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6. Exploratory Analysis of Multivariate Longitudinal Child Education Data

Author

Visaya, Maria Vivien, Sherwell, David, Kimpolo, Charles, and Collinson, Mark

Subjects
Statistics - Applications
Abstract

We analyse binary multivariate longitudinal data of a population of households from a rural district in South Africa. Using a 2-dimensional graphical representation of longitudinal data, each household's data is transformed into a time-evolving geometric orbit. Orbits communicate complete information of change in the data over time and provide insights into the dynamics of both a household's and the population's evolution. The outcome of interest is child educational default, where defaulting is defined as having failed more than three years of schooling. A visual analysis of the impact on educational default of three household factors, namely the presence of a biological mother, the age of the household head (minor- or adult- headed household) and the death of an adult, is presented. In both the non-defaulting and defaulting households, dynamics is mainly described by the temporary in- and out-migration of biological mothers. We find that the presence of mother is more likely in the non-defaulting households. Owing to insufficient events involving change in the age of the household head and adult deaths, we have no conclusion regarding their effect. Orbits offer easily interpreted information of clusters, patterns of change, and the density of state transitions of household orbits., Comment: 27 pages, 10 figures

Published
2015

7. Cohort Profile: Migrant Health Follow-Up Study (MHFUS) of internal migration in South Africa.

Author

Ginsburg, Carren, Collinson, Mark A, Pheiffer, Chantel F, Gómez-Olivé, F Xavier, Harawa, Sadson, McGarvey, Stephen T, Ohene-Kwofie, Daniel, Foster, Andrew D, Myroniuk, Tyler W, Lurie, Mark N, Tollman, Stephen M, and White, Michael J

Subjects
*HUMAN behavior, *RURAL health, *RURAL-urban migration, *HEALTH services accessibility, *SLEEP quality, *YOUNG adults, *DEMOGRAPHIC characteristics
Abstract

The Migrant Health Follow-Up Study (MHFUS) is a longitudinal study conducted in South Africa to examine the consequences of migration and urbanization on individual health. The study has collected data on education, employment, migration, household composition, health, health service use, and diet through four study waves between 2018 and 2022. The MHFUS aims to understand the impact of migration and urbanization on non-communicable and infectious diseases and treatment continuity. The study has achieved a high retention rate of 98% of participants. The study provides valuable insights into the experiences and well-being of migrants in the country. [Extracted from the article]

Published
2024
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10. Clustering South African households based on their asset status using latent variable models

Author

McParland, Damien, Gormley, Isobel Claire, McCormick, Tyler H., Clark, Samuel J., Kabudula, Chodziwadziwa Whiteson, and Collinson, Mark A.

Subjects
Statistics - Applications, Statistics - Methodology
Abstract

The Agincourt Health and Demographic Surveillance System has since 2001 conducted a biannual household asset survey in order to quantify household socio-economic status (SES) in a rural population living in northeast South Africa. The survey contains binary, ordinal and nominal items. In the absence of income or expenditure data, the SES landscape in the study population is explored and described by clustering the households into homogeneous groups based on their asset status. A model-based approach to clustering the Agincourt households, based on latent variable models, is proposed. In the case of modeling binary or ordinal items, item response theory models are employed. For nominal survey items, a factor analysis model, similar in nature to a multinomial probit model, is used. Both model types have an underlying latent variable structure - this similarity is exploited and the models are combined to produce a hybrid model capable of handling mixed data types. Further, a mixture of the hybrid models is considered to provide clustering capabilities within the context of mixed binary, ordinal and nominal response data. The proposed model is termed a mixture of factor analyzers for mixed data (MFA-MD). The MFA-MD model is applied to the survey data to cluster the Agincourt households into homogeneous groups. The model is estimated within the Bayesian paradigm, using a Markov chain Monte Carlo algorithm. Intuitive groupings result, providing insight to the different socio-economic strata within the Agincourt region., Comment: Published in at http://dx.doi.org/10.1214/14-AOAS726 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Published
2014
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11. On the characterisation of shock-induced sliding along multi-material interfaces

