List of Titles

An investigation into the effect of an Extensive Reading Programme on bilingual Grade 3 learners’ reading attitudes in two primary schools in Grahamstown

Authors: Nkomo, Sibhekinkosi Anna
Date: 2017
Language: English
Type: Thesis , Doctoral , PhD , text
Identifier: http://hdl.handle.net/10962/7723 , vital:21289
Description: The focus of this study is to explore formative intervention of a bilingual Extensive Reading Programme (ERP) in two Grade 3 classes in Grahamstown, South Africa. ERP involves access to large quantities of reading materials for pleasure and to reading opportunities (Bamford & Day, 2002; Krashen 2004). The current focus on measurable reading achievement in clearly defined areas such as vocabulary, fluency and comprehension has resulted in reduced attention towards the affective component in relation to literacy development, and links attitudes to reading success. This study helps to fill this gap by examining the effect of an ERP on the reading attitudes of Grade 3 learners. The study draws on Cultural Historical Activity Theory (CHAT) to make sense of learning and social change through mediation, scaffolding, interaction and collaboration learning. The ERP is located within a broad framework of literacy and incorporates a balanced reading approach implemented in an informal reading setting so as to motivate, encourage and nurture reading for enjoyment. This formative intervention used expansive learning cycles to develop a responsive ERP that was implemented and evaluated to investigate its effects on learners’ reading attitude. There were three phases (pre-, during- and post- intervention) that were designed over 31 weeks where rich, qualitative data was collected from questionnaires, observations, learners’ drawings and interviews. To make sense of this data, concepts from CHAT such as contradictions, expansive learning, double stimulation, transformative agency and sustainability were used (Engestrom & Sannino, 2010; Haapasaari & Kerosuo, 2015; Saninno, 2015). In addition, Mathewson’s (1994) reading attitude model addressed the attitudinal aspects of the study whilst a multimodal social semiotic perspective (Kress & Van Leeuwen, 1996) was used to analyse learners’ drawings. The findings of this study demonstrate the effectiveness of combining top-down and bottom-up reading methodologies. In both research sites there was appreciable change in the number of books learners read. Learners also began to volunteer to read and participated in book talks. Through access to a variety of reading materials and reading opportunities, learners demonstrated agency, criticising some ERP practices and modelling new ways, thus claiming and sustaining the reading programme. Being provided with a safe, informal learning context where reading was presented as a social activity, learners gained confidence, engaged in meaningful discussions and improved their self- esteem. Finally, learners continue to access these resources even beyond the research programme.
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Date Issued: 2017

An optimum wind power output model for concentrator augmented wind turbines (CAWTs)

Authors: Shonhiwa, Chipo
Date: 2017
Subjects: Wind power Wind turbines
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10353/8692 , vital:33427
Description: The aim of this study was to develop an optimum wind power output model for concentrator augmented wind turbines (CAWTs), which can operate in low wind speed areas. This study was done using computational fluid dynamics modelling (CFD), theoretical and experimental work. Currently the wind resource is contributing 2.5percent of the global electricity supply and is anticipated to increase to by 2050. Despite this, the contribution to wind energy consumption share by South Africa is still low having just exceeded in 2015. Like many other countries, South Africa agrees that climate change is one of the biggest challenges currently being faced by mankind and acknowledges that tackling it requires collaborative effort from all. The Integrated Resource Plan (IRP 2010-2030) passed in 2010 targets 26.3percent renewable energy contribution to national energy consumption by the year 2030 with 10.3percent coming from wind energy hence contributing to abatement of climate change. 1518percent 1 000 MW Small wind turbines are known for their vital contribution to providing electricity in remote areas. Their power output is mainly influenced by the turbine rotor diameter and wind speed which depend on tower height. A cost benefit analysis conducted basing on increasing wind speed by increasing the turbine tower height revealed that for small wind turbines, the optimal height is . Concentrator Augmented Wind Turbines (CAWTs) are one of several concepts that have been suggested to increase the power output per unit rotor cross-sectional area by increasing the wind speed upstream of the turbine. Although some research effort has been put in this area, the major drawback is that the effect of concentrator geometry and environmental conditions on the aerodynamics and hence ultimate performance of CAWTs is still not clear. Also, the CAWTs systems that have been made so far, do not track the wind resulting in CAWT systems receiving wind from one direction thus limiting their performance. 25 m Wind has a very low energy density in nature implying that a bigger rotor area is required to harness kinetic energy for generation of meaningful electrical energy. This has resulted in higher costs of producing energy from wind than conventional sources of energy such as fossil fuels and hydro. To lower the cost of wind energy, researchers have come up with several initiatives to boost wind turbine power output. A brief review of various concepts that have been used in this study included: history of wind turbines, South Africa’s political will to abatement of climate change, wind resource assessment, power output augmentation, estimation of air density, historical development of CAWTs, fundamental parameters influencing the performance of CAWTs, mathematical modelling of wind turbines and dynamic similarity. Some facts were borrowed from these concepts to come up with the current study and explain the observations. With a view to assess any concept, it is necessary to study the fundamental basis from which it originates. Thus, it was vital to develop a fundamental basis of CAWT performance from which solutions to currently prevailing questions on the relationships among the governing parameters were obtained. The momentum theory of bare wind turbines, which is also found in literature was described. A similar approach was then used for developing the theory of CAWT systems. The theories of concentrator losses, density variation with weather conditions and turbulence modelling were also described. It was of utmost significance to evaluate the wind power potential of the Western part of the Eastern Cape Province to assess whether there would be a need for the concentrator augmented wind turbines (CAWTs) in the province and all other regions with similar or lower wind speeds in the country. In this study, five-year-long, hourly average wind speed series between January 2009 and December 2013 for six weather stations in the western part of the Eastern Cape (Bisho, Fort Beaufort, Graaff–Reinet, Grahamstown, Port Elizabeth and Queenstown) were statistically analysed using the Weibull distribution function. The dimensionless Weibull shape parameter varied from 1.7 to 2.2. All the values were low indicating that there is widely dispersed data. This means that the data tend to be distributed uniformly over a relatively wide range wind speed. Therefore, this has a positive implication on wind power generation in all the studied areas because if a suitable turbine is installed, it would get enough wind speed to run for the greater part of the year. The scale parameter varied between 3.5 and 6.3. The values for all the sites except Port Elizabeth were relatively low implying that the days of high wind speeds are few. Therefore, wind turbines that require high wind speeds for operation are not suitable here.
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Date Issued: 2017

Analysis of a foundational biomedical curriculum: exploring cumulative knowledge-building in the rehabilitative health professions

