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Self-attention policy architectures for reinforcement learning under partial observability
Get PDFIntermittent unavailability of sensory signals due to sensor failure and/or latency is a problem encountered in production environments such as in large manufacturing plants, for example. Deep reinforcement learning offers a natural solution for process control and optimisation in such environments. However, a shortcom-ing of conventional agent policy architectures in this instance is an inability to handle variable-sized inputs composed of available sensory signals, thus requiring the imputation of unavailable sensory signals with data which necessarily constitutes noise. We explore self-attention-based policy architectures as a solution to this problem, demonstrating their robustness under conditions of high partial observability on different rein-forcement learning benchmark tasks, and explore the advantages and disadvantages offered by our solution over conventional policy architectures. Additionally, we propose a novel hard attention mechanism, used in conjunction with our proposed policy architecture, enabling the agent to attend to the most salient sensory signals and allowing for greater interpretability of the agent's decision-making
A comparative analysis of the medicine use and exposures in infants who are HIV exposed uninfected and HIV unexposed uninfected in the first year in Cape Town, South Africa
No full textBackground: Despite several studies investigating medicine exposures in infants, the administration and monitoring of medications in infants who are HIV-exposed uninfected (HEU), a growing population, remains poorly studied. This study aimed to describe and compare medication consumption patterns, including immunization coverage, between infants who are HEU and HIV-unexposed uninfected (HUU) during their first year of life. Methods: This was a secondary analysis of a birth cohort study of pregnant women living with and without HIV and their infants between 2017 and 2019 in Cape Town, South Africa. Interviewer- administered questionnaires captured sociodemographic factors, self-reported medication use, infant feeding practices, and vaccine use over four postnatal visits (<7 days, 10 weeks, 6 and 12 months). Data was manually classified and coded by a clinical pharmacist and student. Logistic regression models were employed to compare patterns of use among infants who are HEU and HUU, as well as identify other maternal and infant factors associated with medication use and vaccine coverage. Findings: A total of 772 mother-infant pairs were analyzed. Compared to infants who are HUU, HEU infants were preterm (64/393 vs. 39/379; p = 0.02), less often breastfed (314/393 vs. 322/379; p <0.001), and weighed less (median, 3288g vs. 3405 g; p = 0.03). HEU infants were found to take at least one medication at a significantly higher rate 388/393 (98.7%) vs 345/379 (91.0%) than infants who are HUU (p <0.001). HEU infants reported lower use of over-the-counter (OTC) medicine (69.2% vs. 80.2%; p <0.01) and traditional, complementary, and alternative medicine (TCAM) (16.8% vs. 26.1%; p <0.001) compared to HUU infants. Mothers of HEU infants were less likely to forget a medicine's name (29.3% vs. 36.9%, p<0.001) than HUU mothers. Prescription medicine use, excluding antiretroviral (ARV) prophylaxis medicines routinely administered to infants who are HEU at birth, was significantly higher among infants who are HEU compared to HUU (65.4%. vs. 23.0%; p <0.01). Vaccine coverage showed no significant difference between infants who are HEU and HUU but steadily declined over the year (95.0% coverage with birth immunizations, vs 70.0% at 9 months) across the entire cohort. Only 293 infants (38.0%) had complete immunization coverage at 1 year. In the adjusted models, being a HEU infant was a protective factor against self-medication. (aOR 0.45; 95% CI 0.31 –0.65; p <0.001). Conversely, being breastfed (aOR 2.46; 95% CI 1.56 –3.83; p <0.001) was a significant risk factor for self-medication infants. Prescription medicine use (excluding ARV prophylaxis medicines) was significantly associated with increased maternal age (aOR 1.06; 95% CI 1.03 – 1.08; p <0.001) and infants who are HEU (aOR 6.52; 95% CI 4.66 – 9.21; p <0.001). No significant associations were found between maternal and infant characteristics and full vaccine coverage. Interpretation: The study revealed that infants who are HEU were more exposed to prescribed medicine (excluding ARV prophylaxis medicines) compared to their HUU counterparts, however, mothers of HUU infants, generally reported higher usage of both TCAM and OTC compared to HEU infants. The study also revealed drops in vaccine coverage rates among infants over the first year of life, indicating a gap in protection against vaccine-preventable diseases. Further research is needed to study medication patterns in different settings. Medication literacy efforts need to be prioritized in pregnant women and mothers of newborns to support rational and safe medicine (including vaccine) usage and subsequently improve the health outcomes for all infants, irrespective of HIV status
