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Hydraulic and Anatomical Trait Plasticity in Fynbos Growth Forms Across a Climatic Gradient in the Cape Floristic Region
(2026) Arens, Matthew; West, Adam; Skelton, Robert
The Cape Floristic Region (CFR) is projected to experience increased frequency and intensity of drought events. Comprehensive understanding of drought tolerance and response across the fynbos vegetation remains limited. This dissertation contributes to addressing these gaps by, first, testing and refining the pneumatic method for constructing xylem vulnerability to embolism curves across three major fynbos growth forms, and second, examining variation of functional traits related to plant hydraulics and xylem anatomy, within and between species along a regional climatic gradient. The pneumatic method was implemented for Protea repens (Proteaceae), Erica monsoniana (Ericaceae) and Cannomois congesta (Restionaceae). A methodological refinement was applied that paired repeat relative water content measurements on pneumatron samples with individual water potential and relative water content relationships to improve water potential estimates. Vulnerability curves generated using the pneumatic method produced coherent metrics, especially at 50% embolised. Additionally, comparisons with published optical and centrifuge datasets showed general agreement. Protea repens and Erica monsoniana were further sampled across three sites spanning a regional climatic gradient to explore for hydraulic and anatomical trait plasticity. Within species, embolism thresholds, sapwood-specific conductivity and vessel diameters were conserved across the gradient. By contrast, osmotic and turgor traits varied among sites. Species differences were consistent, E. monsoniana exhibited more negative vulnerability thresholds and wider hydraulic safety margins than P. repens, aligning with previous understanding of these species' differences in hydraulic strategies. At regional, intraspecific scales, relationships between climate, xylem structure and embolism resistance appear marginal, implying that climatic response of functional traits at this scale primarily manifest at the leaf-level water relations.
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Open Access
Modelling Preferences for Non-Conventional Water Sources for Toilet Flushing: A Discrete Choice Approach
(2026) Andrews, Cameron; Mofokeng, Teboho
Urban water systems in arid and semi-arid regions are increasingly stressed by climate change and rising demand, highlighting a need for decentralised and alternative supplies. While the technical feasibility of options such as desalinated seawater and recycled water is well established, household acceptance remains a key constraint, particularly for its household applications. This study investigated household preferences and underlying decision-making rules for using non-conventional water sources to flush toilets in the coastal, water-stressed context of Hout Bay, Cape Town. A labelled discrete choice experiment (DCE) was developed to compare partially treated seawater, recycled water, and drinking water as flushing sources, with attributes reflecting water aesthetics (stain, colour and odour), cost implications, and disposal practices. The experimental design presented six choice tasks to each respondent and was administered via intercept surveys, following piloting and refinement. A latent class (LC) model revealed two behavioural classes, namely an environmentally conscious group, insensitive to cost and aesthetics, and a cost-conscious group whose acceptance was strongly shaped by cost changes and the colour of the water, alongside support for improved disposal practices. Overall, the results indicate that toilet flushing is a viable entry point for household acceptance of non-conventional water sources, with partially treated seawater emerging as a particularly promising option in a coastal community. Implementation strategies should therefore be framed in relation to affordability for cost-sensitive households and environmental benefits for environmentally oriented households.
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Open Access
The aerobic, water-assisted photo-catalytic oxidation of CH4 over platinum-based catalysts in batch vs. continuous reactors -a new route to methanol?
