- ItemOpen AccessThe Electrochemical Response of Chalcopyrite and Galena to Degrading Water Quality(2022-11-21) Ndamase, Nolihle; Tadie, Margreth; Corin, Kirsten ClaireWater is used as a liquid medium as well as a means of transportation during mining operations. Flotation, in particular, is a water intensive process where water makes up about 80–85% of the pulp phase. Process water contains organic and inorganic species which accumulate as they are recycled. To avoid the treatment costs of removing these contaminants, many mining operations allow the quality of their water to degrade over time. When this water is introduced into flotation circuits, the pulp chemistry is altered. Ionic species that accumulate in recycled process water have been shown by previous studies to be especially deleterious to flotation performance. Such ions include Ca2+, Cu2+, Mg2+, Pb2+, SO42− and S2O32−, amongst others. The flotation sub-process of collector adsorption which is responsible for inducing hydrophobicity on valuable mineral surfaces may be influenced by water chemistry. Accumulating ionic species have been shown to hinder collector adsorption which may reduce recovery of valuable minerals to the concentrate. Consequently, degrading water quality may threaten the economic viability of mining operations that make use of closed water circuits. Electrochemical techniques such as mineral rest potentials can be used to monitor the impact of changing water quality on collector–mineral interactions. Microflotation was used to determine whether mineral floatability was affected by changing water quality. This study therefore aimed to investigate whether electrochemical techniques such as rest potential measurements can be used to predict flotation performance under changing water quality. No definable relationship was found between the rest potential differences and the microflotation initial recoveries, however, rest potential measurements did identify the negative impact that thiosulphate ions may have on flotation processes.
- ItemOpen AccessImportance of ventilation and occupancy to Mycobacterium tuberculosis transmission rates in congregate settings(2022-09-19) Deol, A. K.; Shaikh, N.; Middelkoop, K.; Mohlamonyane, M.; White, R. G.; McCreesh, N.Abstract Background Ventilation rates are a key determinant of the transmission rate of Mycobacterium tuberculosis and other airborne infections. Targeting infection prevention and control (IPC) interventions at locations where ventilation rates are low and occupancy high could be a highly effective intervention strategy. Despite this, few data are available on ventilation rates and occupancy in congregate locations in high tuberculosis burden settings. Methods We collected carbon dioxide concentration and occupancy data in congregate locations and public transport on 88 occasions, in Cape Town, South Africa. For each location, we estimated ventilation rates and the relative rate of infection, accounting for ventilation rates and occupancy. Results We show that the estimated potential transmission rate in congregate settings and public transport varies greatly between different settings. Overall, in the community we studied, estimated infection risk was higher in minibus taxis and trains than in salons, bars, and shops. Despite good levels of ventilation, infection risk could be high in the clinic due to high occupancy levels. Conclusion Public transport in particular may be promising targets for infection prevention and control interventions in this setting, both to reduce Mtb transmission, but also to reduce the transmission of other airborne pathogens such as measles and SARS-CoV-2.
- ItemOpen AccessAn Overview of Frontier Technologies for Land Tenure: How to Avoid the Hype and Focus on What Matters(2022-10-31) Hull, Simon; Liversage, Harold; Rizzo, Maria Paola; Evtimov, VladimirSecure land and natural resource rights are key ingredients for rural transformation, social inclusion, and the realization of the Sustainable Development Goals. In many cases, these rights are not formally recorded, and statutory land administration systems are inaccessible to rural communities. The rapid development of geospatial technologies and systems, combined with participatory methods for social empowerment, have contributed significantly to addressing these challenges and in developing fit-for-purpose land administration/land recordation systems that promote land tenure security, but with the plethora of options currently available, it is challenging to know which technologies are appropriate for what circumstances and purposes. This paper reports on the findings from a joint FAO/IFAD project that addresses this problem. Thirteen one-hour interviews were conducted with knowledgeable experts to showcase which technologies are being used for what purposes and by whom, the associated benefits and challenges, and what the future may hold. We conclude that technologies are best used in partnership with communities and as integrated solutions, that successful implementations must incorporate maintenance plans, and that the real challenge is not the technology–it is the social, legal, and political context. These findings are useful for governments, NGOs, academia, donors, and others involved in land-related projects aimed at benefitting small-scale farmers.
