Influence of increased processing speed on the microstructure evolution and mechanical property relationship in friction stir welding of AA5182-H111 (T500)
- Authors: Bernard, Dreyer
- Date: 2016
- Subjects: Friction stir welding , Aluminum alloys -- Welding
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/7322 , vital:21319
- Description: Friction stir welding of 5xxx series aluminium is generally carried out at low travel speeds, which limits the commercial applications of this process. This manuscript discusses the dynamic eformation characteristics of AA5182-H111 (T500), which allowed a travel speed of 1500 mm/min to be realised. This was achieved by using a spindle speed of 500 rev/min; the same as that required to make a weld of 200 mm/min. The thermal cycles, microstructural evolution due to tool / work-piece interaction, and the local microstructural and mechanical properties of the completed weld are discussed for a travel speed for 200 mm/min and 1500 mm/min. At a rate of 200 mm/min, heat generated due to contact between the shoulder and work-piece surface was transferred ahead of the tool, driving dynamic recrystallization which lowered the flow stress. Hereafter the material entered the stir zone where it was extruded around the pin during a process of continuous dynamic crystallization. At a travel speed of 1500 mm/min, the rate of heat conduction ahead of the tool was not rapid enough, and the material was deformed at low temperatures. A low weld pitch rotations per unit length travelled) was required to ensure that the material was sufficiently strained, to allow the formation of geometric necessary boundaries, which resulted in grain subdivision. The number of high angle grain boundaries was increased through subdivision, thus, increasing the nucleation sites for dynamically recrystallized necklace grains to form. In the absence of heat conduction from the shoulder, the high plastic strain ahead of the tool provided the energy required to drive dynamic recrystallization. Heat was generated from the high plastic strain and during recrystallization, where the stored plastic energy was adiabatically released. Once the material entered the stir zone, the high strain rates associated with the tool rotation which drove dynamic recrystallization that allowed the material to reach high levels of strain, resulted significant grain refinement. The weld zone of the 200 mm/min displayed weld a slight increase in yield strength, with respect to the parent material, due to grain refinement to 10 μm, while the yield strength of the 1500 mm/min weld was significantly increased due to grain refinement to 5 μm. The high weld speed did, however, generate high tensile residual stresses. This work is not only significant for the field of friction stir welding, but also in terms of material processing. The dynamic deformation characteristics associated with Al-5Mg-Mn, alloys which was observed ahead of the tool, is of high value in processes where plastic deformation is applied to improve the mechanical properties of these alloys.
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- Date Issued: 2016
Institutional change, institutional isolation and biodiversity governance in South Africa: a case study of the trout industry in alien and invasive species regulatory reforms
- Authors: Marire, Juniours
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/639 , vital:19977
- Description: The world, in recent decades, has witnessed an incalculable surge in global “wicked” policy problems that have long-term, and most often irreversible, impacts, not least terrorism, climate change, biodiversity losses and desertification. Wicked problems are wicked because there is no single epistemological system that can adequately coordinate policy action for addressing them. Literature abounds with international case studies of opposition to national institutions that are designed to put into effect global and regional policies for resolving wicked problems. This raises questions about what constitutes reasonable institutions, how such institutions can be designed and why societies sometimes fail to develop such institutions despite the obvious need for them. As a point of entry into these issues, the thesis adapted and extended the Northean (2007, 2012) macro meta-theoretic framework for studying the violence-development relationship, which focuses on the role of political and economic competition in the emergence of ‘right’ institutions that promote development, while containing violence. The Northean framework conceptualises two mutually exclusive social orders – the limited access order and the open access order – which provide the socio-cultural context for the evolution of specific institutions. The macro meta-theoretic framework was transformed into a micro metatheoretic framework in such a way that the limited access order and the open access order co-existed in the evolution of specific institutions. This reconceptualisation built on Bromley’s (2004, 2006) two realms of public policy: the realm of reasons (legislative-judicial system) and the realm of rules (administrative system) as well as the feminist concept of epistemic violence, which broadened the concept of violence from being exclusively physical to including the sociocognitive. The feminist concept of epistemic oppression logically fitted into, and became a new sub-category of, Commons’ (1899, 1924, 1934) theories of sovereignty and negotiational psychology. The innovations showed that either of these realms can be a limited access order, while the other can be an open access order or both can be open access orders or both can be limited access orders. The conceptual innovations were then used as an interpretive scheme in analysing the evolution of the South African invasive alien species regulatory reforms under the National Environmental Management: Biodiversity Act of 2004, using a case study of the trout sector, which was the most opposed to the reforms. There was a general perception among socioeconomic sectors that utilise invasive alien species that the regulatory reform processes for the governance of such species had institutionally isolated the sectors. Because of this perception, the regulatory reform process was contested, and implementation of the Fifth Chapter of the Act, which deals with the governance of invasive alien species, was delayed for nearly a decade. The thesis evaluated whether institutional isolation existed and how and why it came to be since it has implications for the reasonableness of emerging regulatory institutions, economic performance of sectors and efficient allocation of fiscal resources in institutional design processes. A mixed methods methodology was used, which included data analysis techniques such as semiosis, exploratory factor analysis, econometric estimation and document analysis. Policy documents, an online survey and key informant interviews comprised the data. The findings suggested six dimensions of institutional change that a theory of institutional change might have to address: the origin and continuity of pecuniary institutions; selfreinforcing mechanisms of the limited access policymaking order; succession and disbandment of the limited access policymaking order; exclusivity of negotiations in institutional design; tiers of institutional isolation; and the role of administrative discontinuities. Findings suggested that institutional isolation existed in the regulatory process, manifesting in three forms: administrative isolation, epistemological isolation and sectoral isolation. Administrative isolation was the most complex of the three in that it also involved a less obvious process of institutional isolation in the form of administrative redefinition of opportunity sets that were already legislatively redefined. The mechanisms of institutional isolation through which administrative isolation was sustained were administrative financing of research and careerism. The two mechanisms created a revolving door-type scenario through which invasion biologists supplied the administrative agency with candidates for senior (decision making) positions and the administrative agency, in turn, demanded specific types of knowledge over which the same epistemic community had a monopoly. The revolving door-type scenario was found to ideologically and physically entrench invasion biologists into the regulatory community. The consequence of the entrenchment was institutional hegemony, which manifested itself through the mechanism of epistemic violence insofar as the invasion biologists became the epistemic arbiters about what kinds of ideas and institutions really mattered in the governance of invasive alien species. Econometric estimates suggested that the extent to which an emerging institution is perceived to be reasonable by regulated sectors depends on the extent to which the institution is designed in a participatory and inclusive manner (that is, using integrative knowledge systems), the extent to which the designers used credible evidence and contextualised international evidence as well as the extent to which the emergent biodiversity governance institution was anthropocentric. However, findings suggested that the South African regulatory reform process fell short on all these four dimensions of reasonable institutions, which is characteristic of institutional design process shaped by hegemonic social imaginaries, resulting in institutional isolation. Emerging from the findings are several theoretical insights. Bush’s (1987) concept of institutional spaces under the Veblenian Dichotomy was extended, the result of which was identification of two stable institutional equilibria – one ceremonial and another instrumental. The ceremonial equilibrium was a typical limited access policymaking order and was responsible for the historical and present emergence of regressive institutions. Findings also suggested that the entrenched invasion biologists ceremonially encapsulated the knowledge fund that had been accumulated since the 1980s, which could have facilitated the consensual design of regulatory institutions for invasive alien species without protracted controversy. Findings suggested that a limited access policymaking order could only be disbanded by the intervention of an external sovereign agent (in this case the office of the state president) since the administrative agency, and the epistemic community that advised it, adopted the solutions that were empirically tested and proposed in the 1980s only after the intervention of the external sovereign agent. The instrumental equilibrium repealed the contested prisoner’s dilemma that was characteristic of the policy process and turned it into an assurance policy game by facilitating the identification of common interests. This finding logically links the study to a recent theoretical development in institutional theory – Ordonomics – which focuses on the causality between ideas and institutions. The findings imply that it is possible to design reasonable institutions as long as integrative (transdisciplinary) knowledge systems, including the non-scientific knowledge of the resource users, are incorporated. Integrative knowledge systems facilitate semantic innovations, which create social DNA, but epistemic violence destroys social DNA. They also imply that reliance on unidisciplinary knowledge systems in institutional design induces a large and inefficient transaction cost burden of public policy on the fiscus and private agents alike because of the inevitability of controversy, especially for wicked policy problems.
