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Abstract Published results on rainwater management systems revealed a lack of holistic science-based design principles. A new approach to rainwater management is proposed. Its necessity and feasibility are discussed. It is demonstrated that quantitatively harvesting rainfall and infiltrating a fraction should be mandatory. Thus, the primary site-specific parameter is the intensity of rainfall. Clearly, rainwater should be harvested and used everywhere as a valuable resource. Under arid semi-arid conditions large tanks maximize water storage for the long dry season while under humid conditions the same helps to minimize the frequency of emptying to avoid flooding. The new approach separates rainwater (and stormwater) from sewage and has the potential to maintain the natural hydrological cycle in urban areas despite urbanization. In already crowded slums, rainwater harvesting (RWH) can also be used to restore the hydrological cycle. The new approach advocates for decentralized RWH infrastructures to harvest, infiltrate, and store rainwater in individual residences, while piping overflows to semi-centralized cluster-scale tanks. Rooting integrated water resource management on RWH appears to be the missing puzzle in: (i) restoring the natural hydrological cycle where it has been disturbed (landscape restoration), (ii) avoiding flooding, and (i) mitigating soil erosion. This is essential for sustainable development.

Abstract The uncertainty regarding the correlation between sea spray aerosol (SSA) formation and sea surface temperature (SST) hinders the accurate estimation of SSA’s impact on global climate. Here, we developed a temperature-controlled plunging SSA simulation tank to investigate the impact of SST on SSA formation from two perspectives: SSA particle size distribution and organic enrichment. Our findings show that SSA particle size decreases with decreasing SST, as exhibited by an increase in SSA within Aitken mode and a decrease in SSA within accumulation and coarse modes. SST can significantly enhance organic enrichment in SSA particles, while the multiplicative increases vary from 2 to 10 times depending on the organic matter species and the SSA particle size. Based on our experimental results, it is predicted that SST reduction may lead to a significantly higher contribution of Aitken modal SSA-derived CCN in cold waters (0 °C) than in warm waters (30 °C). Additionally, we incorporate SST for the first time in estimating the global flux of dissolved organic carbon (DOC) emitted via SSA, yielding a value ranging from 23.45 to 55.78 Tg C yr−1. Compared to previous works, our study reveals the crucial role of SST in influencing both cloud formation and the atmospheric organic burden of SSA.

Abstract Groundwater resource management and development should be done sustainably, which calls for accurate assessment based on new methods and scientific principles. There is an increasing demand for potable water supplies, to meet the woefully inadequate domestic water needs in the Batcham municipality (west of Cameroun). The dearth of knowledge on sustainable management of water resources is to blame for this predicament. As integrated methodologies are not used in groundwater exploration programs, the current problem has gotten worse. Innovative scientific principles of groundwater resource exploration are required to effectively counteract the non-rationalization of water and the problem of unacceptable failure rates in drilled water borehole development. This will improve the appropriate and sustainable use of these resources. Therefore, the goal of this research is to map groundwater potential zones by utilizing readily available datasets and remote sensing (RS), GIS, Frequency Ratios (FR), and multi-criteria analysis (AHP) techniques. The database used is made up of geological data, hydroclimatic data, well data, and satellite images. Each of the methods used is based on the study of the relationships between the factors controlling the groundwater potential. Among these factors, ten (10) were retained based on previous work; these are slope, elevation, land use, land cover, lineament density, drainage density, topographic wetness index, curvature, geology, rainfall, and the static water level. The AHP allowed, according to the user's expertise, to assign weights to each factor controlling the water potential. The FR made it possible to study the relationships linking each variable with high flow rates. The thematic layers obtained were integrated into a GIS environment to generate the groundwater potential map. Four classes of groundwater potential have been identified: bad, moderate, good, and excellent. The bad classes represent 8.32% and 11.21%; moderate 36.57% and 28.70%; good 43.55% and 38.93%; and excellent 11.56% and 21.16%, for the AHP and FR models, respectively. The overlying of wells with high flow rates on areas of excellent groundwater potential shows perfect concordance, which validated the final map. Likewise, the resulting map was validated by sensitivity curve analysis, and the receiver operating characteristic (ROC) curve from which result accuracy was obtained is 70.63% and 80.28% for the AHP method and FR method, respectively. Finally, the FR model outperformed the AHP model in terms of performance and it is possible to use these dependable models to describe groundwater potential zones in the other regions of Cameroon.

