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Endoscopic capacity in West Africa
摘要： Background: Levels of endoscopic demand and capacity in West Africa are unclear. Objectives: This paper aims to: 1. describe the current labor and endoscopic capacity, 2. quantify the impact of a mixed-methods endoscopy course on healthcare professionals in West Africa, and 3. quantify the types of diagnoses encountered. Methods: In a three-day course, healthcare professionals were surveyed on endoscopic resources and capacity and were taught through active observation of live cases, case discussion, simulator experience and didactics. Before and after didactics, multiple-choice exams as well as questionnaires were administered to assess for course efficacy. Also, a case series of 23 patients needing upper GI endoscopy was done. Results: In surveying physicians, less than half had resources to perform an EGD and none could perform an ERCP, while waiting time for emergency endoscopy in urban populations was at least one day. In assessing improvement in medical knowledge among participants after didactics, objective data paired with subjective responses was more useful than either alone. Of 23 patients who received endoscopy, 7 required endoscopic intervention with 6 having gastric or esophageal varices. Currently the endoscopic capacity in West Africa is not sufficient. A formal GI course with simulation and didactics improves gastrointestinal knowledge amongst participants.
关键词： endoscopic demand,training course,West Africa,Endoscopic capacity
更新于2025-09-23 15:23:52
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Modelling the impact of market imperfections on farm household investment in stand-alone solar PV systems
摘要： Access to electricity in rural Sub-Saharan Africa, where livelihoods are predominantly based on small scale farming, is significantly low. Extending centralised national electricity grids to these rural areas faces significant technical and financial constraints. As a result, many see household-financed decentralised technologies such as small standalone solar photovoltaic (PV) systems as being important for achieving greater electricity access. However, rural farm households typically face a range of market imperfections including lack of access to credit, investment irreversibility (or absence of second-hand markets) and farm production/income risk which act as barriers to their ability and/or willingness to invest. This paper examines how these market imperfections impact on the adoption of standalone solar PV systems for small scale farm households in Uganda. We consider how temporary or permanent these barriers to adoption are when farm production/income is uncertain. We do so by using a dynamic programming model which captures household investment in small scale solar PV systems where significant positive benefits arise through assumed improved farm productivity or income effects, while allowing for credit constraints, investment irreversibility and income risk. Although strong positive incentives exist in the model to adopt a solar PV system, the results show that adoption rates are substantially lower for credit constrained households, with only 40% of these households adopting immediately, compared with over 70% of credit unconstrained households. While these adoption rates do increase over time, only 60% of credit constrained households have adopted within 5 years compared with nearly all credit unconstrained households adopting within the same time period. In the longer term for almost 30% of households the credit constraints act as a permanent barrier to adoption. The presence of a well-functioning second-hand market does increase household consumption and welfare but the impacts on overall adoption rates are rather small.
关键词： Credit,Market imperfections,Farm households,Africa,Irreversibility,Solar PVs
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Very High-Resolution Imaging of the City of Goma (North Kivu, D.R. Congo) Using SFM-MVS Photogrammetry
摘要： In complex tropical environment, where the dense vegetation and weather conditions limit the classical use of satellite remote sensing techniques, airborne remote sensing remains the best solution to image large areas in very high spatial resolution. However, implementing such a survey in complex areas like in the region of Goma, North Kivu, Democratic Republic of Congo (DRC), is difficult, expensive and not suitable for fast imaging during crisis periods (the city of Goma is indeed threatened by volcanic eruptions and frequently affected by armed conflicts). Thanks to the support of the Mission of the United Nations in the DRC, we tested the application of Structure-from-Motion Multi-View Stereo photogrammetry to image Goma and its vicinity (~140 km2) using a helicopter and consumer-grade DSLR cameras. The resulting orthomosaic has a spatial resolution of 17.5cm and provides unprecedented details of the city. Direct applications are detailed urban, cadastral and natural hazards mapping.
关键词： Urban Mapping,Volcanic Hazards,Photogrammetry,Central Africa,North Kivu
更新于2025-09-23 15:22:29
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Global Solar Radiation Prediction Using Hybrid Online Sequential Extreme Learning Machine Model
摘要： Accurate global solar radiation prediction is highly essential for related research on renewable energy sources. The cost implication and measurement expertise of global solar radiation emphasize that intelligence prediction models need to be applied. On the basis of long-term measured daily solar radiation data, this study uses a novel regularized online sequential extreme learning machine, integrated with variable forgetting factor (FOS-ELM), to predict global solar radiation at Bur Dedougou, in the Burkina Faso region. Bayesian Information Criterion (BIC) is applied to build the seven input combinations based on speed (Wspeed), maximum and minimum temperature (Tmax and Tmin), maximum and minimum humidity (Hmax and Hmin), evaporation (Eo) and vapor pressure deficiency (VPD). For the difference input parameters magnitudes, seven models were developed and evaluated for the optimal input combination. Various statistical indicators were computed for the prediction accuracy examination. The experimental results of the applied FOS-ELM model demonstrated a reliable prediction accuracy against the classical extreme learning machine (ELM) model for daily global solar radiation simulation. In fact, compared to classical ELM, the FOS-ELM model reported an enhancement in the root mean square error (RMSE) and mean absolute error (MAE) by (68.8–79.8%). In summary, the results clearly confirm the effectiveness of the FOS-ELM model, owing to the fixed internal tuning parameters.
