1. Academic Wits Research Publications (Faculties submissions)
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Item Stress begets stress: the association of adverse childhood experiences with psychological distress in the presence of adult life stress(BioMed Central, 2018) Manyema, Mercy; Norris, Shane A.; Richter, Linda M.Background: Adverse childhood experiences (ACES) have been linked to poor health and well-being outcomes, including poor mental health such as psychological distress. Both ACEs and psychological distress pose a significant public health burden, particularly in low to middle income countries. Contemporaneous stress events in adulthood may also impact psychological distress. The aims of this study were to describe the prevalence of ACEs and psychological distress and to assess the separate and cumulative effect of ACEs on psychological distress, while accounting for the effect of adult stress. Methods: In this cross-sectional study, we used retrospectively measured ACEs from a sample of 1223 young adults aged between 22 and 23 years (52% female) from the Birth to Twenty Plus Study. Psychological distress and adult life stress were measured with a six-month recall period. Hierarchical logistic regression was employed to assess the associations between the exposures and outcome. Results: Nearly 90% of the sample reported at least one ACE and 28% reported psychological distress. The median number of ACEs reported was three (range 0–11). After accounting for demographic and socio-economic factors, all ACEs were individually associated with psychological distress except for parental divorce and unemployment. The individual ACEs increased the odds of PD by between 1.42 and 2.79 times. Compared to participants experiencing no ACEs, those experiencing one to five ACEs were three times more likely to report psychological distress (AOR 3.2 95% CI: 1.83–5.63), while participants who experienced six or more ACEs had nearly eight times greater odds of reporting psychological distress (AOR 7.98 95% CI: 4.28–14.91). Interaction analysis showed that in the absence of adult life stress, the effect of low ACEs compared to high ACEs on PD was not significantly different. Discussion and conclusion: The prevalence of ACEs in this young adult population is high, similar to other studies in young adult populations. A significant direct association exists between ACEs and psychological distress. Adult life stress seems to be a mediator of this relationship. Interventions targeted at psychological distress should address both early life adversity and contemporary stress.Item Describing objectively measured physical activity levels, patterns, and correlates in a cross sectional sample of infants and toddlers from South Africa(BioMed Central, 2017-12) Prioreschi, Alessandra; Micklesfield, Lisa K.; Brage, Soren; Hesketh, Kylie D.; Hnatiuk, Jill; Westgate, KateBackground: Physical activity is considered to have health benefits across the lifespan but levels, patterns, and correlates have not been well described in infants and toddlers under the age of two years. Methods: This study aimed to describe objectively and subjectively measured physical activity in a group of South African infants aged 3- to 24-months (n = 140), and to investigate individual and maternal correlates of physical activity in this sample. Infants’ physical activity was measured using an Axivity AX3 wrist-worn accelerometer for one week and the mean vector magnitude was calculated. In addition, mothers reported the average amount of time their infant spent in various types of activities (including in front of the TV), their beliefs about infants’ physical activity, access to equipment in the home environment, and ages of motor development milestone attainment. Analysis of variance (ANOVA) and pair-wise correlations were used to test age and sex differences and associations with potential correlates. Results: There were significant age and sex effects on the distribution of time spent at different physical activity intensities (Wilks’ lambda = 0.06, p < 0.01). In all cases, the trend was for boys to spend more time in higher intensity physical activity and less time in lower intensity activity than girls; and for time spent in higher intensity activities to be higher in older children. Time spent outside was higher in boys, and this reached significance at 18-months (F =3.84, p =0.02). Less concern around floor play was associated with higher physical activity at 12-months in females only (p = 0.03, r = 0.54), and no other maternal beliefs were correlated with physical activity. The majority (94%) of children were exceeding TV time recommendations. When controlling for age and sex, overall TV time was positively associated with BMI