Towards a material damage model using the logarithmic strain, with von Mises plasticity considerations

Damage is briefly defined as the presence and growth of micro-defects in a material. This study serves to describe the computational implementation of the material damage theory adopted for ductile materials. Thus, pays attention to the computational analysis of the physical behaviour of materials under finite deformations — in particular, the stress-strain behaviour, load-deformation behaviour and location of weak zones. Throughout this study, non-linear continuum mechanics is utilised as the mathematical basis of the constitutive and general finite element framework. In continuum mechanics, there exists no requirement to discretely characterise each microcrack that grows in a material, thus making it possible to provide analysis of the stress and strain response affected by micro-defects using material particles, which are localised collections of many atomic-scale particles. The continuum is thus a sum of its material particles. To complement this description of mechanics, constitutive and phenomenological equations are adopted from the non-linear thermodynamic phenomena of elasticity, plasticity, and damage; the laws of thermodynamics will therefore apply and are shown as such. The proposed material damage model is developed and implemented in the backend of the in-house computational mechanics toolbox SESKA, which uses finite element-based discretisation and approximation techniques. Field and scalar quantities, such as stress and strain, are computed with the use of the return-mapping method. The stress measures utilised are the 2nd Piola-Kirchhoff stress S and the Mandel stress Σ. The Newton-Raphson update scheme is applied in the plasticity evolution equations via the plastic multiplier (denoted λ), which innately controls the evolution of all other inelastic phenomena. Damage is a function of plastic evolution and thus plays a role in the plasticity multiplier calculation. Moreover, this proposed model makes the assumption of full isotropy, all material properties at a material point are the same in tension and compression and the same regardless of the dimension. Finally, several examples are utilised to showcase the model and all the intricacies are presented — the problem setup, boundary condition assignment and multi-layered analysis are detailed in the content of this study and the examples perform well under qualitative scrutiny. These examples include a cantilevered beam model, a simply supported bending model and a plane strain example to evaluate whether the material model achieves qualifiable correlation to expected behaviour and to assess whether the damage-related parameters affect the stress and strain behaviour as expected. In brief conclusion, this paper shows that the model achieves qualifiable correlation and all the material parameters function as expected

Evaluation of adherence to an evidence-based bundle of care for the treatment of staphylococcus aureus bacteraemia at Groote Schuur Hospital

Background Staphylococcus aureus bacteraemia (SAB) is associated with high hospital mortality. Improvements in outcome have been described with standardised bundles of care. Objectives To study adherence to a standardised bundle of care (BOC) recommendations using a consultation proforma, for all patients admitted with SAB to Groote Schuur hospital over a year. To describe in-hospital and 90-day mortality in these patients Methods A retrospective audit of all unsolicited infectious disease consultations for patients with SAB admitted to Groote Schuur hospital during 2018. Adherence to recommendations of a standard care bundle were audited. Results Eighty six patients were included; 61 (71%) with healthcare-associated infection and 25 (29%) with community associated infection. Over 80% of adherence to treatment recommendations was achieved regarding antibiotic (including vancomycin) usage, source control and use of echocardiography as required. In-hospital mortality was 16% while overall 90-day mortality was 18%, with only age an independent predictor of mortality. No association with adherence to the recommendations and outcome was seen. Conclusion Adherence to a simple BOC is good, when using standardised a proforma as a communication tool. SAB mortality may be reduced by such an approach

The requirements and consequences of sections 17 (5) and 23 (5) of the Matrimonial Property Act 88 of 1984: a comparative scrutiny for the South African legal system

