Contribution of ETM+ images and GIS for detecting dynamic changes in the steppe area of Naâma, Algeria

Ce travail met en évidence l’apport des images Landsat pour le suivi dynamique de l’espace steppique dans une aride  (Algérie). L’analyse qualitative et quantitative de l’évolution rapide du paysage et plus particulièrement l’évolution de l’ensablement dans les communes s’avère intéressante dans la mesure où elle permet de dresser un bilan provisoire sur l’état actuel de la zone d’étude. Pour l’analyse, les changements de l’état de surface intervenus entre 1957 et 2002 extraient à partir des images MSS, TM et ETM+ de Landsat ont été retenus. Dès lors, trois méthodes de détections des changements (identification rapide et quantification de l’évolution des changements, technique de la composition colorée diachronique et la méthode indice dynamique de couverture des sols) ont été utilisées afin de localiser les différentes zones qui ont subi des mutations profondes et plus particulièrement l’extension de l’ensablement et la dégradation des sols à l’intérieur des contrées de la wilaya de Naâma. Il est important de noter que nous nous sommes basés sur  le modèle d’Olsson (1994)  pour les corrections atmosphériques des images. La zone concernée par cette étude fait partie des hautes plaines oranaises. Elle se rattache administrativement à la wilaya de Naâma. Elle s’étend sur une superficie de 29 825 km2, entre 32°08’ et 34°16’ de latitude nord et 0°09’ et 1°43’ de longitude ouest. L’utilisation des données de télédétection au travers de l’indice dynamique de couverture des sols et de la composition colorée diachronique a permis de mettre en évidence les différents changements qui ont eu lieu de 1987 à 2002. Ces changements concernant les mutations des unités paysagères en zone steppique ont nécessité de tester plusieurs indices de changement (indice de végétation, indice de brillance, indice de curasse et l’analyse en composante en principale) afin de minimiser les erreurs sur l’appréciation des résultats sur les changements. En effet, ces différents traitements ont révélé que pour l’ensemble de la région d’étude, la surface des espaces ensablés est passée de 1,38 % en 1957 à 42,9 % en 2002, soit une superficie de 1 280 762 ha; ce qui correspond à une extension de 28 461,4 ha par an.  Mots clés: Dégradation, Détection de changement, Ensablement, Télédétection, Naâma, AlgérieIn this work we propose to highlight the Landsat images contribution for the dynamic monitoring of steppe area. We retained for our analysis, the changes  in the soil surface state occurred since 1957 up to 2002 from MSS, TM and ETM+ images of Landsat. From that time on, three methods of detection of changes were used so as to locate the various areas, which are affected, by a major changes and the sanding up extension inside the studied area of the department of Naâma. These images of Landsat showed an alarming of the sand extension.  Indeed, this analysis revealed that for the all the studied area, the sanding up of space surface passed from 1.38 % in 1957 to 42.9 % in 2002, that is a surface of 1 280 762 ha; what corresponds to an extension of 28 461.4 ha per year. Keywords:  change detection, sanding Up, remote sensing, Naâm

Conséquences de l’évolution de l’occupation des sols sur les lacs et les rivières d’un bassin versant de moyenne montagne: application au bassin versant de l’Ain (France)

