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Guidelines for improved coordination of public works projects in Buffalo City Metro

  • Authors: Puta, Mabhelonke
  • Date: 2024-04
  • Subjects: Public works -- South Africa , Infrastructure (Economics) -- South Africa , Economic development projects -- South Africa
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64775 , vital:73890
  • Description: This aim of this study was to determine how improved coordination of public works projects in Buffalo City Metro (BCM) can be promoted. The aim was predicated on the notion that coordination failure adversely affects scope, time, budget, and quality. A pragmatic worldview related to problem- solving informed the collection of both textual and statistical data for the study through surveys and interviews. In BCM public works projects failures in coordination have resulted in negative outcomes of project implementation. The study shows a correlation between coordination and project success, whilst failure in coordination will negatively impact project cost and project scope, resulting in project failure. The study was able to determine prioritised coordination activities. The study further developed coordination guidelines that mitigate coordination failure by outlining mechanisms, which are as follows: appointment of a coordination leader, scheduling coordination activities, participate plan and quality assurance plan. The outputs of these are the coordination of meetings, the online coordination of software, a schedule of lessons learnt, the drawing up of an execution plan and establishing performance incentives. , Thesis (MSc) -- Faculty of Engineering, the Built Environment and Technology, School of Built Environment and Civil Engineering, 2024
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  • Date Issued: 2024-04

Guidelines towards the use of virtual consultation in primary healthcare

  • Authors: Ndome Ndame, Evelyne Alexandra
  • Date: 2024-04
  • Subjects: Telecommunication in medicine , Medicine -- Communication systems , Health services administration -- Information technology
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64728 , vital:73872
  • Description: In an environment of expanding demand on the healthcare system to provide equitable, accessible, and safe healthcare, the use of information and communication technology (ICT) is one of the strategies identified to fulfil such expectations. To make this achievable, ICTs are integrated in healthcare using telehealth, which permits the provision of remote healthcare by using virtual health technologies. One domain of telehealth which permits remote care is virtual consultations. It is an important tool in the healthcare industry used to promote access to healthcare services, especially for elderly people or people with disabilities, those suffering from chronic diseases such as cardiovascular disease, diabetes, and hypertension, among others, and for people in rural and underserved communities. This is possible using videoconferencing technology, telephone consultations, email, or instant messaging. Virtual consultations are becoming an integral part of the healthcare industry all over the world, and it is important to understand how to make use of them to promote healthcare access. The purpose of this study was to create guidelines to assist primary health care professionals in the most effective ways of using virtual consultations to improve access to essential health care services. As such, the objectives governing this study were to identify the role that virtual consultations play in healthcare, to investigate the factors that impact the use of virtual consultations, to review the existing guidelines on virtual consultations, as well as to identify the requirements needed for virtual consultations. This research followed several aspects to guide the methodology of this study. The research process governing this research was the design science research process. The research made use of literature reviews, argumentation, and a survey for data collection as well as a qualitative content analysis to analyse the data. The data collection consisted of 32 survey responses, which aided in the identification of the factors impacting the use of virtual consultations. The results showed that virtual consultations are utilised for various aspects of care delivery, but face-to-face consultations are still the first choice of consultation. , Thesis (MIT) -- Faculty of Engineering, the Built Environment and Technology, School of Information Technology, 2024
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  • Date Issued: 2024-04

Herpetofaunal diversity and affiliations of the Okavango River Basin, with specific focus on the Angolan headwaters

  • Authors: Conradie, Werner
  • Date: 2024-04
  • Subjects: Water conservation -- Okavango River Delta , Watersheds -- Okavango River -- Angola , Biodiversity -- Angola
  • Language: English
  • Type: Doctorate theses , text
  • Identifier: http://hdl.handle.net/10948/63667 , vital:73576
  • Description: Although Africa is reputed to possess some of the richest herpetofaunal diversities in the world, a number of areas remain poorly documented and thus inadequately conserved. One such area in particular is the south-eastern part of Angola. Angola endured a long struggle for independence with a protracted civil war that lasted for nearly three decades, leaving the status of the country’s biodiversity in turmoil. Over the past two decades, Angola has become more accessible for biodiversity surveys, opening up new opportunities to document these previously poorly studied areas and help conserve its biodiversity. South-eastern Angola is the water source of the world-renowned Okavango Delta. However very little is known about the biodiversity, diversity status and conservation significance of the headwaters supplying the largest inland delta in the world. To address this bias in sampling and to investigate the conservation importance of the region, a series of rapid biodiversity surveys of the Angolan Okavango River Basin were conducted between 2012 and 2019. This study contributed over 2150 individual records of amphibians and reptiles, representing 88 reptile and 43 amphibian species. At least 15 species were added to the growing country checklist, with the south-eastern region of Angola now comprising 113 reptile species and 51 amphibian species. Because of this study, the area is now one of the most species-rich and well-studied areas in Angola. This study provided the first genetic data for 26 species, and sequences containing Angolan specimens for the first time were generated for 80 species, of which 23 species have originally been described from Angola. Maximum likelihood and Bayesian inference analyses, supported by species delimitation analyses, were utilised to validate specific species statuses. This allowed for the description of five new species of snake, one gecko and two frogs for Angola. The material further contributed to the description of a new genus of snakes. Numerous undescribed and potentially cryptic species were identified, long-lasting taxonomic issues were resolved, and various taxonomic adjustments were emphasised. Further contributions of the material include assisting in the revision of targeted Angolan amphibian and reptile groups as well as large-scale phylogenetic studies across Africa. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Science & Management, 2024
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  • Date Issued: 2024-04

IL-4/ IL-13 directed microglial activation and differentiation in response to LPS-induced neuroinflammation

  • Authors: Ackerdien, Shiraz
  • Date: 2024-04
  • Subjects: Inflammation , Inflammation -- Treatment , Anti-inflammatory agents
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/63606 , vital:73554
  • Description: Microglia activation is a common hallmark of neuroinflammation that occurs during pathogen invasion or lipopolysaccharide (LPS)-induced inflammation. A neuroinflammatory response is elicited by the release of proinflammatory cytokines which stimulates microglia in an autocrine manner to be polarized into classically activated, pro-inflammatory M1 cells. Prolonged exposure to the inflammatory response can have disastrous effects on the central nervous system (CNS). However, microglia can alternatively be polarized into the activated M2 anti-inflammatory phenotype, but the exact molecular mechanism mediating this phenotypic switch remains poorly understood. Studies have shown that interleukin (IL)-4 can induce the M2 phenotype and activate the signal transducer and activator of the transcription 6 (STAT6) signalling pathway that in turn provokes a beneficial Th2 immune response. Since IL-4 and IL-13 share a common IL-4 receptor alpha (IL-4Rα) chain, it is possible that alternative microglia differentiation and its anti-inflammatory action also involve IL-13. This study aimed to investigate how IL-13 and STAT6 signalling orchestrates the microglial response and differentiation associated with LPS-induced inflammation. Furthermore, the molecular mechanisms that relieve LPS-induced neuroinflammation and neural protection through IL-13-enhanced BDNF signalling were also investigated. C8-B4 microglial cells were induced with LPS to exhibit an M1 pro-inflammatory phenotype or stimulated with IL-4 and/or IL-13 to exhibit an M2 anti-inflammatory microglial phenotype. The cell viability following LPS, IL-4, and/ or IL-13 exposure was determined. The LPS-induced neuroinflammatory response and the anti-inflammatory response induced by IL-4 and IL-13 which promotes STAT-6 signalling were determined by measuring TNFα, IL-1β, and BDNF protein concentrations using ELISA assays. The polarising effects of LPS and IL-4/IL-13 cytokines were also examined via changes in the expression of Iba-1, CD206, CD86, and STAT-6 determined by immunofluorescence analysis. These changes were further investigated by quantifying the mRNA transcripts of TNFα, IL-1 β, Arg-1, CD206, IL-4R, and STAT-6 and BDNF using qRT-PCR. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
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  • Date Issued: 2024-04