This article presents the suitability analysis of onshore wind farm sites using an AHP (Hierarchical Analysis Process) multi-criteria decision-making (MCDM) approach based on geographic information system modeling (GIS). It is based on different technical aspects (wind speed, elevation, slope), economic (proximity to the electricity network, proximity to roads) and social (proximity to residential areas, population density). The introduction of the factor “population density” and the constraint “required area” rarely used in previous studies makes it possible to refine the results. The data is classified into several categories in a gradual manner, namely unsuitable (0); less suitable (1); suitable (2); highly suitable (3) and most suitable (4). The results show us that the largest percentage relating to spatial coverage is observed in the “suitable” range with 50.89 % and the corresponding theoretical wind power potential (TWPP) is 1377.926 GW; it is followed by “highly suitable” 5.67 % and a TWPP of 153.652 GW; then “less suitable” with 1.04 % and a TWPP of 28.163 GW. No areas were identified in “most suitable” and finally the “unsuitable” range with 42.4 %. Also, the most favorable areas are located in the part of the far north of the country corresponding to the strong wind zone. The sensitivity analysis was carried out based on scenario tests (technical, economic and equal-weight) in order to give greater visibility of choice to the different stakeholders who would like to invest in onshore wind energy in Cameroon. Furthermore, a study of hybrid solar-wind systems could improve the efficiency of electricity parks in Cameroon.

ABSTRACTUrban forests are characterized by relationships between people and trees, where urban trees provide benefits to people and people make decisions impacting trees. People’s perceptions of urban forests are related to the cognitive processes that underpin benefits received from trees, while also influencing support for or against trees and their management. A growing literature has considered urban forest perceptions, but most studies are limited to a single geographic area and focus on socio-economic influences, with less consideration of location and cultural influences. This study explores the relationship between where people live, the language they speak, and multiple perception responses associated with urban forests (i.e. values, beliefs, trust, satisfaction) to better understand commonalities and differences across distinct geographic settings and populations. We conducted an online survey about urban forest perceptions in three Canadian urban regions, allowing us to explore perceptions between regions, locations on an urban gradient and language spoken. We found geographic and language differences primary for beliefs held about urban trees and trust in municipal government’s decision-making about those trees, while values and satisfaction with trees and their management were more stable across geographic settings and language spoken. Our findings suggest that some perceptions vary between populations. Additionally, our findings reinforce the need for urban forest managers to understand the specific perceptions held by different populations, rather than assume universality of perception, to ensure specific and differential urban forest management objectives are in place to supports local people and ecological elements.

Distracted driving is a major cause of road traffic crashes in Yaoundé. This is partly due to the scarcity of enforcement and a lack of evidence and investigation using the distraction safety performance indicator (SPI), hindering evidence-based interventions. This study aimed to address this evidence gap by evaluating the distraction SPI using a proven methodology. Data on distracted driving (handheld mobile device; interaction; eating/smoking/drinking) were collected from roadside observations on 36 randomly selected road sections carefully spread to cover the city. SPIs were computed and weighted with traffic volume to ensure the representativeness of the values. A total of 41,004 drivers were observed (38,248 in cars; 1116 in vans; 977 in trucks; 663 in buses). The prevalence of distracted driving in Yaoundé is 13.69% for the three distractions type combined. The prevalence is 7.84% for interaction, 4.89% for handled mobile device usage and 0.96% for eating/smoking/drinking. Leveraging these insights, a seven year (2024–2030) fighting strategy aimed at halving the prevalence was developed. The strategy contains interventions including legislation/enforcement, which have been proven to be effective. This study, pioneered in Yaoundé, provides stakeholders with evidence of the issue and measures to implement and can also be used when developing a road safety strategy. Future research should consider investigation at national level.

