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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: Uncatalogued
  • 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
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  • Date Issued: 2024-10-11

Metal–organic framework-based heterogeneous catalysts with tailored active sites for precise oxidative transformations

  • Authors: Hulushe, Siyabonga Theophillus
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466581 , vital:76754
  • Description: Access restricted. Exected release in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2024
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  • Date Issued: 2024-10-11

Microplastics as potential vectors for selected organic chemical pollutants in river ecosystems

  • Authors: Tumwesigye, Edgar
  • Date: 2024-10-11
  • Subjects: Microplastics Environmental aspects , Vector , Adsorption (Biology) , Watersheds , Kinetics
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466677 , vital:76766 , DOI https://doi.org/10.21504/10962/466677
  • Description: Microplastics (MPs) as pollutants in river ecosystems have received considerable research attention in recent years. However, in Africa, research on MPs is sparse, and more needs to be done. Empirical evidence suggests that MP can act as vectors of organic chemical pollutants due to their diverse functional groups and other physical-chemical properties, such as their small sizes, crystal structure and porosity. MPs acting as vectors of chemical pollutants, adds to the complexity of understanding the risk posed to both the ecosystem and human health. Regarding the so-called vector effect, the role of seasonality, land use type, adsorption kinetics, and MP properties has yet to receive the necessary research in the literature, especially concerning pharmaceutical active compounds and other organic pollutants in river systems. This is particularly true for Africa, including South Africa. This study, therefore, aimed to fill these existing research gaps. Overall, the study aimed to investigate the potential of selected microplastic polymers of a particular size range as vectors of organic pollutants in urban rivers within the Eastern Cape of South Africa. To achieve this aim, the study explored the influence of spatial-temporal variability, MPs particle sizes, and various physicochemical variables on the adsorption of antibiotics: Sulfamethoxazole, ciprofloxacin, and endocrine disruptors: 17β-Estradiol, 4-(2, 6-dimethyl-2-heptyl) phenol. The adsorption kinetics mechanism was also investigated and established. Polyethylene Terephthalate (PET) and polypropylene (PP) MPs were seasonally deployed once in the summer and autumn seasons, i.e. 20th January 2022 in Bloukrans River and 21st January 2022 in Swartkops River for the summer season and 7th April 2022 in Bloukrans River and 8th April 2022 in Swartkops River for the autumn season. Deployed MPs were of two size ranges, type 1 (2 mm<-≤5 mm) and type 2 (0.5mm<-≤2 mm). The sites where the MPs were deployed had different land use practices: informal settlements, discharge points of wastewater treatment works (WWTWs), agricultural farms, and control sites, considered as the least impacted sites. This was done to analyse land use types' role in the adsorption of chemical pollutants onto MPs. MPs were retrieved in periodic intervals of 7 days, 14 days and 35days calculated based on the day of deployment for both summer and autumn seasons and analysed for Sulfamethoxazole, Ciprofloxacin, 17β-Estradiol, 4-(2, 6-dimethyl-2-heptyl) phenol using high-resolution liquid chromatography–mass spectrometry LC-MS/MS equipped with a triple quadrupole (QqQ) analyser. Concurrent with MP retrieval water physicochemical variables: pH, dissolved oxygen (DO), temperature, turbidity, electrical conductivity (EC), total suspended solids (TSS), total dissolved solids, total alkalinity and total hardness. The adsorption kinetics mechanism was studied in the laboratory between PET and PP of two size ranges and Sulfamethoxazole, Ciprofloxacin, and 17β-Estradiol model chemical. The results indicate that land use practices significantly impacted the concentration of the adsorbed chemicals on MPs. Sites downstream of the WWTW had higher concentrations of Sulfamethoxazole: 11119.6001±12552.4120ngL-1 and ciprofloxacin: 30285.19± 28783.7821ngL-1 adsorbed onto MPs in the Bloukrans River compared to the concentration of same compounds from other land use types along the same River catchment. Agriculturally impacted sites had higher concentrations of 17β-Estradiol on MPs; 11624.5611 ± 15382.2923ngL-1 and 100.3635± 29.6321ngL-1 in Swartkops and Bloukrans Rivers respectively compared to other sites. These results suggest that land use is an essential factor influencing chemical inputs into rivers and their adsorption onto MPs. Adsorption was higher for the MP of smaller sizes compared to MPs with bigger sizes, indicating that size is an essential factor that influences the vector effects of MPs. Adsorption was significantly higher after 35 days than all other days during the two seasons (P< 0.05). The adoption kinetics data fitted well with the pseudo-second-order model (R2> 0.99), indicating that chemisorption mechanisms may be the rate-limiting step. Data did not fit the intraparticle diffusion model. Both film diffusion and intraparticle diffusion possibly influenced the rate-limiting adsorption step simultaneously. Regarding the relationship between adsorption and water physico-chemical variables, of special interest a positive correlation between total alkalinity, electrical conductivity, total hardness, and total suspended salts (TDS) and the concentration of the adsorbed chemicals was observed. While the relationship between adsorption and dissolved oxygen was negative. The physicochemical variables with a positive relationship with adsorption are indicative of pollution. Therefore, the result suggests that increasing pollution tends to favour higher adsorption. The results in this study highlight the insights on i) the influence of land use on adsorption, ii) the role of exposure duration on adsorption, iii) the influence of seasonality and MP sizes on adsorption iv) relationship between water physicochemical parameters and adsorption as well as v) establishing adsorption kinetic mechanism. These findings are critical to better understanding the so-called vector effects of MPs and the management associated with MPs in river systems and form essential data sets needed in developing effective pollution mitigation strategies that are region-specific. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2024
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  • Date Issued: 2024-10-11

