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The relationship between the Zener-Hollomon parameter and transfer strip Creep in hot rolled AA3104
(2025) Borrageiro, Roberto; Goerge, Sarah
Excessive sagging has been experienced in AA3104 transfer bar after hot rough rolling, during transport between the hot roughing and finishing mills. This sagging has resulted in bottom scuffing and surface defects as a result of localised contact between the slab and the roller table. This creep of the material is caused by excessive recrystallisation in the microstructure of the material, as a result of the deformation parameters used during hot rough rolling. The presented research aims to assess the mechanical response of the material at varying deformation parameters and to verify their link to the resulting creep experienced by the material. The effects of hot rough rolling and in-situ creep will be simulated with plane strain compression tests performed on a Gleeble 3800 and the resulting test data will be linked with the deformation parameters through the use of the Zener-Hollomon Equation. The level of recrystallisation experienced by a material is heavily impacted by the parame-ters at which the material was deformed. Recrystallisation is driven by the energy stored in the material as a result of deformation processes. It has been found that materials deformed at higher strain rates (ϵ˙) possess increased levels of strain accumulation, and therefore experience elevated levels of recrystallisation when exposed to temperatures (T ) greater than 50% of the materials absolute melting temperature. However, it has also been determined that recrystallisation can be minimised, if the material is deformed at low strain rates and low temperatures [36]. The objectives of this research are to use the simulated hot rolling and in-situ creep data acquired from the Gleeble, to determine threshold values for Z and the deformation parameters, that will result in material slabs which possess a resistance to creep. Plane strain compression tests were performed on a Gleeble 3800 at deformation strain rates and temperatures in the range of ϵ˙ = 1 − 21s−1, and T = 420 − 500◦C, to assess the effects varied parameters had on the creep experienced by the slabs as well as the level of recrystallisation produced in the resulting microstructure of the material. The effects of strain rate and temperature during hot deformation were represented by Zener-Hollomon as well as Arrhenius-type values. These values were compared with the creep strain experienced by samples to identify a threshold value for Z above which creep was minimised. A series of micrographs were acquired to assess the level of recrystallisation experienced by samples deformed at certain parameters. The results from these micrographs were compared with the creep results to highlight the relationship between the deformation parameters and the resulting recrystallisation and creep experienced by the material. Tests performed at deformation parameters which resulted in Z ≥ 1e14 or ln(Z) ≥ 32 were found to experience less recrystallisation and hence were more resistant to creep. It was also found that samples deformed at T > 450◦C experienced significantly more creep than samples that were deformed at T ≤ 450◦C. In both temperature ranges, higher ϵ˙ values commonly resulted in samples experiencing more recrystallisation, and this was heavily accentuated at T > 450◦C. The threshold values required for creating a creep resistant slab of AA3104 during hot rough rolling are Z ≊ 1e14, ln(Z) = 32, and T = 450◦C. Materials deformed at parameters resulting in Z ≥ 1e14 or ln(Z) ≥ 32 will result in a creep resistant slab of material if the deformation temperature T ≤ 450◦C. However increased values for strain rate ϵ˙, will still result in more recrystallisation being experienced by the material, even at T ≤ 450◦C, therefore higher ϵ˙ should be avoided where possible.
