Investigating how the use of visual models can enhance the teaching of common fractions for conceptual understanding to Grade 8 learners
- Authors: Katenda, Aune Kashikuka
- Date: 2019
- Subjects: Fractions -- Study and teaching (Secondary)-- Namibia , Mathematics -- Study and teaching (Secondary)-- Namibia , Information visualization , Visual learning -- Case studies
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/96746 , vital:31314
- Description: The intention of this study was to explore how selected mathematics teachers used visual models to improve the teaching of common fractions for conceptual understanding to Grade 8 learners as a result of an intervention programme. This research study is part of the VIPROmaths project which seeks to research the effective use of visualisation processes in the mathematics classroom in South Africa, Namibia, Zambia, Switzerland and Germany. This study which adopted a case study of teachers in Khomas Region, Namibia, is informed by constructivist learning theory. The study is situated within the interpretive paradigm and a multi-phase mixed method research approach was used. It focussed on analysing the use of visual models when teaching fractions namely: area model, number line model and a set model. The data were collected through survey questionnaires, observation and recall interview. The survey was conducted with the forty three mathematics teachers, from twenty secondary schools in Khomas region. The survey gave an overview of the nature and the use of visual models in schools. Three teachers purposively selected from the survey participated in the intervention program and were observed while teaching and interviewed after their teaching. Data were qualitatively and quantitatively analysed. The findings of this study reveal that visualising fractions is one of the methods that can improve both teaching and learning by providing concrete evidence of otherwise abstract ideas and concepts. The teachers highlighted that models themselves guide learners through to the answer, as compared to working out solutions using symbols only. They further indicated that visual models improve learners’ motivation, enhances understanding of fractions and encourages full participation of learners in the lesson. The study also found that use of visual models encouraged participation and it also boosted learners thinking capability. Teachers in this study preferred to use the area model as they found this model easier and more user-friendly in comparison with the number line and the set models. Teachers did not use the set model because of its complexity. This study concludes that the use of visual models can help enhance the conceptual teaching and understanding of common fractions. It is hoped that the study contributes towards improving the quality teaching and learning of fractions in Namibia. Furthermore, it informs the teacher-training institutions in Namibia to integrate the use of visualisation in their training programmes to promote conceptual understanding of mathematics.
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Investigating the linguistic effectiveness of early reading schemes in isiXhosa: a phonological and orthographical analysis of three isiXhosa Grade 1 graded reader series
- Authors: Katz, Jennifer L
- Date: 2019
- Subjects: Education, Elementary -- South Africa , Literacy -- South Africa , Xhosa language -- Readers , Native language and education -- South Africa
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/92798 , vital:30748
- Description: Literacy in South Africa is in crisis. Inadequate learning and teaching materials, extensive curriculum changes, under-resourced schools and under-qualified teachers are all contributing factors to an alarming situation. Grade 1 African language reading schemes in South Africa are failing to provide young children with the necessary and appropriate practice required to facilitate home language literacy acquisition (NEEDU 2013). A detailed analysis of three isiXhosa Grade 1 graded reader series will show the short-comings of texts translated from English with no cognisance of isiXhosa phonic structures and little appreciation for the agglutinative nature of Nguni languages. Formulating a new, effective approach to the development of African language readers to facilitate reading literacy is urgent and of national importance. The innovative phonics-based methodology, as well as an appropriate instructional level used to develop the Vula Bula Grade 1 isiXhosa readers appears to be a viable blueprint for the development of early readers that can effectively help to ameliorate current deficient literacy levels in African languages. This research thus combines applied linguistics with literacy materials development.
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Inflation hedging with South African common stocks: a JSE sectoral analysis
- Authors: Kawawa, Dennis
- Date: 2019
- Subjects: Johannesburg Stock Exchange , Inflation (Finance) -- South Africa , Hedging (Finance)-- South Africa
- Language: English
- Type: text , Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/71526 , vital:29861
- Description: Inflation risk erodes purchasing power, redistributes wealth from lenders to borrowers and threatens investor’s long-term objectives, which are often specified in real terms; financial market volatility presents an additional risk for investors and portfolio managers concerned with not only real returns but also absolute returns. Understanding key investment risks, of which inflation is one, is crucial for investment managers in order to design effective hedging strategies to preserve wealth over the long run. Empirical tests of the Fisher hypothesis in South Africa have shown that common stocks are a good hedge against inflation. However, empirical evidence from developed countries has also shown that the relationship between common stocks and inflation is heterogeneous across the sectors and industries. This paper analysed the sectoral differences in the hedging ability of South African common stocks to test for this heterogeneity. The paper presents disaggregated sector models to test heterogeneity across the eight sectors of the JSE securities exchange. Understanding which of these sectors offers the best hedge against inflation is important to investors, allowing them to place money where the value will be best preserved during times of higher inflation. The disaggregated sectors tested included the Basic Materials price index, Industrials price index, Consumer Goods price index, Health Care price index, Consumer Services price index, Telecommunications price index, Financials price index, and Technology price index. Johansen Cointegration techniques were employed to empirically test the Fisher hypothesis for the South African market. For the Fisher hypothesis to hold, this paper was required to find evidence of cointegration between the share indices and CPI, as well as a positive slope coefficient for the cointegrating regression. The results of the cointegration test showed that the All Share index and each of disaggregated sector indices were cointegrated with CPI. This implied that a long run relationship exists between common stocks and inflation. Two techniques were used to estimate the cointegrating regressions for each model, a standard long-run cointegrating regression normalizing on the share index and a Vector error correction model (VECM). For all the models both techniques reveal a positive relationship between common stock and CPI with the coefficients for the long run cointegrating regression derived from the various models ranging between 1.41 – 3.62 while the coefficients from the VECM ranged from 1.42 - 4.85. The varying coefficients provide evidence of the heterogeneity of the hedging ability of common stocks. Overall the evidence from the long run cointegration regression suggests that in times of high inflation investors are most compensated for changes in inflation in common stocks relating to the Consumer Services and Health Care sectors, but that in general all sectors of the JSE provide some hedge for inflation. The results suggest that investors are compensated for changes in inflation if they invest in specific industries rather than in the All Share index, thus diversifying portfolios could provide a better hedge for inflation. Although positive coefficients were found the weak exogeneity test revealed only technology Index was caused by changes in CPI. The Paper concluded that in the long run all sectors provided protection against inflation during the period of study, but the evidence only fully supports the Fisher hypothesis for the Technology index, due to the results of the weak exogeneity test that revealed that CPI is weakly exogenous only in the equation of the Technology index.