Aromatic acids are ubiquitous in seawater (SW) and can be transported to the atmosphere via sea spray aerosol (SSA). Despite their importance in affecting the global radiative balance, the contribution of marine aromatic acids and their transport mechanisms through SSA remain unclear. Herein, the distribution of particle size and number concentration of SSA produced in SW containing nine different aromatic acids (i.e., benzoic acids, benzenedicarboxylic acids, hydroxybenzoic acids, vanillic acid, and syringic acid) was studied using a custom-made SSA simulation chamber; moreover, the enrichment of aromatic acids in SSA and their emission flux to the atmosphere were analyzed. Transmission electron microscopy (TEM) images clearly revealed that aromatic acids can be transferred to the nascent SSA. Interestingly, the morphology associated with benzenedicarboxylic-acid-coated particles showed that aromatic acids can promote the growth of other surfaces of sea salt, thus making the sea salt core spherical. Aromatic acids showed a significant enrichment behavior at the air–sea interface, which clearly indicated that SSA represents a source of aromatic acids in the atmosphere. Vanillic acid had the largest global emission flux through SSA (962 t yr−1), even though its concentration in SW was lower. The calculated results indicated that the global annual flux of aromatic acids was affected not only by the concentration in SW, but also by their enrichment factor (EF). These data are critical for further quantifying the contribution of organic acids to the atmosphere via SSA, which may provide an estimate of the potential influence of the atmospheric feedbacks to the ocean carbon cycle.

Diagnosis of most ophthalmic conditions, such as diabetic retinopathy, generally relies on an effective analysis of retinal blood vessels. Techniques that depend solely on the visual observation of clinicians can be tedious and prone to numerous errors. In this article, we propose a semi-supervised automated approach for segmenting blood vessels in retinal color images. Our method effectively combines some classical filters with a Generalized Linear Model (GLM). We first apply the Curvelet Transform along with the Contrast-Limited Histogram Adaptive Equalization (CLAHE) technique to significantly enhance the contrast of vessels in the retinal image during the preprocessing phase. We then use Gabor transform to extract features from the enhanced image. For retinal vasculature identification, we use a GLM learning model with a simple link identity function. Binarization is then performed using an automatic optimal threshold based on the maximum Youden index. A morphological cleaning operation is applied to remove isolated or unwanted segments from the final segmented image. The proposed model is evaluated using statistical parameters on images from three publicly available databases. We achieve average accuracies of 0.9593, 0.9553 and 0.9643, with Receiver Operating Characteristic (ROC) analysis yielding Area Under Curve (AUC) values of 0.9722, 0.9682 and 0.9767 for the CHASE_DB1, STARE and DRIVE databases, respectively. Compared to some of the best results from similar approaches published recently, our results exceed their performance on several datasets.