Implementation of the world health organization surgical safety checklist in the operating room in a private hospital in the Nelson Mandela Bay Municipality

  • Authors: Obeng, Emelia
  • Date: 2024-04
  • Subjects: World Health Organization , Operating room nursing , Preoperative care
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/63517 , vital:73384
  • Description: The World Health Organisation Surgical Safety Checklist (WHO SSC) was developed to improve teamwork among healthcare professionals and ensure consistent use of safety processes in the operating room (Abbott et al., 2018: 147). The WHO SSC has successfully reduced common and avoidable surgical errors relating to nerve cutting, among others (Jain et al., 2018:7). However, the implementation of the WHO SSC has not been widely acknowledged in South Africa due to specific barriers (Koopman, 2018: 20; Sauls, 2019: 15). To this end, the aim of this study was two-fold: (i) to determine the factors that contribute to the implementation of the WHO SSC among operating room healthcare professionals and (ii) to develop a contextually appropriate process implementation guide that may be used to facilitate utilisation of the WHO SSC in a private operating room healthcare facility. A non-experimental descriptive quantitative approach underpinned by positivism and a descriptive exploratory survey was used to study the factors contributing to implementing the WHO SSC. A self-reported questionnaire was used as the method for data collection. Purposive sampling was adopted by selecting all the 130 operating room staff directly involved in completing the WHO SSC. All 130 respondents completed and returned the questionnaire. Data were analysed using the Statistical Package Software for the Social Sciences (SPSS) Version 28.0 for Windows (IBM Corp, 2021). The study described four factors (i.e. awareness, relative advantage, complexity, and usability) contributing to the implementation of the WHO SSC. The analysis revealed a significant inter-relationship between two factors (i.e. relative advantage and awareness) and characteristics of the operating room healthcare professionals (regarding highest qualification, current age and work experience). The study’s main contribution to the existing body of knowledge is the proposed process-oriented implementation guide, including a readiness assessment template for effective implementation of the WHO SSC. It is recommended that good knowledge of the WHO SSC should be created by making operating room healthcare professionals aware of the arrangements and interventions by the private hospital to implement the WHO SSC. , Thesis (MCur) -- Faculty of Health Sciences, School of Clinical care & medicinal sciences , 2024
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  • Date Issued: 2024-04

Incorporating emotion detection in text-dependent speaker authentication

  • Authors: van Rensburg, Ebenhaeser Otto Janse , Von Solms, Rossouw
  • Date: 2024-04
  • Subjects: Automatic speech recognition , Biometric identification , Computer networks -- Security measures , Computer networks -- Access control
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/64566 , vital:73767
  • Description: Biometric authentication allows a person to access sensitive information using unique physical characteristics. Voice, as a biometric authentication method, is gaining popularity due to its unique characteristics and widespread availability on smartphones and other devices. It offers a secure and user-friendly alternative to traditional password-based authentication and allows a less intrusive authentication method than fingerprint authentication. Furthermore, a vast amount of information is portrayed through voice, such as age, gender, health, and emotional state. Gaining illegitimate access to information becomes significantly more difficult as biometrics are difficult to steal, and countermeasures to techniques such as replay attacks are constantly being improved. However, illegitimate access can be gained by forcing a legitimate person to authenticate themselves through voice. This study investigates how the emotion(s) carried by voice can assist in detecting if authentication was performed under duress. Knowledge is contributed using a three-phased approach: information gathering, experimentation, and deliberation. The experimentation phase is further divided into three phases to extract data, implement findings, and assess the value of determining duress using voice. This phased approach to experimentation ensures minimal change in variables and allows the drawn conclusions to be relevant to each phase. The first phase examines datasets and classifiers; the second phase explores feature enhancement techniques and their impact; and the third phase discusses performance measurements and their value to emotion detection. , Thesis (DPhil) -- Faculty Of Engineering, the Built Environment and Technology, School of Information Technology, 2024
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  • Date Issued: 2024-04

Investigating the anti-inflammatory effect of blueberry-AuNP on microglial cells and obese rat brains

  • Authors: Ngwato, Anacia
  • Date: 2024-04
  • Subjects: Anti-inflammatory agents , Brain -- Anatomy , Brain -- Physiology
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64266 , vital:73670
  • Description: Nanotoxicology is a field of study that investigates how nanomaterials interact with biological systems. It focuses on understanding the correlation between the physicochemical properties of nanomaterials, such as size and stability, and their potential toxic effects. Gold nanoparticles (AuNPs), for instance, have a variety of applications in the biological sciences. Therefore, there is a great deal of attention given to evaluating their toxicity to ensure their safe and effective use in biological systems. Anti-inflammatory AuNPs have shown to be a desirable application in obesity treatments since obesity is associated with systematic inflammation. Thus, the study aimed to evaluate the anti-inflammatory effect of BE-AuNPs on C8-B4 microglial cell lines and, to validate the results, the grey matter of brain tissue of obese rats treated with BE-AuNPs. Following the synthesis and characterization of BE-AuNPs, C8-B4 microglial cells were treated with the BE-AuNPs and were evaluated through MTT, HRTEM imaging, qPCR, and ROS. LPS was used to activate the cells. Concentration-dependent toxicity of BE-AuNPs and cellular uptake was observed. The qPCR results showed that the BE-AuNPs decreased the LPS-induced inflammation in the cells. The BE-AuNPs were shown to reduce ROS in inflammatory conditions in the cells. Rat brain tissue analysis through qPCR and ROS demonstrated that BE-AuNPs reduce HFD-induced inflammation and had no ROS effects on the brain, respectively. Thus, leading to a conclusion the BE-AuNPs used in this study are anti-inflammatory. , Thesis (MSc) -- Faculty of Science, Biomolecular & Chemical Sciences, 2024
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  • Date Issued: 2024-04

