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Foundation phase teachers’ understanding and implementation of differentiated pedagogical practices in teaching reading

  • Authors: Muroa, Johanna Makgati
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/463713 , vital:76434
  • Description: Pre-1994, teacher education in South Africa was separated into mainstream and special education classes. Special education classes accommodated learners who were not coping with grade-level work. In 2001, Education White Paper Six advocated for inclusive education. This policy promotes differentiated pedagogical practices to accommodate learners’ needs and minimize barriers to learning. However, research has shown that teachers do not have the required content and pedagogical knowledge to teach according to diverse learners’ needs. One of the reasons given is that the teacher education system does not prepare teachers adequately to teach in classrooms with diverse learners. This qualitative case study is underpinned by an interpretivist orientation as it seeks to ascertain how teachers understand and implement differentiated pedagogical tools in their practice. The research asks the question: How do Foundation Phase teachers understand and implement differentiated pedagogical tools? Seventy-six teachers enrolled for in-service Bachelor of Education (Foundation Phase) completed a questionnaire and three Foundation Phase teachers were observed and interviewed. Data gathered was analyzed using the Theory of Practice Architectures. The study found that the teachers recognized the importance of accommodating the different learners’ learning needs, however, they struggled to implement differentiated pedagogical practices in the classroom. , Thesis (MEd) -- Faculty of Education, Primary and Early Childhood Education, 2024
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  • Date Issued: 2024-10-11

Gold mineralization at the Blue Rock Deposit, Gadzema Greenstone Belt: Implications on genesis and exploration for orogenic gold mineralization within Archaean Greenstone Belts of Zimbabwe

  • Authors: Mavuwa, Tavashavira
  • Date: 2024-10-11
  • Subjects: Felsite , Quartz porphyry , Orogenic gold deposit , Shear zones (Geology) , Prospecting
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/464944 , vital:76559
  • Description: The Blue Rock gold deposit was re-discovered by African Consolidated Resources (ACR) in 2007, over a defunct historical gold mine at Blue Rock, during a regional geochemical soil sampling program, within the Gadzema Greenstone Belt (GGB), in Central Zimbabwe. Most significant orogenic gold deposits within this belt occur as BIF- and quartz vein hosted orebodies. But unlike them, gold mineralization at Blue Rock is associated with felsite and quartz porphyry rocks. The GGB is a northern extension of the Midlands Greenstone Belt (MGB), where the common occurrence of mineralized felsites, in close association with major gold reefs within numerous gold mines is well documented. But no significant effort was directed towards their understanding or exploration in the past. They were never considered viable exploration targets for significant economic gold deposits, until recently. More attention was instead focused on high-grade BIF and quartz vein hosted gold, that dominate most orebodies exploited by numerous mines within the belt. At Blue Rock, ACR defined a significant JORC compliant felsite-hosted gold resource of close to a million ounces, which represents a brand new attractive open-pit mining opportunity. But the successful exploration for such type of mineralization, whose footprint is so different from the common ones previously mined within the GGB, no doubt, calls for a good understanding of this type of mineralization. Which makes felsite-hosted gold mineralization a prime candidate for research, based on a deposit whose discovery and development, I was fortunate to be part of during the past few years. In this contribution, the genesis, localization and economic significance of felsite-hosted gold mineralization is investigated, using the gold deposit at Blue Rock as a case study. The deposit could be understood best through the Mineral Systems Approach, used in this study to interrogate alternative ideas about its genesis using published information and deposit-scale exploratory data. Results from the synthesis of published information on the evolution of Archaean Greenstone Belts and genesis of their host orogenic gold deposits, are consistent with models that view orogenic terrains as having formed through horizontal accretion in modern-day like subduction-accretion systems, at continental margins, where orogenic gold deposition occurred via processes that could be explained quite simply, through a universal orogenic gold mineral systems model. According to this model, orogenic gold deposits are believed to have formed from near neutral fluids containing dissolved gold, generated directly from the devolatilization of a subducted oceanic slab together with its overlying gold-bearing sulphide-rich sedimentary package, or indirectly through fluid released from a mantle lithosphere that was originally metasomatized and fertilized during an earlier subduction event. The fluid migrated up-dip from the mantle to crustal levels, through advection or seismic pumping along lithosphere- to crustal-scale fault zones, to form orogenic gold deposits within lower order structures. If these models are all accurate, then the GGB formed through subduction-related east-directed horizontal accretion at the continental margins of the Sebakwe Proto-Craton (SPC), and the genesis of felsite-hosted gold mineralization at Blue Rock could be explained eloquently through a universal orogenic gold model, in which mantle derived auriferous fluids were localised within lower order structures associated with felsites during the late stages of terrain accretion. Evidence from surface mapping and 3D modelling of exploratory drilling data, conducted during this research, strongly support the argument that the felsite hosted gold mineralization at Blue Rock, is neither unique nor accidental. It is just but, a simple product of the conjunction of favourable geological factors, no different to those that birthed typical GGB orogenic gold mineralization hosted within sheared sulphidic BIFs and quartz vein reefs. They all share the same geodynamic setting, fertility, preservation and regional architectural factors reminiscent of accretionary orogenic settings, albeit with differences in local architecture, variably controlled by geochemical and rheological properties of the different local host rocks. At deposit scale, the felsites occur as small dykes and sills emplaced along pre-existing structural zones of weakness. Gold mineralization is structurally controlled and associated mostly with brittle-ductile shears. During deformation, rheological contrast played a significant role in the selective failure of the more competent felsite rocks, resulting in the creation of permeability channels that allowed fluid migration. The more brittle and competent felsites acted as rigid bodies, that localised strain along their contacts with the surrounding less competent ductile mafic schists which acted as a relatively less permeable fluid cap rock. The irregular felsite contact zones with surrounding mafic schist caused a significant variation in the orientation of local principal maximum stress relative to the internally imposed regional stress, causing anomalously low minimum stress zones at deposit scale. Gold deposition occurred within low minimum stress structural traps dominated by sheared felsite contacts and their fractured interiors as well as triple junctions formed by complex structural geometries created by multiple felsite intrusions. The felsite hosted gold at Blue Rock can therefore be recognized as an orogenic gold mineral system archetype, for which an occurrence model is proposed. Understanding this type of mineralization is key for developing a robust exploration strategy - one that could be applied in a predictive capacity in exploration, to locate new economic gold deposits especially within well-endowed mature orogenic terrains, where exploration risk could be minimized by leveraging on new forward-thinking initiatives like Artificial Intelligence (AI) to re-analyze data from previous mining and exploration, allowing for a faster route to a return on investment. In a world of diminishing natural resources, the potential for previously ignored gold mineralization like the one at Blue Rock, becomes very significant. The prophetic words of Foster (1984), writing in Gold ‘82, therefore remain true and relevant to our time, that; “…. the way ahead for successful gold exploration is to search for new deposits not commonly recognized – in auriferous muds, disseminations in carbonate rocks, porphyries, and in felsic intrusive and extrusive volcanics…”. , Thesis (MSc) -- Faculty of Science, Geology, 2024
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  • Date Issued: 2024-10-11

