Modèle hydrologique basé sur le principe de moindre action (Modhypma)

Il existe dans la littérature hydrologique un grand nombre de modèles pluie-débit conceptuels ou empiriques globaux mais le nombre élevé de paramètres libres, combiné au manque ou à l’insuffisance de données de mesures sur le terrain, rendent leur prédiction incertaine. Les modèles physiques basés sur les lois de conservation sont encore plus exigeants en qualité et quantité de données. Dans cette étude, le développement et l’application du modèle Hydrologique basé sur le Principe de Moindre Action (ModHyPMA) est proposé. A partir des lois habituelles de conservation de masse et de conservation de la quantité de mouvement que l’on rencontre dans les études hydrologiques, nous avons introduit un " lagrangien hydrologique" et une fonctionnelle d’action propre au modèle proposé. L’application de ce modèle est faite dans le cadre de l’étude du bassin de l’Ouémé à la station de Bétérou (Bénin). Les différents critères numériques de performance calculés au calage et à la validation sont présentés. La comparaison des résultats du nouveau modèle à ceux du GR4J montre que le modèle basé sur le principe de moindre action constitue un outil prometteur à la fois pour l’approfondissement des bases physiques des modèles pluie-débit et pour la planification et la gestion des ressources en eau. Mots clés : ModHyPMA ; modèle pluie-débit ; paramètre d’échelle

Fractal analysis of rainfall occurrence observed in the synoptic stations of Benin (west Africa)

Fractal analysis is important for characterizing and modeling rainfall’s space-time variations in hydrology. The purpose of this study consists on determining, in a mono-fractal framework, the scale invariance of rainfall series in Benin synopticstations located in two main geographical area: Cotonou, Bohicon , Savè in a sub equatorial climate and Parakou, Natitingou, Kandi in a Sudanian climate. Daily rainfall data for 1963 to 2008 have been used. It’s provided by the Agency for the Aerial Navigation’s Security in Africa and Madagascar. This study characterizes, for the first time in Benin, the rainfall occurrence using fractal’s theories. Box counting method permits us to determine the fractal dimension (Dƒ) of the support. Afterward, a sensitivity analysis of the previously estimated fractal dimension is performed by varying the series length, as well as, the intensity threshold for the detection of rain. The results show that, the fractal dimension of the rainfall field depends strongly on: (i) the intensity threshold for the detection of rain fixed and (ii) the geographical position of the stations. The fractal dimension of these stations decreases with the increasing values of the threshold and confers to the synoptic stations’ rainy field a multifractal character. Three main regimes of scale invariance are obtained from the stations whatever the values of detection threshold of rain chosen between 0 mm/ day and 50 mm/day. For example, in a null detection threshold of rain, the first regime of scale invariance is delimited from 1 day to 8 days (meso-scale) whatever the geographical position of the stations. The associated fractal dimension varies from 0.52 to 0.65, such as: D ƒ (Bohicon) < D ƒ (Cotonou) < D ƒ (Savè) < D ƒ (Parakou) < D ƒ (Kandi) < D ƒ (Natitingou). However the second regime of scale invariance is delimited from 8 days to 128 days (synoptic scale) for stations located in sub equatorial region with a fractal dimensions varying from 0.86 to 0.90 respectively as: D ƒ (Savè) < D ƒ (Bohicon) < D ƒ (Cotonou); in the Sudanian climate, the second regime is delimited from 8 days to 256 days (synoptic scale) for with a fractal dimensions varying from 0.81 to 0.87 respectively as: D ƒ (Kandi) < D ƒ(Parakou) < D ƒ (Natitingou). The last regime of scale invariance starts from 128 days to above for the stations located in sub equatorial area which are characterized by a fractal dimension equal to 1; it starts from 256 days to above for the stations located in the Sudanian area and characterized by a fractal dimension equal to 1. For successive sequences of sub-periods of different sizes (3 years, 9 years and 15 years), the variation of the fractal dimension (for meso-scale and synoptic-scale) is essentially the same regardless of the size of the sequence and the geographical position of the stations. The occurrence of daily rainfall on all the six synoptic stations of Benin has the same properties as those studied in different parts of the world under different climatic conditions. So they check the universal properties of the occurrence of rain.Keywords: Fractal dimension, rainfall time series, scale-invariance, on-off intermittency, mono-fractal, box counting method

Modeling climate change impact on inflow and hydropower generation of Nangbeto Dam in West Africa using multi-model CORDEX ensemble and ensemble machine learning