Mining MeerKAT data for minute to hour timescale transients and variable sources

  • Authors: Gcilitshana, Sihle
  • Date: 2024-10-11
  • Subjects: MeerKAT , Astronomy Data processing , Radio astronomy , Pipelining (Electronics) , Active galactic nuclei
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/464886 , vital:76554
  • Description: In radio astronomy, minute-to-hour timescale transients and variable sources present an understudied population. We now have an unprecedented view of the transient radio sky due to the advent of new telescopes (such as the MeerKAT) with high instantaneous sensitivity, excellent snapshot imaging capabilities, and a large field of view. We can now probe into this population. This thesis presents the search for minute-to-hour timescale transient and variable sources in two of MeerKAT archival observations: the COSMOS and MACS J2140.2−2339 fields. The fields were observed for eight and five hours at the UHF band, respectively. We employed the PARROT transient and variable search pipeline currently being developed by the RATT group at Rhodes University. The pipeline’s input is a cross-calibrated measurement set, and its outputs are light curves extracted from all the sources in the restored image of the field. Using the light curves from the pipeline, we detected two variable sources in the COSMOS field, scintillating Active Galactic Nuclei (AGNs), which are most likely caused by the turbulent plasma in the interstellar medium. Due to persistent ionospheric diffraction, no variable sources were detected in the MACS J2140.2−2339 field, and no transients were detected in either field. The thesis also highlights areas where improvements to the PARROT pipeline can be implemented. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2024
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  • Date Issued: 2024-10-11

Modelling water quality dynamics by integrating PYWR, climate change, and land-cover scenarios: a case study in the Grootdraai Dam Catchment, Upper Vaal, South Africa

