PhD / Doctoral

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    Open Access
    What drives private equity performance in emerging markets? An African perspective
    (2025) Cata, Olwethu; Toerien, Francois
    Despite the increasing amounts of capital being dedicated to the asset class, few attempts have been made to evaluate Private Equity (PE) returns in emerging markets and for Africa specifically. Understanding the risk factors associated with PE returns in emerging markets and whether institutional investors can expect adequate compensation for accepting such risks is important to optimal asset allocation. This thesisinvestigates PE performance using a novel dataset of 250 portfolio investments made and exited by 28 General Partners (GPs) across 52 funds in Africa over the period 1996 to 2019. It addresses the following four research questions: (1) How has PE in Africa performed relative to public markets? (2) Is the performance achieved by GPs on the continent persistent? (3) What determines the holding periods of PE investments on the continent? (4) How do macroeconomic conditions impact PE returns on the continent? In doing so, the study makes a significant original contribution to the literature on PE performance by providing new evidence from a minimally investigated region and contributes insights that have practical significance for the capital allocation strategies of institutional investors allocating to PE funds on the continent. The contributions are made in four sequential studies. The first examines how PE in Africa has performed relative to public markets. To do this, public market equivalent returns were calculated, which represent the return that an investor would have received if an equivalent investment had been made in the MSCI Emerging Market Index. The findings indicate that, on a gross of fees basis, a dollar invested in private equity in Africa has, on average (median), returned 78% (37%) more than a dollar invested in the MSCI Emerging Market Index over the period 1996 to 2019. Not only have top quartile funds outperformed the index, but so have the average, median, and bottom quartile funds - implying better relative performance than has previously been reported for PE in emerging markets. These results explain the recent increases in investor allocations to PE investments in Africa and imply that an allocation to PE may contribute positively to an allocator's overall portfolio return. The second study investigates whether the GP performance in Africa is persistent using the deal level approach introduced by Braun et al. (2017) that allows for a decomposition of the sources of persistence. The findings suggest that IRR performance is persistent across subsequent deals exited by the same GP and indicate that persistence is driven by the third and top quartiles. This implies conventional wisdom to back GPs that have previously achieved top quartile performance holds in Africa. In exploring the sources of persistence, this study finds that GPs differ systematically in their ability to achieve timeous and high value exits and that this factor has a substantial influence on persistence. Unlike the developed markets literature that documents the disappearance of persistence, the results indicate that the increasing capital flows to the PE industry on the continent have had a limited negative influence on persistence. This suggest that past PE performance in Africa is a good predictor of future returns. The third study investigates the factors that have an impact on PE investment holding periods in Africa. It focuses on the impact of deal characteristics and market conditions on holding periods and uses survival analysis to examine how these factors impact exit behavior. The results indicate that investment duration is persistent across subsequent deals exited by the same GP. This suggests that the ability to timeously realise value is attributable to skill and implies that investment duration may be an important dimension of GP selection. Furthermore, contrary to the increasing holding periods documented by studies focused on developed PE markets, the resultsindicate that the holding periods of PE dealsin Africa have declined over time in line with an improving exit environment as more capital is dedicated to the asset class on the continent. The results also indicate that holding periods are countercyclical and so are lower for investments held when the economy is performing, credit spreads are low, and aggregate industry commitments are increasing. This suggests that GPs on the continent time their exits to take advantage of favourable market conditions. The fourth study uses quantile regression to investigate the impact of macroeconomic conditions on PE returns and examines the combined impact of deal, GP, and macroeconomic factors on performance. The results indicate that GDP growth has a strong positive impact on deal level returns while credit spreads have a negative association with performance. The impact of GDP growth is larger on high performing investments than on low performers while the magnitude of the negative relationship between returns and credit spreads is larger for higher