(2026) Amonye, Chiamaka; Van Steen, Eric
The direct conversion of methane to value-added products such as methanol is often referred to as the ‘holy grail' reaction in catalysis, due to its potential to bypass the energy-intensive syngas route [1], [2]. Several technologies have been investigated for this direct conversion in recent years such as conventional catalytic processes, plasma technologies, membranes technologies, photocatalysis, etc. Yet these processes have not seen commercial implementation due to the thermodynamics of breaking the strong C-H bond (435 kJ/mol) and the tendency of partially oxidised intermediates to undergo further oxidation to COx species [1], [2]. Recent studies have shown that direct methane conversion is feasible over platinumbased catalysts under relatively mild conditions in a trickle bed reactor operating at 220 ⁰C and 30 bar in the presence of liquid water (0 – 0.3 ml/min), with methanol and methoxy methanol at a selectivity of ca. 10% at a methane conversion of 0.6% (and other C1 oxygenated products) [3]. This work highlighted that the direct conversion at relatively low temperatures is possible via weakly adsorbed oxygen species over transition metal surfaces and the site blocking action of water [3][4]. In this study, the direct photocatalytic and thermo-catalytic oxidation of methane was investigated over two platinum-based catalysts (0.5 wt% Pt/TiO2(rutile) and 0.5wt% Pt/WO3) in both batch and continuously operating slurry reactors. It is hypothesized that continuously operating slurry reactors result in higher apparent methanol/C1 oxygenate selectivity in the photocatalytic conversion of methane when compared to the same reaction in batch slurry reactors. Baseline photocatalytic experiments were conducted in a slurry batch reactor operating at 50 ⁰C, 1 atm with UV/visible light. Thereafter, a continuously operating photocatalytic slurry reactor (PSR) was then designed, constructed and commissioned. Experiments spanning 1.5 – 2 days were then conducted on the platinum-based catalysts at 22 bar and varying temperatures (25 – 180 ⁰C). The partial pressures of methane and oxygen were fixed at 0.74 bar and 1.07 bar respectively and UVA (405 nm), blue light (475 nm) and green light (575 nm) were employed as irradiation sources. In the batch reactor, negligible conversion was observed during the dark phase, while irradiation achieved methane consumption rates of 1.89 and 0.95 μmol.gcat-1.min-1 for 0.5 wt% Pt/TiO2(rutile) and 0.5wt% Pt/WO3, respectively. With respect to productivity, deep oxidation products (CO and CO2) dominated over both catalysts, particularly at early reaction times, and product accumulation within the closed reactor generally favoured overoxidation toward thermodynamically stable COx species. Organic products were formed only in minor quantities, with apparent quantum yields for methanol formation remaining low for both catalysts (10-7 – 10-8 %). Although irradiation with UVA and visible light yielded some photocatalytic activity, photon utilisation remained inefficient (~0.011% for Pt/TiO2 and ~0.004% for Pt/WO3), indicating significant underutilization of incident photons due to light attenuation, gas-liquid mass transfer, intrinsic kinetics in the oxidation and reduction reactions and charge carrier recombination [5], [6]. In contrast, the PSR demonstrated steady-state operation across all investigated operating windows but exhibited a fundamentally different limitation regime. Methane conversion remained essentially constant (~0.20-0.23%) across 100 – 180 ⁰C temperature range in the dark and the introduction of UVA, blue and green light irradiation at 180 ⁰C did not enhance conversion of methane consumption rates over either catalyst, despite the sufficient photon supply. The weak temperature dependence and insensitivity to irradiation indicated that under the investigated conditions, the PSR's behaviour was dominated by thermo-catalytic behaviour, rather than photo-catalytic enhancement. It also alludes to system-level constraints, where gas-liquid mass transfer, slurry hydrodynamics, and light attenuation may be governing performance, yielding the observed thermo-catalytic behaviour. This conclusion was further supported by catalyst loading experiments using 0.5 wt% Pt/TiO2(rutile), where an increase in the catalyst loading from 1 g/L to 10 g/L did not result in an increase in conversion, but a reduction in the specific methane consumption rate, this behaviour is consistent with transport and light screening limitations rather than intrinsic kinetic control [5]. Overall, while photocatalytic methane oxidation was demonstrated in both reactor configurations, the performance in the PSR was constrained by transport phenomena rather than photon availability or intrinsic catalyst activity. Future work should focus on reactor-level modifications in the PSR to address the transport limitations identified in this study. Operating within a narrower low-temperature window (<100 ⁰C) under controlled irradiation may provide a clearer separation of thermal and photocatalytic contributions and help identify true optimum operating conditions. In addition, systematic variation of space velocity is required to distinguish intrinsic surface kinetics from mass-transport limitations and assess the influence of time on stream on conversion. Furthermore, alternative photocatalyst supports with stronger visible-light absorption characteristics and reduced electron-hole recombination tendencies could also be beneficial to the improvement of photocatalytic performance under milder operating conditions. iv
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Open Access
2,4-Diaminopyrimidines active against Plasmodium falciparum via the inhibition of haemozoin formation: In-silico discovery and SAR Investigation
(2026) Amod, Leah; Wicht, Kathryn; Veale, Clinton