Author

Collinson, Mark and Eakins, Daniel

Subjects
530
Abstract

Experimental results utilising novel diagnostic techniques focussing on spatial resolution of shock-induced sliding phenomena at multi-material aluminium - stainless steel dry metallic contact interfaces are presented. Relative particle velocities of 50 m s⁻¹ are generated at the sliding interface via an intrinsic impedance mismatch between the material components, driven by gas gun flyer plate impact. Results are first presented for the metallography of recovered target samples from shock-induced sliding contact interfaces where the intrinsic grain structure is utilised as a fiducial marker to provide a measure of the sub-surface deformation experienced. Two distinct mutually exclusive scales of deformation were identified extending over millimetre and micrometre depths with relatively low and high free surface sliding velocities measured for these respectively using optical velocimetry. Further experimental results are presented for spatially resolved velocimetry of shock-induced sliding at planar material interfaces utilising a line-VISAR diagnostic. Experiments are conducted over 3 mm and 15 mm interface length scales with the contact interface orientated at 0.0° and 5.0° relative to the direction of loading. Specific material pairings of aluminium 1050 and aluminium 7068 paired independently with stainless steel 316 were utilised. An initial large scale experiment was found to be suggestive of the role of gaps at the contact interface, estimated to be 35 μm in size via comparison of the velocimetry data with hydrocode models. Further mesoscale experiments are suggestive of the role of re-shock and release waves generated at the contact face co-incident with the breakout of the elastic and plastic shock fronts, defining the velocimetry profile in close vicinity of the contact face over the timescales measured.

Published
2015
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15. Protective Behaviors and Secondary Harms Resulting From Nonpharmaceutical Interventions During the COVID-19 Epidemic in South Africa: Multisite, Prospective Longitudinal Study

Author

Harling, Guy, Gómez-Olivé, Francesc Xavier, Tlouyamma, Joseph, Mutevedzi, Tinofa, Kabudula, Chodziwadziwa Whiteson, Mahlako, Ruth, Singh, Urisha, Ohene-Kwofie, Daniel, Buckland, Rose, Ndagurwa, Pedzisai, Gareta, Dickman, Gunda, Resign, Mngomezulu, Thobeka, Nxumalo, Siyabonga, Wong, Emily B, Kahn, Kathleen, Siedner, Mark J, Maimela, Eric, Tollman, Stephen, Collinson, Mark, and Herbst, Kobus

Subjects
Public aspects of medicine, RA1-1270
Abstract

BackgroundIn March 2020, South Africa implemented strict nonpharmaceutical interventions (NPIs) to contain the spread of COVID-19. Over the subsequent 5 months, NPI policies were eased in stages according to a national strategy. COVID-19 spread throughout the country heterogeneously; the disease reached rural areas by July and case numbers peaked from July to August. A second COVID-19 wave began in late 2020. Data on the impact of NPI policies on social and economic well-being and access to health care are limited. ObjectiveWe aimed to determine how rural residents in three South African provinces changed their behaviors during the first COVID-19 epidemic wave. MethodsThe South African Population Research Infrastructure Network nodes in the Mpumalanga (Agincourt), KwaZulu-Natal, (Africa Health Research Institute) and Limpopo (Dikgale-Mamabolo-Mothiba) provinces conducted up to 14 rounds of longitudinal telephone surveys among randomly sampled households from rural and periurban surveillance populations every 2-3 weeks. Interviews included questions on the following topics: COVID-19–related knowledge and behaviors, the health and economic impacts of NPIs, and mental health. We analyzed how responses varied based on NPI stringency and household sociodemographics. ResultsIn total, 5120 households completed 23,095 interviews between April and December 2020. Respondents’ self-reported satisfaction with their COVID-19–related knowledge and face mask use rapidly rose to 85% and 95%, respectively, by August. As selected NPIs were eased, the amount of travel increased, economic losses were reduced, and the prevalence of anxiety and depression symptoms fell. When the number of COVID-19 cases spiked at one node in July, the amount of travel dropped rapidly and the rate of missed daily medications doubled. Households where more adults received government-funded old-age pensions reported concerns about economic matters and medication access less often. ConclusionsSouth Africans complied with stringent, COVID-19–related NPIs despite the threat of substantial social, economic, and health repercussions. Government-supported social welfare programs appeared to buffer interruptions in income and health care access during local outbreaks. Epidemic control policies must be balanced against the broader well-being of people in resource-limited settings and designed with parallel support systems when such policies threaten peoples’ income and access to basic services.