Authors: De Bie, Gabrielle
Date: 2017
Subjects: Medical education -- Curricula , Human anatomy -- Study and teaching -- Curricula , Physiology -- Study and teaching -- Curricula , Occupational therapy -- Study and teaching -- Curricula , Physical therapy -- Study and teaching -- Curricula , Medical rehabilitation -- Study and teaching -- Curricula , Knowledge, Theory of
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/18617 , vital:22361
Description: This study was motivated by the researcher's experience that students in the rehabilitative health professional programmes were finding it difficult to access fundamental knowledge upon which their professional practices and clinical contexts are based. An important focus of the research was the extent to which cumulative knowledge-building was impacted after the foundational biomedical curriculum became an interdisciplinary programme. The study explored whether the organisation of the interdisciplinary foundational curriculum served the fundamental needs of the professions, and whether, as a matter of social justice, students' access to powerful knowledge was enabled by the form that the fundamental curriculum assumed. This curriculum study at a particular Faculty of Health Sciences foregrounds the structuring, organisation and differentiation of disciplinary knowledge, and reflects a twenty year period that included not only transitions in professional education but also extensive transformation in, and a different approach to, health delivery. At the institution, physiology and anatomy, the biomedical sciences basic to the health professions, underwent disciplinary merging and subsequent altered positioning in curricula. Medicine opted for a problem-based learning approach whereas the rehabilitation health sciences did not. Legitimation Code Theory (LCT) provided the means for analysis of the extent to which interdisciplinary organisation in the foundational curriculum for Physiotherapy and Occupational Therapy enabled integrative, cumulative building of knowledge for professional and clinical contexts. Specialisation and Semantics dimensions of Legitimation Code Theory were used to reveal the principles underpinning practices, contexts and dispositions of Anatomy and Physiology at the Faculty of Health Sciences over a twenty year period post democratisation in South Africa (1994 - 2013). Disciplinary positioning in curriculum prior- and post-merger, were compared and contrasted. LCT were used to characterise the distinctiveness of Physiotherapy and Occupational Therapy at the university including the kind of knowledge and the kind of knower that specialises the different professions, and what is valorised and legitimated for each kind of professional. Semantic gravity was used to explore the expected knowledge recontextualisations in diverse and complex clinical settings for each of the professions. Registered professionals who are clinical educators as well as curriculum designers for clinical studies were interviewed. Profession-specific course outlines were further data sources. The biomedical disciplines Anatomy and Physiology were characterised for their measures of distinction and their respective knowledge-knower structures. Analysis traced each discipline from its strongly classified form in autonomous curricula when there were separate learner-cohorts for physiotherapists and occupational therapists, to post-merger when the disciplines were framed as human biology in an integrated foundational curriculum for a joint cohort of students. Curricular documents for the twenty year period were analysed quantitatively and qualitatively to establish the positioning of Physiology and Anatomy before and after the disciplines merged to a single course of Human Biology. Teaching staff were interviewed for their understanding of what specialises the physiological and anatomical components of the Human Biology curriculum, what they considered as powerful knowledge for the professions, and who they envisaged as the ideal student-knower exiting the basic sciences platform to enter more advanced clinical studies. The degree of context-dependence for meaning-making in the different disciplinary domains and the condensation of meanings inherent in the respective practices and contexts, were analysed. The thesis argues that following the merger Anatomy is preferentially legitimated as powerful knowledge at the expense of Physiology; that the ideal of disciplinary integration is not reached, and that the segmental organisation and structuring of the curriculum negatively impacted on cumulative knowledge-building and application of professional knowledge in the clinical arena. After the merger the disciplines lost their shape, and in particular the hierarchical knowledge structure of Physiology collapsed. By not having access to the necessary disciplinary knowledge structures and their associated practices, students' ability for scaffolding and integrating knowledge into the clinical arena was constrained. The organisation of the current Human Biology curriculum does not facilitate cumulative learning, and in so doing may not contribute to the envisaged graduate professional who is required to practice within a complex and demanding healthcare work environment. The significance of this study conveys that interdisciplinary programmes should be carefully considered, and there is an added imperative in the health professions which ultimately realise treatment of patients. If, aside from interdisciplinary teaching, there are also merged cohorts of participant students, then a sound understanding of the epistemic requirements of each profession is required. Those involved in curriculum development in various fields need to take these recommendations into account to enable cumulative learning and enable epistemological access to powerful knowledge for an increasingly diverse student body.
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Date Issued: 2017

Analysis of the impact of Smallholder Irrigation Schemes on the choice of rural livelihood strategy and household food security in Eastern Cape

Authors: Christian, Mzuyanda
Date: 2017
Subjects: Irrigation -- South Africa -- Eastern Cape Farms, Small -- South Africa -- Eastern Cape Food security -- South Africa -- Eastern Cape
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10353/4813 , vital:28526
Description: Since the end of Apartheid, the South African government has invested substantially in smallholder irrigation schemes, particularly in the former homeland areas. One of the primary goals for establishment of these schemes was to solve food security problems. Sadly, these efforts have not produced the desired results, and poverty has deepened. The question that can be asked is: What is it that makes South African smallholder agricultural sector seemingly impervious to the interventions that government has made in targeting smallholder farmers since the dawn of democracy in 1994? In order to address such a question, a set of structured questionnaires was used to interview 100 smallholder irrigators and 100 non-irrigators using multistage stratified random sampling technique in the Amatole, Chris Hani and OR Tambo District municipalities. Demographic and socio-economic characteristics of smallholder irrigators and non-irrigators around Qamata, Pendu, Tyhefu, Merelles and Ntshongweni irrigation schemes were measured using descriptive statistics. Profitability between the two groups was measured using gross margin analysis (GM). The Probit model was used to determine the factors that affect smallholder farmer‘s choice of participation in irrigation schemes. The impact of irrigation participation on yields, crop sales and food security was estimated using the propensity score matching (PSM) technique. The impact of irrigation participation of smallholder farmer‘s choice of livelihood strategy was estimated using the multinomial regression model. The results showed that male respondents were dominant with a representation of 63 percent and average mean household size of 4 persons with the household head having spent at least 7 years at school. Farming was found to be the major (64 percent) occupation in the study area with an average income of R2 944.52 per cropping season. Both irrigating and non-irrigating smallholder farmers in the study area used improved, fertilizer and tractor for production. Overall, smallholder farmers spent 30.9 percent of their household income on food with irrigators‘food spending lower than those of non-irrigators. The gross margin analysis suggests that the irrigated farmers were in a better position to afford enough food in order to satisfy their household requirement. Findings from the Probit regression and Propensity Score Matching are consistent across the methods, indicating that irrigation participation has a positive influence on crop yields, income and consumption expenditure. Probit regression further showed that age, quality of land, access to credit, access to market, distance to the scheme and membership of another society/association have a positive impact on access and use of irrigation and are significant at p < 0.05 percent level. The Propensity Score Matching using Nearest Neighbour and Kernel Matching Methods of the outcome variables, total farm income and food consumption patterns, shows a positive and statistically significant result at p < 0.05 percent level. The nearest neighbour matching method shows that irrigators received higher farm income R2044.01 than non-irrigating farmers R622.12. The Average Treatment Effect on total food expenditure was negative both in the case of NNM and KM algorithms, indicating that participation in irrigation can decrease the expenditure levels on food from R933.30 to R926.70. This could be due to the fact that irrigating farmers produced enough for home consumption than non-irrigators. The multinomial regression model shows that irrigation participation influences smallholder farmers choice of livelihood strategy and these variables were statistically significant at p < 0.05 percent level. These results provide insights to address the question as to the appropriate development path for transition from homestead to irrigation. Continued support to smallholder farmers in the forms of funding, extension services and improved technologies is certainly needed to enhance food security.
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Date Issued: 2017

Antidiabetic activity and mechanism of action of extracts of Brachylaena elliptica (Thurb.) DC. and Brachylaena ilicifolia (Lam) Phill & Schweick

Authors: Sagbo, Idowu Jonas
Date: 2017
Subjects: Herbs -- Therapeutic use Pharmacognosy Diabetes
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10353/8154 , vital:31624
Description: International Diabetes Federation (IDF) estimated that there are 415 million people globally that are suffering from diabetes and this figure is likely to double by 2040. In South Africa, the number of people suffering from diabetes is believed to be rising steadily and the current antidiabetic therapies include the use of expensive pharmaceutical drugs which after display numerous adverse side effects. Herbal medicine is an alternative treatment strategy used by many rural populations for the management of diabetes, which is cost-effective and with minimal reported side effects. The aim of this study was to validate the antidiabetic activity and to elucidate the possible mechanisms of action of the aqueous leaf extracts prepared from two plants, Brachylaena elliptica and Brachylaena ilicifolia, used by traditional healers in the Eastern Cape, South Africa for the treatment of diabetes. The current pharmaceutical drugs target site, including carbohydrate digestion, regulation of blood glucose levels through insulin levels or activating glucose uptake in liver and muscle. The plants extracts were therefore evaluated for their potential to mimic or replace these drugs. The inhibibitory effects on alpha amylase, alpha glucosidase, DPP-IV activity and pancreatic lipase were evaluated at various concentrations of the plant extracts. To evaluate the suitability of these extracts for cell based in vitro assay as well as to determine the safety of the plant extracts for human consumption, cytotoxicity towards HepG2 cells was assessed using the MTT assay. The effect of both plant extracts on glucose uptake in HepG2 and L6 cells, lipid accumulation in 3T3-L1 preadipocytes and NO production in RAW macrophages were investigated. Both plant extracts were also tested for INS-1 proliferation using the imageXpress®Micro XLS analysis. The MTT reduction assay was also used to investigate the effect of extracts on INS-1 glucose metabolism and as a reflection of insulin secretion. The inhibitory activity of the crude extracts of both plants on protein glycation, collagenase activity and CYP3A4 interaction were also evaluated The crude extracts of both plants displayed no significant inhibition on alpha amylase, alpha glucosidase, dipeptidyl peptidase-IV, lipase, protein glycation and collagenase compared to relevant standard inhibitors, acarbose, EGCG, Diprotin A, Orlistart and aminoguanidine. The mild inhibition of B. elliptica on alpha glucosidase activity at the highest concentration of the extract tested, was considered as not physiologically relevant. The aqueous extracts of bothplants showed < 40 percent cell death in HepG2 cells even at high concentration and hence support the use of the plants by traditional healers. The extracts of B. ellipticaat 25 µg/ml, displayed a proliferative effect on INS-1 cells when compared to the negative control and B. ilicifolia at 25 μg/ml. The treatment of HepG2 cells with 100 µg/mlB. elliptica and B. ilicifolia extracts revealed a higher glucose uptake of 121 percent and 123 percent respectively when compared to the pharmaceutical drug berberine. However, both plants extracts displayed weak significant glucose uptake in L6 muscle cell line at all the tested concentrations when compared to insulin at 6 μg/ml. The crude extracts of both plants demonstrated no significant effect on 3T3-L1 lipid accumulation and INS-1 glucose metabolism. The extracts of both plants strongly reduced NO production in RAW macrophages at the highest concentration (100 μg/ml) tested in this study, which at least in part, may be explained by the flavanoids and phenols content of these plants. In addition, the crude extracts of both plants displayed weak significant inhibition on the CYP3A4 activity indicating that both plant extracts do not interfere with the cytochrome P450 activation or metabolism of anti-diabetic drugs, that may be taken together with the plant extracts. In conclusion, the results obtained from this study revealed that both plants could possibly exert their hypoglycemic effect via interactions with insulin receptor, thereby enhancing glucose metabolism as well as maintaining and repairing the health state and function of the pancreatic beta cells. The findings in this study, therefore provide evidence that B. elliptica and B. ilicifolia possess antidiabetic properties, and support their folkloric use for the management of diabetes. However, due to the potential toxicity of both plant extracts, they must be prescribed with caution.
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Date Issued: 2017