Investigating ways to limit wasteful expenditure due to punitive property taxes on Gauteng hospitals

  • Authors: Molotsi, Obed Lucas
  • Date: 2024-04
  • Subjects: Real property tax -- South Africa -- Gauteng , Real property -- Valuation -- South Africa -- Gauteng , Finance, Public -- Law and legislation -- South Africa -- Gauteng , Financial management
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64705 , vital:73863
  • Description: The PFMA defines fruitless and wasteful expenditure as an expenditure made in vain, and it states that had reasonable care been exercised, such expenditure would and should have been avoided. Among the various forms of wasteful expenditure, the AGSA (AG, 2021) report lists the payment of penalties, or of interest accruing because of late or non-payments, and debt incurred. These expenditures are prevalent in social cluster infrastructure projects, and the waste is attributed to poor planning, weak internal control measures, and lack of oversight on contracts. The Local Municipal Property Act 6 of 2004 (SA Government, 2004) empowers municipalities to develop a land administration process to enforce compliance with land use management schemes, which often is referred to as the steps to be taken to avoid the illegal use of land. The illegal use of land arises when a property owner fails to comply with the provisions of the land scheme, and when the land owner fails to comply with the requirements set out in notices issued in terms of the land use scheme. Illegal land uses arise when property exchanges hands between government departments (vesting), resulting in a change of use. This then leads to a failure by the property owner to update the conditions and property information that should have been in line with the changes enacted in the land use schemes in the asset register. The objective of this research was to investigate ways and the process the Provincial Government of Gauteng should put in place to limit wasteful expenditure and the payment of administrative penalties, or mounting property taxes based on the punitive tariff as the result of engaging in illegal land use. Such illegal land use occurred because the new property owner failed to update the property information and conditions. Based on the data collected through semi-structured interviews, questionnaires administered to a sample completed by the study’s participants, and the secondary research process that included the review of official policy documents, qualitative, and quantitative analysis were performed to achieve important findings of this study. Zoning applies to land with cadastral boundaries, implying that zoning is only applicable to surveyed land. Zones are depicted on the zone scheme maps, and these have the aim to inform land owners of potential development rights that are stipulated in the land use management schemes. Zoning forms the basis for property valuations and property tax (rates) calculation purposes. The other factor used in the calculation of the rate is the value of the rateable properties registered in the valuation roll. Every five years, a new valuation roll is published for review before the adoption by the various municipalities’ councils. The setting of tariffs is informed by the budget requirements of the municipalities to enable them to finance or deliver municipal services. The tariff scales are determined in line with the land use categories. Municipalities publish the tariffs yearly, after the adoption of the budget by the municipalities’ councils. The remedies available to municipalities is levying a punitive rate to try to change the owner’s land use and move it from unauthorised/illegal use of the land outside the category of use to an updated, legal use. The research findings indicate that the Gauteng Provincial Government’s relevant department lacks the necessary structures and processes to monitor changes in the bylaws or land use schemes of municipalities, and the payment of property rates does not hold any strategic importance in the management of properties. The department did not have a system or process in place to review the valuation roll, or to monitor the annual tariff rate adjustments. Therefore, the present research recommends several measures the department will have to implement to limit wasteful and fruitless expenditure regarding property rate payments. , Thesis (MSc) -- Faculty of Engineering, the Built Environment and Technology, School of Built Environment and Civil Engineering, 2024
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  • Date Issued: 2024-04

Investigation of four roof-shaped host compounds for their separation potential of mixtures of guest Isomers and related compounds

  • Authors: Senekal, Ulrich
  • Date: 2024-04
  • Subjects: Grignard reagents , Optical isomers -- Analysis , Supramolecular chemistry
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/64368 , vital:73684
  • Description: The inclusion ability of four roof-shaped host compounds, namely trans-9,10-dihydro-9,10- ethanoanthracene-11,12-dicarboxylic acid (H1), dimethyl trans-9,10-dihydro-9,10- ethanoanthracene-11,12-dicarboxylate (H2), trans-α,α,α’,α’-tetraphenyl-9,10-dihydro-9,10- ethanoanthracene-11,12-dimethanol (H3) and trans-α,α,α’,α’-tetrakis(4-chlorophenyl)-9,10- dihydro-9,10-ethanoanthracene-11,12-dimethanol (H4), were investigated when presented with numerous guest series (eight in number), including the xylene isomers and ethylbenzene, pyridine and the methylpyridine isomers, structurally related toluene, ethylbenzene and cumene, the dichlorobenzenes, six-membered heterocyclic ring compounds (dioxane, morpholine, piperidine and pyridine), anisole and the methylanisole isomers, anisole and the bromoanisole guests, and phenol and the methoxyphenol isomers. The four host compounds were synthesized via Diels-Alder (H1), esterification (H2) and Grignard addition (H3 and H4) reactions, producing yields of product of up to 93%. The yields for the Grignard reactions were lower, 54 and 37%, for the corresponding procedures using phenylmagnesium bromide or 4-chlorophenylmagnesium bromide. Computational molecular modelling studies were conducted on all four host compounds, and the resultant molecular geometries compared with the apohost (guest-free) crystal structures, when available. The geometries of the lowest energy conformers were in close correlation with the observed host structures as obtained from the apohost crystal structures (unfortunately, H3 and H4 were not able to form adequate quality crystals for SCXRD analyses). Interestingly, H1–H4 displayed intramolecular non-classical C–H∙∙∙O hydrogen bonds, while only H1 and H2 demonstrated intermolecular interactions of this type. H3 and H4 assumed one of two forms depending on the guest that was employed: the “active” form presented a strong intramolecular O–H∙∙∙O hydrogen bond, while the “inactive” form possessed weak π∙∙∙π and O–H∙∙∙π interactions. All of the host compounds were subjected to crystallization experiments from each of the guest species, as well as from mixtures of guests from each series (the guest competition experiments), where 1H-, 13C-NMR spectroscopy, GC-MS and/or GC-FID were used to analyse any resultant solids formed, as applicable. Single crystal X-ray diffraction (SCXRD) experiments were carried out on each single solvent complex produced in this work, where the crystal quality was suitable, while thermal analyses were also employed on these to determine their relative thermal stabilities. During the single-guest crystallization experiments, H4 was found to be remarkable in its inclusion ability, forming complexes with all but p-dichlorobenzene, typically with a 1:1 host:guest (H:G) ratio. H1 was more selective in its inclusion behaviour, not enclathrating cumene, 3-bromoanisole, phenol or the three methoxyphenol isomers (favouring 1:1 or 2:1 H:G ratios where complexation was successful). Interestingly, H1 formed salts when presented with 2- and 3-methylpyridine, and morpholine and piperidine. H2 and H3 were less remarkable in their inclusion ability, furnishing apohost crystals or gels in some experiments (typically a 3:1 H:G ratio was favoured for both when complexation occurred). Of the four roof-shaped host compounds, H1 and H4 displayed enhanced selectivities for certain guest species, showing near-complete affinity for a specific guest compound when presented with a guest mixture. H1 was able to include 100.0 and 98.8% p-dichlorobenzene (p-DCB) (from m-DCB/p-DCB and o-DCB/p-DCB mixtures), 96.6 and 93.6% p-xylene (p-Xy) (from m-Xy/p-Xy and o-Xy/p-Xy), 99.3% 4-methylanisole (4-MA) (from 2-MA/4-MA) and 97.1% 4-bromoanisole (4-BA) (from ANI/2-BA/3-BA/4-BA, where ANI is anisole). Host compound H4 was able to include ≈ 90% of selected meta-substituted guests, while H2 and H3 demonstrated moderate preferences for the guest compounds employed in this work (< 60%). It was concluded that some xylene guest mixtures may be purified using all but H2, whereas only H1 and H2 showed potential in separating the pyridines. All but H2 may also be employed in the separation of selected dichlorobenzene mixtures, while H2 showed potential for the separation of the six-membered heterocyclic guest compounds (dioxane, morpholine, piperidine and pyridine), were these ever required to be separated. Both H1 and H4 exhibited an overwhelming affinity for the methyl- and bromoanisole guest compounds, and this work has shown that these are likely host candidates for the purification of a variety of these guest mixtures through supramolecular strategies. SCXRD analyses showed that H1 experienced intermolecular host···host hydrogen bonding interactions between the carboxylic acid functional groups, while H2 typically demonstrated intermolecular non-classical hydrogen bonds in its complexes, forming sheets of host molecules along the c-axis. H4 preferred the “inactive” form whereas H3 assumed either an “active” or “inactive“ form. Various host···guest interactions such as π∙∙∙π, C–H∙∙∙π, C–O∙∙∙π, hydrogen bonding and other short contacts were responsible for guest retention in the crystal structures. Thermal analyses were conducted on all of the successfully formed complexes. Ton (the guest release onset temperature) and Tp (the temperature at which the guest release was most rapid) were recorded, when possible, while the mass losses associated with the guest release event were compared with those mass losses expected, in most cases. , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
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  • Date Issued: 2024-04