BackgroundHIV infection and its progression to AIDS depend on several factors including host genetic factors. The immunological mechanisms of host resistance to HIV infection greatly influence the prevalence of HIV in a given region. Worldwide, Cameroon not exempted, the frequency of AIDS-associated genes varies and may influence this prevalence. The North and Far North Regions of Cameroon have had the lowest HIV prevalence in the country for many years despite risky behaviors associated with their customs and habits. In this work, we seek to explore the contribution of host genes to the HIV low prevalence in these regions.MethodologyFive genes variants previously described as HIV AIDS related were studied. These genes are: CCR5Δ32, CCR5promoter59029G, CCR2-64I, SDF1-3ʹA and Trim5α(R136Q). A total of 384 consented participants were included in this study. The HIV serological status was confirmed using national algorithm. Genomic DNA was extracted from the buffy coats and used for genotyping. The results obtained were compiled in Excel 2016, Epi Info 7.1 and snpStats software and Chi two tests allowed us to compare the frequencies of the AIDS related alleles in the North with those in other Regions of Cameroon and to measure the impact of these ARGs on protection against HIV.ResultsThe frequency of protective alleles CCR5Δ32, CCR5promoter59029G, CCR2-64I, SDF1-3ʹA and Trim5α(R136Q) was the allelic frequencies should be expressed as percentages i.e. 0.52%; 37.56%; 36.46%; 25.19% and 69.33%. These allelic frequencies exhibited a significant difference when compared to those obtained in other regions of Cameroon (p < 0.01). Protective alleles were predominant in the Northern region compared to others and were associated with resistance to HIV [(p < 0.0001); OR = 2.02 CI, 95%].ConclusionThe higher frequency of HIV-protective alleles in the northern regions may be a contributing factor to the lower prevalence of HIV. Nevertheless, this should be reinforced by other preventive and surveillance methods to guarantee the sustained low prevalence. HIV can develop resistance through the process of mutation, but the host targets themselves are genetically stable. The study of these host genetic restriction factors is of great value in the design of a practical cure for HIV infection or an effective vaccine.

Résumé : Cette réflexion porte sur les interactions verbales comme stratégie de l’exhibition de l’ethos de l’annonceur et des internautes dans les publicités de Tangui et Supermont en ligne sur Facebook. L’ethos étudié est discursif, parce que construit dans les discours des interlocuteurs susmentionnés. Dans ces conditions, l’annonceur donne une image positive de sa marque ou de son promoteur en vue de flatter sa cible afin qu’elle consomme les produits vendus. Cependant, les internautes se montrent tantôt agressifs, tantôt complimenteurs, afin de (dé)valoriser les différentes marques, de les blâmer ou les encourager. Il se dégage ainsi une interaction verbale reposant sur les FFAs et les FTAs, donnant lieu à deux types de lien entre l’annonceur et les internautes: relation irénique et relation agonale. En fin de compte, l’image discursive des interlocuteurs a un objectif pragmatique visant à influencer l’autre aux niveaux cognitif et comportemental. Mots-clés : annonceur, (dé)valorisation, ethos, internaute, publicité,

The Stirling refrigerator is a device capable of using green energies such as solar power. In this work, a refrigerator-Stirling/photovoltaic system is proposed to harness solar energy for cold production. The system consists of photovoltaic (PV) panels that capture solar energy and convert it into electricity, and a transmission belt linking the motor to the Stirling beta refrigerator to use the electricity for cooling purposes. The system is modeled on the basis of finite-dimensional thermodynamics, taking into account the refrigerator's internal and external irreversibilities. In addition, the wiring loss, dust coverage and shading of the photovoltaic system and the mechanical power loss of the Stirling refrigerator are taken into account in this model. Power equality has been considered as a system constraint. Finally, the effects of operational and design parameters on system performance are investigated. A numerical code is written in Matlab. The effects of PV module efficiency, Stirling regenerator efficiency and PV derating factor on system performance are quantified, also the optimum operating parameters obtained. The refrigerator-Stirling/photovoltaic has a high COP and a low cooling capacity, in contrast to the refrigerator-Stirling/Dish-Stirling. The optimum solar electric COP and maximum cooling rate are 0.7063 and 1413 W respectively at an optimum panel area of 2 m2. Optimum exergy efficiency is 38.5 % at fv = 0.1, ecological coefficient of performance (ECOP) is 20.3 % at N = 48 rot.s−1, optimum exergy destroyed is 33.31 W at K1 = 21.5 W.K−1. This system can be used to preserve vaccines in hospitals.

