538 research outputs found
Variabilite climatique et hydrologique dans la basse vallee de l’Oueme a Bonou
No full textLes questions de la variabilité ou des changements climatiques et de leurs implications sur les écosystèmes naturels et sur les ressources en eau, sont de plus en plus placées au centre des grands débats scientifiques, politiques et de développement durable tant dans le monde qu’au Bénin. La présente étude vise à analyser la variabilité hydroclimatique et ses effets dans la basse vallée de l’Ouémé à Bonou. La démarche méthodologique s’est focalisée sur l’analyse des données climatologiques (Pluie) sur la période 1950 à 2010, (ETP) de 1965 à 2010 et les données hydrométriques (débits mensuels) sur la période 1950 à 2010. De même, les statistiques de la production agricole sont utilisées afin d’évaluer l’impact des événements pluviométriques et hydrologiques extrêmes sur la production agricole. Par ailleurs des observations directes ont été effectuées sur le terrain en période de crue. Il ressort de l’analyse des résultats que le secteur d’étude a non seulement connu une rupture de stationnarité autour les années 1970, mais aussi d’une baisse des précipitations de l’ordre de 15 à 20 % suivie d’une légère reprise de 2 % à la fin des années 1990. Ces fluctuations pluviométriques soumettent parfois les principales spéculations agricoles à des surplus d’eau dans les sols tout en les rendant plus vulnérables. De même, les crues exceptionnelles qui surviennent entraînent la destruction des cultures, et un déficit de la production agricole dans le milieu d’étude. En ce qui concerne les cours et plans d’eau existants cette situation engendre une dégradation du couvert végétal et accélère le phénomène d’érosion avec pour corollaires le drainage des particules solides et par conséquent le comblement du lit des cours d’eau. Face à cette situation, les populations développent plusieurs stratégies d’adaptation et de mitigation pour atténuer les impacts des pluies extrêmes dans le milieu d’étude.Mots clés: Basse vallée de l’Ouémé à Bonou, variabilité climatique, production agricole, écosystèmesEnglish AbstractMost of the research about variability and climate change and their implications for natural ecosystems and water resources are placed in the center of the great scientific debates, policies and sustainable development in the world and specially in Benin. This study aims at analyzing the hydroclimatic variability and its effects in the lower valley of Ouémé to Bonou. The methodology is focused on the analysis of climate data (rain) over the period 1950-2010 (ETP) from 1965 to 2010 and hydrometric data (monthly rates) over the period 1950 to 2010. The statistics of agricultural production are used to assess the impact of extreme rainfall and hydrological events on agricultural production. Also direct observations were made on the ground during floods. It appears from the analysis of the results that the study area has not only grown out of stationarity around the 1970 but, also a decrease in rainfall of 15 to 20% followed by a slight recovery 2% in the late 1990. These rainfall fluctuations may submit the main agricultural crops to water excess in the soil while making them more vulnerable. Exceptional floods that occur result in the destruction of crops, and a deficit of agricultural production in the sector of this study. According to lake and river this situation cause a degradation of vegetation cover and accelerates the erosion phenomenon with corollary the drainage of solid particles and therefore the filling the beds of streams. Faced with this situation, many people develop strategies for adaptation and mitigation to reduce the impacts of extreme rainfall in the middle of studyKeywords: Lower Valley Oueme to Bonou, climate variability, agricultural production, ecosyste
Mid-Century Climate Change Impacts on Ouémé River Discharge at Bonou Outlet (Benin)
No full textThis work focuses on impacts of climate change on Ouémé River discharge at Bonou outlet based on four global climate models (GCM) over Ouémé catchment from 1971 to 2050. Empirical quantile mapping method is used for bias correction of GCM. Furthermore, twenty-five rain gauges were selected among which are three synoptic stations. The semi-distributed model HEC-HMS (Hydrologic Modeling System from Hydrologic Engineering Center) is used to simulate runoff. As results, HEC-HMS showed ability to simulate runoff while taking into account land use and cover change. In fact, Kling–Gupta Efficiency (KGE) coefficient was 0.94 and 0.91 respectively in calibration and validation. Moreover, Ouémé River discharge is projected to decrease about 6.58 m3/s under Representative Concentration Pathways (RCP 4.5) while an insignificant increasing trend is found under RCP 8.5. Therefore, water resource management infrastructure, especially dam construction, has to be developed for water shortage prevention. In addition, it is essential to account for uncertainties when designing such sensitive infrastructure for flood management
Assessment of production and marketing constraints and value chain of sweet potato in the municipalities of Dangbo and Bonou