HI analysis of resolved galaxies in the MeerKAT Absorption Line Survey

  • Authors: Maina, Eric Kamau
  • Date: 2024-10-11
  • Subjects: MeerKAT , Galaxies Clusters , Square Kilometre Array , H I region
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466701 , vital:76771 , DOI https://doi.org/10.21504/10962/466701
  • Description: This doctoral thesis examines two galaxy groups, Klemola 31 and UGC439, leveraging the observational capabilities of the MeerKAT Absorption Line Survey (MALS). The focus was on studying the interstellar medium, specifically the neutral hydrogen (H i) content, distribution, density, and dynamics, through high spatial resolution observations of these groups, and therefore offering insights into the complex processes affecting galaxy evolution in different environments. To make use of an additional tool, the absorption line characteristics of Hi in the two observed systems were analysed and compared with the kinematics and the morphology as induced by the observation of the Hi emission line in the same systems. For Klemola 31, this thesis identifies significant Hi deficiencies and interactions between member galaxies, with notable evidence of tidal interactions between Klemola 31 A and Klemola 31 B as well as ESO400-11 and LEDA2807038; and possible ram-pressure stripping in ESO400-13. The combined analysis of the Hi in emission and absorption indicates the presence of an extraplanar and potential intra-group medium in the group. The UGC439 group was observed in the commissioning phase of the MeerKAT array, revealing contrasting Hi distributions, with the central three galaxies indicating Hi excess while the peripheral galaxies indicating Hi deficiencies. There are two Hi clouds, one close to the central three galaxies and the other to the north. In this case, the observations are consistent with an Hi absorption system from within the disk of a galaxy. This thesis also highlights the necessity for further high spatial and spectral resolution observations to further reveal the intricacies of gas dynamics and its critical role in the life-cycle of galaxies. It serves as an outlook for further studies of the Hi environment of galaxies by combining absorption and emission line studies as first provided by MALS and ultimately by deep Hi surveys with the Square Kilometre Array. This thesis is organised into four chapters. The first chapter details a few concepts and background information about the physics of galaxy evolution. Chapter two talks about Klemola 31 galaxy group, where we start by describing our observation, data reduction and source finding. Thereafter, we explore the Hi morphology and kinematics of this group. In Chapter Three, we turn our attention to UGC439 galaxy group and organise it in a similar manner. A summary and comparison of the two groups is presented in Chapter 4. , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2024
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  • Date Issued: 2024-10-11

Immobilisation of an Aspergillus niger derived endo-1,4-β-mannanase, Man26A, for the production of prebiotic mannooligosaccharides from soybean meal

  • Authors: Anderson, Amy Sage
  • Date: 2024-10-11
  • Subjects: Aspergillus niger , Soybean meal , Mannosidases , Oligosaccharides , Immobilized microorganisms
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/463897 , vital:76455
  • Description: This study investigated the potential for antibiotic alternatives in the form of prebiotics produced from the enzymatic breakdown of soybean meal (SBM). This study first investigated the immobilisation of an endo-1,4-β-mannanase derived from Aspergillus niger on glutaraldehyde-activated chitosan nanoparticles (CTS) and glutaraldehyde-activated chitosan-coated magnetic Fe3O4 nanoparticles (MAGS-CTS) - which could be effectively used to hydrolyse the galactomannan contained in SBM in a recyclable manner. The mannooligosaccharides (MOS) produced from the enzymatic digestion of SBM were then analysed for their prebiotic and antimicrobial capabilities to determine whether the strategy employed was capable of promoting and inhibiting probiotic and pathogenic growth, respectively. An Aspergillus niger endo-1,4-β-mannanase, Man26A, was confirmed by FTIR (Fourier-transform infrared spectroscopy) and XRD (X-ray powder diffraction) to be immobilised onto CTS and MAGS-CTS by covalent bonding. The immobilisation (%) and activity yields (%) were 81.14% and 35.45%, and 55.75% and 21.17%, respectively. The biochemical properties (pH and temperature optima, and temperature stability) of both the free CTS and MAGS-CTS immobilised Man26A enzymes were evaluated, with the pH optima shifting to a lower pH range after immobilisation (pH 2.0 – 3.0 vs. 5.0), while the temperature optima and stabilities remaining unchanged (at 60°C). CTS and free enzymes exhibited identical thermal stabilities, maintaining 100% activity for the first 6 hours at 55°C, while MAGS-CTS showed an immediate drop in relative activity after the first 30 minutes of incubation. Recyclability analysis revealed that CTS could be effectively reused for six reaction cycles, while the MAGS-CTS immobilised enzyme could only be used once. Both enzymes could be efficiently stored at 4ºC, showing a relative residual activity of 73% after 120 hours of storage. Substrate kinetic analysis showed that the free enzyme had the highest catalytic capabilities in hydrolysing locust bean gum (LBG), with the CTS immobilised enzyme was the most efficient in hydrolysing SBM, the insoluble, complex substrate. Sugar residues produced from the hydrolysis of LBG illustrated the effective breakdown of galactomannan to mannobiose (M2), mannotriose (M3), mannotetrose (M4), and mannohexose (M6). SBM-produced sugars analysed via TLC and HPLC indicated that the MOS residues were most probably glucose, galactose, and galactomannans (GM2 and GM3). The SBM-produced sugars were then evaluated for their prebiotic effect, illustrating their successful utilisation as a carbon source by probiotic bacteria; Streptococcus thermophilus, Bacillus subtilis and Lactobacillus bulgaricus. Evaluation of the antimicrobial activities of the SBM-produced sugars digested by probiotics suggested that their metabolites had the potential to be used as an antibiotic alternative. This study therefore illustrated that an endo-1,4-β-mannanase derived from Aspergillus niger could be immobilised successfully, for use in a recyclable reaction to produce MOS products. This study also described the successful use of SBM-sugars as a prebiotic, indicating a successful alternative to antibiotic growth promoters (AGP) by illustrating their positive effect on inhibiting growth of pathogenic bacterial species. , Thesis (MSc) -- Faculty of Science, Biochemistry, Microbiology & Bioinformatics, 2024
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  • Date Issued: 2024-10-11