Donor cell leukemia (DCL) is a rare complication after allogeneic hematopoietic stem cell transplantation (HSCT) accounting for 0.1% of relapses and presenting as secondary leukemia of donor origin. Distinct in phenotype and cytogenetics from the original leukemia, DCL’s clinical challenge lies in its late onset. Its origin is affected by donor cell anomalies, transplant environment, and additional mutations. A 43-year-old woman, treated for early stage triple-negative breast cancer, developed mixed-phenotype acute leukemia (MPAL), 12 years later. Following induction chemotherapy, myeloablative conditioning, and allo-HSCT from her fully HLA-matched brother, she exhibited multiple cutaneous relapses of the original leukemia, subsequently evolving into DCL of the bone marrow. Cytogenetic analysis revealed a complex male karyotype in 20 out of 21 metaphases, however, still showing the MPAL phenotype. DCL diagnosis was confirmed by 90.5% XY in FISH analysis and the male karyotype. Declining further intensive chemotherapy including a second allo-HSCT, she was subsequently treated with repeated radiotherapy, palliative systemic therapies, and finally venetoclax and navitoclax but died seven months post-DCL diagnosis. This case underlines DCL’s complexity, characterized by unique genetics, further complicating diagnosis. It highlights the need for advanced diagnostic techniques for DCL identification and underscores the urgency for early detection and better prevention and treatment strategies.

Rainwater harvesting (RWH) is principally based on collecting, storing, and using rainfall which would otherwise be lost as surface runoff. Runoff threatens in several ways: accelerating erosion, intensifying flooding, and reducing groundwater recharge. Therefore, purposely retaining rainfall in the urban water cycle rather than draining has several positive impacts on designing sustainable cities. This work presents a proposal on how to avoid flooding in cities by systematically harvesting, storing rainwater, and using it for multiple purposes. The concept of RWH presented here has the potential to be a radical innovation to solve the social, economic, and environmental challenges associated with flash flooding. Each residence is regarded as a water production unit. Depending on the climatic conditions, people can meet their water needs on a local household basis, or alternatively use piped water as a complement. By infiltrating rainwater, groundwater is locally recharged and downstream wells are more productive. The implementation of this idea involves entrepreneurial agency that challenges existing structures, rather than adapting to them. Clearly, social entrepreneurship and social innovation are expected to catalyse the realization of this social innovation, also in rural areas. It is about mobilizing ideas, capacities, and resources to create a sustainable social transformation. HIGHLIGHTS Rainwater harvesting is a well-established tool to retain water within the city.; Harvested rainwater is conventionally used for non-potable used (clean and green city).; The potential of rainwater for safe drinking water provision has been largely overlooked.; A new concept for urban water management, encompassing flash flood mitigation is presented.; Harnessing active engagement of all citizens facilitates the efficiency of this concept.;

Caused by pathogenic microorganisms, infectious diseases are known to cause high mortality rates, severe burdens of disability, and serious worldwide aftermaths. Drug-resistant pathogens have reduced the efficacy of available therapies against these diseases, thus accentuating the need to search for effective antimicrobials. Medicinal plants have served as starting material for the preparation of a number of antimicrobial agents. To this end, the present study highlights the green synthesis of Cocos nucifera-based nanomaterials and evaluation of the mechanistic basis of their antimicrobial action. Accordingly, Cocos nucifera extract was used for the reduction of silver nitrate solution to afford silver nanoparticles. These entities were further incorporated onto sulfuric-acid-based activated carbons to generate the nanocomposites. The antimicrobial activity of the as-prepared nanomaterials was evaluated using the broth microdilution method, while the antioxidant activity was assessed through standard methods. The cytotoxicity of potent nanomaterials was assessed on Vero cells by the spectrophotometric method. As a result, nanoparticles were successfully synthesized, as evidenced by the ultraviolet–visible spectroscopy analysis that revealed an intense absorption spectrum at 433 nm. Fourier Transform Infrared Spectroscopy presented the functional group moieties involved as a capping and reducing agent in the synthesis of the nanomaterials. The incubation of nanomaterials with selected bacterial and fungal strains has led to significant inhibitory effects of these pathogens with minimum inhibitory concentrations ranging from 7.813 to 250 μg/mL. In antioxidant assays, the nanocomposites presented scavenging activities comparable to those of ascorbic acid. Cytotoxicity experiment revealed no toxic effects on Vero cells (range of selectivity indices: from >4 to >128). These results provide evidence of the implication of Cocos nucifera-based nanomaterials in targeting bacterial or fungal systems that mediate free-radical damage or by inhibiting the oxidative damage caused by selected bacteria and fungi, the most susceptible being Escherichia coli and Candida albicans, respectively.

