Usages de l'eau à Gaya (Niger) : entre fortes potentialités et contraintes majeures

Résumé: Le département de Gaya, cadre de notre étude, est situé au sud-ouest de la république du Niger. Il dispose d'un important potentiel hydrique composé des eaux de surface (une centaine de mares permanentes, le fleuve Niger sur 106 km) et de sept aquifères superposés comprenant des nappes de subsurface (affleurantes par endroit) et des nappes artésiennes. L'étude sur les usages de l'eau à Gaya a été menée à travers plusieurs axes centrés sur l'estimation et la répartition spatiale des ressources en eau, le cadre juridique et institutionnel régulant leur mise en valeur, les différents secteurs d'utilisation de l'eau ainsi que les contraintes affectant cette utilisation. L'usage de la cartographie à travers les SIG dans le traitement et l'analyse des données, couplée à notre expérience d'une dizaine d'année de travaux dans la région, a permis de dresser des synthèses richement illustrées permettant de mieux comprendre tous les enjeux liés à la problématique des usages de l'eau dans cette partie du Niger. Contrairement à la vision que l'on a traditionnellement du Sahel où le manque d'eau constitue une des contraintes majeures au développement, ici des conditions locales particulières contredisent ce cliché et transposent le débat sur un autre plan. Il s'agit de la maîtrise de l'eau au niveau local à travers l'élaboration d'une politique appropriée qui tienne compte non seulement des spécificités locales de la ressource, mais aussi des différents types d'usages. La politique de l'eau au Niger, définie selon le Schéma directeur de mise en valeur et de gestion des ressources en eau, à travers la mise en place d'un important arsenal juridique et institutionnel, a eu le mérite de tracer un canevas sur la question, mais a montré ses limites au niveau pratique après dix ans d'essai. En effet au niveau de Gaya, ni l'Etat ni les partenaires au développement (bailleurs de fonds extérieurs) n'ont tenu compte des caractéristiques locales de la ressource ou du contexte socioéconomique particulier de la région. Ce qui a entraîné la réalisation d'infrastructures inadaptées aux réalités hydrogéologiques locales ainsi que des choix inappropriés au niveau de certains aménagements. En dépit de l'abondance de la ressource, son accès tant au niveau quantitatif que qualitatif, reste difficile pour une grande partie des acteurs ruraux. Les différents handicaps rencontrés dans la mise en valeur des ressources en eau résultent de cette incohérence de la politique nationale de l'eau, mais aussi de la difficulté de son application sur le terrain où persiste un pluralisme juridique caractérisé par la cohabitation de deux systèmes de régulation à savoir les droits coutumiers et la législation moderne. Ces différents éléments mis en évidence dans cette étude sur la zone de Gaya pourraient servir de base pour un meilleur aménagement des ressources en eau dans le cadre plus large d'une politique d'aménagement du territoire prenant en compte tous les facteurs tant physiques que socioéconomiques de la région. Abstract: The department of Gaya, in which this study was done, is located in the SW area of the Republic of Niger. It has an important hydrological potential composed of surface water (approximately 100 permanent ponds, 106 km of the Niger River) and 7 bodies of underground water sources including sub-surface and artresan wells. This study of the exploitation of wtaer in Gaya has been carried out employing several parameters based on: the estimation and spacial distribution of water ressources, the juridic and institutional rules governing their utilisation and the various constraints affecting this exploitation. The use of mapping when treating and analysing data, coupled with ten years personel field experience, resulted in a richly illustrated synthesis of this data. This, in turn, led to a better comprehension of all the factors related to problems of water utilisation in this particular region of Niger. Contrary to the generally accepted view that the lack of water ressources is a major contributing factor to the lack of development in the Sahel, in Gaya the local conditions contradict this statement. In this region, and at the local level, the proper use of water is based on the elaboration of an appropriate policy which takes into account not only the local specifics of water ressources but the various types of water utilsation as well. Local use of water and water ressources are dependant on established rules. Water policy in Niger is defined by the General Schema based on an important institutional and judicary arsenal of rules and regulations. However, after a ten-year trial period, this system was shown to have its limitations. In Gaya, neither the State nor the development agencies took into consideration local characteristics nor the socio-economic context of the region. This, in turn, resulted in putting in place infrastructures that were not adapted to local hydrogeological realities as well as inappropriate choices in land planning and development. In spite of the abundance of water ressources, access to them remains difficult for most of the rural population. The various difficulties encountered are the result of incoherent water policies on a national level as well as the lack of practical application in this area. This is due to a double judicary system where two regulatory systems co-exist:traditional laws and modern legislation. the different elements brought out by this study could serve as a basis for a better utilisation of water ressources on a larger scale in which land planning and development policies would take into consideration all the physcial as well as the socio-economical factors of this region.