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- Date Issued: 2016
Integrated Algae Pond Systems for the Treatment of Municipal Wastewater
- Authors: Mambo, Mutsa Prudence
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5960 , http://hdl.handle.net/10962/d1021258
- Description: Integrated algae pond systems are a derivation of the Oswald designed advanced integrated wastewater ponding system, and combine the use of anaerobic and aerobic bioprocesses to effect wastewater treatment. Integrated algae pond system technology was introduced to South Africa in 1996 and a pilot plant was designed and commissioned at the Belmont Valley wastewater treatment works in Grahamstown. Previous studies showed that this system delivered a final effluent superior to most pond systems deployed in South Africa but that it was unable to meet the general standard for nutrient removal and effluent discharge. This study was initiated to re-appraise integrated algae pond systems and to assess the potential of the technology as an effective municipal sewage treatment system. And more...
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- Date Issued: 2016
Investigating the nature of the linguistic challenges of the Department of Basic Education (DBE) 2013 Grade 4 Mathematics ANAs and learners’ and teachers’ experience of them.
- Authors: Sibanda, Lucy
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2079 , http://hdl.handle.net/10962/d1021312
- Description: The underperformance of South African learners in literacy and numeracy is a source of grave concern, especially at the transition from Grade 3 to Grade 4. The challenge that complicates this shift is to some extent linguistic, since at Grade 4 in South Africa the majority of learners begin learning in English, which is an additional language for most. The study adopts a sociocultural view of language and learning. Vygotsky’s influential theoretical work on language and learning, in which language is considered central to learning and learning is a social process embedded in sociocultural settings, informs the study. The introduction of the Annual National Assessments (ANAs) across primary and secondary grades in South Africa in mathematics and literacy in 2011 provides the context for this research. It is against this background that the present study aimed, through a case study approach of three Grade 4 classes of English additional language (EAL) learners, to achieve four things, namely: to investigate the linguistic challenges of the 2013 Grade 4 mathematics ANAs; to analyse the learners’ written responses to the 2013 mathematics ANA items; to explore the 2013 Grade 4 learners’ difficulties and experiences of the 2013 mathematics ANAs, and to investigate the Grade 4 mathematics teachers’ perspectives of the language of the ANAs. In order to achieve these aims, the data was collected in four phases. The first phase of the study addressed the nature of the linguistic challenges of the Department of Basic Education Grade 4 mathematics ANAs. Data collection occurred in two parts: 1) Comparing Grade 4 ANAs to exemplars provided and 2) Analysing the language of the 2013 mathematics ANAs. This was done through content analysis and Shaftel et al.’s (2006) linguistic complexity checklist. Findings for part 1 of the study revealed that there were several inconsistencies in the questioning format and language used in the ANAs and in the exemplars. Findings of the content analysis done on the 2013 mathematics ANA test items using Shaftel et al.’s (2006) linguistic complexity checklist and Vale’s (2013) Linguistic Complexity Index formula point to many linguistic complexities in several test items, particularly in relation to recurrent use of: 7 or more letter words, homophones, prepositional phrases and specific mathematics vocabulary across the majority of questions. In phase 2, the analysis of 106 learners’ written responses for the 2013 mathematics ANA questions revealed that for many of the questions the language used was unfamiliar for Grade 4 learners using English as an additional language. This was aggravated by the inclusion in the ANAs of linguistic forms learners would not have encountered in their workbooks or exemplars intended to prepare the learners for the assessments. Therefore, linguistic complexity of items was a key contributing factor to learners’ poor performance in the test. In the third phase, the quantitative and qualitative analysis of the 26 learners’ interviews revealed that during the task-based interviews, learners experienced difficulties in the following skills: reading, comprehension, transformation, process and encoding. The greatest difficulties were experienced in comprehension and in reading, especially in the two classes where the learners were less proficient in the English language. The fourth phase, in which two Grade 4 mathematics teachers’ perceptions of the linguistic demands of the Grade 4 mathematics ANAs were presented and analysed, the teachers’ perceptions indicated that the mathematical language was mostly too difficult for the Grade 4 learners. Teachers also were of the opinion that learners’ reading skills were poor and they struggled to comprehend what they read. A dilemma regarding whether teachers should assist learners during the ANAs, satisfying the local needs for mediating the language or whether they should comply with the ANA policy which states that they may not assist learners was expressed by one of the teachers. A range of language challenges that teachers managed with various strategies were raised. These included one teacher’s use of code-switching during the teaching of mathematics. The study concludes with implications and recommendations. These include that test designers should minimise the language complexity of test items, especially in the early transition grades of learning in English. Research should be conducted on possibilities for allowing teachers to provide linguistic mediation to ANA questions in these transition years of learners learning in English.
