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Synthesis, characterization and host-guest complexes of supramolecular assemblies based on calixarenes and cucurbiturils
Get PDFThe field of supramolecular chemistry has grown large and wide in both deepness of understanding, range of topics covered and scope and applications. Supramolecular self-assemblies are facilitated by a wide range of non-covalent intra and inter molecular interactions that range from hydrogen bonding to π-interaction and van der Waals. Macrocyclic compounds such as cucurbiturils and calixarenes have emerged as important classes of compounds with excellent potential of forming supramolecular assemblies. The porous nature of these compounds enables them to form host-guest supramolecular complexes stabilized by diverse range of non-covalent interactions. Furthermore, these compounds contain donor atoms capable of forming bonds with metal ions to yield metal complexes with interesting porous characteristics that deviate from their traditional hydrophobic cavity. The versatile nature of the resulting pores imply that they can accommodate diverse types of guests. This work explores the synthesis and characterization of a host of calixarenes and cucurbiturils. Self-assembly of these macrocycles with various metal ions results to the formation of porous metal organic framework (MOF) complexes. Four new calixarene typed compounds obtained from aromatic aldehydes and twenty-six cucurbituril metal complexes are reported. These macrocylces and their metal complexes also form supramolecular complexes with DMSO, methanol, isoniazid hydrochloride and ciprofloxacin hydrochlorides through either self-assembly, mechanochemistry and exposure to solvent vapors. The bulk materials have been characterized using nuclear magnetic resonance spectroscopy (NMR), Fourier transformed infrared spectroscopy (FTIR), powder and single crystal diffraction techniques and thermal studies thermogravimetric analysis (TGA) and differential thermal calorimetry (DSC). Data obtained from this study reveals that calixarenes can form supramolecular complexes with a frequently used laboratory solvents with BN22 showing appreciable selectivity for DMSO sorption from a solvent mixture. These compounds also form supramolecular complexes with drug molecules such as isoniazid and ciprofloxacin. Furthermore, the data reveals that choice of synthetic route of supramolecular ensembles dictates if the guest drug molecule will occupy the intrinsic or extrinsic pores of cucurbituril complexes. Biological studies on the obtained complexes reveal that the cucurbituril complexes are non-cytotoxic while the calixarenes show antibacterial activity against Escherichia coli and Staphylococcus aureus. Additionally, the study showed that ciprofloxacin can be successfully released from a calixarene host in a simulated body fluid although the host was also found to cross the dialysis membrane. The results of this study are important in that; - they can be exploited and developed in the selective sorption of certain guests and - that they can be used in the development of drug delivery systems that play a dual role of delivery and therapeutic activity.Thesis (PhD) -- Faculty of Science, Chemistry, 202
Development of biosensor systems for the detection of anti-cancer drugs and prostate cancer
No full textThesis embargoed. Expected release date early 2025.Thesis (PhD) -- Faculty of Science, Chemistry, 202
Leveraging LTSP to deploy a sustainable e-infrastructure for poor communities in South Africa
Get PDFPoverty alleviation is one of the main challenges the South African government is facing. Information and knowledge are key strategic resources for both social and economic development, and nowadays they most often rely on Information and Communication Technologies (ICTs). Poor communities have limited or no access to functioning e-infrastructure, which underpins ICT. The Siyakhula Living Lab (SLL) is a joint project between the universities of Rhodes and Fort Hare that has been running for over 15 years now. The SLL solution is currently implemented in schools in the Eastern Cape’s Dwesa-Mbhashe municipality as well as schools in Makhanda (formerly Grahamstown). Over the years, a number of blueprints for the meaningful connection of poor communities was developed. The research reported in this thesis sought to review and improve the Siyakhula Living Lab (SLL) blueprint regarding fixed computing infrastructure (as opposed to networking and applications). The review confirmed the viability of the GNU/Linux Terminal Server Project (LTSP) based computing infrastructure deployed in schools to serve the surrounding community. In 2019 LTSP was redesigned and rewritten to improve on the previous version. Amongst other improvements, LTSP19+ has a smaller memory footprint and supports a graphical way to prepare and maintain the client’s image using virtual machines. These improvements increase the potential life of ICT projects implementing the SLL solution, increasing the participation of members of the community (especially teachers) to the maintenance of the computing installations. The review recommends the switching from thin clients deployments to full ("thick") clients deployments, still booting from the network and mounting their file systems on a central server. The switch is motivated by reasons that go from cost-effectiveness to the ability to survive the sudden unavailability of the central server. From experience in the previous deployment, electrical power surge protection should be mandatory. Also, UPS to protect the file system of the central server should be configured to start the shutdown immediately on electrical power loss in order to protect the life of the UPS battery (and make it possible to use cheaper UPS that report only on network power loss). The research study contributed to one real-life computing infrastructure deployment in the Ntsika school in Makhanda and one re-deployment in the Ngwane school in the Dwesa-Mbhashe area. For about two years, the research also supported continuous maintenance for the Ntsika, Ngwane and Mpume schools.Thesis (MSc) -- Faculty of Science, Computer Science, 202
