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The androgenic and anabolic effects of pine pollen on Nile tilapia (Oreochromis niloticus)

  • Authors: Abaho, Ivan
  • Date: 2023-10-13
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/431615 , vital:72790 , DOI 10.21504/10962/431615
  • Description: All-male tilapia aquaculture is desirable to control unwanted breeding. Besides, male tilapia individuals grow faster and bigger than females. Presently, most farmers use 17α- methyltestosterone (MT) to produce an all-male stock, although the hormone is associated with human health and environmental risks. Recently, plant-based products have been reported to induce masculinisation in fish and are considered safe nature-based alternatives to MT. The present study utilised pine pollen (PP) to induce female-to-male sex change in Nile tilapia (Oreochromis niloticus). Prior to the start of the research, there was insufficient information on the use of PP for sex inversion, with no published data on the sex change mechanism, hence limiting the progress in the application of the product from experimental to hatchery levels. In this study, the optimal dietary inclusion of PP for maximum masculinisation of Nile tilapia was investigated by feeding three-day-old fish graded PP levels (80, 160, 320, 640, 1,280, 1,920, 2,560 and 3,200 mg kg-1 basal diet) from 3 to 30 days post-hatch (dph). This was compared with fish of the same batch fed the same basal diet with no PP (CT; negative control) or the same basal diet supplemented with 60 mg MT kg-1 (MT; positive control). To confirm whether the sex change was complete, fish in all treatments were fed only a basal diet for an additional 84 days. The associated differences in the growth of the fish were also determined. Pine pollen and MT significantly skewed the expected 50:50 (male: female) ratio towards more male individuals (Chi-square: X2 = 54.396, df = 9, P < 0.001). The 1,280 mg PP kg-1 of diet equally induced masculinisation (80.0 ± 2.9 % males) as MT (89.2 ± 2.2 %), and both were significantly higher than 50.8 ± 2.2 % in the CT treatment. In addition to masculinization, dietary inclusion of 1,280 mg PP kg-1 improved fish growth, with the specific growth rate significantly higher than fish from the MT and CT treatments (One-way ANOVA: F(9, 20) =14.196, P < 0.001). An increment in the dietary levels of PP from 1,280 to 3,200 mg kg-1 further promoted the growth of the fish but did not affect masculinisation. The mechanism underlying PP-induced sex masculinisation was investigated using all-female Nile tilapia fed a basal diet supplemented with 1,280 mg PP kg-1 for 28 days from 3 dph, in comparison with fish fed a basal diet incorporated with 60 mg MT kg-1 (MT treatment) or only a basal diet (CT treatment). The expression of sex-related genes (dmrt1, amh, cyp19a1a, and foxl2), changes in sex steroid profiles (T: testosterone, 11-KT: 11-ketotestosterone, and E2: 17β-estradiol), and gonadal histology were analysed. Gene expression and sex steroid concentrations were significantly influenced by the interaction between dietary treatment and time, with the expression changing differently over time among the treatments (RM-ANOVA: P < 0.001). Pine pollen significantly up-regulated the expression of dmrt1 and amh, while cyp19a1a and foxl2 were down-regulated. Corresponding to male sex gene up-regulation, male-based steroids (11-KT and T) levels were also significantly amplified in both PP and MTtreated fish. The gene expression pattern and changes in sex steroids corresponded to a higher proportion of male individuals obtained in the MT and PP treatments (MT: 97.8 ± 1.1 % and PP: 77.8 ± 2.9 % males), implying female-to-male sex change induction. Subsequently, spermatogonia and spermatocytes were the dominant germ cells in the histological sections of the gonads obtained from the PP-treated fish. At the same time, the individuals from the MT treatment exhibited mainly spermatids and spermatozoa. In contrast, all the fish from the CT treatment remained females, having only ovarian tissues. This thesis confirmed that PP induces female-to-male sex change in Nile tilapia and enhances fish growth. The research contributed novel information on the mechanism underlying PP induced sex change, which included disrupting the expression of sex genes and the androgento- estrogen balance, ultimately determining the sexual fate of the fish. The findings provide a foundation for understanding the role of PP in masculinisation, with broad potential application in the aquaculture industry. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
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  • Date Issued: 2023-10-13

Massed prolonged exposure therapy for PTSD and alcohol use: a single case experimental study of a university student

  • Authors: Abrahams, Sherwin Owen
  • Date: 2025-04-25
  • Subjects: Prolonged exposure therapy , Post-traumatic stress disorder , Alcoholism , Flooding , College students Alcohol use South Africa , College students Psychology
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/478284 , vital:78173
  • Description: Post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD) are common among university students in South Africa. Bantjies et al. (2023) found a PTSD prevalence of 21.0% (n=28,268), and McGowan and Kagee (2013) reported that 90% (n=1337) had experienced at least one traumatic event. There is a high comorbidity between PTSD and AUD, especially in hazardous drinkers (Peltzer & Pengpid, 2015). Despite the prevalence, research on effective trauma-focused therapies (TFTs) in low-resource settings is limited (Booysen & Kagee, 2021). This study evaluates the effectiveness of massed-prolonged exposure (MPE) therapy for comorbid PTSD and AUD among South African university students, using a Single-Case Experimental Design (SCED). The participant (n=1) underwent comprehensive assessments using CAPS-5, AUDIT, PDS-5, and PCL-5, confirming PTSD and AUD diagnoses. Regular PCL-5 assessments during the intervention showed significant symptom improvement, and post-intervention assessments indicated the participant no longer met PTSD criteria. AUDIT scores also improved from 11 (harmful/hazardous drinking) to 6. The participant found MPE therapy to be feasible, acceptable, and appropriate. This study supports the effectiveness, feasibility and acceptability of MPE therapy and highlights the importance of evidence-based interventions to improve PTSD outcomes within university settings and in low-to-middle-income countries. , Thesis (MA) -- Faculty of Humanities, Psychology, 2025
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  • Date Issued: 2025-04-25

Exploring the diverse racialised responses to the ‘Ashwin Willemse incident’ through theories of race and coloniality of being