performing investments. Notably, the results indicate that capital flows have a significant positive impact on top quantile performers and a nonsignificant influence on low and median performers. Combined with the findings of the third study, this suggests that top performers take advantage of improving liquidity conditions by exiting timeously and therefore realise higher performance. Overall, the results suggest that an allocation to the asset class may contribute positively to an allocator's overall portfolio return. Notably, the presence of deal-by-deal performance persistence indicates that the conventional wisdom of selecting GPs that have previously achieved good performance may be applicable when selecting GPs on the African continent. Furthermore, the finding of holding period persistence demonstrates the importance of the ability to timeously realise exits as a dimension of GP selection. This implies that LPs should pay due consideration to whether the track records of GPs demonstrate persistent abilities in evaluating market conditions and making value enhancing decisions about the timing of exits
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    Open Access
    The impact of the COVID-19 pandemic on EMS practitioners in the Western Cape: strategies to enhance wellness
    (2025) Cermak, Radomir; Cunningham, Charmaine
    This research study aimed to explore the psycho-social impact of stress endured by frontline emergency medical services providers during COVID-19 pandemic and to develop a framework for enhancing their wellness during healthcare crises of the same or similar nature. Prior to the pandemic, emergency medical services providers faced high occupational stress within their work environment, which was characterised by exposure to traumatic scenes and high-stress conditions. The COVID-19 crisis added unique pressures, including increased mortality rates, higher exposure to the virus, and lack of resources emphasising the need for improved wellness strategies. Conducted as a qualitative design, using instrumental case study at the Western Cape Government Emergency Medical Services, Khayelitsha base, Cape Town, this research delved into the experiences of emergency medical care providers during the pandemic, the psycho-social effects the pandemic had on these providers, the coping strategies employed during the crisis and the wellness-enhancing aspects within the context of a health crisis, such as the COVID-19 pandemic. The study data was obtained using one-on-one interviews with a sample of thirty emergency medical care providers and focus group interviews with nine managers from the Western Cape Government Emergency Medical Services, Khayelitsha base, Cape Town, who were operational during the pandemic. The samples included both staff who became infected with COVID-19 but recovered and those that did not contract COVID-19. The qualitative data was analysed using thematic analysis to identify key themes and patterns in the participants' responses. The findings propose a structural framework for bolstering the wellness of emergency medical services providers, within four wellness contexts of spirituality, family, work, and community, with suggested interventions in each context The findings highlight the importance of recognising and addressing the mental and social toll that emergency medical care work during the COVID-19 pandemic had on providers, as well as the need for ongoing preparation, support and resilience building in high-stress situations, such as the COVID-19 pandemic. The proposed framework may provide basis for further implementation of specific psycho-social interventions within emergency medical services work environment and inform policy development in this regard.
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    Open Access
    Regulation of HPV infection and cervical cancer development following a helminth infection
    (2025) Butters, Claire; Horsnell, William; Schafer Georgia
    Soil-transmi,ed helminth (STH) infec7ons elicit systemic immune responses and have the ability to alter suscep7bility to other infec7ons in sites uncolonized by the STH. Recent work published by our group demonstrated that hookworm infec7on increased pathology in the female genital tract (FGT) following infec7on with the commonly sexually transmi,ed herpes simplex virus (HSV)-2. Although epidemiological studies have linked helminth infec7on with an increased prevalence of the most common sexually transmi,ed infec7on, human papillomavirus (HPV), studies in our lab have demonstrated that exposure to helminth products can decrease HPV pseudovirion uptake in vitro. Persistent infec7ons with high-risk types of HPV can result in cervical cancer, the leading cause of cancer related deaths in women in South Africa. Li,le is known about the associa7on between these two diseases. In this thesis, I inves7gated how HPV pseudovirion (PsV) infec7on can be altered by an STH infec7on both in vitro and in vivo. In vitro experiments demonstrated exposure to soma7c helminth an7gens from Nippostrongylus brasiliensis and Heligmosomoides polygyrus bakeri decreased HPV PsV infec7on in two cervical cancer cell lines