Investigation of the host potential of compounds derived from tartaric acid, succinic acid and 1,4-cyclohexanedioic acid

  • Authors: Adam, Muhammad Ameen
  • Date: 2024-04
  • Subjects: Chemical reactions , Chemistry, Organic , Bacteriology
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/63617 , vital:73562
  • Description: The present investigation considered the host behaviour of three compounds, namely (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (H1), 1,1,4,4-tetraphenyl-1,4-butanediol (H2) and cyclohexane-1,4-diylbis(diphenylmethanol) (H3) in various guest mixtures. These host compounds were readily synthesized by means of Grignard addition reactions on the diesters of tartaric acid, succinic acid and 1,4-cyclohexanedioic acid. The guest mixtures included cyclopentanone, cyclohexanone, cycloheptanone and cyclooctanone, γ-butyrolactone, 2-pyrrolidone, N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone, and pyridine, 2-methylpyridine, 3-methylpyridine and 4-methylpyridine. Crystals of (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (H1) were grown from cyclopentanone (5-ONE), cyclohexanone (6-ONE), cycloheptanone (7-ONE) and cyclooctanone (8-ONE,) producing 1:1 host:guest complexes in each instance. Thermal analysis showed the thermal stabilities of these complexes to be in the order 6-ONE > 7-ONE > 8-ONE > 5-ONE which correlated exactly with results from binary guest/guest competition experiments, where 6-ONE was always preferred by H1, while 5-ONE was consistently disfavoured. Single crystal X-ray diffraction (SCXRD) analyses demonstrated that each guest compound was retained in the crystals by means of a hydrogen bond with an alcohol moiety of the host compound. Furthermore, preferred guests 6- and 7-ONE produced crystals with greater densities than guests less favoured (5- and 8-ONE). A conformational analysis of the guest geometries in the four complexes with H1 revealed that the low energy guest conformers were present. The host selectivity for 6- and 7-ONE was proposed to be due to the improved molecular packing in the crystals of the complexes containing these two guest compounds, observed from their higher crystal densities. Hirshfeld surface analyses were not useful in explaining the preference of H1 for 6-ONE relative to 7-ONE (these types of analyses were not possible for the 5-ONE and 8-ONE-containing inclusion compounds due to the nature and degree of disorder present in the guest molecules). H1 was also crystallized from γ-butyrolactone (GBL), 2-pyrrolidone (NP), N-methyl-2-pyrrolidone (NMP) and N-ethyl-2-pyrrolidone (NEP), and 1H-NMR spectroscopy revealed that all but GBL were included. The host compound was also presented with these guest solvents in various mixtures, and it was observed that NMP was an extremely favoured guest solvent, followed by NEP and NP, with GBL being consistently disfavoured in every experiment. It was therefore shown that in certain instances, H1 may serve as an alternative tool for separating some of these mixtures through host-guest chemistry strategies. The hydrogen bonding motifs present in each of the successfully formed complexes were extensively investigated through SCXRD analysis, as was the thermal behaviour of these complexes. In the latter instance, the peak temperature of the endotherm (from the DSC trace) representing the guest release was greater for the inclusion compound with favoured NMP (145.5 °C) relative to the complexes with NP (139.8 °C) and NEP (120.5 °C). Host compounds H2 and H3 were revealed to have the ability to include each of pyridine (PYR), 2-methylpyridine (2MP), 3-methylpyridine (3MP) and 4-methylpyridine (4MP). H2 displayed selective behaviour for 3MP and 4MP when presented with mixtures of these guest compounds, whilst H3 preferred PYR. In the latter case, this PYR-containing inclusion compound was also the more stable one (the guest release onset temperature was highest, Ton 66.0 °C). It was demonstrated that H2 has the ability to separate very many binary mixtures of these pyridines on a practical platform, since K (the selectivity coefficient) values were 10 or greater in many instances. However, unfortunately, the more difficult-to-separate mixtures containing 3MP and 4MP cannot be purified or separated by employing H2 and supramolecular chemistry strategies. H3 was also shown to be a likely candidate for binary guest separations in very many of the guest solutions considered here, where K was also 10 or greater, and even infinity in many cases. SCXRD demonstrated that 2MP, 3MP and 4MP were retained in the crystals of their complexes by means of classical hydrogen bonds with the host compound. Satisfyingly, this hydrogen bond between 2MP and H2 (3.0213(18) Å) was significantly longer than that between this host compound and both disorder components of 3MP (2.875(2) and 2.825(9) Å) and that between H2 and 4MP (2.8458(13) Å). This observation explains the affinity of H2 for both 3MP and 4MP, and why 2MP was disfavoured. The results of thermal experiments did not wholly concur with observations from the guest/guest competition experiments. Hirshfeld surface analyses were also conducted but were not entirely conclusive with respect to explaining the host selectivity behaviour. In the case of H3, SCXRD analyses revealed that favoured PYR experienced a classical hydrogen bond with the host compound that was statistically significantly shorter (2.795(2) Å, 165°) than those between the other guest compounds and H3. Additionally, this guest compound was the only one to be involved in a (host)C−H···π(guest) interaction (2.91 Å, 139°) and also a non-classical hydrogen bond with the host compound ((host)C−H···N−C(guest), 2.77 Å (144°)). Finally, Hirshfeld surface analyses showed also that preferred PYR experienced a greater percentage of C···H/H···C (33.1%) and H···N/N···H (11.1%) interactions compared with the complexes with 2MP, 3MP and 4MP. However, it is not clear whether these Hirshfeld observations explain the affinity of H3 for PYR. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
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  • Date Issued: 2024-04

