadu) district municipalities in the Eastern Cape Province of South Africa were chosen as the composite survey area for this study. A predominantly qualitative research approach was applied to gather data on the phenomena under study. The following methodologies and research instruments and tools were selected. Firstly – as the secondary component of the research – a systematic review of literature to date was conducted to guide the empirical research and primary methodology. Secondly, the empirical component of the study comprised a questionnaire survey, unstructured interviews and focus group discussions. The questionnaire survey was used to collect data from the agribusiness firms in the area surveyed concerning the following aspects: the significant determinants of contract farming, the incentives required by the agribusiness firms to engage small-scale vegetable farmers in their contract farming programmes and the challenges faced by agribusiness firms in their interaction with small-scale farmers in contractual arrangements. Unstructured interviews were used to gather data from officials at each of the three levels of government – the Department of Rural Development and Land Reform nationally, Department of Agriculture and Land Reform provincially and (at local government level) two district municipalities – on the role played by government to reduce the high transaction costs incurred by agri-firms when procuring agricultural raw materials from small-scale vegetable farmers. Focus group discussions were conducted with small-scale farmers regarding their perspective on working with agribusiness firms and to establish the distinguishing characteristics of small-scale farmers in the area surveyed. Relevant policy documents collected from two of the three representative groups of the study population, i.e. agribusiness personnel and government officials, provided the essential context. The study revealed a limited number of contract farming business linkages between small-scale vegetable farmers and agribusiness firms in the survey area. Those that do exist are problematic to both the agribusiness firms and the small-scale farmers. It emerged that the contract farming environment in the area surveyed is highly polarised and characterised by a fundamental conflict of interest between agribusiness and farmer. Among the divergent key factors inhibiting contract farming engagement were a lack in terms of quality seeds, trust, entrepreneurial skills and formal contract agreements. Asset endowment (both land and non-land assets) was found to be significant pre-selection determinants in the farmer’s capacity to be contracted. Access to innovative technology, as well as government incentives such as production inputs, were found to be critical to agribusiness firms to engage smallscale farmers in their contract farming programmes. Government assistance in terms of high transaction costs to agribusiness firms working with large groups of small-scale farmers was found to be essential but inadequate under current policy. This impacts directly on the effectiveness and promotion of contract farming. Furthermore, the current results corroborate the findings of numerous South African studies in the vast body of worldwide research. Firstly, lack of land and non-land assets continue to be major impediments to the direct participa-tion of small-scale farmers in contract farming programmes and, secondly, the transaction and market information costs incurred by agribusiness prevent the participation of less endowed farmers in contract farming programmes. Conducted within the interpretivist paradigm, the explorative research identified wide-ranging challenges in the relationship between agri-business and small-scale farmers which directly impact the effective-ness of contract farming as a development and agrarian reform strategy. Despite their problematic relationship, however, agribusiness and small-scale contract farmers were in agreement that the government needs to expand its support for agri-firms to incentivise greater numbers of small-scale farmers having the opportunity to achieve commercial status through contract farming. The study therefore recommends a collaborative partnership between private firms and government, with state support through revised policies and development programmes. These amendments are crucial to enhancing the engagement of small-scale vegetable farmers in lucrative agri-food chains.
  • Full Text:
  • Date Issued: 2017

An exploration of the processes that encourage HIV and AIDS affected Basotho female adolescent resilience in Sedibeng West in the Vaal Triangle area of the Gauteng Province