Published
2021
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16. The UCL–Lancet Commission on Migration and Health: the health of a world on the move

Author

Abubakar, Ibrahim, Aldridge, Robert W, Devakumar, Delan, Orcutt, Miriam, Burns, Rachel, Barreto, Mauricio L, Dhavan, Poonam, Fouad, Fouad M, Groce, Nora, Guo, Yan, Hargreaves, Sally, Knipper, Michael, Miranda, Jaime, Madise, Nyovani, Kumar, Bernadette, Mosca, Davide, McGovern, Terry, Rubenstein, Leonard, Sammonds, Peter, Sawyer, Susan M, Sheikh, Kabir, Tollman, Stephen, Spiegel, Paul, Zimmerman, Cathy, Abbas, Mustafa, Acer, Eleanor, Ahmad, Ayesha, Abimbola, Seye, Blanchet, Karl, Bocquier, Philippe, Samuels, Fiona, Byrne, Olga, Haerizadeh, Sonia, Issa, Rita, Collinson, Mark, Ginsburg, Carren, Kelman, Ilan, McAlpine, Alys, Pocock, Nicola, Olshansky, Barbara, Ramos, Dandara, White, Michael, Zhou, Suzanne, and Miranda, J Jaime

Published
2018
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28. Strain rate dependence of single crystal tantalum.

Author

Collinson, Mark, Whiteman, Glenn, Millett, Jeremy, Cox, Michael, Quinn, Robert, Hooper, Paul, and Chiu, Yu-Lung

Subjects
*SINGLE crystals, *STRAINS & stresses (Mechanics), *TANTALUM, *STRAIN rate, *CRYSTAL lattices
Abstract

Compression experiments are presented on single crystal tantalum in lattice orientations [100], [110], [111] and [1̅49] across a wide range of strain rates from 10−3 s−1 to 104 s−1. Experiments utilised a screw driven load frame and miniature split Hopkinson pressure bar, complementing existing plate impact and Taylor test data. All orientations demonstrated an approximate log-linear relationship between flow stress and strain rate, with an increase in flow stress observed at 104 s−1 in all orientations except [110]. Large variations in flow stress between the various orientations were noted, with Schmid analysis and final state deformation geometry suggesting the dominance of {112} slip. [ABSTRACT FROM AUTHOR]

Published
2023
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30. Patterns and trends in household food security in rural Mpumalanga Province, South Africa.

Author

Rusere, Farirai, Hunter, Lori, Collinson, Mark, and Twine, Wayne

Subjects
FOOD security, HOUSEHOLDS, PRINCIPAL components analysis, ECONOMIC opportunities
Abstract

This study examines patterns and trends in household food security in Bushbuckridge, Mpumalanga Province, South Africa, from 2010 to 2019. We use data from a household panel nested in the Agincourt Health and Socio-Demographic Surveillance System. Findings indicate that there have been improvements in household food security in this rural setting over the last decade. By polychoric principal component analysis, an aggregate food security index was constructed and we observed a small, yet important, proportion of households (7.8%) that remained chronically food insecure. An ordered probit model was used to estimate the determinants of food security. Findings reveal that the observed differences in household food security status are as a result of differences in socioeconomic status. We therefore recommend that focus must be placed on identifying economic opportunities and empowering the chronically food insecure households if universal household food security is to be attained in rural South Africa and beyond. [ABSTRACT FROM AUTHOR]