  • Authors: Lazar, Sofia
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/465000 , vital:76564
  • Description: Water resource management faces global challenges in allocation, quality, and sustainability. Despite extensive focus on quantity, water quality remains neglected, especially in developing nations, owing to data scarcity and funding issues. Water quantity modelling is more advanced, leaving water quality modelling lagging, as it requires finer spatiotemporal scales. Global water quality models, including those used in South Africa, encounter complexity and data requirements, and some proprietary models limit access. In South Africa, a water quality model is integrated with the less accessible Water Resources Yield Model (WRYM). However, WRYM's spatial lumping may not suffice for water quality assessment, emphasising the need for improvement. This study aims to address the gap in water quality modelling by transitioning from lumped, proprietary, and monthly time-step models applied in South Africa to more spatially distributed, user-friendly, transparent, fast models and daily time-step models, using the Grootdraai Dam Catchment in the Upper Vaal as a study region. The study examines providing water quality simulation for various variables under different tested scenarios, including (i) land-use scenarios (e.g., urbanisation, industrialisation, population growth and expansion in agricultural areas); (ii) mixed scenarios (e.g., climate change, mine closure, and demand increase). The study proposed a framework shifting from the WRYM to a Python water resources (Pywr) model, linked with the Water Quality Systems Assessment Model (WQSAM) in the Grootdraai Dam Catchment. This integration, the Python water resources-Water Quality (Pywr-WQ) model, was developed by the Water Research centre (WRc) in the United Kingdom. The study employed multiple regression models to develop land-use models, the outcomes of which were integrated into the Pywr-WQ model for medium and long term land-use scenario predictions. The study resulted in the following findings: (1) significant patterns emerge concerning the impacts of urbanisation, mining, and agricultural expansion on water quality; (2) urban areas exhibit elevated levels of nitrate plus nitrite and ammonium over the long term associated with human activities and infrastructure development; (3) increased cultivation leads to heightened phosphate levels, indicative of agricultural runoff and potential high fertiliser usage, while the expansion of mining activities results in elevated concentrations of sulphate and Total Dissolved Solids (TDS), attributed to the discharge of mine effluents; (4) noticeable declines in the concentrations of TDS and sulphate are evident in the medium to long term when compared to the baseline simulations. However, the worst-case scenario (i.e., a 70% abstraction increase) exhibits elevated peaks and concentrations compared to scenarios with more probable demand increases (e.g., a 5% increase). , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
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  • Date Issued: 2024-10-11

Moral disgust in Klaus Mann’s Mephisto and Goethe’s Faust

  • Authors: Neilson, Christopher John
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/465934 , vital:76669
  • Description: This thesis investigates the presence and effects of moral emotions within Klaus Mann’s Mephisto (1936) and Goethe’s Faust (1808) with a focus on moral disgust as understood through the theories of P. Rozin and J. Haidt. The thesis also investigates the intertextual links between Goethe’s Faust and Klaus Mann’s Mephisto, namely the presence of the katabasis and anabasis motifs found in classical literature. This is undertaken with the aim to highlight the use of moral emotions as a novel approach to the study of literature. The Faust legend features an important moment when the Faust figure enters into a deal with the devil in hopes of gaining some transitory reward in exchange for his soul, with Goethe’s Faust being the most popular rendition of the German Faust legend. It is a play that depicts the life of a restless scholar who enters into a pact with a demon named Mephistopheles in the promise that Faust will receive pleasure without satisfaction. Shortly after the National Socialists came into power in Germany in 1933, Klaus Mann would write his own interpretation of the Faust motif in response to the Nazi reign. Klaus Mann’s Mephisto details the meteoric rise of the stage-actor Hendrik Höfgen who makes a ‘deal with the devil’ by collaborating with the Nazi elite in order to further his own acting career. Mephisto is devoid of any supernatural elements; this thus removes any supernatural influence on the actions of the Nazis and the protagonist Höfgen. The moral emotion of disgust, and thus also self-directed disgust and self-knowledge, eventually saves Faust, but there is no divine force to redeem Höfgen, nor is there an actual devil or demon to blame. , Thesis (MA) -- Faculty of Humanities, Languages and Literatures, 2024
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  • Date Issued: 2024-10-11

Music in everyday life: an exploration into the various uses of music among restaurant servers in Makhanda

  • Authors: Dlamini, Andile Sakhile
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/466161 , vital:76702
  • Description: Inspired by the theory of practice in everyday life and symbolic interactionist perspectives, this thesis offers an account and analysis of findings from a qualitative study. It aimed to investigate the everyday uses of music among restaurant servers (individuals) in Makhanda, on an intra-level of analysis. It explored music’s role in individuals’ lives, and how music as an art is influential in constructing their individuality or self in society. Ten in-depth interviews were conducted through face-to-face collaboration and an audio recording device. It was evident that music plays various roles in people’s lives. Music, seemingly intertwined with everyday life permits individuals to diversly use music, for instance with tackling their emotions and mood, as an accompaniment to tasks or even a symbol that serves subjective meaning to self, essentially transforming the routinized mundanity of every day. , Thesis (MSocSci) -- Faculty of Humanities, Sociology, 2024
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  • Date Issued: 2024-10-11