  • Authors: Accom, Abner
  • Date: 2022-10-14
  • Subjects: Willemse, Ashwin, 1981- , Ethnic attitudes South Africa , Race awareness South Africa , Postcolonialism South Africa , South Africa Race relations , Decolonization South Africa , Racism in sports South Africa
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/405908 , vital:70218
  • Description: On 19 May 2018 Ashwin Willemse, a coloured Springbok rugby player walked off the SuperSport set, a DSTV sports program, during a live broadcast. He accused his white co-hosts Nick Mallet and Naas Botha (two white apartheid-era Springboks) of patronising him (SABC News, 2018; Eyewitness News, 2018). Responses to the Willemse incident reflected racial divisions in the country. It appeared that many white South Africans criticised Willemse’s behaviour, while many black South Africans stated that they could identify with his response to the subtle racisms experienced in everyday life, and which he claimed to have experienced on the SuperSport program (SABC News, 2018; Eyewitness News, 2018). The racialised media outcry led Professor Jonathan Jansen, to ask: “why do two groups of people, staring at the same event ‘see’ two different realities” (Maleka, 2018: 4)? This thesis probes possible answers to Jonathan Jansen’s question regarding the Ashwin Willemse walkout. The thesis explores and analyses the diverse racialised responses to the ‘Willemse walkout’ through race theories and ‘coloniality of being’. Qualitative research methods were used in the form of a reception analysis involving two racially homogenous (black and white) focus group interviews, two in-depth individual interviews with black research participants, three in-depth individual interviews with white research participants, and a sample of tweets from black and white commentators who had opinions about the ‘Willemse walkout’. The thesis concludes that most black research participants supported Willemse’s actions and most of the white people in the group disagreed with Willemse’s behaviour. Their various opinions were largely due to their different lived experiences which were a consequence of South Africa’s colonial history, apartheid, and racial discrimination. , Thesis (MA) -- Faculty of Humanities, School of Journalism and Media Studies, 2022
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  • Date Issued: 2022-10-14

A social realist analysis of the professional identity formation of lecturers emerging from completing professional development at a South African research-intensive university

  • Authors: Adams, Anthea
  • Date: 2024-10-11
  • Subjects: Identity (Psychology) in education , Academic development , Staff development , Social realism , Critical realism , Scholarship of teaching and learning , Education, Higher South Africa
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466372 , vital:76722 , DOI https://doi.org/10.21504/10962/466372
  • Description: This doctoral study is part of a Department of Higher Education and Training (DHET) capacity development project, Phakamisa. Using Margaret Archer's Social Realism as a substantive theory and methodological tool and Roy Bhaskar's Critical Realism as a meta-theory, I was able to identify and explain the interplay between the structural, cultural and agential mechanisms within a professional development course that enabled or constrained the emergence of lecturers' professional academic identities. My research participants are fourteen lecturers who completed the Postgraduate Diploma in Higher Education (PGDip HE) at Rhodes University between 2007 and 2017. Social Realism's explanatory methodologies, analytical dualism, and the morphogenetic cycle allowed me to provide causal explanations and account for the historicity of the emergence of lecturers' professional academic identities as teachers. A qualitative research design involving case study research allowed me to search for generative mechanisms to understand and explain the conditioning influence of often unobservable phenomena and underlying mechanisms in developing lecturers' identities as teachers in a research-intensive university. As strong social actors imbued with power and material resources, university leadership should consider the constraining influence of contextual conditions, such as the hegemony of disciplinary research versus research in the Scholarship of Teaching and Learning (SoTL). The socio-cultural (S-C) interactions of the fourteen lecturers (agents) signal the possibilities for structural, cultural and agential morphogenesis when agents choose to exercise their agency, i.e., their personal emergent properties (PEPs) to mediate prevalent structural and cultural emergent properties (SEPs and CEPs) enabling or constraining their personal projects. Lecturers' personal projects are the courses of action they intentionally engage in as they strive to establish sustainable yet evolving practices as teachers in their disciplines. This thesis shows that exercising their PEPs involves subjective reflexivity and transforming from primary agents to corporate agents due to collective action and alliances with like-minded peers and colleagues to shape the teaching and learning agenda in their respective departments and the broader higher education context. Triple morphogenesis of lecturers' agency occurred through their realisation as social actors. It signified the formation of their professional identities as teachers and how they uniquely embodied and enacted their teacher roles. , Hierdie doktorale studie is deel van 'n Departement van Hoër Onderwys en Opleiding (DHOO) kapasiteitsontwikkelingsprojek, naamlik Phakamisa. Deur gebruik te maak van Margaret Archer se Sosiale Realisme ("Social Realism") as 'n substantiewe teorie en metodologiese instrument, en Roy Bhaskar se Kritiese Realisme ("Critical Realism") as 'n metateorie, was ek in staat om die wisselwerking tussen die strukturele, kulturele en agentiese meganismes binne 'n professionele ontwikkelingskursus te identifiseer en te verduidelik wat die ontstaan van dosente se professionele akademiese identiteite moontlik gemaak of beperk het. Die deelnemers in my navorsing is veertien dosente wat die Nagraadse Diploma in Hoër Onderwys (NGDip HO) aan Rhodes Universiteit tussen 2007 en 2017 voltooi het. Sosiale Realisme se verklarende metodologieë, analitiese dualisme en die morfogenetiese siklus het my toegelaat om oorsaaklike verklarings te verskaf en die historisiteit van die ontstaan van dosente se professionele akademiese identiteite as onderwysers te verantwoord. ’n Kwalitatiewe navorsingsontwerp wat gevallestudienavorsing behels het, het my toegelaat om na generatiewe meganismes te soek om die kondisionerende invloed van dikwels onwaarneembare verskynsels en onderliggende meganismes in die ontwikkeling van dosente se identiteit as onderwysers in ’n navorsingsintensiewe universiteit te verstaan en te verduidelik. As sterk sosiale rolspelers deurdrenk met mag en materiële hulpbronne, behoort universiteitsleierskap die beperkende invloed van kontekstuele toestande, soos die hegemonie van dissiplinêre navorsing versus navorsing in die Akademieskap van Onderrig en Leer (AvOL, of in Engels "Scholarship of Teaching and Learning", afgekort na SoTL) in ag te neem. Die sosiokulturele (S-K) interaksie van die veertien dosente (agente) dui op die moontlikhede vir strukturele, kulturele en agentiale morfogenese wanneer agente doelbewus kies om hul agentskap uit te oefen, dit wil sê hul persoonlike ontluikende eienskappe (in Engels "personal emergent properties", afgekort na PEPs) om heersende strukturele en kulturele ontluikende eienskappe te bemiddel (in Engels "cultural emergent properties", afgekort na CEPs) wat hul persoonlike projekte moontlik maak of beperk. Dosente se persoonlike projekte is die aksies wat hulle doelbewus aangepak het terwyl hulle daarna gestreef het om volhoubare dog ontwikkelende praktyke as onderwysers in hul dissiplines te vestig. Hierdie tesis dui aan dat die uitoefening van hul persoonlike ontluikende eienskappe ("PEPs") behels subjektiewe refleksiwiteit en transformasie van primêre agente na korporatiewe agente as gevolg van kollektiewe optrede en alliansies met eendersdenkende eweknieë en kollegas om die onderrigen leeragenda in hul onderskeie departemente en die breër hoëronderwyskonteks te beïnvloed. Drievoudige morfogenese van dosente se agentskap het plaasgevind deur hul verwesenliking as sosiale rolspelers. Dit het die vorming van hul professionele identiteite as onderwysers aangedui en die unieke manier hoe hulle hul onderwyserrolle interpreteer en uitleef. , Thesis (PhD) -- Faculty of Education, Centre for Higher Education Research, Teaching and Learning, 2024
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  • Date Issued: 2024-10-11

