22 results on '"Ndlovu, J."'
Search Results
2. Employment experiences of post graduate students in KwaZulu-Natal: An intersection of qualifications and employability in the labor market
- Author
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Ndebele, N.C., primary and Ndlovu, J., additional
- Published
- 2019
- Full Text
- View/download PDF
3. 10 kVp rule - An anthropomorphic pelvis phantom imaging study using a CR system: impact on image quality and effective dose using AEC and manual mode
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Lança, Luís, Franco, L., Ahmed, A., Harderwijk, M., Nasir, S., Ndlovu, J., Oliveira, M., Santiago, A., and Hogg, Peter
- Subjects
Effective dose ,Pelvis phantom ,AEC ,education ,respiratory system ,Radiology - Abstract
Purpose: This study aims to investigate the influence of tube potential (kVp) variation in relation to perceptual image quality and effective dose for pelvis using automatic exposure control (AEC) and non-AEC in a computed radiography (CR) system. Methods and Materials: To determine the effects of using AEC and non-AEC by applying the 10 kVp rule in two experiments using an anthropomorphic pelvis phantom. Images were acquired using 10 kVp increments (60-120 kVp) for both experiments. The first experiment, based on seven AEC combinations, produced 49 images. The mean mAs from each kVp increment were used as a baseline for the second experiment producing 35 images. A total of 84 images were produced and a panel of 5 experienced observers participated for the image scoring using the 2 AFC visual grading software. PCXMC software was used to estimate the effective dose. Results: A decrease in perceptual image quality as the kVp increases was observed both in non-AEC and AEC experiments, however no significant statistical differences (p> 0.05) were found. Image quality scores from all observers at 10 kVp increments for all mAs values using non-AEC mode demonstrates a better score up to 90 kVp. Effective dose results show a statistical significant decrease (p=0.000) on the 75th quartile from 0.3 mSv at 60 kVp to 0.1 mSv at 120 kVp when applying the 10 kVp rule in non-AEC mode. Conclusion: No significant reduction in perceptual image quality is observed when increasing kVp whilst a marked and significant effective dose reduction is observed.
- Published
- 2014
4. Challenges and solutions in PGM furnace operation: high matte temperature and copper cooler corrosion
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Shaw, A, de Villiers, L.P.vS, Hundermark, R.J, Ndlovu, J, Nelson, L.R, Pieterse, B, Sullivan, R, Voermann, N, Walker, C, Stober, F, and McKenzie, A.D
- Subjects
corrosion ,copper cooler ,PGM smelting ,matte temperature ,chloride-accelerated sulphidation - Abstract
The key aspects of process metallurgy that distinguish platinum group metal (PGM) concentrate smelting from that of other base metal sulphide concentrates are presented. These differences include considerably higher input chrome and magnesia contents that directly raise the slag liquidus temperature and have the potential to increase accumulations of refractory spinels. Most importantly, the higher processing temperature required for PGM smelting and the resulting very high matte superheat lead to considerably more onerous smelting conditions than those typical of other smelting operations. This has presented challenges to furnace design and integrity, especially when coupled with the progressive intensification of smelting, involving doubling, and then redoubling, of furnace power inputs over the past 20 years. These power increases have been enabled by increasingly more advanced furnace cooling and structural technologies. Key technologies include strong constant-force spring-loaded bindings acting in three dimensions to minimize infiltration of superheated matte into brick joints, and robust well-cooled tapholes for reliably tapping the superheated matte. The result has been substantially improved productivity, and reduced smelting capital cost outlay per unit of production. A significant challenge, which was not anticipated, presented itself in the form of insidious corrosion of the furnace lining, and especially high-intensity copper cooling elements. Investigation of corrosion in related industries eventually identified 'chloride-accelerated sulphidation', and this term has been retained as it generically describes the most pertinent aspects of the accelerated low-temperature wear of copper coolers observed in PGM smelting. In addition to discussing the corrosion mechanism, this paper describes a number of solutions that were developed jointly by Anglo American Platinum and Hatch to address the copper corrosion problem. First, new monitoring technologies allowed furnaces to be operated more safely for a longer period of time. Second, a system for replacing corroded coolers from outside the furnace during a fast 'hot' shutdown minimized the impact on furnace operating factor and hearth life. Finally, a corrosion-resistant graphite-protected cooler design significantly improved furnace campaign life, and heralds a more lasting solution to cooler corrosion in PGM furnaces.