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- Date Issued: 2016
Isithako sohlahlubo-bunzululwazi-sakhono kwiimbalo zikaSaule: iinoveli ezintathu = decontsructive stylistic critique of Saule' s writings: the case of three novels
- Authors: Jaxa, Nontembiso Patricia , Kwatsha, Linda Loretta
- Date: 2016
- Subjects: Xhosa literature -- Criticism, Textual , Literature -- Black authors -- History and criticism , South African literature -- History and criticism , Saule, N -- Criticism and interpretation , Saule, N -- Literary style
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/7762 , vital:23830
- Description: Kule ngxoxo kuqwalaselwa ukugqwesa kwesiThako Sohlahlubo-buNzululwazi-sakhono kuhlalutyo loncwadi. Olu phando lugxile ekuduliseni ukuba akukho luzalwano luthe ngqo, kwaye lusisigxina phakathi kwegama nentsingiselo, ngenxa yobumbaxa beentsingiselo zegama. Esi siThako siludondolo ekusinyelelwa ngalo kolu phando, ukuqaqambisa ukuba iitekisi azinantsingiselo izinzileyo. Ke ngoko ibe ayinabunyani mpela ingcamango yokuba igama linokunanyatheliswa intsingiselo ethile, ze loo ntsingiselo ibange ubuntsusa. Ingxoxo yophando, iphendula imibuzo ebuza ubuni besiThako Sohlahlubo-buNzululwazi-sakhono, nokuchana kwaso ekuhlalutyeni iitekisi zoncwadi. Imibuzo ikwabuza izizathu zokungazinzi kwentsingiselo yetekisi, nokungabi nakwalatheka ncam kwentsingiselo ajolise kuyo umbhali, ngotolo lwakhe oluluchongo-sigama. Le mibuzo iyaphenduleka kubuthumbu bengxoxo. Ingxoxo idandalazisa ukunzotshoba kwesi siThako kuhlahlubo, kuqanyelwa ngeengcingane zaso eziphambili. Ukuphendulwa kwemibuzo yophando, kufezekisa iinjongo zophando. Iinoveli ezichongelwe uphando, ziinoveli ezintathu zikaSaule, ezizezi: Ukhozi Olumaphiko, Umlimandlela kunye no-Vuleka Mhlaba, azikhethelwanga kuthelekiswa koko kukudandalazisa elubala ukunyanisa kwesiThako Sohlahlubo-buNzululwazi-sakhono, malunga nomba weentsingiselo. Ngazo, kudula ubunyani bophindaphindeko lwegama elinye kwimixholo ngemixholo, lizale iintsingiselo ezahlukileyo. Kanti, kukwadandalaza ukuba intsingiselo yegama ayixhomekekanga kumxholo, iyakwazi ukutyekeza ngaphaya kwawo, liveze nezinye iintsingiselo. Olu phando lungaluncedo kakhulu kubafundi nootitshala kuba kanye luphethe umba wokuhlalutywa kweetekisi, ngendlela ekhuthazwa yiNkcazelo yePolisi yeKharityhulam nokuHlola (2011). Ebethelela ukuba kufundo loncwadi kufuneka abafundi bayiqhaqhe ukuyihlalutya itekisi ukuze kuvele indlela eyakhiwe neyakheke ngayo, oko ke kukuHlahluba. Kanti ke nakubahlohli lungaluncedo kuba lutyhila okuninzi ngesiThako Sohlahlubo-buNzululwazi-sakhono. Ekuxoxeni, isiThako sobuNzululwazi Mlando-mbali, kurhatyulwe kuso, ukuxhasa imiba ethile kuphando. Ingxoxo Yahlulwe yazizahluko ngolu hlobo: Isahluko sokuqala, sidandalazisa ingxubakaxaka ethunuke yandulula uphando olu. Kwabekwa iinjongo, iziphumo-njongo zophando nemibuzo ekuza kucangcathwa kuyo kuphando. Kwaphengululwa iincwadi zeengcali kwisi-Thako Sohlahlubo-buNzululwazi-sakhono, kwarhewulwa nesiThako sobuNzululwazi beeNkumbulo noMlando-mbali. Isahluko sesibini, luphendululo lweencwadi olunzulileyo nolunabileyo, kupendlwa izimvo ezimalunga nobuni besiThako Sohlahlubo-buNzululwazi-sakhono. Kubekelelwa, kucutyungulwa iingcingane zaso, ezibe ludondolo lophando. Isahluko sesithathu, yingxoxo. Kuphicothwa iinoveli ezichongelwe uphando, zihlahlutywa, kusetyenziswa iingcamango neengcingane zesiThako Sohla-hlubo-buNzululwazi-sakhono. Ikakhulu kuqwalaselwa indlela izibini ezichasana ngokulinganayo ezivela ngayo. Kuduliswa ukuminxiselwa kwezo zikwinqanaba elingezantsi. Isahluko sesine, ingxoxo iyaqhuba, kuqwalselwa ukusetyenziswa kwamaze-nge nemiqondiso, neentsingiselo ezivelayo, nokwahluka kwazo, okukhokelela ukuba utekisi ibe nobuvumephika. Isahluko sesihlanu, uphando luqhubeka kudandalaziswa ukusetyenziswa kwezandi, isigama sokuchaza nezafobe, nemifanekiso-ngqondweni eyakhiwa zezi zixhobo zoncwadi, ze kuphendlwe iintsingiselo nefuthe lazo kwitekisi. Isahluko sesithandathu sigxile ekusetyenzisweni kwembali kuncwadi, ngendlela evuselela iinkumbulo. Kuso nakuba kuhlahlutywa kodwa kunce-diswa ngokurhabula kwisiThako sobuNzululwazi beeNkumbulo noMlando-mbali.
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- Date Issued: 2016
Job Engagement and Coping Strategies as Moderators of the Relationship between Occupational Stress and Burnout among Police Officers in the Eastern Cape, South Africa
- Authors: Dywili, Mtutuzeli
- Date: 2016
- Subjects: Police -- Job stress -- South Africa -- Eastern cape Job satisfaction -- South Africa -- Eastern Cape Employee motivation -- South Africa -- Eastern Cape Work -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/7697 , vital:30707
- Description: Police work in South Africa is demanding and stressful. Literature reveals that occupational stress when fully manifest amount to emotional burnout. It was therefore the aim of this study to examine job engagement and coping strategies as moderators of the relationship between occupational stress and burnout among police officers. Using a sample of 377 police officers from the Eastern Cape, South Africa, data was collected using various scales namely; the Effort – Reward Imbalance (ERI) questionnaire (occupational stress), the Maslach Burnout Inventory – General Survey MBI-GS (emotional burnout), the Utrecht Work Engagement Scale (job engagement), and the Coping Orientation to Problems Experienced questionnaire (coping strategies). Correlation tests and regression analysis were ministered on the data to test the research hypotheses. The major finding of the study indicated that job engagement and coping strategies collectively significantly moderate the relationship between occupational stress and emotional burnout. However, job engagement on its own was reported to be an insignificant moderator of the relationship between occupational stress and emotional burnout.
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- Date Issued: 2016
Land-use effects on mammal communities in the Fish-Kowie corridor, Eastern Cape, South Africa, with particular reference to carnivores
- Authors: Kok, Armand du Preez
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/561 , vital:19970
- Description: Human population growth is causing an increase in habitat transformation on a global scale, and this transformation is driven by changes in land-use practices. One consequence of habitat transformation is the negative effect it can have on mammal communities, especially carnivores. Carnivores are important components of ecosystems as they play an essential structuring role, but also often come into conflict with people. I studied the impact of land-use on mammalian diversity, the attitudes of landowners/managers towards carnivores, the distribution of carnivores, and the interactions among carnivore species in the Fish-Kowie corridor (FKC), an area of conservation concern, in the Eastern Cape, South Africa. Livestock and game farming are the two dominant land-use types in the FKC. Carnivore distribution data were collected between 2012 and 2014 using a robust camera trap survey that consisted of 432 camera stations (216 on livestock and 216 on game farms). In addition, the attitudes of 55 landowners/managers were assessed using semi- structured questionnaire interviews that were conducted in person. My results revealed that mammal diversity was similar on the two land-use types. However, individual species differed in their distribution on the two land-use types. In general, both livestock and game farmers had negative attitudes towards carnivores in the FKC, due to their depredation of valuable livestock and game species. Black-backed jackals (Canis mesomelas), caracals (Caracal caracal), leopards (Panthera pardus), and brown hyaenas (Parahyaena brunnea) were considered the most problematic carnivores, but sensitivity to land-use varied among these four species. Black- backed jackals had the highest occupancy rates of all four predators and were 3.8 times more likely to occupy sites on game farms compared to livestock farms. By contrast, leopards and brown hyaenas were only detected on game farms, and caracals did not appear to be sensitive to the effects of land-use. In general, the interactions among carnivores were weak and were likely driven by carnivore diversity, resource partitioning, and anthropogenic pressures. While there were many subtle differences in the distribution of mammal species and human attitudes towards wildlife on livestock and game farms in the FKC, there were also many similarities. My study has produced results that can be used by the FKC community to better understand how mammals and humans interact across the landscape, information that will ultimately contribute to future conservation planning in the area.