Integrating sustainability into strategic decision making in the South African automotive sector

  • Authors: Makaudi, Tuelo Ivan
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/461874 , vital:76247
  • Description: Sustainability has become a major topic for businesses, policy makers, government, and researchers. With the growing awareness of climate change, environmental and social problems, attention has turned to how businesses impact the environment, society, and economy. Sustainability, therefore, requires the integration of environmental and social issues into strategic decision making. Many organizations consider sustainability as an important issue for the business. However, some companies are struggling to combine business success and the success of other stakeholders, particularly those representing the interests of the environment and society. The purpose of this case study is to explore how sustainability is integrated into strategic decision making within some companies in the South African automotive industry. This study followed a qualitative approach, and semi-structured interviews were conducted with ten senior managers in the automotive sector in South Africa. The study used an inductive thematic analysis approach to analyse the data, and five main themes were generated: (1) Business profitability, (2) Organization culture, (3) Rationality, (4) Compliance, and (5) Corporate social responsibility (CSR). The findings of the study indicated that strategic decisions made considered business profitability first and foremost above environment and society. There is evidence that businesses engage in some sustainability activities, but this was related to the business objective to be profitable and to meet compliance requirements. The findings of the study also indicated that a rational decision-making approach was used predominantly, compared to intuitive and political approaches. This was due to the cautious approach of maintaining profit-making as a primary business objective. In terms of recommendations, this study recommends that automotive companies in South Africa integrate sustainability considerations into organizational/or business strategy to enable the industry to create shared value for the environment, society and economy. Integrating sustainability into business strategy will align business practices with sustainability goals and therefore allowing the automotive industry to have a positive impact in the society and environment which in turn will lead to improved financial performance. , Thesis (MBA) -- Faculty of Commerce, Rhodes Business School, 2024
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  • Date Issued: 2024-10-11

Interaction of Arbuscular Mycorrhiza and Solanum Tuberosum

  • Authors: Chifetete, Varaidzo Winnie
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466513 , vital:76737
  • Description: Restricted access. Expected release in 2026. , Thesis (PhD) -- Faculty of Science, Biochemistry, Microbiology and Bioinformatics, 2024
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  • Date Issued: 2024-10-11

Investigating deep-seated factors that can condition English First Additional Language literature teaching in Grade 7

  • Authors: Ntikinca, Xolela
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/463757 , vital:76438
  • Description: Access restricted. Expected release in 2026. , Thesis (MEd) -- Faculty of Education, Institute for the Study of Englishes of Africa, 2024
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  • Date Issued: 2024-10-11

Investigating optoelectronic and thermal properties of perylene tetracarboxylic bisimide derivatives-and-cellulose nanocomposites for possible solar energy applications

  • Authors: Ndwandwe, Bongeka Lethukukhanya
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/464554 , vital:76521
  • Description: Restricted access. Expected release in 2026. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
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  • Date Issued: 2024-10-11

Investigating teachers’ post-pandemic management of mathematics content coverage in Grade 3

  • Authors: Damaske, Inge Gerda
  • Date: 2024-10-11
  • Subjects: COVID-19 Pandemic, 2020- Influence , Mathematics Study and teaching (Elementary) South Africa City of Tshwane Metropolitan Municipality , Elementary school teachers South Africa City of Tshwane Metropolitan Municipality , Educational technology , Curriculum planning
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/463691 , vital:76432
  • Description: This study investigated how teachers managed and continue to manage mathematics content coverage in Grade 3 during the COVID-19 pandemic and now post the pandemic. In particular my study sought to understand technologies that teachers may have drawn on during the pandemic in support of curriculum coverage and those that they continue to use. In addition, the study began with a detailed documentary analysis of all available documentation provided to schools and teachers about the management of teaching and curriculum coverage during the pandemic as this provides understanding of the policy and guidelines context in which teachers were working. Thus, in this research I investigated the research questions: i) How have teachers managed the stipulated curriculum coverage in Grade 3 mathematics during the pandemic? and ii) How are teachers continuing to manage this post the pandemic. This included identifying how much and what type of support teachers were given from various stakeholders in the primary education system. Here the levels of support from school principals, governing bodies and more importantly the Department of Basic Education were analysed. This research, situated within an interpretative paradigm, was guided by the sociocultural theory inherent in the concerns-based adoption model. The levels of use within the concerns-based adoption model were adapted to suit the South African context of the study. Participants of the study were 18 teachers from different quintile schools within the Tshwane South District. Key findings included that the Department of Basic Education (DBE) provided a range of documents aimed at adjusting content coverage in response to the altered school calendar during the pandemic. Notable adjustments, particularly in the Annual Teaching Plans (ATPs) of 2020, revealed discrepancies in allocated school days and modifications in content areas such as numbers, operations, geometry, measurement, and data handling. The reduction in the number range and fluctuations in measurement components were observed. Despite the provision of guidelines, the study notes challenges in maintaining continuity and optimal learning, with indications of non-compliance with provided ATPs. The study further found that teachers in different quintile schools adopted diverse strategies for mathematics content coverage during the pandemic. Quintile 5 schools, often well-resourced, reported effective remote teaching using tools like PowerPoint and MS Teams. In contrast, teachers in quintiles 3 and 4, more impacted by school closures, employed varied methods, including extra lessons. Surprisingly, teachers in well-resourced private schools reported gaps in learners' mathematical knowledge, emphasizing the flexibility they have in curriculum coverage. Technology played a pivotal role in facilitating remote teaching during the pandemic, with tools like WhatsApp, MS Teams, and Zoom being widely used, where available. The study underscored the impact of technology on curriculum coverage, especially in well-resourced schools. Grade 3 teachers expressed challenges in meeting unrealistic expectations for curriculum coverage, citing gaps in learners' understanding. The study highlighted a discrepancy between the resources provided by the DBE and the actual needs on the ground, signalling a need for policymakers to become more understanding to the situations in schools. The lack of support from the DBE prompted teachers to become flexible, adapting teaching strategies and supporting each other to navigate the challenges posed by the pandemic. The study concludes by noting the evolving mindset of teachers, transitioning through different levels of Concerns-Based Adoption Model (CBAM), ultimately showcasing their resilience and adaptability in managing curriculum coverage with the available resources. , Thesis (MEd) -- Faculty of Education, Primary and Early Childhood Education, 2024
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  • Date Issued: 2024-10-11