- Published
- 2013
5. Redoubling platinum group metal smelting intensity-operational challenges and solutions
- Author
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Hundermark, R., Nelson, L., de Villiers, Bertus, Ndlovu, J., Mokwena, D., Mukumbe, P., Pieterse, B., Seyanund, W., Van Manen, P., Hundermark, R., Nelson, L., de Villiers, Bertus, Ndlovu, J., Mokwena, D., Mukumbe, P., Pieterse, B., Seyanund, W., and Van Manen, P.
- Abstract
The 2003 redoubling in power to 68MW on the Polokwane Smelter furnace represented a significant intensification in platinum group metal (PGM) smelting. Combined with onerous 'green' PGM concentrate smelting requirements, this yielded conditions unusually corrosive to copper coolers and refractories. This presented unexpected operational and design challenges to reliable crucible operation and maintenance. Combined with specific operational control intervention, development of protective coatings has led to the life of water-cooled copper components improving from 9 to 40 months. The furnace matte endwall was extended in 2010 to address accelerated wear of refractories and the potential risk for contact of copper components by superheated matte. An 18 month planned endwall rebuild cycle has been demonstrated (versus catastrophic failure within 9 months). Finally, benefits including lower energy consumption, improved metal recoveries and higher productivity resulting from operational and in-house design developments will be described, that justify "Celebrating the Mega-scale" in PGM smelting.
- Published
- 2014
6. Optimisation of paediatrics computed radiography for full spine curvature measurements using a phantom: a pilot study
- Author
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Sa dos Reis, Claudia, Ndlovu, J., Serrenho, C., Akhtar, I., de Haan, S., Garcia, J., de Linde, D., Thorskog, M., Franco, L., Lanca, C., Hogg, P., Sa dos Reis, Claudia, Ndlovu, J., Serrenho, C., Akhtar, I., de Haan, S., Garcia, J., de Linde, D., Thorskog, M., Franco, L., Lanca, C., and Hogg, P.
- Abstract
Aim: Optimise a set of exposure factors, with the lowest effective dose, to delineate spinal curvature with the modified Cobb method in a full spine using computed radiography (CR) for a 5-year-old paediatric anthropomorphic phantom. Methods: Images were acquired by varying a set of parameters: positions (antero-posterior (AP), posteroanterior (PA) and lateral), kilo-voltage peak (kVp) (66-90), source-to-image distance (SID) (150 to 200cm), broad focus and the use of a grid (grid in/out) to analyse the impact on E and image quality (IQ). IQ was analysed applying two approaches: objective [contrast-to-noise-ratio/(CNR] and perceptual, using 5 observers. Monte-Carlo modelling was used for dose estimation. Cohen’s Kappa coefficient was used to calculate inter-observer-variability. The angle was measured using Cobb’s method on lateral projections under different imaging conditions. Results: PA promoted the lowest effective dose (0.013 mSv) compared to AP (0.048 mSv) and lateral (0.025 mSv). The exposure parameters that allowed lower dose were 200cm SID, 90 kVp, broad focus and grid out for paediatrics using an Agfa CR system. Thirty-seven images were assessed for IQ and thirty-two were classified adequate. Cobb angle measurements varied between 16°±2.9 and 19.9°±0.9. Conclusion: Cobb angle measurements can be performed using the lowest dose with a low contrast-tonoise ratio. The variation on measurements for this was ±2.9° and this is within the range of acceptable clinical error without impact on clinical diagnosis. Further work is recommended on improvement to the sample size and a more robust perceptual IQ assessment protocol for observers.
- Published
- 2014
7. Optimisation of exposure parameters for spinal curvature measurements in paediatric radiography
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Sa dos Reis, Claudia, Ndlovu, J., Serrenho, C., Akhtar, I., de Haan, S., Garcia, J., de Linde, D., Thorskog, M., Franco, L., Hogg, P., Sa dos Reis, Claudia, Ndlovu, J., Serrenho, C., Akhtar, I., de Haan, S., Garcia, J., de Linde, D., Thorskog, M., Franco, L., and Hogg, P.