and one primary kera7nocyte cell line (the target cell of HPV). Similarly, exposure to the excretory-secretory (ES) an7gens from H. polygyrus decreased HPV PsV infec7on in two cell lines, and increased HPV PsV infec7on in the other cervical cancer cell line. When the soma7c an7gens were heat inac7vated, the protec7on against HPV PsV infec7on was abrogated, sugges7ng the molecule involved in this protec7on is a heat unstable protein. In contrast, when H. polygyrus ES an7gen was heat inac7vated, the previously observed increase in infec7on was reversed and instead decreased HPV PsV infec7on. Addi7onally, western blot analysis revealed that exposure to N. brasiliensis soma7c an7gen resulted in increased expression of vimen7n, a molecule known to inhibit HPV infec7on. These results were then validated in vivo, through the development of a physiological murine model for HPV infec7on, u7lising a luminescent HPV PsV and in vivo imaging system (IVIS). Following op7misa7on, I found that HPV PsV infec7on was significantly reduced following intravaginal exposure to N. brasiliensis L3 an7gen and at day 9 post-infec7on with N. brasiliensis. This was associated with a significant increase in eosinophil accumula7on in the female genital tract (FGT) and iliac lymph node (iLN), the draining lymph node of the FGT. Coinfected mice demonstrated a popula7on of eosinophils expressing lower levels of Ly6C and higher levels of CD11b, a recruitment marker. When eosinophil recruitment was blocked, the helminth-dependent reduc7on in HPV infec7on is lost, sugges7ng these immune cells may contribute to this observed protec7on. Addi7onally, western blot analysis revealed that N. brasiliensis infec7on increased the expression of an HPV receptor, glypican. These data suggest that coinfec7on with N. brasiliensis has a protec7ve effect against the ini7al infec7on of HPV. Finally, to inves7gate how STH infec7on may influence the development and growth of HPVrelated cervical cancer, I developed a cervical cancer xenograY model using nude mice. Here, my data suggest that engraYed nude mice infected with N. brasiliensis displayed reduced growth of cervical cancer tumours compared to naïve mice, with no change to tumour immune cell infiltrates but rather an increase in tumour cell p53 expression and altered epithelial to mesenchymal transi7on (EMT) marker expression. Together, these findings show that helminth infec7on can protect against distal viral infec7on and suppress the growth and cancer cell behaviour of HPV associated cervical cancer.
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    Open Access
    Evaluating the impact of ultraviolet light on chemical and mechanical properties of human scalp hair through controlled and natural experiments
    (2025) Buthelezi, Ntandoyenkosi; Ngoepe, Malebogo; Khumalo Nonhlanhla
    Introduction: Human hair fibres have been studied in a variety of fields for different applications. Examples include the use of hair as a medical testing substrate for diagnosis of pathologies, as a tool for forensic investigations, a substrate for cosmetic product development and as a precursor material for construction engineering and agriculture. The changes that affect the character and behaviour of hair fibres, arising from exposure to environmental factors such as UV radiation, have been the focus of some studies. Even though there are a range of environmental variables that could be worthy of consideration, understanding the impact of UV radiation is increasingly important given the inevitability of exposure and changes in climatic conditions. Chemical and mechanical experiments have demonstrated that the proteins and pigments of human hair are most heavily affected during exposure to UV radiation, resulting in unhealthy fibres, suppressed growth and permanent hair loss. Problem: Photodamage and photoprotective potential of human hair fibres have been identified, however many studies have been conducted on ‘Caucasian' hair samples and the findings have been assumed to hold for other population groups. The use of race-based classification systems has further confounded findings, as the groupings are not able to account for intra-population and intra-individual variation objectively. This study is the first evaluation aimed at comparing the effect of UV radiation on hair of varying curl, using a combination of chemical and mechanical tools alongside advanced statistical techniques on the same samples. Furthermore, the study makes use of both controlled UV-exposed fibres and dreadlocks exposed to natural sunlight. Therefore, this study aims to compare the effects of UV irradiation and hair curl on the chemical and mechanical characteristics on human hair fibres, for controlled UV-exposed fibres and natural sun-bleached dreadlocks. Method: To analyse the influence of the radiation interaction with human hair, natural untreated, and UVA and UVB radiated black hair samples of low to high curl were compared. This study utilized thermogravimetric analysis and derivative thermogravimetry (TGA/DTG), Fourier-transform infrared spectrometry (FTIR- ATR) coupled with multivariate analysis, scanning electron microscopy (SEM) and mechanical