Investigating the relationship between Adverse Childhood Experiences (ACE) and attention skills in children living with HIV

  • Authors: Ngomane, Sibongile
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/465821 , vital:76656
  • Description: Background: While persons living with HIV (PWH) have benefited from significant advances in antiretroviral (ARV) treatment, neurocognitive deficits sequent HIV, remain elevated in this population. Notwithstanding HIV, adverse childhood experiences (ACEs) have been implicated in compromised neurocognitive outcomes in children living with HIV. There however, continues to be a dearth of research, investigating the intertwined nature of HIV, ACEs, and neurocognition in pediatric and adolescent HIV. Objectives: This study investigated the relationship between ACEs (High vs Low) and attention outcomes, in children and adolescents, living with HIV, a residing at HIV care shelters in South Africa. Methods: A non-experimental quantitative research design, inclusive of 42 participants (n = 22 males; n = 20 females), was employed to answer the research questions pertinent to the study. Measures of neurocognition were assessed using the NEPSY-II. Adverse childhood experiences were assessed using the ACE CYW-Qs. Independent Sample t-test and Hierarchical regression analysis were conducted to answer research goals, using jamovi 2.3.21 statistical software. Results: The study found that participants who reported a high number of ACEs also performed poorly on attention measures. There were inconclusive findings on the effect of biological sex and age, on attention outcomes. Conclusion: Higher levels of childhood adversities are associated with poorer outcomes in attention scores among children living with HIV. , Thesis (MA) -- Faculty of Humanities, Psychology, 2024
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  • Date Issued: 2024-10-11

IT business consulting competencies to address business intelligence and analytics challenges in South African organisations

  • Authors: Chatapura, Ruvimbo Faith
  • Date: 2024-10-11
  • Subjects: Business enterprises Information technology South Africa , Business intelligence , Business analytics , Business consultants , Dynamic capabilities , Knowledge management
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/462680 , vital:76325
  • Description: Background: In today's dynamic environment, the importance and popularity of business intelligence and analytics (BI&A) has increased due to the rise in big data being generated across the globe. BI&A is an essential emerging business competency area and dynamic capability that serves as an enabler for organisations to harvest value from their big data. When implemented correctly, BI&A is a powerful tool that leads to increased competitive advantage. However, organisations in South Africa are facing major challenges when it comes to adopting and harnessing it. As such, it is IT business consultants that South African organisations turn to for acquiring BI&A expertise. Objective: Using the Theory of Dynamic Capabilities as an underpinning lens, the purpose of this study is to investigate the relevant competencies IT business consultants need to address BI&A challenges in South African organisations. This study focuses on developing a BI&A competency framework based on these competencies that IT business consultants can consider when addressing the BI&A challenges in South African organisations. Methods: A qualitative research approach was utilised in this study by making use of an interpretive paradigm, abductive reasoning, qualitative description research strategy, as well as semi-structured interviews and questionnaires as data collection methods to elicit feedback on this study’s BI&A competency framework. Content analysis was conducted to categorise and code the interview data, and descriptive analysis was conducted to rank the competencies in order of relevance. Findings: It was found that the relevant business competencies to consider are business acumen, industry knowledge and strategic conceptual abilities. The relevant technical competencies are categorised into three categories: analytical skills (logical thinking, problem-solving, statistical analysis and what-if analysis), data engineering (data modelling skills, data warehousing, database management, data governance, data interpretation, data stewardship, data visualisation tools and data processing languages) and supplementary skills (project management, consulting skills and artificial intelligence). The relevant values and behavioural competencies to consider are integrity, communication, teamwork, resilience, commitment, creativity, emotional intelligence, humility, behavioural analysis, curiosity, leadership and social intelligence. , Thesis (MCom) -- Faculty of Commerce, Information Systems, 2024
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  • Date Issued: 2024-10-11

KalCal: a novel calibration framework for radio interferometry using the Kalman Filter and Smoother

  • Authors: Welman, Brian Allister
  • Date: 2024-10-11
  • Subjects: Radio interferometers , Calibration , Kalman filtering , Bayesian inference , Signal processing , Radio astronomy , MeerKAT
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/467127 , vital:76818
  • Description: Calibration in radio interferometry is essential for correcting measurement errors. Traditional methods employ maximum likelihood techniques and non-linear least squares solvers but face challenges due to the data volumes and increased noise sensitivity of contemporary instruments such as MeerKAT. A common approach for mitigating these issues is using “solution intervals”, which helps manage the data volume and reduces overfitting. However, inappropriate interval sizes can degrade calibration quality, and determining optimal sizes is challenging, often relying on brute-force methods. This study introduces Kalman Filtering and Smoothing in Calibration (KalCal), a new framework for calibration that combines the Kalman Filter, Kalman Smoother, and the energy function: the negative logarithm of the Bayesian evidence. KalCal offers Bayesian-optimal solutions as probability densities and models calibration effects with lower computational requirements than iterative approaches. Unlike traditional methods, which require all the data for a particular solution to be in memory simultaneously, KalCal’s recursive computations only need a single pass through the data with appropriate prior information. The energy function provides the means for KalCal to determine this prior information. Theoretical contributions include additions to complex optimisation literature and the “Kalman-Woodbury Identity” that reformulates the traditional Kalman Filter. A Python implementation of the KalCal framework was benchmarked against solution intervals as implemented in the QuartiCal package. Simulations show KalCal matching solution intervals in high Signal-to-Noise Ratio (SNR) scenarios and surpassing them in low SNR conditions. Moreover, the energy function produced minima that coincide with KalCal’s Mean Square Error (MSE) on the true gain signal. This result is significant as the MSE is unavailable in real applications. Further research is needed to assess the computational feasibility and intricacies of KalCal. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2024
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  • Date Issued: 2024-10-11

Macroinvertebrate population dynamics, community composition and diversity patterns of two coastal lakes in northern KwaZulu-Natal, South Africa

