36 research outputs found
Genetic Variability and Its Implications on Early Generation Sorghum Lines Selection for Yield, Yield Contributing Traits, and Resistance to Sorghum Midge
Sorghum is the second most important cereal crop in Niger. The crop is grown in a wide range of ecological environments in the country. However, sorghum grain yield in Niger is limited by both abiotic and biotic constraints. Recombinant inbred lines derived from the cross of a local variety with a midge resistant variety and two local checks were evaluated during the 2015 rainy season across two planting dates in two environments in Niger. The objective was to investigate genetic variability for yield, yield related traits, and resistance to sorghum midge. High phenotypic coefficient of variation (PCV) versus genotypic coefficient of variation (GCV) was observed in both sites and planting dates. Across planting dates at both Konni and Maradi, grain yield, plant height, panicle weight, and midge damage had high heritability coupled with high estimates of genetic advance. At Konni, high genetic advance coupled with high heritability was detected for grain yield, plant height, panicle weight, and resistance to midge. There were similar results at Maradi for grain yield, plant height, and panicle weight. Therefore, selection might be successful for the above characters in their respective environments
P2 receptors in atherosclerosis and postangioplasty restenosis
Atherosclerosis is an immunoinflammatory process that involves complex interactions between the vessel wall and blood components and is thought to be initiated by endothelial dysfunction [Ross (Nature 362:801â09, 1993); Fuster et al. (N Engl J Med 326:242â50, 1992); Davies and Woolf (Br Heart J 69:S3âS11, 1993)]. Extracellular nucleotides that are released from a variety of arterial and blood cells [Di Virgilio and Solini (Br J Pharmacol 135:831â42, 2002)] can bind to P2 receptors and modulate proliferation and migration of smooth muscle cells (SMC), which are known to be involved in intimal hyperplasia that accompanies atherosclerosis and postangioplasty restenosis [Lafont et al. (Circ Res 76:996â002, 1995)]. In addition, P2 receptors mediate many other functions including platelet aggregation, leukocyte adherence, and arterial vasomotricity. A direct pathological role of P2 receptors is reinforced by recent evidence showing that upregulation and activation of P2Y2 receptors in rabbit arteries mediates intimal hyperplasia [Seye et al. (Circulation 106:2720â726, 2002)]. In addition, upregulation of functional P2Y receptors also has been demonstrated in the basilar artery of the rat double-hemorrhage model [Carpenter et al. (Stroke 32:516â22, 2001)] and in coronary artery of diabetic dyslipidemic pigs [Hill et al. (J Vasc Res 38:432â43, 2001)]. It has been proposed that upregulation of P2Y receptors may be a potential diagnostic indicator for the early stages of atherosclerosis [Elmaleh et al. (Proc Natl Acad Sci U S A 95:691â95, 1998)]. Therefore, particular effort must be made to understand the consequences of nucleotide release from cells in the cardiovascular system and the subsequent effects of P2 nucleotide receptor activation in blood vessels, which may reveal novel therapeutic strategies for atherosclerosis and restenosis after angioplasty
Mesure en laboratoire des échanges hydrauliques entre fracture et matrice et des couplages hydromécaniques associés dans le cas d'une roche gréseuse
