1. Academic Wits Research Outputs/Journal articles
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Item Parenting in place: young children's living arrangement and migrants' sleep health in South Africa(Wiley, 2023-06) Madhavan, Sangeetha; Kim, Seung Wan; White, Michael; Gomez‐Olive, XavierMigration research tends to treat childrearing as a secondary role for migrants. By prioritising the economic objectives of migration, most models present migrants as either delaying childbearing or, if they have young children, not living with them. However, migration has become increasingly feminised, the types of mobility more varied, while the returns to migration remain uncertain at best. At the same time, norms around childrearing are shifting, and the capacity of kin to take care of children may be weakening. In such contexts, migrants may not want to or be able to be separated from their children. Confronting such difficult decisions and their consequences may be reflected in poor sleep health for the migrant parent. We draw on data from the Migration and Health Follow‐Up Study (MHFUS) in South Africa to examine the following questions: (i) To what extent is children's coresidence associated with sleep health for migrant parents? (ii) Do effects vary by sex of migrant? and (iii) Do effects vary by location of migrant? Results from propensity score matching confirm that migrants who coreside with all their young children are more likely to experience healthy sleep compared to those who have nonresident or no young children. However, stratified analysis shows that these effects are only significant for women and those not living in Gauteng province. The value of these findings is underscored by the need for research on the well‐being of migrant parents who are negotiating multiple agendas in economically precarious and physically insecure destinations.Item An inertial-type method for solving image restoration problems(Springer, 2023-07) Izuchukwu, Chinedu; Shehu, Yekini; Reich, SimeonWe first establish weak convergence results regarding an inertial Krasnosel’skiĭ-Mann iterative method for approximating common fixed points of countable families of nonexpansive mappings in real Hilbert spaces with no extra assumptions on the considered countable families of nonexpansive mappings. The method of proof and the imposed conditions on the iterative parameters are different from those already available in the literature. We then present some applications to the Douglas–Rachford splitting method and image restoration problems, and compare the performance of our method with that of other popular inertial Krasnosel’skiĭ-Mann methods which can be found in the literature.Item Introducing a secondary segmentation to construct a radiomics model for pulmonary tuberculosis cavities(Springer, 2023) du Plessis, Tamarisk; Ramkilawon, Gopika; Duncombe Rae, William Ian; Botha, Tanita; Martinson, Neil Alexander; Dixon, Sarah Alice Parry; Kyme, Andre; Sathekge, Mike MichaelPurpose: Accurate segmentation (separating diseased portions of the lung from normal appearing lung) is a challenge in radiomic studies of non-neoplastic diseases, such as pulmonary tuberculosis (PTB). In this study, we developed a segmentation method, applicable to chest X-rays (CXR), that can eliminate the need for precise disease delineation, and that is effective for constructing radiomic models for automatic PTB cavity classification. Methods: This retrospective study used a dataset of 266 posteroanterior CXR of patients diagnosed with laboratory confirmed PTB. The lungs were segmented using a U-net-based in-house automatic segmentation model. A secondary segmentation was developed using a sliding window, superimposed on the primary lung segmentation. Pyradiomics was used for feature extraction from every window which increased the dimensionality of the data, but this allowed us to accurately capture the spread of the features across the lung. Two separate measures (standard-deviation and variance) were used to consolidate the features. Pearson’s correlation analysis (with a 0.8 cut-off value) was then applied for dimensionality reduction followed by the construction of Random Forest radiomic models. Results: Two almost identical radiomic signatures consisting of 10 texture features each (9 were the same plus 1 other feature) were identified using the