Analyse de la chaîne de valeur du matériel génétique bovin laitier au Sénégal

Ministry of Foreign Affairs, Finlan

Monitoring and Forecasting of Coastal Erosion in the Context of Climate Change in Saint Louis (Senegal)

Owing to its unique physical and socio-economic characteristics, the Saint Louis region stands out as one of the most susceptible areas in Senegal to the adverse impacts of coastal erosion. The dynamics of erosion in this region are significantly influenced by the Langue de Barbarie (LB), a sand spit formed at the mouth of the Senegal River. Initially, in 2003, a 4 m wide artificial breach was strategically introduced to mitigate flooding; however, sediment dynamics expanded it to 6 km by 2020, thereby affecting the entire region. This study delves into the coastline change of the LB, specifically divided into three zones (LB-1, LB-2, and LB-3), spanning the period from 1994 to 2042. Leveraging Geographic Information System (GIS) and remote sensing techniques, our investigation reveals that, prior to the breach’s creation, the average dynamic coastline rates in zones LB-1, LB-2, and LB-3 were estimated at 4.4, 5.9, and 4.4 m/year, respectively. Subsequent to the breach, these rates shifted to −1.2, 8.4, and −2.7 m/year, with the most significant erosion observed alongshore of LB-3 at −6.6 m/year during the period 2002–2012. Projecting into 2032, LB-1 and LB-3 are anticipated to experience erosion rates of −11.5 and −26.8 m/year, respectively, while the LB-2 records an estimated accretion rate of 8.41 m/year. Eroded areas are expected to total 571,458 m2, while accumulated areas are expected to total 67,191 m2. By 2042, zones LB-1, LB-2, and LB-3 are expected to experience erosion rates of −23 and −53.6 m/year, resulting in the erosion of 1,021,963 m2 and the accumulation of 94,930 m2 with a dynamic rate of 168.2 m/year in zone LB-3. These results have significant implications for solving the urgent issue of coastal erosion in LB. © 2024 by the authors

Faidherbia albida transpiration and canopy conductance in a reference agroforestry system of West Africa

Faidherbia albida is a fertilizer and forage woody species of agroforestry systems in semi-arid Africa., It is phreatophyte and shows reverse phenology (leafless in rainy season) what is expected to avoid competition for soil water with associated crops. Moreover, the root access to groundwater is assumed to prevent constraint on transpiration. However, the details of F. albida transpiration and canopy conductance under daily and seasonal conditions are poorly known. The on-farm study was conducted at Faidherbia-Flux station in the population-health-environment observatory of Niakhar, Senegal. Five mature trees were selected in the stand with a density of 6.9 tree ha-1. Sap flow, xylem and soil water content were continuously recorded over a complete year with meteorological variables and measurements of canopy phenology, leaf area index and leaf water potential. Maximal transpiration estimated from sap flow peaked around 210 L tree-1 day-1 in the early dry season (December) for an average tree (DBH of 48.5 cm and 260 m² of leaf area). The transpiration slowly decreased up to June before a sharp decrease following intense defoliation at the beginning of the rainy season in July. Predawn leaf water potential ranged between 0.25 in early dry season and 0.45 MPa in mid dry season, indicating a low water constraint. However, the reference canopy stomatal conductance per leaf area (at 1 kPa of air vapour pressure deficit, VPD) decreased from around 100 in early dry season to 50 mmol m-2s-1 in mid dry season suggesting a significant regulation. Moreover, in both case, the canopy stomatal conductance was highly sensitive to VPD with a 50% decrease at 3 kPa. This study provides new bases for transpiration modeling of Faidherbia albida in agroforestry parklands. It particularly suggests to also consider the influences of soil surface drying and air dryness on transpiration regulation of Faidherbia

More C uptake during the dry season? The case of a semi-arid agro-silvo-pastoral ecosystem dominated by Faidherbia albida, a tree with reverse phenology (Senegal)