Apparent digestibility coefficients of feed ingredients and essential amino acid requirements of dusky kob (Argyrosomus japonicus)

Authors: Adesola, Abidemi Adejoke
Date: 2017
Subjects: Amino acids in animal nutrition , Fishes -- Feeding and feeds , Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Nutrition , Argyrosomus -- Nutrition , Argyrosomus japonicus -- Feeding and feeds , Argyrosomus -- Feeding and feeds
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/32140 , vital:24014
Description: Important to the evaluation of potential feed ingredients for inclusion in fish diets should be their digestibility and amino acid requirement so that feeds can be formulated on a digestible basis rather than a gross nutrient basis. This thesis established techniques for faecal collection, the validity of digestibility markers, it determined apparent digestibility coefficients for various novel feed ingredients, and it established the optimal lysine requirement for Argyrosomus japonicus, which was used to estimate each of the essential amino acid requirements by using the ideal protein concept. There were no significant differences in dry matter apparent digestibility coefficients when faeces were collected by stripping (77.0 %), dissection (80.1 %) or settlement (83.5 %). Faecal collection by the settlement method produced the most reliable digestibility data. Apparent digestibility coefficients for dry matter, crude protein and energy calculated using acid-insoluble ash were higher (84.0 %, 93.2 % and 93.0 %, respectively) than those using chromic oxide (55.7 %, 79.1 % and 78.2 %) and titanium dioxide (58.6 %, 79.7 % and 80.5 %). The magnitude of variation in digestibility coefficients obtained using acid-insoluble ash was always lower than that obtained with the other markers. Therefore, acid-insoluble ash was preferred as a dietary marker. Using the above protocol, protein and amino acid digestibility of some animal and plant protein ingredients were evaluated in a series of experiments. The first trial compared the apparent digestibility coefficients of some animal products included as single protein source in the test diets. Apparent protein digestibility values were 84.5 %, 83.8 %, 85.8 % and 83.1 % for fishmeal-prime, fishmeal-standard, poultry meal and pork meal, respectively. Apparent digestibility coefficients for poultry meal were comparable to those of fishmeal, which indicate its potential as a substitute for fishmeal in the diets of A. japonicus. The second trial determined the apparent coefficients of plant and animal protein sources included at 30 % into a practical reference diet (70 %). Apparent protein digestibility ranged from 92.4 % in sunflower meal to 85.5 % in corn gluten meal. Soybean meal is a promising feed ingredient in A. japonicus due to the high apparent digestibility of its protein (92.0 %) and essential amino acid digestibility (mean average 91.4 %). A fundamental assumption in fish feed formulation is that the digestibility of nutrients is additive, i.e., digestibility of a nutrient in one ingredient does not interact with the digestibility of the same nutrient in another ingredient. In the third trial, additivity of feed ingredients was tested using pork meal and poultry meal. The results indicate that the apparent digestibility coefficient of animal protein ingredients could be calculated from compound diets to accurately determine protein and amino acid digestibility in A. japonicus, and possibly other carnivorous fish species. Dietary essential amino acid requirements were determined for juvenile A. japonicus in two trials. A dose-response study was conducted using crystalline lysine to determine the optimal requirement of dietary lysine for A. japonicus. Optimal dietary lysine was estimated at 31.7 g kg-¹ dry diet, corresponding to 73.5 g kg-¹ of dietary protein, based on specific growth rate and broken-line segmented regression analyses. Dietary requirements for other essential amino acids ranged from 22 g kg-¹ (histidine) to 71 g kg-¹ (leucine) crude protein. The results of the present study provided a research tool that could be used to assess and verify the conclusions of earlier dietary work on A. japonicus and in further studies to develop least cost diet formulations for this species. The study also adds to the knowledge of the nutritional requirements of A. japonicus by providing information on the digestibility of plants and animal protein ingredients. It also contributes to future dietary research for this species because this study determines, for the first time, the most suitable methods for investigating the digestibility of raw materials for A. japonicus.
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Date Issued: 2017

Application of the theory of critical distance technique to predict fracture toughness in friction stir welded Ti-6Al-4V sheet

Authors: Rall, William Henry
Date: 2017
Subjects: Friction stir welding Fracture mechanics
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10948/20351 , vital:29266
Description: With modern day socioeconomic pressures to deliver more cost effective, higher performance and energy efficient mechanisms and structures, light weight design is coming more to the forefront of design methodologies. These methodologies need to apply lightweight materials in unison with a defect tolerant design strategy. Titanium is certainly not a new material and was used in large quantities in the 1960’s and ‘70s, but mostly in military applications. The main drawback of this material was cost, however due to current design needs as mentioned the consumption of the material is rising rapidly. Friction stir welding is by no means a new technique anymore, however, relatively speaking it is still in its infancy when compared to other traditional welding techniques. It has been applied mostly to low melting temperature metals, more specifically aluminium; however, its application to higher melting temperatures has started to enjoy more attention over the last few years. The lower temperatures at which the weld occurs, when compared to conventional processes, is the main reason for applying this technique to materials melting at a higher temperature such as titanium. Fracture mechanics allows modern-day designers and maintenance engineers to operate structures with an inherent flaw. These flaws may be due to geometric features of the design; fabrication defects or defects such as cracks that have developed over time within an operational structure. Fracture mechanics has evolved significantly since Griffith first proposed it in the early 20th century. The application of the method is often complex and determining the material properties for fracture resistance can be problematic and costly. Many techniques have been proposed over time to simplify the application of this method and one of these techniques would be the theory of critical distance. Since the technique is relatively new and has mostly been applied to more brittle materials, this study aimed not only to apply this technique to a more ductile material but additionally to one that is classified as a sheet material. The initial tests of this study investigated if a common convergent point could be determined by using three notches varying in size. The technique does not have a standard that governs its application. The initial tests did not yield a common intersecting point thus a second study was applied to see if sample width would influence the results. The results from the study indicated that wider samples seemed to yield similar apparent fracture toughness results, however a common convergence point could still not be established. This prompted a more in-depth study which involved various sample widths coupled with varying notch depths. Sharper notches were also applied and samples with controlled cracks were also tested. The results clearly showed that as the plastic zone size increases in relation to the ligament length of the sample, the critical distance becomes larger. The results also suggested that it would perhaps be best to use sample sizes with notches which allow fracture of the sample before the nett section stress reaches the material’s yield strength. The final tests involved testing the friction stir welded material. Various other studies were also done to corroborate the fracture toughness results. The stress relieved samples showed a reduction in the fracture toughness due to possible precipitation hardening during the stress relieving heat treatment process. The welded material showed an increase in the apparent fracture toughness when compared to the parent plate. The results indicate that residual stresses have an influence on the fracture toughness. In terms of the critical distance, it would appear that the value stays unchanged from the parent plate to the welded material; however, what is significant was that the value seemed to stay more or less constant as long as the nett section stress of the notched samples stayed below the yield stress of the material.
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Date Issued: 2017