Organic peroxides (OPs) are an important component of dissolved organic matter (DOM), detected in various aquatic media. Despite their unique functions as redox agents in water ecosystems, the complete mechanisms and factors controlling their transformation are not explicitly established. Here, we evaluate the pH effect on the aqueous-phase reaction of three selected OPs (methyl hydroperoxide (MHP), peracetic acid (PAA), and benzoyl peroxide (BZP)) with dissolved SO2. Results show that due to the presence of the hydroperoxyl group in their structures, MHP and PAA are susceptible to forming inorganic sulfate and organosulfate (methyl sulfate for MHP and acetyl sulfate for PAA) depending on the pH, while BZP exclusively forms organosulfate (benzoyl sulfate) in the pH range investigated. Moreover, it is seen that the ability of PAA to form inorganic sulfate relative to organosulfate is more pronounced, which is supported by a previous experimental observation. The effective rate constants of the transformation of these peroxides within the pH 1–10 and 240–340 K ranges exhibit positive pH and temperature dependencies, and BZP is seen to degrade more effectively than MHP and PAA. In addition to the pH impact, it is highlighted that the formation of organic and/or inorganic sulfate strongly depends on the nature of the substituents on the peroxy function. Namely, PAA and BZP are more reactive than MHP, which may be attributed to the electron-withdrawing effects of -C(O)R (R = -CH3 and -C6H5 for PAA and BZP, respectively) substituents that activate the peroxy function. The results further indicate that the aqueous-phase degradation of OPs can adequately drive the change in the chemical composition of DOM, both in terms of organic and inorganic sulfate mass fractions.

The present paper performs a techno-economic and an environmental analysis of an islanded energy system based on Geothermal/Biogas/Wind/PV hybrid energy system using two battery technologies for electricity generation in the city of Woulde in Cameroon. The innovation of the present paper is threefold: (i) a geothermal plant was modeled, and coupled to various power sources and battery technologies; (ii) an environmental analysis of the hybrid system was performed; and (iii) a solar dual-axis tracker (DAT) was incorporated in the system. The study findings suggested that the integration of a DAT reduced the battery requirements. The results demonstrated that integrating the DAT in the architecture minimized the levelized cost of energy, i.e. from US$ 0.271/kWh to US$ 0.260/kWh for lead-acid (LA) batteries, and from US$ 0.269/kWh to US$ 0.256/kWh for lithium-ion (LI) batteries. It was revealed that the net present cost varied from US$ 61.3 million to US$ 58.9 million for LA batteries, and from US$ 61.0 million to US$ 58.0 million for LI batteries. For both energy storage technologies, the use of a DAT improved the photovoltaic electricity production (about 32.0 % more power). The solutions also revealed that the monthly electricity production of the biogas generator increased with the use of a DAT (about 227.74 % and 7.16 % more power with LA and LI batteries respectively). Concerning the monthly electricity production of the geothermal generator, it decreased with the use of a DAT (about 15.30 % and 7.96 % less power with LA and LI batteries respectively). In addition, the integration of a DAT in the hybrid system increased the emissions of Carbon dioxide and Carbon monoxide. The computation of the excess of electricity revealed a variation from 6,439.0 kWh/year (for fixed system) to 1,676.0 kWh/year (for the system incorporating a DAT) when the LA storage technology was used. For LI technology, it was shown that the excess of electricity increased from 657.0 kWh/year (for fixed system) to 2,420.0 kWh/year (for the system incorporating a DAT). It was also found no unmet load in the different architectures implemented, which simply indicated that the energy produced by the scenarios covered the electricity needs. It was also demonstrated that the electricity production was largely dominated by the geothermal plant for all the scenarios, followed by the PV panels, biogas, and wind turbine generators. It was also found that the wind turbine electricity generation was mainly recorded during the months of January, February, March, and December.