- Abstract
This review aims to identify strategies to optimise radiography practice using digital technologies, for full spine studies on paediatrics focusing particularly on methods used to diagnose and measure severity of spinal curvatures. The literature search was performed on different databases (PubMed, Google Scholar and ScienceDirect) and relevant websites (e.g., American College of Radiology and International Commission on Radiological Protection) to identify guidelines and recent studies focused on dose optimisation in paediatrics using digital technologies. Plain radiography was identified as the most accurate method. The American College of Radiology (ACR) and European Commission (EC) provided two guidelines that were identified as the most relevant to the subject. The ACR guidelines were updated in 2014; however these guidelines do not provide detailed guidance on technical exposure parameters. The EC guidelines are more complete but are dedicated to screen film systems. Other studies provided reviews on the several exposure parameters that should be included for optimisation, such as tube current, tube voltage and source-to-image distance; however, only explored few of these parameters and not all of them together. One publication explored all parameters together but this was for adults only. Due to lack of literature on exposure parameters for paediatrics, more research is required to guide and harmonise practice.
- Published
- 2014
8. The promise of Africa.
- Author
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Lane A., XXVI International Mineral Processing Congress: IMPC 2012 New Delhi, India 24-Sep-1228-Sep-12 PL-IX Indian Institute of Mineral Engineers and the Indian Institute of Metals, Ndlovu J., Lane A., XXVI International Mineral Processing Congress: IMPC 2012 New Delhi, India 24-Sep-1228-Sep-12 PL-IX Indian Institute of Mineral Engineers and the Indian Institute of Metals, and Ndlovu J.
- Abstract
Africa has large, relatively unexplored mineral deposits, and recent high economic growth rates have improved the political, economic, and infrastructural environments. However, these opportunities are accompanied by significant risks, including resource nationalism, uncertain regulation, corruption, and continuing political instability. Companies can actively manage these risks by creating a sense of shared purpose with the countries and communities that own the resources, using tools such as stakeholder analysis, local narratives, scenario planning, and constituency engagement. A key aspect in Zimbabwe is the socio-economic impact of resource development and related social programmes. Engagement with the local community is vital. A structured analytic tool is suggested which has four steps: develop stakeholder segmentation, understand the most prominent local narratives, understand potential future scenarios, and develop a detailed constituency engagement approach. Other core issues which should be considered include poverty, inequality and unemployment. Two case studies of successful community relations are discussed: Barrick Gold Corporation's Pascua-Lama gold project on the border between Chile and Argentina, and Rio Tinto's Hamersley iron and Argyle diamond mines in the Pilbara region of Western Australia., Africa has large, relatively unexplored mineral deposits, and recent high economic growth rates have improved the political, economic, and infrastructural environments. However, these opportunities are accompanied by significant risks, including resource nationalism, uncertain regulation, corruption, and continuing political instability. Companies can actively manage these risks by creating a sense of shared purpose with the countries and communities that own the resources, using tools such as stakeholder analysis, local narratives, scenario planning, and constituency engagement. A key aspect in Zimbabwe is the socio-economic impact of resource development and related social programmes. Engagement with the local community is vital. A structured analytic tool is suggested which has four steps: develop stakeholder segmentation, understand the most prominent local narratives, understand potential future scenarios, and develop a detailed constituency engagement approach. Other core issues which should be considered include poverty, inequality and unemployment. Two case studies of successful community relations are discussed: Barrick Gold Corporation's Pascua-Lama gold project on the border between Chile and Argentina, and Rio Tinto's Hamersley iron and Argyle diamond mines in the Pilbara region of Western Australia.
- Published
- 2012
9. Process description and short history of Polokwane smelter.
- Author
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Hundermark R., South African Pyrometallurgy 2006 international conference Johannesburg, South Africa 5-8 Mar. 2006, de Villiers B., Ndlovu J., Hundermark R., South African Pyrometallurgy 2006 international conference Johannesburg, South Africa 5-8 Mar. 2006, de Villiers B., and Ndlovu J.