Investigation of the synthesis and characterisation of spiro orthocarbonates and heterocyclic orthocarbonates

  • Authors: Cuthbertson, Jarryd Pierre
  • Date: 2024-04
  • Subjects: Chemistry, Analytic , Analytical chemistry , Chemistry
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/63678 , vital:73578
  • Description: A series of mostly asymmetrical spiro orthocarbonates and heterospirocyclic derivatives of orthocarbonic acid was synthesized from 2,2-dichlorobenzodioxole and a number of difunctional reagents. A systematic study of the size of the chelate rings formed around the spirocentric carbon atom was conducted by selecting representative samples of aliphatic and aromatic diols. The feasibility and scope of potential starting materials used was expanded by reacting DCBD successfully with thiols. Molecular structures of these compounds were confirmed using diffraction studies on single crystals. All compounds were analyzed using multinuclear NMR. DFT calculations performed on the compounds allowed for the development of equations that can accurately predict 13C chemical shifts of SOCs. Furthermore, the experimental NMR spectroscopy gave rise to an increment shift system for the 13C NMR shifts allowing for further assignment of carbon atom positions in compounds with multiple possible bonding patterns. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
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  • Date Issued: 2024-04

Learners’ understanding of their linguistic resources as a basis for learning natural sciences

  • Authors: Thorne, Rochelle Eugenia
  • Date: 2024-04
  • Subjects: Linguistic analysis (Linguistics) , Science -- Study and teaching -- Methodology , Science -- Study and teaching (Elementary)
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/64049 , vital:73646
  • Description: With eleven official languages, South Africa is known for its multilingual environment. Despite this, the country's educational system heavily favours English and Afrikaans. Despite the varied linguistic backgrounds of learners, English continues to be used as the Language of Learning and Teaching (LoLT), which raises questions regarding fair access to education. Within the context of South Africa's constitution and policy frameworks, particularly the Language in Education Policy (LiEP), this study aims to investigate how group work activities in a Natural Sciences classroom can give learners an opportunity to mobilise their multilingual repertoires. Three formerly Afrikaans-medium high schools in the Northern Areas of Gqeberha, were the sites for this research which focuses on Grade Nine Natural Sciences learners. Through the use of both quantitative and qualitative methods such as questionnaires, classroom observations, and focus groups, the study explores how learners make use of their language resources to navigate science instruction in English. The results contest the idea that languages are distinct entities and show that learners use language interchangeably as a learning tool, a practice known as translanguaging. Group work becomes an important space in which learners exercise agency in language selection, enabling the link of dialogical, multilingual, and cultural responses. Sociocultural theory offers insights into group work relationships and provides the theoretical foundation for understanding how learners use language to understand scientific topics. Building on Gibbons' mode continuum (2003), which maps the shifts in discourse in classroom contexts from every day talk at the “here and now” to more specialized talk, the study also explored an expanded continuum which aimed at clarifying the nuances of language and cognitive progression among learners working in collaborative groups. This study adds to the conversation about language ideologies by recognising the ideologies of inclusion, access and identity which informed learners’ thinking and attitudes to language choice in education. Thus, the study emphasises the importance of a sophisticated comprehension of multilingual repertoires in the classroom. In order to better accommodate the changing linguistic patterns of multilingual learners, the study recommends re-evaluating language policies and encouraging educators to exploit the potential of group work to develop understanding of scientific concepts. , Thesis (DPhil) -- Faculty of Education, School of Post Graduate Education, 2024
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  • Date Issued: 2024-04

Lion and leopard diet and dispersal in human-dominated landscapes

  • Authors: Forbes, Ryan Edward
  • Date: 2024-04
  • Subjects: Carnivora -- South Africa , Carnivorous animals -- Conservation , Carnivorous animals -- Ecology
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/63766 , vital:73596
  • Description: Terrestrial carnivore population declines are driven by habitat loss and fragmentation, prey-depletion, persecution, and retaliatory killings. Population strongholds now centre on protected areas, that face increasing human pressure, resulting in population isolation, declining prey populations, and livestock intrusion. I therefore aimed to investigate dispersal and connectivity, and diets of lions (Panthera leo) and leopards (P. pardus) in response to human-use and wildlife density gradients in the Greater Limpopo Transfrontier Conservation Area (GLTCA). Firstly, I investigated dispersal and connectivity for these carnivores across the GLTCA, using single nucleotide polymorphisms. I present evidence that in the prey-depleted Mozambique portion of the GLTCA, lion and leopard dispersal distances are higher compared with the prey-abundant Kruger National Park (KNP). I also provide the first evidence for long-range dispersal in female lions. Despite evidence for connectivity occurring across the GLTCA, I recorded population structuring across the region for both carnivores, likely due to habitat fragmentation by human activities in the Mozambique portion of the GLTCA. I then assessed carnivore diet responses to prey depletion and livestock availability by comparing lion and leopard diets in the prey-abundant/livestock-absent KNP (South Africa), with the prey-depleted/livestock-abundant Limpopo National Park (LNP, Mozambique), using scat analyses. Lions and leopards downshifted their prey size selection in LNP relative to KNP. Despite both carnivores expanding their dietary niche breadths in LNP relative to KNP, diet overlap did not differ between sites. This suggests that even when prey is depleted, lions and leopards can partition food resources, which likely limits competition. Despite cattle (Bos taurus) being the most abundant ungulate in LNP, lions and leopards strongly avoided cattle, supporting the notion that carnivores can perceive the risk of hunting livestock and modulate their foraging behaviour to reduce human-carnivore conflict. Should my findings reflect general patterns in carnivore dispersal and diet responses to human-use and wildlife gradients, then carnivore conservation initiates across their range should focus on prey population rehabilitation, improved livestock husbandry practices, the establishment of effective dispersal corridors and improved human-tolerance towards large carnivores. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
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  • Date Issued: 2024-04