Assessment of anti-urease and consequential inhibitory potential of South African honey extracts on the multiplication of drug-resistant, vacA and cagA positive helicobacter pylori strains under acidic conditions

Authors: Dube, Callote
Date: 2017
Subjects: Helicobacter pylori Drug resistance in microorganisms Honey -- Therapeutic use
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10353/7787 , vital:30764
Description: Helicobacter pylori, a neutralophile chronically infects the gastric stomach of more than half of the world’s population. Infection with the organism is associated with acute or chronic duodenal/gastric ulcer disease, gastritis, gastric adenocarcinoma, mucosa-associated tissue lymphoma (MALT) and primary B-cell gastric lymphoma and has been grouped as a class one carcinogen by the World Health Organisation (WHO). Prevalence of this organism is very high in developing countries especially in Africa, including South Africa. H. pylori treatment using the common first and second line regimens, triple therapy with two antibiotics and a proton pump inhibitor (PPI) is showing inefficiency due to increasing drug resistance. However, newly developed treatment regimens seem to be more expensive and are accompanied by more side effects. Honey contains phytochemicals which are a wealthy source of biologically active compounds some of which have been put into good use in the pharmaceutical industry. Pathogenesis of H. pylori infection in the human stomach relies on several virulence factors which include the urease enzyme, cagA and vacA. The urease enzyme actively hydrolyses urea to produce ammonia an important by-product involved in pH regulation favouring the survival of the organism in the acidic human stomach. This study therefore focuses on screening for anti-urease solvent extracts of South African honey, and evaluate whether inhibition of urease offsets the growth of H. pylori under acidic conditions. Locally produced natural honeys; Bush honey, Raw honey, Gold Crest honey, Q Bee honey, Little Bee honey, Fleures honey-radurised, Siyakholwa pure honey and Manuka honey; an import from New Zealand were purchased and the method by Syazana et al. (2010) was used for the extraction of compounds in honey. A standard strain ATCC 43526 (American Type Culture Collection, Manassas, VA, USA) and 48 pure cultures obtained from clinical isolates cultured from gastric corpus biopsy specimen of patients with gastric morbidities who were ix visiting the endoscopy unit in Livingstone Hospital, Port Elizabeth between June 2008 to December 2008 were initially used as source of urease enzyme as per extraction method done by Amin et al. (2013), but with modifications. Prior to urease extraction, H. pylori strains were identified by biochemical tests (urease, catalase, oxidase, Gram stain), confirmed by PCR targeting the glmM gene (140 bp) and drug resistance profiling was done on all the 48 strains according to Seanego et al. (2012). The screening for anti-urease active compounds was done according to Kaltwasser et al. (1966), a method relying on the reduction of NADH in a coupled urease dehydrogenase (GDH) system. Acetohydroxamic acid was used as a standard inhibitor. Prevalence of cytotoxin-associated gene A (cagA) gene and vacuolating cytotoxin gene A (vacA) gene was determined among all 48 clinical samples. The standard strains of H. pylori, X47 (cagA positive), J99 (vacA s1m1) and Tx30a (s2m2) were used as positive controls. H. pylori’s growth was then monitored under acidic pH in a cocktail spiked with anti-urease compounds (test samples) and in a cocktail without anti-urease compounds (negative control). Acetohydroxamic acid was used as a standard urease inhibitor. H. pylori multiplication was monitored in Brain Heart Infusion Broth (BHIB) adjusted to pH of 2, 3, 4, 5, 6 and 7. The strain MP01 was used as a standard urease negative strain while X47 and J99 were used as positive standards for cagA and vacA s1m1 respectively. The compounds that had anti-urease activity and were successful towards suppressing the multiplication of H. pylori under acidic environment, all other factors optimised, were subjected to gas chromatograph mass spectrometry (GC-MS) and liquid chromatograph spectrometry (LCMS) to determine volatile compounds and drugs in honey extracts respectively. The findings of this study revealed that at a concentration of 50 mg/mL, urease inhibition by petroleum ether extracts of Gold Crest and Fleures honey, hexane extracts of Little Bee and Manuka honey, and chloroform extracts of Bush honey and Q Bee honey had a range above or equal to 50 percent and there was no significance difference in urease inhibition percentage (I percent) of urease from different sources including that extracted from drug resistant H. pylori (p >0.05). Virulence factors are important for the pathogenesis of H. pylori. All the 48 clinical isolates were glmM (140 bp) positive and cagA was detected in 97.9 percent of the test isolates. The vacA gene was detected in all isolates but with different subtypes. The vacA allelic combination s1m1 was detected in 75 percent of the test isolates and s1m2 allelic combination was detected in 16.7 percent of the test isolates while the combination s2m2 was detected in 8.3 percent of the test isolates. None of the test isolates possessed the allelic combination s2m1. When H. pylori multiplication was monitored under acidic conditions in the presence of anti-urease active compounds, it was revealed that anti-urease active compounds in honey are capable of inhibiting the normal multiplication of H. pylori strains that are cagA positive, vacA positive and drug resistant. The GC-MS analysis showed that Fleures honey (urease I percent = 67.8 – 68.5 percent) and Gold Crest honey (urease I percent = 50.9 percent – 53.3 percent), all petroleum ether extracts had 27 and 26 volatile compounds. The hexane extract of Manuka honey (urease I percent = 50.0 – 53.2) had 43 compounds detected. The chloroform extract of Q Bee (urease I percent = 64.2 – 66.2 percent) had 13 volatile compounds detected. All the volatile compounds considered as representative samples of GC-MS analysis had a spectral matching ≥ 90 percent with the NIST11 library. However, the majority of compounds that were detected by LC-MS in representative honey extracts include vardenafil, urapidil, hydrocortisone, e.t.c which are drugs commonly used in the treatment of different ailments or infections that affect human beings. In addition, two xi drugs, sulfaquinoxaline and hydroxyquinoline which are used in veterinary medicine and antiseptic, disinfectant and pesticide applications in agricultural activities were detected in Little Bee honey. We therefore conclude that inhibition of urease has a bactericidal effect on drug resistant, cagA positive and vacA positive H. pylori strains growing under acidic environment.
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Date Issued: 2017

Assessment of student satisfaction on institutional factors influencing student retention in one comprehensive university in the Eastern Cape Province of South Africa

Authors: Stofile, Regina N
Date: 2017
Subjects: Education, Higher -- South Africa College dropouts Dropouts -- South Africa -- Eastern Cape
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10353/9450 , vital:34353
Description: In all higher education institutions across the world, the student retention and success is an issue of concern and a pressing one. Students invest heavily in their higher education, while institutions in turn, lose a considerable sum of money for each student that drops out due to dissatisfaction with institutional services. The purpose of this quantitative methods research study, employing a survey design, was to assess student satisfaction with institutional factors that influence student satisfaction in higher education. The research questions focused on student satisfaction factors namely; academic advising, academic support, teaching approaches, assessment techniques, learning facilities, student funding services, student accommodation and administrative services. The study used structured questionnaire, with Likert scale type of question items, to collect data from the respondents These were hand delivered to 650 students in four campuses of the selected university. SPSS was used for data analysis. Major findings revealed that the selected institutional factors significantly impacted on student satisfaction, and their decisions to stay within the institution. Based on the results of the study, a framework to assist the institution ensure that student are receiving the services that they need from the institution as early as possible, was proposed. The study provided therefore the useful data for institutions to use in their quality enhancement activities. The result of the study can be incorporated into enrolment management planning and the intervention strategies, to improve the success of students at the selected institution in Eastern Cape.
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Date Issued: 2017

Av evaluation of the contribution of shelters in offering psychological empowerment to survivors of abuse : a study of selected shelters in Pretoria