  • Authors: Campbell, Kaylee Maria
  • Date: 2024-10-11
  • Subjects: Indicators (Biology) , Lakes South Africa KwaZulu-Natal , Sibayi, Lake (South Africa) , Lake Mzingazi Dam , Biological monitoring South Africa KwaZulu-Natal , Biodiversity , Geospatial data South Africa KwaZulu-Natal , Land use Planning South Africa KwaZulu-Natal
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/464406 , vital:76508
  • Description: The 2018 South African National Biodiversity Assessment (NBA) identified eight freshwater lakes of national ecological importance and a lack of understanding of their biology. The assessment further called for baseline foundational data for their conservation. Aquatic invertebrates are considered to be reliable and sensitive biological indicators of environmental and water quality changes, and understanding aquatic invertebrate dynamics in these systems will provide a comprehensive understanding of how they can be better protected. The NBA also highlighted a gap in data associated with ecological response to landscape developments and climate change (mainly below average precipitation and increased temperatures) and how this contributes to aquatic resource conservation. This further complicates the modelling of important ecological thresholds and hampers the prediction of possible responses of these ecosystems to environmental changes. This gap informed the aims and rationale of this dissertation; to identify longer-term spatiotemporal trends in aquatic invertebrate communities in Lake Sibaya and Lake Mzingazi and to determine whether the surrounding land use changes could lead to long-term changes in aquatic invertebrate communities of both lakes by comparing recent survey data with historical datasets. In Chapter 2, this dissertation investigated the population dynamics of freshwater shrimp, Caridina africana in Lake Sibaya and Mzingazi and compared the data to that of 1975 study published by Hart (1981). This was done to assess any changes in the C. africana populations due to the considerable changes in land use and weather patterns that have occurred in the last 48 years in and around the systems. Results from Lake Sibaya and Lake Mzingazi were also compared to determine any differences in urban and agricultural stressors presented to C. africana populations. This chapter hypothesised that increases in anthropogenic pollution, invasive species and other habitat modifications at Lake Sibaya and Lake Mzingazi would lead to (1) reductions in shrimp densities and changes in population dynamics when comparing with the 1975 data from Hart (1981). Additionally, it was predicted that (2) Caridina africana abundances found at Lake Mzingazi would be lower than those found at Lake Sibaya (3) due to different water quality variables associated with land use. Results showed that C. africana population densities at Lake Sibaya and lake level recordings had experienced significant decreases since 1975 with densities being significantly lower in 2021. Additional differences seen in 2021 when compared to 1975 were that females were more abundant than males, individuals between the sizes of 3mm and 5mm were most abundant instead of those in the smallest size class (<0.83mm – 1.67mm) and females only dominated size classes above 4mm instead of all size classes above 2.5mm. Populations at Lake Sibaya were negatively correlated with nitrate concentrations in 2021 and populations at Lake Mzingazi were negatively correlated with temperature according to generalised linear models. These results emphasized the importance of pollution mitigation, sustainable water abstraction and the maintenance of natural water temperature ranges in the conservation of lentic C. africana populations. There was also no evidence that urbanisation and agriculture presented different threats to freshwater shrimp populations. In Chapter 3, this dissertation aimed to quantify the littoral aquatic invertebrate diversity and assemblage patterns from Lake Sibaya and Lake Mzingazi to provide comprehensive baseline datasets for these coastal systems. This chapter also aimed to investigate the impacts of landscape developments and habitat change on aquatic invertebrate communities by understanding significant water quality parameters as drivers of community variation. Predictions for Chapter 3 were that increases in agricultural and anthropogenic disturbance and habitat modification will lead to (1) aquatic invertebrate community composition at lakes Sibaya and Mzingazi being structured according to water quality variables that stem from surrounding land-use activities, leading to (2) differing community structures at each lake. Lastly, it was hypothesised that (3) the presence of the invasive snail Tarebia granifera would likely be affecting the aquatic invertebrate diversity and composition of both lakes. According to linear models, aquatic invertebrate abundance at Lake Sibaya was negatively affected by salinity, lake level and phosphate concentration, and positively associated with temperature. Taxa richness and Pielou’s evenness at the lake were negatively associated with conductivity and nitrate concentrations respectively. The aquatic invertebrate community at Lake Sibaya also followed typical seasonal patterns. At Lake Mzingazi, Pielou’s evenness was negatively associated with nitrate and ammonium concentrations and no typical seasonal patterns were evident in the community composition. Communities at Lake Mzingazi also exhibited resilience despite changes in physicochemical parameters, emphasising the difficulty in predicting aquatic community response to habitat modification due to lake-specific community resilience. Tarebia granifera populations at Lake Sibaya were found to negatively affect invertebrate diversity scores according to generalised linear models. Additionally, no individuals of Melanoides tuberculata were found in either system indicating the possibility that these native snails may have been outcompeted by their invasive counterpart. The prevalence of significant stressors associated with habitat disturbance and the unexpected results seen at Lake Mzingazi emphasized the importance of monitoring aquatic invertebrate communities in response to climate change and associated land use developments to adequately understand the long-term threats these changes pose to freshwater ecosystems and biodiversity conservation. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2024
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  • Date Issued: 2024-10-11

Mediating learning of electrostatics through stories on cultural beliefs and practices about lightning to Grade 7 township school learners

  • Authors: Funani, Lindiso Desmond
  • Date: 2024-10-11
  • Subjects: Science Study and teaching (Primary) South Africa , Electrostatics , Lightning South Africa , Traditional ecological knowledge South Africa , Argumentation theory , Social learning South Africa
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/463548 , vital:76419
  • Description: The Curriculum and Assessment Policy Statement (CAPS) document mandates that teaching and learning should start with the knowledge and experiences of learners from home or communities when teaching Natural Sciences. The aim is to bridge the gap between the science content learned in the school classroom and the science accessible to learners in their homes and community environments. CAPS claims that it ‘embraces local indigenous knowledge’ but it does not specify how this should be done in schools. As a result, little or no integration of Indigenous Knowledge (IK) is enacted in many of our schools in South Africa and learners seem to find science inaccessible and irrelevant to their everyday lives. It is against this backdrop that this interventionist study sought to mediate learning of electrostatics through harnessing stories on cultural beliefs and practices about lightning to Grade 7 township school learners. This study is located within the interpretivist and Indigenous research paradigms, central to which is to develop a greater understanding of how people make sense of the contexts in which they live and work. Within the Indigenous research paradigm, I focused on the Ubuntu perspective. Furthermore, this study was conducted in an under-resourced school located in the Sarah Baartman District, Eastern Cape Province of South Africa. The participants were Grade 7 Natural Sciences learners and two Indigenous Knowledge Custodians (IKCs). In addition, one Natural Sciences teacher was my critical friend. Focus group interviews (sharing circles), group activities, observations (participatory and lesson observation), and learners’ journals were used to gather data. Vygotsky’s sociocultural theory and Ogunniyi’s Contiguity Argumentation Theory were used as theoretical frameworks in this study. The findings of the study revealed that both the group activity and the presentations by the Indigenous Knowledge Custodians on stories on cultural beliefs and practices about lightning enabled learners’ argumentation and sense-making of electrostatics. The study thus recommends that science teachers should make efforts to tap into the cultural heritage of IKCs to make science accessible and relevant to learners' everyday life experiences. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
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  • Date Issued: 2024-10-11