The regeneration of palmiet (prionium serratum) following hydrogeomorphic disturbance: a case study of the Kromme River wetland
Get PDFThe Kromme River wetland in the Eastern Cape of South Africa occupies a broad valley (up to 350 m wide) with a gentle longitudinal slope of less than 2 % that has been formed by cut-and-fill cycles that are initiated by trunk-tributary interactions. These hydrogeomorphic disturbance events trigger gully erosion and generate sediments, the coarse fraction of which is deposited less than 2 km downstream, leading to depositional floodout features that fill gullies headwards. This process has been occurring at intervals for at least 10 000 years, and as such pre-dates the introduction of European farming practices in the area. Plants that regenerate by colonising these features are thought to have evolved adaptions necessary to colonise intermittently produced bare sandy sediments. This study aimed to examine the regeneration ecology of palmiet (Prionium serratum), the dominant vegetation community within these cut-and-fill wetlands, by relating its regeneration characteristics to environmental factors in a reach of the Kromme River wetland that has experienced a recent hydrogeomorphic disturbance event (approximately 10 years before the commencement of this study). Palmiet was found to be regenerating on sedimentary deposits on beds of gullies and on depositional bars on the margins of gully beds. The large depositional floodout downstream of a large gully also favoured palmiet regeneration, where it was found to be regenerating along not only the active channel, but also along old abandoned flow paths and sometimes areas well elevated above the channel. The geomorphic features that favoured palmiet regeneration were characterised by coarse-grained sediments (mean particle size approximately 310 μm) with low organic matter content (0.61 %), a low depth to the water table and low elevation above the thalweg (mean depth to water table is approximately 0.6 m), and a relatively close distance to the thalweg (< 10 m). This understanding of palmiet’s regeneration characteristics was viewed in relation to existing literature on undisturbed palmiet wetland plant communities and its reported contribution to conditions that favour wetland formation through gully filling, which allowed for the creation of a conceptual model of palmiet regeneration, colonisation and long-term persistence. This model was based on the Fluvial Biogeomorphic Succession concept. It suggests that palmiet’s interaction with the hydrogeomorphic environment throughout the different stages of its life cycle results in self-organising biogeomorphic landforms. Over hundreds of years, the reciprocal interactions between palmiet, sediments and water, fills gullies and restores valley bottoms, ultimately leading to the formation of a wetland landform. It is further proposed that through continued accretion, the geomorphic wetland landscape becomes more and more disconnected from the hydrogeomorphic dynamics of the fluvial system, such that the prevailing conditions begin to favour fynbos establishment, which may outcompete palmiet.Thesis (MSc) -- Faculty of Science, Geography, 202
The reported prevalence of aircrew fatigue and the contributing factors within the South African aviation industry
Get PDFFatigue in aviation results from the complex interaction of various factors (both work and non-work-related) that are important to understand when attempting to manage it. Managing fatigue effectively is important given that it has and continues to influence crew wellness and aviation safety. One of the ways of managing fatigue is through appropriately designed Flight Time Limitations (FTLs) however; in South Africa there have been calls from the unions and the crew to update these in line with the latest science and operational demands and insights. Doing this requires the generation of context specific data, which this thesis aimed to provide as an initial step. Firstly, this study aimed to explore the reported prevalence of fatigue across the South African aviation industry. Secondly, it elucidated what factors (both work and non-work related) crew perceived contributed to fatigue and lastly, the crew‟s perceptions regarding the current FTLs were explored. Methods: To realize the aims of the study, an online survey was developed using existing literature initially, and through consulting with and getting information from aviation industry stakeholders and other experts in the field of aviation and fatigue. This consultation (which occurred over a number of iterations of the survey) ensured that there was a balance between the scientific and the actual operational perspectives on how best to explore crew perceptions around fatigue. The finalized survey was divided into five parts: part one was consent to participate; part two included questions pertaining to the participants‟ demographic information; part three included questions pertaining to the crews‟ perceptions around fatigue (its prevalence, its impact on safety and how it affected crew); part four explored crew‟s perceptions on fatigue contributory factors, both work and non-work related; finally part five included questions pertaining to crew perceptions about the current South African FTLs, specifically their concerns, suggestions for improvement and any aspects they considered as fatigue