Efforts towards the eradication of malaria have been countered by the frequent emergence of Plasmodium resistance to clinical drugs, necessitating the tactical development of next-generation antimalarials. Haemozoin formation, the mechanism by which Plasmodium detoxifies haem during its asexual blood stage, is an attractive target owing to its non-genomic, and therefore non-mutable nature. Furthermore, the therapeutic potential of this pathway has been extensively validated via antimalarial drugs such as chloroquine, making it suitable for target-based drug discovery. Contemporary drug discovery has become increasingly reliant on in-silico tools to accelerate the identification and development of new candidates by vastly expanding the chemical space that can be accessed while heavily reducing time, labour, and material costs. In this work, a virtual screening workflow combining structure-based and ligand-based methods was developed to screen a commercial library of 300K compounds for potential inhibitors of βhaematin (synthetic haemozoin) formation that retain in-vitro activity against Plasmodium falciparum. After applying physiochemical and structural-similarity filters, the resultant diverse, “druglike” set of 25 000 compounds was first virtually screened via molecular docking against a model of the β-haematin crystal. Next, two classification models were trained to predict whether an inhibitor of β-haematin formation would display whole-cell activity against P. falciparum. The optimised models were used to screen the docking hits, resulting in a combined total of 404 compounds with predicted antiplasmodial activity. Selection criteria were then applied to prioritise 32 compounds for experimental testing, the results of which showed the in-silico workflow to be highly effective in enriching hit rates for β-haematin inhibition (43%) and whole-cell activity (30%). Notably, the coumarin-containing compound O3 was found to be a potent inhibitor of β-haematin formation inhibition (IC50 = 8 μM vs chloroquine IC50 = 25 μM) and displayed submicromolar activity against chloroquine-sensitive P. falciparum (IC50 = 0.154 μM). Though commercially available, the synthesis of O3 had not been reported in the literature, nor had the therapeutic potential for this chemotype been investigated. As such, an investigation into the structure-activity relationships of O3 was conducted, beginning with the development of a synthetic route for accessing the parent molecule and several rationally designed analogues. Accessing the desired analogues required substantial synthetic optimisation to overcome the impact of deactivated synthons. This was particularly stark during the construction of the core 2,4-diaminopyrimidine region. An in-depth biological assessment confirmed that several members of this small cohort retained promising inhibitory activity against whole-cell P. falciparum with selectivity over human HepG2 cells and validated that β-haematin formation inhibition translated into intracellular inhibition of haemozoin formation. These data further showed that while the coumarin moiety, central phenyl ring or pyrimidine methyl were not required for biological activity, alteration of the 2,4diaminopyrimdine pharmacophore was detrimental to biological activity. In summary, the in-silico workflow can identify promising scaffolds for antiplasmodial drug discovery. The compounds developed in this PhD represent an important new class of compounds which show promise for further optimisation, including additional SAR insight, increased biological activity, and improved physicochemical properties.
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Open Access
'The Sweetness of Belonging': Mobility and South African Indian Identity
(2026) Abrahams, Chenayde; Daya, Shari
This thesis explores the dynamic interplay between mobility – both forced and voluntary – and South African Indian identity in Johannesburg, focusing on the establishment of Lenasia under Apartheid, and contemporary Indian migrations to formerly White suburbs such as Glenvista and Glenanda. Drawing on oral histories from twelve participants who experienced forced removals and/or recent relocations, this thesis examines how race, place, memory, and belonging are negotiated across generations and locations. Through reflexive thematic analysis of semi-structured interviews, the research reveals ambivalent recollections of Apartheid-era displacements, impacted by forgetfulness around trauma, an unjust Apartheid construction of force, and race/class realities that allow for ‘softer' recollections (Anderson & Daya 2022). The interrogation of Lenasia as an Apartheid-crafted township exposes it as a contradictory space: a site of enforced violent segregation that also fostered intimate community bonds through shared practices like food-exchange and sport, embodying a 'kasi way-of-being' rooted in collectivism. However, participants' recent movement into previously White-only suburbs is often framed as escapes from perceived decay linked to informal settlements – exposing internalized anti-Blackness and subconscious desires for proximity to Whiteness. In these new spaces, disbelonging persists through anonymity, racial misrecognition (Hansen 2012), and the loss of communal safety, even as participants transplant Lenasian practices as subtle resistance. Theoretically grounded in concepts of place-identities (Relph 1976), racial epidermalization (Fanon 1952), the politics of memory and forgetting (Anderson & Daya 2022), and anti-Blackness (Sharpe, 2016), the findings underscore Apartheid's enduring legacies: racial hierarchies both reconfigured and disrupted through mobility, memory, and everyday acts. Ultimately, the thesis argues that belonging is not fixed but actively remade, offering insights into ‘post-Apartheid' urban inequalities and the need for more inclusive spatial justice in Johannesburg.