Mediating learning of nutrition through using traditional food processing and preservation to grade 6 rural school learners

  • Authors: Tyeda, Nomvume
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/463658 , vital:76429
  • Description: Rural learners, especially those in the school where I teach, seem to grasp science in a disconnected manner, and hence struggle to understand it. This concern aligns with the findings of the Trends of International Mathematics and Science Studies, which notes poor performance in science among learners in South Africa. When examining these challenges, learners appear to inhabit a realm divided by a river, struggling to bridge the gap between what they learn at home and what is taught at school. Against this context, this research aimed to mediate the learning of nutrition for Grade 6 rural school learners by integrating traditional ways of food processing and preservation. The interpretivist and Indigenous research paradigms underpin the research. I used the Ubuntu perspective within the Indigenous research paradigm, which emphasises respect and humble togetherness. This qualitative case study took place at a rural school in the OR Tambo Coastal district in the Eastern Cape. It involved 14 Grade 6 Natural Sciences and Technology learners, a critical friend, and two Indigenous Knowledge Custodians. Various methods were used to collect data, including group activities by learners, participatory and lesson observation, focus group interviews (sharing circles), and learners’ journal reflections. The findings of the study revealed the significance of integrating Indigenous Knowledge with modern scientific principles, engaging in experiential and hands-on learning activities, involving Indigenous Knowledge Custodians, and using visual learning aids to enhance learners’ engagement and sense-making of nutrition. The study recommends that Indigenous Knowledge should be integrated with modern science to provide a comprehensive understanding of the topic of nutrition. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
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  • Date Issued: 2024-10-11

Mediating learning of sound through cultural music and dance stories to Grade 4 farm school learners

  • Authors: Tshitshi, Hlengiwe
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/463647 , vital:76428
  • Description: The current South African Natural Science and Technology (NS-Tech) curriculum for grades 4–9 encourages teachers to integrate Indigenous Knowledge (IK) into their teaching. By doing so, it is hoped that this would contextualise and make science relevant to learners. However, the contradiction is that IK is hardly discussed in the curriculum and there are no clear guidelines on how to integrate it. It is against this background that in this study I used stories about cultural beliefs and practices on traditional music and dance to support Grade 4 NS-Tech from a farm school talking about and making sense of the topic of sound. This study is underpinned by the interpretivist and Indigenous research paradigms. Within the Indigenous research paradigm, I focused on the Ubuntu perspective. A qualitative case study research design was employed, and the study was conducted in the Sarah Baartman District of the Eastern Cape. Four Grade 4 learners and four Indigenous Knowledge Custodians who were all family members were participants in this study. In addition, I invited an NS-Tech teacher to be my critical friend in this study. A focus group interview (sharing circle), participatory and lesson observations and learners’ journal reflections were employed to gather data. Vygotsky’s sociocultural theory together with Ogunniyi’s contiguity argumentative theory were used as lenses to analyse data. A thematic approach to data analysis was employed to come up with sub-themes. Thereafter, common sub-themes were subsequently combined to form themes. The findings of this study revealed that the following factors can significantly enable/constrain the ability of Grade 4 Natural Sciences and Technology learners from a farm school to comprehend and engage with the topic of sound: (1) integration of IK into science lessons, (2) Experiential learning through hands-on activities, (3) Community involvement in knowledge acquisition, and (4) Emotional effect of loud sounds. In addition, the contribution of Indigenous Knowledge Custodians facilitated a notable enhancement in learners’ dialogue and understanding of sound. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
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  • Date Issued: 2024-10-11

Medical pluralism amongst Makhanda traditional health practitioners: Exploring dispositions to COVID-19 vaccinations

  • Authors: Mothapo, Lebogang
  • Date: 2024-10-11
  • Subjects: Traditional healer Attitudes , Integrative medicine , COVID-19 vaccines , COVID-19 Pandemic, 2020-2023 Influence , Traditional healer South Africa Makhanda
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/466284 , vital:76714
  • Description: ‘Healers and healing’, ‘wellbeing and prevalence’, ‘medical systems and progression’. Every healing concept is tied to people’s perspectives, thoughts, beliefs, and backgrounds. Worldviews and world perspectives influence these throughout time and space. The progressive postulation between medical systems and the comprehensive relations between them is a narrative worth exploring through the distinct perspectives of Traditional Health Practitioners in Makhanda. This qualitative study sought to explore the dispositions of Traditional Health Practitioners (THPs) towards COVID-19 vaccinations to understand the practice and acceptance of medical pluralism through a traditional lens. Through purposive and snowball sampling, 10 participants were recruited and semi-structured in-depth interviews were conducted as a tool for data collection. Thematic data analysis was conducted to analyse the data, and multiple codes that led to themes emerged. THPs exhibit multiple concepts tied to COVID-19 vaccination, representing the dynamic understanding of participating in biomedical approaches. THPs, in their decision to uptake the COVID-19 vaccination, are motivated by the severity of the disease and other compelling reasons, such as the obligations and regulations put in place to encourage vaccination uptake in achieving mass/herd immunity. THPs who, in their decision of not uptaking the COVID-19 vaccination, display mistrust, disregard for the COVID-19 vaccination in particular and the entrusted commitment to traditional medicine. In all the expressed dispositions, reliance on the understanding of COVID-19 and the dependence on lived experiences played an integral role in how THPs responded to COVID-19 vaccinations. Due to this understanding, the practice of medical pluralism amongst Makhanda THPs is understood through context-based concepts to explore the in-depth multifaceted positioning of medical pluralism. , Thesis (MSocSci) -- Faculty of Humanities, Anthropology, 2024
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  • Date Issued: 2024-10-11