International audienceThe experimental device of "3 S" laboratory, previously used to study thĂ© hydromechanical behaviour of individual fractures on thĂ© laboratory scale, was modified to also measure thĂ© flow through thĂ© porous matrix of thĂ© rock mass sample as well. The results of thĂ© 3 tests were analyzed by numerical modelling. The VIPLEF/HYDREF codes used take into account of thĂ© double porosity of thĂ© sample (fracture + rock matrix) and make it possible to precisely reproduce thĂ© hydromechanical loading. The analyses show that thĂ© relation between thĂ© hydraulic aperture of thĂ© fracture and mechanical closure strongly impacts thĂ© fracture flow rate prĂ©dictions. The rock matrix flow rate can also be slightly affected by thĂ© fracture hydraulic aperture. The realization of simultaneous measurements of fiows in both fracture and rock matrix should enable us to globally evaluate thĂ© conceptual approach used.Le dispositif expĂ©rimental du laboratoire "3 S", prĂ©cĂ©demment utilisĂ© pour Ă©tudier le comportement hydromĂ©canique des fractures Ă l'Ă©chelle du laboratoire, a Ă©tĂ© modifiĂ© pour mesurer Ă©galement le dĂ©bit Ă travers la matrice poreuse de l'Ă©chantillon de roche. Les rĂ©sultats des 3 essais ont Ă©tĂ© analysĂ©s par modĂ©lisation numĂ©rique. Les codes VIPLEF/HYDREF utilisĂ©s tiennent compte de la double porositĂ© de l'Ă©chantillon (fracture + matrice) et permettent de reproduire avec prĂ©cision le chargement hydromĂ©canique imposĂ©. Les analyses montrent que la relation entre l'ouverture hydraulique de la fracture et la fermeture mĂ©canique affecte fortement le dĂ©bit simulĂ© dans la fracture. Les Ă©coulements dans la matrice peuvent Ă©galement ĂȘtre lĂ©gĂšrement affectĂ©s par l'ouverture hydraulique de la fracture. La rĂ©alisation de mesures simultanĂ©es des dĂ©bits dans la fracture et la matrice devrait, Ă terme, permettre une Ă©valuation globale de l'approche conceptuelle utilisĂ©e
Modélisation des affaissements miniers : influence des tailles
International audienceKnowledge of subsidence engineering is of considerable importance to the planning and development of surface. Subsidence is generally associated with the extraction of minerals and natural resources such as oil, gas and water
Genetic diversity and comparison of diagnostic tests for characterization of footâandâmouth disease virus strains from Pakistan 2008â2012
Clustering mesoscale convective systems with laser-based water vapor delta O-18 monitoring in Niamey (Niger)
The isotopic composition of surface water vapor (delta(v)) has been measured continuously in Niamey along with the isotopic composition of event-based precipitation (delta(p)) since 2010. We investigate the evolution of water vapor and precipitation isotope ratios during rain events of the 2010, 2011, and 2012 monsoon periods. We establish a classification of rain systems into three types based on the delta(v) temporal evolution. We find that 51% of rain events (class A) exhibit a sharp decrease in delta O-18(v) in phase with the surface air temperature drop, leading to a depletion of water vapor by - 1.9% on average during rainfall. Twenty-nine percent of rain events (class B) show a similar decrease in delta O-18(v) in phase with the temperature drop but are characterized by a progressive enrichment of the vapor in the stratiform region, resulting in a depletion of water vapor by -1.2% on average during rainfall. The last 20% of the rain events (class C) are associated with a progressive increase in delta O-18(v) during rainfall (+0.8%). We also examine the temporal evolution of water vapor deuterium excess (d(v)) which shows a sharp increase as delta O-18(v) decreases, followed by a progressive decrease in the stratiform part for classes A and B. Using a basic box model, we examine for each class the respective roles that mesoscale subsidence and rain evaporation play on the evolution of delta O-18(v). We show that those two processes are dominant for class A, whereas other processes may exert a major role on delta O-18(v) for classes B and C
Les changements d'usage des sols et leurs conséquences hydro-géomorphologiques sur un bassin versant endoréique sahélien.