z-score (β=0.01, p = 0.05). Conclusion: This study is the first to show sex and age differences in the patterns of physical activity, and to report on objectively measured and maternal reported physical activity and sedentary behaviour in the first two years of life in South Africa infants. Infants and toddlers should be provided with as many opportunities to be active through play as possible, and TV time should be limited.Item Modelling spontaneous combustion liability of carbonaceous materials(Springer Open, 2018-06) Onifade, M.; Genc, B.This paper presents predictive models to determine spontaneous combustion liability of carbonaceous materials (coals and coal-shales) using statistical analysis. The intrinsic properties and spontaneous combustion liability index were determined by testing 14 coals and 14 coal-shales from Witbank coalfields, South Africa. The relationship between these intrinsic properties (obtained from proximate, ultimate and petrographic analysis) and spontaneous combustion liability indices (the Wits-Ehac Index and Wits-CT Index) were established. The influence of the intrinsic properties of coal-shales in relation to coal properties affecting spontaneous combustion has been established using a statistical method. The linear regression analysis indicates better linear relationships between some of the selected intrinsic properties and spontaneous combustion liability index and thus, identifies the major intrinsic factors affecting their liability toward spontaneous combustion. It was found that a definite positive or negative correlation coefficient exists between the intrinsic factors and spontaneous combustion liability. A set of models to predict the spontaneous combustion liability was derived. The best significant correlation along with the most appropriate model as indicated by R-squared values, the coefficient of correlations and standard error was used to predict the incident of spontaneous combustion.Item Frontline health workers and exclusive breastfeeding guidelines in an HIV endemic South African community: a qualitative exploration of policy translation(BioMed Central, 2018-06) Nieuwoudt, Sara; Manderson, LenoreBackground: Mothers rely heavily on health worker advice to make infant feeding decisions. Confusing or misleading advice can lead to suboptimal feeding practices. From 2001, HIV positive mothers in South Africa were counseled to choose either exclusive breastfeeding or exclusive formula feeding to minimize vertical HIV transmission. On the basis of revised World Health Organization guidelines, the government amended this policy in 2011, by promoting exclusive breastfeeding and discontinuing the provision of free formula. We explored how health workers experienced this new policy in an HIV endemic community in 2015–16, with attention to their knowledge of the policy, counselling practices, and observations of any changes. Methods: We interviewed eleven health workers, from four community health clinics, who had counseled mothers before and after the policy change. The transcribed interviews were analyzed thematically, using a hybrid coding approach. Results: The scientific rationale of the policy was not explained to most health workers, who mostly thought that the discontinuation of the formula program was cost-related. The content of their counseling reflected knowledge about promoting breastfeeding for all women, and accordingly they mentioned the nutritional and developmental benefits of breastfeeding. The importance of exclusive breastfeeding for all infants was not emphasized, instead counseling focused on HIV prevention, even for uninfected mothers. The health workers noted an increased incidence of breastfeeding, but some worried that to avoid HIV disclosure, HIV positive mothers were mixed feeding rather than exclusively breastfeeding. Conclusions: Causal links between the policy, counseling content and feeding practices were unclear. Some participants believed that breastfeeding practices were driven by finance or family pressures rather than the health information they provided. Health workers generally lacked training on the policy’s evidence base, particularly the health benefits of exclusive breastfeeding for non-exposed infants. They wanted clarity on their counseling role, based on individual risk or to promote exclusive breastfeeding as a single option. If the latter, they needed training on how to assist mothers with community-based barriers. Infant feeding messages from health workers are likely to remain confusing until their uncertainties are addressed. Their insights should inform future guideline development as key actors.Item UNICEF’s contribution to the adoption and implementation of option B+ for preventing mother-to-child transmission