No full textAbstract Background Sweet potato [Ipomoea batatas (L.) Lam.] plays an important role in ensuring food security and incomes for local communities. It is particularly grown in southern region of Benin, and its production over the last few years has declined due to disease and severe pest infestation. Therefore, it was imperative to carry out this study to identify the main constraints related to the recent decline in sweet production and more specifically analyzing the production and marketing constraints of sweet potato in the townships of Dangbo and Bonou. Results The results of the survey revealed that many varieties of sweet potato were grown, mainly “Vobodouaho” (local name in Goun language), the most preferred variety by producers. Weedicides and insecticides were used to control weeds and insect pests, respectively. There was no efficient control methods against black rot, Alternaria blight, cylas spp., and caterpillar among the pathogens and insects that damaged sweet potato production in the study areas. The main constraints reducing sweet potato production in the townships of Dangbo and Bonou are: lack of adequate methods for controlling pest and diseases, lack of financial resources due to no access to credit, absence of modern equipment, scarcity and high cost of labor and absence of best methods for long-term storage. The average yield of sweet production per hectare ranged from 6.5 to 15.1 tons fresh matter/ha. The market value of sweet potato is still low at farmers’ level when compared to that of other stakeholders along the value chain. Conclusion This study calls for the attention of public and private sectors and policy makers for more investment in sweet potato research. Avenues for further research on sweet potato have also been suggested
Brachionus falcatus and Platyias patulus indicating organic pollution in Ouémé River's basin, Republic of Benin
No full textZooplankton is a biological compartment widely used in the bio-monitoring of aquatic ecosystems. It allows early detection of environmental disturbances even before reaching the upper compartments of interest to humans. The present study evaluated the ability of two rotifer species Brachionus falcatus and Platyias patulus to indicate organic pollution in the Ouémé River basin. Sampling was done between October 2014 and September 2015. Plankton net of 20 μm mesh size was used. Parameters such as NH4+, NO2- and PO43- were measured in water and used for the calculation of the Organic Pollution Index (IPO). The results showed that the occurrence of B. falcatus and P. patulus was 96.66% and 81.11%, respectively. Both species were particularly abundant in sites such as Kaboua and Vossa as well as downstream of the basin (Agonlin-lowé and Bonou). These strong abundances are linked to a very strong organic pollution in Kaboua and Vossa then to a high organic pollution at downstream. The least organically polluted station (Kpassa) had the lowest abundance of both species. B. falcatus and P. patulus are therefore two indicator species of organic pollution in the Ouémé River's basin in Benin
Myocardial Involvement in Rheumatic Disorders
No full textPurpose of Review: Autoimmune rheumatic diseases (ARDs) affect 8% of the population and approximately 78% of patients are women. Myocardial disease in ARDs is the endpoint of various pathophysiologic mechanisms including atherosclerosis, valvular disease, systemic, myocardial, and/or vascular inflammation, as well as myocardial ischemia and replacement/diffuse fibrosis. Recent Findings: The increased risk of CVD in ARDs leads to excess comorbidity not fully explained by traditional cardiovascular risk factors. It seems that the chronic inflammatory status typically seen in ARDs, promotes both the development of myocardial inflammation/fibrosis and the acceleration of atherosclerosis. Summary: CMR (cardio-vascular magnetic resonance) is the ideal imaging modality for the evaluation of cardiac involvement in patients with ARDs, as it can simultaneously assess cardiac function and characterize myocardial tissues with regard to oedema and fibrosis. Due to its high spatial resolution, CMR is capable of identifying various disease entities such as myocardial oedema /inflammation, subendocardial vasculitis and myocardial fibrosis, that are often missed by other imaging modalities, notably at an early stage of development. Although generally accepted guidelines about the application of CMR in ARDs have not yet been formulated, according to our experience and the available published literature, we recommend CMR in ARD patientS with new-onset heart failure (HF), arrhythmia, for treatment evaluation/change or if there is any mismatch between patient symptoms and routine non-invasive evaluation
Caractéristiques structurales et écologiques des populations de Antiaris toxicaria (Pers.) Lesch et de Ceiba pentandra (L.) Gaertn dans les forêts reliques du Sud-Benin
No full textCette étude des caractéristiques structurales et écologiques des populations de Antiaris toxicaria et Ceiba pentandra dans les forêts de Bonou et de Pobè (6°53’-6°58’ latitude Nord et 2°28’-2°41’ longitude Est)a permis de mettre en évidence leurs contraintes sylvicoles. Les données dendrométriques et écologiques ont été collectées sur les individus de populations de ces deux espèces dans 20 placeaux de 0,25 ha (50 m*50 m) installés dans ces forêts. Les résultats de notre étude indiquent que les populations de A. toxicaria présentent un bon renouvellement des individus dans la forêt de Bonou, alors qu’à Pobè, on observe une irrégularité de la régénération de l’espèce. Des mesures sylvicoles telles que l’enrichissement de la forêt de Pobè en A. toxicaria sont indispensables pour assurer la pérennité de l’espèce en forêt. Quant aux populations de C. pentandra dans les deux forêts, on remarque un problème de régénération de l’espèce caractérisé par la quasi absence desindividus de diamètres faibles (10 cm < dbh < 20 cm). Le renouvellement de cette espèce semble être compromis dans les deux forêts étudiées. Des mesures sylvicoles appropriées ont été proposées en vue d’assurer la gestion durable de ces espèces dans les forêts étudiées.Mots clés : Antiaris toxicaria, Ceiba pentandra, forêt de Bonou, forêt de Pobè, caractéristiques structurales,Bénin