Les ressources naturelles des bassins-versants ruraux sahĂ©liens subissent depuis plusieurs dĂ©cennies une forte pression qui conduit Ă un changement radical de leur comportement hydro-gĂ©omorphologique. L'exemple est pris sur le bassin-versant du kori Dantiandou, bassin-versant endorĂ©ique de l'Ouest nigĂ©rien situĂ© Ă environ 70 kilomĂštres Ă l'est de Niamey (Niger). Il s'agit plus particuliĂšrement d'un de ses sous-bassins-versants, celui de Sama Dey (28,2 km 2 de superficie). Ce bassin-versant a connu de profondes mutations, avec entre autres, entre 1990 et 1999, une dĂ©gradation de la brousse tigrĂ©e sur les plateaux (- 4 %) et une diminution des jachĂšres (- 3 %) sur les terres de culture des glacis. La diminution du couvert vĂ©gĂ©tal entraĂźne la formation de surfaces encroĂtĂ©es (+ 12 %) gĂ©nĂ©ratrices de ruissellement et d'Ă©rosion sur des sols sableux Ă©oliens trĂšs fragiles. Sur les parcelles, le coefficient de ruissellement annuel moyen par rapport aux pluies totales est de 50,4 % sur croĂte d'Ă©rosion, contre 2,8 % sur champ de mil avec des pertes en terres moyennes annuelles respectivement de 56,6 t/ha et 2 t/ha. Le coefficient d'Ă©coulement annuel moyen est de 46 % Ă la station amont contre 26 % Ă la station aval. L'objectif de l'Ă©tude est de mettre en Ă©vidence le fonctionnement hydro-gĂ©omorphologique actuel avec comme facteur dĂ©terminant l'encroĂtement dĂ Ă la sensibilitĂ© des sols Ă la battance, phĂ©nomĂšne liĂ© aux changements d'usage des sols. L'approche mĂ©thodologique suivie a consistĂ© Ă effectuer des observations et un suivi du ruissellement et de l'Ă©rosion sur de petites parcelles (2006-2008), Ă mesurer les dĂ©bits liquides Ă deux stations de jaugeage Ă l'aide d'un moulinet (2004-2008) et Ă cartographier l'Ă©volution de l'occupation des sols et des unitĂ©s morphopĂ©dologiques. Comme rĂ©sultats significatifs on peut retenir que les facteurs dĂ©clenchants du ruissellement et de l'Ă©rosion sur la pĂ©riode choisie sont, par ordre d'importance, les propriĂ©tĂ©s des sols, notamment leur sensibilitĂ© Ă la battance, l'occupation des sols, et la pente
Runoff evolution according to land use change in a small Sahelian catchment
International audienceSignificant land use changes have been observed in West Africa, particularly in the Sahel region where climatic and demographic factors have led to a rise in cultivated areas, in recent decades. These changes caused strong modifications in the water cycle and in river regimes. 5 By comparing the rainfall-runoff relationships for two periods (1991-1994 and 2004-2010) in two small neighbouring catchments (approx. 0.1 km 2 each) of the Sahel, this study highlights the different hydrological consequences of land use change, particularly vegetation clearing and the consequent degradation of topsoil. Runoff increased in the upper basin, while it decreased in the lower basin, due to a 10 strong increase in in-channel infiltration. Flood peak durations have become shorter in the downstream part of the catchment due to the huge increase of runoff water transmission losses within the gullies. Further study will consist of equipping one of the catchments with anti-erosion devices (mainly "half-moons" and terraces) in order to evaluate the influence of anti-15 erosion devices on runoff and suspended load
Runoff evolution due to land-use change in a small Sahelian catchment
International audienceLand-use changes have been significant these last decades in West Africa, particularly in the Sahel region; in this area, climatic and demographic factors have led to a rise in cropped areas in recent decades causing strong changes in the water cycle and in river regimes. This study compares the rainfall-runoff relationships for two periods (1991-1994 and 2004-2011) in two small and similar neighbouring Sahelian catchments (approx 0.1 km(2) each). This allows identification of the different hydrological consequences of land-use/land-cover change, particularly the fallow shortening and the consequent degradation of topsoil. The main land surface change is a 75% increase in crusted soil area. Runoff increased by more than 20% on average between the two periods while flood duration decreased by 50% on average. However, runoff values remained largely constant in the lower part of the northern basin due to a strong increase in in-channel infiltration