Navigating change: a critical analysis of social media’s role in shaping gender activists’ perspectives

  • Authors: Dias, Sasha Elliot
  • Date: 2024-10-11
  • Subjects: Social media and society , Sexual minority activists South Africa , Political activism , Gender digital divide , Harassment , Cyberfeminism
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/466128 , vital:76699
  • Description: This research explores the unique challenges and opportunities that social media offers gender activists fighting for equality and social justice. It examines the negative and positive elements of social media, highlighting the ways it can be adopted to build communities, amplify voices, and advance social change in unique ways, but also the ways in which it can adversely contribute to existing power imbalances and inequalities. This research does not concentrate on any specific gender-based movement, but rather aims to understand how gender activists in South Africa have embraced social media in their local activism. The study followed a qualitative approach and collected the data through in-depth semi-structured interviews. It also followed a thematic framework in its analysis of the data collected from the interviews. The study found that, while online gender activism in South Africa faces challenges such as harassment and the digital gender divide, there is still progress in terms of community building and political engagement on social media. The findings suggest that, in spite of the challenges, social media can still be an important tool for advancing gender-based social justice in South Africa. This research made use of Counter-publics and Cyberfeminism as guiding theoretical frameworks. The theory of Counter-publics provides a valuable way of understanding how virtual groups emerge and challenge dominant societal norms and values. Cyberfeminism provides insight into how women have challenged contemporary inequalities through the adoption of technologies such as social media. As sub-components to Cyber-feminism, Intersectionality and Standpoint perspectives were used to understand how activists’ diverse identities and social positions influence their individual forms of activism. , Thesis (MSocSci) -- Faculty of Humanities, Sociology, 2024
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  • Date Issued: 2024-10-11

No way to escape: a crime fiction

  • Authors: Dzanibe, Nkosivumile
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/465923 , vital:76668
  • Description: This study presents a model for science engagement that incorporates journalistic approaches. This model emerges from a project that aimed to create engagement and communication around a genetically modified sugar cane variety, developed by the South African Sugarcane Research Institute (SASRI). In this project, we engaged with small scale growers in the North and South Coast region of KwaZulu-Natal. This study’s methodology is based in action research and an iterative approach to science communication and engagement. It draws and reflects on an action research cycle captured through video documentary as a way to effectively and thoroughly collect, analyse and interpret data and produce through the case study. Based on this action research process a model for science engagement is proposed and reflected on and interrogated by scientists and science communicators through a focus group engagement (see model here as part of this thesis): https://drive.google.com/file/d/14UD1qd4fPcqIZrkESq5v2wgJ1Y2Q7hON/view?usp=sharing. I reflect, using video, on this model and how it incorporates principles and techniques for public engagement drawn from different approaches to journalism and communication studies, I argue that science engagement can benefit from drawing from journalistic approaches to public engagement such as those emerging from development communication, public journalism and development journalism. The submission of this thesis includes various other videos as part of the overall thesis. , Thesis (MA) -- Faculty of Humanities, Languages and Literatures, 2024
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  • Date Issued: 2024-10-11

Optimising Integrated Multitrophic Aquaculture (IMTA) on a South African abalone farm

