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Additive manufacturing is an emerging and continually growing field of research with great potential in the development of new technologies through which to change the world as we know it. This thesis offers a look from a 3D printing perspective towards the diverse fields of artificial muscle fabrication, bioprinting, polymer chemistry which can effect shape change or other responses under stimuli, as well an in detail investigation into steerable needle robotics and its potential as a mechanism for additive manufacturing. Since the 3D printing of (bio)polymers is generally reserved for the fabrication of structures on beds which are far away from where their intended use is intended, this thesis proposes an approach to 3D printing exactly the polymer that is of interest in the location in which it is intended. This thesis presents the research and development of a flexible steerable needle robot for the application of 3D printing (bio)polymers which could take the form of artificial muscles, bone, nerves, etc. in vivo. This is extremely challenging, however, and the research undertaken is intended towards building the capability to one day in future achieving this goal. Several experiments are presented which explore the characteristics of a custom developed steerable needle robot in application for 3D printing which include: its mechanisms, its control systems, its algorithms to accurately reach a target goal within a presented body, as well as it visualization system. Furthermore, this developed robot is then utilized to ”3D print” a (bio)polymer inside of a prepared phantom body (e.g., gelatine) to fabricate a bio-fiber. While the bio-fibers presented by this thesis are simple and do not react under any stimulus to act as an artificial muscle, there is a further future opportunity identified which could utilize advanced polymer chemistry to in fact achieve this end result. This thesis contributes towards the synthesis of multiple fields of research towards the g

Additive Manufacturing (AM) technologies have the potential to create complex geometric parts that can be used in high-end product industries, aerospace, automotive, medical etc. However, the surface finish, part-to-part reliability, and machine-to-machine reliability has made it difficult to qualify the process for load dependent structures. The improvement of surface finish on metal printed parts, is a widely sought solution by these high-end industries and non-destructively characterizing the mechanical aptitude of metal printed parts, would pave the way for quality assessment strategies used to certify additively manufactured parts. This thesis examines the capability of laser polishing and non-destructive testing technologies and methods to address these difficulties. This research study presents an investigation into quality management strategies for Direct Metal Printing (DMP) with powdered Stainless Steel 17-4 PH. The research aim is split into two key categories: to improve the surface finish of metal additive manufactured parts and to non-destructively characterize the impact of defects (metallurgical anomalies) on the mechanical properties of the printed part. To improve surface finish of a printed part, a novel methodology was tested to laser polish the Laser-Powder Bed Fusion (L-PBF) parts during print with the built-in laser. Numerous technologies for non-destructive testing techniques already exist, and in the duration of this doctoral study various technologies were explored. However, the final solution focuses on layer-wise capture with a versatile low-cost imaging system, retrofitted within the DMP machine, to capture each layer following the lasering process. In addition, the study also focuses on progressing the characterization of data (images), using a combination of image processing, 3D modelling and Finite-Element-Analysis to create a novel strategy for replicating the as-built specimen as a computer-aided design model and performing simulate

The primary aim of this study was to explore gender differences regarding the sport psychological skills (SPS) profile of adolescent sport participants in a South African context. The present study forms part of an extensive five-year longitudinal study, the Physical Activity and Health Longitudinal Study (PAHL-Study). A crosssectional research design was used to gather quantitative data. Two hundred and eleven (89 boys and 122 girls) grade nine pupils (14 and 15 years of age) participated in the study. The participants completed the Athletic Coping Skills Inventory for Sport (ACSI-28) to determine their SPS profile. The results showed that the boys obtained higher mean scores in seven of the eight measured sport psychological skills. Freedom from worry was the only skill that yielded a statistically significant difference, with the boys (52.06±20.27) obtaining a higher mean value than the girls (46.17±20.56). In conclusion, the current findings indicated that, at this developmental level of competitive sport, boys and girls participants seem to be very similar regarding their sport psychological skills dispositions