The current electricity challenges in Africa have spurred the interest of governments in incorporating renewable energy sources into the energy mix. The use of hybrid solar energy systems has become a practical choice for electrification. The novelty of the paper is threefold: (i) The Grid/Fuel Cell/PV/Electrolyzer hybrid system is modeled, simulated, and optimized in for some communities of the nineteen countries of the African and Malagasy Council for Higher Education (CAMES) for the very first time; (ii) The levelized costs of hydrogen and energy were evaluated and compared; (iii) PV, fuel cell, grid purchases, and grid sales power productions were determined and compared. The study findings showed a levelized cost of energy varying between US$ 0.238/kWh (in Madagascar) and US$ 0.344/kWh (in Gabon). Subsequently, among the West, Central, and East African countries of CAMES, Mali, Chad, and Burundi were the countries with the smallest LCOE respectively. Also, the levelized cost of hydrogen ranged between US$ 1.84/kg (in Madagascar) and US$ 2.17/kg (in Gabon and Equatorial Guinea). The computation of the net present cost indicated a variation between 183,536 US$ (in Madagascar) and 216,115 US$ (in Gabon). The PV, fuel cell, grid purchases, and grid sales power productions were between 34,044 kWh/year (in Gabon) and 53,176 kWh/year (in Mali) for PV productions; between 43,526 kWh/year (in the Democratic Republic of Congo) and 43,784 kWh/year (in Chad) for fuel cell productions; between 29,976 kWh/year (in Senegal) and 30,700 kWh/year (in the Congo Republic) for grid purchases power productions; and between 11,604 kWh/year (in Gabon) and 29,608 kWh/year (in Mali) for grid sales productions respectively. It was concluded that the PV power production was the highest power generated by the hybrid system when compared with fuel cell, grid sales, and grid purchases power productions. Concerning the PV penetration, it varied between 54.2 % (in Gabon) and 84.7 % (in Mali). The present work is aimed at decision-makers so that they become aware of the need to urgently develop the renewable energy sector in the countries for a successful energy transition in Africa.

The development of antimicrobial resistance has increased the prevalence of infectious diseases, causing a global health problem that accounts for over 4.95 million deaths worldwide annually. The side effects associated with current antibiotics prompt a crucial need to search for effective and safe antimicrobial agents. In this study, silver nanoparticles (AgNPs) were prepared by chemical reduction method using silver nitrates as a metallic precursor and Croton macrostachyus bark aqueous extract as a reducing and capping agent. The nanoparticles were further functionalized using C. macrostachyus-based activated carbon (CAC) to generate nanocomposites (CAC-AgNPs). The nanomaterials were characterized by ultraviolet-visible (UV–vis) absorption spectra and Fourier transform infrared (FTIR) spectra. The antibacterial activity of the as-prepared nanomaterials was evaluated against an array of bacterial strains by microdilution method, whereas their cytotoxicity profile was evaluated using Vero cells (human mammalian cells). Antibacterial mechanistic studies of active nanomaterials were carried out through bacterial growth kinetics, nucleic acid leakage tests, and catalase inhibition assays. As a result, the as-prepared nanomaterials exhibited antibacterial activity against an array of bacterial strains (minimum inhibitory concentration (MIC) range: 62.5 to 500 µg/mL), the most susceptible being Escherichia coli and Staphylococcus aureus. Cytotoxicity studies of the nanomaterials on Vero cells revealed that the nanocomposite (median cytotoxic concentration (CC50): 213.6 µg/mL) was less toxic than its nanoparticle (CC50 value: 164.75 µg/mL) counterpart. Antibacterial mechanistic studies revealed that the nanomaterials induced (i) bacteriostatic activity vis à vis E. coli and S. aureus and (ii) inhibition of catalase in these bacteria. This novel contribution regarding the antibacterial mechanisms of action of silver nanocomposites from C. macrostachyus-based activated carbon may contribute to our understanding of the antibacterial action of these biomaterials. Nevertheless, more chemistry and in vivo experiments as well as in depth antibacterial mechanistic studies are warranted for the successful utilization of these antibacterial biomaterials.