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- Date Issued: 2016
Leonotis leonurus: understanding the mechanism of anti-diabetic action and investigating a nano drug delivery system
- Authors: Odei-Addo, Frank , Levendal, Ruby-Ann
- Date: 2016
- Subjects: Diabetes Plant extracts
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/13116 , vital:27153
- Description: Diabetes mellitus is a metabolic disease characterised by hyperglycaemia resulting from defects in insulin secretion, insulin action, or both. The leaf extract of Leonotis leonurus and its active compound marrubiin, have been shown to possess anti-diabetic, antiplatelet, anti-inflammatory and anti-coagulation activity. In the present study, the mechanism by which L. leonurus and marrubiin exert their anti-diabetic properties, the cross-talk between the peripheral tissues and a nano drug delivery system were investigated. Marrubiin in the plant extract was effectively quantified by an optimised reversed phase highperformance liquid chromatography (HPLC) protocol using a pentafluorophenyl (PFP) column with water and acetonitrile (50:50) as mobile phase, and a flow rate of 1ml/min. The chemical structure was determined using liquid chromatography-tandem mass spectroscopy LC-MS/MS. Real-time quantitative polymerase chain reaction (RT-qPCR) gene expression of selected adipokines and proteins implicated in Type-2 diabetes (T2D) were investigated in specific peripheral tissues isolated from an in vivo obese rat model. An in vitro cell culture model was used to determine the crosstalk between the peripheral tissues and pancreatic (INS-1E) β-cells. Various nanoformulations of L. leonurus extract were prepared and their effect on cytotoxicity (in Chang liver and INS-1 cells), insulin-mediated glucose uptake (Change liver cells) and insulin secretion (INS-1) were investigated. The average yield of marrubiin from the plant extract was 10% (n=3), with a molecular mass of 333.20Da and a molecular formula of C20H29O4 +. Results from the in vivo study showed that the L. leonurus extract significantly (p<0.05) enhanced the gene expression of adiponectin, peroxisome proliferator-activated receptor gamma (PPAR-γ), glucokinase (GK), uncoupling protein-2 (UCP-2) and reduced leptin in adipose tissue, but resistin, glucose transporters (GLUT), fatty acid synthase (FAS), insulin receptor substrate -1 (IRS-1) and phosphoenolpyruvate carboxykinase (PEPCK) gene expression were not affected. Marrubiin decreased gene expression of leptin and resistin, and increased IRS-1 and glucokinase in adipose tissue. In liver and muscle tissues, marrubiin and the L. leonurus extract reduced gene expression of PPAR-γ, IRS-1, glucokinase and PEPCK. In the in vitro crosstalk study (under normoglycaemic and hyperglycaemic conditions), conditioned medium from 3T3-L1 cells significantly (p<0.01) enhanced insulin secretion. This was not observed in INS-1E cells exposed to muscle- and liver-conditioned medium, respectively. The in vitro studies using a nanostructured lipid formulation (NLC) of the plant extract was not cytotoxic to either INS-1 and Chang liver cells. The NLC formulation significantly (p<0.05) enhanced glucose uptake in Chang liver cells and improved chronic insulin release in INS-1 cells (p<0.05). Based on the above findings from the in vivo and in vitro studies, both L. leonurus and marrubiin exerted an insulinotropic effect via adipose tissue on pancreatic β-cells. The findings in the in vivo study showed that marrubiin and the L. leonurus extract were employing their major anti-diabetic action via the adipose tissue.
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- Date Issued: 2016
Life history of the maritime platygastrid Echthrodesis lamorali Masner 1968 (Hymenoptera: Platygastridae: Scelioninae)
- Authors: Owen, Candice Ann
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/837 , vital:19995 , 10.21504/10962/837
- Description: Echthrodesis lamorali Masner 1968 (Hymenoptera: Platygastridae, Scelioninae) is an intertidal parasitoid wasp that uses the eggs of the maritime spider, Desis formidabilis O.P. Cambridge 1890 (Araneae: Desidae), as a host. This species is one of only three known maritime parasitoids globally, and is the only known spider egg parasitoid that attacks its host within the intertidal region in southern Africa. Originally described from ‘The Island’, Kommetjie (Western Cape, South Africa), this shore was the only known locality of the species at the commencement of this thesis. Furthermore, the extent of the parasitism pressure the wasp exerts on D. formidabilis was largely unknown, along with its basic biology (drivers of its broad-scale and fine-scale distribution patterns; parasitism incidence; and sex ratios) and morphological and physiological adaptations for living within the frequently saltwater-inundated environment. This thesis unravelled these aspects, as well as experimentally provided data for many components of the life history of E. lamorali that had only been hypothesized by other authors, at a variety of scales, from the country-wide ecosystem, to single shores, and finally to the scale of the individual. While the distribution of E. lamorali was found to be much wider than previously thought, it remained restricted to the shores of the Cape Peninsula (Western Cape, South Africa). The host spiders were located throughout a much wider distributional range than the wasp, from East London in the east to the Peninsula, but some behavioural and morphological differences were found between those within and outside of the range of the parasitoid, suggesting range-limitation imposed by the host on E. lamorali. This limitation may be strengthened by the general lack of suitable shore types within the close vicinity of the Peninsula. Modelling using macro-climatic conditions suggested that maximum temperatures and humidities were also largely limiting to E. lamorali, although these patterns were not observable in the micro-climates in which the species survives. The wasp populations and spiders within the range of E. lamorali as identified in Chapter 2 were assessed to determine any preferences for local conditions, including location along the Peninsula, nesting sites and intertidal zones within single shores, using AICc modelling, which detected parasitism patterns in D. formidabilis and E. lamorali populations, as well as the sex ratios in the latter species. The models showed that the spider population size and distribution was more influenced by bottom-up factors such as abiotic components of the shore than by parasitism, which only showed density dependence with the host at certain scales. Both host and parasitoid populations illustrated a preference for the middle zone on single shores. Observed spider nest characteristics suggested opportunistic nesting behaviour in the species, although preference was shown for construction along an east-west orientation and in locations with low sun exposure. Along with larger population sizes on the west coast over the east coast (not reflected by E. lamorali), these observations suggest that D. formidabilis prefers cooler environments. Spider brood success was 50% in unparasitized egg-sacs, but this figure halved when E. lamorali gained access to the eggs (of which 100% within a single compartment were parasitized each time). Encapsulation of the embryo was found to be positively correlated with parasitism, indicating some form of host resistance. Resultant parasitoid broods illustrated a strong female bias in the species, as is common for this group of insects. The life history of E. lamorali was then assessed at a smaller scale, that of the individual. Scanning electron microscopy of whole E. lamorali specimens and light microscopy of sectioned specimens demonstrated no morphological adaptations in the trachea and spiracles to cope with saltwater inundation. On the other hand, respirometry experiments categorically demonstrated that the species copes with inundation through the formation of a physical gill over the full habitus, and the induction of a state of torpor to reduce metabolic needs, when submerged. This precludes the need for any further morphological adaptations. Determination of the wasp’s critical thermal tolerance illustrated a wide temperature range with a particularly cold lower limit of -1.1ºC ± 0.16, suggesting the presence of related genera or ancestors in much colder environments. With a much broader distribution than previously thought, and the inclusion of the distributional range of E. lamorali within the Table Mountain National Park, this species is being effectively conserved and managed through the umbrella-conservation of the park. Links to the host proved to vary at differing scales, proving the need for scale considerations to be included in other similar biological and ecological studies. Finally, the species showed physiological adaptation to its intertidal existence. Echthrodesis lamorali, the only discovered maritime spider egg parasitoid in Southern Africa, displayed unusual characteristics at every scale of its life history and as such, warrants further investigation.
