Challenges in topside ionospheric modelling over South Africa

This thesis creates a basic framework and provides the information necessary to create a more accurate description of the topside ionosphere in terms of the altitude variation of the electron density (Ne) over the South African region. The detailed overview of various topside ionospheric modelling techniques, with specific emphasis on their implications for the efforts to model the South African topside, provides a starting point towards achieving the goals. The novelty of the thesis lies in the investigation of the applicabilityof three different techniques to model the South African topside ionosphere: (1) The possibility of using Artificial Neural Network (ANN) techniques for empirical modelling of the topside ionosphere based on the available, however irregularly sampled, topside sounder measurements. The goal of this model was to test the ability of ANN techniques to capture the complex relationships between the various ionospheric variables using irregularly distributed measurements. While this technique is promising, the method did not show significant improvement over the International Reference Ionosphere (IRI) model results when compared with the actual measurements. (2) Application of the diffusive equilibrium theory. Although based on sound physics foundations, the method only operates on a generalised level leading to results that are not necessarily unique. Furthermore, the approach relies on many ionospheric variables as inputs which are derived from other models whose accuracy is not verified. (3) Attempts to complement the standard functional techniques, (Chapman, Epstein, Exponential and Parabolic), with Global Positioning System (GPS) and ionosonde measurements in an effort to provide deeper insights into the actual conditions within the ionosphere. The vertical Ne distribution is reconstructed by linking together the different aspects of the constituent ions and their transition height by considering how they influence the shape of the profile. While this approach has not been tested against actual measurements, results show that the method could be potentially useful for topside ionospheric studies. Due to the limitations of each technique reviewed, this thesis observes that the employment of an approach that incorporates both theoretical onsiderations and empirical aspects has the potential to lead to a more accurate characterisation of the topside ionospheric behaviour, and resulting in improved models in terms of reliability and forecasting ability. The point is made that a topside sounder mission for South Africa would provide the required measured topside ionospheric data and answer the many science questions that this region poses as well as solving a number of the limitations set out in this thesis

Particle precipitation effects on the South African ionosphere

Particle precipitation involves the injection of energetic particles into the ionosphere which could increase the ionisation and conductivity of the upper atmosphere. The goal of this study was to examine the ionospheric response and changes due to particle precipitation in the region over South Africa, using a combination of groundbased and satellite instruments. Particle precipitation events were identified from satellite particle flux measurements of the Defence Meteorological Satellite Program (DMSP). Comprehensive studies were done on the events of 5 April, 2000 and 7 October, 2000. Analysis of the data from the satellite instruments indicates that no particle precipitation was observed over the South African region during these events and that it is unlikely to occur during other such events. To validate the data, methods and tools used in this study, precipitation in the South Atlantic anomaly (SAA) region is used. Satellite ion density measurements revealed that strong density enhancements occurred over the SAA region at satellite altitudes during the precipitation events, but this did not occur in the South African region. The measurements also revealed how the ionisation enhancements in the SAA region correlated with geomagnetic and solar activities. Particle precipitation and convective electric fields are two major magnetospheric energy sources to the upper atmosphere in the auroral and the SAA regions. These increase dramatically during geomagnetic storms and can disturb thermospheric circulation in the atmosphere and alter the rates of production and recombination of the ionised species. Ionosonde observations at Grahamstown, South Africa (33.30S, 26.50E), provided the data to build a picture of the response of the ionosphere over the South African region to particle precipitation during the precipitation events. This analysis showed that, within the confines of the available data, no direct connections between particle precipitation events and disturbances in the ionosphere over this region were revealed

Sign bilingual education practice as a strategy for inclusion of deaf children in Zimbabwe

Literature indicates that inclusion of deaf children in mainstream schools is a complex process and that it has eluded many deaf practitioners and education systems for a very long time. New research is, however, pointing to the potential for sign bilingual education as a viable strategy for improving inclusivity of deaf children in mainstream settings. The purpose of the current study was, therefore, to interrogate how sign bilingual education was used as a strategy for inclusion of deaf children in Zimbabwe. The study was premised on Cummins Linguistic Interdependence theory and adopted the mixed methods paradigm which is informed by the philosophy of pragmatism. The sequential explanatory design was utilized and participants were selected using random sampling for the quantitative phase and purposive sampling for the qualitative phase. Questionnaires, face-to-face and focus group interviews (FGIs) were used to elicit data from participants. These data were presented on SPSS generated graphs and analysed using frequency counts, percentages and inferential statistics based on the analysis of Spearman’s Rank Order Correlation Coefficient at 5% level of significance (p=0.005). Consequently, qualitative data were presented as summaries and direct quotes and analysed using thematic and content analyses. The results revealed that the conception, hence the practice of sign bilingual was limited and had challenges, but that it had the greatest potential benefits for inclusion of deaf children in mainstream schools in Zimbabwe. On these bases, the study recommended training of teachers and parents as well as staff development of the teachers and school administrators. The study also recommended adoption of best practices such as early exposure, co-teaching, co-enrolment, multi-stakeholder participation, turning special schools into resource centers for sign bilingual education and inclusion and embracing ICT. A further recommendation pointed to review of policy in line with best practices. Ultimately, the study proposed a framework for sign bilingual education as a strategy for inclusion of deaf children in mainstream schools in Zimbabwe.Inclusive EducationPh. D. (Inclusive Education