  • Authors: De Lange, Une
  • Date: 2017
  • Subjects: Resilience (Personality trait) in adolescence -- South Africa -- Gauteng Teenage girls -- South Africa -- Gauteng
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: http://hdl.handle.net/10948/22220 , vital:29875
  • Description: This study aimed to explore processes encouraging resilience in HIV and AIDS affected Basotho female adolescents in Sedibeng West in the Vaal Triangle area of the Gauteng province; and to identify guidelines to help these individuals to get through their adversities in constructive ways. By using purposive sampling (a non-probability sampling method), 61 high risk, high resilient HIV and AIDS affected Basotho female adolescents in Sedibeng West were identified to participate in the research An extensive literature review revealed the following gaps with regard to the topic of this study: • Shortage of literature regarding the effects that HIV and AIDS have on Basotho female adolescents and how these adolescents cope with these challenges; • Lack of focus on resilience of specific cultural adolescent groups; • Lack of focus on processes that encourage resilience in adolescents; • Need for qualitative studies of resilience and visual qualitative studies in particular. Consequently, a qualitative, visual phenomenological study was done where data was collected by a multi-dimensional data gathering method consisting of open-ended questionnaires, drawings and semi-structured interviews. The findings revealed that HIV and AIDS affected all participants in a substantial way. The following three main processes encourage resilience in Basotho female adolescents: Benefitting from constructive bonds; Making meaning; and Acting constructively. Furthermore, Spiritual beings and Mothers were primarily identified as figures of strength and support during adolescents’ adversity. Based on the findings, the researcher recommends that: • The Department of Education include all aspects concerning HIV and AIDS, as well as aspects concerning Religion and Spirituality in the Life Skills curriculum without making any preference of religion; • a mother figure should be established in every child’s life at a very young age, preferably as early as birth; • young people be taught skills and strategies to build interpersonal relationships and attachment bonds to significant others; • families and schools empower individuals with skills to find meaning in adversity • parents and family members model constructive regulation of behaviour to adolescents.
  • Full Text:
  • Date Issued: 2017

An in vitro evaluation of anti-breast cancer activity of novel, heterocyclic aromatic compounds in combination with curcumin

  • Authors: Pereira, Melanie Claire
  • Date: 2017
  • Subjects: Breast -- Cancer Heterocyclic compounds
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10948/20416 , vital:29284
  • Description: Nearly two thirds of breast cancers are classified as estrogen receptor positive. Estrogen receptor (+) breast cancer is usually treated with anti-estrogen therapy, using Tamoxifen as the primary standard of treatment. Unfortunately, resistance to Tamoxifen is known to occur after 1 to 3 years of Tamoxifen therapy. For this reason, improved treatment strategies for ER (+) breast cancer are urgently needed. The general toxicity exerted by most anti-cancer drugs on proliferating cells, as well as some normal cells, restricts their therapeutic use. Novel cytotoxic agents developed with unique mechanisms of action have not been therapeutically suitable, since many of these compounds lack tumour selectivity. The adverse effects and the inefficacies of most chemotherapeutic therapies have motivated extensive investigations of alternatives. Numerous studies have demonstrated the advantages of using combination therapy with naturally-derived agents as an alternative, due to the higher therapeutic efficacy; with the added benefit of lower drug usage and reduction in drug-resistance development. An excellent example of a naturally derived and common dietary agent is curcumin, the active constituent of turmeric. Curcumin is known to modulate several signalling pathways in addition to displaying a diverse range of anti-tumour activities against a number of cancer cells. Several reports point to curcumin being beneficial if used in addition to chemotherapeutic drugs. In this study, synthetic aminonaphthoquinone derivatives (coded Rau 008, Rau 010, Rau 015 and Rau 018) were tested individually and in combination with curcumin for the potential as anti-breast cancer agents in different tumour cell lines. Notably, the aminonaphthoquinone class of compounds have shown potential as anti-cancer agents in various tumour cell lines. This study was thus aimed at screening the Rau compounds (and selected combinations with curcumin) for anti-cancer activity using a range of in vitro biological assays, and was not mechanistic in nature. The IC50 values of the individual and combined drugs were determined from dose-response curves using non-linear regression analyses. Synergistic, additive and antagonistic drug interactions were assessed using combination index and isobologram approaches. Based on these interactions, selected drug combinations were then further analysed for their potential anti-estrogenic, cytotoxic, anti-angiogenic and anti-metastatic effects against the ER(-) MDA-MB-231 and ER(+) MCF-7 breast cancer cell lines. The potential anti-cancer effects of the selected drug combinations on other estrogen-responsive models, such as the osteosarcoma (MG-63) and endometrial cancer (HEC-1A) cell lines, were also investigated. Overall, the findings of this study indicated that the sensitivity of the tumour cells to the various test compounds was significantly enhanced when combined with curcumin. For instance, in the presence of curcumin, Rau 008 or Rau 010 reduced the metastatic capability of ER(-) breast cancer cells significantly. The anti-proliferative effect of the Rau 015+curcumin combination was enhanced in ER(+) and ER(-) breast cancer, including oteosarcoma cells, while a combination of Rau 015 and curcumin induced a significant cytotoxic effect in ER(-) breast cancer and endometrial cancer-derived cells. A combination of Rau 018 and curcumin inhibited the proliferation of ER(+) breast cancer, and the combined effect was significantly more enhanced compared to individual treatment. A similar effect was noted in osteosarcoma-derived cells. Further, the Rau 018+curcumin combination exerted a marked cytotoxic and anti-angiogenic effect in ER(-) breast cancer, osteosarcoma and endometrial cancer in addition to inhibiting the attachment of ER(-) breast cancer cells to collagen. Notably, curcumin enhanced the anti-proliferative effect of Tamoxifen in breast cancer (MCF-7 and MDA-MB-231), osteosarcoma and endometrial cancer, and also induced a significant cytotoxic effect against ER(+) breast cancer and osteosarcoma, whilst also reducing the invasive potential of ER(-) breast cancer. A combination of 17β-estradiol and curcumin induced a marked anti-proliferative effect in ER(+) and ER(-) breast cancer, reduced the adhesion of ER(-) breast cancer to laminin, and elicited a significant cytotoxic and anti-angiogenic effect against endometrial cancer. Notably all the selected combinations (except Rau 018 and curcumin) inhibited bone mineralization. These findings point to the vital influence of curcumin in the responsiveness of ER(+) and ER(-) tumours towards the relative test agents. Further, among the Rau+curcumin combinations tested in this study, the anti-cancer activity of Rau 015+curcumin and Rau 018+curcumin appeared to be the most effective in the different cell lines tested. Nonetheless, it appears that a combination of 30 μM Rau 018 with 100 μM curcumin may be more promising as an anti-breast cancer agent against ER(+) and perhaps triple negative breast cancer, and warrants further investigation.
  • Full Text:
  • Date Issued: 2017