A scoping review on problematic Internet use and Substance Use Disorder among men

  • Authors: Adolph, Miché Tania
  • Date: 2024-10-11
  • Subjects: Internet addiction , Substance abuse , Men Mental health , Scoping review protocol , Compulsive behavior Sex differences
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/465788 , vital:76653
  • Description: Problematic Internet Use (PIU) and Substance Use Disorder (SUD) interact in complex ways that influence the current mental health landscape. Concurrently, the advent of the digital era has presented new difficulties, one of which is the emergence of problematic internet use as a significant issue that negatively impacts mental health. The increasing popularity of internet use has led to an increasing number of reports highlighting the potential negative consequences of overuse, such as substance use. Thus, the study aimed to synthesise literature on problematic internet use and substance use disorder, including the way in which they affect men, given that prior research has predominantly focused on women. The methods employed follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) which is largely based on a PRISMA statement and checklist, the JBI methodological guidance, and other approaches for undertaking scoping reviews. A total of 16 studies were eligible for final review, and the themes identified from the reviewed studies were obtained using Braun and Clarke’s thematic analysis. An analysis of the articles showed a large focus on gender differences in addiction patterns, vulnerability to problematic internet use across age groups, associations between substance use and behavioural addictions, problematic internet use and mental health disorders, the psychological consequences of problematic internet use and substance use disorders, and the various risk factors associated with the development of problematic internet use and substance use disorder. A clear understanding and conceptualisation of this behavioural addiction is vital, including the development and utilisation of appropriate and validated diagnostic and screening tools to measure its presence and, in turn, address it as an emerging mental health disorder. Focus should be given to the assessment of problematic internet use by distinguishing the two different forms, namely the generalised and specific forms of problematic internet use. Additionally, given that there were very few to no qualitative studies conducted on the topic of problematic internet use, much less addressing the possible association with substance use disorder, an assessment of the individual’s experience, especially that of men, is lacking. Future research could therefore aim to incorporate more qualitative studies to address the above. Further research is also needed to clarify the nature of the relationship between problematic internet use and substance use disorder for the purpose of establishing possible causality, including the neurobiological substrates involved. , Thesis (MA) -- Faculty of Humanities, Psychology, 2024
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  • Date Issued: 2024-10-11

The exploration of Black and Brown drag performance communities: an artistic tool for creating safe spaces

  • Authors: Adriaan, Aaron Robert
  • Date: 2025-04-25
  • Subjects: Sexual minority culture South Africa , Performance art South Africa , Drag performance South Africa , Intersectionality (Sociology) , Autoethnography , Theater South Africa
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/478383 , vital:78182
  • Description: This research investigates the role of drag performance in South Africa, particularly its contribution to the fostering and maintenance of safe spaces for Black and Brown Queer communities. Inspired by the community building legacy Kewpie. This research project employs auto-ethnographic research practice to generate a better understanding of modes of Queer drag praxis drawing on Linda Tuhiwai Smith's (1999) concept of the "insider/outsider" researcher. The project acknowledges the ethical challenges of researching vulnerable communities. This research is guided by self-reflection and information gathered from fieldwork; informed by an awareness of the theory of ‘intersectionality’ (Carbado, Crenshaw, Mays, Tomlinson 2013) exploring the complexities of race, class, and sexuality within Cape Town’s Queer community. In this way, the study navigates the complexities of race, class, and sexuality within the drag context of Cape Town through the viewpoint of this researcher. The contextual exploration of drag unfolds across two interconnected disciplinary avenues: Firstly, the historical context of drag and its evolution within the performance art canon: to understand the place of contemporary drag in the broader artistic and cultural discourse. Secondly, the study investigates theatrical histories and conventions that have influenced and transformed drag practices. This is done to frame drag performance with forms of theatrical performance. This historical and disciplinary background is used to formulate a distinction that is at the centre of this research: proposing that contemporary drag practice in the City of Cape Town can be understood and to some extent distinguished by the categories of embodied costume and embodied performance. Embodied costume within the scope of this research view the use of drag aesthetics and visual elements in artistic expressions and performances that fall outside of traditional ‘drag show’ culture. Embodied performance refers to drag performances that fall within the context of traditional ‘drag show’ genres, communities, and venues − reminiscent of cabaret performance. This conception highlights the performative aspects of the drag persona, which is an extension of the performer’s identity. While some performers and performances can exemplify either embodied performance or embodied costume, these categories are not mutually exclusive, with incalculable overlaps in keeping with the rich possibilities of drag practice. The purpose of highlighting these distinctions is to create a critical framework for exploring the unique position drag occupies between fine art and theatre, incorporating both fields of practice, and synthesising them into a unique language for the expression of alternate gender narratives. , Thesis (MA) -- Faculty of Humanities, Fine Art, 2025
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  • Date Issued: 2025-04-25

Drifting towards death: a South African patient safety incident through an HFE Systems lens