two separate consolidation measures. Two well performing random forest models were constructed from these signatures. The standard-deviation model (AUC = 0.9444 (95% CI, 0.8762; 0.9814)) performed marginally better than the variance model (AUC = 0.9288 (95% CI, 0.9046; 0.9843)). Conclusion: The introduction of the secondary sliding window segmentation on CXR could eliminate the need for disease delineation in pulmonary radiomic studies, and it could improve the accuracy of CXR reporting currently regaining prominence as a high-volume screening tool as the developed radiomic models correctly classify cavities from normal CXR.Item Female condom color and scent preference in Durban, South Africa(Elsevier, 2023-06) Beksinska, Mags; Smit, Jenni; Mona, Amanda; Maphumulo, Virginia; Mphili, Nonhlanhla; Manzini-Matebula, Nontsikelelo; Chidarikire, ThatoObjectives: To assess preferences for female condom (FC) colors and scents. Study design: Women aged 18–40 years were randomized to one of three FCs (FC2, Cupid1, Cupid2) two of which offered a choice of color and scent (red/strawberry, purple/vanilla, natural/unscented). Women could choose any variety within condom types while participating in an FC contraceptive efficacy study in South Africa. Results: One hundred and thirty-three women were allocated to each FC type. Strawberry was the most popular variety for both FC2 and Cupid1 (60.9%, 78.3% respectively). Some women chose more than one variety but few chose the natural. Conclusions: Data support a clear preference for colored and scented FCs. Implications: These data can inform FC programme managers to predict demand for different varieties of FC and can adjust supply of FCs accordinglyItem The stability of C-peptide and insulin in plasma and serum samples under different storage conditions(De Gruyter, 2023-07) Nkuna, Delhia X.; Khoza, Siyabonga P.; George, Jaya A.; Maphayi, Mpho R.Objectives: C-peptide and insulin are peptide hormones and their stability is affected by a number of pre-analytical factors. The study aimed to investigate the impact of sample type, storage temperature and time delays before centrifugation and analysis on the stability of C-peptide and insulin. Methods: Ten healthy non-diabetic adults in fasting and non-fasting state were enrolled. 40 mL of blood was collected from each participant into SST and dipotassium EDTA tubes. Samples were centrifuged immediately or at timed intervals (8, 12, 48 and 72 h). After baseline measurements on the Roche Cobas e602 analyzer using electrochemiluminescence immunoassays, aliquots were stored at room temperature (RT), 2–8 and −20 °C for 4 h to 30 days. The percentage deviation (PD) from baseline was calculated and a change greater than desirable biological variation total error was considered clinically significant. Results: C-peptide was more stable in separated serum than plasma (PD of −5 vs. −13 %) samples stored at 2–8 °C for 7 days and was most unstable at RT when centrifugation was delayed (PD −46 % in plasma and −74 % in serum after 48 h). Insulin was more stable in plasma than in serum under the different storage conditions with a minimum PD of −1% when stored at −20 °C for 30 days. When samples were kept unspun at RT for 72 h, PD was −23 and −80 % in plasma and serum, respectively. Conclusions: C-peptide was more stable in serum provided the sample was centrifuged immediately and stored in the fridge or freezer while insulin was found to be more stable in EDTA plasma.Item Numerical simulation of nanofluid flow due to a stretchable rotating disk(Elsevier, 2023-05) Ayano, Mekonnen S.; Otegbeye, Olumuyiwa; Mathunjwa, Jochonia S.In this study, a steady magnetohydrodynamic (MHD) flow due to stretchable rotating disk in the presence of gyrotactic microorganisms is investigated. The governing equations modeling the flow are solved numerically using the newly introduced simple iteration method (SIM) that seeks to linearize a system using relaxation technique that effectively decouples the system. To verify the convergence and accuracy of the method, solution error and residual error analysis are carried out, respectively. The obtained results suggest that the SIM is a highly efficient method that produces convergent and highly accurate solutions. The effects of various parameters as well as combined parameter effects on the solution profiles