of HIV: a policy analysis(BioMed Central, 2018-06) Chersich, M. F.; Newbatt, E.; Ng’oma, K.; de Zoysa, L.Background: Between 2011 and 2013, global and national guidelines for preventing mother-to-child transmission (PMTCT) of HIV shifted to recommend Option B+, the provision of lifelong antiretroviral treatment for all HIV-infected pregnant women. Methods: We aimed to analyse how Option B+ reached the policy agenda, and unpack the processes, actors and politics that explain its adoption, with a focus on examining UNICEF’s contribution to these events. Analysis drew on published articles and other documentation, 30 key informants interviews with staff at UNICEF, partner organisations and government officials, and country case studies. Cameroon, India, South Africa and Zimbabwe were each visited for 5–8 days. Interview transcripts were analysed using Dedoose software, reviewed several times and then coded thematically. Results: A national policy initiative in Malawi in 2011, in which the country adopted Option B+, rather than existing WHO recommended regimens, irrevocably placed the policy on the global agenda. UNICEF and other organisations recognised the policy’s potential impact and strategically crafted arguments to support it, framing these around operational considerations, cost-effectiveness and values. As ‘policy entrepreneurs’, these organisations vigorously promoted the policy through a variety of channels and means, overcoming concerted opposition. WHO, on the basis of scanty evidence, released a series of documents towards the policy’s endorsement, paving the way for its widespread adoption. National-level policy transformation was rapid and definitive, distinct from previous incremental policy processes. Many organisations, including UNICEF, facilitated these changes in country, acting individually, or in concert. Conclusions: The adoption of the Option B+ policy marked a departure from established processes for PMTCT policy formulation which had been led by WHO with the support of technical experts, and in which recommendations were developed following shifts in evidence. Rather, changes were spurred by a country-level initiative, and a set of strategically framed arguments that resonated with funders and country-level actors. This bottom-up approach, supported by normative agencies, was transformative. For UNICEF, alignment between the organisation’s country focus and the policy’s underpinning values, enabled it to work with partners and accelerate widespread policy change.Item Knock-down of LRP/LR promotes apoptosis in early and late stage colorectal carcinoma cells via caspase activation(BioMed Central, 2018-05) Vania, Leila; Rebelo, Thalia M.; Ferreira, Eloise; Weiss, Stefan F. T.Background: Cancer remains one of the leading causes of death around the world, where incidence and mortality rates are at a constant increase. Tumourigenic cells are characteristically seen to over-express the 37 kDa/67 kDa laminin receptor (LRP/LR) compared to their normal cell counterparts. This receptor has numerous roles in tumourigenesis including metastasis, angiogenic enhancement, telomerase activation, cell viability and apoptotic evasion. This study aimed to expose the role of LRP/LR on the cellular viability of early (SW-480) and late (DLD-1) stage colorectal cancer cells. Methods: siRNA were used to down-regulate the expression of LRP/LR in SW-480 and DLD-1 cells which was assessed using western blotting. Subsequently, cell survival was evaluated using the MTT cell survival assay and confocal microscopy. Thereafter, Annexin V-FITC/PI staining and caspase activity assays were used to investigate the mechanism underlying the cell death observed upon LRP/LR knockdown. The data was analysed using Student’s ttest with a confidence interval of 95%, with p-values of less than 0.05 seen as significant. Results: Here we reveal that siRNA-mediated knock-down of LRP led to notable decreases in cell viability through increased levels of apoptosis, apparent by compromised membrane integrity and significantly high caspase-3 activity. Down-regulated LRP resulted in a significant increase in caspase-8 and -9 activity in both cell lines. Conclusions: These findings show that the receptor is critically implicated in apoptosis and that LRP/LR downregulation induces apoptosis in early and late stage colorectal cancer cells through both apoptotic pathways. Thus, this study suggests that siRNA-mediated knock-down of LRP could be a possible therapeutic strategy for the treatment of early and late stage colorectal carcinoma.Item Kondo effect and enhanced magnetic properties in gadolinium functionalized carbon nanotube supramolecular complex(Nature Research, 2018-05) Ncube, S.; Coleman, C.; Strydom, A.; Flahaut, E.; de