mitigating. The survey was made available via the South African Civil Aviation Authority‟s (SACAA) website as well as via the industry stakeholder‟s networks that encouraged all crew across the different sectors of the industry to participate. All numerical data collected were analysed descriptively through inferential statistics, while the qualitative data were analysed using thematic analysis. Results: 194 participants completed the survey, 167 were from cockpit and 27 were from the cabin crew. The results of the study highlight that there is a high perceived prevalence of fatigue. The crew also recognized that fatigue is a significant safety risk, but less indicated that fatigue interfered with their ability to do their duties. Crew reported that the length of duties, number of sectors flown, insufficient sleep at night, early sign-on‟s, late sign-offs, working too many consecutive days in a row, inadequate or irregular sleep before and during periods of duty, night flying, bad weather, severe turbulence, having young children or dependents to look after, financial stress, extended commuting to get to and from work, and poor diet were some of the work and non-work-related contributory factors to fatigue. In line with these findings, questions around the perceived concerns about the current FTLs revealed that crew were concerned about unclear definitions of the civil aviation regulations (CARs), the lack of control of disruptive rostering schedules, periods of high workload due to the number of sectors flown per duty, the length of duty periods and effects of being on standby duty, inadequate rest between duties and strings of duty. The crew also had concerns regarding the Flight Duty Periods (FDPs) where the crew were concerned with the flying limits being used as targets by the operators, a lack of science applied to the FDPs, and that the current FDPs are outdated. The recommendations included limiting disruptive rostering schedules by altering standby provisions for the crew, instilling a block roster schedule, disallowing double signing on and off on the same day, and reducing split shifts. The crew also recommended adjusting duty durations by adjusting daily and monthly limits, tapering duty lengths, but also limiting discretionary extensions. Increasing rest provision was another recommendation suggested by the crew and included increasing the number of rest days off as well as the minimum hours of rest between duties needs to be increased. The fatigue mitigating aspects were minimal if any. Conclusion: Overall the study revealed that there is a high perceived prevalence of fatigue within this sample of the South African aviation industry and that the concerns outlined by crew around the contributory factors to fatigue are consistent with previous research, but also reflect the unique operating context of South Africa. This study serves as a base from which to explore more specific areas of the crew working time that are disruptive to sleep. This may help operator‟s roster duties in a more predictable way to limit the incidence of fatigue, while also offering the opportunity for the regulator and other stakeholders to focus their efforts on how to better design the current FTLs to limit the prevalence and risks associated with crew fatigue.Thesis (MSc) -- Human Kinetics and Ergonomics, 202
Implementing mathematics intervention strategies to enhance understanding of number sense: an informative framework for the Ekurhuleni North District, Gauteng province, South Africa
Get PDFThis study was prompted by the observation that learners’ performance in mathematics is low in South Africa. Several factors such as teachers’ qualifications, demotivated learners, and limited school resources have been raised and considered. Although number sense forms the foundation blocks for mathematics understanding, limited academic work has been done to explore implementable mathematics instructional interventions for the enhancement of understanding number sense. The purpose of this study was to contribute an implementable mathematics intervention framework for understanding number sense. Since the study focused on exploring intervention activities, it was guided by the pragmatism research philosophy. Data were captured from purposive samples of teachers and stratified samples of 1050 learners from schools in the Ekurhuleni North district in South Africa. The research design comprises the following sequence: survey, pre-test, intervention, post-test, and evaluation by teachers’ focus group discussion. These activities were carried out parallel to document analysis, which provided bench marks. The main data-capturing instruments were the questionnaires, learners’ test, interview, and document analysis guides. Factors analysis to establish associations, differences, and regression was carried out using SPSS and Excel. The study found that: almost all teachers implemented some form of mathematics interventions. Continuous assessment was the main intervention, followed by problem-solving, and the use of games (which was least preferred). Teachers shunned games because they require more time and management skills. Challenges that teachers experienced when implementing mathematics interventions include their limited knowledge and the lack of resources and support from education authorities who expect and emphasise high pass rates in mathematics. The teachers’ focus group discussions evaluated the intervention and proposed the following sequence for instructional intervention on number sense: Stage 1: parroting of number names, for example, six, two, nine and seven Stage 2: symbolic identification, for example, the symbol 6, 2, 9 and 7 Stage 3: association where a learner group six stones, shows two fingers, etc. Stage 4: seriating or ordering done through oral counting and use of inequality symbols: () to compare and estimate values in problems Stage 5: the four operations for addition (+), subtraction (-), multiplication (x) and division (÷) emphasizing estimation and application. The study recommends the adoption, modification and implementation of mathematics intervention framework to enhance number sense.Thesis (MEd) -- Faculty of Education, 202