This thesis is a comparative scrutiny of sections 17 (5) and 23 (5) of the Matrimonial Property Act 88 of 1984. The comparison centres on the legal situation in South Africa, Germany and Switzerland. References, however, will also be made to other countries such as England, Scotland, France, Belgium, Spain, Sweden, Austria and Poland. Sections 17 (5) and 23 (5) of the Matrimonial Property Act 88 of 1984 provide that for legal transactions in respect of household necessaries both spouses are, respectively, jointly and severally liable [section 23 (5)] or may be sued jointly and severally [section 17 (5)]. As regards the question of liability for the debts arising from transactions in respect of household necessaries, the statutory provisions are relatively clear. However these statutory provisions give rise to many important questions other than the issue of liability such as the historical background, the ratio legis and the legal nature of sections 17 (5) and 23 (5) of the Matrimonial Property Act 88 of 1984, the requirements and the effects of sections 17 (5) and 23 (5) in respect of the contractual position of the spouses and the acquisition of ownership. Furthermore the question arises as to how the effects of sections 17 (5) and 23 (5) of the Matrimonial Property Act 88 of 1984 can be excluded. Unfortunately it would appear that the South African authorities have not yet grappled with many of these questions, in spite of the importance thereof. The author therefore attempts to submit his own answers. Furthermore the legal situation in Germany and Switzerland is presented. No attempt is made to answer questions which arise in these countries, since the primary object of the present thesis is the legal situation in South Africa. The author thus merely describes the legal situation in Germany and Switzerland and concentrates on the majority opinion in these countries. Only where, from the South African point of view it appears to be necessary, a short criticism is submitted. Finally the author compares the different legal systems, highlights weaknesses of the South African law and the advantages of the Swiss and German law in order to submit a proposal which could improve the current legal situation in South Africa

Environmental health recommendations for Multidrug-Resistant Tuberculosis in low- and middle-income countries: a systematic review

Despite efforts towards the management and prevention of Tuberculosis (TB) having shown some success, Multidrug-Resistant Tuberculosis (MDR-TB) may potentially compromise these endeavours. MDR-TB has the potential to become the most dominant form of TB in low- and middle-income countries (LMICs). The impact of environmental health factors on the optimization of health of MDR-TB infected individuals, as well as on the prevention of transmission to household contacts, is not well documented. Current Sustainable Development Goals (SDGs) aim to achieve inclusivity, sustainability and resilience, not only through economic and social changes, but also through environmental targets in order to achieve optimal health and well-being for all. However, without appropriate acknowledgment of the environment's influence on outcomes during TB treatment, these targets are potentially unattainable. Establishing the recommendations of environmental health risk factors for individuals living at home with MDR-TB will have important policy implications as well as assist in decision making for those affected with MDR-TB in LMICs, such as South Africa. This systematic review, therefore, sought to identify the environmental health factors in LMICs that affect treatment outcomes for individuals living at home with MDR-TB, to optimize their health during completion of their treatment regimen and prevent transmission to household contacts. Part A outlines the current literature available for such a topic as well as methodology used within the systematic search and analysis of included articles. Prominent environmental health exposure variables of interest that have previously been identified as having a significant role in TB transmission or influencing the well-being of infected individuals, were identified within the literature. These included air pollution, nutrition, migration, urbanization, smoking, alcohol, other substance use and housing. Outcomes of interest included optimization of health and prevention of MDR-TB transmission to household contacts. The article (part B) represents the results from the systematic search as well as the application to current policy recommendations. After screening and reviewing the full text of potential articles for inclusion (N = 87), only thirteen articles were eligible for inclusion into the final sample. All included studies were primary observational studies, examining the relationship between MDRTB and the pre-defined exposures and outcomes in populations ≥13 years of age. Environmental risk factors for household transmission of MDR-TB potentially included malnutrition but showed no significant relationship with overcrowding. There was disagreement as to whether smoking was as a significant predictor of mortality but findings did indicate that smoking did have a negative impact on sputum culture conversion among patients receiving treatment. Other substance use was found to have a significant role in the default of treatment. The use of alcohol was associated with poor treatment outcomes, default of treatment and lack of sputum culture conversion. In terms of household conditions, an association was found between substandard housing conditions and treatment default. Formal housing was associated with a decline in treatment default but a residential address change was associated with defaulting treatment. The results of the review presented contradictory results regarding the risk of mortality and underweight/overweight BMI estimates. The review potentially highlighted vulnerable population groups including gender groups, children and HIV positive individuals. Therefore, this systematic review highlighted the potential relationship between environmental risk factors and optimising the health of individuals on treatment for MDR-TB, as well as the role that promoting environmental health may play in preventing the transmission to household contacts. In conclusion, environmental risk factors should be incorporated into local health system strategies and global policy. This includes WHO targets in TB prevention efforts, as well as in action areas for the attainment of relevant SDGs (e.g. SDG 3 and SDG 5), to address the burden of MDR-TB and decrease MDR-TB transmission in LMICs, effectively and sustainably