  • Authors: Agar, Sarah Leigh
  • Date: 2022-10-14
  • Subjects: Patients Safety measures , Medical errors Prevention , Human engineering , Medical care South Africa
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/362716 , vital:65356
  • Description: Patient Safety Incidents (PSI) are a frequent occurrence within the South African public healthcare system wherein a patient is unnecessarily maimed, harmed, killed, or put through significant trauma, emotional or physical. These incidents have a significant impact on the performance of the system and the well-being of individuals involved. Often PSI are the result of multiple system failings that provide the necessary preconditions for the PSI to occur. Thus, to provide appropriate patient safety recommendations to address and aid in the prevention of future PSI it is necessary to apply a systems approach to PSI analysis. A systems approach supports a ‘bigger picture’ view of an incident which includes looking beyond the immediate causes of a PSI and taking the different levels of the healthcare system into consideration during incident analysis. Human Factors and Ergonomics (HFE) is at its core a systems discipline and has been successfully applied to multiple fields including healthcare. HFE offers multiple incident analysis tools grounded in systems theory. The Life Esidimeni incident, a PSI that resulted in the death of 144 MHCU, is the biggest PSI in recent South African history and is therefore an important potential case study for the application of HFE systems tools within the South African healthcare context (an area that is lacking in existing literature). The objectives of this research were to (i) Systematically uncover the causal factors that led to the outcome of the of the Life Esidimeni incident; (ii) Identify critical faults, and gaps within the healthcare system that led to the Life Esidimeni PSI; and (iii) Provide proactive recommendations for future prevention of PSI. To fulfil these objectives a descriptive case study research method design was adopted using a qualitative systems-based tool, AcciMap. The application of AcciMap to Life Esidimeni enabled both the sharp end and blunt end causal factors that contributed to the outcome of the incident to be identified. Importantly this provided insight into the critical faults and gaps of the South African public healthcare system. The results of the AcciMap indicated that there were four main broad systemic faults in the system. These broad areas were categorized as key themes, which include: (i) competency, (ii) safeguards, (iii) time pressures, and (iv) vertical integration. From these key themes recommendations aimed at addressing the critical faults and gaps in the system and preventing future PSI were made. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2022
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  • Date Issued: 2022-10-14

Anonymous testimony and epistemic responsibility

  • Authors: Ajiboro, Aderonke Adeyinka
  • Date: 2023-10-13
  • Subjects: Anonymity , Assertion , Credibility , Truthfulness and falsehood , Responsibility , Testimony (Theory of knowledge)
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/432286 , vital:72858 , DOI 10.21504/10962/432286
  • Description: In this thesis, I examine anonymous testimony in both offline (face-to-face) and online (internet and social media) interactions and the epistemic concerns it raises in relation to belief, knowledge, justification, and normative assessments of assertions. I discuss anonymous testimony as involving a relation between the hearer and the content of the testimony in comparison to ordinary cases where the speaker of an assertion is known. In anonymous testimony, the hearer has the burden of epistemic responsibility to arrive at a testimonial belief or arguably acceptance. The hearer is also accountable for the anonymous testimony in the event of re-assertion. I also assess the norms of assertion for anonymous testimony and argue that knowledge, truth, and belief norms that apply in cases where the speaker is known should not be applied to cases of anonymous speakers. Epistemologists have paid little attention to anonymous testimony and its implications on the norms of interaction. This is a study in the epistemology of testimony and it aims at providing further understanding of the epistemic responsibility of hearers of anonymous testimony. In Chapter One, I argue that anonymous testimony can be appropriately described as testimony; where the properties of an assertion to induce belief in the hearer are sufficient to describe the assertion as testimony. I examine the kinds of anonymity and the burden of epistemic responsibility for the hearer. I introduce basically anonymous testimony in offline and online contexts of interaction. A basically anonymous testimony occurs where, at the instance of receiving testimony and making an epistemic decision on it, the speaker is unidentifiable to the hearer. In Chapter Two, I discuss the kinds of epistemic attitudes hearers may have when they receive anonymous testimony. I discuss reductionism, antireductionism, and entitlement theory as accounts of the justification for believing testimony. I argue that acceptance is the appropriate attitude and the entitlement theory provides a basis for accepting anonymous testimony. I also argue that practical reasons are a sufficient to accept anonymous testimony. Also, I discuss the possibility that a hearer of anonymous testimony can make a wrongful presumption by assigning an identity to a person as the speaker of an anonymous testimony. This can cause harm to the ‘person’ of the presumed speaker such as an unwarranted credibility assessment of the person by other people in the community. I also argue that making a credibility assessment of a presumed speaker constitutes harm to a proper epistemic assessment of the content. In Chapter Three, I discuss the possibility of trust relations between an anonymous speaker and a hearer. I argue that the hearer is solely responsible for making an epistemic decision from anonymous testimony. I argue that anonymous testimony can be relevant to a hearer given the value of its content. In Chapter Four, I discuss the applicability of knowledge, truth, belief, reasonable to believe and supportive reasons norms for the re-assertion of anonymous testimony. Hence, I argue that the supportive reasons norm, which acknowledges acceptance of an assertion, the relevance of contexts, and admits both epistemic and practical reasons to make an assertion, should guide the re-assertion of anonymous testimony. I also argue that a hearer should be epistemically conscientiousness for responsible re-assertion of received anonymous testimony. , Thesis (PhD) -- Faculty of Humanities, Philosophy, 2023
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  • Date Issued: 2023-10-13

The impact of Ghana's entrepreneurial ecosystem on women's entrepreneurial performance: the moderating role of entrepreneurial identity