Authors: Nyamutinga, Dudzai
Date: 2017
Subjects: Women's shelters -- South Africa Abused women -- Services for -- South Africa Victims of family violence
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10353/9209 , vital:34305
Description: This research explored the contribution made by shelters in the psychosocial empowerment of survivors of abuse in the contemporary South Africa. Abuse of women is increasing at an alarming rate and government is not able to handle the task single-handedly. The study utilized convergent mixed methods approach (Creswell, 2014) with qualitative and quantitative approaches used in tandem; but with the qualitative approach being more dominant, while quantitative approach was less dominant. For research designs, the qualitative approach used a case study design; while the quantitative method utilized a mini survey design. On the unit of analysis, 52 participants participated in the qualitative sample, with the following sample distribution: 30 participants (15 from each shelter) participated using in-depth interviews, 10 participants (5 from each shelter) constituted a focus group discussion with 12 participants (6 from each shelter) interviewed as key informants. The quantitative approach had a sample of 100 samples women who were victims of abuse complete a mini survey based on questionnaire interviews. The study identified many factors that prompted women to go and reside in shelters from physical abuse and sexual abuse usually perpetrated by women’s spouses taking the larger share. Other important drivers included economic and emotional abuse. This resonates with some of the tenets of the critical feminist theory that an offender’s victimization of another person is an expression of domination and control (Brownmiller and Russell, 1975 in Wilcox 2010). Furthermore, the United Nations recognizes that violence against women is a manifestation of historically unequal power relations between men and women, contributing from male domination and discrimination over women. The study also established various psychosocial services provided to survivors of abuse. Such services were important in order to strengthen survivors’ coping capacities, raise their confidence and reinforce their decision-making processes pertaining to their lives. Some of these psychosocial services provided include provision of accommodation, nutritional meals, therapeutic counselling, basic counselling sessions, group work sessions, access to skills development programmes, assistance in maneuvering the judicial system, job placements, parenting skills, access to education and provision of preschool for their children and information and referrals. This study also managed to unearth and identify the various institutional and operational challenges that beset the running of the two selected shelters in Pretoria. Acutely, shelters suffer funding challenges, with funding either being inadequate or having to take so long before it is availed and, therefore, almost affecting the day to day operations of the shelters. These shelters were also challenged by donor regulations, inadequate infrastructure and a continuous increase of survivors and children in their care. Furthermore, the study identified the shelters’ effectiveness to raise survivors’ hope for the future; boost their confidence; improve their social functioning; provide emotional and practical support; offer them the requisite accommodation and meals; and also provided them with different kinds of skills that made them financially independent. The research recommended that a decentralization of shelters to rural areas across all provinces and the nation at large would go a long way in ensuring that all survivors will get the assistance they need. As the rural-urban migration takes its toll, the abuse of women also continues to increase. Funding is the key to the success of every project, and, therefore, the provision of enough and consistent funding and a sustainable plan to the shelters will ensure the smoothness of the provision of services and reduce staff burnout, reduce high staff turnover, and increase the stability of trained personnel. The study also recommends the government to consider subsidizing the salaries for the staff working in shelters so that their salaries would be on par with their colleagues in other organizations. Government should also facilitate the institution of shelters for survivors of abuse as some men feel that the issue of abuse focuses on females and therefore men shy away from accessing the services of the shelters.
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Date Issued: 2017

Best practice guideline for the nursing management of women with gestational diabetes mellitus in military health institutions in Ghana

Authors: Mensah, Gwendolyn Patience
Date: 2017
Subjects: Diabetes in pregnancy -- Ghana , Diabetics -- Treatment -- Ghana Nursing services -- Ghana -- Administration Public health -- Ghana
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10948/14036 , vital:27409
Description: Pregnancy is a normal physiological process for the majority of women. These women, their families and significant others normally expect a successful period of pregnancy, labour, delivery and arrival of a normal and healthy baby. However, some of these pregnant women may develop Gestational Diabetes Mellitus (GDM) during this period and if not managed properly, the mother and the foetus in utero are affected in a negative way: there is a likelihood of the mother and baby developing Type 2 Diabetes in the future and also, other risks such as preterm labour, and foetal macrosomia. In order to prevent such occurrences, I set out to develop a best practice guideline for the nursing management of GDM in military health institutions in Ghana in order to help enhance nursing care. The design for this research was qualitative, explorative, descriptive and contextual in nature. The research is organised in three phases: Phase one deals with the data analysis and discussion of the interviews with professional nurses and midwives and women with a history of GDM. The data collected from the interviews were transcribed, analysed and extracted with Tesch’s eight steps of coding used for the coding. The services of an independent coder were employed to assist with the coding process which led to the formulation of key themes. Semi-structured individual interviews provided a means of exploring the perceptions of professional nurses and midwives on the nursing management of GDM: in addition, women with a history of GDM were interviewed so as to elicit their views on the management they had experienced from professional nurses and midwives before and after being diagnosed with GDM. The trustworthiness of the study was ensured by conforming to Lincoln and Guba’s framework of credibility, transferability, dependability, confirmability and authenticity. An independent coder assisted with the coding process. Phase two deals with the Integrative literature review of available evidence-based clinical practice guidelines for the nursing management of GDM. Evidence-based clinical practice guidelines were searched and appraised with assistance from an independent appraiser and themes were then formulated. In Phase three, the themes from Phase one and Phase two were integrated for the development of a draft best practice guideline for the nursing management of GDM in military health institutions in Ghana. The draft guideline was given to an expert panel of reviewers for their comments and recommendations. These were considered in the development of the final best practice guideline for the nursing management of GDM.
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Date Issued: 2017

Biotic and abiotic factors promoting the development and proliferation of water hyacinth (eichhornia crassipes (Mart.) Solms-Laub.) in the Wouri Basin (Douala-Cameroon) and environs, with implications for its control

Authors: Voukeng, Sonia Nadege Kenfack
Date: 2017
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/7644 , vital:21281
Description: The Wouri River, situated in the Wouri Basin, is one of the main rivers of the Littoral Region in the city of Douala in Cameroon. It is a source of income and food for the population living around these areas. Since the 1990s, the fishing, transportation, irrigation and sand extraction activities have been impeded by the invasion of aquatic plants, specifically water hyacinth (Eichhornia crassipes [Mart.] Solms-Laubach: Pontederiaceae). Introduced in 1997 to the shore of Lake Chad, water hyacinth has invaded almost 114 ha of the Wouri Basin. Furthermore, Douala, the economic capital of the Cameroon and location for more than 70% of the country’s industries, uses the Wouri River and its tributaries to deposit its effluent and waste, which has worsened the problem of water hyacinth. This thesis examined the ecological and socio-economic impacts of water hyacinth in the Wouri Basin and its possible control. An increase in the nutrients in the water has provided water hyacinth with appropriate conditions for its fast growth during both the rainy and dry seasons. The availability of nutrients in these areas is enhanced by the constant, daily tidal fluctuation of water, providing enough water to the plant for easy nutrient uptake. A survey of the impacts of water hyacinth on aquatic plant communities in the Wouri Basin showed that this plant is able to out-compete native species. Assessment of the impact of water hyacinth on the abundance and diversity of plant communities indicated that at some invaded sites, 65% of the vegetation consisted of water hyacinth. Species found in association with water hyacinth with a high level of abundance-dominance were Pistia stratiotes L. (Araceae) (another invader), Commelina benghalensis L. (Commelinaceae) and Echinochloa pyramidalis (Lam.) Hitchc. & Chase (Poaceae). This component of the study also showed that habitats rich in water hyacinth were poor in diversity, while habitats without water hyacinth were rich in diversity, thus raising awareness of the importance of monitoring invasive aquatic weeds along the Wouri Basin, and of implementing correct control management of all invasive aquatic weeds. Communities living along the invaded rivers are well aware of the range of problems caused by the weed; because as the rivers and water bodies used for fishing, transportation, and sand extraction are progressively invaded by the weed, the riparian population is the first to feel the impact. The impact on people has been noticeable, with an increase in diseases, such as malaria, cholera, diarrhoea, typhoid, filariasis, schistosomiasis, scabies and yellow fever increasing the need for a medicine and hospitalization. Economic losses due to the management of invasive aquatic weeds were recorded, and the Ministry of Environment spent an estimated US$1 200 000 between 2010 and 2015 to manage this scourge. In 2016, an amount of US$160 000 was transferred to these regions to manage invasive aquatic weeds, especially water hyacinth, although manual clearing is still the only method used to control this weed. Isolation of fungi from diseased water hyacinth plants in the Wouri Basin revealed several fungal species, most of which have been isolated from water hyacinth species in water bodies elsewhere, which showed a higher diversity during the dry season than during the rainy season. These fungi included Acremonium zonatum (Sawada). W. Gams (Hypocreaceae), Alternaria eichhorniae Nag Raj & Ponnappa (Pleosporaceae), Chaetomium sp., Colletotrichum sp., Curvularia pallescens Boedjin (Pleosporaceae), Curvalaria sp., Epicoccum nigrum Link (Pleosporaceae), Fusarium sp., Pithomyces chartarum fBerk. & M. A. Curtis) M. B. Ellis (Montagnulaceae), to a lesser extent Myrothecium roridum Tode ex Fr. (Incertae sedis) and Nigrospora sp. Although never released in Cameroon, arthropod biological control agents (Neochetina eichhorniae Warner (Coleoptera, Curculionidae) and N. bruchi Hustache (Coleoptera, Curculionidae)) were present, but their populations were relatively low. The slow spread of the insect population was explained by several factors, among them the tidal fluctuation of water, which has an impact on the population growth of the weevils. Whilst adults may be able to survive tidal fluctuations, larvae are severely impacted by them, contributing to the slow success of biological control. In this study, a significant increase in pathogen-induced disease severity and incidence was noted when Neochetina eichhorniae weevils were present, possibly because larvae tunnelling on the petiole created openings for the penetration of fungal spores. This study highlights the negative impacts of water hyacinth, on the environment, people, and thus economy of Cameroon. The presence of biological control agents and pathogens offers Cameroon the possibility of initiating and properly implementing the biological control option, or an integrated management solution, to manage water hyacinth in the Wouri Basin, and in the rest of Cameroon.
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Date Issued: 2017

