https://ir.unisa.ac.za/handle/10500/2910 Mon, 11 May 2026 17:18:02 GMT 2026-05-11T17:18:02Z https://ir.unisa.ac.za/handle/10500/32428 Deep learning for spatial multi-omics: predicting cardiomyocyte differentiation efficiency at single-cell resolution Kgabeng, Tumo Cardiovascular diseases remain the leading cause of global mortality, with limited regenerative capacity of adult cardiac tissue presenting significant therapeutic challenges. The primary cause of death worldwide is still cardiovascular diseases, and treating these conditions is extremely difficult due to the adult heart tissue's limited capacity for regeneration. Cardiomyocytes derived from human induced pluripotent stem cells (hiPSC CMs) present promising potential for cardiac regenerative medicine; however, existing differentiation protocols are highly inconsistent and do not have accurate predictive evaluation techniques. By integrating the analysis of temporal gene expression data and spatial transcriptomics, this study developed a novel hybrid deep learning architecture that combines Graph Neural Networks (GNNs) and Recurrent Neural Networks (RNNs) to predict the outcomes of cardiomyocyte differentiation. RNN components analysed temporal gene expression trajectories across 800 samples and 10 time points, while GNN components processed spatial transcriptomics data from 752 tissue spots to capture spatial relationships. Three fusion strategies - concatenation, attention-based, and ensemble approaches - were meticulously evaluated. With an accuracy of 96.67%, the ensemble fusion approach outperformed the state-of-the-art computational approaches by a significant margin (+13.47% compared to the top GNN approaches and +6.97% compared to specialised biological models). Keywords: Cardiomyocyte differentiation; Spatial transcriptomics, Spatial multi-omics; Single-cell biology; Deep learning; Graph Neural Networks; Recurrent Neural Networks; Stem cells; Artificial Intelligence; Cardiac biology Fri, 06 Mar 2026 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/32428 2026-03-06T00:00:00Z https://ir.unisa.ac.za/handle/10500/32332 Estimating brittleness indexes from mechanical and petrographic characteristics of Norite Molomo, Selaki Grace Norite is a coarse-grained plutonic rock that has been relatively understudied in terms of its mechanical and petrographic properties. This study investigates the brittleness of norite within the Eastern Limb of the Bushveld Igneous Complex (BIC), South Africa. However, there is a scarcity of studies that quantitatively link its petrographic characteristics to establish brittleness indices. The primary aim was to estimate brittleness indexes based on both mechanical and petrographic properties of norite, which is a significant rock type commonly found in the hanging walls of platinum mines. Given the recurring safety incidents, especially falls of ground and rock bursts in underground mining, understanding the brittleness of norite is essential for enhancing geotechnical designs and safety measures. Samples were collected from a 10-meter exposure along Mototolo Road in the Critical Zone of the Eastern Bushveld Complex, near the Anglo-American Platinum Mototolo Mine. Mechanical analysis involved laboratory testing, which includes uniaxial compressive strength (UCS), tensile strength, Young's modulus, and Poisson’s ratio, supported by numerical simulations and multivariate regression models. The results indicate that norite exhibits high compressive strength and low ductility, with brittleness indexes effectively predicted using combinations of strength parameters. Mineralogical investigations were done using thin-section petrography to evaluate grain texture, contact nature, and mineral composition. It was observed that coarse and medium grain textures significantly influence brittleness, whereas grain contact type alone lacks predictive power. The main contribution of this work is the development of integrated predictive models that use both mechanical and mineralogical data. While the use of surface samples presents a limitation, their geological equivalence to underground norite supports the relevance of the findings for subsurface application. The findings enhance the understanding of the structural performance of norite and suggest practical recommendations for underground mine design. This research further contributes to improved and safer mining operations. Fri, 13 Feb 2026 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/32332 2026-02-13T00:00:00Z https://ir.unisa.ac.za/handle/10500/32261 Reliability analysis of studded shear connectors in composite slabs subjected to shear loading Morudu, Kagiso Ntate This study investigated the reliability of stud connectors in composite slabs subjected to shear loading, focusing on the adequacy and efficiency of design provisions outlined in four major international codes: SANS 10162-4, EN 1994, AISC 360, and AS/NZS 2327:2017. The analysis evaluated the safety margins and conservatism inherent in these codes, using both the First Order Reliability Method (FORM) and Monte Carlo Simulation (MCS) to assess the probability of failure of stud connectors under various loading and material conditions. The study began by analysing model uncertainty, revealing significant differences in bias and variability among the design codes. The SANS 10162-4 model showed no bias and minimal variability, while AISC 360 demonstrated