Additive manufacturing (AM) techniques have promising applications in daily life due to their superiority over conventional manufacturing techniques in terms of complexity and ease of use. However, current applications of polymer-based 3D printing (3DP) are limited to small scale only due to the high cost of materials, print times, and physical sizes of the available machines. In addition, the applications of 3DP are yet to be explored for insulation of different large-scale mechanical structures. For example, milk vats are large structures with complex assemblies (like pipes, joints, couplings, valves, ladders, vessel doors) that requires insulation to store the milk at a low temperature of 6 °C as per the NZCP1 regulations in New Zealand. Generally, milk vats lack any kind of proper insulation around them and require additional cooling systems to keep the milk at a prescribed temperature. Any variations in the temperature can lead to deterioration in the quality of milk. Therefore, there exists a research gap that can not only help to solve an industrial issue but also can be a first step towards real large-scale 3DP applications that can potentially lead to many others in future. For example, pipe insulation, food storage tanks, chemical storage tanks, water treatment. This research explores new and inexpensive materials for large-scale 3DP. For this purpose, the current state of the 3DP materials is analyzed and based upon this analysis two distinct approaches are devised: 1) in-process approach to improve the mechanical properties of the existing materials like polylactic acid (PLA), and 2) modification of inexpensive materials (like materials used in injection, rotational, and blow moulding) to make them printable. In the first approach, by controlling the process parameters, mechanical properties are studied. While in the second approach, blends of high density polyethylene (HDPE) and polypropylene (PP) with different thermoplastics (acrylonitrile butadiene s

Background: Hypercoagulation is associated with coronary artery disease (CAD). Whether depression symptoms dysregulate inflammatory and hemostatic markers in an African cohort is not known; therefore, we assessed the relationship between depressive symptoms and inflammatory and hemostatic markers as potential CAD risk markers in an African sex cohort. Material and Methods: We included 181 black African urban-dwelling teachers (88 men, 93 women; aged 25-60 years) from the Sympathetic Activity and Ambulatory Blood Pressure in Africans Study. The Patient Health Questionnaire was used to assess depressive symptoms. Fasting plasma concentrations of C-reactive protein, fibrinogen, D-dimer, plasminogen activator inhibitor-1 (PAI-1) and 24-hour blood pressure measures were obtained. Results: Moderately severe depression symptom status was similar in the black sex groups. Both sex groups showed a mean hypertensive state and low-grade inflammation (C-reactive protein > 3 mg/L). Levels of PAI-1 were higher in depressed men, whereas D-dimer levels were lower in depressed women when considering concomitant confounders. In black men only, depressive symptoms were associated with levels of PAI-1 (adj. R2 = 0.12; [beta] = .22 [95% confidence interval, .0-.44]; P = .04) and D-dimer (adj. R2 = 0.12; [beta] = .28 [95% confidence interval, .08-.48]; P = .01), independent of confounders. Conclusion: In black men, depression symptoms accompanied by a mean hypertensive status may up-regulate inflammatory and thrombotic processes. Depression symptoms in black men facilitated hypercoagulation or fibrinolytic dysregulation and potentially increased their CAD risk. Early screening of fibrinolytic markers and for the presence of depressive symptoms is recommended

Objective: Chronic psychosocial stress as experienced in an urban environment plays an important role in the aetiology of depression-related cardiovascular risk. It is uncertain whether acute mental stress responses aggravate this risk. Therefore, we aimed to explore the associations between depressive symptoms, neuroendocrine acute mental stress responses and cardiovascular risk, that is ECG-left ventricular hypertrophy (ECG-LVH), in a black South African cohort. Materials and methods: The substudy sample consisted of 179 black African men and women from the Sympathetic Activity and Ambulatory Blood Pressure in Africans study. Depressive symptoms were evaluated using the nine-item Patient Health Questionnaire and the participants were stratified into black Africans with depressive symptoms and without. Cortisol and 3-methoxy-phenylglycol (MHPG) responses were analysed during rest and exposure to the Stroop mental stressor. Cortisol median split responses were determined and stratified sex groups accordingly into above (>1.5 ng/ml) and below (≤1.5 ng/ml) responders. Blood pressure and ECG-LVH data were obtained from 24-h ambulatory monitoring and 12-lead ECG. Results: The Africans with depressive symptoms demonstrated mean hypertensive status, blunted cortisol and MHPG acute mental stress responses (P≤0.05). In Africans with depressive symptoms and low cortisol stress responses, blunted MHPG acute mental stress responses were associated with ECG-LVH in Africans [adjusted R 2=0.20; β=0.92 (95% confidence interval 0.74, 1.10); P≤0.02]. Conclusion: Blunted neuroendocrine responses were linked to depressive symptoms and ECG-LVH in black Africans. When coupled to their hypertensive status, these vasoconstrictive agent responses may underpin the increased long-term depression and vascular disease risk in urban Africans.