  • Authors: Akuamoah Boateng, Irene
  • Date: 2025-04-02
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/479559 , vital:78324 , DOI 10.21504/10962/479559
  • Description: Women business leaders are generating a tremendous impact in their markets, industries and communities through innovation, job creation and economic growth. However, their contributions are often lost in the prevailing narrative that women are over-represented among the poorest and most vulnerable entrepreneurs globally. A review of the extant literature has postulated challenges that women entrepreneurs faced several challenges in the ecosystem in which it operates. Women entrepreneurs have access to limited capital as compared to its men counterparts, fewer opportunities to network and build relationships with other entrepreneurs, investors, and mentors, which affects their access to resources and knowledge. Due to the issue of gender-based stereotypes and biases that women entrepreneurs constantly face, they are unable to meet mentors who can provide them with guidance and support to grow their business. These women-specific challenges have become barriers limiting the growth of women entrepreneurs, however insufficient reports highlight how these hindering factors can create opportunities for the growth of women entrepreneurs. Dwelling on the Process theory, the study explored the impact of Ghana’s entrepreneurial ecosystem on women’s entrepreneurial performance with the moderating role of entrepreneurial identity. The study was a cross-sectional quantitative research design with data collected from 413 women entrepreneurs in the Greater Accra Region using structured questionnaire collected using the survey monkey online tool. The data was analyzed using IBM SPSS v.25 and the PLS-SEM v.4.0. The first objective was examined through 12 hypotheses, while the second was analyzed using 2.The study finds that access to finance has positive and insignificant effect on the entrepreneurial performance of women in Ghana. Likewise, education and training have a negative and insignificant effect on the market and operational performance of women entrepreneurs in Ghana. The results of the study postulated that the availability of infrastructure and resources has a negative but significant effect on both the market and operational performance of Ghanaian women entrepreneurs. The results of the study further reported a positive but insignificant impact of network and social capital on the market performance and operational performance of women entrepreneurs in Ghana. The results of the study in relations to the regulatory environment and women entrepreneurial performance indicates an insignificant relationship between regulatory environment and market performance and regulatory performance whilst cultural and social factors within the Ghanaian ecosystem negatively but significantly influence the entrepreneurial performance of women in Ghana but innovation and knowledge spillover have a positive and significant impact on both the market performance and operational performance. Furthermore, the findings of the study suggest that Ghana's entrepreneurial ecosystem may not have a substantial direct impact on women's entrepreneurial performance in Ghana. Further practical and theoretical implications of the study are discussed in the thesis. , Thesis (PhD) -- Faculty of Commerce, Rhodes Business School, 2025
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  • Date Issued: 2025-04-02

The memory altar

Macroplastics in the environment: are they suitable habitats for macroinvertebrates in riverine systems?

  • Authors: Ali, Andrew Abagai
  • Date: 2023-10-13
  • Subjects: Macroplastics , Aquatic invertebrates South Africa Eastern Cape , Experimental ecology , Plastic scrap , Environmental degradation , Functional ecology , Biotic communities
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424153 , vital:72128
  • Description: Emerging pollutants, such as plastics are threat to freshwater ecosystems, and may negatively impact riverine systems. They can modify riverine habitats and affect aquatic organism distribution and composition. Knowledge of how macroplastics alter riverine habitat heterogeneity, and their effects on macroinvertebrate assemblage structure is sparse, especially in Africa. This study examines the effect of hydraulic biotopes on the colonisation, establishment and succession patterns of macroinvertebrates on macroplastic and natural substrates based on the taxonomic and trait-based approach. Four experimental sites from minimally impacted upper reaches of the Buffalo, Kat, Kowie, and Swartkops Rivers in the Eastern Cape of South Africa were selected for the deployment of plastic substrates. Plastics materials, including polyethylene terephthalate (PET) bottles and natural substrate composed of stone and vegetation, were used to formulate three substrate groups: Group 1: 100% natural substrates (NS), Group 2: 50% natural substrates and 50% plastic material (NP), and Group 3: 100% plastic materials (PD). These substrates were placed in litter bags of equal dimension (25 cm by 35 cm, with 2.5 cm mesh) and deployed randomly in three hydraulic biotopes (pools, riffles, runs) over a period of 180 days (October 2021 to April 2022). A total of 216 substrate bags, 54 bags per substrate were deployed per site in the four experimental sites. Twelve bags from each substrate group were retrieved at an interval of 30 days beginning on day 30 after deployment, and analysed for the establishment of macroinvertebrate communities. Based on composite hydraulic biotope data, Simpson index was significantly higher (P < 0.05) for macroinvertebrate assemblage structure on the 50% and 100% macroplastic substrate groups compared to natural substrates. With the exception of Tabanidae, Glossosomatidae, and Psephenidae, all macroinvertebrate taxa recorded showed non-significant positive correlations with all three substrate groups. However, Tabanidae, Glossosomatidae, and Psephenidae showed significant positive correlation with the 100% natural substrates, 50% plastic substrates and 100% plastic substrates, respectively. The parsimony analysis reveal that, within 30 days, all substrate groups underwent similar succession, with high abundance of pioneer taxa which increased on days 60 and 90, and then decreased from days 120 to 180. For the the pool biotope, Shannon and Simpson indices were significantly higher (P < 0.05) for the macroinvertabrates collected over the natural substates compared with those collected on the macroplastic substrate groups. However, in the riffle and run biotopes, all diversity indices were similar for all substrate groups and no statistically significant difference was observed. Statistically significant higher values for taxonomic richness, diversity, and evenness were found on day 30 to 90 for the riffle biotopes, and day 30 to 60 for the run biotopes. The run biotope presented temporal statistical significant variability in taxonomic composition with different macroinvertebrate communities recorded on days 30 and 60 compared with days 90 to 180. However, in pools and riffles, no temporal variation was observed in the taxonomic composition of macroinvertebrates on all three substrate groups. The trait-based fuzzy correspondence analysis revealed differential spatial-temporal distribution of macroinvertebrate traits on all three substrate group. The early colonisers i.e. day 30 – 60, were dominated by group of taxa characterised by medium (>10 – 20 mm) and large (20 > 40) body size, flat body, collector-gatherers, free-living, and predators. The late colonisers, collected mainly on day 150 and 180 were dominated by taxa with a preference for high flow velocity (0.3 - 0.6 m/s), permanent attachment, and filter-feeding mode. Traits such as oval and flat body shape, medium body size (>10 - 20 mm), skating and clinging/climbing mobility, temporal attachment, shredders, predators, prey, and plastron and spiracle respiration showed positive correlation with the 100% macroplastic substrates. Filter feeding, crawling, permanent attachment, a preference for fast velocity (0.3-0.6 m/s), and coarse particle organic matter were positively correlated with the 50% macroplastic substrates. Overall, the results provided critical insights on the impact of macroplastics on the assemblage structure of biological communities by acting as suitable habitats in stream ecosystems. The study elucidated the role of traits of aquatic organisms in mediating the colonisation of plastics substrates, providing insights into the impact of plastics proliferation on riverine ecosystem functioning. Furthermore, the finding provides a baseline insight into the influence of hydraulic biotopes on the colonisation and establishment of macroinvertebrates on macroplastic acting as artificial riverine habitat. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2023
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  • Date Issued: 2023-10-13

Associations between contraceptive use, physical activity, depression, and quality of life among women of childbearing age in Akure South Local Government area of Ondo State, Nigeria