An intergrated continuous flow system for the manufacture of biodiesel from waste cooking oil using a heterogeneous acid catalyst and homogeneous base catalyst

  • Authors: Mathe,Francis Matota
  • Date: 2017
  • Subjects: Biodiesel fuels industry , Catalysis , Vegetable oils as fuel
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/44460 , vital:37837
  • Description: The continuous flow production of biodiesel from waste cooking oil (WCO) was investigated in this study. Two different methods of biodiesel production were investigated. The first method involved the acid esterification of free fatty acids (FFAs). In the biodiesel community, the esterification of FFAs in WCO is usually regarded as the pre-treatment stage of biodiesel production using low-quality feedstock.The second method involved the transesterification of triglycerides in WCO. Homogeneous catalysts (NaOH or H2SO4) and heterogeneous catalysts (NaOH/ZnO, Sn/ZnO, Amberlyst-15, Amberlite-IRA 904, Fe/Bentonite and Amberlite IRN 78) were evaluated in the transesterification reaction. Catalyst screening was done using a batch reactor. NaOH gave a high úME content of 96.7% and was chosen as the optimum catalyst for the reaction.The main aim of the project was to make an integrated system that incorporates the esterification and transesterification reaction in the flow production of biodiesel using WCO. The system was developed using the conditions obtained from optimum studies of the separate reactions. Slight adjustments based on further experimental work were made to create an efficient system. The effect of excess methanol from the first step on the concentration of NaOH in the second phase was investigated. It was shown that the excess methanol decreases the concentration of the NaOH and this decreases the úMEs in the final mixture of biodiesel.
  • Full Text:
  • Date Issued: 2017