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Open Access
Pacing patterns of female runners in the Comrades marathon “down run”: a retrospective descriptive research design
(2026) Preen, Tessa Joan; Bosch, Andrew
Appropriate pacing is considered optimal for successful endurance performance (Casado et al., 2021a). The Comrades Marathon has been subject to multiple studies (Boulter et al., 2011, Coetzee et al., 2022, Hagemann et al., 2008, Nikolaidis and Knechtle, 2019, Woyo and Nyamandi, 2022); however, there are currently no published studies on the pacing patterns used by runners in the Comrades Marathon. Aims: This study aimed to determine the pacing patterns of the fastest through to the slowest female runners in the Comrades Marathon “down” run, between the years 2016 and 2023. This will be conducted by analysing the pacing patterns to determine if the pacing patterns differ between runners of different abilities, and to determine how their pace changes between different sections of the race. Methods: Results of all the female finishers of the Comrades Marathon who fulfilled the inclusion and exclusion criteria were combined into a single spreadsheet. The data was separated into four groups, based on time, from fastest to slowest. Race pace was analysed using a Generalised Linear Mixed Effects Model (GLMM) to determine any statistically significant differences. Pairwise comparisons and post-hoc tests utilizing the Bonferroni method were then used to determine which average paces demonstrated statistically significant differences (p<0.05). Results: 7818 results were analysed. The mean race time for all female participants was 10:40:57 (hh:mm:ss). The faster runners (group A) showed the least variable pacing pattern, while the slowest runners (group D) showed the most variable pacing pattern. The pacing pattern used was variable, with runners showing decreased pace in segments 4 and 6 from the mean race pace. Conclusion: The pacing patterns differ between runners of different abilities. The greatest differences of average pace were seen in the first 30km, where the slower runners ran at significantly higher percentages of their average race pace. It is evident that the course profile significantly affected the pacing selected by the participants. All athletes had significant speed reductions in segments 4 and 6.
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Open Access
Ecopsychology in South Africa: public perceptions and professional applications of nature-based therapy in the Western Cape
(2026) Pienaar, Andrea; Spedding, Maxine; Pileggi, Lea-Ann
Ecotherapy, a form of nature-based therapy rooted in Ecopsychology, is increasingly recognised for its mental health benefits. However, little is known about its application within the South African mental health system. This study sought to answer the question: What place could nature-based therapies have in the South African mental health landscape? Using a mixed-methods approach, this study explored the perspectives of two groups: licensed mental health professionals who offer nature-based therapies, and members of the public who might use them. The first phase involved semi-structured interviews with seven mental health professionals, analysed using Braun and Clarke's (2006) reflexive thematic analysis, supplemented with their more recent guidance on good practice (Braun & Clarke, 2019, 2023). In the second phase, the study examined public knowledge and interest in nature-based therapy by collecting survey data from 922 Western Cape residents. The data were analysed using a combination of content analysis and statistical methods, including descriptive statistics and inferential tests such as Chi-squared and Mann–Whitney U tests. Findings indicated that, at the time of writing, nature-based therapies were not widely practised in South Africa. Few practitioners met the inclusion criteria, and the majority of respondents had not previously participated in nature-based interventions. However, despite low public awareness, there appears to be high interest in engaging with ecotherapy. While ecotherapy remains in its early stages of development, the findings suggest potential for its expansion within the South African mental health landscape. The findings highlight a need for further development of the research base, practitioner training, and formalisation of ecotherapy practices to support its growth in the South African mental health field.
