Les territoires : une science impossible ?

International audienceA scientific project implies some unification on its scientific object. Territory can be defined as natural and social spatial unit in various dimensions, from local to global, and would require different approach. In fact internal connection nets are not necessarily similar than external relationship. Therefore scale change requires non linear correlations. Then a territorial analysis implies to put together two opposite logical pattern, when dealing with spatial features or with spatial processes. In one way, explanations for territorial forms require regressive causes (from the consequences to the origin), in the other way dynamic analysis uses mechanical causes (from the initial forces to the result). A third difficulty remains in the various temporalities, from very long term to historical remnants to present day evolutions. In fact territorial dynamics proceed though discontinuous evolution through shifting processes including postponed actions and complex retroactions.Le projet de science du territoire implique d'affronter trois difficultés au delà de la simple recherche documentaire : la dimension variée des unités spatiales envisagées entre des échelles micro-locales et des approches planétaires ; les systèmes de relations internes au territoire envisagé ne sont pas nécessairement de même nature que les réseaux d'interactions externes. L'étude de territoire met en oeuvre de démarches complexes voire contradictoires lorsqu'il s'agit de formes ou de processus : les unes relèvent de logiques régressives tandis que les autres s'inscrivent dans analyses progressives. Enfin l'intégration de temporalités différentes, continues ou discontinues, sur un même espace en évolution implique des raisonnements compliqués. Il s'agit de qui prendre en compte les réactions et rétroactions parfois différées, des dynamiques rapides et des évolutions très lentes. La complexité des interactions sur un territoire laisse donc une large place aux démarches empiriques

La géographie physique des années 1970 en France, entre occasions manquées et essais non transformés ?

La période allant de 1968 à 1981 correspond à des années cruciales pour la géographie physique en France, entre tradition et innovations. Au plan scientifique et sociétal, la géographie physique est en effet confrontée depuis 1950 à divers changements au plan des concepts et des théories, en particulier la double révolution de la systémique et de la quantification. Dans les années 1970 s’accélère la marche aux grands programmes internationaux, à la globalisation et à l’innovation technique. L’article discute des possibles raisons de fond d’une mutation inachevée de la géographie physique française, moins par manque de moyens matériels que du fait d’effectifs insuffisants pour porter le renouvellement des idées.The period from 1968 to 1981 is a crucial one in France for physical geography, between tradition and innovation. Since 1950, physical geography was confronted, scientifically and socially, to various changes in terms of concepts and theories, especially the dual revolution of systems theory and quantitative geography. In the 1970s there was an acceleration towards large international programs, globalisation and technological innovation. The paper discusses some fundamental reasons for the incomplete transformation of the French physical geography, less from lack of resources than as a result of an insufficient number of scholars to put forward the renewal of ideas

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer, studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory, a versatile observatory designed to address the Hot and Energetic Universe science theme, selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), it aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR, browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters. Finally we briefly discuss on the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, and touch on communication and outreach activities, the consortium organisation, and finally on the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. (abridged).Comment: 48 pages, 29 figures, Accepted for publication in Experimental Astronomy with minor editin

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory. Athena is a versatile observatory designed to address the Hot and Energetic Universe science theme, as selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), X-IFU aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over a hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR (i.e. in the course of its preliminary definition phase, so-called B1), browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters, such as the instrument efficiency, spectral resolution, energy scale knowledge, count rate capability, non X-ray background and target of opportunity efficiency. Finally, we briefly discuss the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, touch on communication and outreach activities, the consortium organisation and the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. The X-IFU will be provided by an international consortium led by France, The Netherlands and Italy, with ESA member state contributions from Belgium, Czech Republic, Finland, Germany, Poland, Spain, Switzerland, with additional contributions from the United States and Japan.The French contribution to X-IFU is funded by CNES, CNRS and CEA. This work has been also supported by ASI (Italian Space Agency) through the Contract 2019-27-HH.0, and by the ESA (European Space Agency) Core Technology Program (CTP) Contract No. 4000114932/15/NL/BW and the AREMBES - ESA CTP No.4000116655/16/NL/BW. This publication is part of grant RTI2018-096686-B-C21 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. This publication is part of grant RTI2018-096686-B-C21 and PID2020-115325GB-C31 funded by MCIN/AEI/10.13039/501100011033

La restauration de la continuité écologique au regard des aménagements historiques et des dynamiques passées. Trajectoire héritée de la Mérantaise (Yvelines-Essonne)

International audienc

La géographie physique des années 1970 en France, entre occasions manquées et essais non transformés ?