Bush clumps as indicators of thresholds of change in Arid Thicket mosaic piospheres

Authors: Schmidt, Anton George
Date: 2017
Subjects: Biodiversity conservation Ecological processes
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10948/20811 , vital:29403
Description: In the literature, Arid Thicket transformation by domestic meso-herbivores is purported to follow a state-and-transition model, whereby the ecosystem is initially resilient to herbivory until some threshold is crossed, where after there is a rapid shift to a new alternative stable state. My study represents a first attempt to verify this hypothesis by searching for evidence of stable ecosystem states separated by structural, functional and degradation thresholds in Pruim-Spekboomveld, a variation of Arid Thicket found in the southern Cape of South Africa. In this variation, thicket bush clumps ranging in size from approximately 1 m2 to 100 m2 are interspersed in a matrix of Succulent Karoo vegetation. I correlate structural and functional attributes of the thicket bush clumps and the soil environment beneath them (indicators of ecosystem function) to distance from artificial watering points in four piosphere treatments that have had a different rangeland management history. I mostly fit linear, exponential and sigmoid regression models to my data and use Akaike’s Information Criterion to select the best fitting model. When analysing data on changes in the variation of vegetation production with distance from water using the Normalized Difference Vegetation Index, I additionally fit Generalized Additive Models to the data to take into account more complex predicted patterns of change. Furthermore, I compare the end regions of my data in the piosphere treatments to each other and to similar data collected in a transformed and untransformed reference site. I use both the pattern and extent of transformation within and between the treatments and the reference sites, to verify the existence of stable states and structural, functional and degradation thresholds. I also subject my entire dataset to multivariate analysis using ordination and permutation procedures, in an attempt to corroborate my results from the univariate analysis and to assess the response of bush clump community composition to herbivory. My results indicate that at the scale of a bush clump, a threshold reduction in species richness, functional type diversity, succulent shrub redundancy and cover, palatable shrub cover and bush clump leaf mass below 1.5 m occurs in regions intensively used by domestic meso-herbivores. Furthermore, at the landscape scale there is a threshold reduction in canopy tree cover and bush clump density. In addition to these structural threshold changes, results from a Landscape Function Analysis indicate that soil nutrient cycling, soil water infiltration and soil stability thresholds are crossed at the landscape scale. The soil nutrient cycling threshold is affirmed by soil chemical analyses which indicate that the most rested treatment in the study area has low carbon and nitrogen levels. Furthermore, the keystone species, Portulacaria afra, is unable to re-establish itself in any of the treatments. High pH and potassium levels in all the treatments, relative to the untransformed reference site, indicate that Portulacaria afra (which prefers moderate soil conditions) is unlikely to re-establish in the study area. This finding suggests that all my treatments have crossed a degradation threshold and therefore represent an alternative stable state to the untransformed reference site. My multivariate analysis supports this finding and further indicates that the sampling zones within 25 m of the watering points in the most utilized treatments have crossed a second degradation threshold. This finding is supported by my results that indicate that structural and function thresholds (related to the size, density and ability of bush clumps to capture and retain soil resources) have been crossed. Furthermore, excessively high concentrations of base cations in these sampling zones, relative to the untransformed reference site, affirm the crossing of a degradation threshold. My results on the changes in the variation of vegetation production with distance from water using the Normalized Difference Vegetation Index, support the growing body of evidence in the literature that suggests that increases in the variance of ecosystem processes and services are important indicators of impending ecological thresholds. In general, my findings support the prediction in the literature that domestic meso-herbivore induced transformation of Arid Mosaic Thicket will follow a state-andtransition model.
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Date Issued: 2017

Cape gannets in contrasting environments: ehaviour, demographics and indicators of environmental change

Authors: Ryklief, Rabiah
Date: 2017
Subjects: Endemic birds -- South Africa Marine pollution -- South Africa
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10948/21167 , vital:29452
Description: Marine communities represent biological networks, where physical and chemical changes in the marine environment can influence the physiology and behaviour of marine organisms. Stochastic marine conditions can alter key biological interactions and thus, influence the mechanisms that underpin population demography and phenotypic plasticity. Marine top predators, such as seabirds, are often controlled by bottom-up processes and their ability to cope with variable ocean conditions lies in their physiological and behavioural response to such perturbations. Seabirds are central-place foragers during the breeding season making them particularly vulnerable to environmental fluctuations as they face constrains associated with reproductive effort in addition to self-maintenance. The Cape gannet Morus capensis is a medium-sized pelagic seabird that is endemic to southern Africa. The Cape gannet has experienced considerable change in population distribution and abundance over the past 50 years. These changes have been linked to a combination of fishing pressure and climate-mediated regime shifts of their preferred prey, i.e. sardine Sardinops sagax and anchovy ngraulis encrasicolus. Historically, Malgas Island was the largest Cape gannet colony in South Africa. However, it is now in a state of population decline, despite its occurrence within one of the most productive upwelling systems in the world, the Benguela Current. At present, Bird Island is the largest Cape gannet colony and has recently stabilised, despite regular immigration of gannets from the west coast. Furthermore, Bird Island lies within the Agulhas bioregion and is subject to low levels of productivity from the nutrient-poor Agulhas current. Malgas and Bird islands are the two most populous of the six extant Cape gannet colonies. Birds at these colonies provided a natural experiment due to the contrasting population trajectories and environmental conditions at their colonies. The foraging ecology and behaviour of Cape gannets were studied during the breeding season to assess the mechanistic links connecting climate and fisheries to population demography. Cape gannets displayed considerable inter-annual variation in foraging effort and distribution across a five-year period. This highlights the importance of long-term datasets to contextualise the degree of natural variation within a species, as well as considerations for conservation management. For the first time, oceanographic variables such as sea surface temperature and chlorophyll-a, indices that reflect marine productivity, were used to predict Cape gannet foraging distribution. Furthermore, Cape gannets at Bird Island had an energy budget deficit in a year when foraging effort was much higher in comparison to what was observed at Malgas Island. This in turn was linked to the first identification of nutritional stress in a Sulid species. Reasons for this include a combination of higher intra-specific competition in conjunction with a lower energetic content of referential prey species at Bird Island. Foraging effort showed more variability at Malgas Island in comparison to Bird Island, likely due to Malgas Island gannets often taking two short foraging trips a day, whereas Bird Island gannets often spent the night at sea. Some degree of phenotypic plasticity was evidenced by substantial variations across breeding seasons and ocean basins in foraging effort and behaviour.
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Date Issued: 2017

