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Using deep learning to characterise weak signals in global equity markets: a case study of COVID-19
Get PDFThis study examines the use of deep learning to identify and characterise anomalous events and their preceding weak signals in equity price data. Particular interest is placed on Gray Rhino events, indicated by the presence of progressively stronger signals prior. The market behaviour prior to and during the COVID-19 pandemic on G-20 equity markets provides a useful context to this end. Existing literature has examined the effects of the pandemic on these markets but has yet to provide conclusive insights into the development of the major equity crash. We compare the existing literature concomitantly to our rigorous application of event study methodology, identifying the presence and effects of signals prior to the market crash. In addition, we develop and deploy a novel Anomaly Characterisation Process (ACP). The ACP utilises an ARIMA time series model to transform equity price time-series for the extraction of relevant information, whereby subsequent fits of GJR-GARCH and deep-undercomplete-autoencoder models are deployed. Resultantly, measures of dispersion and atypicality are produced which allow for effective and clear characterisation of the degree of typicality of the equity prices and their movements. This innovative method demonstrates efficacy in detecting both point and contextual anomalies. When applied in the context of COVID-19, the findings suggest that different event types can be distinguished successfully with this novel approach through the identification of weak signals. Notably, these insights of the ACP in conjunction with those of the event study suggest that the COVID-19 market crash is consistent with a Gray Rhino event and not a Black Swan event. We briefly demonstrate that these insights can be used by market participants to improve risk-adjusted returns via ACP-informed risk-mitigation techniques
The correlation between cranial fractures and brain trauma: a retrospective study
Get PDFTraumatic brain injury (TBI) is a global public health concern. TBI has been noted to co-occur with cranial fractures, however this is not always case. At present, there is a gap in literature regarding the correlative relationship between the presence of cranial fracture and brain trauma. The knowledge and understanding of this correlation is imperative for autopsy examinations where pathologists have to determine the cause of death of an individual. Furthermore, in cases where the skeleton is the only tissue that is available for examination, anthropologists will be able to apply this knowledge to infer the presence of brain trauma at death. Therefore, the current study aimed to assess the correlation of cranial fracture and brain injury in cases of blunt force trauma. This was achieved through a retrospective review of blunt force head injury cases of blunt force head injury examined at Salt River Mortuary, Cape Town between 01 January 2015 and 31 December 2019. Co-occurrence of cranial fractures with brain trauma was prevalent in the current study, accounting for 64% of the recorded cases. A significant association was found between age at death and the presence of brain trauma (p = 0.042), with majority of individuals with brain trauma ranging between 18 to 49 years of age. Similarly, a significant association was found between the presence of cranial fractures and age (p = <0.001). A significant association was found between the presence of cranial fractures and brain trauma to the frontal, parietal and temporal lobes (p = <0.001). Moreover, fracture type was significantly associated with the presence of brain trauma. Fractures of the cranial base have an increased risk of being associated with traumatic brain injury compared to the fractures in other regions. Individuals presenting with cranial fracture are 4.48 times more likely to have TBI, compared to those without cranial fracture. Specifically, individuals with fracture of the basal region of the cranium are 3.77 times more likely to have co-occurring TBI. Notably, all cases of hinge fractures had associated brain trauma. The data presented in this study can be used for the prediction of the presence of brain trauma, where the presence of cranial fracture is noted
Investigation of ride-share service decisions with uncertainty and perceived risks: Case study of young adults in Cape Town, South Africa
Get PDFRide-share services could help young adults avoid or delay car ownership by meeting the individuals' immediate demand for personalised private vehicle transportation. However, little is known about how young adults in South Africa, and specifically Cape Town, decide on rideshare service trips involving uncertainty and perceived risks (trips ‘at night', ‘alone' and ‘alone at night'). Using the Quantum Probability Theory concepts of Belief State and incompatibility, this research aims to better understand the influences of Gender (female, male), Access to a Private Vehicle (access, no access) and COVID-19 (‘before', ‘during', ‘after') in ride-share service decisions that involve personal security uncertainty and perceived risks in Cape Town. Evidence for incompatibility in decisions is explored using