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L’entre-deux identitaire dans quelques oeuvres d’écrivains francophones “immigrantsˮ, “cas de Dany Laferrière, d’Alain Mabanckou, de Calixthe Beyala et de Lottin Wekapeˮ
- Authors: Kayumba, Viviane Ngoie Banza
- Date: 2019
- Subjects: African literature (French) -- History and criticism , Immigrants in literature , Mabanckou, Alain, 1966-. Black bazaar , Laferrière, Dany. Je suis un écrivain japonais , Beyala, Calixthe. Le Petit prince de Belleville , Wekape, Lottin, 1968-. J’appartiens au monde
- Language: French
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/150929 , vital:39018
- Description: This dissertation examines the theme of hybrid identities in Mabanckou, Laferrière, Beyala and Wekape’s novels : Black Bazar, Le Petit prince de Belleville, Je suis un écrivain japonais and J’appartiens au monde. Hybrid identity raises the issue of identity diversity and contemporary francophone literature is characterised by the emergence of fictional narratives increasingly numerous. This research undertaken is driven by the desire to extend the field of investigation in francophone literature by taking into account a varied corpus of Haitian, Congolese, and Cameroonian literatures. I have opted for writers who settled in a foreign country and have adopted a foreign language that they considered to be part of a foreign literary world; writers who are between two or more cultures which they depict in French. The few existing studies on hybrid identities on these four novels focused more on formal and linguistic analysis and omitted meaningful sociocritic analysis. It is clear that a full study on sociocritic approach on hybrid identity on these four authors remains to be done. The research is demonstrating how different characters created by these four postmodern immigrant French-speaking writers occasionally function similarly in their texts. This gives a clear understanding of the specific behaviour of immigrants characters, vis-à-vis their various situations in the novels, and how these immigrants seek to address the problems they encounter. As this research offers reflections related to the identities and nationalities of immigrants, Laferrière, Mabanckou, Beyala and Wekape’s texts are based on the search for social belonging and a literary membership in this modern world. Therefore, they are analysing their position in a literary field as well as in a social field. In their texts they highlight the Space real or imaginary. In which way and how this Space contribute to the evolution of francophone literature? To what extent does francophone literature takes into account this representation of the Space? These questions lead to a reflection on the position occupied by these authors in the francophone field and the source of their literary inspirations. My interest in these authors is motivated by the fact that, by living and writing in a country which is not their place of birth, they each reveal different aspects of hybrid identity. Each of them, has his or her personal and original way of tackling the problem of mixed identity. They present their characters in different situations and different contexts, showing that each has been in contact with several cultures which they have assimilated and each lived in his or her own way a particular story. My study’s focus is to understand the problems of contact of cultures and their consequences, and to explore how through the characters of the novel, immigrant French speaking writers understood their acculturation as themselves have experienced an identity crisis, resulting from the confrontation of the culture of their new homeland and the culture of their country of origin. For this reason, Bourdieu’s approach “la sociocritique” will help me to found out the origin of the author’s obsession with the question of hybrid identity. I have chosen these four immigrant speaking writers to explore the strategies implemented by the novels’ narrators to construct their identities and to find out how the narrators express the intentions of the authors. In their texts, Mabanckou, Beyala, Laferrière and Wekape have used various strategies to express the quest for identity which gives clear indications of the authors’ creativity such as humour, parody, or solemnity and gravity - and the narrative voices reveal distinctive attitudes in relation to hybrid identity. At this level, other approaches will also be called for, such as the work of Westphal, Doubrovsky, Genette, Colona, etc. Through my investigation, these works present similarities and dissimilarities. Each author tackled the questions of hybrid identities according to his own experience. From there, a different commitment emerges, depending on the degree of inquiry into questions about immigration. These authors all evoke the social precariousness of their characters or the immigrant and privilege an urban framework. The examination of these works allowed me to identify their place in Francophonie literature and to discover the importance of their texts. The four novels relate to the search for identity, an aesthetic way and a search for freedom. They possess aesthetic qualities, they have a high degree of coherence. Their romantic choice shows their creativity and their strategies engender a hybrid writing that stems from their position between several languages and place these novels within the world literature.