Readiness of public libraries to deliver information literacy instruction to school children: a case study of a City of Cape Town public library
Get PDFInformation literacy (IL) is an integral part of lifelong learning. IL instruction is accepted internationally as the specific mission of school libraries. However, in South Africa, there are few schools that have functional school libraries, and so it is unrealistic to put the IL instruction responsibility on school libraries. Therefore, public libraries need to step in and close the IL gap. However, it is not clear how well equipped public libraries are for this role. To examine the problem above, the main objective of this study was to investigate the readiness of public libraries to offer IL support to school learners. The Big6 model guided data collection in this study in terms of the formulation of the interview questions for librarians, and the observations guide. Under the interpretive paradigm, this study employed a qualitative research approach with a case study design. The case is that of a public library referred to as the Library in this study. The Library is an example of one library in the City of Cape Town and the researcher was interested in providing an in-depth study of this library with regards to IL instruction support for school learners. One of the reasons it was chosen is because there are a number of schools in the area in which it is situated. The populations for the study were the public librarians working at the Library and schoolteachers from the surrounding primary and high schools. There was no sampling required for public librarians because their population was manageable. However, non-probability sampling was employed for schoolteachers, coupled with purposive sampling. The data from the public librarians were collected through semi structured interviews and observations, while the data from the schoolteachers were collected through semi-structured interviews only. Data were analysed manually. Findings indicated that the majority of the librarians in the study have a combination of work experience and LIS qualifications (though some were obtained a long time ago), which contributes positively to their readiness to teach IL. The findings of the study revealed that there is no sustained programme that is explicitly referred to as IL at the Library. However, librarians at the Library offer IL support to school learners and IL support for school learners is embedded in various library programmes, such as library orientation, digital literacy, storytelling, and the homework assistance, reading and holiday programmes. The findings also showed that the librarians in the study generally have a positive attitude towards teaching IL to school learners, although they acknowledged that they are not teachers by profession. Furthermore, it was revealed that while there was no collaboration between the Library and one of the primary schools in the study, the Library does collaborate with some of the teachers from the other schools. It is hoped that this study will contribute to the body of literature, particularly that of information literacy education for school children in public libraries
Re-imagining a child-centric spatial environment that promotes quality of life for children in Altantis (Witsand)
Get PDFThis study investigates how Urban Design can promote quality of life for the development of children in Atlantis (Witsand). Altantis is located 45 kilometers north of Cape Town, Which is a long distance from the economic city centre. Atlantis was created in the early 1970s as a “model industrial node” within the framework of apartheid spatial development policies. These policies were designed to physically separate and divide South Africans along racial lines of Cape Town. Acknowledging the significance of integrating children's development/ upbringing in urban design research can bridge the disconnect between the urban fabric and educational facilities to promote child-centric urban development. Employing a qualitative research approach, including social mapping, text mapping, desktop context analysis, site observations through a periscope, and interviews of subjects except, ECD operators, Caregivers, and program coordinators from CoCT. The study aims to employ urban design theories and tools to redress spatial challenges or negative effects apartheid-era urban planning in Atlantis to create a child-centric spatial environment, promote the safety of children, and promote consistent learning and the quality of life of children. The spatial characteristics will be investigated to develop urban design intervention that will assist in addressing challenges in Atlantis particularly in the neighborhood of Witsand. When dealing with disadvantaged neighborhoods like Witsand, it will be vital to observe urban design theories such as tactical urbanism to ensure interventions are realistic and impactfulon communitie
The taxation of 'Influencers' in South Africa and in an international context