International audienceThe period from 1968 to 1981 is a crucial one in France for physical geography, between tradition and innovation. Since 1950, physical geography is facing scientifically and socially to various changes in terms of concepts and theories, especially the double revolution of system theory and quantitative geography. The 1970s have been the years of great international programs, globalisation and technological innovation. The paper aims to discuss some fundamental reasons of incomplete transformation of the French physical geography, less from lack of resources than as a result of insufficient number of scholars to put forward the renewal of ideas.La période allant de 1968 à 1981 correspond à des années cruciales pour la géographie physique en France, entre tradition et innovations. Au plan scientifique et sociétal, la géographie physique est en effet confrontée depuis 1950 à divers changements au plan des concepts et des théories, en particulier la double révolution de la systémique et de la quantification. Dans les années 1970 s’accélère la marche aux grands programmes internationaux, à la globalisation et à l’innovation technique. L’article discute des possibles raisons de fond d’une mutation inachevée de la géographie physique française, moins par manque de moyens matériels que du fait d’effectifs insuffisants pour porter le renouvellement des idées

Catalogue du musée de la ville de Pau ; Considérations sur les musées de province ; et Notice sur le musée de Pau / par Ch. Le Coeur,...

Appartient à l’ensemble documentaire : Aquit1Avec mode text

AGE ET MODALITES DE MISE EN PLACE DES RIVIERES DE PIERRES DU MASSIF DU MEZENC (VELAY ORIENTAL, SE DU MASSIF CENTRAL FRANÇAIS) ; PREMIERE APPROCHE

le n° de page correspond à la page de présentation du résumé du poster dans le fascicule des résumés du colloqueInternational audienceMany blockstreams occur in the Miocene volcanic area of Mont Mézenc, eastern Velay, SE Massif Central, France. They were supplied by frost-shattered exposures of lava-flow boundaries, phonolitic domes and other intrusions. These ‘rivers of rock’ are ribbons of chaotically upheaved blocks presenting an openwork structure, are 400 to 1100 m long and 20 to 200 m wide, and are today disconnected from the rock exposures that supplied the debris. Some occur on very low gradient slopes. The largest blockstreams offer evidence of compression ridges and post-depositional block subsidence. Their dynamics and age are not precisely known in the study area and they have been interpreted by default as Late Pleniglacial rock glaciers. Field observations (stratigraphic relations with other surficial deposits, topographic position, distance from bedrock source areas and from talwegs, structural context), however, indicate that the situation is more complex, with new implications for their age, origin and past dynamics. This reconnaissance study proposes a typology of blockstreams for the area. The base of the blockstreams remains inaccessible to direct observation but several ground-penetrating radar transects were carried out in order to map the topography at depth. Results show that the blocks fill gullies 5 to 15 m in depth. At the surface, a sharp textural transition with other slope deposits is clearly detected but the latter grade topographically to the surface of the blockstreams, not to the gullies beneath them. These cross-cutting relations provide a relative chronology not previously established in the case of blockstream deposits.La province volcanique miocène supérieur du Velay oriental (SE du Massif central français) compte, à l'échelle de tout le territoire français, une richesse incomparable en rivières de pierres alimentées par le démantèlement des reliefs volcaniques (rebords de coulées basaltiques à trachytiques et, surtout, dômes et intrusions phonolitiques). Ces langues de blocs métriques redressés en tous sens, sans matrice, déconnectées des amonts pourvoyeurs (gélifraction) et présentes sur des pentes très faibles sont ici d'origine et d'âge mal connus. Elles sont par défaut assimilées à d'anciens glaciers rocheux et rattachées au Pléniglaciaire supérieur (Valadas, 1983). Les observations de terrain (rapports stratigraphiques avec les autres formations, position dans la topographie, distance aux zones-source, contexte structural...), suggèrent cependant une plus grande diversité d'âge et d'origine. Les investigations préliminaires conduites avec l'objectif d'établir une typologie ont, entre autre, consisté à réaliser des profils GPR en travers de ces formations offrant peu de coupes, afin de connaître la morphologie qui les a accueillies ou canalisées. Les premiers résultats révèlent la présence de ravines relativement profondes (5 m à une quinzaine de mètres) alors qu'en surface la transition est nette mais en continuité topographique entre les rivières de pierres masquant ces ravines et les formations gélifluées à blocs couvrant le reste des versants