- Abstract
The Polokwane smelter is the only platinum-producing smelter in the area. Wet concentrate is received from various concentrators along the Eastern Bushveld Complex with 60% from the UG2 and 40% from the Merensky reef, varying in grade from 35 g/t Pt to 110 g/t Pt, from which Pt-rich Cu-Ni matte is produced. A brief description is given of the process operation, which includes concentrate receiving and flash drying, the furnace, furnace refractory and cooling system, matte handling and crushing, and water management., The Polokwane smelter is the only platinum-producing smelter in the area. Wet concentrate is received from various concentrators along the Eastern Bushveld Complex with 60% from the UG2 and 40% from the Merensky reef, varying in grade from 35 g/t Pt to 110 g/t Pt, from which Pt-rich Cu-Ni matte is produced. A brief description is given of the process operation, which includes concentrate receiving and flash drying, the furnace, furnace refractory and cooling system, matte handling and crushing, and water management.
- Published
- 2006
10. Operational readiness: a value proposition.
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Ndlovu J., Nickel and cobalt 2005: challenges in extraction and production, Calgary, Alberta, 21-24 Aug. 2005, Amadi-Echendu J.E., Nelson L.R., Stober F., Ndlovu J., Nickel and cobalt 2005: challenges in extraction and production, Calgary, Alberta, 21-24 Aug. 2005, Amadi-Echendu J.E., Nelson L.R., and Stober F.
- Abstract
The Polokwane smelter complex, Bushveld, South Africa, uses a single 68 MW high-intensity six-in-line furnace to smelt a planned 650 000 t/a dry concentrate to produce a PGM-containing matte. Considerable attention was paid to project development and implementation of the design, engineering, construction and commissioning stages. A dedicated multi- disciplinary operational readiness and support team was established comprising an owners' team and specialists from the furnace designer to effect a safe and rapid ramp-up to the design smelter capacity. The team was responsible for the development of the business operations model comprising the implementation of systems of work, and also provided invaluable coaching and training on metallurgical and engineering aspects of the high-intensity operation. Other aspects included a focus on safe operation, protection of the asset and maximising its utilisation in a sustainable manner., The Polokwane smelter complex, Bushveld, South Africa, uses a single 68 MW high-intensity six-in-line furnace to smelt a planned 650 000 t/a dry concentrate to produce a PGM-containing matte. Considerable attention was paid to project development and implementation of the design, engineering, construction and commissioning stages. A dedicated multi- disciplinary operational readiness and support team was established comprising an owners' team and specialists from the furnace designer to effect a safe and rapid ramp-up to the design smelter capacity. The team was responsible for the development of the business operations model comprising the implementation of systems of work, and also provided invaluable coaching and training on metallurgical and engineering aspects of the high-intensity operation. Other aspects included a focus on safe operation, protection of the asset and maximising its utilisation in a sustainable manner.
- Published
- 2005
11. Role of technical innovation on production delivery at the Polokwane smelter.
- Author
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Nelson L.R., Nickel and cobalt 2005: challenges in extraction and production, Calgary, Alberta, 21-24 Aug. 2005, de Villiers L.P.S., Ndlovu J., Stober F., Wanblad D., Nelson L.R., Nickel and cobalt 2005: challenges in extraction and production, Calgary, Alberta, 21-24 Aug. 2005, de Villiers L.P.S., Ndlovu J., Stober F., and Wanblad D.
- Abstract
The single six-in-line furnace of the Polokwane smelter in South Africa is the largest installed high-intensity furnace for platinum group metal sulphide smelting in the world, with a throughput of 650 000 t/a dry concentrate at a design power input of 68 MW. The process requirements included the need to achieve high-intensity smelting of a high proportion of UG2 feed containing up to 4% Cr2O3. Operation at higher slag Cr2O3 levels leads directly to higher bath temperatures and also increases the potential for undesirable precipitation of solid spinel phases at the matte-slag interface or as build-up on the hearth. Selection of adequate transformer capacity was needed to allow operation at deep electrode immersion and to operate at high hearth power density to substantially prevent build-up of spinel on the hearth. Adoption of water-cooled Cu waffle coolers in the slag zone allows sustainable operation at the high resulting sidewall heat fluxes and reduced lime addition as a basic slag conditioner. Very low slag PGM losses are also achieved., The single six-in-line furnace of the Polokwane smelter in South Africa is the largest installed high-intensity furnace for platinum group metal sulphide smelting in the world, with a throughput of 650 000 t/a dry concentrate at a design power input of 68 MW. The process requirements included the need to achieve high-intensity smelting of a high proportion of UG2 feed containing up to 4% Cr2O3. Operation at higher slag Cr2O3 levels leads directly to higher bath temperatures and also increases the potential for undesirable precipitation of solid spinel phases at the matte-slag interface or as build-up on the hearth. Selection of adequate transformer capacity was needed to allow operation at deep electrode immersion and to operate at high hearth power density to substantially prevent build-up of spinel on the hearth. Adoption of water-cooled Cu waffle coolers in the slag zone allows sustainable operation at the high resulting sidewall heat fluxes and reduced lime addition as a basic slag conditioner. Very low slag PGM losses are also achieved.