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Exploration of challenges in bringing traditional medicine into SA’s healthcare system, using medicinal plants for treatment of waterborne diarrhoeal diseases as a case study
- Authors: Keche, Priscilla
- Date: 2019
- Subjects: Traditional medicine -- South Africa , Waterborne infection -- South Africa , Diarrhea -- South Africa , Healers -- South Africa , Medical care -- Quality control , Medicinal plants -- South Africa , Diarrhea in children -- South Africa , World Health Organization
- Language: English
- Type: thesis , text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/118035 , vital:34588
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Biotechnology Innovation Centre (RUBIC), 2019.
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The development of a larval feeding regimen for dusky kob, Argyrosomus japonicus, with a specific focus on the effect of weaning period on larval development and survival
- Authors: Keet, Thomas
- Date: 2019
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/96897 , vital:31344
- Description: One of the biggest limiting factors in marine finfish aquaculture is the low survival rate of early-stage larvae. Most mortalities can be ascribed to the poor nutritional value of live feeds, sibling cannibalism, and various stressors that result in swim bladder hyperinflation and/or starvation during the larval stage. Research results vary on the best timing for the introduction of artificial feed for good survival and growth rate in dusky kob larvae. The main objective of this experiment was to improve survival and growth rate. The experiment focused on a new feeding regime that sought to wean larvae onto an artificial diet earlier than the current Argyrosomus japonicus standard (weaning commenced at 16 days after hatch (DAH) versus 20 days after hatch), based on findings and recommendations made by Musson & Kaiser (2014). Three trials were conducted, each with five replicates of the two treatments, namely the new feeding regime and the standard feeding regime in a fully randomised design. Samples from each tank were collected every two days for the duration of the trial. Morphometric measurements (standard length; body depth; eye diameter) obtained from these sample larvae were used to compare growth rates between treatments. The ratio of BD:SL was used to assess larval condition throughout each trial. Tank survival rates were calculated on the last day of each trial.The study indicated that in mean water temperatures ranging from 24.3 – 25.2 °C, dusky kob larvae can be weaned onto an artificial pellet diet from 16 - 21 DAH without any negative effects on growth, condition and survival. Results from the highest mean temperatures of Trial 2 show a better mean condition in the treatment group during the weaning period (p < 0.05). In Trial 3, with its lower mean water temperatures of 23.2 °C, larvae in both treatments showed stunted absolute growth rates of all biometrics when compared to results from the higher mean temperatures of Trials 1 and 2. During the first 6 days of Trial 3 larvae were in relatively poor condition, BD:SL ≤ 0.30. During this same period in Trials 1 and 2, mean BD:SL ≥ 0.31, suggesting that a BD:SL ratio of ≤ 0.30 in non-weaned dusky kob larvae is an indicator of a degree of starvation. A future study on the morphology and histology of the larval gastrointestinal tract, specifically the liver and intestines, and how this early weaning regime affects their ontogeny under differing temperature conditions this needed to investigate the validity of these initial data on dusky kob larvae condition.
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The development of a larval feeding regimen for dusky kob, Argyrosomus japonicus, with a specific focus on the effect of weaning period on larval development and survival
- Authors: Keet, Thomas
- Date: 2019
- Subjects: Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Larvae , Argyrosomus -- Larvae , Argyrosomus japonicus -- Larvae -- Nutrition , Argyrosomus -- Larvae -- Nutrition
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/146577 , vital:38538
- Description: One of the biggest limiting factors in marine finfish aquaculture is the low survival rate of early-stage larvae. Most mortalities can be ascribed to the poor nutritional value of live feeds, sibling cannibalism, and various stressors that result in swim bladder hyperinflation and/or starvation during the larval stage. Research results vary on the best timing for the introduction of artificial feed for good survival and growth rate in dusky kob larvae. The main objective of this experiment was to improve survival and growth rate. The experiment focused on a new feeding regime that sought to wean larvae onto an artificial diet earlier than the current Argyrosomus japonicus standard (weaning commenced at 16 days after hatch (DAH) versus 20 days after hatch), based on findings and recommendations made by Musson & Kaiser (2014). Three trials were conducted, each with five replicates of the two treatments, namely the new feeding regime and the standard feeding regime in a fully randomised design. Samples from each tank were collected every two days for the duration of the trial. Morphometric measurements (standard length; body depth; eye diameter) obtained from these sample larvae were used to compare growth rates between treatments. The ratio of BD:SL was used to assess larval condition throughout each trial. Tank survival rates were calculated on the last day of each trial.The study indicated that in mean water temperatures ranging from 24.3 – 25.2 °C, dusky kob larvae can be weaned onto an artificial pellet diet from 16 - 21 DAH without any negative effects on growth, condition and survival. Results from the highest mean temperatures of Trial 2 show a better mean condition in the treatment group during the weaning period (p < 0.05). In Trial 3, with its lower mean water temperatures of 23.2 °C, larvae in both treatments showed stunted absolute growth rates of all biometrics when compared to results from the higher mean temperatures of Trials 1 and 2. During the first 6 days of Trial 3 larvae were in relatively poor condition, BD:SL ≤ 0.30. During this same period in Trials 1 and 2, mean BD:SL ≥ 0.31, suggesting that a BD:SL ratio of ≤ 0.30 in non-weaned dusky kob larvae is an indicator of a degree of starvation. A future study on the morphology and histology of the larval gastrointestinal tract, specifically the liver and intestines, and how this early weaning regime affects their ontogeny under differing temperature conditions this needed to investigate the validity of these initial data on dusky kob larvae condition.