Suitably Strange: Re-imagining learning, scholar-activism, and justice
Get PDFUsing artworks emergent from my career as a pracademic and scholar activist, I attempt to share a ‘tactile theory’ of being and doing, that refer mainly to response-abilities (i.e., abilities to respond in accountable ways) in scholar activist educational sociology. I aim to make visible (and tactile) the sometimes-invisible qualities and practices needed for navigating the eroded and dying ecological relations of our generation, as well as warming up and making pliable the heteronormative, capitalist, patriarchal and anthropocentric conventions that are associated with it. In order to warm and sculpt these normative conventions, I argue for the need for ‘suitably strange’ practice. I present six images and associated prose that aim to optimally disrupt these conventions, towards generative rethinking and embodying learning, scholar activism and justice, and from which I explore a tactile theory, an example and related response-ability for each. I end with a reflection of how these suitably strange artefacts can help us develop a new concept of proactive-cognitive justice or ‘justness’
Land degradation and livelihood strategies in rural Zimbabwe: the case of two A1 farms in Shurugwi District
Get PDFLand degradation is a global phenomenon which is having serious negative consequences for rural livelihoods, which depend quite fundamentally on land and its resources. At the same time, one of the key conditions contributing to land degradation relates to rural livelihood practices, insofar as these practices fail to protect the land. Hence, there sometimes exists a mutually-reinforcing process of decline, in relation to both land vitality and livelihoods vitality over time. This thesis seeks to investigate and understand this complex land-livelihoods process through a case study of two fast track farms in the Shurugwi District of contemporary Zimbabwe. In the year 2000, the Zimbabwean government introduced the fast track land reform programme which fundamentally reconfigured the rural landscape. In particular, it led to the formation of A1 farms (containing small-scale farming units called A1 plots), onto which people were resettled for purposes of enhancing their livelihoods. The case study focuses on two A1 farms in the district, namely, Selukwe Peak and Adare farms. Through a longitudinal study of land and livelihoods on these A1 farms, this study seeks to identify the multi-faceted character of land degradation on the farms, the multi-layered conditions (or causes) facilitating land degradation (specifically, the farm-based livelihood practices) and the effects of this land degradation on these very livelihood practices. This includes a focus on farmers’ understandings of land degradation and how these understandings may or may not condition livelihood practices on the two farms. Of particular importance is the presence of not only agricultural practices, but also high levels of illegal and legal mining on the farms and in the surrounding areas. In pursuing this study, the thesis draws upon the Sustainable Livelihoods Approach alongside Margaret Archer’s morphogenetic sociological perspective. Combined, they provide an intricate understanding of the relevance of both structure and agency to the analysis. A qualitative methodology was used, and this involved a questionnaire survey, in- depth interviews, life histories, focus group discussions and transect walks. The study concludes that the livelihood strategies undertaken by the villagers of Selukwe Peak and Adare farms are key causes of land degradation, as are the land-degrading activities of illegal and legal miners. The A1 villagers are aware that their activities are causing land degradation but they continue these activities because they are pushed by circumstances beyond their control. Hence, both proximate and underlying causes are of some significance in understanding land degradation and livelihoods on the two farms, and their interrelationships.Thesis (PhD) -- Faculty of Humanities, Sociology, 202
Barriers to utilisation of antenatal care services in Bloemfontein, sub-district of Mangaung Metro, Free State, South Africa
Get PDFBackground: Maternal and child mortality remain a global health problem, regardless of preventative measures put in place. Antenatal care is crucial to decrease maternal and child morbidity and mortality. However, in Bloemfontein, the sub-district of Mangaung Metro in the Free State, it has been identified that women utilise this kind of service sub-optimally. The study aimed to explore and describe barriers to the utilisation of antenatal care by pregnant women in the Bloemfontein sub-district of Mangaung Metro. Methodology: This study was qualitative and used an explorative, descriptive design. Qualitative data was collected by using focus group discussions and key informants’ interviews. Three focus group discussions with twenty-five pregnant and lactating mothers, aged between 18 and 49 years, were conducted. Participants took part in one focus group discussion at each healthcare facility. Four key informant interviews were conducted with four facility managers and one professional midwife who conducted ANC at the clinic at the time of the study in the three healthcare facilities. A thematic analysis process was used to analyse the collected qualitative data under each