  • Authors: Alimi, Olabisi Ganiyat
  • Date: 2023-10-13
  • Subjects: Exercise for women Nigeria Ondo State , Depression in women Nigeria Ondo State , Well-being Nigeria Ondo State , Quality of life Nigeria Ondo State , Contraception Side effects
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424210 , vital:72133
  • Description: Background: Population experts and policymakers are concerned about Nigeria's rapid annual population growth due to the country's high birth rate which was 5.3 births per woman in 2018. Fear of the side effects of modern contraceptives among Nigerian women contributes to the low rate of contraceptive use, which was reported to be 17% and 37% among married and sexually active unmarried women, respectively. Which is a significant cause of the high birth rate. Although the side effects of modern contraceptives on women's clinical and physiological variables are well known, studies examining the associations between contraceptive use and physical and psychosocial variables such as physical activity (PA), depression, and quality of life (QoL) in non-athletic Nigerian women of reproductive age are scarce. This study aimed to examine the associations between contraceptive use, PA, depression, and QoL among non-athletic women of childbearing age in Akure South Local Government, Ondo State, Nigeria. Methods: In a descriptive cross-sectional study, 646 women of childbearing age were recruited using the multistage sampling technique. The data of 496 current contraceptive users and 146 non-users were analysed, as 4 respondents did not respond regarding current contraceptive use status. The Global PA Questionnaire (GPAQ), Beck’s Depression Inventory (BDI) and World Health QoL Organization Quality of Life Brief (WHOQoL BREF) were used to assess respondents’ scores/levels of PA, depression and health-related quality of life (HRQoL). The GPAQ, BDI, and WHOQOL scores were compared between contraceptive users and non-users using non-parametric Quade Analysis of Covariance while age, married status, tribe, religion, and occupation were included covariates. PA, sedentary behaviour (SB), and BDI scores were categorized using guidelines. Contraceptive use/practice was the outcome variable. Pearson's chi-square test bivariate analysis and a multivariate logistic model were used to identify factors associated with contraceptive use (users and non-users). Crude and adjusted odds ratios and their confidence intervals were calculated to determine the significance of the association. The regression model was adjusted for age, marital status, religion, tribe, highest education level, occupation, awareness of contraceptives, current use, lifetime use, type, class, and duration of current contraception. “Statistical significance was set at p < 0.05. Results: The mean age of the respondents was 29.73±6.10 years. The contraceptive users and non-users were not significantly different regarding their ages (p = 0.135), marital status (p = 0.245), highest education (p = 0.444), occupation (p = 0.238), and tribe (p = 0.192). The respondents’ lifetime and point prevalence of contraceptive uptake was 93.6% and 77.3%, respectively, while 72 (12.8%) reported experiencing contraception-related side effects. Of the 496 respondents who currently practice contraception, 146 (29.4%) were hormonal contraceptive users. The majority of the respondents had moderate and mild levels of PA (48.5%) and depression (51.4%), respectively, and a significantly higher proportion of contraceptive users had minimal and moderate depression levels than the non-users (p = 0.018). The contraceptive users demonstrated significantly higher median scores of BDI (p = 0.02), Physical health QoL (p < 0.001), environment QoL (p = 0.033) and overall QoL (0.004) than the non-users. Hormonal contraceptive users had significantly higher median PA walking/bicycling scores than non-hormonal users (p = 0.014). Respondents with mild and moderate depression levels had higher odds of being contraceptive users than those with minimal depression (AOR = 3.12, 95% CI = 1.43 – 6.80, p = 0.04 and 4.67, 95% CI = 1.92 – 11.36, p = 0.001 respectively). Conclusion: Contraceptive use is negatively associated with depression but positively related to Physical health, environment and overall domains of HRQoL. Healthcare professionals should consider women's mental and emotional condition while advising on family planning for optimal HRQoL. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2023
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  • Date Issued: 2023-10-13

A social realist analysis of health policy development: interests, ideas and community pharmacists

  • Authors: Allan, Lucie
  • Date: 2024-10-11
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/466328 , vital:76718
  • Description: Access restricted. Expected release in 2026. , Thesis (PhD) -- Faculty of Pharmacy, Pharmacy, 2024
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  • Date Issued: 2024-10-11

Thermal physiology of juvenile red roman seabream, Chrysoblephus laticeps after long-term exposure to low pH conditions

  • Authors: Allison, Caitlin
  • Date: 2023-10-13
  • Subjects: Climatic changes , Ocean acidification , Basal metabolism , Chrysoblephus laticeps , Thermal tolerance (Physiology) , Phenotypic plasticity , Fishes Climatic factors
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424323 , vital:72143
  • Description: Climate change has caused a combination of effects on the physiology of fishes. Of particular concern are the effects of thermal variability and ocean acidification. Organismal energy budgets change throughout ontogeny and research into the metabolic scope during early life stages is particularly useful in identifying potential bottlenecks. The first part of this thesis aimed to assess the absolute aerobic scope (AAS, described as the difference between the maximum and standard metabolic rates) of individual juveniles from a protected population of the endemic, commercially important seabream, Chrysoblephus laticeps, across a range of ecologically relevant temperatures (T = 11, 14, 18, 22˚C) under present-day conditions (pH = 8.03, pCO2 ≈ 420 μatm) using intermittent flow respirometry. The second component sought to investigate how long-term exposure (from fertilisation to juvenile, ~100 days exposure) to high-pCO2/hypercapnic conditions (pH = 7.63, pCO2 ≈ 1400 μatm), would affect the AAS of juvenile C. laticeps over a range of temperatures. Lower pH conditions were predicted to cause a decrease in the AAS of treatment animals due to additional energetic costs of acid-base regulation. The findings of the first data chapter demonstrated that juvenile C. laticeps reared under current CO2 conditions are tolerant to a wide range of thermal conditions, and individuals with a broad aerobic scope will be the best suited to coping with enhanced thermal variability. In contrast to the expected outcomes of the second data chapter, juvenile C. laticeps reared under high pCO2 conditions displayed greater AAS at high and low temperatures when compared with specimens from high pH conditions. Whilst a high degree of individual phenotypic variation was observed in the metabolic response of both groups, this was reduced at the lower and upper extreme temperatures for high pH and low pH animals respectively. Notably, the variation in treatment animal’s SMR was significantly diminished across all temperatures tested, compared to only a localised reduction in the SMR of high pH animals at cold temperatures. This may be indicative of compensatory pathways affecting energy restructuring and thermally-governed physiological trade-offs under hypercapnia. Given these results, juvenile C. laticeps appear to be more resilient to ocean acidification than anticipated, potentially owing to intrapopulation metabolic phenotypic diversity. This is likely attributed to the parental lineage originating in the Tsitsikamma MPA, which is thought to boast greater phenotypic diversity as a consequence of the refuge that these conservation areas offer from exploitation. Owing to the restriction imposed by the availability of surviving, captive-reared juveniles, the sample size used in this study was relatively low. However, owing to the repeated-measures nature of this research the sample size was sufficient to offer suitable statistical power for the polynomial mixed model used in the analysis. Future research should incorporate both physiological and behavioural responses to multiple environmental stressors to better understand covariation between these two traits, and to detect any behavioural trade-offs that might arise through compensation. In addition, these trials should be repeated using offspring from outside of the MPA to compare whether the same level of resilience and metabolic phenotypic diversity would be present in an exploited population. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
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  • Date Issued: 2023-10-13