Published
2024
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31. Development and validation of a diagnostic aid for convulsive epilepsy in sub-Saharan Africa: a retrospective case-control study

Author

Jones, Gabriel Davis, primary, Kariuki, Symon M, additional, Ngugi, Anthony K, additional, Mwesige, Angelina Kakooza, additional, Masanja, Honorati, additional, Owusu-Agyei, Seth, additional, Wagner, Ryan, additional, Cross, J Helen, additional, Sander, Josemir W, additional, Newton, Charles R, additional, Sen, Arjune, additional, Abban, Hanna, additional, Adjei, Patrick, additional, Ae-Ngibise, Ken, additional, Agbokey, Francis, additional, Aissaoui, Lisa, additional, Akpalu, Albert, additional, Akpalu, Bright, additional, Asiamah, Sabina, additional, Asiki, Gershim, additional, Atieno, Mercy, additional, Bauni, Evasius, additional, Bhwana, Dan, additional, Bitta, Mary, additional, Bottomley, Christian, additional, Chabi, Martin, additional, Chengo, Eddie, additional, Chowdhary, Neerja, additional, Connor, Myles, additional, Cross, Helen, additional, Collinson, Mark, additional, Darkwa, Emmanuel, additional, Denison, Timothy, additional, Doku, Victor, additional, Dua, Tarun, additional, Egesa, Isaac, additional, Godi, Tony, additional, Gómez-Olivé, F. Xavier, additional, Grassi, Simone, additional, Iddi, Samuel, additional, Junior, Daniel Nana Yaw Abankwah, additional, Kahn, Kathleen, additional, Kakooza, Angelina, additional, Kariuki, Symon, additional, Kamuyu, Gathoni, additional, Khalayi, Clarah, additional, Kimambo, Henrika, additional, Kleinschmidt, Immo, additional, Kwasa, Thomas, additional, Mahone, Sloan, additional, Manolova, Gergana, additional, Mathew, Alexander, additional, Matuja, William, additional, McDaid, David, additional, Mmbando, Bruno, additional, Mtai Mwanga, Daniel, additional, Muli, Dorcas, additional, Mung'ala Odera, Victor, additional, Murunga Wekesah, Frederick, additional, Mushi, Vivian, additional, Ngugi, Anthony, additional, Odermatt, Peter, additional, Odhiambo, Rachael, additional, O Mageto, James, additional, Otieno, Peter, additional, Pariyo, George, additional, Peterson, Stefan, additional, Sander, Josemir, additional, Sottie, Cynthia, additional, Sylvester, Isolide, additional, Tollman, Stephen, additional, Thoya, Yvonne, additional, Twine, Rhian, additional, Vallentin, Sonia, additional, Walker, Richard, additional, and Waruingi, Stella, additional

Published
2023
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32. Epidemiology of chronic multimorbidity and temporary migration in a rural South African community in health transition: A cross-sectional population-based analysis

Author

Dzomba, Armstrong, primary, Ginsburg, Carren, additional, Kabudula, Chodziwadziwa W., additional, Yorlets, Rachel R., additional, Ndagurwa, Pedzisai, additional, Harawa, Sadson, additional, Lurie, Mark N., additional, McGarvey, Stephen T., additional, Tollman, Stephen, additional, Collinson, Mark A., additional, White, Michael J., additional, and Gomez-Olive, Francesc X., additional

Published
2023
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37. Correction to: Validity of Self-Report for Ascertaining HIV Status Among Circular Migrants and Permanent Residents in South Africa: A Cross-Sectional, Population-Based Analysis

Author

Yorlets, Rachel R, primary, Lurie, Mark N, additional, Ginsburg, Carren, additional, Hogan, Joseph W, additional, Joyce, Nina R, additional, Harawa, Sadson, additional, Collinson, Mark A, additional, Gómez-Olivé, F Xavier, additional, and White, Michael J, additional

Published
2022
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