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Now showing 1 - 5 of 19

Recent Submissions

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    Connected domination number, average distance and their application in drug design
    (University of the Witwatersrand, Johannesburg, 2025) Flowers, James David John; Jonck, Elizabeth; Maartens, Ronald John; Mukwembi, Simon
    Let a graph with n vertices be G. A leaf of G is a vertex of degree 1 in G. The leaf number of G, denoted L(G), is the number of leaves in a spanning tree of G that contains the maximum number of leaves possible. The Wiener index of G, denoted W(G), is defined to be the sum of the distances between all unordered pairs of vertices in G. When the Wiener index of G, of order n, is divided by n2 , the average distance, denoted µ(G), is obtained. We are concerned with bounds on W(G) and L(G). Also, we attempt to model the biological activity of some compounds using these two Graph Theory concepts. The output of the model is analysed using statistical methods and the suitability of the parameters is determined.
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    Geophysical insights into the southern Lebombo volcanic sequences and its influence on the formation of the Zululand Basin
    (University of the Witwatersrand, Johannesburg, 2025) Makhateng, Pontsho Tamara
    The Lebombo sequence provides a glimpse into the past by studying its formation and the sequence of tectonic events that caused the mountainous monocline we see today. The Lebombo sequence is part of the failed triple junction, which had two arms that were sequences of the volcanic basalts and rhyolites and a third arm that was a dyke swarm. The cause of these structures was assumed to be due to a plume and/or lithospheric stretching. Each of these theories can be placed into the context of the Gondwana break-up. Once faulting and rifting of Gondwana began, the study area was also affected by additional crustal thinning and stretching, which led to the intrusions of the Lebombo sequence. As rifting then became drifting, the formation of the Zululand Basin occurred. The Zululand Basin formation is strongly tied to the Lebombo basement. The purpose of this study is to understand the subsurface structure and formation of the Lebombo sequence and the Zululand Basin using geophysical data. The geology of the region consists of the Lebombo sequence outcropping to the west of the Zululand Basin and dipping eastwards to form the basement of the Zululand Basin. The Lebombo is made up of the Jozini Rhyolites and the Sabie River Basalts. The sequences are overlain by the siltstones, sandstones, and reworked volcanics of the Zululand Basin. There are extensive intrusions in the Lebombo of dykes and the Bumbeni Complex. The Bumbeni Complex forms a ridge that divides the basin into two sub-basins. Most geological maps indicate the Bumbeni Complex as a single intrusion. In this study, the regional tectonics were interpreted from the Total Magnetic Intensity map. The regional interpretation of the area showed that the lineaments in the area do not have the same strike. The strike varies from NNE-SSW for the Jozini Formation to NW-SW for the Sabie River Basalt Formation. This change in strike could represent changes in the edge of the Kaapvaal Craton. Two 2D magnetic profiles were modelled using the open-source PyGMI software. One profile was in the northern section of the study area, where two seismic lines were used to constrain the model by determining the approximate depth of the Lebombo volcanic sequence. The observed data on iii profile 2 was not fitted well due to the resolution of the modelled area in PyGMI. The second 2D magnetic profile was in the area where the Bumbeni Complex intruded to see how it would affect the lithologies around. The results showed that the Bumbeni Complex was intruded after the volcanic sequences had dipped eastwards. The aim of these profiles was to assist in understanding the transition from the outcropping Lebombo volcanic sequences to the basin fill and to investigate the formation of the Bumbeni Complex. The profile models were not as successful as expected because fitting the data was difficult due to the presence of remanence and not enough physical property measurements to constrain the models. This made it difficult to determine the orientation and thickness of the intrusive dykes in the Lebombo sequence. A 3D inversion of the magnetic data was run, using ModelVision and UBC GIF-Tools, to determine whether the Bumbeni Ridge was a single intrusion or multiple intrusions across the basin. The results showed that the Lebombo sequence was intruded in three different places by the Bumbeni Complex to form the Bumbeni Ridge. Future work would include paleomagnetic studies and measurements of physical properties to assist with the modelling process.
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    Dietary L-glutamine affects eggshell quality in the post-peak laying period*
    (2022) Muszyński, Siemowit; Tomaszewska, Ewa; Arczewska-Włosek, Anna; Kasperek, Kornel; Batkowska, Justyna; Lamorski, Krzysztof; Wiącek, Dariusz; Janine Donaldson, Janine Donaldson
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    Trade with the West. Glass bowls of Eastern Mediterranean origin found in the courtyard of the Casas del Turuñuelo site (Guareña, Badajoz, Spain): archaeological context, analysis and conservation
    (Elsevier, 2023-06) González, Esther Rodríguez; Pérez, Sebastián Celestino; Medina Sánchez, María Cruz; Zucchiatti, Alessandro; Martín, Joaquín Barrio
    The aim of this work is presenting a group of glasses excavated from the archaeological site Casas del Turuñuelo (Guareña, Badajoz, Spain), whose destruction dates back to the 5th Century BCE. Different types of glasses were found, among them two thick-walled translucent bowls and a very fine blue-coloured bowl. The study and conservation of these pieces has made it possible to characterize the composition of the different types of glass and their specific degradation, and to identify the possible origin where they were manufactured, in the Eastern Mediterranean. In addition, it has managed to recover the original surface and shape of these pieces and has given them the necessary consistency to be well preserved and studied.
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    Optimising curriculum design using Bayesian structure learning
    (University of the Witwatersrand, Johannesburg, 2025) Mandlazi, Thabo; Ajoodha, Ritesh; Jadhav, Ashwini
    Mathematics education is vital in developing students’ analytical and problem-solving skills. However, in South African schools, many students opt for Mathematical Literacy over Pure Mathematics, often due to the latter being perceived as overly abstract and challenging. This study investigates the poten- tial of Bayesian Networks and score-based structure learning algorithms to optimise curriculum design, making Pure Mathematics more accessible, structured, and student-centered. Mathematical concepts were modelled as a Bayesian Network, enabling the extraction of prerequisite relationships using probabilistic graphical models. The study evaluated the performance of several struc- ture learning algorithms, including the Chow-Liu algorithm, the Tabu Search algorithm, the Simulated Annealing algorithm, and the Hill Climbing algorithm. The accuracy of the learned structures was as- sessed against a known ground truth using Structural Hamming Distance (SHD) and Kullback–Leibler (KL) Divergence. Results show that learned structures consistently recover the main prerequisite structures, with SHD and KL Divergence improving as sample size increases. Sparse learners (Hill Climbing, Chow–Liu) yield interpretable backbones that align well with expert expectations and are effective for auditing scope and sequence. Denser searches (Tabu, Simulated Annealing) surface additional cross-topic dependencies that highlight remedial and enrichment routes, although they’re less simple. Applied to ASSISTments data, the pipeline confirms meaningful prerequisite relations. It repeatedly elevates “connector” concepts (e.g., factorisation skills, numerical representation, symmetry) as influential bridges whose targeted re- inforcement can lower downstream difficulty. This research provides a foundation for data-driven curriculum modelling that ensures students mas- ter foundational topics before progressing to more advanced content. By leveraging adaptive learning frameworks informed by structural learning, educators can personalise instruction based on learners’ knowledge gaps, reduce cognitive overload, and enhance engagement. This approach holds particular promise in South Africa, where it can support efforts to shift perceptions of Pure Mathematics from abstract and intimidating to relevant and achievable. Limitations include sensitivity to skill tagging, priors, and static modelling of time. Overall, BN struc- ture learning emerges as a viable instrument for evidence-aligned curriculum design, supporting iterative “learn–validate–refine” improvement cycles in mathematics education.