关键词： global solar radiation,West Africa region,energy harvesting,FOS-ELM model,input optimization
更新于2025-09-23 15:22:29
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A 10-year record of aerosol optical properties and radiative forcing over three environmentally distinct AERONET sites in Kenya, East Africa
摘要： In the framework of Aerosol Robotic Network (AERONET), the aerosol optical, microphysical and radiative properties were investigated over three sites (CRPSM_Malindi, Nairobi, and ICIPE_Mbita) in Kenya, East Africa (EA) during 2006-2015. The annual mean (±σ) aerosol optical depth at 440 nm (AOD440) was found high at Mbita (0.27±0.09) followed by Malindi (0.26±0.07), and low at Nairobi (0.19±0.04). Whereas, the seasonal mean AOD440 noticed high (low) values during the local dry (wet) seasons. The aerosol optical properties: AOD, single scattering albedo (SSA), asymmetry parameter (ASY), and complex aerosol refractive index (RI) exhibited significant temporal and spectral heterogeneities illustrating the complexity of aerosol types with an abundance of fine-mode aerosols during the local dry (JJA) season. Characterization of major aerosol types revealed the dominance of mixed-type followed by biomass burning aerosols. The aerosol volume size distribution revealed that the coarse- over fine-mode aerosols showed a significant contribution to the total volume particle concentration, especially at high (> 0.3) AOD440. Further, the aerosol columnar number size distribution (CSD) retrieved from the King’s inversion of spectral AOD exhibited a power law distribution affirming multiplicity of aerosol sources. The direct aerosol radiative forcing values simulated in the shortwave region using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model showed good correlation (r=>0.85) with the AERONET derived ones at the top-of-atmosphere (TOA), bottom-of-atmosphere (BOA) and within the atmosphere (ATM). The annual mean (±σ) TOA, BOA, and ATM forcing values were found in the range from -8.10±3.75 to -13.23±4.87, -34.54±4.86 to -46.11±10.27, and 26.63±6.43 to 36.24±7.26 Wm-2, respectively, with an atmospheric heating rate (AHR) of 0.74±0.12–1.02±0.20 K day-1. The SBDART-derived DARF exhibited significant temporal heterogeneity with high (low) during the local dry (wet) seasons. Results derived from the present study forms a basis for regional climate change studies and could increase the accuracy of climate models over this unexplored region of Africa.
关键词： Aerosol radiative forcing,Aerosol optical depth,Size distribution,East Africa,AERONET,Single scattering albedo
更新于2025-09-23 15:22:29
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Impact of global warming on photovoltaic power generation over West Africa
摘要： Many West African countries are plagued with poor electricity. The abundance of solar irradiance over the region makes solar energy an attractive solution to the problem, but there is a dearth of information on how the ongoing solar dimming and global warming may alter the solar energy over the region in the future at various global warming levels. This study investigates the impact of climate change on photovoltaic power generation potential (PVP) over West Africa under four global warming levels (1.5°C; 2.0°C; 2.5°C and 3.0°C) and under the representative concentration pathway 8.5 (RCP 8.5) climate change scenario. Fourteen regional climate model simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX) were analysed for the study. The capability of the simulations to reproduce the PVP and climate variables over West Africa is quantified. The results show that the CORDEX simulation ensemble captures the spatial distribution and the annual cycle of climate variables and PVP over West Africa, though with few biases. The simulation and observation indicate that PVP over West Africa ranges from 8% to 25% and the annual cycle is influenced by the seasonal variation of the monsoon system. The simulation ensemble projects a decrease of PVP over West Africa in the future and indicates that the magnitude of the decrease grows with warming levels. The maximum decrease in PVP projected over any country or zone in the region is less than 3.8% even for a warming level of 3.0°C. Hence, the study suggests that ongoing global warming may have an influence on PVP over West Africa.
关键词： West Africa,Global warming,Global dimming,Solar energy,Paris agreement
更新于2025-09-12 10:27:22
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Powering Africa Using An Off-Grid, Stand-Alone, Solar Photovoltaic Model
摘要： Over 90 % of Sub-Saharan Africa is without electricity access. The rural areas of the few African countries with access lack electricity. Studies have suggested that solar energy systems hold the key to powering the continent. Although, a vast population currently operate fossil-fuel powered generators to meet their basic electricity needs. The study is designed for a 2-bedroom flat inhabited by an average Africa family. A residential building in Akure, Ondo State, Southern Nigeria has this model installed in a stable and reliable condition. The proposed solar photovoltaic model is composed of solar panels, Direct Current (D.C) cables, charge controller, solar batteries, solar inverter, solar bulbs and instrumentation gadgets. The model is an optimum size solar Photovoltaic installation with a maximum power input of 1,800 W. The maximum allowable load is 1,000 W and a maximum charging D.C voltage of 28.2 V. The solar-powered system is equipped with a set of six (6) 300 Watts monocrystalline solar panels. A commercial maximum power point tracking (MPPT) charge controller was used for this model. Two (2) units of Deep Cycle AGM Solar Batteries connected in series are installed for the solar photovoltaic system. A pure sine wave solar inverter was used in the developed solar PV model to transform D.C electricity available in the batteries to A.C electricity. Themodel is a flexible one which could be scaled up as may be desired or required. The solar photovoltaic model has a very high prospect for powering Africa. The model has ample potentials to fulfil economic, social and environmental objectives which qualifies it as a sustainable energy option to improve the quality of life. The implementation of this form of sustainable energy will open even development of the continent and end the electricity woes of the populace.