Agro-silvo-pastoralism is a highly representative Land Use in Africa, often presented as a strategical option for ecological intensification of cropping systems towards food security and sovereignty. We set up a new long-term observatory (“Faidherbia-Flux”) to monitor and model microclimate, energy and C balance in Niakhar (central Senegal, rainfall ~ 500 mm), dominated by the multipurpose tree Faidherbia albida (12.5 m high; 7 tree ha-1; 5% canopy cover). Faidherbia is an attractive agroforestry tree species in order to partition fluxes, given that it is on leaf during the dry season (October-June) and defoliated during the wet season, just when crops take over. Pearl-millet and groundnut crops were conducted during the wet season, following annual rotation in a complex mixed mosaic of ca. 1 ha fields. Early 2018, we installed an eddy-covariance (EC) tower above the whole mosaic (EC1: 20 m high). A second EC system was displayed above the crop (EC2: 4.5 m if pearl-millet, 2.5 m if groundnut) in order to partition ecosystem EC fluxes between tree layer and crop+soil layers. Sap-flow was monitored from April 2019 onwards in 5 faidherbia trees (37 sensors). The ecosystem displayed moderate but significant daily CO2 and H2O fluxes during the dry season, when faidherbia (low canopy cover) was in leaf and the soil was evaporating. At the onset of the rainy season, the soil bursted a large amount of CO2. Just after the growth of pearl-millet in 2018, CO2 uptake by photosynthesis increased dramatically. However, this was largely compensated by high ecosystem respiration. Surprisingly in 2019, although the crop was turned to groundnut, the fluxes behaved pretty much the same as with pearl millet in 2018: comparing annual balances between 2018 and 2019 we obtained [454, 513] for rainfall (P: mm yr-1), [3500, 3486] for potential evapotranspiration (ETo: mm yr-1), [0.13, 0.15] for P/ETo, [470, 497] for actual evapotranspiration (E: mm yr-1), [2809, 2785] for net radiation (Rn: MJ m-2 yr-1), [1686, 1645] for sensible heat flux (H: MJ m-2 yr-1), [-3.2, -2.8] for net ecosystem exchange of C (NEE: tC ha-1 yr-1), [-11.8, -11.1] for gross primary productivity (GPP: tC ha-1 yr-1) and [8.6, 8.3] for ecosystem respiration (Re: tC ha-1 yr-1). The energy balance (Rn-H-LE) was nearly nil indicating that the EC system behaved reasonably. E was very close to P, indicating that little or no water would recharge the deep soil layers.Now comparing the dry (2/3 of the year) and wet (1/3) seasons: surprisingly, NEE was more effective during the dry season [-3.9, -1.7]. This was the result of Re being much lower on a daily basis as well as cumulated over the entire seasons [57, 84], whereas GPP was similar [-10.8, -12.1]. We found a good match between E measured above the whole ecosystem (EC1), and the sum of tree transpiration (T, measured by sapflow) + E measured just above crops + soil (EC2) throughout the wet and dry seasons. The “Faidherbia-Flux” observatory is registered in FLUXNET as SN-Nkr and is widely open for collaboration

Autoantibodies against type I IFNs in patients with life-threatening COVID-19

Interindividual clinical variability in the course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is vast. We report that at least 101 of 987 patients with life-threatening coronavirus disease 2019 (COVID-19) pneumonia had neutralizing immunoglobulin G (IgG) autoantibodies (auto-Abs) against interferon-w (IFN-w) (13 patients), against the 13 types of IFN-a (36), or against both (52) at the onset of critical disease; a few also had auto-Abs against the other three type I IFNs. The auto-Abs neutralize the ability of the corresponding type I IFNs to block SARS-CoV-2 infection in vitro. These auto-Abs were not found in 663 individuals with asymptomatic or mild SARS-CoV-2 infection and were present in only 4 of 1227 healthy individuals. Patients with auto-Abs were aged 25 to 87 years and 95 of the 101 were men. A B cell autoimmune phenocopy of inborn errors of type I IFN immunity accounts for life-threatening COVID-19 pneumonia in at least 2.6% of women and 12.5% of men

NUMERICAL STUDY OF DROPLET FORMATION IN A Y-JUNCTION MICROCHANNEL

This study investigates the formation process of droplets in a Y-junction microchannel using two immiscible fluids: water as the continuous fluid and oil as the dispersed phase. We have examined the influence of the capillary number, flow rate ratio and viscosity ratio between the two fluids; parameters which determine the length and generation frequency of the droplets. Numerical simulations have been performed using the software Ansys Fluent with the interface capture method Volume of Fluid (VOF) for solving the governing equations. Three different algorithms have been tested for the pressure-velocity coupling: SIMPLE, SIMPLEC and PISO. The results are quite similar for SIMPLE and SIMPLEC, however it turned out that PISO is a better algorithm to solve the two-phase flow. Additionally, another Y-junction is coupled in the initial geometry to observe a symmetric breakup of the droplets and their formation is explained using the pressure field and the velocity field

Tiques et hémoparasitoses du bétail au Sénégal. V. La zone Nord-guinéenne

Les auteurs rapportent les résultats d'une étude sur les tiques et les hémoparasitoses des bovins, des ovins et des caprins de la zone nord-guinéenne. Un détiquage systématique de 40 bovins, 40 moutons et 40 chèvres est effectué pendant 15 mois dans le but de déterminer la dynamique des populations et de préciser les sites préférentiels de fixation des différentes espèces suivantes récoltées sur ces animaux : Amblyomma variegatum, Boophilus geigyi, Hyalomma truncatum, H. marginatum rufipes, Rhipicephalus sulcatus, Rh. senegalensis, Rh. lunulatus. Des études sont menées simultanément sur les hémoparasitoses par réalisation de frottis de sang et de splénectomies. Chez les bovins, sont mis en évidence : Anaplasma marginale, Ehrlichia bovis, Trypanosoma vivax, Theileria mutans, Theileria velifera. Les infections décelées chez les petits ruminants sont occasionnées par Anaplasma ovis, Ehrlichia ovina, Trypanosoma congolense, Theileria ovis. Les valeurs de l'hématocrite d'animaux apparemment sains sont étudiées, de même que les variations saisonnières de ce paramètre hématologique.</jats:p