Climate change (CC) poses a threat to renewable hydropower, which continues to play a significant role in energy generation in West Africa (WA). Thus, the assessment of the impacts of climate change and climate variability on hydropower generation is critical for dam management. This study develops a framework based on ensemble climate models and ensemble machine learning methods to assess the projected impacts of CC on inflow to the reservoir and hydropower generation at the Nangbeto Hydropower plant in WA. Inflow to reservoir and energy generation for the future (2020–2099) is modeled using climate models output data from Coordinated Regional Downscaling Experiment to produce a publicly accessible hydropower dataset from 1980 to 2099. The bias-adjusted ensemble mean of eleven climate models for representative concentration pathways (RC4.5 and RCP8.5) are used. The added value of this approach is to use fewer input data (temperature and precipitation) while focusing on their lagged effect on inflow and energy. Generally, the model output strongly correlates with the observation (1986–2005) with a Pearson correlation of 0.86 for energy and 0.82 for inflow while the mean absolute error is 2.97% for energy and 9.73% for inflow. The results reveals that both inflow and energy simulated over the future periods (2020–2039, 2040–2059, 2060–2079, and 2080–2099) will decrease relative to the historical period (1986–2005) for both RCPs in the range of (2.5–20.5% and 1–8.5% for inflow and energy, respectively), at annual, monthly and seasonal time scales. Therefore, these results should be considered by decision-makers when assessing the best option for the energy mix development plan

Analysis of the temporal structure of the daily rainfall observed at upper Oueme valley catchment in northern of Benin (west Africa) during 1999-2012.

West African rainfall is characterized by a strong variability. In order to quantify the hydrological impacts of such variability, analysis of rainfall patterns is highly essential. This study aims to characterize the Sudanese rainfall, using a raingauge data set collected on the upper Oueme River catchment (Benin) between 1999 and 2012. In this study, we choose a homogeneous network of fourteen rain gauges divided into four zones in the catchment: zone A (Affon, Bori, Sonoumon, Tobre), zone B (Copargo, Djougou, Donga, Tebou), zone C (Dogue, Pelebina, Sarmanga), zone D (Beterou_C, Wewe, Koko). The analysis of the frequency distributions of daily rainfall revealed that 25% of rainy days give rainy heights greater than 15mm while 50% of rainy days occur with rainy heights less than 5mm. The frequency distribution of daily rainfall has been well modeled by Gamma and Weibull law. The seasonal cycle of daily rainfall in the study region is mono-modal. The analysis of the seasonal cycle indicated that its bandwidth is wider in the South than in the North of the region such as: bandwidth (zone A) = bandwidth (zone B) < bandwidth (zone C) < bandwidth (zone D). The results of this study will allow us to fully realize the monofractal analysis of the precipitations in this region.Keywords: Sudanese climate; precipitation; West Africa, seasonal cycle, Exponential, Gamma, Weibull model.RESUMELes précipitations en Afrique de l'Ouest sont caractérisées par une forte variabilité spatio-temporelle. Afin de quantifier les impacts hydrologiques de cette variabilité, l'analyse de la structure temporelle des précipitations est très essentielle. Cette étude vise à caractériser les précipitations soudanaises, en utilisant un ensemble de données recueillies sur le pluviomètre bassin versant supérieur du fleuve Ouémé (Bénin) entre 1999 et 2012. Dans cette étude, nous choisissons un réseau homogène de quatorze pluviomètres répartis en quatre zones dans le bassin versant : zone A (Affon, Bori, Sonoumon, Tobre), zone B (Copargo, Djougou, Donga, Tebou), la zone C (Dogue, Pelebina, Sarmanga), la zone D (Beterou_C, Wewe, Koko). L’analyse des distributions fréquentielles des pluies journalières a révélé que 25% des jours pluvieux donnent lieu à des cumuls supérieurs à 15mm. Cette distribution des cumuls journaliers a été bien modélisée par la loi gamma et la loi de weibull. Le cycle saisonnier des pluies journalières de la région est monomodal. Son analyse par zone a indiqué que sa bande passante est plus large au Sud qu’au Nord de la région : la bande passante (zone A) = bande passante (zone B) <bande passante (zone C) <bande passante (zone D). Les résultats de cette étude nous permettront de réaliser pleinement l'analyse de monofractal des précipitations dans cette région.Mots clés : Climat soudanien, précipitations, Afrique de l'Ouest, cycle saisonnier, exponentiel, modèle Gamma, Weibull

Antimalarial antibody repertoire defined by plasma IG proteomics and single B cell IG sequencing