the largest bias and variability. EN 1994 and AS/NZS 2327:2017 displayed moderate levels of conservatism. Reliability indices were computed for each design code, with results indicating that all models provided sufficient safety margins, though EN 1994 and AISC 360 exhibited excessive conservatism that may lead to overdesign. A sensitivity analysis based on FORM identified variable actions as the most critical factor affecting reliability, followed by stud diameter. The implications of these findings were used to propose adjustments to partial safety and reduction factors to optimize design efficiency without compromising safety. For instance, a reduction in the partial safety factor from 1.25 to 1.1 for EN 1994:2005, and an increase in the partial reduction factor for AISC 360 from 0.65 to 0.80, were recommended. The study concludes that while the current design standards provide adequate safety, there is significant potential for optimization, particularly in reducing conservatism in certain models. Future research is recommended to refine design models, account for more complex loading conditions, and explore probabilistic methods to further enhance the reliability and efficiency of stud connector designs. Limitations of the study include the use of simplified load conditions and assumptions about material properties, as well as the exclusion of long-term effects such as creep and shrinkage. In summary, this study evaluates the reliability performance of existing stud-connector design models and develops calibrated resistance factors that enhance their consistency with target reliability levels, providing evidence that can inform future improvements to design provisions while maintaining adequate safety margins. Mon, 01 Sep 2025 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/32261 2025-09-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/32122 Biodegradation of environmental significant inorganics using aerobic bacteria found in Blesbokspruit Wetland, South Africa Kgabile, Mpho Gift The Blesbokspruit wetland is known to be one of the imperative wetlands in Republic of South Africa (RSA), located in region of Ekurhuleni, Gauteng Province. A continuous discharge towards the Blesbokspruit wetland from effluents coming from the nearby Grootvlei mine, paper production company (South African Pulp and Paper Industries) and other anthropogenic activities accompanied with environmental impurities which include cyanide-residues has been witnessed within the wetland. Cyanide compounds depict distinct characteristics depending on chemical bindings with other elements which determines their severity and stability of the compound. Cyanides are either classified as either organic or inorganic cyanides and they are regarded as environmental significant contaminants. Biodegradation processes have proved to be an ideal tool to degrade environmental significant contaminants due to its cost effectiveness, eco-friendly and durability. The environmental significant inorganic placed under study is thiocyanate and its biodegradability using microorganisms isolated from soil, water and sludge within Blesbokspruit wetland. Among the most problematic inorganics found in wetlands are cyanides, particularly thiocyanate, which are toxicophores due to their cyanide content. Studies have shown that cyanides are present in effluents channelled by mining industries, which results in the deterioration of the Blesbokspruit wetland. Microorganisms were isolated and identified using universal primers 16S-27F and 16S-1492R, targeting 16S rDNA sequence. Indicator plate technique was applied in order to detect microorganisms with thiocyanate biodegradation capabilities, where phenol red aided as an indicator to distinguish microorganisms that can degrade thiocyanate by observing a colour change from red to pink. Later, thiocyanate degrading isolates and mixed culture were inoculated in minimal media without addition of a carbon or nitrogen source and 1/10th minimal medium containing a 24-hour starved culture was further inoculated in batch conical flasks containing minimal media with thiocyanate (SCN) either 150 mg SCN-/L or 250 mg SCN-/L. The sampling intervals were done every 24 hour-interval for a duration of 5 days, whereby the absorbance of microbial growth was measured at 600 nm and ammonium-nitrogen was measured with use of Merck Spectroquant Pharo 300. The results have shown that only few bacterial isolates were more effective compared to the bacterial consortium with regards to biodegrading thiocyanate, whereas the highest biological thiocyanate removal efficiency achieved in this study was 97.44 % and 95.71 % under 150 mg SCN-/L and 250 mg SCN-/L by Exiguobacterium sp., respectively. Most of bacterial isolates gave less biological thiocyanate removal efficiency as compared to bacterial consortium which was dominantly comprised by Pseudomonas sp. It was concluded that aerobic bacteria obtained at the Blesbokspruit wetland were capable of biodegrading thiocyanate which is deemed as an environmental significant inorganic. The greater concentration amounts of thiocyanate, most bacteria seemed to be susceptible to exposure, although few bacteria exhibited some form of resistance to some extent. Most of these bacteria were able nitrify the available ammonium-nitrogen. Wed, 21 Dec 2022 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/32122 2022-12-21T00:00:00Z