University of N'Djamena

Contexte : Au Tchad, les parcours naturels constituent la base de l’alimentation des ruminants. Leur productivité est tributaire des conditions édaphiques et climatiques. Dans le département de Barh Kôh, dans la zone soudanienne, la productivité des parcours naturels, l’ingestion au pâturage et la contribution des différentes catégories d’herbacées au régime alimentaire des bovins sont mal connues, ce qui rend difficile la formulation de rations complémentaires. Objectif : Cette investigation se propose de quantifier l’ingestion au pâturage et de caractériser la qualité des fourrages consommés en fonction de la localité (sous-préfecture), de l’année et de la saison. Méthodes : Les travaux ont été conduits sur quatre parcours naturels distincts. La productivité de ces parcours a fait l’objet d’une première évaluation en 2019, suivie d’une réévaluation en 2021. Une étude du comportement alimentaire des bovins zébu Goudali (Bos taurus indicus) localement appeler (Bogolodji ou Bokolodji) a été réalisée durant la saison pluvieuse, sur une période de 10 jours pour chaque parcours. Résultats : La productivité et la capacité de charge des parcours naturels étaient de 3,4 ± 0,4 t MS/ha et 1,2 ± 0,3 UBT/ha/an respectivement. La productivité a varié significativement entre les localités (p < 0,05) et a été influencée par l’année (p < 0,001). Suite aux importantes précipitations enregistrées en 2019 (1 237 mm d’eau), la productivité a été plus élevée (4,7 t MS/ha), mais elle a diminué de 50 % en 2021 par rapport à la moyenne des années précédentes. La saison n’a pas eu d’effet significatif sur la productivité des parcours (p > 0,05) (3,3 ± 0,5 et 3,0 ± 0,4 t MS/ha, en pleine saison pluvieuse et au début de la saison sèche respectivement). Les bovins Goudali ont ingéré 7,9 kg de MS par jour d’herbes de parcours naturels constituées pour moitié de graminées, pour un quart de légumineuses herbacées et pour un quart de ligneux ayant pour valeurs 0,55 UFL et 0,47 UFV par kg de MS. Les valeurs de PDIN (92 g/kg MS) sont en moyenne de 10 % supérieures à celles des PDIE (82 g/kg MS). Conclusions : Ces résultats permettent une gestion efficace des parcours naturels de type Soudanien et d’orienter les stratégies de supplémentation des bovins au Tchad.

ABSTRACT This study examines the linear and the non‐linear effects of international trade taxes on access to clean cooking technologies in Sub‐Saharan Africa between 2000 and 2023. The study adopts several robust estimation strategies, including the Driscoll–Kraay cross‐sectional dependence estimation, the two‐step system GMM approach, and the Dynamic Panel Thresholds strategy. The findings reveal a dual effect: while international trade taxes exert a positive linear impact at moderate levels, they produce a negative non‐linear effect once the tax rate surpasses a dynamic threshold of 5.039. The estimated dynamic threshold of 5.039% marks the turning point beyond which trade taxes negatively affect clean cooking access. The results are consistent across rural and urban populations, low and middle‐income economies, as well as between countries with low versus high energy import dependence, with the non‐linear effect most severe among high importers. Complementary factors such as internet penetration, trade openness, governance quality, and domestic credit significantly enhance access to clean cooking fuels and technologies. These results underscore the need for “smart” taxation policies that balance fiscal space generation with household affordability. Policy recommendations emphasise differentiated tariff regimes, strengthened credit markets, improved governance, and regional trade cooperation to accelerate universal clean cooking access in SSA.