“To be or not to be?”: The decriminalisation of sex work in South Africa

President Cyril Ramaphosa in his speech at the launch of the Gender-Based Violence (GBV) and Femicide Declaration in 2019, made the commitment to working towards decriminalising sex work in South Africa as a means to also fight GBV. This in-line with what organisations that advocate for sex work such as the Sex Workers Education and Advocacy Taskforce (SWEAT) and Sonke Gender Justice have been fighting for. The plight of sex workers and the urgent requirement for sex work legislative reforms has been highlighted by the documented increase or the spotlight on GBV. Sex work is predominantly a profession taken up by women and thus the effects of its criminalisation are mostly experienced by women. Therefore, there is a close link between the struggles of sex workers the struggle against GBV. The thesis explores the reasons why advocacy groups such as SWEAT support decriminalisation as opposed to legalisation and partial decriminalisation. Drawing an understanding as to why other sex work modules do not appeal to the needs of sex workers and why they are viewed to lead back to the infringement on basic human rights. Furthermore, it looks at the impact of using the GBV platforms to address the decriminalisation of sex work in South Africa

Simulating the Dynamics and Influences of the West African Westerly Jet

The West African westerly jet (WAWJ) is a key rainfall producing system over West Africa. While past studies have examined the dynamics of the WAWJ and its influences on Sahelian rainfall, there is no information on how well the jet is simulated by contemporary climate models. This thesis examines the capability of the Coupled Model Intercomparison Project version 6 models (CMIP6) and the Atmospheric component of Model Prediction Across Scale (MPAS) in simulating the WAWJ, its moisture transport over West Africa, and its influence on Sahelian precipitation. Three types of climate dataset (observation, reanalysis, and simulations) were analysed in the thesis. The observation dataset (from the Climate Research Unit or ‘CRU') and the reanalysis dataset (from the European Centre for Medium-Range Weather Forecast Atmospheric Reanalysis, or ‘ERA5') were used to evaluate 26 CMIP6 models (for 35 years: 1980–2014) and MPAS (for 30 years: 1985–2014). To investigate the sensitivity of the simulated WAWJ to model resolution, two additional simulations were performed with MPAS, focusing on WAWJ strong years (1989, 1994, and 1999) and weak years (1986, 1990, and 2000). This thesis defined the WAWJ as a low-level westerly jet (with average maximum speed of 5 m s-1 ) at 925 hPa over the eastern Atlantic Ocean and over the West African coast and used standard statistical metrics to quantify the capability of the models in simulating the characteristics and influences of the WAWJ. The majority of the CMIP6 models capture the temporal and spatial structures of the WAWJ and agree with ERA5 that the jet attains its maximum speed in August. However, most simulated jets form earlier and are stronger than the observed jet. While most of the CMIP6 models capture the link between the jet and temperature distribution over West Africa, they struggle to reproduce the relationship between the jet and precipitation distribution over the sub-continent, especially over the Sahel. Most models failed to replicate the increase in the moisture transport (i.e., the eastward and north-eastward transports) associated with a stronger WAWJ, as in ERA5. Some models capture the increased moisture transport but do not translate it to increased precipitation over the Sahel. MPAS performs well in simulating various features in temperature, precipitation, and wind fields over West Africa, but with wet and warm biases over the region. It also simulates the WAWJ but the simulated jet forms too early and is too strong. In addition, the position and dynamics of the simulated jet differ from the observed jet because the model fails to capture the local pressure gradient force that induces the WAWJ over the Atlantic Ocean. The model underestimates the relationship between the WAWJ and Sahelian precipitation because it limits WAWJ moisture transports to the southern part of Sahel, in contrast to the observation. The sensitivity simulations show that increasing the horizontal resolution of the model does not improve the MPAS simulation of the WAWJ or the WAWJ moisture transport to the Sahel. The results of the study have application in improving the climate models for seasonal predictions and future projections over West Africa, especially over the Sahel