Meerkat polarimetric observations of Pictor A

  • Authors: Andati, Lexy Acherwa Livoyi
  • Date: 2024-10-11
  • Subjects: Polarimetry , MeerKAT , Radio astronomy , Radio galaxies , Cosmic magnetic fields , Pictor A
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466896 , vital:76796 , DOI https://doi.org/10.21504/10962/466896
  • Description: Pictor A is one of the brightest and closest radio galaxies in the Southern Hemisphere, offering a unique opportunity for in-depth studies of the astrophysics of radio galaxies and their interactions with their environments. Many multi-wavelength studies of this source have been done. However, the most comprehensive radio frequency study of Pictor A’s morphological components was conducted by Perley et al. (1997) using the Very Large Array (VLA) located in the Northern Hemisphere. To date, that work remains the most detailed study of Pictor A. In this thesis, we conducted a spectropolarimetric study of Pictor A using new L-band data obtained in 2019 from the high-sensitivity MeerKAT telescope, which provides the deepest and most sensitive data of this source at a continuous and finely sampled frequency coverage in the L-band. Thus, due to Pictor A’s proximity, high luminosity, and the MeerKAT’s high sensitivity, the data delivers a unique dataset for our study of the magnetic field structure of Pictor A and allows for a detailed study of the source’s morphological structures. We presented the steps taken during our calibration and data reduction, leading to polarimetryready images. During the first phase of calibration, excision of data corrupted by instrumental effects and radio frequency interference (RFI) resulted in only 50% useable data. Pictor A’s exceptionally bright western hotspot introduced significant artefacts in our images, mitigated in the second calibration phase through direction-dependent calibration. The calibrated data resulted in a multi-frequency synthesis (MFS) Stokes I image of Pictor A at 7.5′′ in resolution with an offsource RMS noise of ∼22 𝜇Jy/beam. The off-source noise in the Stokes Q and U sub-band images ranged between 95 – 278 𝜇Jy/beam and 41 – 233 𝜇Jy/beam, respectively. Additionally, we briefly highlighted the effects of RFI in the L-band on polarimetry, particularly the considerable loss of 𝜆2 coverage of ∼50%. All the calibration recipes used for this work were made available in this thesis. Using Pictor A’s data as a testbed, we introduced a Python-based tool, Smops, developed during the calibration stages of our work. Smops was designed for an intermediate post-processing step. It interpolates input sub-band model FITS images (such as those produced by WSClean) into finely channelized sub-band model FITS images, thereby generating model images at a higher frequency resolution. Smops reduces the need to generate model images with numerous sub-bands, which is computationally intensive and time-consuming. A higher resolution in frequency of the models facilitates more efficient model subtraction during self-calibration. We then presented the total intensity features of Pictor A, which the calibrated data reveals. We confirmed the presence of Pictor A’s radio jet extending from its core to the western hotspot. Notably, this feature, faint and barely visible in previous radio images, is now distinctly observed. The counterjet remains undetectable. Furthermore, we demonstrated the coexistence of radio emission, which is expected to align with previously observed X-ray diffuse emission. This observation confirmed the inverse Compton origin of Pictor A’s lobe emission. Employing the RM-synthesis technique for the spectropolarimetric study of Pictor A, we identified a relatively consistent rotation measure (RM) across its lobes, with an average RM of 48.06 ± 10.19 rad m−2 for the entire source. However, the eastern lobe displayed a wider RM dispersion than the western lobe. Moreover, our study affirmed the depolarisation asymmetry previously observed between the western and eastern lobes of Pictor A, where the eastern lobe exhibited significantly more depolarisation than its western counterpart. Most lines-of-sight across Pictor A displayed single-peaked Faraday spectra, indicating a single Faraday rotating screen. However, we also noted that several lines-of-sight (∼23%) showed more than one Faraday peak. An investigation into the ii possible causes of the multiple observed peaks using QU-fitting suggested that there is a possibility of a Faraday thick structure or multiple Faraday components along these paths. Furthermore, we estimated a Galactic RM contribution towards Pictor A of 23.57 ± 10.87 rad m−2. We concluded that while our Galaxy may contribute to the mean RM for this source, it cannot explain smallscale fluctuations, which suggests that some fraction of the observed rotation measures could result from some inter-galactic medium, X-ray gas near the shock boundary region (the sheath), or other unknown intervening material. We introduced Scrappy, a Python-based tool tailored for processing lines-of-sight data. Scrappy yields RM-synthesis diagnostic data products such as the data associated with each line-of-sight, and their corresponding plots in 𝜙-space (e.g. cleaned and dirty Faraday spectra and RMTF), and 𝜆2-space (e.g. the fractional polarisation, and Stokes Q and U ). Scrappy further avails a Bash-based pipeline, showrunner.sh, that processes input sub-band Stokes images, automatically selects usable sub-bands, stacks images into Stokes cubes, generates lines-of-sight, processes their corresponding data, and produces diagnostic plots. Additionally, it creates per-pixel maps of fractional polarisation, RM, polarisation angle, peak FDF, and linear polarised intensity. The pipeline ensures reproducibility. To visualise the diagnostic plots from Scrappy, we developed PolarVis, a simple web-based tool that enables the visualisation of diagnostic plots associated with each available line-of-sight, thus facilitating the quick exploration of interesting lines-of-sight in regions across this source. This tool facilitates the visualisation of polarisation behaviour for specific lines-of-sight, enabling quick identification of interesting regions of the source. Furthermore, its interactivity promotes the exploration of line-of-sight data. Availing data to the public with this tool permits validation or comparison of results from varying techniques, hence fostering a sense of transparency. As a result, the 2389 lines-of-sight of Pictor A are presented using PolarVis and are available at https://pica.ratt.center. , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2024
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  • Date Issued: 2024-10-11