The various morphological parameters of watersheds play a crucial role in determining their hydrological behavior. The analysis of morphometric parameters is the fastest and most economical way to represent the hydrological and physiographic characteristics of watersheds. This study uses GIS and remote sensing to determine morphometric parameters in order to assess the understanding of physiographic, morphological, and hydrographic properties. The parameters were analyzed using a digital elevation model (DEM) combined with Excel software. A total of thirteen parameters (Gravelius Compact, Shape factor, hypsometric curve, soils, average elevation, Equivalent rectangle, Average slope index, Total elevation difference, Overall slope index, Specific elevation difference, Drainage density, River frequency, Concentration time) were determined to assess the various characteristics of the Abéché watershed. The values of the relief parameters show that the watershed has a steep relief (382 m). The density of the hydrographic network indicates a very coarse nature (1.16 km) and represents an elongated shape. The hypsometric curve shows that the Abéché watershed is at a mature stage of formation. These results would be useful for evaluating watersheds for drainage management and environmental planning for sustainable management and development.

This study investigated the phytochemical profile of Solanum Obtusifolium Dunal extract and explored its biological activities, such as antihyperglycemic, antiglycation, and anti-inflammatory properties. Also, it conducted computational analyses, such as molecular docking simulations. Advanced technique, including high-performance liquid chromatography with a diode-array detector, was employed to identify and quantify phytochemicals. This research evaluated the antiglycation properties of Solanum Obtusifolium Dunal hydro-ethanolic extract by analyzing glycation progression across different stages. The in vitro assessment of the antihyperglycemic effect involved the enzymes α-amylase, α-glucosidase, and pancreatic lipase. The anti-inflammatory effect was demonstrated by the inhibition of protein denaturation and the stabilization of cell membranes. Computational studies, including ADME analysis and molecular docking, were also performed. HPLC-DAD analysis revealed the significant presence of quercetin, p-coumaric acid, catechin, and gallic acid in the hydroethanolic extract from Solanum Obtusifolium Dunal fruit. In glycation assays, this extract exhibited targeted inhibitory effects at multiple levels. Additionally, it had a significant impact (p < 0.001) on the activity of α-amylase, α-glucosidase and pancreatic lipase enzymes in vitro. This extract also exhibited a protective effect against hemolysis and protein denaturation. The findings were supported by the presence of a significant amount of flavonoids and phenolic acids, identified through HPLC-DAD analysis, along with computational studies and molecular docking, which also confirmed that the molecules of this extract were not toxic according to ADMET testing.

ABSTRACT This study examines the linear and non‐linear effects of natural resource rents on health performance in 48 Sub‐Saharan African countries between 2000 and 2023. By employing the Driscoll–Kraay strategy to correct for cross‐sectional dependence and the IV‐GMM approach to address potential endogeneity, the analysis reveals a nuanced and robust inverted U‐shaped relationship between natural resource rents and health outcomes. Specifically, the results show that natural resources exert a positive linear effect at moderate levels, suggesting that resource revenues, when effectively mobilized, enhance health performance. However, the negative non‐linear effects highlight that over‐reliance on resource rents undermines sustainability, as volatility and misallocation erode the capacity of resource wealth to translate into long‐term improvements in population health. The robustness checks reinforce these findings across resource‐rich and resource‐poor countries, as well as among middle‐income economies, while differences emerge for low‐income economies where modest levels of resource rents remain insufficient to overcome the severe deficit in health infrastructure and institutional capacity. The disaggregation of resource types further reveals that oil, gas, coal, and forest rents are associated with health performance gains at moderate levels, though the non‐linear results confirm that higher dependence on any resource rent type eventually worsens health performance. Overall, the study highlights that policy design must establish frameworks that ensure natural resource wealth is converted into sustainable health improvements for populations across Sub‐Saharan Africa.