- Full Text:
- Date Issued: 2016
Links between valley confinement, landforms and vegetation distribution in a semi-arid valley floor environment, Baviaanskloof, South Africa
- Authors: Smith-Adao, Lindie B
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/953 , vital:20006
- Description: Although a large body of international literature has advanced our understanding of river systems, a considerable amount of gaps exit in the knowledge of dryland systems. River systems reflect complex interactions between biophysical processes and patterns. Understanding how processes generate observed patterns and, in turn, how patterns influence processes is crucial to understanding river structure and function. It requires an interdisciplinary approach in both research and resulting applications. The aim of this thesis was to examine the relationship between valley confinement, fluvial style, valley floor morphology and vegetation in the semi-arid environment of the Baviaanskloof river catchment, South Africa. This interdisciplinary investigation used a mixed method approach that involved desktop analyses and field surveys to understand dynamics at multiple scales, from the whole catchment to local (site, reach and quadrat or sample plot) scales. The desktop analyses included historical rainfall patterns and climate extremes, aerial photograph time-series and remote sensing greenness indices, and the field surveys focussed on cross-valley landform profiles, groundwater depth levels, sediment size distribution and soil chemistry, and vegetation distribution patterns. Based on the integrative assessment of these techniques a framework was developed of the links between valley confinement, surface-groundwater interaction, hydrogeomorphic processes and landforms, vegetation and human activities. Study findings highlighted the fact that very strong links exist between these factors. In this semi-arid area water availability (groundwater and streamflow conditions) was the primary control on valley floor vegetation composition and patterning. One group of species was associated with the wetted channel reaches at confined and semi-confined valley settings, while the other was associated with dry bed channel reaches at unconfined valley settings. The analyses also indicated that the environmental variables which best explained the variation in vegetation at the differing geomorphic landforms were related to landform position (elevation and distance), sediment size (fine and coarse sand) and available phosphorus (i.e. human impacts). The different plants, in turn, also affected landforms through their influence on sediment erosion, transport and deposition. Specially, they build, maintained or modified geomorphic landforms at confined, semi-confined and unconfined valley settings across the valley floor. Valley confinement was a primary control influencing hydrogeomorphic processes and their associated landforms. Alluvial fans and terraces acted as critical additional controls at especially the unconfined valley setting. Implications for restoration efforts in the catchment included strategies that took cognisance of: active revegetation on floodplain surfaces related to former agricultural fields; channel switching associated with the highly dynamic and unpredictable nature of geomorphic features; unstable multi-thread braided channels in the unconfined valley setting; and the selection of representative monitoring sites.
- Full Text:
- Date Issued: 2016
Managing change in organisational environment
- Authors: Markova, Elena
- Date: 2016
- Subjects: Organizational change , Conflict management , Teams in the workplace
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8129 , vital:25017
- Description: Twentieth century has set an unprecedented pace of change, which seems to be ever increasing. The changes are transforming every sphere of social life including business and organisational life. Globalisation has made organisational structures flatter but wider in reach. Advancements in information and communication technologies have made teams larger through vast and powerful information networks. These forces are triggering the reshaping and restructuring of every major industry worldwide nowadays. The main research aim of this study is to explore how organisational conflict is affected by change (and vice versa) in order to work out a set of recommendations which shall take form of practical intervention strategies for the improvement of organizational effectiveness by mitigating the dysfunctions of a conflict and adjusting employees' styles of handling interpersonal and intergroup conflict. Workplace conflict is an everyday reality. It is an inevitable result of human interaction in a competitive environment of the workplace. So, according to this assumption, conflict is not something vicious and destructive, but an intrinsic part of human interaction. Then, the conflict is not a problem in itself, the way it is managed is what defines whether the conflict is destructive or not.
- Full Text:
- Date Issued: 2016
Measuring the performance of the banking sector in Zimbabwe
- Authors: Abel, Sanderson
- Date: 2016
- Subjects: Banks and banking -- Zimbabwe , Bank profits -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/5110 , vital:20806
- Description: The measurement of the banking sector performance in Zimbabwe is motivated by the unique developments that typified the sector during the period 2009-2014 after emerging from an economic crisis. The Zimbabwean economy returned to stability and growth in 2009, after a decade long economic decline. Economic stability brought about growth in deposits, loans, assets, capitalization and profits during this period. The banking sector has been accused of excessive profiteering through overpricing their products, which culminated in the intervention by the authorities in the sector. The interest rates spread, fees and other charges were presumed to be high which motivated the need to understand whether the banking sector is efficient or inefficient given the high interest rate spreads between the deposit rates and lending rates. Furthermore the high interest rates have raised the question of whether banks were exploiting their market power to price their products highly or whether their prices were determined by the dictates of market forces. Continued profitability of the sector also called for an investigation into what was driving the persistence of profitability over time. The primary objective of this research was to measure the performance of the banking sector during the period 2009-2014. The study contributes to the empirical literature by measuring and assessing the drivers of banking sector competition, efficiency and profitability and applying them at much disaggregated levels. This study also contributes to the debate on the relationships among the performance measures of competition, profitability and efficiency. The study adopted a number of methods which contributes to the array of tools central banks can employ to measure bank performance. The study employed a number of methodologies to measure the competition, efficiency and profitability performance of the banking sector. Competition was estimated using the new empirical industrial organisation methods of Panza and Rose (1987) and the Lerner (1934) Index was used. Cost and revenue efficiency was estimated using the two step methods of Data Envelopment Analysis followed by the Tobit regression method. An assessment of the persistence and drivers of profitability was measured using the Generalised Method of Moments. This study shows that the banking sector was operating under monopolistic competition market structure. This implies that banks held some market power as a result of product differentiation due to unique features such as brands, image and advertising, among others. The study indicates that competition increased during the period 2009-2014. Market power/competition in the banking sector during the study period was driven by capital adequacy, non-performing loans, liquidity risk, cost-income ratio, economic growth and government policy on pricing of bank products. The study suggests that the banking sector experienced an average inefficiency level of approximately 35 per cent in relationship with the best performing institutions in the sample. As a result of stability experienced in the economy, the average revenue and cost efficiency increased between 2009 and 2014. The study further established that the discord around the implementation of the indigenisation and empowerment law, coupled with the government intervention in the banking sector had a negative impact on the banking sector efficiency. It also found that efficiency is determined by market power, capital adequacy, cost income ratio, economic growth, inflation, market share and profitability. The Granger Causality test between cost efficiency and market power suggests that causality is bidirectional. On the other hand granger causality between revenue efficiency and market power is unidirectional and positive, running from revenue efficiency to market power. The result implies that policy measures should bring a balance between increasing competition and improving the revenue efficiency. The study shows that the banking sector was profitable during the period 2009 to 2014. The profitability was a reflection of a stable macroeconomic environment, typified by low inflation levels, despite the crises during this period. It further reveals that the banking sector‟s profitability persisted over time, reflecting the regulatory structure of the sector. The study established that profitability was determined by market power, non-performing loans, liquidity risk, capital adequacy, bank size and cost efficiency. This implies profitability was driven by bank specific determinants. There are a number of policy implications derived from the study. Regulatory measures such as forced consolidations can lead to excessive market power by the banking institution; hence it should be moderated. Banks should enhance credit risk because NPLs has been dragging profits. Banks should take advantage of the various measures introduced, such as the setting up of the special purpose vehicle and credit reference bureau. The government should avoid tampering with market forces as this reduces competition, efficiency and profitability and put in place measures that grow the economy as it increases the efficiency and profitability of the banking sector.