are also investigated. An increase in the Hall and permeability parameters leads to a corresponding rise in the microorganism’s density and nanoparticle volume fraction.Item Spectrum of ascending aortic aneurysms at a peri-urban tertiary hospital: an echocardiography-based study(Oxford University Press, 2023-07) Meel, Ruchika; Hasenkam, Michael; Goncalves, Ricardo; Goncalvev, Ricardo; Mogaladi, ShunguIntroduction: Thoracic ascending aortic (TAA) aneurysms are an important cause of disability and death and require early detection for effective management. Currently, there is a paucity of data from Africa pertaining to TAA aneurysms. This study describes the spectrum of TAA aneurysms at a peri-urban tertiary hospital. Methods: A descriptive retrospective study based on clinical and echocardiographic imaging data of patients with TAA aneurysms from October 2017–October 2022. Advanced strain imaging was performed to measure left ventricular (LV) basal, apical, and global longitudinal strain as well as circumferential strain (CS) of the ascending aorta as a proxy measurement of aortic compliance. Results: The study comprised 139 cases of TAA aneurysms (52.5% females) with a mean age of 50 ± 14.8 years with 45 age and gender matched controls. Most cases (95%) were of African ethnicity. The main etiologies were hypertension (41.7%), HIV (36.6%), connective tissue disease (10.7%), congenital (2.2%) and mixed pathologies (8.6%). Two-thirds of patients (69.7%) presented in heart failure, 10% presented with aortic dissection. Thirty percent of the patients were classified as New York Heart Association (NYHA) class I, 59.7% NYHA II, 8.6% NYHA III and two patients NYHA class IV. Echocardiography revealed enlarged aortic dimensions compared to controls (P < 0.001). TAA aneurysms were complicated by severe aortic regurgitation (AR) in half (50.3%) of patients, moderate AR in 25.8%, and mild AR in 14.3%. The mean LV ejection fraction (46.9 ± 12.7%) was reduced compared to controls (P < 0.001). Aortic CS was reduced compared to controls [4.4 (3.2–6.2) % vs. 9.0 (7.1–13.4) %, P < 0.001]. Aortic stiffness was higher in the aortic aneurysm group compared to controls (15.39 ± 20.65 vs. 5.04 ± 2.09, P = 0.001). LV longitudinal strain (−13.9 ± 3.9% vs. 18.1 ± 6.7%), basal CS (−13.9 ± 5.6% vs. −17.9 ± 5.8%) and apical CS (−8.7 ± 8.5% vs. −30.6 ± 3.8%) were reduced compared to controls (P < 0.001). Most patients were on diuretic and anti-remodeling therapy. Surgery was performed in 29.4% and overall mortality was 7.9%. Mortality for acute aortic dissection was 40%. Conclusion: TAA aneurysms associated with hypertension and HIV are common in this predominantly African female population and are associated with considerable morbidity and mortality. Two-dimensional echocardiography and advanced strain imaging are potential tools for detecting and risk stratifying TAA aneurysms.Item Causes and predictors of mortality in South Africans with systemic sclerosis(Wiley, 2023-05) Dire, Zodwa; Ickinger, Claudia; Tikly, MohammedBackground: There is a dearth of mortality data on systemic sclerosis (SSc) in sub‐Saharan Africa. We undertook a retrospective study of causes and predictors of death in low‐income indigent South Africans with SSc. Methods: A retrospective records review of clinicodemographic, laboratory, and outcome data of SSc patients attending a state‐funded tertiary Rheumatology service in South Africa. Results: Most of the 164 patients were Black (92.7%) and female (87.8%). The mean (SD) age at diagnosis and follow‐up duration were 42.6 (12.9) and 5.5 (5.6) years, respectively. The majority (75.6%) had diffuse cutaneous SSc (dcSSc); and digital pits/ulcers, interstitial lung disease (ILD), and pulmonary hypertension (PH) were documented in 73.6%, 55.0%, and 38.3%, respectively. There were 56 known deaths and an equal number of patients were lost to follow‐up. Deaths resulted from ILD complicated by PH (42.9%), infections (8.9%), cardiac disease (7.1%), and malignancies (3.6%). Estimated 5‐ and 10‐year survival rates for patients with known outcomes were 58% and 42%, respectively. Independent predictors of death were renal dysfunction and cor pulmonale. Conclusion: Most patients in this study of South Africans had dcSSc and poor outcomes. Known deaths resulted from cardiorespiratory complications of ILD complicated