Exploring ESL teachers’ self-developed pedagogical practices for teaching reading comprehension in Namibian primary schools

  • Authors: Alumbungu, Marta Ndakalako
  • Date: 2023-10-13
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/419714 , vital:71669
  • Description: Embargoed. Possible release date 2026 pending publication. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2023
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  • Date Issued: 2023-10-13

Exploring self-directed continuous professional development for English Language teachers in selected Namibian secondary schools

  • Authors: Amakutuwa, Hilma Ndesheetelwa Mwalengwa
  • Date: 2024-10-11
  • Subjects: English language Study and teaching Namibia , English teachers Namibia , Continuing professional development , Self-managed learning , Reflective practice
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/463538 , vital:76418
  • Description: Continuous professional development (CPD) for teachers, with all its diverse notions, has been noted and articulated in various policy documents in Namibia, and is understood as in-service training and professional development for teachers to improve learning outcomes. In Namibia, challenges have been experienced with the performance of learners in English as a Second Language (ESL) at the national level, and teacher professional development could be one way of changing the status quo. However, in answer to the call from the Namibian Ministry of Education Arts and Culture for a more idiosyncratic orientation, limited literature was found on how ESL teachers use self-directed learning (SDL) to shape their CPD activities. Thus, the purpose of this study was to address this gap by exploring the self-directed CPD needs of English Language teachers in selected Namibian secondary schools. The study was oriented to theoretical insights from SDL, reflective practice and social constructivism. Through the use of a qualitative approach, the study employed an exploratory case study research design. Semi-structured interviews and focus group discussions were used to generate data from eight selected Grade 8 to 12 ESL teachers in the Khomas region of Namibia. The data gathered were analysed using an inductive thematic framework. The findings of the study indicate that ESL teachers are faced with a myriad of challenges ranging from classroom experiences, the type of learners they work with and the support system available at school, regional and national level. The study found that due to changing education paradigms, ESL teachers need to broaden their knowledge base in specialised education and systematic professional interventions at school level. They indicated that this would help learners with challenges in reading, writing and comprehension to improve their skills in ESL classrooms. They further emphasised the necessity for mentors, education specialists, systematic schools and circuit based collaborative CPD, as well as more support from school heads and regional ESL senior education officers, which is an area that is inadequately managed. Finally, they pointed out that in order to make their ESL classes engaging and enjoyable, teachers needed to have a strong foundation in ICT education. This foundation can be leveraged to create resources that are now lacking. The findings have implications for ESL teachers, school administrators, education specialists and policymakers, as they provide insights and recommendations for enhancing ESL education practices. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
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  • Date Issued: 2024-10-11

The impacts of anthropogenic fires in West African savanna woodlands and parklands: the case of the Guinea savanna, Ghana