  • Authors: Falade, Abiodun Emmanuel
  • Date: 2024-10-11
  • Subjects: Aquaculture , Integrated multi-trophic aquaculture , Seaweed , Abalone culture South Africa , Abalones , Ingestion , Nutrient cycles
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466712 , vital:76772 , DOI https://doi.org/10.21504/10962/466712
  • Description: The efficiency of fed nutrient utilisation in integrated multitrophic aquaculture (IMTA) system was evaluated on a South African abalone farm. On many commercial abalone farms in South Africa, Haliotis midae are fed a combination of pelleted feed and live macroalgae cultured downstream in abalone effluent. This production technique reduces the discharge of dissolved nutrients into the environment and improves farm productivity as unquantified proportion of the waste metabolites is captured as macroalgal biomass. However, the solid waste from abalone culture tanks remains unutilised and discharged to the coastal environments. Thus, there is scope to improve the dissolved nutrients removal efficiency of the macroalgae and to reduce the discharge of particulate nutrients using detritus waste extractive organisms. The present study aimed at the production and environmental performance of a shore-based abalone/macroalgae IMTA improving farm in South Africa by improving the nutrient utilisation efficiency of farmed abalone and seaweed and testing the waste solids removal potential of a sea cucumber species. Monoculture systems, where abalone and seaweed were cultured separately, both in fresh seawater (salinity: 35 g/L), were compared with an integrated culture system where the seaweed (Ulva lacinulata) was cultured downstream in the wastewater flowing from abalone tanks that were up-channel. Based on the findings from quantifying the performance of these production systems, methods to improve the nutrient utilisation and production efficiencies of the production systems were explored. These assessed methods included (1) the removal of abalone biodeposits by detritus extractive sea cucumber production, (2) evaluating the potential of farmed macroalgae as supplement in formulated diet, and (3) replacing mineral fertilisers with eco-friendly live microbial fertilisers for seaweed farming. Furthermore, the overall environmental performance of the two farm systems was quantified using a life cycle analysis methodology. Monitoring of the nutrient flows through the monoculture and IMTA systems revealed that the highest inputs of nutrients (nitrogen and phosphorus) into the abalone and seaweed culture tanks of the two production systems were abalone feed pellet (70-81%) and mineral fertilisers respectively (63-93%). About 48-51% of the nitrogen supplied from the feed was utilised by abalone in the IMTA and monoculture systems, while the remaining portion was lost as organic waste nitrogen on the production tank floor (20-30%) and as dissolved nitrogen in post-abalone tank effluent (30-36%). In the seaweed tanks receiving abalone effluent (IMTA), 69% of the dissolved nitrogen input was absorbed by cultured Ulva while 25% of the nitrogen was lost to the post-seaweed effluent which returned to the environment. However, in the monoculture system, 52% of the nitrogen from supplemented inorganic fertiliser was absorbed by cultured Ulva while ca. 46% of the nutrient was lost to coastal waters through the post-seaweed effluent. Moreover, while the feed accounted for ca. 74-78% input of the phosphorus in abalone of the two production systems, not more than 19% and 13% of this phosphorus was utilised by H. midae in the IMTA and monoculture systems respectively, while the largest portions were lost as organic waste in the sediment (34-45%) and dissolved waste phosphorus in the effluent (33-54%). In the seaweed tanks, a small portion (11-15%) of supplied phosphorus was removed by farmed Ulva while 77-89% was lost in the post-seaweed effluent discharged to coastal environment. The substitution of 50% mineral fertilisers with live microbial fertilisers during seaweed production significantly reduced the discharge of dissolved nitrogen and phosphorus from macroalgae raceways to coastal environment by 55 and 45% respectively, without impacting their growth, yield and nutrient compositions. A life cycle analysis of the measured energy and nutrients utilisation efficiency of these production systems was compiled, and the impacts of the inputs and outputs from each production system on the environment was assessed. The electrical energy input to abalone and seaweed tanks constituted the highest contribution to all assessed environmental impact categories for the two production systems, followed by the contributions from the nutrients supplied to farmed abalone (formulated diet) and seaweed (mineral fertilisers). The impact of these inputs on the environment was most evident on marine aquatic ecotoxicity being 2.11E+03 kg 1.4-DB eq and 4.43E+03 kg 1.4-DB eq for IMTA and monoculture systems respectively. The measured impact of seaweed aquaculture on the environment was reduced by 50-52% when Ulva was cultured in abalone effluent (IMTA) compared to culture in fresh seawater (monoculture). However, the input of chemical fertilisers in the two systems of cultivation resulted in similar eutrophication potentials (8.09 - 8.41E-02 kg PO4--- eq). To reduce the solid waste discharge from abalone tanks, and create an additional high-value crop, an endemic sea cucumber species (Neostichopus grammatus) was introduced on the floor of the abalone culture tanks in a pilot abalone/detritivore/macroalgae IMTA system. The sea cucumber utilised the biodeposits in abalone tanks as food which reduced organic solid discharge to the environment by 11%. However, the sea cucumbers displayed poor nutrient utilisation, a negative growth rate (- 0.59% day-1) and 49% weight loss by the end of the trial that was probably due to sub-optimal habitat conditions (lack of a sand substrate). The potential of including farmed Ulva (IMTA and monoculture) meal in pelleted feed for H. midae was evaluated as a means of improving farming efficiency and reducing the levels of fishmeal and soya in the pellet. In an initial trial, Ulva was included at 12% dry weight in commercial diet and fed to farmed H. midae for 244 d. The 12% inclusion of IMTA and monoculture Ulva resulted in poor feed conversion and nutrient utilisation by H. midae. In a follow-up trial which tested graded inclusion levels of Ulva meal (0.75, 1.50, 3.00, 6.00 and 12.00%), the growth rate and feed utilisation of H. midae was enhanced at a 0.75-6.00% inclusion level of the seaweed in the diet, while at a 6.00-12.00% inclusion level growth rates and feed conversion efficiencies decreased. Therefore, it is recommended that for sub-adult South African abalone, up to 6.00% IMTA Ulva meal can be included in the diet formulation without impacting their growth performance and nutrient utilisation efficiency negatively. This present study contributes to the understanding of the nutrient utilisation dynamics on integrated abalone farms in South Africa. The evidence from the different trials suggests the IMTA techniques tested could be adopted to improve the production performance and reduce the impact of abalone farming on the environment. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
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  • Date Issued: 2024-10-11