Negative Mood Reduces Self-Referential Memory Effects in an Online Object Ownership Simulation

The Self-Reference Effect (SRE) is a cognitive bias in which self-relevant stimuli are prioritised for processing. This bias allocates more attentional and encoding resources to selfrelevant objects making their memory traces more robust and easily retrievable. Research has repeatedly shown that self-owned and self-proximal objects benefit from this bias. However, little is known about the factors that impact the SRE. Emerging research suggests that emotion may attenuate the SRE. For instance, studies show that the salience of a self-related stimulus reduces when the stimulus is associated with negative self-referential information. However, there is limited research on how the SRE may be modulated by transient mood states. The major aim of the present study is to determine whether the SRE may be modulated by transient mood states. We investigated whether an induced negative mood state alters memory for self-related objects using an online emotion induction and shopping task. This task was selected because although SRE effects are robust in laboratory conditions, most studies rely on tasks with low external validity. All participants completed an online mood induction protocol (either negative or neutral mood induction). Thereafter, participants completed an online self-referencing object ownership task involving encoding (and subsequent recall) of self-owned, familiar other-owned, or unfamiliar other-owned everyday household shopping items. The group induced into a negative mood showed reduced memory recognition accuracy compared to the neutral mood group, with reduced memory for selfowned items. Further analyses revealed that negative mood interacted with both depression scores and object ownership to influence self-referential processing. Our results add to current SRE evidence and offer insights into how this bias can be influenced by both transient mood states and affective symptoms. Keywords: Self-reference, Object Ownership, Mood, Negative Emotion, Online

Neoadjuvant endocrine therapy for estrogen receptor positive breast cancer in an African setting

Background Several studies have reported response rates for ER positive cancers on neoadjuvant endocrine therapy (NET), with lower toxicity compared to neoadjuvant chemotherapy (NCT). During the first wave of the COVID pandemic, clinician preference for NET increased significantly, buying time for hospital recovery before proceeding to surgery. To date, no studies have yet explicitly reported on the use of NET in an African context. Methods This study was a retrospective review, looking at breast cancer patients who received NET between 01 March 2019 to 31 December 2020 at Groote Schuur Hospital. Patients were included if they were female, older than 18 years, ER positive, and had a biopsy-proven breast cancer less than 50mm in size on clinical exam. Results There were 16 patients included in the study, of which all were female. The mean age was 59 years (range 41-75). When comparing the histological measurement to initial size on imaging, 7 patients had an excellent response to NET with tumours that decreased in size, whereas 9 patients had tumours that increased in size despite NET. There was no statistically significant difference between the two groups in terms of patient and pre-treatment tumour characteristics, pathological results, endocrine therapy, surgical therapy, or adjuvant oncological therapy. For the 9 patients who had progression on NET, the post resection median tumour size was more than double the pre-NET tumour size, as determined on imaging. Conclusion Until further studies can be performed in this setting, NET should be used with caution in situations where there will be a significant delay to surgery

Localization Techniques for Non-Palpable Breast Lesions: Current Status, Knowledge Gaps, and Rationale for the MELODY Study (EUBREAST-4/iBRA-NET, NCT 05559411)

Background: Surgical excision of a non-palpable breast lesion requires a localization step. Among available techniques, wire-guided localization (WGL) is most commonly used. Other techniques (radioactive, magnetic, radar or radiofrequency-based, and intraoperative ultrasound) have been developed in the last two decades with the aim of improving outcomes and logistics. Methods: We performed a systematic review on localization techniques for non-palpable breast cancer. Results: For most techniques, oncological outcomes such as lesion identification and clear margin rate seem either comparable with or better than for WGL, but evidence is limited to small cohort studies for some of the devices. Intraoperative ultrasound is associated with significantly higher negative margin rates in meta-analyses of randomized clinical trials (RCTs). Radioactive techniques were studied in several RCTs and are non-inferior to WGL. Smaller studies show higher patient preference towards wire-free localization, but little is known about surgeons’ and radiologists’ attitudes towards these techniques. Conclusions: Large studies with an additional focus on patient, surgeon, and radiologist preference are necessary. This review aims to present the rationale for the MELODY (NCT05559411) study and to enable standardization of outcome measures for future studies