This study explored levels of occupational stress and mental well-being of a cohort of Black South African teachers. 200 secondary school teachers completed the Teacher Stress Inventory (TSI: Boyle, Borg, Falzon, & Baglion, 1995), General Health Questionnaire (GHQ-28: Goldberg & Hillier, 1979) and Mental Health Continuum-Short Form (MHC-SF: Keyes, 2006). Correlations and Structural Equation Modelling (SEM) were used to determine the levels of occupational stress and well-being of participants, and to establish the relation between these variables. A significant majority of the teachers reported high levels of mental health (flourishing) despite high levels of teacher stress. These results show teachers’ ability to withstand and cope with stress whilst maintaining their mental health. This suggests the presence of protective factors that mediate the effect of work-related stressors and, in so doing, contribute to the teachers’ levels of resilience.

Orientation: Recent literature has emphasised the important role that self-regulation plays in the mental health of individuals. The lack of a validated psychometric instrument to accurately measure self-regulation amongst Black South Africans however limits its potential impact within the challenging South African context. Research purpose: The aim of this study was to investigate the psychometric properties of the Short Self-Regulation Questionnaire (SSRQ) when used in a South African context, specifically focusing on Black South Africans. Motivation for the study: By commenting on the ability of the SSRQ to accurately capture the construct of self-regulation amongst Black educators, the current article serves to address and alleviate the lacunae in our understanding of self-regulation as a potentially protective factor. Research design, approach and method: The study was of a quantitative nature, and made use of a cross-sectional design and purposively selected study sample. Participants were urbanised Black teachers (N = 200) who completed the SSRQ and other measures of self-regulation and psychological well-being. Main findings: The reliability of the SSRQ total scale score proved satisfactory. Factor analysis produced five robust sub-constructs that were theoretically interpretable. Significant correlations between the SSRQ and other measures of self-regulation and psychological wellbeing also indicated good criterion-related validity. Practical/managerial implications: The availability of a reliable and valid instrument for the measurement of self-regulation in the South African context will enable both researchers and practitioners to better understand and utilise self-regulation in the enhancement of individual well-being. Contribution/value-add: The SSRQ’s ability to accurately measure self-regulation will contribute to our understanding of its role as preventive strength in the South African context. Refinement of item content will serve to further streng

This study sought to determine the differential influence of self- and collective efficacy beliefs on the psychological well-being of individuals within a community in transition. A cross-sectional survey design was used to collect data from 1050 Setswana speaking participants from urban (n = 451) and rural (n = 599) areas in the North-West Province of South-Africa. The Community Collective Efficacy Scale (CCES) and the Generalized Self-Efficacy Scale (GSE), as well as the Affectometer 2 (AFM) and Satisfaction with Life Scale (SWLS) were administered. Descriptive statistics, as well as correlational and regression analyses were conducted to determine the association between self-efficacy and collective efficacy, and the different measures of psychological well-being. Results indicated that participants from the urban context reported higher levels of both self-efficacy and collective efficacy, as well as higher levels of psychological well-being than their rural counterparts. A strong and significant relationship was found between self-efficacy and collective efficacy, and between efficacy beliefs and psychological well-being. Efficacy beliefs are important factors in the prediction of psychological well-being. Raising either self-efficacy or collective efficacy should lead to higher psychological well-being and better adjustment during the process or urbanisation.