Get PDFSocial media has changed as a result of the digital economy's explosive expansion, turning it into a powerful tool for both individuals and businesses alike. Influencer marketing, a product of this digital era, has achieved remarkable success. With their dynamic and multifaceted lives, social media Influencers have become an integral part of the digital economy. However, existing international tax rules lack specific provisions addressing Influencers, raising questions about their tax treatment and the potential for treaty abuse. This underscores the necessity of exploring how the Influencers are to be taxed within the current legal frameworks, both from a local and international point of view. Following the introduction of fundamental concepts essential for understanding the activities and income generation means of Influencers, this document delves into an exploration of the local and international tax implications for these individuals. In the local context, an examination of current South African tax laws applicable to Influencers is undertaken. Additionally, in the international sphere, an in-depth analysis of their activities is conducted within the framework of the Organisation for Economic Co-operation and Development on Income and Capital Model Tax Convention (“OECD MTC”). Upon examination of the activities and income streams of Influencers from both a South African and international perspective, it became evident that their taxation is guided by existing legislation rather than specific provisions tailored for them. In South Africa, the classification of Influencers as employees or independent contractors holds crucial implications for their tax treatment. Notably, the taxation of promotional gifts, whether received for consideration or not, emerges as a critical aspect, subjecting Influencers to taxation due to their provision of marketing or advertising services. On the international front, existing rules, with the exception of the debate around Article 17 of the OECD MTC, are deemed sufficient for encompassing Influencer activities. The choice between Article 7 and Article 17 depends on the nature of the Influencer's activities. The various income streams of Influencers, from commission income to fees for services rendered and the sale of goods, fall within the scope of Article 7. The examination of Influencer activities under Article 17 is particularly relevant when they entertain followers through live social media posts. The conclusion underscores that Influencers face similar cross-border challenges as other taxpayers. Still, it emphasises the need for careful identification of their income streams to ensure proper application of double tax treaties and to avoid potential issues of double taxation or double non-taxation. The unique lifestyle of Influencers may lead to scenarios of double taxation, and them seeking visas in lower-tax jurisdictions since most of their income is subject to taxation in the Country where they are tax resident. The ongoing discussions regarding the taxation of Influencers are of crucial importance, particularly in light of evolving dynamics within the digital economy and their substantial potential for tax collection. This underscores the importance for Tax Authorities to provide clear guidance in navigating this intricate landscape for Influencers
Investigating the structural and cultural conditions that reproduce coloniality and inhibit decolonisation at a private higher education institution in South Africa
No full textThis qualitative research study seeking to establish the structural and systemic inhibitors of decolonisation at a South African Private Higher Education Institution (PHEI), adopted a Critical and Social Realism theoretical framework while employing a critical discourse analytical approach. Working within an interpretive paradigm, the study gathered data through semi-structured interviews involving the PHEI lecturers whose agential association purposively placed them at vantage points to assess the structural and cultural elements that stunt the progression of transformation. The study established that the absence of institutional commitment to decolonisation informed the lecturers' peripheral influence in executing a decolonisation agenda. It was also established that the lecturers' perceptions of decolonisation did not progress beyond intellectual and academic pronouncements and as such, institutional structure and culture continue to inhibit decolonisation. That lack of depth on the part of lecturers compromised their competence to pronounce on apparent structural and racial configurations manifest in the institution. The study recommended further investigations that would triangulate the experiences of multiple stakeholders in a bid to propose a framework that would foreground decolonisation and curriculum change as a central concern
Volatility spillover between Exchange-Traded Funds on the Johannesburg Stock Exchange