Mathematical modelling of the tumour treatment with chemotherapy

  • Authors: Nyaweni, Fundile Sindy
  • Date: 2024-04
  • Subjects: Mathematical models , Mathematics , Chemotherapy
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64289 , vital:73672
  • Description: In this study, a cancer disease model incorporating predator-prey dynamics between immune cells and tumor cells, as well as competition between tumor cells and normal cells, is formulated in an attempt to understand the interaction dynamics that govern the complex interplay within the tumor microenvironment. Mathematical analysis is employed to derive conditions for the boundedness of solutions and to discuss disease thresholds such as the basic reproduction number, R0. Equilibrium points are identified, and stability conditions for the system are derived. Sensitivity analysis is used to assess uncertainties in the parameters of the model, specifically their impact on R0. Numerical simulations are conducted, utilizing the Runge-Kutta scheme to solve the model. Furthermore, optimal control (OC) techniques are applied to examine the role of chemotherapy in enhancing tumor cell elimination and minimizing adverse effects on immune cells and normal cells. The improved model, incorporating normal cells, anticancer drugs, and immune cells, allows for a more comprehensive analysis of the dynamic interactions within the biological system. The optimal control is determined using the forward-backward sweep numerical method. The numerical simulation is carried out in MATLAB to validate and complement the analytical findings. The results indicate that a low concentration of the drug leads to a prolonged period for tumor clearance. Conversely, a higher drug concentration results in quicker tumor clearance, albeit with adverse effects on normal and effector cells. The OC identifies when to stop the treatment once the tumor clears. Furthermore, OC facilitates the regeneration of normal and immune cells beyond treatment, in contrast to a control scenario without optimization. The findings highlight the importance of early detection and careful chemotherapy dosage selection for effective and personalized cancer treatment strategies. , Thesis (MSc) -- Faculty of Science, School Computer Science, Mathematics, Physics and Statistics, 2024
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  • Date Issued: 2024-04

Multi-purpose community centres as catalysts for socio-economic development in Eastern Cape province, South Africa

  • Authors: Gobe, Cynthia Bongiwe Ntombikayise
  • Date: 2024-04
  • Subjects: Community centers -- South Africa , Buildings -- Environmental engineering -- South Africa , Sustainable construction -- Economic aspects , Infrastructure (Economics) -- South Africa Sustainable development
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/64533 , vital:73747
  • Description: The central issue facing African society, especially underdeveloped countries is that most of the population lives below the poverty line, experiences high levels of unemployment and unsustainable livelihoods. The poor and marginalised groups in many communities are deprived access to infrastructure and socio-economic amenities, this includes accessibility to government services, information, and developmental opportunities. The development of Multi-purpose Community Centres (MPCCs) is viewed as a value-adding solution to several challenges facing unequal societies, such as inadequate infrastructure, remote settlement patterns, poor access to basic services, poor access to technology, poor access to information, increased unemployment rate, increased poverty rate, and many others. The study examines the socio-economic impact of MPCCs on municipalities of the Eastern Cape Province in South Africa and explores how these centres, as built environment outputs can become a stimulus for sustainable livelihoods in urban, rural, and peri-urban human settlements, including informal settlements. The study falls under implementation evaluation research methodologies which assesses whether a programme has been adequately implemented before making inference on its effectiveness. Anchored in a Social Constructivism knowledge paradigm and leaning on a Systems and Development Theories, the study adopted a Mixed Method Research approach. In view of the data required document reviews, field observations, interviews and questionnaire surveys were employed. The research findings revealed that despite the delivery of MPCCs by the Department of Human Settlements, these centers have not provided much socio-economic opportunities to members of the communities where they are built. The MPCCs under study are facing many challenges that render them ineffective to fulfill their mandate of improving the lives of residents. The study yielded an inclusive and responsive human settlements development model for the creation of well-functioning socio-economic impactful MPCCs within existing and forth-coming housing projects and informal settlements. , Thesis (DPhil) -- Faculty of Engineering, the Built Environment, and Technology, School of Built Environment and Civil Engineering, 2024
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  • Date Issued: 2024-04

Optimisation of laser welding for thin-walled Ti6Al4V glider pressure hull

  • Authors: Nel, Matthew Ryan
  • Date: 2024-04
  • Subjects: Laser welding , Welding , Mechanical engineering
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64739 , vital:73882
  • Description: Laser welding is a type of fusion welding process characterised by deep penetration, low heat input and high welding speed. This dissertation investigates the suitability of this process for the fabrication of an underwater glider buoyancy engine from thin Ti6Al4V alloy sheet. Areas of interest include the effect of process parameters on weld microstructure, static properties (microhardness, tensile and bend tests) and dynamic properties (fatigue tests). The effect of welding speed and laser defocusing were evaluated considering experimental matrices consisting of four different travel speeds and three defocus distances. These were narrowed down to three travel speeds and a single defocus distance, resulting in a final test matrix delivering three different heat inputs. Thereafter, the effect of heat input on static and dynamic properties was investigated. Vickers microhardness tests were carried out to predict weld response during tensile testing, with the expectation being that harder welds would offload more strain. This was confirmed using digital image correlation, which allowed for virtual measurement and visualisation of strain offloading. Bend tests were carried out on parent and welded samples to confirm whether Ti6Al4V could be formed to the correct geometry. Forming Ti6Al4V into a U-shape was the first consideration, since dynamic testing required samples of this geometry with longitudinal weld orientation. A two-stage forming methodology was developed from these experiments. Formed samples were subjected to fatigue tests in a custom designed fatigue platform for testing weld orientation as it would appear in the final component. Prediction of the welded buoyancy engine life was the goal behind these tests. Fracture surfaces were analysed to gain understanding of where crack initiation and final fracture occurred. Porosity served as the primary cause for crack initiation in failed samples. Pore distribution was heaviest in low-heat weldments and decreased with increasing heat input, while pore size increased with increasing heat input. This resulted in medium-heat weldments exhibiting superior performance to that of low- and high-heat ones. It was concluded that the laser welding process is able to produce weldments of sufficient integrity in thin Ti6Al4V sheet-formed components intended for use in glider buoyancy engines. , Thesis (MEng) -- Faculty of Engineering, the Built Environment and Technology, School of Engineering, 2024
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  • Date Issued: 2024-04

Optimisation techniques to improve the drive efficiency of a mobile ventilator platform