pre-questions of related Transport Factors (Sustainable Transport, Reliability, Road Safety, Crime). Additionally, positive framing questions, potentially affecting the Belief States, are tested using unrelated pre-questions, namely the Good Mood Questions. These investigations are explored through four experiments, via online surveys using Google Forms, distributed to the university community. The differences in willingness to engage in ride-share service trips ‘at night', ‘alone' and ‘alone at night' are most pronounced for Gender, however, differences per Access to a Private Vehicle and COVID-19 were also significant. Furthermore, ‘after COVID-19' indicated a significant drop in willingness to use ride-share services for these trips. The strongest evidence of incompatibility was found in females indicating impactful levels of uncertainty and perceived risks in their ride-share service decisions of ‘at night', ‘alone', and ‘alone at night'. However, limited evidence of positive framing effects was found using the Good Mood Questions for both females and males in the COVID-19 scenarios. Overall, the implications of these findings for ride-share service providers are that there is a need for more measures to improve personal security for females when taking trips ‘at night' or ‘alone at night'. While this research is limited by the scarcity of data from ride-share service companies, future research can expand on these findings by including more diverse population groups, especially lower-income groups, for more representative knowledge of the larger Cape Town population
Influence of symmetry on the stability behaviour of plane and space frames
Get PDFSymmetry refers to a property of an object or a system that remains unchanged or invariant under a transformation, such as reflection, rotation, or scaling. This study sought to investigate how symmetry influences the buckling behaviour of open frames as well as closed polygonal and prismatic frames. This was achieved by employing analytical methods developed in this study and the finite element method to study plane and space frames. The analytical results were used to validate the finite element models developed in Abaqus. The finite element models were then used to carry out more detailed studies on the influence of symmetry on the stability behaviour of plane frames. In addition, the study also proposed an alternative method for tracing the post buckling paths of lattice domes. Two group theoretic approaches to the buckling analysis of plane frames were developed based on the matrix stiffness method, and slope deflection method respectively. This was achieved by using group theory to decompose an n-dimensional problem into smaller independent problems of much smaller dimensions. The buckling loads and mode shapes are then computed with much less computational effort and numerical problems of ill conditioning are avoided. This was very useful for the group theoretic slope deflection approach developed in this study. The group theoretic slope deflection approach was used to obtain analytical results for the buckling loads and modes of plane frames. Another advantage of the group theoretic approach developed was that insights on the symmetry of the buckling modes were obtained even before detailed computations for eigenvalues are carried out. The analytical results obtained from the group theoretic slope deflection method were used to validate Finite element models created in Abaqus of the Cnv plane and space frames, and Dnh space frames. These finite element models were then used to conduct more detailed investigations of the influence of symmetry on the stability behaviour of plane and space frames. This study found that for plane frames symmetric to a Cnv group in terms of stiffness and loading, the lowest buckling load had an eigenmode with the symmetry of a subgroup of Cnv with the highest order of elements. The study found that the order of emergence of symmetries for eigenmodes of higher eigenvalues was from the subgroups of Cnv with the highest order of elements to those with the lowest order of elements and this order of emergence repeats every 2n eigenvalue. The study also found that when eigenvalues are categorised by the symmetry group of their eigenmodes, eigenvalues whose eigenmodes have the symmetries of subgroup of Cnv with the highest order of elements, formed the lower bound eigenvalues; and the eigenvalues whose eigenmodes have the Cn symmetries formed the higher bound eigenvalues. Further, this study found that when the group index of an eigenmode is greater than two, the respective eigenvalue is a repeating eigenvalue; and that when the group index is equal to two, then the respective eigenvalue is non-repeating. This study also found that space frames that are Cnv symmetric in terms of stiffness and subjected to a loading arrangement symmetric to a subgroup of Cnv, display the buckling behaviour of a frame that is symmetric to that particular subgroup in terms of stiffness and loading. Lastly this study found that, plane frames that are Cnv symmetric in terms of loading and subjected to Cnv/2 loading display the buckling behaviour of a plane frame symmetric to Cnv with respect to loading and stiffness for the case where n/2 is even. Some of the findings of