Abstract Background The Viral hepatitis elimination by 2030 is uncertain in resource-limited settings (RLS), due to high burdens and poor diagnostic coverage. This sounds more challenging for hepatitis C virus (HCV) given that antibody (HCVAb) sero-positivity still lacks wide access to HCV RNA molecular testing. This warrants context-specific strategies for appropriate management of liver impairment in RLS. We herein determine the association between anti-HCV positivity and liver impairment in an African RLS. Methods A facility-based observational study was conducted from July-August 2021 among individuals attending the “St Monique” Health Center at Ottou, a rural community of Yaounde,Cameroon. Following a consecutive sampling, consenting individuals were tested for anti-HCV antibodies, hepatitis B surface antigen (HBsAg) and HIV antibodies (HIVAb) as per the national guidelines. After excluding positive cases for HBsAg and/or HIVAb, liver function tests (ALT/AST) were performed on eligible participants (HBsAg and HIVAb negative) and outcomes were compared according to HCVAb status; with p 50 years compared to younger ones [38.46%(15/39) versus 12.36% (33/267) respectively, OR(95%CI) = 4.43(2.11-9.29), p 50 versus younger ones [69.23% (27/39) versus 24.72%(66/267) respectively, p

Abstract The main viral protease (Mpro) of SARS-CoV-2 provides an excellent target for antivirals, due to its essential and conserved function in the viral replication cycle. We reported in this study, the SARS-CoV-2 main protease inhibitory effect of twelve compounds isolated from D. caloneura and P. erinaceus together with four derivatives. Among the effectively tested samples, two derivatized compounds displayed significant improvement on the activity from the starting material, friedelin (1) through the acetoreduced (2) to the acetoxy product (3) with respective IC50 values of 42.89, 29.69 and 19.39 µg/mL. The latter displayed the highest activity although lower as compared to that of baicalein, the positive control with IC50 0.41 µg/mL. The molecular docking study showed that an increase in the number of hydrogen bonds between compounds and active site of Mpro resulted in increased inhibition. Graphical Abstract

Abstract The influence of intra-seasonal oscillations (ISO) on rainfall in Central Africa (CA) during the March–May (MAM) season is assessed using the National Oceanic and Atmospheric Administration Climate Prediction Center daily gridded rainfall data. ISO indices are defined using the time series analysis of the first two principal components resulting from the empirical orthogonal function, applied to daily filtered outgoing longwave radiation. Based on these indices, a total of 71 strong Intraseasonal Events (SIEs) and 66 weak Intraseasonal Events (WIEs) were selected using threshold method. The results show that SIEs are associated with enhanced rainfall conditions over almost all the study area, while WIEs provide a meridional dipole-like rainfall pattern, consisting of increasing precipitation in the western part and decreasing in the eastern part of CA. The relationship with Madden–Julian Oscillation (MJO) was also examined. The positive rainfall anomalies associated with MJO phases progress eastward and are modulated by the 850 and 200 hPa horizontal wind. The circulation, linked to geopotential height anomalies at lower layers, tends to strengthen (reduce) the convective activity over the region during extreme ISO events and for the MAM season throughout the study period. Uncentered pattern correlation was further used to assess the link between ISO and MJO phases during the MAM season and we found a correlation of 0.5 in precipitation anomalies between phases 1 and 2 of the MJO and the SIEs; − 0.4 and − 0.6 between phases 5 and 6 and the SIEs respectively, suggesting a strong relationship between ISO events and MJO.