under laboratory conditions: Perspectives for aquaculture
No full textMacrobrachium macrobrachion is an African native brackish river prawn with a high commercial value. Currently, there is little information on the post-larval production of this species. Two experiments were conducted in the laboratory to develop production techniques for this species. The first experiment analyzed the duration of yolk resorption and the second described the larval stages. Yolk resorption was studied in 240 newly hatched larvae for 24 h based on the reduction in yolk area over time. For larval development stages, six breeding tanks containing 100 L with a density of 50 larvae/L were used. Larvae were fed a combination of Artemia nauplii, Brachionusplicatilis, and pelleted food (Larviva ProStart, Biomar Efico). The results have shown that the area of yolk reserves varied significantly in the hours after hatching. At 14 h after hatching, each larva resorbed approximately 85% of its yolk reserve, and at 18 h after hatching, each of them still had approximately 6.1%. Twelve larval stages were identified and described in three critical stages. M. macrobrachion larvae are lecithotrophic and need to start exogenous feeding at 14 h at the earliest and 18 h at the latest after hatching. These results are the first to highlight the potential for mass production of brackish river prawns.Fil: Koussovi, Guillaume. National University of Agriculture; Benín. Gaston Berger University; SenegalFil: Houssou, Arsène Mathieu. National University of Agriculture; BenínFil: Daves, Dimas Armando Orés. National University of Agriculture; BenínFil: Niass, Farokh. Gaston Berger University; SenegalFil: Bonou, Clément Agossou. University of Abomey-Calavi; SenegalFil: Lopez, Laura Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Biología de la Reproducción y Crecimiento de Crustáceos Decápodos; ArgentinaFil: Montchowui, Elie. National University of Agriculture; Bení
Spatio-Temporal Trend of Past and Future Extreme Wave Climates in the Gulf of Guinea Driven by Climate Change
No full textThis study assessed the extremes of wave conditions for past (1979–2005) and future (2026–2045 and 2081–2100) time slices in the Gulf of Guinea (GoG). The ensemble produced from eight General Circulation Models under different Representative Concentration Pathway (RCP) emission scenarios (RCP4.5 and RCP8.5) was subjected to linear regression analysis and Mann–Kendal test for their trends and significance, respectively. Results showed an increase in the extreme of significant wave height (Hs) and mean wave period (Tm) between 1979–2005, 2026–2045, and 2081–2100 with few exceptions. The average values of annual and seasonal Hs and Tm range from 1.26–1.62 m and 10.37 s–10.86 s, respectively, for 1979–2005. These Hs values are projected to increase by 0.1 m (0.05 m) to 1.72 m (1.67 m) and the Tm will increase by 0.29 s (0.24 s) to 11.15 s (11.10 s) by the end of the century (mid-century) time slices, respectively. The mean wave direction (Dm) (201.89°–206.27°) showed an anticlockwise shift (−29.2 × 10−3 degrees per year) for 1979–2005 which is projected to become more southwesterly with an increase up to 2.2° (0.5°) by end (mid) century in 2100 (2045), respectively. Future work will be on the impacts of changing wave on longshore sediment transport along the GoG
Thrombus formation 10 years after placement of an atrial septal secundum defect closure device
No full textTHERMOPHYSICAL CHARACTERIZATION OF ECO-PLASTER MADE FROM GIANT SNAIL SHELLS
No full textInternational audienceThe main objective of this work is to carry out the thermophysical characterization of an eco-plaster made from giant snails shells Achatina Achatina. To achieve this, it was first synthesized eco-plaster from snail shells collected in nature. Thermal effusivity and conductivity measurements in transient mode and according to mixing rate , were then carried out with hot strip method. Finally, a thermal behavior study face to surface heating and cooling of specimens was carried out. The results obtained showed on one hand that thermal effusivity and conductivity respectively decrease from 555.386 J. m . K . s . to 377.736 J. m . K . s . and from 0.159 W. m . K to 0.104 W. m . K , when mixing rate increases from 1.8 to 2.7. In the same range of mixing rate, a comparative study showed on other hand, that density, thermal effusivity and conductivity of synthesized ecoplaster are lower than those of imported plaster. Surface heating tests with a constant heat flow for 180 s have shown that temperature rise is the same for both types of plaster up to 15 s in mixing rate range from 1.8 -2.7 and; up to 30 s for mixing rate of 3.6. Beyond 15 s and 30 s respectively for rates of 1.8 -2.7 and 3.6, we note that eco-plaster heats up faster than imported plaster. When heat flow is eliminated, we notice that the two plasters are cooled in same way
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