  • Authors: Imran, Mohammed Zaahid
  • Date: 2024-04
  • Subjects: Artificial respiration , Respirators (Medical equipment) , Topology , Medical instruments and apparatus -- Design and construction
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64555 , vital:73749
  • Description: COVID-19 pandemic has underscored the indispensable role of mechanical ventilators in providing critical respiratory support to patients. This research has focused on the imperative task of optimising the articulation system of the ventilator, designed to enhance its efficiency, with particular emphasis on improving the volume displacement from the ambu bag. Several optimisation methods were explored, including generative design (GD), Design of Experiments (DOE), Shape optimisation, and topology optimisation. The study also highlights the significance of additive manufacturing and material testing in developing ventilator components. The study delves into the intricate development and fine-tuning of the ventilator setup, emphasising its pivotal role in delivering life-sustaining respiratory aid. The ventilator’s core mechanisms, featuring a two-pusher arm system powered by a servo motor, was engineered intricately to apply precise pressure on the ambu bag. The research underscores the importance of optimising both the pusher arm and pressure plates to improve air displacement within the system. A significant challenge addressed in this research was the excessive strain on the servo motor owing to the demands of the articulation system. The research employed strategies such as shape optimisation and topology optimisation to reduce the stress on the articulation system while increasing the air displacement and thus reducing the pusher arm displacement on the ventilator. The research methodology included stages such as setting performance benchmarks, calibration, and verification to ensure precision and reliability; shape optimisation for maximum efficiency; and topology optimisation for superior structural performance and reduced weight. These interconnected stages were instrumental in the comprehensive development and enhancement of the ventilator system, ensuring its effectiveness and dependability in delivering lifesaving respiratory support.This research extensively examined sensor reliability and performance through verification tests and calibrations, highlighting the precision of the servo motor and the suitability of the 5-Amps current sensor for monitoring servo motor current without additional calibration. Optimisation efforts aimed to enhance the ventilators performance by relocating the pusher arm to the bag’s centre, resulting in improved volume displacement efficiency by 7.78 % and a 25.35 % reduction in current consumption. Shape optimisation, especially with curvature-based pressure plates, increased volume displacement by 84.47 % reaching an optimal configuration outputting 1475.73 ml of volume per compression. Understanding the forces through strain gauges and FEA facilitated topology optimisation, the MAXSTIFFDS15 configuration demonstrated promising results by reducing component weight and achieving significant energy savings of 45.04 %, potentially reducing long-term costs. , Thesis (MEng) -- Faculty of Engineering, the Built Environment, and Technology, School of Engineering, 2024
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  • Date Issued: 2024-04

Out of place: an analysis of place as a contributor to the complexities of my “coloured” identity in Malabar, Gqeberha

  • Authors: Flowers, Victoria
  • Date: 2024-04
  • Subjects: Colored people (South Africa) -- Race identity , Ethnicity in art -- South Africa -- Port Elizabeth , Modernism (Art)
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/62780 , vital:72954
  • Description: Coloured identity has been a historical point of contestation in South Africa because Colouredness is assumed as “an inbred quality that arises automatically from miscegenation while instrumentalists share the essentialist premise that coloured identity is something negative and undesirable but blame it on the racism and the exploitative practices of the ruling white minority” (Adhikari, 2009: 15). This archaic belief attributed to racial mixture has now become redundant, due to the emergence of new hybridised Coloured identities that factor other ethnic and cultural groups as well as internal and external elements into their conception. The role of Place in the formation of Coloured identities is at the core of this fine arts based enquiry. This study is located in Malabar, Gqeberha which was established after the forced removals onset by the Group Areas Act of 1950 and the displacement of residents from South End. Additionally, it considers specific locations significant in their linkages to hybridised peoples, and how the place and individuals have been influenced by historical legacies of colonisation and apartheid. These are examined to consider their function in contextualising contemporary lived experiences of Coloured identity within the community of Malabar and its effect on artistic practice through autoethnographic research. Through this autoethnographic and reflexive study and the accompanying empirical research process, I critically examine and explore my Coloured identity as part of being-in-the-world (Heidegger, 1962). This ‘being’ is multifaceted as a result of the significance of Place in South Africa and how it has shaped my perception of how and where I have a sense of being and belonging. , Thesis (MA) -- Faculty of Humanities, School Visual and Performing Arts, 2023
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  • Date Issued: 2024-04

Photocatalytic reduction of CO2 into green fuels on microspherical nanocomposites comprising of CdS, TiO2, ZnFe2O4 semiconductors and heterojunctions

  • Authors: Mudau, Rendani Julian
  • Date: 2024-04
  • Subjects: Heterojunctions , Chemistry, Inorganic , Nanochemistry
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64214 , vital:73665
  • Description: Human anthropogenic activities have led to an increase in CO2 levels resulting in global warming. There is a need to reduce CO2 levels in the atmosphere by capturing the gas and converting the captured CO2 into fuels. Photocatalytic conversion of CO2 into valuable products via photoreduction is a promising technique to reduce carbon dioxide using sunlight and water. Redox reactions between CO2 and water using photocatalysts offer an effective method of lowering CO2, which has detrimental effects on the environment. This dissertation reports the synthesis and characterization of five photochemical catalysts comprising of CdS, TiO2, ZnFe2O4 semiconductors and heterojunctions and their use as photocatalysts for the photocatalytic reduction of CO2 into green fuels. Mott−Schottky plot of TiO2, CdS and CdS/TiO2 confirmed the formation of n-type, n-type, and n-n type material respectively. The band gap of TiO2, CdS, and CdS/TiO2 obtained were 3.21,2.24, 2.04 eV, respectively, the combination of TiO2 and CdS resulted in the lowering of band gap energy which is favourable for photocatalytic reduction studies. XRD of TiO2, CdS and CdS/TiO2 provided relevant information about the various phase reflections of the photocatalysts, it also supported reports confirming the increase in crystallite size of TiO2 anatase phase upon calcination. Chemical environment of the various photocatalysts, such as Ti2p1/2, Ti2p3/2, O1s, Cd3d3/2, Cd3d5/2, S2p1/2 and S2p3/2 were observed in TiO2, CdS and CdS/TiO2. BET surface area of TiO2, CdS and CdS/TiO2 was also observed to be 2.9243, 4.0605, and 9.8450 m2g, respectively. Photocatalytic reduction of CO2 resulted in formic acid, formaldehyde, acetic acid, carbon monoxide, ethanol, and methanol after 12 h. Modification of CdS with TiO2 to form CdS/TiO2 produced high yield of formic acid (217.7 μmol/g) compared to CdS (8.7 μmol/g) and TiO2 (122.5 μmol/g). CdS had high yield of formaldehyde (20.4 μmol/g) and ethanol (57.8 μmol/g) compared to TiO2 (12.9, 3.6 μmol/g of formaldehyde and ethanol, respectively) and CdS/TiO2 (19.7 μmol/g and there was no detection of ethanol). TiO2 shows high yield of methanol (145.2 μmol/g) and is the only catalysts that produced carbon monoxide (52.2 μmol/g) compared to CdS (87.8 μmol/g of methanol) and CdS/TiO2 (50.2 μmol/g of methanol). A detailed elucidation of the various products was reported by means of nuclear magnetic resonance (NMR) spectrometer. ZnFe2O4 and CdS/TiO2/ZnFe2O4 were characterized and employed for photocatalytic reduction of CO2 in water. XRD and XPS confirmed the presence Fe (2+) and Fe (3+) in tetrahedral/octahedral and Zn (2+) in tetrahedral on ZnFe2O4 and CdS/TiO2. CdS/TiO2/ZnFe2O4 presented a lowered band gap of 1.98 eV due to the presence of ZnFe2O4 while the band gap of ZnFe2O4 obtained is 1.95 eV. The Mott-Schottky plots confirmed the conduction (2.81 and 2.59 eV) and valence band (–0.86 and –6.1 eV) of ZnFe2O4 and CdS/TiO2/ZnFe2O4 together with their junctions, respectively. ZnFe2O4 and CdS/TiO2/ZnFe2O4 are p-type and p-n type junctions, respectively. Photocatalytic reduction of CO2 under visible light for 12 h using CdS/TiO2/ZnFe2O4 hollow microspheres nanocomposites produced methanol (182.1 μmol/g), formic acid (1.9 μmol/g), formaldehyde (9.5 μmol/g), ethanol (67.1 μmol/g), and oxalic acid (38.9 μmol/g). Amongst the synthesized catalysts, CdS/TiO2/ZnFe2O4 produced high yield of methanol, ethanol, and oxalic acid. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
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  • Date Issued: 2024-04