Changes in household food security, nutrition and food waste along an agro-ecological gradient and the rural-urban continuum in mid-sized South African towns

Authors: Chakona, Gamuchirai
Date: 2017
Subjects: Food security -- South Africa , Women -- South Africa -- Nutritiona , Urban women -- South Africa -- Nutrition , Rural women -- South Africa -- Nutrition , Wild foods -- South Africa , Food supply -- South Africa , Malnutrition in children -- South Africa , Grants-in-aid -- South Africa , Household ecology -- South Africa
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/6484 , vital:21127
Description: The lack of dietary diversity is a severe problem experienced by most poor households globally. Most poor communities are at high risk of inadequate intake of micronutrients resulting from diets dominated by starchy staples. The present study considered the diets, dietary diversities and food security of women of reproductive age between 15-49 years, households and communities along the rural-urban continuum in three mid-sized towns situated along an agro-ecological gradient in South Africa. A 48-hour dietary recall was performed across two seasons (twice in summer and once in winter) and focus group discussions were held to gather all information including food abundance, seasons of food scarcity as well as coping strategies which households employ during periods of food shocks. Households were further asked to quantify any type of food waste that they could have generated in the previous 48 hours. Nutritional status of children under the age of five in all three towns was also measured using height-for-age (HAZ) and mid-upper arm circumference (MUAC) as indicators of stunting and wasting respectively. The household surveys were conducted with 554 women randomly selected in rural, peri-urban and urban locations of Richards Bay, Dundee and Harrismith. For nutritional status, the sample consisted of 216 children who were randomly selected from the sampled households in rural, peri-urban and urban locations of the study sites. Household Dietary Diversity Scores (HDDS) and Women’s Dietary Diversity Scores (WDDS) were calculated from the food items consumed by each household and each woman over a two-day period, respectively. Household food access was also measured for each household using Household Food Insecurity Access Scale (HFIAS). The mean WDDS and HDDS for the wettest site of Richards Bay (3.8±0.29 and 8.44±1.72, respectively) was significantly higher than at Dundee (3.4±0.30 and 7.76±1.63, respectively) and Harrismith (3.5±0.27 and 7.83±1.59, respectively) which were not different from one another. The mean HFIAS for Dundee (9.39±7.13) was significantly higher than that in Richards Bay (5.57±6.98) and Harrismith (6.43±6.59) which were not significantly different from one another. Dietary diversity scores were also significantly higher in urban locations than in peri-urban and rural ones whilst HFIAS was significantly lower in the urban locations than peri-urban and rural locations. There was lower dependence on food purchasing in Richards Bay compared to Dundee and Harrismith where the majority of the population was purchasing most of their food. The majority of Richards Bay households were involved in subsistence agriculture and also produced a surplus for sale, as well as collecting wild foods, which improved food security, unlike Dundee and Harrismith. Food insecurity was higher in rural and peri-urban areas compared to urban areas. In all towns, food was always available throughout the year but was beyond the reach of many households. In urban areas food was readily available and only limited by access, whereas rural populations have limited access to affordable food and face higher prices. The peri-urban populations were more food insecure because of high levels of poverty, unemployment and lack of access/entitlements to land. Periurban dwellers are therefore more sensitive to changes in incomes and food prices because they lack safety nets to absorb income or price shocks as they purchase more, rather than growing their own food. Household dietary diversity was significantly negatively correlated with household food access, that is households with low HDDS had higher HFIAS scores. Due to high levels of food insecurity, a greater percentage of children under the age of five years were stunted (35 %) and wasted (18 %). There were no significant differences in stunting along the agro-ecological gradient, along the rural-urban continuum and sex of child. However, significant differences were observed in child wasting along the agro-ecological gradient with Harrismith having more wasted children than the other two towns, which were not significantly different from each other. Significant differences were also observed between MUAC and sex of child where male children had higher MUAC than females. Wasting was significantly negatively associated with HDDS, with children from households with low HDDS tending to have large MUAC thus showing an inverse association among HDDS and obesity. However, further studies are needed to confirm this finding. In general food insecurity was closely associated with low wealth, food expenditure, large household size and limited access to land. The study did not find any significant role in the use of wild foods and social grants in improving food security for those households who were consuming wild foods and those receiving social grants. Although a greater percentage of households were food insecure, significant amounts of unprepared food (495±179 g per household) were wasted in Richards Bay alone in 48 hours mainly because the food had passed the best before date or had visibly gone bad. The amount of food waste was closely significantly negatively associated with household size. In general, the prevalence of food insecurity and wasting followed the agro-ecological gradient, with households in Richards Bay where the area.
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Date Issued: 2017

Characterisation of photovoltaic devices using large area light beam induced current measurements

Authors: Okullo, Michael , Van Dyk, Ernes , Okullo, W
Date: 2017
Subjects: Photovoltaic cells Photovoltaic power generation
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10948/20526 , vital:29314
Description: Photovoltaic (PV) modules are made by connecting PV cells in series in order to generate a reasonable voltage that can be used for any productive work. Inaccuracy in cell sorting during crystalline silicon module construction, or non-uniform deposition of PV material and laser scribing during thin _lm module construction, may introduce current mismatch in the module. Current mismatch is a consequence of connecting module cells which have non-identical electrical characteristics. When current mismatch occurs in a module, it is the cell generating the lowest current that determines the module output current and this leads to a decrease in the output power and lifespan of the module. Investigation of current uniformity and the different current reducing features in PV modules, which are potential sources of current mismatch, is therefore critical in optimising the performance of PV modules. In this study, a large area light beam induced current (LA-LBIC) measurement system was developed. This non-destructive technique was used to characterise crystalline silicon PV modules (mono-crystalline and multi-crystalline), thin _lm PV modules (amorphous silicon and copper indium diselenide) and a combined concentrator photovoltaic (CPV) module. A light source mounted onto a motorised x-y scanning stage was used to illuminate a PV module, or the Fresnel lens of a CPV module, point-by-point, while measuring the module output current. The measured current was mapped as a function of position and presented as an LBIC image. The point-illuminated circuit model of a PV module was designed and used to explain the variation in current between and within module cells in the LA-LBIC maps. Application of the model to crystalline silicon modules attributes the variation in photo-generated current between cells mainly to current mismatch between series connected cells. Current variation within cells is attributed to individual cell shunts. In the thin _lm modules, the model attributes the variation in photo-generated current mainly to differences in local cell shunts and series resistances originating from the scribing procedure during cell formation in the manufacturing process. In the PV modules studied, variation in photo-generated current was found to exist both between and within cells. The variation was more pronounced between cells than within cells. Module point I-V curves at different points of the module were measured in order to extract short circuit current, to quantify the variations between and within cells. A striation ring defect, causing a drop in short circuit current of 38%, was detected in the mono-crystalline module. Investigation of the striation ring defect indicated that the defect is active in the bulk (p-type) but inactive in the top (n-type) layer. Further characterisation of the defect revealed that a higher percentage loss in short circuit current occurs at lower light intensities. In the multi-crystalline silicon module, cracks were detected and found to electrically isolate the module cells into two parts, causing them to operate in parallel and consequently introducing current mismatch in the module. The I-V curve of the module at standard test condition (STC) revealed a step below the knee, which is a manifestation of current mismatch in the module. High currents, as a consequence of diffuse reflection, leading to multiple reflections by the top glass were also observed at localised points on the bus bar and cell separations. In the a-Si module, the variation in photo-current within some cells, was found to be substantial. In the copper indium diselenide (CIS) module, an electrical disconnection across the module cells was identified. A disconnection in the form of a triangular shape was also identified in this module, which completely disconnected the front contact of this area from the module. This unique disconnection feature caused current in the module to follow in a reverse direction when the light spot was incident within the boundary of the disconnection. Scans performed under different forward voltage biases were useful in identifying severely shunted module cells. A severely shunted cell was found to generate a higher photo-current than a good cell at the same forward bias voltage. This unique observation was explored further using point-illuminated module I-V measurements, and was found to be due to the crossing over of the I-V curves of the two cells. In order to explore the relationship between cell photo-current and cell shunt resistance, a method to determine the shunt resistances of the cells in an encapsulated module was devised. The method involves measuring the I-V curves of a fully illuminated module and a partially illuminated module when one of its cells is shaded and the I-V curves used to determine the short circuit current and the shunt resistance of the shaded cell. A strong correlation was found to exist between the short circuit current of the shaded cell and the cell shunt resistance, as well as between the short circuit current of the shaded cell and dark LBIC. The LA-LBIC technique was further applied to characterise a combine CPV module. Results showed that the Fresnel lens facets close to the centre generate a higher photo-current at the receiver than those towards the edges. The reduced photo-current towards the edges was attributed to losses due to di_raction, dielectric reflection and internal re_ection. About 65% of the area of the Fresnel lenses were found to be e_ective in light collection in terms of the photo-current generated at the receiver. Abrasions and scratches on the Fresnel lenses were identi_ed as some of the current limiting features in a CPV module. The LA-LBIC technique used in this study has demonstrated the potential to investigate current mismatch, current limiting and current enhancing features in PV modules. The capacity to further characterise current limiting features in order to investigate their effects on photo-current under different wavelengths and light intensities was also demonstrated. Extending the LA-LBIC technique to characterise a combined CPV module is a great achievement of this work.
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Date Issued: 2017