these two approaches (matrix formulation and slope-deflection) have already been reported in a publication of the American Society of Civil Engineers, and presented at an international conference. For laterally unrestrained Cnv symmetric space frames, this study found that for n>2: the buckling mode for the lowest buckling value is C1v symmetric and the frame sways along one line of symmetry; and the lowest buckling value is a repeating buckling value. For Dnh symmetric space frames in terms of stiffness and loading, the post-buckling behaviour was investigated in addition to the buckling behaviour. Such space frames were found to display the following stability behaviour: the symmetries of the buckling modes are subgroups of Dnh; the order of emergence of symmetries of buckling modes repeats every 4n buckling value; the buckling values whose buckling modes have the Cn symmetries form the higher bound buckling values when all buckling values are arranged by buckling mode symmetry. This study also found that space frames that are Dnh symmetric in terms of stiffness and subjected to a loading arrangement symmetric to a subgroup of Dnh, display the buckling behaviour of a frame that is symmetric to that particular subgroup in terms of stiffness and loading. Lastly, this study found that the post-buckling behaviour of space frames is stable and is independent of the beam to column stiffness. This study also demonstrated how the post buckling equilibrium paths of lattice space domes can be traced using a load excitation method, without having to use special path switching algorithms. In this method, the pattern of the applied load arrangement to excite a particular bifurcation path is based on the symmetry of the deformation pattern of the dome on that particular bifurcation path. Thus, the post buckling equilibrium paths can be traced by simply using geometric non-linear analysis in a Finite element software such as Abaqus
Identifying risk factors for traumatic injury (TBI) due to road traffic accidents (RTA) and strategies to reduce the burden of secondary brain injury
Get PDFBackground: There is a major knowledge gap in South Africa about detailed risk factors contributing to TBI due to RTAs in children. The objectives of this study were to map the burden of disease and examine circumstantial and clinical information to inform potential intervention strategies. Methods: This was a descriptive study of patients with TBI admitted to the Red Cross War Memorial Children's Hospital in Cape Town, Western Cape. A retrospective analysis of basic demographic and clinical data were performed from a large database of children admitted with severe TBI. More detailed information about the circumstances of RTAs causing TBI were prospectively collected through interviews with caregivers. Findings: From a database of 511 paediatric patients with severe TBI (age 13 or less), 403 (78.9%) sustained injuries in RTAs, mostly as pedestrians (71.7%). Males were more often injured (66%) and the median age was 6.8 years. The median time from the accident to tertiary hospital admission was three hours, to obtaining a CT scan was 4.5 hours, and to ICU admission was nine hours. With respect to the circumstances of RTAs, 155 interviews were conducted of which 80.7% involved pedestrian incidents. In 34 incidents (22%), more than one person was injured. Among these, 19 involved parents, with 17 of them (89.5%) dying from their injuries. Among pedestrians, 62% were injured while crossing the road and 57.5% were unaccompanied by an adult. Most commonly, the injured first attended the nearest clinic or day hospital (46%) by travelling with a personal vehicle (53%). Local areas that experienced the most RTAs were Gugulethu (7.7%), Khayelitsha (5.3%) and Mitchells Plain (5.3%). Interpretation: The study indicates a high incidence of RTAs as a cause of TBI in South African children, particularly among pedestrians. The high rate of unaccompanied children crossing roads, suggests a need for improved road safety education and adult supervision. The clustering of RTAs in specific local communities' points to the need for targeted interventions in highrisk locations. The high mortality rate among parents involved in RTAs with their children underscores the broader impact of these accidents on families and communities. Funding: This work was supported by the University of Cape Town Postgraduate Funding Office and the Paediatric Neurosurgery Unit
Implementing the National Strategic Plan on Gender-Based Violence and Femicide in South Africa: The challenges of policy implementation