Total electron content derived from global positioning system during solar maximum of 2012-2013 over the eastern part of the African sector

This work presents results of diurnal, seasonal and latitudinal variations of vertical Total Electron Content (TECv) derived from GPS receivers at four locations, [Dodoma (6.19oS, 35.75oE), Mzuzu (11.43oS, 34.01oE), Zomba (15.38oS, 35.33oE) and Tete (16.15oS, 33.58oE)] during the solar maximum period of 2012 – 2013. The receivers are located directly below the EIA and at approximately the same longitude, ~ (33 – 3 oE) within the eastern part of the African sector. Diurnal and latitudinal variations of TECv are presented for an average of the five (5) quietest days of each of the four seasons: March equinox, June solstice, September equinox and December solstice; for the seasonal variations all months in a year were considered. Results showed that TECv is characterized by consistent minimum diurnal variations during presunrise hours, rises steeply during the sunrise period to the maximum peak during the daytime, followed by a decrease to a minimum during nighttime. The values of TECv from all stations used and for both years (2012 and 2013) showed semiannual variations. Our study also showed that, the day maximum value of the TECv decreased significantly with the increase in latitude.Keywords: Global Positioning System, Total Electron Conten

Quantifying the azimuthal plasmaspheric density structure and dynamics inferred from IMAGE EUV

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95221/1/jgra22185.pd

Devising effective strategies and policies for CSA: insights from a panel of global policy experts

In this section, we present the results of a consultation with a panel of leading thinkers on agricultural and climate change policy. We interviewed these experts using a set of questions based on the main findings, conclusions, insights and questions that emerged from our set of case studies and conceptual papers. This section is divided into four parts, each focusing on a set of questions relating to the conclusions that emerged from the case study and conceptual chapters. (i) Focus on changes in production systems as adaptation: priorities and policy actions; (ii) Incorporating climate change into agricultural research and extension; (iii) Taking a close look at national policies affecting risk management: index insurance, safety nets and input subsidies and (iv) Priorities for the future and summary of main points. Overall, there is a fairly high level of agreement amongst the panel members in responding to most of the interview questions, although with some difference in emphasis or applications. However there are also some differences of opinion that emerge from their responses. In this chapter, we discuss the main points made on each of the issues addressed, highlighting the areas of agreement, as well as differences. (Résumé d'auteur

Listeria monocytogenes at the food–human interface : a review of risk factors influencing transmission and consumer exposure in Africa

DATA AVAILABILITY STATEMENT: Data sharing not applicable - no new data generated.In African public health systems, Listeria monocytogenes is a pathogen of relatively low priority. Yet, the biggest listeriosis outbreak recorded to date occurred in Africa in 2018. This review highlights the factors that potentially impact L. monocytogenes transmission risks through African food value chains (FVCs). With the high rate of urbanisation, African FVCs have become spatially longer yet still informal. At the same time, dietary diversifications have resulted in increased consumption of processed ready-to-eat (RTE) meat, poultry, fishery and dairy products typically associated with a higher risk of L. monocytogenes consumer exposure. With frequent cold chain challenges, the potential of L. monocytogenes growth in contaminated RTE foods can further amplify consumer exposure risks. Moreover, the high prevalence of untreated HIV infections, endemic anaemia, high fertility rate and a gradually increasing proportion of elderly persons expands the fraction of listeriosis-susceptible groups among African populations. With already warmer tropical conditions, the projected climate change-induced increases in ambient temperatures are likely to exacerbate listeriosis risks in Africa. As precautionary approaches, African countries should implement systems for the detection and reporting of listeriosis cases and food safety regulations that provide L. monocytogenes standards and limits in high-risk RTE foods.The Australia-Africa Universities Network (AAUN)–Partnership Research and Development Fund 2018.https://ifst.onlinelibrary.wiley.com/journal/13652621Consumer ScienceFood ScienceSDG-02:Zero HungerSDG-03:Good heatlh and well-bein

Natural multi-occurrence of mycotoxins in rice from Niger State, Nigeria

Twenty-one rice samples from field (ten), store (six) and market (five) from the traditional rice-growing areas of Niger State, Nigeria were analysed for aflatoxins (AFs), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), fumonisin B1 (FB1) and B2 (FB2), and patulin (PAT) by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) respectively. T-2 toxin was determined using TLC only. AFs were detected in all samples, at total AF concentrations of 28–372 μg/kg. OTA was found in 66.7% of the samples, also at high concentrations (134–341 μg/kg) that have to be considered as critical levels in aspects of nephrotoxicity. ZEA (53.4%), DON (23.8), FB1 (14.3%) and FB2 (4.8%) were also found in rice, although at relatively low levels. T-2 toxin was qualitatively detected by TLC in only one sample. Co-contamination with AFs, OTA, and ZEA was very common, and up to five mycotoxins were detected in a single sample. The high AF and OTA levels as found in rice in this study are regarded as unsafe, and multi-occurrences of mycotoxins in the rice samples with possible additive or synergistic toxic effects in consumers raise concern with respect to public health