Photoluminescence and electroluminescence imaging of PV devices

  • Authors: Roodt, Roelof Petrus
  • Date: 2024-04
  • Subjects: Photoluminescence , Biosensors
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64333 , vital:73676
  • Description: Luminescence imaging has become a particularly useful and valuable tool for the characterisation of photovoltaic devices. This study entailed the design, construction, and optimisation of a system for the electroluminescence (EL) and photoluminescence (PL) imaging of various solar cell devices. The system can perform EL and PL imaging of solar cells of different cell technologies and materials systems, including Si, perovskite, and triple-junction concentrator solar cells. This required appropriate electrical power supplies for carrier injection for EL imaging and optical excitation for PL imaging. The different materials systems also required wavelength appropriate filters for PL imaging. In addition, the system utilized a temperature-controlled sample stage and was placed in a chamber for environmental control and isolation of UV radiation from laboratory. In addition to optimization of imaging conditions, luminescence images need to be optimized to facilitate detailed analysis and the application of appropriate algorithms to extract device parameters and hence generate device parameter images of the devices under investigation. For EL imaging, two power supplies were used to inject current into the solar cells. The reason for the two power supplies is that the first power supply had a current range of ± 1 A and an applied voltage capability of ± 21 V. This was used for the smaller solar cells. It was also convenient to use as the power supply could also measure the injected current and applied voltage and digitally store it with the images. For the larger solar cells, a second power supply was utilized, which could inject current into the samples in the range of ± 12 A at an applied voltage of ± 40 V. To measure the current and voltage of the power supply provided, two digital multimeters were utilized. For acquiring images, the same camera was used for EL and PL imaging. The sensor used in the camera is a silicon CMOS sensor. For PL imaging, four light emitting diode (LED) boards, consisting out of sixty-four LED’s, per board, of four different wavelengths, were used to optically excite the solar cells. The four wavelengths emitted by the LED’s were chosen to match the bandgaps of the different solar cell devices investigated. The LEDs were powered with a multi-channel constant voltage power supply, where the current could be varied. The Si solar cell is a 156 x 156 mm commercial solar cell. The perovskite solar module is a 40 x 40 mm module, which consists out of six cells connected in series. The triple-junction concentrator solar cell has a dimension of 10 x 10 mm which consists of three junctions staked on top of one another. These three layers consist of indium gallium phosphate (InGaP), indium gallium arsenide (InGaAs) and germanium (Ge). To capture EL and PL images of these various solar cell devices, filters of specific wavelengths were placed in front of the camera to isolate the light generated by the different devices. In addition to isolating the luminescence observed from the solar cells, an image correction procedure was adapted from literature, to be applicable to acquiring luminescence images of these various solar cells. As there are a range of factors which influence the quality and clarity of the luminescence images, i.e., chromatic aberration, diffraction, and absorption depth, to name a few, the wavelength dependency of these factors was investigated. This was done by acquiring a point spread function (PSF) for each of these devices and then using these PSF's together with a deconvolution algorithm to correct the luminescence images. The PSF was acquired by fitting a point source emission image to a function that includes exponential and Gaussian terms. The point source image was obtained by placing a black piece of vinyl with a pinhole in it over the solar cell. To communicate with all the various devices and to acquire images at various intensities a LABVIEW program was written. This was used then used to control the power supplies, digital multimeters, camera, and the LED's. This allowed for the user to specify at what points along the current-voltage (I-V) curve data points needed to be measured together with the luminescence images captured. For PL imaging the intensity of the LED's was then also adjusted according to user specified values. The system was utilised to acquire EL images of the Si solar cell, EL and PL images of the perovskite solar cell and EL images of the InGaP and InGaAs layers in the triple-junction concentrator solar cell. With the correction procedure utilised in this study, it was seen that the image quality and clarity improved, compared to the conventional way of capturing luminescence images. These statements are supported by the results obtained for the series resistance maps of the Si solar cell and the perovskite solar module, as the series resistance maps obtained from the corrected luminescence images have less noise and more detail compared to the results from the raw luminescence images. From the EL images captured for the two layers of the triple junction concentrator, it was clear that the intensity profile of the two layers is different, as the intensity for the InGaP layers was that the device had bright edges and darker intensity on the interior where exactly the opposite was observed for the InGaAs layer, having a bright interior and darker edges. This is most likely due to the opto-electric coupling of these layers withing the triple junction solar cell. For the series resistance images obtained for the Si solar cell, it is observed that at lower carrier injection, the series resistance is lower compared to higher carrier injection levels. This result can also be influenced by the increase in cell temperature with the increase in injected carriers. The series resistance maps obtained from the perovskite EL images shows an interesting result. As the perovskite solar cell has degraded, three of the six cells have optically inactive regions, showing lower luminescence intensities. The series resistance of the other three cells are much lower compared to these cells that have inactive regions under low injection conditions. As the injection level increases, it is seen that the series resistance values of five of the six cells become comparable to one another. With regards to the PSF, it was found that using a bandpass filter in front of the lens reduced to amount of spreading observed from a single point source across the detector. Furthermore, there is a strong wavelength dependency in the PSF as the severity increased with increase in the emission wavelength of the solar cells under investigation.In this study an opto-electrical characterisation system was constructed to acquire PL and EL images of various solar cell technologies. In addition to this, a range of factors that influence the quality of these images were investigated and used in the image correction procedure to correct the images for all these cell technologies. It was shown that the correction procedure works for all three of the technologies investigated in this study, and all these factors showed a strong wavelength dependency. These corrected luminescence images together with current-voltage (I-V) data was then used to determine characteristic parameters of a one-diode model of the various PV devices. This was not only achieved, but it also clearly indicated that all the correction procedures need to be considered to obtain a clear and accurate representation of the actual PV device. This has a major influence on the understanding and improvement of these PV devices. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
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  • Date Issued: 2024-04
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