Get PDFGrowth in the Exchange-Traded Fund industry (ETF) has been exponential in the past decade. International research on this topic has been extensive, with less focus given to the local Johannesburg Stock Exchange (JSE). This research aims to extend the existing literature on the JSE, particularly focusing on the volatility spillover between domestic ETFs representing four major asset classes and four equity ETFs using the Diebold and Yilmaz (2012) Spillover Index. The equity ETF system includes the Satrix RESI 10 (STXRES), Satrix FINI 15 (STXFIN), and Satrix Capped INDI (STXIND). Four ETFs are selected as proxies for equities, bonds, commodities, and property. The ETFs representing the asset classes are the Satrix 40 (STX40), Satrix GOVI (STXGVI), ABSA NewGOLD (GLD), and 1Invest SA Property (ETFSAP), respectively. These two volatility systems are examined independently. The results show that the STX40 ETF is a net volatility transmitter in the alternate asset ETF system. Within the equity ETF system, the STXFIN and STXRES are net volatility receivers, and the STXIND fluctuates between receiver and transmitter of volatility over the period analysed. In the alternate asset system, ETFSAP and STXGVI are net volatility receivers, with the GLD ETF oscillating between being both a net receiver and transmitter. Furthermore, the Chicago Board Options Exchange Volatility Index (VIX) index is used to proxy foreign volatility shocks to South African financial assets. Approximately 12,5% of volatility for the full set of ETFs can be attributed to the VIX. Additionally, a regression analysis is employed to evaluate the VIX as a significant explanatory variable for measuring volatility propagation through the chosen ETFs, with the results confirming its significance solely in the equity ETF system. This study adds to the existing literature on portfolio allocation decisions by focusing on sector rotation and asset allocation strategies. Additionally, it provides insights into the diversification opportunities that JSE investors can benefit from using ETFs. The study includes periods of financial market volatility, driven by significant macroeconomic events, such as Britain's referendum vote on European Union participation, the COVID-19 pandemic, and the conflict between Russia and Ukrain
Investigation into implementing a massively parallel sequencing workflow for forensic human identification in South Africa
Get PDFSouth Africa faces grave challenges with high crime rates and associated unidentified bodies each year. DNA profiling using capillary electrophoresis (CE) is typically utilised for human identification purposes but is limiting when applied to degraded post-mortem samples. The ForenSeqTM DNA Signature Prep kit was the first massively parallel sequencing (MPS) workflow validated on the MiSeq FGxTM system, addressing several challenges identified in CE-based methods. With forensic laboratories in developing regions showing proclivity towards a seemingly impossible adoption of MPS, sequence-based studies in Africa are sorely needed to leverage emerging advancements for forensic human identification. This study proposed a four-phased approach for laboratories to facilitate the implementation of MPS for forensic human identification, and included: optimisation, population data generation, internal validation and demonstration of applicability. An optimisation study was carried out to ensure high first-time success rates of analysing reference samples (crude buccal swab lysates) with the ForenSeqTM DNA Signature Prep kit. This entailed systematic adjustments to a direct PCR approach and the development of a lysate purification method. This optimised approach was subsequently used to conduct a population study comprising 463 consenting South African volunteers, wherein the first sequence-based allele frequency data pertaining to autosomal short tandem repeat (A-STR) markers were generated for South African populations. Rich variation was observed, where 80 novel allele sequences were recorded. An increase of 86% was observed in length- to sequence-based allele counts across several A-STR markers, with additional variation recorded in flanking regions. Furthermore, a concordance rate exceeding 99% was achieved. The novel findings and abundance of variation observed in the South African population surpasses that which has been previously characterised on a global scale, warranting further research into characterising sequence data for other forensically relevant markers. The final facet of this study involved the internal validation of the optimised MPS workflow, from sample preparation to sequencing. The workflow was deemed fit for purpose and reported the first performance parameters for post-mortem crude buccal swab lysates. The validated workflow was then applied to a forensic cold case to generate investigative leads from a severely decomposed body, demonstrating the comprehensive capability of the workflow. The synthesis of results obtained in this study have led to key recommendations for under-resourced laboratories to maximise resources for large-scale studies
An exploration of recovery among persons with severe mental health conditions in South Africa