BackgroundHigh-risk (HR) human papillomavirus (HPV) infection remains a great concern in sub-Saharan Africa in men who have sex with men (MSM). The prevalence of anal shedding of HPV and associated risk factors was estimated for the first time in a cross-sectional observational study covering MSM living in N’Djamena, the capital city of Chad.MethodsMSM were recruited from the community in 21 sites in neighborhoods of 5 districts randomly selected in N’Djamena by respondent-driven sampling (RDS) method. Anal Collector V-Veil UP2™ device was used for anal canal self-sampling. Manual silica-extracted DNA was subjected for HPV detection and genotyping using BMRT Human Papillomavirus Genotyping Real Time PCR assay (Jiangsu Bioperfectus Technologies Co., Ltd., Taizhou, China). HIV serostatus was assessed using two rapid tests in series.ResultsA total of 70 MSM (mean age: 29.9 years; range, 18–50) were included. The overall acceptability to practice veil-based anal self-sampling was 95.9%. The usability of the veil collector device was high (92.3%), with easy understandable instructions for use and correct placement in the anal canal. Satisfaction questionnaire reported high overall feeling, intimacy respect and lack of shame. The majority of MSM (44/70, 62.8%) showed anal shedding of HPV DNA, with HR-HPV frequently detected (38,70, 54.3%), including HPV-33 (30/70, 42.9%) HPV-68 (16/70, 22.9%), HPV-18 (4/70, 5.7%), HPV-35 (3/70, 4.3%), HPV-58 (2/70, 2.9%), and HPV-45 (1/70, 1.4%). The distribution of genotypes in HR-HPV DNA-positive MSM revealed that HPV-33 (30/70; 42.9%) was the predominant genotype, followed by the HPV-68 (16/70; 22.9%), HPV-18 (4/70; 5.7%), HPV-35 (3/70; 4.3%), HPV-58 (2/70; 2.9%), and HPV-45, HPV-51 and HPV-56 (each type, 1/70;1.4%).Among all HPV detected, only 42 HPV (36.8%) were covered by Gardasil-9® vaccine, including the HR-HPV-33, −18, −58 and −45, and the low risk-HPV-6 (5.7%) and HPV-11 (1.4%). The majority of detected HPV were non-covered by Gardasil-9® vaccine (63.1%). Overall HIV prevalence was 5.7%.ConclusionsTaken together, these observations point the MSM population in N’Djamena as a very particular core group of HIV and HPV transmission. HIV prevalence was higher than that of general adult population, but limited to only one MSM of twenty. The RDS method of recruitment allowed to include MSM likely belonging to the same sexual network of HPV transmission leading to the selection of an atypical and specific profile of anal HPV distribution. The potential efficacy of HPV prophylactic vaccination in this population can be estimated at relatively weak.

Background: Methylene blue (BM), whose toxic effects are not immediately apparent, can, in the long term, cause damage to the cardiovascular, central nervous, dermatological, gastrointestinal, genitourinary, and haematological systems in humans. It is therefore essential to eliminate this dye from wastewater. Aims: The present study aims to investigate the elimination of methylene blue from water solution by adsorption on mesoporous silica. Study Design: This study was conducted using a batch method for the treatment of aqueous methylene blue solution through the adsorption technique. Place and Duration of Study: Département de Chimie, Université de N’Djamena, from August 2025 to October 2025. Methodology: This study aims to remove a synthetic dye, specifically methylene blue, using mesoporous silica (nanometer-sized amorphous silica) synthesised via a colloidal route. The adsorption technique is implemented by examining the influence of pH, temperature, and dye concentration under various experimental conditions. During the experiments, a fixed mass of adsorbent was introduced into different beakers containing 50 mL of the colored solution and then subjected to continuous stirring for 180 minutes at 25 °C. The effects of the experimental parameters on the adsorption process were also investigated in this work. Results: Synthesised SiO2 has a pHpzc of 7,57. An optimal pH of 8 was determined at 25 °C, resulting in 99.079% dye removal. Equilibrium was reached after 10 minutes of contact with a removal rate of 99.63%. With a mass of 40 mg of the adsorbent, 99.65% of the dye was removed. The Langmuir isotherm accurately describes the experimental data, while the pseudo-second-order kinetic model more precisely describes the adsorption behaviour. Conclusion: This mesoporous silica (SiO2) synthesised via a Mineral Sol is a promising candidate for the remediation of wastewater pollution.