Participatory mapping of key drivers of ecological change and analysing equity dimensions of ecosystem services flow in the Kat River Catchment

  • Authors: Seriki, Esther Ahuoiza
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/465024 , vital:76566
  • Description: Rivers are important ecosystems which supply ecosystem services critical to social-economic well-being. However, many rivers are degraded due to human activities. Degradation of river systems compromises the quality and quantity of ecosystem services they can supply. Managing important drivers of ecological change requires broad-based stakeholder participation to mobilise collective actions for an effective rehabilitation strategy. This study looked at two crucial research objectives in the Kat River catchment. The first was to undertake a multidimensional, participatory, engaged mapping of ecological changes, as well as current and changing ecosystem services in the Kat River catchment, and the second was to analyse the equity dimensions of ecosystem services flow in the Kat River catchment. Data were collected through semi-structured interviews and participatory GIS mapping exercises. A purposive sampling method was applied to recruit research participants for interviews and workshops. Between March 13th and May 31st, 2023, thirty-one (31) participants representing four social groups, non-farming individuals, catchment management forum members, commercial and subsistence farmers, participated in interviews. Additionally, twenty-two (22) stakeholders attended 2-day workshops held between 20−21 April 2022, and 30−31 May 2023. Data collected from interviews and workshops were analysed using thematic analysis. The results of stakeholder perceptions regarding the perceived ecological changes and their key drivers in the Kat River catchment revealed a concerning trend. Participants reported significant changes to the catchment area over time, including increased occurrences of flooding and water pollution and decreased aquatic biodiversity. Furthermore, degradation of ecosystem services, such as water quality, availability of medicinal plants, reeds, and fish populations, was noted. These environmental shifts have been accompanied by a rise in social-economic burdens, including the prevalence of water-borne diseases, cultural burdens (particularly the inability of certain groups to access ancestral grave sites) and declining fish populations. These findings emphasise the urgent need for intervention strategies to mitigate further degradation of the catchment area and safeguard the well-being of both the human population and the integrity of the ecosystems. Recommended intervention measures include improving wastewater management practices and creating targeted public awareness campaigns. By addressing these challenges, stakeholders can work towards preserving the integrity of the catchment area, protecting water resources and conserving biodiversity for future generations. The equity dimensions (distributive and procedural equity) analysis revealed notable disparities in access to the benefits of ecosystem services, as well as in participation of residents in the Kat River Water Users Association. Certain social groups, such as commercial farmers, were observed to receive more benefits from ecosystem services, while other groups, including the elderly and disabled individuals, seem to be negatively impacted by the activities of those who benefit most from ecosystem services in the Kat River catchment. This raises not only an equity issue but also the issue of how costs are externalised by certain groups. Of particular concern was the finding that seventy (70) per cent of the research participants were not aware of the presence of the Kat River Water Users Association, raising concerns about procedural equity in water resource management processes. Additionally, ninety (90) per cent of the participants had the perception that there was unfair water access and allocation across the various social groups, highlighting possible distributive inequities. The participants expressed a clear interest in learning more about the existence and operation of the Kat River Water Users Association, signalling a need for increased awareness and participation among social groups. Addressing these equity concerns is crucial to ensure that water resource management processes are designed to provide all stakeholders and water-dependent actors with equitable and fair access to decision making. Moving forward, efforts should be directed towards raising awareness of the Kat River Water Users Association and to promoting inclusive participation among all social groups. This awareness may involve targeted outreach campaigns, community engagement initiatives and policy reforms to foster more equitable water governance practices within the catchment. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
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  • Date Issued: 2024-10-11