Get PDFThis paper examines the challenges toward implementing gender-based violence (GBV) interventions under the National Strategic Plan of Gender-Based Violence and Femicide (NSP GBVF) in South Africa. The NSP was introduced in 2020 as a multistakeholder policy to address the high levels of GBV in the country, however, has failed to reach a number of its targets in the first three years. Six semi-structured interviews were conducted with experts in the field, who have worked for organisations that run gender-based violence interventions, to gain insight into their views about the implementation of the NSP as well as GBV prevention efforts in the country. The NSP GBVF was a result of women's and feminist groups organising to bring attention to the government's complicity in the high levels of GBV. South Africa has a strong history of women's movements mobilising behind causes that impact them. Civil society organisations that focus on GBV have been in contention with the government at times, due to the lack of transparency and accountability within the government as well as the perceived lack of political urgency around issues of GBV. The relationship between the government and Civil society organisations is an important one as these organisations bring expert knowledge about the communities they work in, have the potential to increase implementation capacity and hold the government accountable when promises are not met. Currently, the gap between policy and implementation limits the effectiveness of the NSP at a grassroots level. Government needs to be held to greater accountability to ensure the adoption of the national framework at both institutional and grassroots levels. Community engagement is vital as a cultural shift in attitudes around gender and violence is required. South Africa has created gender-responsive policies since 1994, however these policies are not being effectively resourced or implemented which is why there has not been a reduction in GBV rates. The underlying structural causes of GBV need to be addressed in order to achieve results
Multi-object and multi-feature models of thumb anatomy for population based morphological assessment
No full textThe trapeziometacarpal (TMC) joint, formed by the junction of the trapezium and first metacarpal (MC1) bones, is highly susceptible to the onset and progression of osteoarthritis (OA). Although various treatment options exist to ease symptoms and slow the progression of OA, the success of these treatments is heavily reliant on the early diagnosis of the disorder. The primary aim of this research was to develop a methodology for the use of computed tomography (CT) imaging in the characterisation of biomechanical risk factors of OA in the TMC joint using data from OA-affected and control subjects. Features related to shape, pose, and intensity in the CT images of the TMC joints from the subjects were correlated to a range of biomechanical risk factors. Multi-object and multi feature-class statistical models of control and OA-affected datasets were created through the development of 3 pipelines – a registration pipeline, a correspondence pipeline, and a model building pipeline. These models were used to compare the ranges of 5 morphological anatomical measures, namely: the distances between the articular surfaces of the bones; the angle of volar beak protrusion; the angle of trapezial inclination; the surface areas of the articular facets; and the radii of curvature. In line with the respective hypotheses, the distance between the articular surfaces and the angle of volar beak protrusion were seen to decrease in OA-affected data whilst the surface areas of the articular facets were seen to increase. Contrary to their respective hypotheses, the angle of trapezial inclination was seen to decrease in OA-affected data and the radii of curvature of the articular facets showed no significant changes in morphology. This suggests certain anatomical measures may be indicative of the onset and progression of TMC OA and provides a range of values typical of both control subjects and OA-affected subjects. A third model representative of the combined OA-affected and control data was developed and used to determine the correlations between the shape and pose, and the shape and intensity feature classes. This indicated a high correlation between both the shape and intensity and the shape and pose feature classes, thus suggesting a correlation between the respective biomechanical risk factors. In summary, the results of this research suggest that a decreased distance between the articular surfaces, an increased articular surface area, and a decrease in the angle of volar beak protrusion may be indicative of the onset and progression of TMC OA. This research is limited by the relatively small size of the datasets used and thus further research is necessary to determine the variation in the trapezial angle of inclination and the change in concavity of the articular surface of the MC1. Moreover, this research serves as an explanation and demonstration of the developed pipelines in the creation of a DMFC-GPM of the TMC joint which can be applied to larger and more diverse datasets in future research to determine the correlations between the respective feature classes
Triggers, transitions, and trip decisions from 1976 to 2019: why utility cyclists in Cape Town choose to ‘ditch their cars’, and why bicycle advocacy says they should