  • Authors: Amoako, Esther Ekua Amfoa
  • Date: 2022-10-14
  • Subjects: Firemaking Ghana , Agroforestry Ghana , Parks Fire management Ghana , Nature Effect of human beings on Ghana , Land use Ghana , Savanna ecology Ghana , Traditional ecological knowledge Ghana
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/365610 , vital:65764 , DOI https://doi.org/10.21504/10962/365610
  • Description: Fire is recognised as an important factor influencing the structure and function of tropical savannas. Despite the extensive studies conducted on the effects of fire on global savannas, there are relatively few studies focusing on fire-assisted land use practices in the agroforestry parkland of the Sudano-Guinean savannas of West Africa. The region experiences recurrent fires in the dry season which begins from November to April. The fires are anthropogenic and are mainly caused through rural livelihoods and cultural practices such as farming - to remove debris from crop fields and to improve soil fertility and hunting to flush out animals, among other reasons. This study therefore sought to: 1. contribute to the understanding of fire-assisted traditional land use practices, people’s knowledge and perceptions of fire use and fire regime: 2. analyse the effects of fire on vegetation, and 3. determine the effects of fire on soils in the Guinea savanna woodlands and parklands of Ghana. Study sites (burnt and unburnt land use types) were selected based on five-year daily fire counts (2013-2017) data, obtained from the Earth Observation Research and Innovation Centre (EORIC), Ghana in collaboration with the Council for Scientific and Industrial Research (CSIR) Meraka Institute, South Africa. Fire densities were calculated for the 18 districts in the Guinea savanna (Northern Region of Ghana). The districts were stratified into low, medium and high fire frequency areas. The East Gonja district recorded the highest fire density (1.0 fires km-2) while Tamale recorded the lowest fire density (0.3 fires km-2). Of the eighteen districts, six districts were purposively selected and ten communities sampled. Firstly, I investigated the frequency of fire use and control, perceptions of fire regime for selected livelihood and socio-cultural activities in the six districts. The majority of respondents (83%) across the study districts indicated that they used fire once a year for at least one of the following activities: land preparation, weed/grass/pest control, burning stubble after harvest, bush clearing around homesteads, firebreaks, charcoal burning and hunting. The study showed the highest frequency of fire use in the dry season was for land preparation for cropping. However, less than a fifth of the respondents (17%) indicated that they did not use fire for any of the above activities. The results of a multiple regression predicted fire activities in the dry season from gender, age, level of education, occupation and household size. Secondly, the study examined how fire influenced the population structure and abundance of two economically important woody species Vitellaria paradoxa C. F. Gaertn. (Shea tree) and Anogeissus leiocarpa (DC.) Guill. & Perr. (African Birch) in burnt and unburnt land-use types. Stand basal area, mean densities of juveniles and adult trees and Simpson’s index of dominance were determined. Eight diameter size classes of each species were analysed by comparing their observed distributions to a three-parameter Weibull distribution across the land use types. A total of 3,366 individuals of A. leiocarpa (n = 1,846) and V. paradoxa (n = 1,520) were enumerated. The highest total basal area of Anogeissus leiocarpa (16.9 m2/ha) was estimated in sacred groves whereas Vitellaria. paradoxa (20.6 m2 /ha) was found in unburnt woodland. The highest mean densities of A. leiocarpa (22.7±29.7 stems/ha) and V. paradoxa (15.3±2.2 stems/ha) were found in sacred in groves. Anogeissus leiocarpa was, however, absent in fallows and burnt crop fields. A somewhat inverse J-shaped distribution was found in sacred groves for both species. Thirdly, the study compared species composition in early burnt, late burnt and unburnt plots in a protected area where fire was regulated. Vitellaria paradoxa C. F. Gaertn., Terminalia avicennioides Guill. & Perr., Combretum adenogonium Steud. ex A. Rich. and Combretum molle R. Br. Ex. G. Don. were the most common and abundant in all treatments. Late burnt and unburnt plots recorded the lowest diversity amongst the three treatments. Unburnt plots had higher tree density than burnt plots. A Detrended Canonical Analysis showed a changing trend, indicating a moderately strong positive association between burning time and species composition. The first and second axes contributed 53% and 12% variation, respectively. Most of the species found in axis one had fairly strong positive association to early and late burnt treatment than unburnt treatments. Finally, the effects of fire on soil properties in burnt and unburnt crop fields and woodland in the ten communities were also investigated. A total of 151 composite samples in selected burnt and unburnt land use types (burnt crop field n=20; unburnt crop field n=27; burnt woodland n=53, unburnt woodland n=51) were analysed. The variables analysed were pH, soil organic carbon (SOC), total nitrogen (TN), available phosphorous (P), Exchangeable bases - potassium (K), magnesium (Mg), calcium (Ca), cation exchange and soil texture. Total N, SOC, pH and Ca differed significantly across the burnt and unburnt land-use types. A principal component analysis showed a stronger association and more positive gradient in woodlands than in crop fields. Total N showed a positive association with SOC, whereas silt showed a negative association to sand and clay. Traditional knowledge and perceptions of users of savanna agroforestry parklands can inform the formulation of local by-laws for community fire management as well as national policy regulation on fire use in the savanna through the interlinked analysis of social and ecological systems as have been elucidated in this study. The results on vegetation assessment revealed that fire practices and land uses influenced size class distribution of the two study species as well as the densities of woody species in traditional crop fields and the National Park. The unstable populations observed in most land uses and the absence of A. leiocarpa in crop fields and fallows call for education and policy actions on the use of fire in parklands of West Africa. Furthermore, fires positively influenced some soil properties in both woodlands and crop fields confirming one of the emphasised reasons why rural subsistence farmers use fire. As an environmental management decision and land use policy intervention, early dry season burning could be an option to curbing the indiscriminate and unplanned fire use. Also, the protection of trees on farm lands could check the unstable population structure of economically important woody species leading to the different structures that deviated from the recommended reverse J-shaped distribution curve observed in these agroforestry parklands. The management of socio-ecological systems such as the agroforestry parklands of West Africa require a holistic understanding of the complexity of the different resource systems, units and actors involved for sustainable management of these natural resources. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2022
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  • Date Issued: 2022-10-14

Meerkat polarimetric observations of Pictor A

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

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

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

The morphogenesis of higher education leadership: a social realist exploratory journey

  • Authors: Andrews, Ruth
  • Date: 2023-10-13
  • Subjects: Educational leadership South Africa , Education, Higher South Africa , Critical realism , Social realism , Educational change South Africa , Transformational leadership
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/442897 , vital:74051 , DOI 10.21504/10962/442897
  • Description: The purpose of the study underpinning this thesis was to explore the tensions experienced by university leaders as they balance politics, power and the academic project whilst pursuing their ultimate concerns in the world. Universities are undergoing constant change, particularly in the present time of hypercomplexity, where the discourses of globalisation and neoliberalism condition higher education institutions and their leaders. This predisposes universities to operate as a market economy rather than as a public good. University leaders are under immense pressure as they seek to reposition themselves and exercise their agency in steering their institutions in a landscape fraught with complexity and contestation about the very nature of the modern university. The study was located in a traditional university in South Africa, which added another layer of complexity given the history of Apartheid and, the use of education as a means of discriminating against the black majority population, and the subsequent attempts by the government to transform the system following the first democratic election of 1994. Bhaskar’s (1989) critical realism and Archer’s (1998, 2000) social realism were used to frame the study theoretically. Bhaskar argues for the understanding of the world as an ‘open system’ in which experiences and events emerge from the tendential interplay of mechanisms at a layer of reality not directly accessible to empirical observation. Archer’s (2000) social realism draws on critical realism to provide a set of tools that allows an exploration of the social world in more detail. This study draws on the tools of analytical dualism, or the temporary separation of structure, culture and agency for analytical purposes, and Archer’s (1998) morphogenetic framework, which allows for the exploration of change, or non-change, over time. The overarching goal of the study was to explore how leaders at one South African university were enabled and constrained as they exercised their agency in the pursuit of projects they had identified to address their ultimate concerns about the world more generally and higher education in particular. However, the study also sought to explore the construct of leadership itself in a specific context by using Archer’s (2007, 2012) theoretical work on reflexivity. The study drew on in-depth interviews with senior leaders at the institution, including two vice-chancellors. The interviews were subjected to analysis, and the inferential tools of abduction and retroduction were used to identify the interplay of mechanisms located at the level of the Real, the deepest layer of reality posited by Bhaskar (1978), which led to the events and experiences reported by leaders. A literature review was used to identify additional theories that were used in the processes of abduction and retroduction. The study revealed that change, or rather non-change, is often concealed in cultural rhetoric veiled in leadership practices in acts assimilating past ideology and codified rules and practices with new codified rules and practices. Leaders often draw on powerful relational networks as they reflexively exercise their agency, and these networks can also work to constrain change. , Thesis (PhD) -- Faculty of Education, Education 2023
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  • Date Issued: 2023-10-13
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