The Ain river – tributary of the Rhone, is distinguished by a geological and geomorphological duality splitting it into two very clear parts: the mountainous (karstic-jura mountains) and the low alluvial valley of the Ain river, characterized by agricultural land use. The geographical boundary between the two zones is the dam of Vouglans (3rd water reserve of France). These geological differences give rise to two types of reserves: karstic reserves at the top of the watershed and an alluvial water table enclosed in the quaternary alluvium at the bottom. The last thirty years have been marked by the massive exodus of the rural populations of the Haut, which maintained a pastoral activity for the valleys holding most of the industries. A renewal of pastoral areas by mainly coniferous and deciduous forests, particularly in the upper part of the catchment area (Jura), reflects this phenomenon of exodus. This process was accompanied by an increase in the input of organic matter and marked deoxygenation of the deep (hypolimnion) levels of the water bodies, mostly located at the top. This physico-chemical manifestation is felt at the bottom in rivers and more particularly in the river Ain, one of the main tributaries of the Rhone. The management of water resources has been subjected to this geological and economic duality, giving rise to a SWMM (Scheme for Water Management and Management) based on the alluvial plain in the lower part of the watershed and the installation of numerous contracts of rivers on the affluent of the Ain in addition to the SWMM. One of the priority concerns of managers is the assessment of the extent of deoxygenation recorded in the plans to the rivers and especially its consequences on the lower rivers. The results of measurements and models applied show that the phenomenon is not very noticeable upstream and downstream of the Vouglans dam. Predictive simulations incorporating the GIEC recommendations (optimistic and pessimistic scenario) do not show a particular trend for 2050.The Ain river – tributary of the Rhone, is distinguished by a geological and geomorphological duality splitting it into two very clear parts: the mountainous (karstic-jura mountains) and the low alluvial valley of the Ain river, characterized by agricultural land use. The geographical boundary between the two zones is the dam of Vouglans (3rd water reserve of France). These geological differences give rise to two types of reserves: karstic reserves at the top of the watershed and an alluvial water table enclosed in the quaternary alluvium at the bottom. The last thirty years have been marked by the massive exodus of the rural populations of the Haut, which maintained a pastoral activity for the valleys holding most of the industries. A renewal of pastoral areas by mainly coniferous and deciduous forests, particularly in the upper part of the catchment area (Jura), reflects this phenomenon of exodus. This process was accompanied by an increase in the input of organic matter and marked deoxygenation of the deep (hypolimnion) levels of the water bodies, mostly located at the top. This physico-chemical manifestation is felt at the bottom in rivers and more particularly in the river Ain, one of the main tributaries of the Rhone. The management of water resources has been subjected to this geological and economic duality, giving rise to a SWMM (Scheme for Water Management and Management) based on the alluvial plain in the lower part of the watershed and the installation of numerous contracts of rivers on the affluent of the Ain in addition to the SWMM. One of the priority concerns of managers is the assessment of the extent of deoxygenation recorded in the plans to the rivers and especially its consequences on the lower rivers. The results of measurements and models applied show that the phenomenon is not very noticeable upstream and downstream of the Vouglans dam. Predictive simulations incorporating the GIEC recommendations (optimistic and pessimistic scenario) do not show a particular trend for 2050

MaxMin Linear Initialization for Fuzzy C-Means

International audienceClustering is an extensive research area in data science. The aim of clustering is to discover groups and to identify interesting patterns in datasets. Crisp (hard) clustering considers that each data point belongs to one and only one cluster. However, it is inadequate as some data points may belong to several clusters, as is the case in text categorization. Thus, we need more flexible clustering. Fuzzy clustering methods, where each data point can belong to several clusters, are an interesting alternative. Yet, seeding iterative fuzzy algorithms to achieve high quality clustering is an issue. In this paper, we propose a new linear and efficient initialization algorithm MaxMin Linear to deal with this problem. Then, we validate our theoretical results through extensive experiments on a variety of numerical real-world and artificial datasets. We also test several validity indices, including a new validity index that we propose, Transformed Standardized Fuzzy Difference (TSFD)

CB1 Antagonism Exerts Specific Molecular Effects on Visceral and Subcutaneous Fat and Reverses Liver Steatosis in Diet-Induced Obese Mice

International audienceThe beneficial effects of the inactivation of endocannabinoid system (ECS) by administration of antagonists of the cannabinoid receptor (CB) 1 on several pathological features associated with obesity is well demonstrated, but the relative contribution of central versus peripheral mechanisms is unclear. We examined the impact of CB1 antagonism on liver and adipose tissue lipid metabolism in a mouse model of diet-induced obesity. Mice were fed either with a standard diet or a high-sucrose high-fat (HSHF) diet for 19 weeks and then treated with the CB1-specific antagonist SR141716 (10 mg x kg(-1) x day(-1)) for 6 weeks. Treatment with SR141716 reduced fat mass, insulin levels, and liver triglycerides primarily increased by HSHF feeding. Serum adiponectin levels were restored after being reduced in HSHF mice. Gene expression of scavenger receptor class B type I and hepatic lipase was induced by CB1 blockade and associated with an increase in HDL-cholesteryl ether uptake. Concomitantly, the expression of CB1, which was strongly increased in the liver and adipose tissue of HSHF mice, was totally normalized by the treatment. Interestingly, in visceral but not subcutaneous fat, genes involved in transport, synthesis, oxidation, and release of fatty acids were upregulated by HSHF feeding, while this effect was counteracted by CB1 antagonism. A reduction in the CB1-mediated ECS activity in visceral fat is associated with a normalization of adipocyte metabolism, which may be a determining factor in the reversion of liver steatosis induced by treatment with SR141716