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CubiCal: a fast radio interferometric calibration suite exploiting complex optimisation
- Authors: Kenyon, Jonathan
- Date: 2019
- Subjects: Interferometry , Radio astronomy , Python (Computer program language) , Square Kilometre Array (Project)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/92341 , vital:30711
- Description: The advent of the Square Kilometre Array and its precursors marks the start of an exciting era for radio interferometry. However, with new instruments producing unprecedented quantities of data, many existing calibration algorithms and implementations will be hard-pressed to keep up. Fortunately, it has recently been shown that the radio interferometric calibration problem can be expressed concisely using the ideas of complex optimisation. The resulting framework exposes properties of the calibration problem which can be exploited to accelerate traditional non-linear least squares algorithms. We extend the existing work on the topic by considering the more general problem of calibrating a Jones chain: the product of several unknown gain terms. We also derive specialised solvers for performing phase-only, delay and pointing error calibration. In doing so, we devise a method for determining update rules for arbitrary, real-valued parametrisations of a complex gain. The solvers are implemented in an optimised Python package called CubiCal. CubiCal makes use of Cython to generate fast C and C++ routines for performing computationally demanding tasks whilst leveraging multiprocessing and shared memory to take advantage of modern, parallel hardware. The package is fully compatible with the measurement set, the most common format for interferometer data, and is well integrated with Montblanc - a third party package which implements optimised model visibility prediction. CubiCal's calibration routines are applied successfully to both simulated and real data for the field surrounding source 3C147. These tests include direction-independent and direction dependent calibration, as well as tests of the specialised solvers. Finally, we conduct extensive performance benchmarks and verify that CubiCal convincingly outperforms its most comparable competitor.
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Tracking the decline of the world’s largest seabream against policy adjustments
- Authors: Kerwath, Sven E , Parker, Denham , Winker, A Henning , Potts, Warren M , Mann, Bruce , Wilke, Christopher , Attwood, Colin G
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/131433 , vital:36571 , https://doi.org/10.3354/meps12853
- Description: For most rare marine species, abundance trends are poorly estimated. This uncertainty often translates into disagreement on management regulations, impeding conservation efforts when they are most urgently required. The world’s largest sea bream, the red steenbras Petrus rupestris, has undergone a substantial and widely acknowledged decline during the 20th century. Standardised probability of encounter over the last 3 decades was used to track red steenbras abundance trajectories in 2 regions, which together represent the species’ distribution. The results predicted a reduction in abundance of 44% in the East region and 96% in the South-West region, from what was already considered to be a collapsed population at the start of the time series. The species is now largely confined to areas in the centre of its historical abundance. Content analysis of a recreational angling magazine revealed a concurrent 50% decrease in reported size between 1984 and 2012. Shore-based observer data (2009-2010) indicate that the impact of recreational fishers on this species far exceeded that of commercial fishers at the time. Regulations in the form of progressively more stringent catch and effort restrictions appear to have been largely ineffective, too lenient, implemented too late or were unsuitable to control fishing mortality for this species. This study highlights 2 fundamental challenges in management of rare marine fish species: (1) providing decision makers with a credible measure of abundance for species whose rarity limits data availability and (2) implementing effective policy changes before the specific measures become ineffective and obsolete.
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Labour market perceptions of students at a Technical and Vocational Education and Training (TVET) college in Grahamstown, South Africa
- Authors: Khambule, Nelisa
- Date: 2019
- Subjects: Eastcape Midlands College (Makhanda, South Africa) -- Students -- Attitudes , College students -- South Africa -- Makhanda -- Attitudes , College graduates -- Employment -- South Africa , Labor market -- South Africa , Employability -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSocSc
- Identifier: http://hdl.handle.net/10962/96515 , vital:31289
- Description: In the context of South Africa, the supply of intermediate to high-level skills is central to economic growth and development. The post-school education and training sector is a critical source of these skills. Technical and Vocational Education and Training (TVET) colleges are expected to provide the intermediate to high-level skills that are required in a fast-changing global and national economy. In addition to fulfilling the goal of meeting the skills needs of the country, TVET colleges are expected to expand access to education and training opportunities and create pathways that will ensure smooth transitions for learners from college to employment. Using the third-generation labour market segmentation approach to the study of labour markets, this study sought to investigate the various socio-political factors that influence TVET college students’ perceptions about employment opportunities in the labour market with a NCV qualification. Using a qualitative methodology, this research investigated whether TVET students at Eastcape Midlands College felt adequately prepared for the labour market with their prospective post-secondary school qualification. The findings varied, with some students being of the view that the theoretical component of their programme of study could be improved to better prepare them for the labour market, and others, being of the view that the practical component could be improved. At a general level, the findings showed that the students did not have perfect knowledge of the availability of employment opportunities for their prospective qualifications.