Sousa, A.We report on the enhancement of magnetic properties of multiwalled carbon nanotubes (MWNTs) functionalized with a gadolinium based supramolecular complex. By employing a newly developed synthesis technique, we find that the functionalization method of the nanocomposite enhances the strength of magnetic interaction, leading to a large effective moment of 15.79µB and nonsuperparamagnetic behavior, unlike what has been previously reported. Saturating resistance at low temperatures is ftted with the numerical renormalization group formula, verifying the Kondo effect for magnetic impurities on a metallic electron system. Magnetoresistance shows devices fabricated from aligned gadolinium functionalized MWNTs (Gd-Fctn-MWNTs) exhibit spin-valve switching behaviour of up to 8%. This study highlights the possibility of enhancing magnetic interactions in carbon systems through chemical modification, moreover, we demonstrate the rich physics that might be useful for developing spin based quantum computing elements based on one-dimensional (1D) channels.Item Compositions with a fixed number of inversions(Springer, 2018-05) Knopfmacher, A.; Mays, M. E.; Wagner, S.A composition of the positive integer n is a representation of n as an ordered sum of positive integers n = a1 + a2 + ··· + am. There are 2n−1 unrestricted compositions of n, which can be sorted according to the number of inversions they contain. (An inversion in a composition is a pair of summands {ai, aj} for which i aj .) The number of inversions of a composition is an indication of how far the composition is from a partition of n, which by convention uses a sequence of nondecreasing summands and thus has no inversions. We count compositions of n with exactly r inversions in several ways to derive generating function identities, and also consider asymptotic results.Item Optimizing Structures with Semi‑Rigid Connections Using the Principle of Virtual Work(Springer, 2018-04) Elvin, Alex; Strydom, JohnnieIn this paper, the virtual work optimization method (VWOM) has been generalised to consider structures with semi-rigid connections. The VWOM is an automated method that minimizes the mass of a structure with a given geometry, multiple deflection criteria, and load cases while adhering to design code requirements. In the optimization process, members are selected from a discrete database to meet all strength and stiffness criteria. Connections are modelled using rotational springs, allowing some moment transfer. The rotational stiffness of each connection can be varied from rigid to pinned. The example of a pitched roof frame is used to explain the method. Two case studies are considered: (i) (i) a three-storey two-bay and (ii) a four-storey three-bay office building. The VWOM produced results up to 26.7% lighter than results in the literature. Furthermore, the structures were optimized for a range of rotational stifness, where all connections in the structure were assumed to have the same rotational stiffness. Characteristic jumps in the optimized mass versus rotational stiffness were observed.Item Influence of socioeconomic status on changes in body size and physical activity in ageing black South African women(BioMed Central, 2018-04) Gradidge, Philippe Jean-Luc; Norris, Shane A.; Munthali, Richard; Crowther, Nigel J.Background: The increasing prevalence of obesity in sub-Saharan African women is not well understood, and black South African women in the region are particularly vulnerable. This study aimed to examine whether the relationship of socioeconomic status (SES) with changes in body mass index (BMI) and waist circumference (WC) is mediated by physical activity in ageing African women. Methods: In a longitudinal analysis of the 518 caregivers associated with the Birth to Twenty Plus study, the role of SES associated with 10-year changes in BMI and WC was tested using structural equation modelling (SEM). The degree of mediation of moderate-vigorous physical activity (MVPA) and sitting time in this association was also assessed. Results: The prevalence of obesity increased significantly from baseline to follow-up (p < 0.0001). In the SEM models, baseline SES had a direct positive effect on changes in BMI (β, 95% CI, 0.02 (0.005 to 0.04), and a direct negative effect on changes in MVPA (β, 95% CI, − 3.81 (− 6.92 to − 0.70). Baseline MVPA had a direct negative effect (β, 95% CI, − 0.002 (− 0.003 to − 0.0003) and indirect positive effect via change in MVPA (β, 95% CI, 0.01 (0.0001 to 0.001) on change in WC. Conclusions: Our study demonstrates the role and interaction of sociodemographic and behavioural predictors of obesity and suggests a multifaceted approach to management of the crisis in communities of ageing urban African women.