- Full Text:
- Date Issued: 2016
Mechanism and synchronicity of wheat (Triticum aestivum) resistance to leaf rust (Puccinia triticina) and Russian wheat aphid (Duiraphis noxia) SA1
- Authors: Njom, Henry Akum
- Date: 2016
- Subjects: Wheat -- Disease and pest resistance Bacterial diseases of plants Russian wheat aphid
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/2700 , vital:28056
- Description: Wheat (Triticum aestivum and T. Durum) is an extremely important agronomic crop produced worldwide. Wheat consumption has doubled in the last 30 years with approximately 600 million tons consumed per annum. According to the International Maize and Wheat Improvement Center, worldwide wheat demand will increase over 40 percent by 2020, while land as well as resources available for the production will decrease significantly if the current trend prevails. The wheat industry is challenged with abiotic and biotic stressors that lead to reduction in crop yields. Increase knowledge of wheat’s biochemical constitution and functional biology is of paramount importance to improve wheat so as to meet with this demand. Pesticides and fungicides are being used to control biotic stress imposed by insect pest and fungi pathogens but these chemicals pose a risk to the environment and human health. To this effect, there is re-evaluation of pesticides currently in use by the Environmental Protection Agency, via mandates of the 1996 Food Quality Protection Act and those with higher perceived risks are banned. Genetic resistance is now a more environmental friendly and effective method of controlling insect pest and rust diseases of wheat than the costly spraying with pesticides and fungicides. Although, resistant cultivars effectively prevent current prevailing pathotypes of leaf rust and biotypes of Russian wheat aphid from attacking wheat, new pathotypes and biotypes of the pathogen/pest may develop and infect resistant cultivars. Therefore, breeders are continually searching for new sources of resistance. Proteomic approaches can be utilised to ascertain target enzymes and proteins from resistant lines that could be utilised to augment the natural tolerance of agronomically favourable varieties of wheat. With this ultimate goal in mind, the aim of this study was to elucidate the mechanism and synchronicity of wheat resistance to leaf rust (Puccinia triticina) and Russian wheat aphid (Duiraphis noxia) SA1. To determine the resistance mechanism of the wheat cultivars to leaf rust infection and Russian wheat aphid infestation, a proteomics approach using two-dimensional gel electrophoresis was used in order to determine the effect of RWA SA1 on the wheat cultivars proteome. Differentially expressed proteins that were up or down regulated (appearing or disappearing) were identified using PDQuestTM Basic 2-DE Gel analysis software. Proteins bands of interest were in-gel trypsin digested as per the protocol described in Schevchenko et al. (2007) and analysed using a Dionex Ultimate 3000 RSLC system coupled to an AB Sciex 6600 TripleTOF mass spectrometer. Protein pilot v5 using Paragon search engine (AB Sciex) was used for comparison of the obtained MS/MS spectra with a custom database containing sequences of Puccinia triticina (Uniprot Swissprot), Triticum aestivum (Uniprot TrEMBL) and Russian wheat aphid (Uniprot TrEMBL) as well as a list of sequences from common contaminating proteins. Proteins with a threshold of ≥99.9 percent confidence were reported. A total of 72 proteins were putatively identified from the 37 protein spots excised originating from either leaf rust or Russian wheat aphid experiments. Sixty-three of these proteins were associated with wheat response to stress imposed by RWA SA1 feeding while 39 were associated with infection by Puccinia triticina. Several enzymes involved in the Calvin cycle, electron transport and ATP synthesis were observed to be differentially regulated suggesting greater metabolic requirements in the wheat plants following aphid infestation and leaf rust infection. Proteins directly associated with photosynthesis were also differentially regulated following RWA SA1 infestation and P.
- Full Text:
- Date Issued: 2016
Modelling dispersal processes in impala-cheetah-lion ecosystems with infection in the lions
- Authors: Mbava, Willard
- Date: 2016
- Subjects: Predation (Biology) -- South Africa -- Kruger National Park Endangered species -- South Africa -- Kruger National Park
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/11782 , vital:26968
- Description: The study involved the predator-prey interaction of three species namely the predator (Cheetah Acinonyx jubatus), the super-predator (Lion Panthera leo), and their common prey (Impala Aepyceros melampus). The study area is the Kruger National Park. The predator being an endangered species, faces a survival problem. It is frequently killed by the super-predator to reduce competition for prey. The super-predator also scares away the predator o_ its kills. The prey forms the main diet of the predator. The plight of the predator motivated the author to formulate disease and reaction-diffusion models for the species interactions. The purpose of the models were to predict and explain the effect of large competition from the super-predator on the predator population. Important parameters related to additional predator mortality due to presence of super-predator, the disease incidence rate and induced death rate formed the focal points of the analysis. The dynamics of a predator-prey model with disease in super-predator were investigated. The super-predator species is infected with bovine Tuberculosis. In the study, the disease is considered as biological control to allow the predator population to regain from low numbers. The results highlight that in the absence of additional mortality on the predator by the super-predator, the predator population survives extinction. Furthermore, at current levels of disease incidence, the super-predator population is wiped out by the disease. However, the super-predator population survives extinction if the disease incidence rate is low. Persistence of all populations is possible in the case of low disease incidence rate and no additional mortality imparted on the predator. Furthermore, a two-species subsystem, prey and predator, is considered as a special case to determine the effect of super-predator removal from the system, on the survival of the predator. This is treated as a contrasting case from the smaller parks. The results show that the predator population thrives well in the total absence of its main competitor, with its population rising to at least twice the initial value. A reaction-diffusion three-species predator-prey model was formulated and analysed. Stability of the temporal and the spatio-temporal systems, existence and non-existence of stationary steady state solutions were studied. Conditions for the emergence of stationary patterns were deduced. The results show that by choosing the diffusion coeffcient d2 > _D 2 suffciently large, a non-constant positive solution is generated, that is, stationary patterns emerge, depicting dispersal of species. Predators were observed to occupy habitats surrounding prey. However, super-predators were observed to alternate their habitats, from staying away from prey to invading prey habitat. In the investigation, strategies to determine ways in which the predator species could be saved from extinction and its population improved were devised, and these included isolation of the predator from the super-predator.