Plasma antimalarial Ab can mediate antiparasite immunity but has not previously been characterized at the molecular level. Here, we develop an innovative strategy to characterize humoral responses by integrating profiles of plasma immunoglobulins (IGs) or Abs with those expressed on B cells as part of the B cell receptor. We applied this strategy to define plasma IG and to determine variable (V) gene usage after vaccination with the Plasmodium falciparum zygote antigen Pfs25. Using proteomic tools coupled with bulk immunosequencing data, we determined human antigen-binding fragment [F(ab′)2] peptide sequences from plasma IG of adults who received 4 doses of Pfs25-EPA/Alhydrogel. Specifically, Pfs25 antigen-specific F(ab′)2 peptides (Pfs25-IG) were aligned to cDNA sequences of IG heavy (IGH) chain complementarity determining region 3 from a data set generated by total peripheral B cell immunosequencing of the entire vaccinated population. IGHV4 was the most commonly identified IGHV subgroup of Pfs25-IG, a pattern that was corroborated by V heavy/V light chain sequencing of Pfs25-specific single B cells from 5 vaccinees and by matching plasma Pfs25-IG peptides and V-(D)-J sequences of Pfs25-specific single B cells from the same donor. Among 13 recombinant human mAbs generated from IG sequences of Pfs25-specific single B cells, a single IGHV4 mAb displayed strong neutralizing activity, reducing the number of P. falciparum oocysts in infected mosquitoes by more than 80% at 100 μg/mL. Our approach characterizes the human plasma Ab repertoire in response to the Pfs25-EPA/Alhydrogel vaccine and will be useful for studying circulating Abs in response to other vaccines as well as those induced during infections or autoimmune disorders

Phytochemical and nutritional properties of sumac (Rhus coriaria): a potential ingredient for developing functional foods

Sumac (Rhus coriaria) is a flowering plant that is widely consumed for its promoting health benefits and used in food preparations as a spice in the Mediterranean region. It is a high shrub or small tree with imparipinnate leaves, villus and red fruits with one-seeded drupe, and small greenish-white flowers. The nutraceutical and pharmaceutical potential of sumac makes it a remarkable functional food. In this review, the phytochemical and nutritional properties of sumac as an under valorized functional food have been discussed. Flavonoids, anthocyanins, phenolic acids, and organic acids have been reported as dominant phytochemicals in sumac, which are well known for their pharmacological properties that attract many consumers to commonly choose sumac in their diet as well as food preparations. The remarkable volatile compounds present in sumac give it a unique aroma that increases its acceptance by consumers and potential use in the food industry. Sumac has been evaluated for a broad range of nutritional and pharmacological activities such as antioxidant, antinociceptive, anti-inflammatory, anti-diabetic, hepatoprotective, cardioprotective, anticancer, anti-infertility, and neuroprotective potential. This review has also briefly outlined the safety concerns concerning the use of sumac in terms of toxicology and interactions

Antimalarial antibody repertoire defined by plasma IG proteomics and single B cell IG sequencing

Plasma antimalarial Ab can mediate antiparasite immunity but has not previously been characterized at the molecular level. Here, we develop an innovative strategy to characterize humoral responses by integrating profiles of plasma immunoglobulins (IGs) or Abs with those expressed on B cells as part of the B cell receptor. We applied this strategy to define plasma IG and to determine variable (V) gene usage after vaccination with the Plasmodium falciparum zygote antigen Pfs25. Using proteomic tools coupled with bulk immunosequencing data, we determined human antigen-binding fragment [F(ab′)2] peptide sequences from plasma IG of adults who received 4 doses of Pfs25-EPA/Alhydrogel. Specifically, Pfs25 antigen-specific F(ab′)2 peptides (Pfs25-IG) were aligned to cDNA sequences of IG heavy (IGH) chain complementarity determining region 3 from a data set generated by total peripheral B cell immunosequencing of the entire vaccinated population. IGHV4 was the most commonly identified IGHV subgroup of Pfs25-IG, a pattern that was corroborated by V heavy/V light chain sequencing of Pfs25-specific single B cells from 5 vaccinees and by matching plasma Pfs25-IG peptides and V-(D)-J sequences of Pfs25-specific single B cells from the same donor. Among 13 recombinant human mAbs generated from IG sequences of Pfs25-specific single B cells, a single IGHV4 mAb displayed strong neutralizing activity, reducing the number of P. falciparum oocysts in infected mosquitoes by more than 80% at 100 μg/mL. Our approach characterizes the human plasma Ab repertoire in response to the Pfs25-EPA/Alhydrogel vaccine and will be useful for studying circulating Abs in response to other vaccines as well as those induced during infections or autoimmune disorders