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The development of high-throughput assays to screen for potential anticancer and antimalarial compounds that target ADP-ribosylation factor 6 and its signalling machineries
- Authors: Khan, Farrah Dilshaad
- Date: 2019
- Subjects: ADP-ribosylation , Proteins -- Metabolism , Nucleoproteins , Malaria -- Chemotherapy , Cancer -- Chemotherapy
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/92952 , vital:30810
- Description: ADP-ribosylation factors (Arfs) are small GTP-binding proteins that cycle between active GTP-bound forms and inactive GDP-bound forms. GDP/GTP cycling is regulated by large families of guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). ArfGEFs activate Arfs by mediating the exchange of GDP for GTP, while ArfGAPs terminate Arf function by stimulating the hydrolysis of the terminal phosphate group of GTP. Arf6 is a major regulator of endocytic trafficking and reorganization of the actin cytoskeleton in eukaryotic organisms. Owing to its participation in wide range of fundamentally distinct cellular processes, Arf6 may be a drug target for cancer and malaria amongst other diseases. As with cancer cells, rapid growth and viability of eukaryotic pathogens likely places a heavy burden on their endocytic pathways and a critical reliance on Arf6 activity. A putative malarial homolog of Arf6 (PfArf6) localises to numerous puncta along the periphery of the parasite in the mature trophozoite life stage of the parasite (T. Swart, MSc dissertation). Owing to highly inefficient parasite transfection procedures and a relative shortage of well described and validated parasite organelle markers, the possible functions of PfArf6 were explored using HeLa cells as a surrogate model for parasites by fluorescence microscopy of cells transfected with GFP-tagged PfArf6. Partial co-localisation was observed with the mammalian markers HsArf6 and LC3, which suggested possible roles in Arf6-dependent endocytosis and autophagy, respectively. While these possible roles are currently under investigation in parasites, an overall long-term goal which was initiated in this study was to determine whether PfArf6 is a valid drug target. To chemically validate PfArf6 as a drug target, a potent inhibitor needs to be identified. This requires the development of assays that may be employed for high-throughput screening of compound libraries. To support this goal, a novel plate-based assay was developed using human Arf6. The assay relies on the selective binding of an Arf effector protein domain (GGA3) fused to glutathione-S-transferase (GST), to His-tagged Arf6 immobilised on a nickel-coated plate. The assay format was developed and could robustly distinguish HsArf6-GDP (inactive) from HsArf6-GTP (active). Furthermore, it could be employed to detect the deactivation of Arf6 by ArfGAP1-stimualted GTP hydrolysis, but not Arf6 activation by ARNO-stimulated GDP/GTP exchange (ARNO is an ArfGEF). The ArfGAP1 deactivation assay was chemically validated using a known ArfGAP inhibitor, QS11. An improved assay was developed that employs JIP4 as an Arf6-specific binding partner instead of GGA3. In addition to superior performance, the alternative assay format could potentially be exploited for cancer drug discovery, since Arf6-JIP4 interaction has been implicated in cancer cell invasion and metastasis. Both assays may be employed to explore alternative ArfGEFs and ArfGAPs that act on Arf6 and contribute to the advancement of cancer. In parallel experiments, where development of PfArf6 assays was the focus, several issues arose. Firstly, we could not prepare GDP- and GTP-bound forms of PfArf6 since EDTA-mediated nucleotide exchange appeared to irreversibly destabilise the protein. However, PfArf6 activation (i.e. the preparation of PfArf6-GTP) was possible when mediated by ARNO and assessed by tryptophan fluorescence kinetic assays, suggesting that PfArf6 may be expressed in GDP-bound form in E. coli. As with human Arf6, ARNO-mediated GDP/GTP exchange on PfArf6 was not detectable in the immobilised PfArf6-GGA interaction GST assay format. However, a more sensitive assay was developed which relies on the use of nickel-horseradish peroxidase to detect the binding of His-tagged PfArf6 to JIP4-GST immobilised on glutathione plates and could detect ARNO-mediated PfArf6 activation. Since we could not prepare PfArf6-GTP (that did not rely on the presence of the ArfGEF, ARNO), malarial ArfGAP deactivation studies were conducted using PfArf1 instead of PfArf6 in the GGA-GST interaction assay. Both PfArfGAP1and PfArfGAP2 stimulated GTP hydrolysis by PfArf1, but only the former was inhibited by the standard human ArfGAP inhibitor, QS11. The development of these simple, cost-effective assays can be used in the high-throughput screening of novel anticancer and antimalarial compounds that target Arf signalling machineries. In theory, the assay could be extended as a tool to identify novel inhibitors of the multitude of Arfs, ArfGEFs and ArfGAPs originating from any organism and hence has broad clinical significance.