- Full Text:
- Date Issued: 2016
Molecular characterization of Mycobacterium bovis isolated from cattle and sputum specimens from humans in the Eastern Cape province, South Africa : public health and economic implication
- Authors: Bhembe, Nolwazi Londiwe
- Date: 2016
- Subjects: Mycobacterium tuberculosis -- South Africa -- Eastern Cape Public health -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/13238 , vital:39625
- Description: Tuberculosis (TB) is a disease caused by the members of the Mycobacterium tuberculosis complex (MTBC), which infects both animals and humans. The primary host of Mycobacterium bovis is cattle. It remains a major global health problem. About 2 billion people are thought to be infected with TB and about 1.3 million decease each year from the disease. This study is aimed at determining the prevalence of the disease, characterizing the MTBC isolates and increasing the understanding of the genetic diversity MTBC in the Eastern Cape Province of South Africa, from studying both samples from both humans and cattle. A total of 376 cattle lymph nodes were collected from two commercial abattoirs for investigations. Suspected 6 000 sputum specimens were also collected from humans (cattle farmers). All collected samples were cultured, and isolates were confirmed with a multiplex polymerase chain reaction (PCR) targeting the mpb64 and IS6110 genes. Positive isolates were tested for resistance against anti-TB drugs using the standard Lowenstein Jensen proportion method. Isolates from cattle lymph nodes were further characterized to species level, using the region of deletion 1 (RD1) and oxyR restriction fragment length polymorphism analyses. MIRU-VNTR typing and spoligotyping assays were used to further examine the genetic diversity of all strains. Obtained spoligotype patterns were matched with isolates published in the universal spoligotyping database (SITVIT2). MTBC was detected in 162 (43.09 percent) cattle lymph nodes and 156 sputum specimens. Some isolates 25.9 percent (42/162) from the cattle lymph nodes samples were resistant to rifampicin (RIF) and 98.7 percent (154/156) were resistant to isoniazid (INH) and rifampicin (RIF) (of the human sputum specimens). All cattle lymph nodes isolates exhibited the RD1 gene, and the oxyR analyses classified 96.9 percent of the isolates as Mycobacterium tuberculosis complex and 3.1 percent as Mycobacterium bovis. Twenty seven spoligotype patterns were isolated from cattle lymph nodes, with 10 shared types (SIT) consigned to 5 lineages, including Bov_4-Caprea (1.9 percent), Microti (0.6 percent) and Beijing (17.9 percent) constituting East Asian, Latin-American-Mediterranean (LAM) (3.7 percent), X (4.3 percent), MANU (3.1percent), S (0.6 percent) and 67.9 percent were orphans that were further categorized to their designated lineages (Indo-Oceanic, Euro-American and West-African 2). Ninety one percent of the isolates from humans (farmers) were grouped into 7 clusters by spoligotyping, while the remaining 9 percent was unclustered. SITs were observed in 89.6 percent of the isolates from the Beijing, LAM, X, T and S families. The Beijing family was the most prevalent strain from both human isolates (77.2 percent) and cattle lymph nodes isolates (17.9 percent), and the T (0.6 percent) and Microti (0.6 percent) families were the least detected genotypes in both humans and cattle lymph nodes. In the cattle lymph nodes, spoligotyping showed a higher clustering rate of 82.1 percent, with the lowest (HGDI) = 0.485. The 12 MIRU-VNTR clustering rate was 64.8 percent, showing a higher HGDI of 0.671. However, a combination of both methods showed a decreased clustering rate of 53.7 percent; however these methods resulted in a higher HGDI (0.676). Isolates from human sputum specimens spoligotyping showed a higher clustering rate of 89 percent with an HGDI = 0.822. The 12 MIRU-VNTR showed the lowest clustering rate of 69 percent and an HGDI = 0.940 and the combination of the methods showed a clustering rate of 78 percent and an HGDI = 0.951. The results of this study show the diversity of MTBC strains in the Eastern Cape Province and the low clustering rate indicates continuing transmission in the province. The detection of MTBC strains from slaughtered cattle lymph nodes in abattoirs confirms the risk of providing TB infected meat in markets which has serious implications for the control of TB in South Africa. The continuing spread of MTBC in South Africa threatens both the public and economic health.
- Full Text:
- Date Issued: 2016
Moringa oleifera leaf powder as a functional antioxidant additive in pork droewors
- Authors: Mukumbo, Felicitas Esnart
- Date: 2016
- Subjects: Antioxidants , Moringa oleifera , Pork -- Quality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/15354 , vital:40400
- Description: The study investigated the effect of Moringa oleifera leaf powder (MLP) on physico-chemical characteristics, antioxidant activity, antioxidant compound content and lipid oxidation in pork droëwors. Firstly, the physico-chemical properties (proximate composition, salt content, water activity (aw), pH) of commercially produced droëwors from different types of meat (beef, game, ostrich) were determined. In the second experiment beef and pork droëwors with similar fat content were produced. Physico-chemical properties and lipid oxidation (thiobarbituric reactive substances (TBARS)) during processing and 26 days of storage at 25 °C and 50percent relative humidity (RH) were measured. In the third experiment, antioxidant compounds (Total Phenolic Compounds (TPC), α-tocopherol, β-carotene) in MLP were quantified. Thereafter, 4 treatments of pork droëwors were produced, with MLP included at 0, 0.5, 1 and 2 g/ 100 g. Physico-chemical properties and TBARS were measured at intervals during drying (0, 1.5, 5.75, 27.25, 72 h) and after 7 days of storage under ambient conditions. Antioxidant activity (ferric reducing antioxidant power (FRAP)), TBARS, α- and γ-tocopherol, and β-carotene contents were measured. In the fourth experiment, three batches of droëwors were produced (C: no antioxidant, M0.75: 0.75 g/ 100 g MLP, VE: 15 mg/ kg α-tocopherol oil) and stored at 25 °C and 50percent relative humidity for 112 days. Drying kinetics and α-tocopherol contents of pork droëwors after drying were measured and the physico-chemical properties and TBARS were followed during storage. Results showed no differences (P > 0.05) in the physico-chemical characteristics of beef, game meat and ostrich droëwors; containing on average 25.8 ± 1.25 g/100 g moisture, 42.0 ± 0.10 g/100 g protein, 32.0 ± 1.68 g/100 g fat, 6.2 ± 0.13 g/100 g ash and 4.2 ± 0.10 g/100 g salt; with aw and pH of 0.79 ± 0.015 and 5.3 ± 0.05, respectively. During processing and storage, TBARS were higher (P < 0.05) in pork droëwors (maximum 3.83 mg MDA/kg DM) than in beef (maximum 0.99 mg MDA/kg DM). Moringa oleifera leaf powder contained high levels of TPC (7.5 ± 0.2 mg gallic acid eq/g) and substantial levels of α-tocopherol (76.7 ± 1.9 mg/100 g) and β-carotene (23.2 ± 2.8 mg/100 g). The FRAP, α-tocopherol and β-carotene content of pork droëwors increased (P < 0.05) proportionally with increasing levels of MLP inclusion. Lipid oxidation occurred more rapidly (P < 0.05) when MLP was not added and was similar (P > 0.05) for all MLP treatments. There was no significant effect of the inclusion of 0.75 g/100 g MLP on the drying curves and physico-chemical characteristics of the droëwors. The α-tocopherol content was higher (P < 0.05) and TBARS during storage were lower (P > 0.05) with MLP addition. The results of the current study give an overview of the composition of commercial droëwors and showed higher susceptibility to lipid oxidation in pork droëwors. Moringa oleifera leaf powder exhibited antioxidant activity in pork droëwors, inhibited lipid oxidation and increased the content of α-tocopherol in the product. It can be concluded that MLP could be used as a functional antioxidant additive in pork droëwors.
- Full Text:
- Date Issued: 2016
Nanocomposites of carbon nanomaterials and metallophthalocyanines : applications towards electrocatalysis
- Authors: Nyoni, Stephen
- Date: 2016
- Subjects: Nanocomposites (Materials) , Nanostructured materials , Electrocatalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4561 , http://hdl.handle.net/10962/d1020846
- Description: Nanohybrid materials have been prepared and examined for their electrocatalytic activity. The nanocomposites have been prepared from carbon nanomaterials (multiwalled carbon nanotubes (MWCNTs) and graphene nanosheets), cadmium selenide quantum dots and metallophthalocyanines (MPcs). The MPcs used in this work are cobalt tetraamino-phthalocyanine (CoTAPc) and tetra (4-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninatocobalt (II)) (CoPyPc). Their activity has also been explored in different forms; polymeric MPcs, iodine doped MPcs and covalently linked MPcs. The premixed drop-dry, sequential drop-dry and electropolymerisation electrode modification techniques were used to prepare nanocomposite catalysts on the glassy carbon electrode (GCE) surface. The sequential drop dry technique for MPc and MWCNTs gave better catalytic responses in terms of limit of detection, catalytic and electron transfer rate constants relative to the premixed. MWCNTs and CdSe-QDs have been used as intercalating agents to reduce restacking of graphene nanosheets during nanocomposite preparation. Voltammetry, chronoamperometry, scanning electrochemical microscopy and electrochemical impedance spectroscopy methods are used for electrochemical characterization modified GCE. X-ray photoelectron spectroscopy, X-ray diffractometry, transmission electron microscopy, scanning electron microscopy, infra-red spectroscopy, Raman spectroscopy were used to explore surface functionalities, morphology and topography of the nanocomposites. Electrocatalytic activity and possible applications of the modified electrodes were tested using oxygen reduction reaction, l-cysteine oxidation and paraquat reduction. Activity of nanocomposites was found superior over individual nanomaterials in these applications.
