University of the Witwatersrand

About: University of the Witwatersrand is a education organization based out in Johannesburg, South Africa. It is known for research contribution in the topics: Population & Context (language use). The organization has 25215 authors who have published 52766 publications receiving 1347668 citations. The organization is also known as: Wits University & University of Witwatersrand.

Investigation of hot ductility in Al-killed boron steels

Abstract: The influence of boron to nitrogen ratio, strain rate and cooling rate on hot ductility of aluminium-killed, low carbon, boron microalloyed steel was investigated. Hot tensile testing was performed on steel samples reheated in argon to 1300 °C, cooled at rates of 0.3, 1.2 and 3.0 °C s −1 to temperatures in the range 750–1050 °C, and then strained to failure at initial strain rates of 1 × 10 −4 or 1 × 10 −3 s −1 . It was found that the steel with a B:N ratio of 0.19 showed deep hot ductility troughs for all tested conditions; the steel with a B:N ratio of 0.47 showed a deep ductility trough for a high cooling rate of 3.0 °C s −1 and the steel with a near-stoichiometric B:N ratio of 0.75 showed no ductility troughs for the tested conditions. The ductility troughs extended from ∼900 °C (near the Ae 3 temperature) to ∼1000 or 1050 °C in the single-phase austenite region. The proposed mechanism of hot ductility improvement with increase in B:N ratio in these steels is that the B removes N from solution, thus reducing the strain-induced precipitation of AlN. Additionally, BN co-precipitates with sulphides, preventing precipitation of fine MnS, CuS and FeS, and forming large, complex precipitates that have no effect on hot ductility.

Relationship between Household Socio-Economic Status and Under- Five Mortality in Rufiji DSS, TANZANIA.

Abstract: Background : Disparities in health outcomes between the poor and the better off are increasingly attracting attention from researchers and policy makers. However, policies aimed at reducing inequity need to be based on evidence of their nature, magnitude, and determinants. Objectives : The study aims to investigate the relationship between household socio-economic status (SES) and under-five mortality, and to measure health inequality by comparing poorest/least poor quintile mortality rate ratio and the use of a mortality concentration index. It also aims to describe the risk factors associated with under-five mortality at Rufiji Demographic Surveillance Site (RDSS), Tanzania. Methods : This analytical cross sectional study included 11,189 children under-five residing in 7,298 households in RDSS in 2005. Principal component analysis was used to construct household SES. KaplanMeier survival incidence estimates were used for mortality rates. Health inequality was measured by calculating and comparing mortality rates between the poorest and least poor wealth quintile. We also computed a mortality concentration index. Risk factors of child mortality were assessed using Poisson regression taking into account potential confounders. Results : Under-five mortality was 26.9 per 1,000 person-years [95% confidence interval (CI) (23.7-30.4)]. The poorest were 2.4 times more likely to die compared to the least poor. Our mortality concentration index [0.16; 95% CI (-0.24, -0.08)] indicated considerable health inequality. Least poor households had a 52% reduced mortality risk [incidence rate ratio (IRR) = 0.48; 95% CI 0.30-0.80]. Furthermore, children with mothers who had attained secondary education had a 70% reduced risk of dying compared to mothers with no education [IRR=0.30; 95% CI (0.22-0.88)]. Conclusion : Household socio-economic inequality and maternal education were associated with under-five mortality in the RDSS. Targeted interventions to address these factors may contribute towards accelerating the reduction of child mortality in rural Tanzania. Keywords : inequality; socio-economic status; principal component analysis; mortality concentration index (Published: 24 January 2013) Citation: Glob Health Action 2013, 6 : 19278 - http://dx.doi.org/10.3402/gha.v6i0.19278

Age-Disparate Partnerships and Risk of HIV-1 Acquisition Among South African Women Participating in the VOICE Trial.

Abstract: A recent analysis from South Africa reported no association between age-disparate relationships and HIV-1 acquisition. We assessed the association between male partner age and HIV-1 acquisition among South African women participating in the VOICE trial. Of 4077 women enrolled, 3789 had complete data; 26% and 5% reported having a partner >5 and >10 years older at enrollment, respectively. Reporting a partner >5 years older (hazard ratio = 1.00; 95% confidence interval: 0.74 to 1.35) or >10 older (hazard ratio = 0.92; 95% confidence interval: 0.49 to 1.74) was not associated with HIV-1 acquisition. These data corroborate recent reports and may suggest a shift in local epidemiology of heterosexual HIV-1 transmission.