tensile testing (MTT) techniques to obtain information on the chemical, and mechanical properties of the human hair. Results: UVB radiation resulted in more significant changes than UVA across all curl types, as demonstrated by all measurement techniques. After 7 days of UVB exposure, FTIR revealed changes on the absorbance of the amide and lipid bands. Major changes were observed associated with degradation of proteins at characteristic peaks; amide A (3300 and 3070 cm-1 ), amide I (1650 cm-1 ), and amide II (1550 cm-1 ). UVB 7-days exposure also produced the highest amount of the cystine oxidation products (at 1022-1077 cm-1 region) and had the lowest absorption for the disulphide bonds. The TGA/DTG showed that the onset degradation temperature (ODT) of UVB-treated fibres was significantly reduced compared to both the control group and UVA exposed group. The MTT results showed increased yield stress and yield strain for UVB exposed fibres. Interestingly, a threshold effect in damage was observed in low curl fibres as opposed to high curl fibres. Extending UV exposure time beyond 7-days in low curl hair fibres did not result in increased damage, however, this phenomenon was not observed for the high curl fibres. For the natural dreadlock experiment, the distal hair fibres showed reduced thermal stability and changes in the chemical properties observed on the FTIR. There were no significant changes on the mechanical properties of proximal compared to distal hair fibres. However, a SEM investigation revealed more structural damage in the distal fibres which might contribute to differences observed in the TGA and FTIR. This study provides novel insight into a critical point at which damage becomes pronounced and highlights how hair fibres of varying curl respond to UV-induced stress. This knowledge will not only aid hair scientists in navigating population specific hair analysis, but also provides valuable insights and paves a way for informed strategies for hair care development industry and related disciplines. The results obtained in this study could be beneficial for the hair care industry by informing the formulation of targeted products that account for different hair types and their specific vulnerabilities to UV damage. For instance, cosmetic companies could develop specialized UV protection shampoos and conditioners designed to address the specific needs to different hair types.
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    Open Access
    Degradation behaviour of the mechanical properties of bovine cortical bone
    (2025) Daras, Nicholas; Cloete, Trevor; Nurick, Gerald
    Cortical bone, is subject to extensive mechanical characterization, yet the literature reveals notable discrepancies in reported mechanical properties, in particular concerning the elastic modulus. This variability is attributed to the intricate nature of bone and the diverse experimental factors influencing its performance, notably specimen preparation, including machining techniques and storage protocols. Additionally, the manner in which machine compliance is accounted for is not always reported, particularly concerning the quasi-brittle nature of cortical bone. Even when compliance is accounted for, the methods are not elaborated on in great detail. A further critical observation is the absence of an intermediary step in bone testing simulations, bridging the gap between specimen-scale material characterization and full bone testing. An intermediate stage would provide validation data for a nuanced understanding of material behaviour while mitigating computational expense associated with full bone simulations. To address these gaps, this thesis develops solutions that enhance the accuracy and reliability of the mechanical testing of bone. A custom subpress has been designed and commissioned to minimize machine compliance during quasi-static compression tests on small cortical bone specimens. By quantifying machine compliance through novel methodologies, this research has unveiled its significant impact on mechanical property measurements. Furthermore, this investigation delves into the effects of long-term storage, particularly frozen storage, on bovine cortical bone properties. Three distinct storage protocols were evaluated over a one-year period, revealing significant degradation of fresh bone samples beyond six months irrespective of storage method. This study sheds light on the practical implications of specimen storage protocols in preserving bone integrity. In parallel, the efficacy of cross-section bone specimen tests as an intermediary validation step for simulations is presented. Dynamic strain rate tests using a three-point bending split Hopkinson bar yield rich datasets, indicating clear trends applicable for numerical validation. Simulations utilizing dynamic compression and cross-section data exhibit encouraging correlations with experimental observations. A comparison between the material model for cortical bone in the commonly used ‘Total Human Model for Safety' (THUMS) and a strain-rate dependent plasticity material model highlights the advantages of the latter, emphasizing the potential for enhanced simulation accuracy.