Clustering of grape yield maps to delineate site-specific management zones

Zonal management in vineyards requires the prior delineation of stable yield zones within the parcel. Among the different methodologies used for zone delineation, cluster analysis of yield data from several years is one of the possibilities cited in scientific literature. However, there exist reasonable doubts concerning the cluster algorithm to be used and the number of zones that have to be delineated within a field. In this paper two different cluster algorithms have been compared (k-means and fuzzy c-means) using the grape yield data corresponding to three successive years (2002, 2003 and 2004), for a ‘Pinot Noir’ vineyard parcel. Final choice of the most recommendable algorithm has been linked to obtaining a stable pattern of spatial yield distribution and to allowing for the delineation of compact and average sized areas. The general recommendation is to use reclassified maps of two clusters or yield classes (low yield zone and high yield zone) and, consequently, the site-specific vineyard management should be based on the prior delineation of just two different zones or sub-parcels. The two tested algorithms are good options for this purpose. However, the fuzzy c-means algorithm allows for a better zoning of the parcel, forming more compact areas and with more equilibrated zonal differences over time.

Spatially varying selection shapes life history clines among populations of Drosophila melanogaster from sub-Saharan Africa.

Clines in life history traits, presumably driven by spatially varying selection, are widespread. Major latitudinal clines have been observed, for example, in Drosophila melanogaster, an ancestrally tropical insect from Africa that has colonized temperate habitats on multiple continents. Yet, how geographic factors other than latitude, such as altitude or longitude, affect life history in this species remains poorly understood. Moreover, most previous work has been performed on derived European, American and Australian populations, but whether life history also varies predictably with geography in the ancestral Afro-tropical range has not been investigated systematically. Here, we have examined life history variation among populations of D. melanogaster from sub-Saharan Africa. Viability and reproductive diapause did not vary with geography, but body size increased with altitude, latitude and longitude. Early fecundity covaried positively with altitude and latitude, whereas lifespan showed the opposite trend. Examination of genetic variance-covariance matrices revealed geographic differentiation also in trade-off structure, and QST -FST analysis showed that life history differentiation among populations is likely shaped by selection. Together, our results suggest that geographic and/or climatic factors drive adaptive phenotypic differentiation among ancestral African populations and confirm the widely held notion that latitude and altitude represent parallel gradients.

Long-term continuous-flow left ventricular assist devices (LVAD) as bridge to heart transplantation.

Heart transplantation (HTx) is the treatment of choice for end-stage heart failure but the limited availability of heart's donors still represents a major issue. So long-term mechanical circulatory support (MCS) has been proposed as an alternative treatment option to assist patients scheduled on HTx waiting list bridging them for a variable time period to cardiac transplantation-the so-called bridge-to-transplantation (BTT) strategy. Nowadays approximately 90% of patients being considered for MCS receive a left ventricular assist device (LVAD). In fact, LVAD experienced several improvements in the last decade and the predominance of continuous-flow over pulsatile-flow technology has been evident since 2008. The aim of the present report is to give an overview of continuous-flow LVAD utilization in the specific setting of the BTT strategy taking into consideration the most representative articles of the scientific literature and focusing the attention on the evolution, clinical outcomes, relevant implications on the HTx strategy and future perspectives of the continuous-flow LVAD technology.

KLF2 mutation is the most frequent somatic change in splenic marginal zone lymphoma and identifies a subset with distinct genotype.

To characterise the genetics of splenic marginal zone lymphoma (SMZL), we performed whole exome sequencing of 16 cases and identified novel recurrent inactivating mutations in Kruppel-like factor 2 (KLF2), a gene whose deficiency was previously shown to cause splenic marginal zone hyperplasia in mice. KLF2 mutation was found in 40 (42%) of 96 SMZLs, but rarely in other B-cell lymphomas. The majority of KLF2 mutations were frameshift indels or nonsense changes, with missense mutations clustered in the C-terminal zinc finger domains. Functional assays showed that these mutations inactivated the ability of KLF2 to suppress NF-κB activation by TLR, BCR, BAFFR and TNFR signalling. Further extensive investigations revealed common and distinct genetic changes between SMZL with and without KLF2 mutation. IGHV1-2 rearrangement and 7q deletion were primarily seen in SMZL with KLF2 mutation, while MYD88 and TP53 mutations were nearly exclusively found in those without KLF2 mutation. NOTCH2, TRAF3, TNFAIP3 and CARD11 mutations were observed in SMZL both with and without KLF2 mutation. Taken together, KLF2 mutation is the most common genetic change in SMZL and identifies a subset with a distinct genotype characterised by multi-genetic changes. These different genetic changes may deregulate various signalling pathways and generate cooperative oncogenic properties, thereby contributing to lymphomagenesis.