- Published
- 2005
12. Nutritional Analysis of the South African Wild Vegetable Corchorus olitorius L.
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Ndlovu, J., primary and Afolayan, A.J., additional
- Published
- 2008
- Full Text
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13. Elemental analysis of Fadogia ancylantha leaves used as a nutraceutical in Mashonaland West Province, Zimbabwe.
- Author
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Muzenda T, Shoko R, Chimwanda P, and Ndlovu J
- Abstract
In this study, the concentrations of the essential elements to the human body N, K, Mg, P, Ca, Fe, Mn, and Zn of the fermented and non-fermented Fadogia ancylantha leaf samples were analysed to assess their nutritional value in two different areas in Zimbabwe: Mhangura (Mashonaland West, Province) and Alaska (Mashonaland West Province). Atomic absorption spectroscopy and ultraviolet spectrophotometry techniques were used to measure the concentrations of the minerals. The concentrations of manganese were significantly high ( p < 0.05) in non-fermented treatments, with Mhangura samples having 0.447 mg/g and Alaska samples having 0.453 mg/g. Iron was high in fermented samples with Mhangura samples having 0.245 mg/g and Alaska samples having 0.270 mg/g. The concentrations of manganese and iron in Fadogia ancylantha can be used to supplement the recommended daily doses in pregnant, menstruating, and lactating women. The study, therefore, recommends that Fadogia ancylantha be used as a nutraceutical for the supplementation of iron and manganese., Competing Interests: Conflict of interest: Authors state no conflict of interest., (© 2023 the author(s), published by De Gruyter.)
- Published
- 2023
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14. Construction and analysis of protein-protein interaction networks based on nuclear proteomics data of the desiccation-tolerant Xerophyta schlechteri leaves subjected to dehydration stress.
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Shoko R, Magogo B, Pullen J, Mudziwapasi R, and Ndlovu J
- Abstract
In order to understand the mechanism of desiccation tolerance in Xerophyta schlechteri , we carried out an in silico study to identify hub proteins and functional modules in the nuclear proteome of the leaves. Protein-protein interaction networks were constructed and analyzed from proteome data obtained from Abdalla and Rafudeen. We constructed networks in Cytoscape using the GeneMania software and analyzed them using a Network Analyzer. Functional enrichment analysis of key proteins in the respective networks was done using GeneMania network enrichment analysis, and GO (Gene Ontology) terms were summarized using REViGO. Also, community analysis of differentially expressed proteins was conducted using the Cytoscape Apps, GeneMania and ClusterMaker. Functional modules associated with the communities were identified using an online tool, ShinyGO. We identified HSP 70-2 as the super-hub protein among the up-regulated proteins. On the other hand, 40S ribosomal protein S2-3 (a protein added by GeneMANIA) was identified as a super-hub protein associated with the down-regulated proteins. For up-regulated proteins, the enriched biological process terms were those associated with chromatin organization and negative regulation of transcription. In the down-regulated protein-set, terms associated with protein synthesis were significantly enriched. Community analysis identified three functional modules that can be categorized as chromatin organization, anti-oxidant activity and metabolic processes., Competing Interests: No potential conflict of interest was reported by the authors., (© 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)
- Published
- 2023
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15. In Silico Study of Cucurbita maxima Compounds as Potential Therapeutics Against Schistosomiasis.