by PH. Cor pulmonale and renal dysfunction were independent predictors of death.Item Projecting Podocarpaceae response to climate change: we are not out of the woods yet(Oxford University Press, 2023-06) Twala, Thando C.; Fisher, Jolene T.; Glennon, Kelsey L.Under the changing climate, the persistence of Afrotemperate taxa may be threatened as suitable habitat availability decreases. The unique disjunct ranges of podocarps in southern Africa raise questions about the persistence of these species under climate change. Here, we identified likely environmental drivers of these distributions, characterized the current and future (2070) environmental niches, and projected distributions of four podocarp species in South Africa. Species distribution models were conducted using species locality data for Afrocarpus falcatus, Podocarpus latifolius, Pseudotropheus elongatus and Podocarpus henkelii and both historical climate data (1970–2000) and future climate scenarios (Representative Concentration Pathway [RCP] 4.5 and 8.5, 2061–2080) to estimate the current and future distributions. We also used this opportunity to identify the most important climatic variables that likely govern each species’ distribution. Using niche overlap estimates, a similarity test, and indices of niche expansion, stability and unfilling, we explored how niches change under different climate scenarios. The distribution of the study species was governed by the maximum temperature of the warmest month, temperature annual range, mean temperature of the wettest quarter, and precipitation of the wettest, driest and warmest quarters. The current distribution of A. falcatus was predicted to expand to higher elevations under RCP 4.5 and RCP 8.5. Podocarpus henkelii was predicted to lose most of its suitable habitat under RCP 4.5 and expand under RCP 8.5; however, this was the opposite for P. elongatus and P. latifolius. Interestingly, P. elongatus, which had the smallest geographic distribution, showed the most vulnerability to climate change in comparison to the other podocarps. Mapping the distribution of podocarps and understanding the differences in their current and future climate niches provide insight into potential climate drivers of podocarp persistence and the potential for adaptation of these species. Overall, these results suggest that P. elongatus and P. henkelii may expand to novel environmental niches.Item Association of close-range contact patterns with SARS-CoV-2: a household transmission study(eLife Sciences Publications, 2023-07) Kleynhans, Jackie; Dall'Amico, Lorenzo; Gauvin, Laetitia; Tizzoni, Michele; Maloma, Lucia; Walaza, Sibongile; Martinson, Neil A.; von Gottberg, Anne; Wolter, Nicole; Makhasi, Mvuyo; Cohen, Cheryl; Cattuto, Ciro; Tempia, StefanoBackground: Households are an important location for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission, especially during periods when travel and work was restricted to essential services. We aimed to assess the association of close-range contact patterns with SARS-CoV-2 transmission. Methods: We deployed proximity sensors for two weeks to measure face-to-face interactions between household members after SARS-CoV-2 was identified in the household, in South Africa, 2020-2021. We calculated the duration, frequency, and average duration of close-range proximity events with SARS-CoV-2 index cases. We assessed the association of contact parameters with SARS-CoV-2 transmission using mixed effects logistic regression accounting for index and household member characteristics. Results: We included 340 individuals (88 SARS-CoV-2 index cases and 252 household members). On multivariable analysis, factors associated with SARS-CoV-2 acquisition were index cases with minimum Ct value <30 (aOR 16.8 95% CI 3.1-93.1) vs >35, and female contacts (aOR 2.5 95% CI 1.3-5.0). No contact parameters were associated with acquisition (aOR 1.0-1.1) for any of the duration, frequency, cumulative time in contact, or average duration parameters. Conclusions: We did not find an association between close-range proximity events and SARS-CoV-2 household transmission. Our findings may be due to study limitations, that droplet-mediated transmission during close-proximity contacts plays a smaller role than airborne transmission of SARS-CoV-2 in the household, or due to high contact rates in households.