An Internet of things model for field service automation

  • Authors: Kapeso, Mando Mulabita
  • Date: 2017
  • Subjects: Internet of things Manufacturing processes -- Automation , Automation
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: http://hdl.handle.net/10948/18641 , vital:28698
  • Description: Due to the competitive nature of the global economy, organisations are continuously seeking ways of cutting costs and increasing efficiency to gain a competitive advantage. Field service organisations that offer after sales support seek to gain a competitive advantage through downtime minimisation. Downtime is the time between service requests made by a customer or triggered by equipment failure and the completion of the service to rectify the problem by the field service team. Researchers have identified downtime as one of the key performance indicators for field service organisations. The lack of real-time access to information and inaccuracy of information are factors which contribute to the poor management of downtime. Various technology advancements have been adopted to address some of the challenges faced by field service organisations through automation. The emergence of an Internet of Things (IoT), has brought new enhancement possibilities to various industries, for instance, the manufacturing industry. The main research question that this study aims to address is “How can an Internet of Things be used to optimise field service automation?” The main research objective was to develop and evaluate a model for the optimisation of field services using an IoT’s features and technologies. The model aims at addressing challenges associated with the inaccuracy or/and lack of real-time access to information during downtime. The model developed is the theoretical artefact of the research methodology used in this study which is the Design Science Research Methodology (DSRM). The DSRM activities were adopted to fulfil the research objectives of this research. A literature review in the field services domain was conducted to establish the problems faced by field service organisations. Several interviews were held to verify the problems of FSM identified in literature and some potential solutions. During the design and development activity of the DSRM methodology, an IoT model for FSA was designed. The model consists of:The Four Layered Architecture; The Three Phase Data Flow Process; and Definition and descriptions of IoT-based elements and functions. The model was then used to drive the design, development, and evaluation of “proof of concept” prototype, the KapCha prototype. KapCha enables the optimisation of FSA using IoT techniques and features. The implementation of a sub-component of the KapCha system, in fulfilment of the research. The implementation of KapCha was applied to the context of a smart lighting environment in the case study. A two-phase evaluation was conducted to review both the theoretical model and the KapCha prototype. The model and KapCha prototype were evaluated using the Technical and Risk efficacy evaluation strategy from the Framework for Evaluation of Design Science (FEDS). The Technical Risk and Efficacy strategy made use of formative, artificial-summative and summative-naturalistic methods of evaluation. An artificial-summative evaluation was used to evaluate the design of the model. Iterative formative evaluations were conducted during the development of the KapCha. KapCha was then placed in a real-environment conditions and a summative-naturalistic evaluation was conducted. The summative-naturalistic evaluation was used to determine the performance of KapCha under real-world conditions to evaluate the extent it addresses FSA problems identified such as real-time communication and automated fault detection.
  • Full Text:
  • Date Issued: 2017

Ant colony optimisation-based algorithms for optical burst switching networks

  • Authors: Gravett, Andrew Scott , Gibbon, Timothy B
  • Date: 2017
  • Subjects: Distributed algorithms , Ants -- Behavior -- Mathematical models
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/18939 , vital:28757
  • Description: This research developed two novel distributed algorithms inspired by Ant Colony Optimisation (ACO) for a solution to the problem of dynamic Routing and Wavelength Assignment (RWA) with wavelength continuity constraint in Optical Burst Switching (OBS) networks utilising both the traditional International Telecommunication Union (ITU) Fixed Grid Wavelength Division Multiplexing (WDM) and Flexible Spectrum scenarios. The growing demand for more bandwidth in optical networks require more efficient utilisation of available optical resources. OBS is a promising optical switching technique for the improved utilisation of optical network resources over the current optical circuit switching technique. The development of newer technologies has introduced higher rate transmissions and various modulation formats, however, introducing these technologies into the traditional ITU Fixed Grid does not efficiently utilise the available bandwidth. Flexible Spectrum is a promising approach offering a solution to the problem of improving bandwidth utilisation, which comes with a potential cost. Transmissions have the potential for impairment with respect to the increased traffic and lack of large channel spacing. Proposed routing algorithms should be aware of the linear and non-linear Physical Layer Impairments (PLIs) in order to operate closer to optimum performance. The OBS resource reservation protocol does not cater for the loss of transmissions, Burst Control Packets (BCPs) included, due to physical layer impairments. The protocol was adapted for use in Flexible Spectrum. Investigation of the use of a route and wavelength combination, from source to destination node pair, for the RWA process was proposed for ACO-based approaches to enforce the establishment and use of complete paths for greedy exploitation in Flexible Spectrum was conducted. The routing tuple for the RWA process is the tight coupling of a route and wavelength in combination intended to promote the greedy exploitation of successful paths for transmission requests. The application of the routing tuples differs from traditional ACO-based approaches and prompted the investigation of new pheromone calculation equations. The two novel proposed approaches were tested and experiments conducted comparing with and against existing algorithms (a simple greedy and an ACO-based algorithm) in a traditional ITU Fixed Grid and Flexible Spectrum scenario on three different network topologies. The proposed Flexible Spectrum Ant Colony (FSAC) approach had a markably improved performance over the existing algorithms in the ITU Fixed Grid WDM and Flexible Spectrum scenarios, while Upper Confidence Bound Routing and Wavelength Assignment (UCBRWA) algorithm was able to perform well in the traditional ITU Fixed Grid WDM scenario, but underperformed in the Flexible Spectrum scenario. The results show that the distributed ACO-based FSAC algorithm significantly improved the burst transmission success probability, providing a good solution in the Flexible Spectrum network environment undergoing transmission impairments.
  • Full Text:
  • Date Issued: 2017