Quaternary active tectonic structures in the offshore Bajo Segura basin (SE Iberian Peninsula Mediterranean Sea).

The Bajo Segura fault zone (BSFZ) is the northern terminal splay of the Eastern Betic shear zone (EBSZ), a large left-lateral strike-slip fault system of sigmoid geometry stretching more than 450 km from Alicante to Almería. The BSFZ extends from the onshore Bajo Segura basin further into the Mediterranean Sea and shows a moderate instrumental seismic activity characterized by small earthquakes. Nevertheless, the zone was affected by large historical earthquakes of which the largest was the 1829 Torrevieja earthquake (IEMS98 X). The onshore area of the BSFZ is marked by active transpressive structures (faults and folds), whereas the offshore area has been scarcely explored from the tectonic point of view. During the EVENT-SHELF cruise, a total of 10 high-resolution single-channel seismic sparker profiles were obtained along and across the offshore Bajo Segura basin. Analysis of these profiles resulted in (a) the identification of 6 Quaternary seismo-stratigraphic units bounded by five horizons corresponding to regional erosional surfaces related to global sea level lowstands; and (b) the mapping of the active sub-seafloor structures and their correlation with those described onshore. Moreover, the results suggest that the Bajo Segura blind thrust fault or the Torrevieja left-lateral strike-slip fault, with prolongation offshore, could be considered as the source of the 1829 Torrevieja earthquake. These data improve our understanding of present deformation along the BSFZ and provide new insights into the seismic hazard in the area.

Right ventricular dysfunction in children and adolescents conceived by assisted reproductive technologies.

Assisted reproductive technologies (ART) predispose the offspring to vascular dysfunction, arterial hypertension, and hypoxic pulmonary hypertension. Recently, cardiac remodeling and dysfunction during fetal and early postnatal life have been reported in offspring of ART, but it is not known whether these cardiac alterations persist later in life and whether confounding factors contribute to this problem. We, therefore, assessed cardiac function and pulmonary artery pressure by echocardiography in 54 healthy children conceived by ART (mean age 11.5 ± 2.4 yr) and 54 age-matched (12.2 ± 2.3 yr) and sex-matched control children. Because ART is often associated with low birth weight and prematurity, two potential confounders associated with cardiac dysfunction, only singletons born with normal birth weight at term were studied. Moreover, because cardiac remodeling in infants conceived by ART was observed in utero, a situation associated with increased right heart load, we also assessed cardiac function during high-altitude exposure, a condition associated with hypoxic pulmonary hypertension-induced right ventricular overload. We found that, while at low altitude cardiac morphometry and function was not different between children conceived by ART and control children, under the stressful conditions of high-altitude-induced pressure overload and hypoxia, larger right ventricular end-diastolic area and diastolic dysfunction (evidenced by lower E-wave tissue Doppler velocity and A-wave tissue Doppler velocity of the lateral tricuspid annulus) were detectable in children and adolescents conceived by ART. In conclusion, right ventricular dysfunction persists in children and adolescents conceived by ART. These cardiac alterations appear to be related to ART per se rather than to low birth weight or prematurity.

Exaggerated pulmonary hypertension and right ventricular dysfunction in high-altitude dwellers with patent foramen ovale.

BACKGROUND: There is considerable interindividual variability in pulmonary artery pressure among high-altitude (HA) dwellers, but the underlying mechanism is not known. At low altitude, a patent foramen ovale (PFO) is present in about 25% of the general population. Its prevalence is increased in clinical conditions associated with pulmonary hypertension and arterial hypoxemia, and it is thought to aggravate these problems. METHODS: We searched for a PFO (transesophageal echocardiography) in healthy HA dwellers (n = 22) and patients with chronic mountain sickness (n = 35) at 3,600 m above sea level and studied its effects (transthoracic echocardiography) on right ventricular (RV) function, pulmonary artery pressure, and vascular resistance at rest and during mild exercise (50 W), an intervention designed to further increase pulmonary artery pressure. RESULTS: The prevalence of PFO (32%) was similar to that reported in low-altitude populations and was not different in participants with and without chronic mountain sickness. Its presence was associated with RV enlargement at rest and an exaggerated increase in right-ventricular-to-right-atrial pressure gradient (25 ± 7 mm Hg vs 15 ± 9 mm Hg, P < .001) and a blunted increase in fractional area change of the right ventricle (3% [-1%, 5%] vs 7% [3%, 16%], P = .008) during mild exercise. CONCLUSIONS: These findings show, we believe for the first time, that although the prevalence of PFO is not increased in HA dwellers, its presence appears to facilitate pulmonary vasoconstriction and RV dysfunction during a mild physical effort frequently associated with daily activity. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT01182792; URL: www.clinicaltrials.gov.