Get PDFAlmost all cycling research in South Africa to date has focused on utility cyclists living with low incomes, the so-called ‘captive’ user who does not have access to a private car. Individual car drivers (particularly of single occupants), however, are a target of the City of Cape Town’s policy direction, which aims to grow cycling, displacing private travel, to mitigate road traffic congestion and the city’s carbon emissions profile. These utility cyclists with greater mode use options have received comparatively little research attention. Attempts to increase bicycle mode share among this cohort have so far seen little reward. The literature posits that to shift cycling practices in low-cycling countries, there is value in considering the role and influence of narratives of cycling choices, and in understanding what cycling means and why it is already attractive to those who do choose to cycle in low-cycling contexts. To this end, this research selects individuals from within this group of car-owning middle to high-income adults in Cape Town who do cycle as transport (‘choice’ or intentional cyclists), and examines why they started cycling and what has motivated them to shift and sustain their cycling practice in their adult life. It does so through in-depth interviews with intentional cyclists (n=36) and a survey of individuals (n=36) who share characteristics with the above but who ride as sport only. Interviews were captured as mobility biographies, and segmented in terms of Prochaska and DiClemente’s Transtheoretical or Stages of Change model. Using thematic and narrative analysis, the research considers how cyclists frame the triggers and motivations for adopting, increasing, and maintaining their cycling practice, and whether these motivations differ at different behavioural stages. Qualitative method, and particularly a narrative approach, is well suited to exploring and gaining an in-depth understanding of a specific group of people, such as this group of interest. The research then compares these motivations to the arguments engaged in the advocacy discourse (media, speeches, official policy, civil society activism, letters to the press) regarding the value of bicycle transport and why individuals ‘should’ adopt this mode. Analysis was underpinned by theories of individual behaviour change, including Triandis’ Theory of Interpersonal Behaviour, and Ajzen’s Theory of Planned Behaviour. Key findings are that of the individuals who do cycle as transport, most cycled during childhood; a substantial number kept cycling if they attended university and also for sport. It is rare for an adult new to cycling to use a bicycle as transport. When considering ways to travel other than by car, interviewees were able to draw on memories of the freedom, ‘fun’, and joy of childhood cycling and their current sports practice. They have high levels of self-efficacy and behavioural control (with respect to capability, knowledge, social power, finances, agency), and operate within normative contexts where cycle commuting is either acceptable or encouraged, or where non-normative behaviour identifies them as part of a desired sub-culture. What influences individuals to start a cycling practice, and what influenced them to maintain it, are different. Interviewees initially are drawn to the opportunity to save money on grudge costs such as parking, to avoid driving in traffic, to supplement race training, and to make better use of time. When increasing and sustaining their practice, personal wellbeing is more motivating, as are self-concept and identity. These identities become more entrenched, and increasingly dominant motivations, the more often and for more purposes they ride. Fitness is a motivator across all stages of change. Interviewees most often increase their cycling by seeing, meeting, or riding with others who do so, than they are by other forms of advocacy; the ‘doable’ nature of bicycle transport is a more influential message than the public good that cycling might deliver. What sustains cycling practices is not so much habit but personal identity, commitment, and the wellbeing impact of cycling; where individuals are less identified as cyclists, they appear to be more likely to use their cars when circumstances are challenging. The research finds a mismatch between advocacy and individuals’ motivations, particularly during later stages of cycling behaviour. Advocacy tends to focus on the affordability of cycling, its public health benefits, its ability to ease road traffic congestion, and its social and environmental benefits. These assume altruistic motives for cycling. Among interviewees, the side-effects of carbon mitigation and the opportunity to performatively permeate social divides are welcomed but are not primary motivations. Interviewees enjoy saving money on grudge spend such as parking, but affordability, as such, is not a major concern to this cohort who own their own cars as well as relatively high-end bicycles. Implications for advocacy is that positioning cycling for this cohort as a virtuous activity is not necessarily successful, and that ‘fun’ is a legitimate reason for choosing cycling. Segmenting cyclists by stage of change, and developing interventions that might either catalyze an initial cycling practice or support a longer-term practice, is one approach. Segmenting cyclists by implicit motivation rather than by trip purpose – personal benefit, normative needs, or altruism – is another. Both the theories of Planned Behaviour and of Interpersonal Behaviour have good explanatory potential; the latter more so, as it takes into account the frequency of past behaviour, and the importance of emotion. Interviewees are mostly motivated by personal benefit, and unless an individual loves cycling, they are unlikely to cycle commute, no matter what the benefits might be