Assessing the outcomes and consequences of large carnivore reintroductions to the Eastern Cape, South Africa

  • Authors: Banasiak, Natalia Matgorzata
  • Date: 2017
  • Subjects: Carnivores -- Reintroduction , Wildlife reintroduction
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/11963 , vital:27011
  • Description: Reintroduction is a potentially powerful tool available to conservationists to cope with species population declines. Nonetheless, it is poorly understood and past reviews tend to indicate poor results. Reintroduction, under the sensu stricto IUCN definition, must have a primary objective of conservation; however species can be released to sites in their indigenous range (reintroduction sensu lato) to meet other objectives. The outcomes of these reintroductions s.l need to be assessed to determine how effectively they achieve their varied objectives. A Web of Science review revealed that only 32.1% of 131 publications on reintroduction provided clearly defined success criteria. Using economic, ecological, conservation and problem animal management objectives as reintroduction s.l. drivers, I developed context-dependent success definitions for each objective to use in reintroduction outcome assessments. These success criteria were then used to assess the reintroductions s.l. of large carnivores, namely lion, leopard, cheetah, African wild dog, spotted hyaena, and brown hyaena, to 16 private- and state-owned reserves in the Eastern Cape Province, South Africa. Ecotourism and ecological restoration were the most common objectives for the reintroduction of top predators to these reserves. Overall the reintroductions of large carnivores have been successful in meeting their objectives. Only African wild dogs have failed to establish in the province. Causes of objective-specific failures for the other species in some reserves included introductions of same-sex populations, lack of breeding events and changes in reserve management objectives. Assessments for leopard and brown hyaena were inconclusive due to lack of monitoring data. The reintroduction of large carnivores to the Eastern Cape Province has also resulted in the emergence of human-carnivore conflict on neighbouring properties. Carnivores have reportedly escaped from 8 reserves (61.5% of reserves) in the Eastern Cape. A total of 75 conflict events on 68 neighbouring properties (36.7% of neighbouring properties) have been reported. There is a major gap in research around conflict resulting from carnivore reintroductions and future research is required to fully understand the situation in the province in order to develop effective mitigation methods. An adaptive management approach to reintroductions is encouraged to improve monitoring and ensure reintroductions continue to meet their objectives. Furthermore, emerging consequences, such as human-wildlife conflict, and related mitigation strategies should be incorporated into management of reintroduced populations. Communities surrounding reintroduction sites should be educated on lifting baselines where conflict-causing species are recovering to ensure continued success of reintroduction undertakings. National management plans should be developed for all large carnivore species to improve the conservation value of small, fenced reserves that are typical of South African conservation, through a managed metapopulation approach. Management plans should include social, political, and economic factors that can influence the success of reintroductions and ultimate conservation outcomes.
  • Full Text:
  • Date Issued: 2017

Assessment of the host properties of selected optically pure, racemic and achiral compounds