Chinese aid and African agency since 2000: examining the cases of Zimbabwe, Angola and Ghana

Authors: Chipaike, Ronald
Date: 2017
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/59151 , vital:27442
Description: Restricted access-thesis embargoed for 2 years
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Date Issued: 2017

Colonisation and succession of fishes in Lake Liambezi, a shallow ephemeral floodplain lake in Southern Africa

Authors: Peel, Richard Anthony
Date: 2017
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/65211 , vital:28707
Description: Expected release date-May 2019
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Date Issued: 2017

Combined in silico approaches towards the identification of novel malarial cysteine protease inhibitors

Authors: Musyoka, Thommas Mutemi
Date: 2017
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/4488 , vital:20679
Description: Malaria an infectious disease caused by a group of parasitic organisms of the Plasmodium genus remains a severe public health problem in Africa, South America and parts of Asia. The leading causes for the persistence of malaria are the emergence of drug resistance to common antimalarial drugs, lack of effective vaccines and the inadequate control of mosquito vectors. Worryingly, accumulating evidence shows that the parasite has developed resistant to the current first-line treatment based on artemisinin. Hence, the identification and characterization of novel drug targets and drugs with unique mode of action remains an urgent priority. The successful sequencing and assembly of genomes from several Plasmodium species has opened an opportune window for the identification of new drug targets. Cysteine proteases are one of the major drug targets to be identified so far. The use of cysteine protease inhibitors coupled with gene manipulation studies has defined specific and putative roles of cysteine proteases which include hemoglobin degradation, erythrocyte rupture, immune evasion and erythrocyte invasion, steps which are central for the completion of the Plasmodium parasite life cycle. In an aim to discover potential novel antimalarials, this thesis focussed on falcipains (FPs), a group of four papain-like cysteine proteases from Plasmodium falciparum. Two of these enzymes, FP-2 and FP-3 are the major hemoglobinases and have been validated as drug targets. For the successful elimination of malaria, drugs must be safe and target both human and wild Plasmodium infective forms. Thus, an incipient aim was to identify protein homologs of these two proteases from other Plasmodium species and the host (human). From BLASTP analysis, up to 16 FP-2 and FP-3 homologs were identified (13 plasmodial proteases and 3 human cathepsins). Using in silico characterization approaches, the intra and inter group sequence, structural, phylogenetic and physicochemical differences were determined. To extend previous work (MSc student) involving docking studies on the identified proteins using known FP-2 and FP-3 inhibitors, a South African natural compound and its ZINC analogs, molecular dynamics and binding free energy studies were performed to determine the stabilities and quantification of the strength of interactions between the different protein-ligand complexes. From the results, key structural elements that regulate the binding and selectivity of non-peptidic compounds onto the different proteins were deciphered. Interaction fingerprints and energy decomposition analysis identified key residues and energetic terms that are central for effective ligand binding. This research presents novel insight essential for the structure-based molecular drug design of more potent antimalarial drugs.
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Date Issued: 2017

Community structure and trophic relations in marine tufa stromatolite pools of the Eastern Cape

Authors: Rishworth, Gavin Midgley
Date: 2017
Subjects: Bioturbation -- South Africa -- Eastern Cape
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10948/7116 , vital:21236
Description: Microbialites were the dominant life-form of most shallow oceans during the Precambrian. These structures are formed by the deposition of calcium carbonate by cyanobacteria as well as the binding and trapping of sediment by these and other microalgae. In modern environments they are scarce due to several factors, including grazing pressures by metazoans, altered calcium carbonate saturation states of seawater and competition with macroalgae. The recent discovery of an extensive network of actively accreting layered microbialites (stromatolites) along the South African coastline is potentially informative from this perspective. These stromatolites form within the peritidal zone, at the interface of groundwater seepage and periodic marine incursion, forming pools trapped by the accreting fabric. The aim of this thesis was to characterise the ecosystem dynamics of a representative selection of the South African locations. During a comprehensive monthly assessment over an annual cycle, as well as for additional seasonal collections, physico-chemical measurements were monitored together with biological components such as benthic and pelagic microalgae as well as the invertebrate fauna inhabiting the stromatolite pools. These components were then assessed in terms of the potential physical and biological drivers which might explain patterns of variability. Finally, to link all of the ecosystem components, a food-web analysis was conducted, to determine the trophic linkages and, importantly, the reliance by the various consumer organisms on the stromatolite material as a food resource. Results show that the stromatolite pools are driven by a regular interplay between freshwater and marine salinity states, this being determined by tidal amplitude and ocean storm cycles. Furthermore, marine incursion represents the primary source of phosphorus for the stromatolite pools, while available nitrogen is consistently provided by the freshwater inlet stream at each site. This results in an optimum zone of primary biomass within the main stromatolite pool supported by nutrient conditions, while the shifts in salinity state occurring over a weekly tidal schedule likely exclude organisms and macrophytes that are not halotolerant. This is reflected in the benthic microalgae that form the stromatolite accretions in that they are primarily driven by salinity conditions, in addition to seasonal patterns. Interestingly, the variable nutrient conditions, both between sites and temporally, did not contribute as an important driver of the benthic microalgae but did significantly relate to the pelagic microalgae (phytoplankton). This, together with the higher biomass of benthic microalgae compared to its pelagic counterpart, suggests that the stromatolite pools are a benthic-driven system. The short duration of water retention within the stromatolite pools as a result of the constant freshwater inflow, likely also precludes nutrient build-up and favours the benthic, sessile ecosystem component, especially the stromatolite-forming microalgae. In terms of the metazoan infauna, the South African stromatolite pools support a persistent assemblage. This might be surprising given the apparently destructive influence of grazing and burrowing animals on microbial mats in terms of restricting the formation of layered accretions. However, metazoans that burrow within the stromatolite fabric were observed to coexist with clear, layered accretions. This supports the observations in some other modern microbialite habitats to suggest that metazoan disruption is clearly not the only or primary factor responsible for modern microbialite scarcity. When assessing the possible drivers of the metazoan community occupying the stromatolite matrix, both salinity patterns and resource conditions in terms of nutrient supply and macroalgal cover were consistently best related to infaunal abundance and presence/absence. This further demonstrates the role of salinity conditions in terms of providing a habitat that is restrictive to most metazoan organisms, while also suggesting that the metazoans are responding to macroalgal rather than the stromatolite microalgal conditions. To further develop this observation, the results from the stable isotope work clearly reflect a dominance of pool macroalgae in the diets of invertebrate consumers, with little to no stromatolite material consumed. This suggests that there is limited apparent destructive grazing influence by the metazoans on the stromatolite matrix, in addition to the burrowing bioturbation mentioned previously. Furthermore, the metazoan grazers may be indirectly benefitting the stromatolites by restricting macroalgal biomass, which might otherwise outcompete its microalgal counterpart. This study provides a valuable understanding of benthic-driven peritidal stromatolite ecosystems, and also, from a geological perspective of past stromatolite habitats, suggests some of the mechanisms as to why metazoans may be able to coexist with layered microbialites. Given the threats to similar habitats globally, especially in terms of water resources, management measures necessary to ensure stromatolite persistence in modern environments such as these are proposed. The possible ecological role of peritidal stromatolite habitats within the broader environment, as well as recommendations for future work, is also contextualised.
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Date Issued: 2017

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