- ItemOpen AccessA quantitative assessment of the consistency of projections from five mathematical models of the HIV epidemic in South Africa: a model comparison study(2023-10-27) Moolla, Haroon; Phillips, Andrew; ten Brink, Debra; Mudimu, Edinah; Stover, John; Bansi-Matharu, Loveleen; Martin-Hughes, Rowan; Wulan, Nisaa; Cambiano, Valentina; Smith, Jennifer; Bershteyn, Anna; Meyer-Rath, Gesine; Jamieson, Lise; Johnson, Leigh F.Abstract Background Mathematical models are increasingly used to inform HIV policy and planning. Comparing estimates obtained using different mathematical models can test the robustness of estimates and highlight research gaps. As part of a larger project aiming to determine the optimal allocation of funding for HIV services, in this study we compare projections from five mathematical models of the HIV epidemic in South Africa: EMOD-HIV, Goals, HIV-Synthesis, Optima, and Thembisa. Methods The five modelling groups produced estimates of the total population, HIV incidence, HIV prevalence, proportion of people living with HIV who are diagnosed, ART coverage, proportion of those on ART who are virally suppressed, AIDS-related deaths, total deaths, and the proportion of adult males who are circumcised. Estimates were made under a “status quo” scenario for the period 1990 to 2040. For each output variable we assessed the consistency of model estimates by calculating the coefficient of variation and examining the trend over time. Results For most outputs there was significant inter-model variability between 1990 and 2005, when limited data was available for calibration, good consistency from 2005 to 2025, and increasing variability towards the end of the projection period. Estimates of HIV incidence, deaths in people living with HIV, and total deaths displayed the largest long-term variability, with standard deviations between 35 and 65% of the cross-model means. Despite this variability, all models predicted a gradual decline in HIV incidence in the long-term. Projections related to the UNAIDS 95–95-95 targets were more consistent, with the coefficients of variation below 0.1 for all groups except children. Conclusions While models produced consistent estimates for several outputs, there are areas of variability that should be investigated. This is important if projections are to be used in subsequent cost-effectiveness studies.
- ItemOpen AccessMamekhaya: a pilot study combining a cognitive-behavioral intervention and mentor mothers with PMTCT services in South Africa(2010) Futterman, D., Shea, J., Besser, M., Stafford, S., Desmond, K., Comulada, W. S., &; Greco, ENearly 30% of pregnant women in South Africa are estimated to be HIV seropositive, yet adherence to guidelines for the prevention of mother-to-child transmission of HIV (PMTCT) is often low. A pilot study was developed to see whether PMTCT services provided by the South African Government could be enhanced by the Mamekhaya program, a combination of the mothers2mothers peer-mentoring program and a culturally adapted cognitive-behavioral intervention (CBI) from the USA. Pregnant women attending two maternity clinics offering PMTCT in Gugulethu and Vanguard Townships, Cape Town, South Africa, were invited to participate in the study. Women at the intervention site (Gugulethu) received the support of a mentor mother and also attended an eight-session Mamekhaya CBI. At the control site (Vanguard), women received standard services provided by midwives and counselors. Baseline assessments were completed by all participants at enrollment (n=160), and follow-ups were completed six months later by 44% of participants. Self-reports of adherence to PMTCT practices were high across both sites (90% or more engaging in the core practices). Women at the Mamekhaya site showed significantly greater improvement in establishing social support and reducing depression scores than women at the control site. Mamekhaya participants also showed trends for better attendance at follow-up medical visits, and greater improvements in positive coping. The greatest effect of the Mamekhaya program was to increase HIV knowledge scores, particularly with regard to understanding the meaning and importance of viral load and CD4 test results. Results from this pilot study show promise that augmenting basic PMTCT services with mentor mothers and a culturally adapted CBI can be effective in conveying information and in improving the emotional outlook and hopefulness of HIV-positive pregnant women in South Africa.