Get PDFBackground Severe mental health conditions have long-term impacts on multiple stakeholders, especially in low- and middle-income countries. Historically, public mental health services have focused on symptom reduction, emphasising clinical recovery. However, personal recovery, which considers mental health service users' lived experience, has received little attention. Since contextual factors influence outcomes, understanding and measuring recovery in low-resource settings is crucial. This study sought to explore personal recovery from severe mental health conditions in South Africa, where challenges, including poverty, stigma, and limited mental health resources intersect to shape the recovery process. Aim and objectives The overarching research question underpinning the thesis was: What constitutes and facilitates recovery for persons living with severe mental health conditions in South Africa? I aimed to answer this question and contribute to closing the research gap by pursuing four research objectives: (i) To conduct a scoping review on how personal recovery is conceptualised for persons living with severe mental health conditions in low- and middle-income countries; (ii) To explore and describe service provider perspectives on what recovery is for persons with severe mental health conditions in South Africa; (iii) To explore and describe what recovery is for men with severe mental health conditions and their caregivers in South Africa; and (iv) To evaluate the psychometric properties of the Recovery Assessment Scale among persons with severe mental health conditions in South Africa. Methods This mixed-methods study included both qualitative and quantitative components. Initially, a scoping review was undertaken to explore how recovery from severe mental health conditions is conceptualised and facilitated in low- and middle-income countries. Ten articles were included and thematically analysed. Next, semi-structured interviews and focus groups were conducted with 17 service providers in the Western Cape. This qualitative phase also included interviews with four male mental health service users and three of their caregivers. Visual participatory methods such as photovoice and life graphs were used to collect data. Finally, a quantitative evaluation was conducted to assess the psychometric properties of the Recovery Assessment Scale among 250 South African mental health service users. Results The scoping review revealed that recovery from severe mental health conditions is perceived as a continuous, non-linear process. While high-income countries focus on autonomy and independence, low- and middle-income countries emphasise social ii connectedness and spirituality as key recovery elements. Service providers suggested that clinical recovery models dominate mental health care, but personal recovery requires an approach that addresses social, economic, and cultural inequalities. For mental health service users, long-term relational support was vital to recovery. Even though spirituality was crucial to recovery, stigma from faith-based communities sometimes hindered access to spiritual support. Finally, the psychometric evaluation of the Recovery Assessment Scale showed a five-factor structure, with “Empowerment and Inner Strength” emerging as a new factor. The adapted Recovery Assessment Scale demonstrated strong internal consistency and reliability, proving a suitable tool for measuring recovery in South Africa. Discussion and conclusion The findings were synthesised into the Recovery Mandala, which identifies seven interconnected elements central to recovery from severe mental health conditions in South Africa: Collaborative Co-creation, Person-Centeredness, Hope and Empowerment, Social Network Utilisation, Caregiver Involvement, Spirituality and Religion, and Employment. These elements reflect the relational and holistic nature of recover
Unravelling the palaeobiology of the dinosaurian post crania and associated carnivore teeth from the early jurassic, Elliot formation in the Eastern Cape
Get PDFThe Elliot Formation of the Stormberg Group of South Africa ranges in age from the Late Triassic to the Early Jurassic. This stratigraphic unit bears a varied dinosaur assemblage, among which sauropodomorph dinosaurs are the most abundant. Sauropodomorpha are particularly well documented in the Upper Elliot Formation and are morphologically and taxonomically diverse. Specimen AM 6147, a large basal sauropodomorph, was excavated from the Barkley Pass, Eastern Cape, Elliot Formation of South Africa in 2013 by a joint team from the Albany Museum and the University of the Witwatersrand led by Dr Billy de Klerk. The specimen comprises post cranial material including ribs, gastralia, vertebrae of the mid-posterior section of the tail, and a complete left pes. Associated with the specimen are three teeth of contemporaneous carnivores. Here, we describe the skeletal anatomy of AM 6147 and assess its phylogenetic affinities by scoring our findings in a phylogenetic data matrix. We also attempt to identify the carnivorous taxa to which the associated teeth may have belonged, and the nature of the relationship between them and AM 6147. Our phylogenetic analyses reveal that this specimen belongs to the Massospondylidae and that it is recovered as a new taxon, Enkulusaura deklerki, based on a unique combination of plesiomorphic and derived features. Our findings suggests that the three associated carnivore teeth could possibly belong to two different theropod dinosaur, while the third tooth is likely from a crocodylomorph. In conclusion, this study of AM 6147 shows that it is a new large bodied Massospondylid from the Elliot Formation and provides a better understanding of the diversity of basal Sauropodomorpha in the Early Jurassic of South Africa. Furthermore, the associated teeth contribute insight into the ecological relationships between these contemporaneous taxa