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Un-functionalized gold nanoparticles as a simple colorimetric probe for sensitive and selective detection of dopamine
- Authors: Khanyile, Nokuthula , Krause, Rui W M , Vilakazi, Sibulelo , Torto, Nelson
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/195048 , vital:45522 , xlink:href="http://dx.doi.org/10.17159/0379-4350/2019/v72a27"
- Description: A dopamine (DA) colorimetric probe based on the growth and aggregation of un-functionalized gold nanoparticles (AuNPs) is reported. Upon addition of AuNPs to dopamine at various concentrations, the shape, size and colour change of the nanoparticles results in spectral shifts to higher wavelengths and hence colour change is the mode of detection. The colour change can be easily observed by the naked eye from as low as 5.0 nM DA, even under sub-optimal conditions. Under optimal pH conditions the calculated limit of detection was 2.5 nM (3σ). The probe was successfully applied to whole blood sample and showed good selectivity and sensitivity towards DA. The simple, sensitive and selective probe could be an excellent alternative for on-site and immediate detection of DA without the use of instrumentation and would thus be useful for rapid diagnostic applications.
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An evaluation of the current extent and potential spread of Black Bass invasions in South Africa
- Authors: Khosa, Dumisani , Marr, Sean M , Wasserman, Ryan J , Zengeya, Tsungai A , Weyl, Olaf L F
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103867 , vital:32317 , https://doi.org/10.1007/s10530-019-01930-0
- Description: Black Bass, a collective name for members of the centrarchid genus Micropterus, are native to North America, but have been introduced globally to enhance recreational angling. This study assessed the distribution of Micropterus salmoides, M. dolomieu and M. punctulatus in South Africa using both formal (survey-based) and informal (tournament data and social media) information sources. Analysis of the distribution data showed habitat bias between the data sources. Survey data from formal information sources were dominated by locality records in riverine environments while those derived from informal information sources focused more on lacustrine habitats. Presence data were used to develop niche models to identify suitable areas for their establishment. The predicted distribution range of M. salmoides revealed a broad suitability over most of South Africa, however, the Cape Fold Ecoregion and all coastal regions were most suitable for the establishment for both M. dolomieu and M. punctulatus. Flow accumulation and precipitation of coldest quarter were the most important environmental variables associated with the presence of all Black Bass species in South Africa. In addition, anthropogenic disturbance such as agricultural activities were associated with the presence of both Smallmouth Bass and Spotted Bass. An extensive area-based invasion debt was observed for all Micropterus spp. The potential for further spread of Black Bass in South Africa is of ecological concern because of their impact on native biota.
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Exploring visual literacy development through films in senior phase English first additional language
- Authors: Khosa, Michael
- Date: 2019
- Subjects: Visual litearcy , Motion pictures in education -- South Africa , English language -- Study and teaching (Secondary) -- South Africa
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/92672 , vital:30727
- Description: Despite learners’ general poor performance in English First Additional Language (EFAL), research indicates their wide exposure to film viewing which is untapped when teaching visual literacy in EFAL classes (Mnyanda, 2017). This study identified a golden opportunity of introducing film teaching in the senior phase in order to equip learners with the knowledge, skills and values for self-fulfilment, and meaningful participation in society as citizens of a free country. Two teachers’ meaning-making and pedagogical practices of teaching film were explored in a rural Eastern Cape District, South Africa. Qualitative research methodology was used to collect data from lesson observations using a video camera and post-lesson interviews with each teacher. I drew on Vygotsky’s (1978) socio-cultural theory of learning which privileges learners’ social interaction, More Knowledgeable Other and scaffolding in the learning process. Critical Discourse Analysis offered insights on challenging stereotypes available in designing and redesigning texts. It emerged that lack of resources in previously disadvantaged schools and teachers’ missed opportunities to teach film in context were major causes of underperformance. Findings also interestingly revealed that learners could perform better when taught through the film. This study recommends that schools should teach film since it is can improve learners’ results.