MeerKAT: a journey from commissioning to science

  • Authors: Hugo, Benjamin Vorster
  • Date: 2024-10-11
  • Subjects: MeerKAT , Interferometry , Ionosphere , Pulsars
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466871 , vital:76794 , DOI https://doi.org/10.21504/10962/466871
  • Description: This dissertation presents a collection of work completed for the South African Radio Astronomy Observatory in characterizing calibrator fields PKS B1934-638, PKS B0407-65 and 3C286, the development of a facet-based multi-direction peeling scheme for the CUBICAL calibration framework and incorporation into an end-to-end containerized data reduction framework, a study of a transitional millisecond pulsar candidate, and characterization of baseline dependent archiving tooling for MeerKAT. Our long term studies of PKS B1934-638, PKS B0407-65 indicate that these bandpass and flux calibrators are stable over multiple years. We also find that, especially at low frequencies in the UHF band, the population of sources surrounding these stellar Gigahertz Peaked Sources (GPS) can contribute to errors two to three orders of magnitude above desired bandpass calibration solution stability, if left unmodeled. We derive new new full sky models of these fields, currently in use by the MeerKAT Science Data Processor. We characterize the MeerKAT feed alignment using the refraction-driven linearly polarized thermal light from the Moon in order to derive a new model for the linear polarization of the stable quasar 3C286 down to 544 MHz. Part of this work includes characterization of ionospheric corrections using the International Global Navigation Satelite System Service and direct measurement of total electron content above the MeerKAT site using interchange data from the South African TrigNET service. We find that current commonly-employed techniques achieve corrections to ionospheric Faraday rotation no better than 1 rad m􀀀2. This is the main limitation on the accuracy of polarimetric observation using the MeerKAT array. We find that 3C286 intrinsically depolarizes at frequencies below 1 GHz, with an associated non-linear increase in the intrinsic source rotation measure. We present an improvement to workflows using the CUBICAL calibration framework, developed at Rhodes University. Modern radio interferometers presents a significant challenge to calibrate, often necessitating memory and computeintensive direction-dependent calibration towards many directions in order to improve the fidelity of radio images in order to meet scientific goals. We developed a framework to simplify the model prediction aspect of these direction-dependent calibration workflows using targeted faceting. Using our scheme users use models derived from the DDFACET imaging package and only need to provide lattices to mark regions of sky to which direction-dependent calibration solutions need to be solved for. This simplifies a laborious multi-step process in traditional calibration packages that need to be executed per direction. The approach is compared to an image-space corrective regime and incorporated into the VERMEERKAT end-to-end calibration framework for MeerKAT data. The improved direction-dependent calibration techniques were then applied in an analysis of the transitional millisecond pulsar candidate CXOU J110926.4-650224. The link between accreting binary systems (where emission is dominated by the synchrotron emission of relativistic jets from thermo-nuclear reaction onto the Neutron Star surface by the infalling matter) and binary radio pulsars is currently elusive. This is due to the lack of a large population of such transitional systems — only three confirmed transitional systems are known at the time of writing. It is thought that infalling matter effectively quenches the radio pulsar mechanism. Our candidate was found to be variable in the optical and the X-ray, with transitions between low, high and flaring states lasting anywhere from a tens of seconds to tens of minutes, seen in archival observations spanning nearly three decades. For the first time we detect low level synchrotron emission (_ 50 mJy beam􀀀1) coincident with this system using MeerKAT, including a flare within minutes of a flare detected in X-ray using the XMM-Newton observatory. Our analysis indicate that there is no clear anti-correlated behaviour between radio and X-ray state transitions in this system, unlike other candidate systems—indicating that such transitional systems may not exhibit homogenous behaviour. This suggests that the processes driving the X-ray mode-switching in this system are not directly linked to the processes responsible for emitting radio synchrotron radiation. Finally, we consider the problem of MeerKAT data archiving. We present a qualification analysis, using MeerKAT data, of the Rhodes University baseline-dependent archiving package XOVA, which can be used to compress and archive MeerKAT data in interchange standard-compliant format. The data rates from interferometric array radio telescopes, such as MeerKAT, grow as the square of the number of antennas in such an array. For the sake of reproducibility and future reanalysis it is important to archive calibrated visibility products. The degree to which calibrated visibility products can be compressed, by averaging, depends on the amount of smearing that can be tolerated at a fixed distance from the center of the images synthesized from these visibility products. This is, traditionally, set by the longest spacing in the interferometric array, with all other spacings averaged to the same integration and channelization as the longest spacing. We find that, using baseline-dependent averaging techniques – where averaging intervals are set per interferometric spacing – we can achieve space savings an order of magnitude better than traditional averaging approaches, with no appreciable loss of image fidelity when compared to traditional averaging approaches. , Thesis (PhD) -- Faculty of Science, Faculty of Science, Physics and Electronics, 2024
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  • Date Issued: 2024-10-11

Metallophthalocyanines: versatile probes for microbial photoinactivation and for pollutant degradation as photocatalysts, both molecular or supported form

  • Authors: Sindelo, Azole
  • Date: 2024-10-11
  • Subjects: Phthalocyanines , Active oxygen , Nanoparticles , Nanofibers , Glass wool , Photocatalysis
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466614 , vital:76760 , DOI https://doi.org/10.21504/10962/466614
  • Description: This thesis investigates the synthesie of metallophthalocyanines for potential use as photosensitizers in two applications: photodynamic antimicrobial chemotherapy and the photodegradation of organic pollutants. To achieve this, phthalocyanines with morpholine (substituted at alpha and beta position, to imine), ethyl and propyl pyrrolidine Schiff bases, asymmetrical mercaptobenzothiazole and morpholine substituents were synthesized for the first time. All nitrogen containing phthalocyanines were methylated to form cationic derivatives. Asymmetrical mercaptobenzothiazole were covalently linked to spherical and pyramidal zinc oxide nanoparticles, while the asymmetrical morpholine were conjugated to polyacrylonitrile (PAN) nanofibers, chitosan modified PAN and glass wool, while carboxylic acid containing phthalocyanines were also linked to glass wool. Various characterization techniques, including electronic spectroscopy, mass spectroscopy, nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR), elemental analysis, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM), and time-resolved fluorescence measurements were employed to characterize all the phthalocyanine composites. The research aimed to establish general trends in fluorescence quantum yields, triplet and singlet oxygen generation, photodegradation rates, and fluorescence and triplet state lifetimes of the complexes. Notably, the presence of zinc oxide nanoparticles increased the triplet quantum yield of phthalocyanines, however, the singlet oxygen quantum yield decreased. The study also examined the photodynamic inactivation of various planktonic cells and biofilms using all photosensitizers. The photodynamic antimicrobial chemotherapy activities were dose-dependent, and all cationic photosensitizers were highly effective in completely inactivating the microbes in both forms, as opposed to non-charged photosensitizers. For the supports, the chitosan modified PAN showed high efficacy due to improved hydrophilicity. Furthermore, the research was conducted on the photodegradation of 4-chlorophenol, methyl orange and methylene blue using Pc-anchored PAN and glass wool supports. The immobilized photosensitizers demonstrated a strong capacity for generating singlet oxygen in aqueous media, with the cationic Pc-PAN removing methylene blue more efficiently due to its adsorption and photodegradation abilities. All supports were recoverable, showing potential application for future use in the removal of microbes and organic pollutants. , Thesis (PhD) -- Faculty of Science, Chemistry, 2024
  • Full Text:
  • Date Issued: 2024-10-11
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