Diversification and dynamic capabilities within construction business models and their impact on firm performance
Get PDFThis study focuses on the levels of diversity within construction business models and their impact on business performance. This study examines the impact of diversification and dynamic capabilities on firm performance in the South African construction industry. The author's findings indicate a statistically significant relationship between the international diversification of construction business portfolios and both the diversification of the construction sector and the allocation of resources within construction organisations. A significant correlation exists between physical and human resources and the diversification of the construction sector. The findings provide evidence and validation for the theory of dynamic capabilities as influential factors in the value creation of construction organisations. Additionally, the study highlights the significance of both physical and human resources in ensuring the optimal performance of construction organisations. A study strategy known as "mixed methods" was used, which consisted of employing both quantitative and qualitative approaches for data collection and analysis. Survey data were collected as well as case study firms identified through rigorous qualification criteria, where further detailed observations were made and firm performance data spanning over 5 financial years were analysed and findings discussed. In summary, this doctoral thesis contributes significantly to the advancement of our understanding of construction business models and their impact on organisational performance in South Africa. The research findings presented in this study offer significant insights for both academic researchers and industry practitioners in the construction sector, regarding the interrelationships among international diversification, resource allocation, and dynamic capabilities. In addition, the study developed a programmable coded construction business model framework that enables a more comprehensive examination of construction business models and their resulting performance outcomes. Construction companies can thus make informed decisions and develop strategies to navigate a complex and changing business environment
Characterisation of surfactant protein a as a novel prophylactic means against oncogenic HPV infections
Get PDFInfection with Human Papillomavirus (HPV) presents a continuous global health challenge due to its incurable nature, particularly impacting low- and middle-income countries (LMIC). Although highly effective prophylactic vaccines targeting the most prevalent HPV types exist, they do not cover all oncogenic HPV types found in malignant lesions and the extent of cross protection against other oncogenic HPV types is limited. Moreover, these vaccines are ineffective for women already infected with high-risk HPV types. These limitations are more prominent in LMIC, where limited healthcare access, awareness, and proper transport and storage hinder vaccine accessibility. Cervical cancer's persistent status as the fourth most common cancer in women globally underscores the urgent need for alternative interventions that broadly target HPV infections. In an effort to identify alternative broad-spectrum protective means against HPV infection, our previous research identified surfactant protein A (SP-A), an innate immune opsonin, as a novel molecule capable of recognising HPV16 pseudovirions (HPV16-PsVs) with functional consequences for reduced infection in a murine cervicovaginal HPV challenge model. Building on these findings, our aim was to assess SP-A's suitability as a novel broad-spectrum HPV targeting molecule to prevent initial viral infection of the human keratinocyte cell line, HaCaT. Additionally, we aimed to study SP-A's ability to agglutinate HPV-PsVs and to assess potential consequences of this SP-A coating on immune cell recognition and elicited immune responses in human-derived immune cells. Our study demonstrated SP-A's ability to agglutinate and opsonise multiple oncogenic HPV PsVs types, which was accompanied by their enhanced uptake and clearance by RAW264.7 murine macrophages, THP-1 monocytes, and THP-1-derived immature dendritic cells (DC0). Importantly, SP-A-opsonised HPV-PsVs resulted in decreased viral uptake and infection of HaCaT keratinocytes. These results were supported by increased lysosomal accumulation of SP-A-opsonised HPV16-PsVs as observed for both RAW264.7 and HaCaT cells. Co-culturing selected immune cells with HaCaT keratinocytes further reduced HPV-PsV infection in the presence of SP-A which might be explained by SP-A's behaviour in driving a proinflammatory immune response in THP-1 and DC0, in the presence of HPV16-PsVs, as identified by cytokine profiling. These results unveiled SP-A's versatility and substantial influence on various HPV interactions with immune cells and keratinocytes and laid the foundation for future research into the development of alternative prophylactic interventions. Increasing innate immune recognition by exogenous supplementation with SP-A (or SP-A derivatives) holds promise for broader protection against diverse HPV types and potentially other sexually transmitted infections