关键词： Solar Photovoltaic,Global Warming,Africa,Sustainable Energy,Electricity
更新于2025-09-12 10:27:22
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The Rationale for Selective Laser Trabeculoplasty in Africa
摘要： Glaucoma is the leading cause of irreversible blindness in Africa. The condition is treatable but not curable. There are numerous obstacles to glaucoma care in Africa, including availability, accessibility and affordability of treatments, as well as medication nonadherence among patients. Medical therapy is costly relative to the average income in Africa and it requires daily self-dosing by patients. Surgery is of limited availability in many regions in Africa, and a high proportion of patients refuse surgery because it is expensive. Selective laser trabeculoplasty (SLT) proves to be a favorable alternative to medical or surgical care, as it is highly effective and safe in people of African descent, more cost-effective than medical therapy, quick and easy to perform, and portable. The procedure also requires no postoperative care, thus obviates the issue of nonadherence. In uncontrolled studies, SLT has a high response rate and it lowers intraocular pressure by 30% to 40%, which exceeds the goal in international guidelines for initial therapies. The African Glaucoma Consortium (AGC), a member-driven stakeholder collective, has been formed in part to develop the infrastructure for continent-wide improvements in glaucoma care. It embraces SLT as a potential key tool in their development plans. The mission of AGC includes improving clinical care by educating existing and new health care professionals to expand the provider network, by conducting trials to identify optimal care strategies for glaucoma in Africa, and by facilitating the development of an integrated network of Centers of Excellence to bring SLT and other crucial glaucoma therapies to communities throughout Africa.
关键词： selective laser trabeculoplasty,Africa,glaucoma
更新于2025-09-11 14:15:04
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Molecular Diagnosis of Inherited Retinal Diseases in Indigenous African Populations by Whole-Exome Sequencing
摘要： PURPOSE. A majority of genes associated with inherited retinal diseases (IRDs) have been identi?ed in patients of European origin. Indigenous African populations exhibit rich genomic diversity, and evaluation of reported genetic mutations has yielded low returns so far. Our goal was to perform whole-exome sequencing (WES) to examine variants in known IRD genes in underrepresented African cohorts. METHODS. Whole-exome sequencing was performed on 56 samples from 16 families with diverse IRD phenotypes that had remained undiagnosed after screening for known mutations using genotyping-based microarrays (Asper Ophthalmics). Variants in reported IRD genes were identi?ed using WES and validated by Sanger sequencing. Custom TaqMan assays were used to screen for identi?ed mutations in 193 unrelated indigenous Africans with IRDs. RESULTS. A total of 3494 variants were identi?ed in 217 known IRD genes, leading to the identi?cation of seven different mutations (including six novel) in six genes (RHO, PRPF3, PRPF31, ABCA4, CERKL, and PDE6B) in six distinct families. TaqMan screening in additional probands revealed identical homozygous CERKL and PDE6B variants in four more patients. CONCLUSIONS. This is the ?rst report of WES of patients with IRDs in indigenous African populations. Our study identi?ed genetic defects in almost 40% of the families analyzed, signi?cantly enhancing the molecular diagnosis of IRD in South Africa. Thus, WES of understudied cohorts seems to present an effective strategy for determining novel mutations in heterogeneous retinal diseases.
关键词： genetic testing,vision loss,inherited blindness,South Africa,retinal degeneration,next generation sequencing,photoreceptor dysfunction,clinical genetics
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Worldpop - Fusion of Earth and Big Data for Intraurban Population Mapping
摘要： High resolution estimates of human population distributions are very useful for large-scale or national scale analyses in many fields including epidemiology, healthcare, resource distribution, and development. Population densities have long been estimated using remote sensing data, particularly at large spatial scales. However, the accuracy of population density predictions can be very poor in cities, and this is particularly relevant in urban areas in sub-Saharan Africa. Here we map intra-urban population densities for select African cities by disaggregating census data using random forest techniques with remotely-sensed and geospatial data, including bespoke time-series intra-urban built-up data. We produce maps with up to 83% explained variance and find including built-up density layers in urban population models allows for clear improvements in prediction.
关键词： machine learning,population density,census,built-up,Urban areas,Africa
更新于2025-09-10 09:29:36