- Full Text:
- Date Issued: 2016
Nascent Desires: Gendered Sexualities in Life Orientation Sexuality Education Programmes and Popular Music
- Authors: Moodley, Dale Dhersen
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3274 , http://hdl.handle.net/10962/d1021260
- Description: Formal school-based sexuality education is one medium, amongst others, that recognises young people’s sexuality, but usually as at-risk and/or risk taking subjects, or as innocent subjects. I analyse the gendered sexualities of young people as represented in: Grade 10 Life Orientation sexuality education programmes and popular music, as two mediums of sexual socialisation in Grade 10 learners’ lives, and as engaged with by Grade 10 learners and educators. I collected data from two schools in the Eastern Cape that included: (i) sections on sexuality from two Life Orientation manuals used by educators in classrooms: ‘Oxford Successful Life Orientation’ (2011), and ‘Shuters Top Class Life Orientation’ (2011); (ii) videos and lyrics of three songs voted most popular by learners which were ‘Climax’ by Usher, ‘Beez in the Trap’ by Nicki Minaj, and ‘Where Have You Been’ by Rihanna; (iii) observations of seven sexuality education classes; and, (iv) in-depth semistructured interviews conducted with eight learners and two educators. I draw on an integrated theoretical and methodological approach – Foucauldian, feminist poststructural and psychosocial psychoanalytic perspectives – to conceptualise and analyse gendered sexualities in terms of: (i) the dominant gendered discourses found in sexuality education manuals, and music videos and lyrics; (ii) the reflexive and interactive gendered subject positions taken up and/or resisted by learners and educators during classroom lessons and one-on-one interviews; and, (iii) learners’ and educators’ conscious and unconscious investments in particular gendered subject positions during one-on-one interviews. These three sets of analysis produced four major themes. The first theme centres on responsible sexuality; young women are expected to assume more sexual responsility than young men, thus curbing their sexual agency. The second theme outlines three types of pleasure – sexual, romantic and dating and/or relationship pleasure – that accord young men and women active and passive ways of exercising pleasure. The third theme highlights the heteronormative transitioning adolescent subject that constructs young women as reproductive subjects and young men as sexual subjects. The last theme focuses on gendered power relations and raunch culture, and maintains that young men are powerful and likely to commit acts of sexual violence against young women because they are powerless. The central argument developed when viewing all the themes is that dominant gendered discourse, gendered subject positions, and conscious and unconscious investments in these positions challenge the extent to which the gendered meanings that underpin adolescent learners’ sexuality are stable and fixed. The gendered discourses in the Life Orientation sexuality education programmes showed that gender is expressed rigidly, thus privileging masculine over feminine sexuality. However, the gendered discourses in the popular music contested rigid gender binaries and produced fluid and equitable masculine and feminine sexualities. The classroom practices depicted multiple and more equatable gendered sexualities, highlighting just how contested gender is. Finally, educator and learners’ personal biographies illustrated how conflicting masculine and feminine sexualities present a signficant source of emotional conflict for them. It may benefit policymakers and stakeholders to consider informal mediums of sexual socialisation for learners, such as music, when drafting the Life Orientation sexuality education curriculum, whilst also taking into account learners and educators personal lives.
- Full Text:
- Date Issued: 2016
Observational cosmology with imperfect data
- Authors: Bester, Hertzog Landman
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/463 , vital:19961
- Description: We develop a formalism suitable to infer the background geometry of a general spherically symmetric dust universe directly from data on the past lightcone. This direct observational approach makes minimal assumptions about inaccessible parts of the Universe. The non-parametric and Bayesian framework we propose provides a very direct way to test one of the most fundamental underlying assumptions of concordance cosmology viz. the Copernican principle. We present the Copernicus algorithm for this purpose. By applying the algorithm to currently available data, we demonstrate that it is not yet possible to confirm or refute the validity of the Copernican principle within the proposed framework. This is followed by an investigation which aims to determine which future data will best be able to test the Copernican principle. Our results on simulated data suggest that, besides the need to improve the current data, it will be important to identify additional model independent observables for this purpose. The main difficulty with current data is their inability to constrain the value of the cosmological constant. We show how redshift drift data could be used to infer its value with minimal assumptions about the nature of the early Universe. We also discuss some alternative applications of the algorithm.
- Full Text:
- Date Issued: 2016
Participation of Zimbabwean female students in physics: Subject perception and identity formation
- Authors: Gudyanga, Anna
- Date: 2016
- Subjects: Participation -- Women -- Zimbabwe Women -- Education -- Zimbabwe Science -- Study and teaching -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/11542 , vital:26936
- Description: The central focus of this study was to determine the extent to which identity formation influenced Zimbabwean A-level female students’ perceptions of and participation in physics. The themes from the sub-problems included the influence of contextual factors on identity formation in relation to physics as a subject at Advanced Level (A-level), facets of identity formation considered to be of significance by female students in relation to physics, the way in which female students’ perceptions of physics influenced their participation in the subject as well as the factors of identity formation considered as contributing to developing an orientation towards physics by female students. A qualitative approach grounded in an interpretivist paradigm was used. A tri-hybrid theoretical lens comprising of Wenger’s (1998) Social Learning Theory featuring CoP, the Feminist Stand point Theory and Sfard and Prusak’s (2005) notion of ‘telling’ identities or stories, enabled a rich understanding of the influences of identity formation on female students’ perceptions of and participation in physics. The data generating methods used were classroom observation, Draw-A-Scientist Test and semi-structured interviews conducted with nine participants. The data were collated to generate narratives. Key findings: The contextual factors that influenced the identity formation of female students and subsequently their participation in physics at A-level included: Parental and siblings influence; cultural perceptions; impact of the O-level experience; A-level physics teachers’ attitudes; classroom and laboratory experience; male peer influence and other factors such as an understanding of the relevance of physics in daily life. Facets of identity formation considered to be of significance by female students in relation to physics included: being confident, fearless, intelligent, and courageous, liking physics and being determined. These facets motivated them to develop an identity in favour of physics. The female participants studying only mathematics perceived themselves as very intelligent but with a fear of failing physics, lacking confidence and courage. Female students who held negative perceptions towards physics chose to do only mathematics at A-level while those with positive perceptions which influenced the formation of a positive physics identity displayed enthusiasm and commitment to achieve high levels of performance in the subject. Factors of identity formation considered as contributing positively to the development of an orientation towards physics by female students included the importance of v female physics teachers as role models, motivation from O-level science teachers, high self-confidence, high self-esteem, parental support and encouragement, and aspirations towards a physics related career. Gender insensitivity displayed by male teachers, male peer harassment and gender stereotyping are factors in identity formation considered as inhibiting the development of an orientation towards physics by female students. This study provides physics educators, physics planners and the government with detailed information on the role identity formation plays on the participation of Zimbabwean female adolescent students in A-level physics. The findings may be used by heads of schools to sensitise academic staff on the gender dimensions of teaching and learning as well as by counsellors and parents to encourage females to enrol for physics and mathematics as their subjects of choice. This study also contributes to the strengthening of educational research in Zimbabwe, especially research aimed at emancipation of female students in Zimbabwe.
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- Date Issued: 2016