identified barrier. The STATA version 15 was used in the analysis of the demographic characteristics of the participants. Results: Most of the participants indicated that they are aware of the importance of attending ANC appointments however, they have voiced that the delayed waiting times and staff attitudes contribute to how they feel about visiting a clinic early. Some of the participants mentioned that they have cultural barriers as they still believe that a traditional pregnant woman should not reveal her pregnancy in the early days but must rather wait until her stomach has grown significantly for her to visit the clinic. Two participants indicated that they had unplanned pregnancies and wanted to do an abortion, but their religious beliefs prevented them to choose to terminate their pregnancies. Economically, not all participants complained about their financial situation though the majority were unemployed and single. Participants from the Bloemspruit facility complained of transport as they stay far from the clinic and they are sometimes forced to walk alone which makes it difficult to attend all their booked sessions with their midwives. The results of the study revealed that there are several factors contributing to late antenatal care attendance namely provider and personal factors contributing to late antenatal care attendance in the Bloemfontein sub-district of Mangaung Metro. Personal factors that were found to be contributing to late antenatal care booking were lack of transport, especially for Bloemspruit participants, unwanted pregnancy, lack of financial support, lack of partner support, cultural and religious beliefs, and lack of knowledge. Provider factors that were found to be contributing to late booking were lack of resources like tools of the trade, long waiting times, poor infrastructure, human resources, and midwives’ attitudes. Recommendations. To deploy qualified midwives to conduct antenatal care clinics, to extend the service over the weekends as participants mentioned that they struggle to get time off from work during the week. Health promotion and community awareness campaigns on the importance of antenatal care may increase the utilisation of antenatal care services.Thesis (MPA) -- Faculty of Health Sciences, 202
Backpack carriage and musculoskeletal pain among primary school learners in King Williams Town, South Africa
Get PDFBACKGROUND: There is rising concern that kids are walking to school with too much weight on their backs. The weight of schoolchildren's backpacks is a persistent and divisive topic in the fields of education and health. Children who carry heavy backpacks are more likely to have back discomfort and musculoskeletal pain, which raises their risk of developing chronic back pain as adults. There is little research on this topic among South African school-age youngsters. The goal of the study was to find out how common low back and other musculoskeletal complaints were among primary school students who used a school bag. RESEARCH AIM: The purpose of the study was to identify the prevalence and location of musculoskeletal discomfort in primary school students in King William's Town, South Africa, and describe their link with backpack use. METHOD: In King Williams Town, Eastern Cape, South Africa, a descriptive cross-sectional survey was conducted among elementary school students between the ages of 9 and 14 years old. A systematic questionnaire and the Cornell Musculoskeletal Questionnaire were used to gather the data (body chart). Age, gender, and schoolbag details (style of backpack, carrying technique, and carrying time) were collected. The learner's waist, hip, and bag circumferences were all measured. On the data, descriptive and interferential statistics were used. FINDINGS: The study's conclusions showed that students' musculoskeletal pain was brought on by the weight of their backpacks or school bags. The majority of the students (89.8percent) complain about the difficulty they experience when lugging their heavy backpacks to class. In addition, 83.4percent of the students had bags that weighed more than 10percent of their body weight. Additionally, a sizable percentage of students (89.8percent) carry a hefty bag to school every day and report feeling fatigued while doing so (90.8percent). 90percent of the students reported feeling discomfort before, during, or after carrying their schoolbags. This pain is related with carrying a schoolbag. The majority of students (53.5percent) felt that their daily pain interferes with their ability to study. In order of severity, the majority of students report having discomfort in their shoulders (82.7percent), lower back (59.9percent), neck (47.0percent), upper back (40.7percent), and upper arm (16.4percent). CONCLUSION: According to the study, there is a link between students' musculoskeletal pain and carrying hefty backpacks or school bags. The shoulders are where musculoskeletal discomfort is most frequently felt. The study supported the findings of the majority of studies cited in the literature that most schoolchildren suffer from musculoskeletal pain because the weight of their backpacks is excessive compared to their size, weight, and age. RECOMMENDATIONS: The study produced a number of recommendations, including that the Department of Basic Education inform teachers, students, parents, guardians, and other key stakeholders about the effects of heavy backpacks or schoolbags on students' musculoskeletal pain. For students' convenience and to lighten the load on their school bags, locker rooms should be available. Teachers, parents, and guardians should also pay attention to the school bags that students are using to make sure that the weight is appropriate for their age and body size.Thesis (MPA) -- Faculty of Health Sciences, 202