Depressive symptoms are associated with an increased risk for developing cardiovascular diseases, driven by its link to the metabolic syndrome (MetS). This phenomenon, however, still needs to be investigated in the African population. The aim of this study is to investigate the association between left ventricular hypertrophy (LVH) and MetS risk markers in a determined sample. The researchers stratified Black African men and women into with depressive symptoms (D) or without depressive symptoms (ND) group, based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria score. Fasting MetS, chronic hyperglycemia (HbA1c), ambulatory blood pressure (BP) and Cornell product-LVH (CP-LVH) in ECG measures were obtained. Depressive symptoms were reported in 45.3% of the sample. Independent of depression status, African men and women revealed a pre-diabetic state (glycated hemoglobin >5.7%). CP-LVH was associated with decreased low high-density lipoprotein cholesterol in D African women. In D African men, systolic BP (P = .001) and HbA1c (P = .08) explained 64% and 31% of the variation in LVH, respectively. In conclusion, depressive symptoms in Black African women were associated with a measure of target end organ damage, CP-LVH, and this association was driven by a metabolic factor. In Black African men, independent of depressive symptoms, LVH, was driven by cardiometabolic factors, namely SBP and HbA1c.

Orientation: Recent literature has emphasised the important role that self-regulation plays in the mental health of individuals. The lack of a validated psychometric instrument to accurately measure self-regulation amongst Black South Africans however limits its potential impact within the challenging South African context. Research purpose: The aim of this study was to investigate the psychometric properties of the Short Self-Regulation Questionnaire (SSRQ) when used in a South African context, specifically focusing on Black South Africans. Motivation for the study: By commenting on the ability of the SSRQ to accurately capture the construct of self-regulation amongst Black educators, the current article serves to address and alleviate the lacunae in our understanding of self-regulation as a potentially protective factor. Research design, approach and method: The study was of a quantitative nature, and made use of a cross-sectional design and purposively selected study sample. Participants were urbanised Black teachers (N = 200) who completed the SSRQ and other measures of self-regulation and psychological well-being. Main findings: The reliability of the SSRQ total scale score proved satisfactory. Factor analysis produced five robust sub-constructs that were theoretically interpretable. Significant correlations between the SSRQ and other measures of self-regulation and psychological wellbeing also indicated good criterion-related validity. Practical/managerial implications: The availability of a reliable and valid instrument for the measurement of self-regulation in the South African context will enable both researchers and practitioners to better understand and utilise self-regulation in the enhancement of individual well-being. Contribution/value-add: The SSRQ’s ability to accurately measure self-regulation will contribute to our understanding of its role as preventive strength in the South African context. Refinement of item content will serve to further streng

Dissociation between b-adrenergic behavioral and physiological defensive active coping (AC) responses was associated with cardiometabolic risk in urban but not rural African males. Whether this is partly driven by underlying neuroendo- crine dysfunction is not certain. We aimed to assess the association between coping style, urbanization, and neuroen- docrine function. Blood pressure (BP) and serum stress hormones were assessed across levels of urbanization (rural vs. urban) and coping style (active vs. passive) in 178 Black African men. Urban men demonstrated increased hypertension prevalence, a-adrenergic hemodynamic pattern, lower testosterone levels, and a larger cortisol:testosterone ratio (Cort:Test) compared to their rural counterparts. This was particularly evident in urban AC men where cortisol and Cort:Test explained 36–40% of the variance in BP. Dissociation between behavioral and physiological b-adrenergic neuroendocrine responses in urban AC African men was shown. A stressful urban environment might induce an apparent loss of physiological control, thereby facilitating disturbed neuroendocrine AC responses, which could increase cardiovascular disease risk

Family members as well as informal caregivers are increasingly bearing the responsibility of taking care of persons diagnosed with HIV/AIDS (UNAIDS, 2000:5). The intensity of the caregiving process and the variety of stressors caregivers are exposed to (Uys, 2002:101-102; De Figueiredo & Turato, 2001:637-640; Flaskerud, Carter & Lee, 2000:128), have been well researched and documented. In this study, the salutogenic perspective was used to determine the sense of coherence of a group of eight informal caregivers. This perspective serves as one of the theories within the movement of positive psychology, where the focus is on the origins of psychological well-being. The results of the Sense of Coherence Scale (SOC) and the analysis of semi- structured interviews revealed a number of general resistance resources that have a positive influence on the caregivers� sense of coherence, as well as their psychological well-being. These results may lead to the development of a psycho-educational program which will assist caregivers in maintaining their psychological well-being in spite of the stressors associated with caregiving.