Perceptions, knowledge, and attitudes towards employee wellness programmes among private high school educators in South Africa

  • Authors: Moroane, Motheo
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/464765 , vital:76543
  • Description: Organisations can perform more effectively if their employees' health and wellbeing are optimal and considered a priority. Evidence suggests that employee wellness programmes (EWP) increase employee and overall organisational health, effectiveness, and performance. The World Competitive Report has ranked South Africa poorly regarding Human Resource Management and Development. The South African education system accommodates more than 12,3 million high school learners, 2 938 primary and secondary schools and only 37 500 educators. The South African Department of Education has implemented several initiatives to improve education and the wellbeing of South African educators. However, research investigating the work-related health and wellbeing of educators indicates that burnout, job dissatisfaction, depression, anxiety, and infections, including HIV and AIDS, TB, and Malaria, are prominent among educators. The objectives of this research were to explore whether age, sex, education, and years employed as an educator will significantly impact South African private high school educators' (i) perceptions, (ii) knowledge and (iii) attitudes toward employee wellness programmes, and to (iv) using the answers from a questionnaire; to propose a normative holistic employee wellness programme for private high school educators in South Africa. To fulfil these objectives a mixed-methods study approach was adopted. The study used a once-off, specifically designed questionnaire that explored EWP perceptions, knowledge, and attitudes among South African private high school educators. The results of the questionnaire indicated that firstly, the highest education obtained significantly influenced how educators rated their knowledge of employee wellness programmes. Specifically, the higher the level of education/more educated educators were, the better employees rated their knowledge of wellness programmes. Secondly, gender emerged as a significant factor. Female educators were more inclined to better rate their perception and knowledge regarding whether the workplace could provide valuable source of information on employee health and wellbeing. In other words, female educators rated their knowledge and perceived the workplace as a potentially valuable source of information on employee wellness programmes, than men did. Thirdly, educators with more than ten years of experience were more likely to participate in employee wellness programmes. Lastly, younger employees (younger than the age of 41 years) had the attitude that stigmas may prevent employees from participating in employee wellness programmes and seeking counselling, testing and treatment. Based on these findings, a tailored holistic EWP model was developed to address the specific needs of private high school educators, aiming to enhance their overall wellbeing. In conclusion, this dissertation emphasized the importance of EWP in improving the health and performance of educators in South Africa’s private high schools. Importantly, this study identified unique challenges faced by these educators and highlighted the need for tailored wellness initiatives. Lastly, this study emphasizes the importance of addressing educator wellbeing to enhance the overall educational environment in South Africa. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2024
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  • Date Issued: 2024-10-11
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