- Author
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Mtemeli FL, Shoko R, Ndlovu J, and Mugumbate G
- Abstract
Schistosomiasis, a disease usually related to poverty and poor sanitation, affects more than 200 million people worldwide. Since the 1970s, the medical sector has depended on a single drug, praziquantel, for the treatment of the disease. The emerging evidence of resistance of the Schistosoma parasite to praziquantel and the drug's inefficacy against juvenile stages of the parasite makes the need to find alternative drugs an urgent matter. In this study, we explored the inhibition potential of compounds from Cucurbita maxima using molecular docking studies on Schistosoma mansoni purine nucleoside phosphorylase ( Sm PNP) and Schistosoma haematobium 28-kDa glutathione S-transferase ( Sh 28kDaGST). Following molecular docking studies and analysis of the active sites, the primary amino acids that were observed and shown to be involved in the Sm PNP-ligand interaction are CYS 33, ARG 86, HIS 88, TYR 90, ALA 118, ALA 119, PRO 200, TYR 202, GLU 203, VAL 219, MET 221, THR 244, ASN 245, PRO 257 and HIS 259. For the Sh2 8dKa-ligand interaction, the primary amino acids were PHE 11, ARG 16, TRP 41, LEU 53, GLU 70 and SER 71. Momordicoside I aglycone binds to Sm PNP with the lowest binding affinity of -7.9 kcal/mol by pi sigma bond interactions with HIS 88. Balsaminoside B binds to Sh 28kDaGST with a binding affinity of -7.6 kcal/mol by hydrogen bond interaction with TRP 41, LEU 53 and SER 71. Pharmacokinetic studies showed favourable drug-like properties for the 10 compounds that exhibited the lowest binding energies. Therefore, we propose that bioactive compounds from C. maxima be considered as potential novel drug hits in the treatment of schistosomiasis., Competing Interests: Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2022.)
- Published
- 2022
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16. Why Do Patients with Mental Disorders Default Treatment? A Qualitative Enquiry in Rural Kwazulu-Natal, South Africa.
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Mokwena KE and Ndlovu J
- Abstract
Although treatment default by psychiatric patients or mental health care users is a global challenge, this behavior is reported to be higher in South Africa. The Manguzi District Hospital in rural Kwa-Zulu Natal Province, South Africa, experiences high rates of treatment default by psychiatric patients. The objective of this study was to determine the reasons for treatment defaulting at Manguzi Hospital, KwaZulu-Natal Province, South Africa. An explorative qualitative design, using in-depth interviews, was conducted with mental health care users who had defaulted out-patient psychiatric treatment. Twenty-one mental health care users were interviewed before data saturation was reached. Nvivo version 11 was used to analyze the qualitative data. Major themes that emerged confirmed that social factors are key contributions to treatment defaulting, and these include denial of the mental disorders; belief that they are cured; lack of, or disintegration of social support; preference for traditional medicine; and flaws in the health care system. Social determinants of treatment outcomes for mental disorders require tailor-made support systems for patients in these rural communities, which include increase in health literacy and attention to the cultural understanding of mental disorders.
- Published
- 2021
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17. Human usage in the native range may determine future genetic structure of an invasion: insights from Acacia pycnantha.
- Author
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Le Roux JJ, Richardson DM, Wilson JR, and Ndlovu J
- Subjects
- Australia, Bayes Theorem, Cluster Analysis, DNA, Plant genetics, Forestry, Genotype, Population Dynamics, Sequence Analysis, DNA, South Africa, Acacia genetics, Genetic Variation, Genetics, Population, Introduced Species
- Abstract
Background: The influence of introduction history and post-introduction dynamics on genetic diversity and structure has been a major research focus in invasion biology. However, genetic diversity and structure in the invasive range can also be affected by human-mediated processes in the native range prior to species introductions, an aspect often neglected in invasion biology. Here we aim to trace the native provenance of the invasive tree Acacia pycnantha by comparing the genetic diversity and structure between populations in the native Australian range and the invasive range in South Africa. This approach also allowed us to explore how human actions altered genetic structure before and after the introduction of A. pycnantha into South Africa. We hypothesized that extensive movement and replanting in A. pycnantha's Australian range prior to its introduction to South Africa might result in highly admixed genotypes in the introduced range, comparable genetic diversity in both ranges, and therefore preclude an accurate determination of native provenance(s) of invasive populations., Results: In the native range Bayesian assignment tests identified three genetic clusters with substantial admixture and could not clearly differentiate previously identified genetic entities, corroborating admixture as a result of replantings within Australia. Assignment tests that included invasive populations from South Africa indicated similar levels of admixture compared to Australian populations and a lack of genetic structure. Invasive populations of A. pycnantha in South Africa are as genetically diverse as native populations, and could not be assigned to particular native range regions., Conclusions: Our results indicate that the genetic structure of A. pycnantha in Australia has been greatly altered through various planting initiatives. Specifically, there is little geographic structure and high levels of admixture. While numerous introduction history scenarios may explain the levels of admixture observed in South Africa, planting records of A. pycnantha in Australia suggest that populations were probably already admixed before propagules were introduced to South Africa. These findings have important implications for the management of invasive A. pycnantha populations in South Africa, especially for classical biological control, and more broadly, for studies that aim to understand the evolutionary dynamics of the invasion process.