  • Authors: Jooste, Daniel Victor
  • Date: 2017
  • Subjects: Organic compounds -- Synthesis Cyclic compounds
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/18826 , vital:28735
  • Description: This study focussed on the synthesis and host properties of four different broad categories of potential host compounds, namely optically active and racemic TADDOL [(4R,5R)-α,α,α’,α’-tetraphenyl-1,3-dioxolane-4,5-dimethanol] and derivatives, TTFOL [(3R,4R)-2,2,5,5-tetraphenyltetrahydrofuran-3,4-diol], amino acid ester-derived compounds [(S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol], and compounds derived from xanthone [9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine]. The potential hosts were recrystallized from a range of possible guest species and the resulting solids analysed by 1H-NMR spectroscopy. If inclusion was observed by this technique, the complexes were analysed further using single crystal X-ray techniques and thermal experiments where possible. Competition studies were carried out where these were deemed appropriate. Optically active and racemic TADDOLs were synthesized using L-(+) and DL-(±)-tartaric acid respectively. Two further derivatives were prepared whereby the hydroxyl groups were substituted for chlorine and azide in order to assess the effect of this change on the inclusion ability. Both the optically active and racemic TADDOLs displayed similar host abilities, complexing with guests with 1:1 host:guest ratios as determined through 1H-NMR spectroscopy. Competition experiments showed that both forms of TADDOL exhibited similar guest preferences for pyridine and the methylpyridine isomers. Pyridine however was preferred over 2-methylpyridine by optically active TADDOL while the racemic form preferred this methyl-substituted guest over pyridine. Thermal analysis studies showed, surprisingly, that the TADDOL complexes containing pyridine had higher relative thermal stabilities than those containing the methylpyridines, whether the host was optically active or not. The preference order of these hosts for these guests can, therefore, not be used as a predictor for the relative thermal stability of the complexes. TTFOL was found to include only ethanol, 2-methylpyridine and dioxane from the range of guest species used; the complex with dioxane did not produce X-ray quality crystals. The L-tyrosine derivative, (S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol, was an ineffective host incapable of including any of the guests used in these experiments. The two xanthone derivatives, 9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine each formed complexes with one guest species (morpholine and DMF, respectively).
  • Full Text:
  • Date Issued: 2017

Benthic algal communities of shallow reefs in the Eastern Cape: availability of abalone habitat

  • Authors: Witte, Andrew Dennis
  • Date: 2017
  • Subjects: Reef ecology -- South Africa -- Eastern Cape Abalone fisheries -- Habitat -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/12032 , vital:27021
  • Description: Marine ranching has been identified as an alternative to traditional aquacultural rearing and growing organisms for consumption. In the Eastern Cape, abalone ranching is a new and experimental industry. The aims of the research were to: first develop a GIS model to assist management in site selection for abalone seeding; and secondly to develop and standardize the sampling methodology in order to ground truth the sites, and assist in the monitoring and habitat identification of abalone. The GIS model developed in Chapter 3 was created using an unsupervised classification and fuzzy logic approach. Both vector and raster datasets were utilized to represent 7 different layers. Predominantly satellite imagery was used to classify the different substrate groups according to pixel colour signatures. The basic process was to apply a fuzzy rule set (membership) to rasters which gave an output raster (Fuzzification). The membership output rasters were overlaid which creates a single model output. It was found that model accuracy increased significantly as more layers were overlaid, due to the high variability within each of the individual layers. Model ground-truthing showed a strong and significant correlation (r2 = 0.91; p < 0.001) between the model outputs and actual site suitability based on in situ evaluation. Chapter 4 describes the investigation towards the optimal sampling methods for abalone ranching habitat assessments. Both destructive sampling methods and imagery methods were considered as methods of data collection. The study also evaluated whether quadrat and transects were going to be suitable methods to assess sites, and what size or length respectively they should be to collect the appropriate data. Transect length showed great variation according to the factor assessed. A transect of 15 metres was found to be optimal. Abalone counts showed no significant (p = 0.1) change in the Coefficent of Variance (CV) for transect lengths greater than 15m, and had a mean of 0.2 abalone per metre. Quadrat size showed a significant difference in functional group richness between quadrat sizes of 0.0625m2, and 0.25m2 but no difference between 0.25m2 and 1m2 quadrats for both scape and photographic quadrats. It was also found that between 5 and 10 replicates (p = 0.08) represents the functional groups appropriately using quadrats and that a 0.25m2 quadrat is most suitable for sampling. Chapter 5 describes the benthic community structure of Cape Recife shallow water reefs. Using the standardized methodology previously mentioned, 45 sites were assessed to identify the community structure. These sites were grouped into 5 different groups influenced by depth and substrate, as well as functional group composition according to a Wards classification. The community structure showed that depth and substrate play a significant role (p < 0.05) in the community type. There is also a significant relationship (p < 0.05) between complexity, rugosity, abalone presence and substrate. During this study the basic protocols for site selection and benthic community monitoring have been developed to support the abalone ranching initiative in the Cape Recife area. It has also provided a baseline of the benthic community in the ranching concession area which will be used as a benchmark for future monitoring efforts. The site selection, sampling, and monitoring methods developed during the course of this work have now been rolled out as Standard Operating Procedures for the ranching programme in this area.
  • Full Text:
  • Date Issued: 2017
  • Disclaimer
  • Privacy
  • Copyright
  • Contact