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Vowel harmony in isiXhosa: an OT and acoustic study of [ATR]
- Authors: Kilian, Kelly
- Date: 2019
- Subjects: Grammar, Comparative and general -- Vowel harmony , Xhosa language -- Vowels , Xhosa language -- Phonetics
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/67678 , vital:29128
- Description: The vowel harmony system in isiXhosa is centred on a process of vowel raising. All mid-vowels preceding a high vowel take on the feature advanced tongue root (ATR) (e.g. thɛnga ‘buy’ → thengisa ‘sell’; bɔna 'see' → bonisa 'cause to see') (Harris 1987). The process of mid-vowel assimilation for the feature [+ATR] is consistent in all instances in which the mid-vowel occurs preceding a high vowel trigger, unless harmony is blocked by the low opaque vowel [a]. This is the analysis presented in Jokweni & Thipa (1996) the only previous literature to address the vowel harmony process of isiXhosa in detail. As an alternative approach to the rule-based phonology applied in the analysis presented by Jokweni & Thipa (1996), I propose the introduction of Optimality theory (OT) (Prince & Smolensky 1993, Bakovic 2000, and Pulleyblank 2002). I will present a map of the harmony system of isiXhosa using OT, while also presenting acoustic data to supplement the selected examples provided in Jokweni & Thipa (1996). This acoustic investigation will determine whether the harmonic feature is ATR, and how this feature patterns among vowels in different phonological contexts. In this paper vowel harmony is achieved through the implication of numerous rules, and with very specific directional and prosodic limitations on the spread of [+ATR]. Using generalisations based on my own collected data as well as those reported in previous literature, I have developed a constraint ranking to account for the harmony process in isiXhosa. By adapting the No-disagreement approach to harmony (Pulleyblank 2002), the final constraint ranking has the capacity to derive the optimal phonetic candidate for every harmony case. A selection of spread constraints is used to account for the raising as well as blocking processes, by driving either regressive or progressive spreading. Within the original No-disagreement approach a spread constraint would recognised only one feature in its prohibition of disagreeing segments. However, in the adapted approach the spread constraint driving [+ATR] assimilation is combined with a feature of correspondence (Krämer 2001) which considers the height as well as the ATR value of the sequential segments. The constraint is therefore adapted to consider more than one feature and is not activated unless the sequential segments agree for this particular feature. The regressive spread constraint is therefore only activated when the consecutive segments have an agreeing height value. The introduction of this adaptation was necessary to provide a more nuanced OT approach with the capacity to effectively characterise the idiosyncrasies observed in this harmony pattern. The harmony constraints are therefore no longer contradict one another by simultaneously driving harmony in opposite directions. Furthermore, the direct acoustic analysis is completed by means of the PRAAT software, to answer the salient question of the definitive harmonic feature. To provide a multiplicity of empirical evidence I have recorded utterances containing a number of vowel combinations. Each combination positions the alternating mid-vowels in a particular phonological context from which instances of ATR alternations have been extracted and phonetically analysed. Using the generalisations reported in Jokweni & Thipa (1996) as a starting point, the acoustic signal of each mid-vowel within a set phonological context is annotated for a predicted ATR value. Hence, if a mid-vowel occurs preceding a high vowel it is annotated as [+ATR] etc. The data sets representing each of the mid-variants found in a specific phonological context are then plotted into vowel charts and compared by means of statistical analysis (Baayen 2008, Bluman 2000). The results are then used to determine whether any significant phonetic alternation is occurring, and what the acoustic distinction between [+ATR] & [-ATR] variants is essentially comprised of. The final acoustic results indicate a significant difference between the mid-vowel ATR variants extracted from specific phonological contexts. Hence, due to co-articulatory effects or some other phonological influence the realisation of [+/-ATR] variants exist along a spectrum, and are therefore not phonetically consistent, but indicate a different acoustic make-up across the various groups.
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Identification of Novel Potential Inhibitors of Pteridine Reductase 1 in Trypanosoma brucei via Computational Structure-Based Approaches and in Vitro Inhibition Assays
- Authors: Kimuda, Magambo Phillip , Laming, Dustin , Hoppe, Heinrich C , Tastan Bishop, Özlem
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124675 , vital:35647 , https://doi:10.3390/molecules24010142
- Description: Pteridine reductase 1 (PTR1) is a trypanosomatid multifunctional enzyme that provides a mechanism for escape of dihydrofolate reductase (DHFR) inhibition. This is because PTR1 can reduce pterins and folates. Trypanosomes require folates and pterins for survival and are unable to synthesize them de novo. Currently there are no anti-folate based Human African Trypanosomiasis (HAT) chemotherapeutics in use. Thus, successful dual inhibition of Trypanosoma brucei dihydrofolate reductase (TbDHFR) and Trypanosoma brucei pteridine reductase 1 (TbPTR1) has implications in the exploitation of anti-folates. We carried out molecular docking of a ligand library of 5742 compounds against TbPTR1 and identified 18 compounds showing promising binding modes. The protein-ligand complexes were subjected to molecular dynamics to characterize their molecular interactions and energetics, followed by in vitro testing. In this study, we identified five compounds which showed low micromolar Trypanosome growth inhibition in in vitro experiments that might be acting by inhibition of TbPTR1. Compounds RUBi004, RUBi007, RUBi014, and RUBi018 displayed moderate to strong antagonism (mutual reduction in potency) when used in combination with the known TbDHFR inhibitor, WR99210. This gave an indication that the compounds might inhibit both TbPTR1 and TbDHFR. RUBi016 showed an additive effect in the isobologram assay. Overall, our results provide a basis for scaffold optimization for further studies in the development of HAT anti-folates.