MasakhaNEWS:News Topic Classification for African languages

African languages are severely under-represented in NLP research due to lack of datasets covering several NLP tasks. While there are individual language specific datasets that are being expanded to different tasks, only a handful of NLP tasks (e.g. named entity recognition and machine translation) have standardized benchmark datasets covering several geographical and typologically-diverse African languages. In this paper, we develop MasakhaNEWS -- a new benchmark dataset for news topic classification covering 16 languages widely spoken in Africa. We provide an evaluation of baseline models by training classical machine learning models and fine-tuning several language models. Furthermore, we explore several alternatives to full fine-tuning of language models that are better suited for zero-shot and few-shot learning such as cross-lingual parameter-efficient fine-tuning (like MAD-X), pattern exploiting training (PET), prompting language models (like ChatGPT), and prompt-free sentence transformer fine-tuning (SetFit and Cohere Embedding API). Our evaluation in zero-shot setting shows the potential of prompting ChatGPT for news topic classification in low-resource African languages, achieving an average performance of 70 F1 points without leveraging additional supervision like MAD-X. In few-shot setting, we show that with as little as 10 examples per label, we achieved more than 90\% (i.e. 86.0 F1 points) of the performance of full supervised training (92.6 F1 points) leveraging the PET approach

Independent and combined effects of improved water, sanitation, and hygiene, and improved complementary feeding, on child stunting and anaemia in rural Zimbabwe: a cluster-randomised trial.

BACKGROUND: Child stunting reduces survival and impairs neurodevelopment. We tested the independent and combined effects of improved water, sanitation, and hygiene (WASH), and improved infant and young child feeding (IYCF) on stunting and anaemia in in Zimbabwe. METHODS: We did a cluster-randomised, community-based, 2 × 2 factorial trial in two rural districts in Zimbabwe. Clusters were defined as the catchment area of between one and four village health workers employed by the Zimbabwe Ministry of Health and Child Care. Women were eligible for inclusion if they permanently lived in clusters and were confirmed pregnant. Clusters were randomly assigned (1:1:1:1) to standard of care (52 clusters), IYCF (20 g of a small-quantity lipid-based nutrient supplement per day from age 6 to 18 months plus complementary feeding counselling; 53 clusters), WASH (construction of a ventilated improved pit latrine, provision of two handwashing stations, liquid soap, chlorine, and play space plus hygiene counselling; 53 clusters), or IYCF plus WASH (53 clusters). A constrained randomisation technique was used to achieve balance across the groups for 14 variables related to geography, demography, water access, and community-level sanitation coverage. Masking of participants and fieldworkers was not possible. The primary outcomes were infant length-for-age Z score and haemoglobin concentrations at 18 months of age among children born to mothers who were HIV negative during pregnancy. These outcomes were analysed in the intention-to-treat population. We estimated the effects of the interventions by comparing the two IYCF groups with the two non-IYCF groups and the two WASH groups with the two non-WASH groups, except for outcomes that had an important statistical interaction between the interventions. This trial is registered with ClinicalTrials.gov, number NCT01824940. FINDINGS: Between Nov 22, 2012, and March 27, 2015, 5280 pregnant women were enrolled from 211 clusters. 3686 children born to HIV-negative mothers were assessed at age 18 months (884 in the standard of care group from 52 clusters, 893 in the IYCF group from 53 clusters, 918 in the WASH group from 53 clusters, and 991 in the IYCF plus WASH group from 51 clusters). In the IYCF intervention groups, the mean length-for-age Z score was 0·16 (95% CI 0·08-0·23) higher and the mean haemoglobin concentration was 2·03 g/L (1·28-2·79) higher than those in the non-IYCF intervention groups. The IYCF intervention reduced the number of stunted children from 620 (35%) of 1792 to 514 (27%) of 1879, and the number of children with anaemia from 245 (13·9%) of 1759 to 193 (10·5%) of 1845. The WASH intervention had no effect on either primary outcome. Neither intervention reduced the prevalence of diarrhoea at 12 or 18 months. No trial-related serious adverse events, and only three trial-related adverse events, were reported. INTERPRETATION: Household-level elementary WASH interventions implemented in rural areas in low-income countries are unlikely to reduce stunting or anaemia and might not reduce diarrhoea. Implementation of these WASH interventions in combination with IYCF interventions is unlikely to reduce stunting or anaemia more than implementation of IYCF alone. FUNDING: Bill & Melinda Gates Foundation, UK Department for International Development, Wellcome Trust, Swiss Development Cooperation, UNICEF, and US National Institutes of Health.The SHINE trial is funded by the Bill & Melinda Gates Foundation (OPP1021542 and OPP113707); UK Department for International Development; Wellcome Trust, UK (093768/Z/10/Z, 108065/Z/15/Z and 203905/Z/16/Z); Swiss Agency for Development and Cooperation; US National Institutes of Health (2R01HD060338-06); and UNICEF (PCA-2017-0002)