- Published
- 2013
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18. Elucidating the native sources of an invasive tree species, Acacia pycnantha, reveals unexpected native range diversity and structure.
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Ndlovu J, Richardson DM, Wilson JR, O'Leary M, and Le Roux JJ
- Subjects
- Australia, Base Sequence, Bayes Theorem, Cell Nucleus genetics, Ecotype, Genome, Plastid genetics, Geography, Haplotypes, Acacia genetics, Genetic Variation, Introduced Species, Trees genetics
- Abstract
Background and Aims: Understanding the introduction history of invasive plant species is important for their management and identifying effective host-specific biological control agents. However, uncertain taxonomy, intra- and interspecific hybridization, and cryptic speciation may obscure introduction histories, making it difficult to identify native regions to explore for host-specific agents. The overall aim of this study was to identify the native source populations of Acacia pycnantha, a tree native to south-eastern Australia and invasive in South Africa, Western Australia and Portugal. Using a phylogeographical approach also allowed an exploration of the historical processes that have shaped the genetic structure of A. pycnantha in its native range., Methods: Nuclear (nDNA) and plastid DNA sequence data were used in network and tree-building analyses to reconstruct phylogeographical relationships between native and invasive A. pycnantha populations. In addition, mismatch distributions, relative rates and Bayesian analyses were used to infer recent demographic processes and timing of events in Australia that led to population structure and diversification., Key Results: The plastid network indicated that Australian populations of A. pycnantha are geographically structured into two informally recognized lineages, the wetland and dryland forms, whereas the nuclear phylogeny showed little geographical structure between these two forms. Moreover, the dryland form of A. pycnantha showed close genetic similarity to the wetland form based on nDNA sequence data. Hybrid zones may explain these findings, supported here by incongruent phylogenetic placement of some of these taxa between nuclear and plastid genealogies., Conclusions: It is hypothesized that habitat fragmentation due to cycles of aridity inter-dispersed with periods of abundant rainfall during the Pleistocene (approx. 100 kya) probably gave rise to native dryland and wetland forms of A. pycnantha. Although the different lineages were confined to different ecological regions, we also found evidence for intraspecific hybridization in Victoria. The invasive populations in Portugal and South Africa represent wetland forms, whereas some South African populations resemble the Victorian dryland form. The success of the biological control programme for A. pycnantha in South Africa may therefore be attributed to the fact that the gall-forming wasp Trichilogaster signiventris was sourced from South Australian populations, which closely match most of the invasive populations in South Africa.
- Published
- 2013
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19. Methods to reduce social desirability bias in sex surveys in low-development settings: experience in Zimbabwe.
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Gregson S, Zhuwau T, Ndlovu J, and Nyamukapa CA
- Subjects
- Adolescent, Adult, Confidentiality, Female, Humans, Male, Middle Aged, Regression Analysis, Sexual Partners, Zimbabwe epidemiology, Data Collection methods, Developing Countries statistics & numerical data, Prejudice, Sexual Behavior statistics & numerical data, Social Desirability
- Abstract
Background: Social desirability bias hampers measurement of risk behavior for acquiring STDs and evaluation of control interventions. More confidential data collection methods reduce this bias in Western countries but generally require technology not available in less developed settings. GOAL The goal of this report was to describe and evaluate an informal, confidential, low-technology method-Informal Confidential Voting Interviews (ICVIs)-for collecting sexual behavior data in less developed settings., Study Design: Reports of multiple sex partners by sexually active, basic-literate, population-based survey participants in rural Zimbabwe randomly assigned to ICVIs and face-to-face interviews (FTFIs) were compared., Results: Ninety-two percent of respondents (n = 7,823) were sufficiently literate for ICVIs. Error rates were low but higher than in FTFIs. More male and female ICVI respondents interviewed reported multiple current sex partners (OR = 1.33 and 5.24, respectively) and multiple partners in the past month (OR = 1.71 and 2.92) and the past year (OR = 1.35 and 1.97)., Conclusion: The ICVI method appears to reduce bias but requires further evaluation to assess viability and effect in alternative settings.