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Computational analysis of missense mutations from the human Macrophage Migration Inhibitory Factor (MIF) protein by Molecular Dynamics Simulations and Dynamic Residue Network Analysis:
- Authors: Kimuda, Phillip M , Brown, David K , Amamuddy, Olivier S , Ross, Caroline J , Matovu, Enock , Tastan Bishop, Özlem
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/163238 , vital:41021 , https://doi.org/10.21955/aasopenres.1115054.1
- Description: Missense mutations are changes in the DNA that result in a change in the amino acid sequence. Depending on their location within the protein they can have a negative impact on how the protein functions. This is especially important for proteins involved in the body’s response to infection and diseases. Macrophage migration inhibitory factor (MIF) is one such protein that functions to recruit white blood cells to sites of inflammation.
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The extent of urban Green Collar employment, its contribution to poverty alleviation and potential for growth in the Eastern Cape, South Africa
- Authors: King, Andrew
- Date: 2019
- Subjects: Economic development -- Environmental aspects -- South Africa -- Eastern Cape , Poverty prevention -- South Africa -- Eastern Cape , Job creation -- South Africa -- Eastern Cape , Urban ecology (Sociology) -- South Africa -- Eastern Cape , Urban poor -- Employment -- South Africa -- Eastern Cape , Clean energy industries -- Employment -- South Africa -- Eastern Cape , Renewable energy sources -- Government policy -- South Africa -- Eastern Cape , Land use, Urban -- South Africa -- Eastern Cape , Open spaces -- Environmental aspects -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/115191 , vital:34095
- Description: The aim of this research was to investigate the job provisioning benefits of urban green space (GS), the ability of these jobs to alleviate poverty amongst poor urban households, as well as the potential to increase the number of Green Collar (GC) jobs. According to Lal et al. (2010), Roy et al. (2012) and others, environmental employment or GC jobs, represent the very synergy between social, economic and environmental resilience and sustainability, and have the ability to provide an additional range of goods and services. Data was collected from 12 towns and cities in the Eastern Cape of South Africa, all varying in population, town size and geographic location. Structured employer, employee and resident interviews were used to collect data, which pertained to a number of employment characteristics and employee living conditions. Throughout the sample, 19 different types of jobs were identified, and a total of 17 429 GC employees were counted, sharing a total of approximately R503 million in annual wages. Some GC employees were found to still be in a position of poverty despite employment, while others enjoyed a higher standard of living as a result, although this was largely dependent on the extent of wages and other household and employment attributes. Using lessons learnt from previous chapters, a number of data sources and a creative approach, the potential for growth and improvement in the urban GC sector was discussed, and the way forward involves private, public, informal and civil sector participation and innovation; which will not only enhance environmental and social ecosystem services, but also provide meaningful employment opportunities to the otherwise impoverished. Urban GC jobs should be widely viewed as a useful tool in achieving social, environmental and economic prosperity in urban landscapes (Bowen and Kuralbayeva, 2015).
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Reconfiguring the Omweso board game: performing narratives of Buganda material culture
- Authors: Kirumira, Rose Namubiru
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145996 , vital:38487 , https://0-doi.org.wam.seals.ac.za/10.1162/afar_a_00460
- Description: My artwork titled Nakulabye, which is 4 meters long and weighs 440 pounds, is an intimidating sculptural replica of the Omweso game board (Fig. 1). The wooden sculpture, twenty times larger than an average Omweso game board, includes four cane stools to sit on during play. Its composition is derived from a human face, and it has thirty-two pits (8 × 4) in the configuration of a mancala board. This sculpture was inspired by my engagement with a group of men that I visited in July 2016 in Nakulabye, a town in an urban area of Kampala City, Uganda. At the Nakulabye Omweso Club, a shop veranda in Nakulabye Town, these men play Omweso and chat against the backdrop of a small television that mostly screens British Premiere Leagues. Observing their exchanges, which seem to be informed by moves on the Omweso board and reveal strong, clearly gendered power dynamics, I became curious about the performative place of Omweso as a cultural artifact of the Baganda people.
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Foreground simulations for observations of the global 21-cm signal
- Authors: Klutse, Diana
- Date: 2019
- Subjects: Cosmic background radiation , Astronomy -- Observations , Electromagnetic waves , Radiation, Background
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76398 , vital:30557
- Description: The sky-averaged (global) spectrum of the redshifted 21-cm line promises to be a direct probe of the Dark Ages, the period before the first luminous sources formed and the Epoch of Reionization during which these sources produced enough ionizing photons to ionize the neutral intergalactic medium. However, observations of this signal are contaminated by both astrophysical foregrounds which are orders of magnitude brighter than the cosmological signal and by non-astrophysical and non-ideal instrumental effects. It is therefore crucial to understand all these data components and their impacts on the cosmological signal, for successful signal extraction. In this view, we investigated the impact that small scale spatial structures of diffuse Galactic foreground has on the foreground spectrum as observed by a global 21-cm observation. We simulated two different sets of observations using a realistic dipole beam model of two synchotron foreground templates that differ from each other in the small scale structure: the original 408 MHz all-sky map by Haslam et al. (1982) and a version where the calibration was improved to remove artifcats and point sources (Remazeilles et al., 2015). We generated simulated foreground spectra and modeled them using a polynomial expansion in frequency. We found that the different foreground templates have a modest impact on the simulated spectra, generate differences up to 2% in the root mean square of residual spectra after the log-polynomial best fit was subtracted out.
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