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Open Access
Investigating the association of genetic variants, previously identified by a genome-wide association study, with ACL rupture risk in multiple cohorts
(2026) Phipson, Caryn; Collins, Malcolm; Laguette, Mary-Jessica; September, Alison
INTRODUCTION Genetic variance is an important risk factor for many musculoskeletal soft tissue injuries, including ACL ruptures. Several direct-to-consumer genetic tests have emerged that claim to be able to test for susceptibility to such injuries. Only a single company uses injury-specific markers in their tests based on the findings of genome-wide association studies (GWAS), an arguably more robust and scientifically reliable approach than the candidate gene study approach traditionally used. The genetic markers identified by GWAS used to determine ACL rupture risk include rs144051132 (T/A), rs186727643 (C/T), and rs188099931 (A/G). However, their viability as reliable markers of injury risk has yet to be critically and scientifically evaluated in independent cohorts. Thus, the aim of this study was to determine whether rs144051132, rs186727643, and rs188099931 are associated with ACL rupture across multiple population groups. METHODS A genetic association study, comprising cases clinically diagnosed with ACL rupture (ACL), a subset of cases who had sustained an ACL rupture via a non-contact mechanism (ACL-NC), and a control group (CON), was conducted whereby participants from four cohorts of European ancestry; South African (CON=229, ACL=242, ACL-NC=161), Australian (CON=82, ACL=330, ACL-NC=149), Swedish (CON=116, ACL=95, ACL-NC=79), and Polish (CON=147, ACL=142, ACL-NC=56), as well as a South African mixed ancestry cohort (CON=105, ACL=98, ACL-NC=58), were genotyped for the three variants using TaqMan™ Genotyping assays. Genotype distributions were compared between the ACL and CON groups, as well as between the ACL-NC and CON groups. The functional effects of each variant were also analysed using multiple bioinformatics tools. RESULTS No significant associations between the three variants and ACL rupture risk were reported. Furthermore, several genotypes were either absent or rare. Specifically, the rs144051132 AA, rs186727643 TT, and rs188099931 GG genotypes were not detected. Twelve rs144051132 TA [CON(0.7%, n=4) vs ACL(1.0%, n=8), p=0.770; CON vs ACL-NC(0.9%, n=4), p=0.819], one rs186727643 CT [ACL(0.1%, n=1), p=1.000], and six rs188099931 AG [CON(0.2%, n=1) vs ACL(0.6%, n=5), p=0.410; CON vs ACL-NC(0.7%, n=3), p=0.448] genotypes were identified across the European cohorts. In the South African mixed ancestry cohort, three rs144051132 TA [CON(0.9%, n=1) vs ACL(2.0%, n=2), p=0.611; CON vs ACL-NC(2.0%, n=1), p=0.489], eight rs186727643 CT [CON(2.8%, n=3) vs ACL(5.1%, n=5), p=0.486; CON vs ACLNC(2.0%, n=1), p=0.092], and one rs188099931 AG [CON(0.9%, n=1), p=1.000] genotypes were identified. All three heterozygote genotypes were absent from the Swedish cohort, while rs186727643 CT and rs188099931 AG were absent from the Polish cohort. The rs186727643 CT genotype was also absent from the South African cohort of European ancestry. CONCLUSION In line with these results, the scientific evidence is too weak to support an association between ACL rupture risk and rs144051132, rs186727643, and rs188099931. The observed rarity of the effect allele suggests that the use of these variants as reliable markers of ACL rupture risk is not yet viable, and this dissertation does not support their inclusion as markers of injury risk in a direct-to-consumer genetic test.
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Open Access
Exploring the lived experiences of unemployed youth in a youth unemployment programme in Gauteng
(2026) Phihlela, Boitumelo; Hoosain, Shanaaz
The purpose of this study was to explore the lived experiences of unemployed youth participating in a youth unemployment programme in Gauteng. The unemployed youth are in a vulnerable position where employment in South Africa is limited. The study aimed to understand and explore how unemployment has affected the unemployed youth, more specifically those enrolled in an unemployment programme in Gauteng that seeks to develop the skills of this group to position them in the economy. The methodology used was a qualitative method of obtaining data. The researcher used individual in-depth interviews to explore the lived experiences of the unemployed youth. The researcher recorded the interviews because noting taking would be distracting to both the interviewer and the interviewee. Using an audio recording device also allowed the conversation to flow without hindrance, and the dialogue to flow freely. As the data was being collected, a code number or pseudonym was used to protect each participant which decreases the possibility of their identity being leaked. This was also used to ensure that the data remains anonymous. The raw data was stored in a Google Drive that was accessed by the researcher. The main findings of the research found that unemployment stripped away the dignity and identity of the unemployed youth. For some, it placed them in a position where they were no longer able to do anything for themselves and their families which made them question their human agency. Unemployment affected the unemployed youth in a physical, mental, emotional and financial manner. However, the youth unemployment programme gave the unemployed youth something to look forward to while equipping them with the necessary skills for their future employment. The recommendations included for more queries on employment programs, policy makers support for unemployed youth and more government-led initiatives to include psychosocial support.