- Published
- 2002
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20. [Lack of physicians gives Ndlovu total responsibility. Interview by Inger Jalakas].
- Author
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Ndlovu JI
- Subjects
- Adult, Child, Female, HIV Infections epidemiology, HIV Infections prevention & control, Humans, Malaria epidemiology, Malaria prevention & control, Male, Physicians supply & distribution, Role, Zimbabwe epidemiology, Morbidity, Mortality, Nurses, Male
- Published
- 1997
21. Recent upturn in mortality in rural Zimbabwe: evidence for an early demographic impact of HIV-1 infection?
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Gregson S, Anderson RM, Ndlovu J, Zhuwau T, and Chandiwana SK
- Subjects
- Adolescent, Adult, Age Factors, Death Certificates, Female, Humans, Infant, Infant Mortality, Infant, Newborn, Male, Middle Aged, Mortality trends, Parents, Pregnancy, Pregnancy Complications, Infectious, Prevalence, Rural Population, Sex Factors, Sexual Behavior, Survival Analysis, Zimbabwe epidemiology, Demography, Disease Outbreaks, HIV Infections mortality, HIV-1
- Abstract
Objectives: To describe recent mortality trends in rural Zimbabwe and to assess the impact of HIV-1 infection., Method: Comparative, cross-sectional, retrospective, demographic survey with 1-year follow-up. Parallel HIV-1 surveillance. Comparison of results with 1992 national census and vital registration data and results from mathematical model-based population projections., Setting and Participants: Residents of 929 (745 revisited in 1995) households in two rural areas of Manicaland Province, Zimbabwe, with contrasting HIV-1 prevalence: Honde and Rusitu valleys. Subjects gave information on parental survival for 2320 resident children. Female residents aged 13-49 years (n = 1237) provided information on birth histories and child survival. Consenting women attending local antenatal clinics (n = 487) provided blood samples for HIV-1 screening and demographic information., Main Outcome Measures: HIV-1 prevalence in pregnant women; per capita death registration rates; incidence of parental death for children aged under 8 years; infant mortality and age-specific death probabilities., Results: HIV-1 prevalence was high in each study area. Death registration and age-specific mortality have begun to rise. The largest increases were seen in the area of higher HIV-1 prevalence (Honde) and among younger adults, particularly men. Incidence of parental death was observed to be rising. Increases in registered deaths were concentrated among HIV-1-associated causes., Conclusions: The observed increases in mortality by age, sex and cause of death were consistent with those expected early in a severe HIV-1 epidemic, on the basis of mathematical model projections and observations elsewhere in Africa. Further rises in mortality, particularly among women and young children, and consequent increases in orphanhood, are to be expected in rural areas of Zimbabwe.
- Published
- 1997
- Full Text
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22. Factual knowledge about AIDS and dating practices among high school students from selected schools.
- Author
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Nyachuru-Sihlangu RH and Ndlovu J
- Subjects
- Acquired Immunodeficiency Syndrome transmission, Adolescent, Female, Health Education standards, Humans, Male, Models, Psychological, Psychology, Adolescent, Sexual Partners, Zimbabwe, Acquired Immunodeficiency Syndrome prevention & control, Health Knowledge, Attitudes, Practice, Students psychology
- Abstract
Following various educational strategies by governmental and non-governmental organisations to educate youths and school teachers about HIV infection and prevention, this KABP survey was one attempt to evaluate the results. The study sample of 478 high school students was drawn from four randomly selected schools in Mashonaland and Matabeleland including high and low density, government and mission co-educational schools. The sample was randomly selected and stratified to represent sex and grade level. The KABP self administered questionnaire was used. The paper analyses the relationship between the knowledge and dating patterns. Generally, respondents demonstrated a 50pc to 80pc accuracy of factual knowledge. Of the 66pc Forms I through IV pupils who dated, 30pc preferred only sexually involved relationships and a small number considered the possibility of HIV/AIDS infection. A theoretically based tripartite coalition involving the school, the family health care services for education, guidance and support to promote responsible behaviour throughout childhood was suggested.
- Published
- 1992
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