Cartographier l’ontologie d’un territoire sur le web: Le cas de la Bolivie

International audienceUnder what conditions is it possible to define the identity of a territory on the Web? In this paper we explore the way entities with a clear-cut geographical existence (such as Bolivia) exist and are objectivized in a digital space like the Web. Our question is “should the mapping of a territorial entity on the Web and its traditional geographical representation converge?” In order to answer it, we set out an analysis which takes as its starting point the architecture of the Web, revolving around the notion of resource (objects identified on the Web). Therefrom, we conduct an anthropological analysis of the “modes of existence” (Etienne Souriau) of a country such as Bolivia on the Web. We use several digital methods in order to probe concrete examples of the networks of associations it elicits and show that, as a resource, its limits that are widely redefined on the Web, largely through the networks generated by online participation (blogs, commentaries, tweets, Wikipedia entries…). Bolivia can thence be described as a burgeoning, quite unstable, entity whose borders become rather imprecise. Yet, such a characterization also proves way more encompassing and richer than traditional (namely, geographic) ones.Quelle est l’identité d’un territoire sur le Web ? Dans cet article nous explorons les modes d’identification et d’objectivation d’entités (en l’occurrence, ici, un pays) ayant une existence géographique admise hors du Web. Il apparait que la Bolivie, en tant qu’objet identifié au moyen du Web, alimenté par des contenus participatifs (blogs, commentaires, tweets, articles Wikipédia, contenus structurées sur DBpedia, etc.), est une entité en devenir qui prolifère et non un référent stable aux bords nets. Grâce à cette hypothèse permettant de penser sérieusement l’existence à part entière d’une entité sur le Web, nous pouvons mener une enquête anthropologique à propos de ces deux modes d’existence (au sens d’Etienne Souriau) de l’entité Bolivie. La cartographie d’une entité territoriale sur le Web et sa cartographie géographique se recouvrent-elles ? Et selon quelles dimensions le cas échéant ? Nous verrons que la question à se poser sur le Web est avant tout une question d’échelles. Pour ce faire, nous repartirons des fondements de l’architecture du Web afin de déterminer comment faire varier les échelles sur le Web de manière à continuer à parler de la Bolivie (une entité une) tout en tenant compte de la prolifération des associations qu’elle tisse (une entité multiple) et ainsi enrichir notre appréhension de l’objet géographique Bolivie "hors" du Web (objet dont l’existence est néanmoins impactée par le Web selon des modalités à éclaircir)

Can shadowing mimic the QCD phase transition?

The directed flow of protons is studied in the quark-gluon string model as a function of the impact parameter for S+S and Pb+Pb reactions at 160 AGeV/c. A significant reduction of the directed flow in midrapidity range, which can lead to the development of the antiflow, is found due to the absorption of early emitted particles by massive spectators (shadowing effect). This effect can mimic the formation of the quark-gluon plasma (QGP). However, in the absorption scenario the antiflow is stronger for the system of light colliding nuclei than for the heavy ones, while in the case of the plasma creation the effect should be opposite.Comment: REVTEX, 11 pages, 5 figures embedded, accepted for publication in Physics Letters

Basin-scale, integrated observations of the early 21st century multiyear drought in southeast Australia

The Murray-Darling Basin in southeast Australia is experiencing one of the most severe droughts observed recently in the world, driven by several years of rainfall deficits and record high temperatures. This paper provides new basin‐scale observations of the multiyear drought, integrated to a degree rarely achieved on such a large scale, to assess the response of water resources and the severity of the drought. A combination of Gravity Recovery and Climate Experiment (GRACE) data with in situ and modeled hydrological data shows the propagation of the water deficit through the hydrological cycle and the rise of different types of drought. Our observations show the rapid drying of soil moisture and surface water storages, which reached near‐stationary low levels only ∼2 years after the onset of the drought in 2001, with a loss of ∼80 and ∼12 km3 between January 2001 and January 2003, respectively. The multiyear drought has led to the almost complete drying of surface water resources which account for most of the water used for irrigation and domestic purposes. High correlation between observed groundwater variations and GRACE data substantiates the persistent reduction in groundwater storage, with groundwater levels still declining 6 years after the onset of the drought (groundwater loss of ∼104 km3 between 2001 and 2007). The hydrological drought continues even though the region returned to average annual rainfall during 2007

Recovery of rapid water mass changes (RWMC) by Kalman filtering of GRACE observations

We demonstrate a new approach to recover water mass changes from GRACE satellite data at a daily temporal resolution. Such a product can be beneficial in monitoring extreme weather events that last a few days and are missing by conventional monthly GRACE data. The determination of the distribution of these water mass sources over networks of juxtaposed triangular tiles was made using Kalman Filtering (KF) of daily GRACE geopotential difference observations that were reduced for isolating the continental hydrology contribution of the measured gravity field. Geopotential differences were obtained from the along-track K-Band Range Rate (KBRR) measurements according to the method of energy integral. The recovery approach was validated by inverting synthetic GRACE geopotential differences simulated using GLDAS/WGHM global hydrology model outputs. Series of daily regional and global KF solutions were estimated from real GRACE KBRR data for the period 2003–2012. They provide a realistic description of hydrological fluxes at monthly time scales, which are consistent with classical spherical harmonics and mascons solutions provided by the GRACE official centers but also give an intra-month/daily continuity of these variations

Reconfigurations ontologiques dans les nouvelles constitutions politiques andines: Une analyse anthropologique

In recent years, Bolivia and Ecuador have been the scene of radical ontological turns induced by processes of building new political constitutions. For the fi rst time, collectives with animist, analogist and naturalist modes of identifi cation had to negotiate and conciliate their «worlds» and «natures». In this article we explore the mediating role of the nature-Pachamama in the Bolivian context and its power to integrate and reassemble successfully diverging perspectives and notions of being in a new national constitution.In recent years, Bolivia and Ecuador have been the scene of radical ontological turns induced by processes of building new political constitutions. For the fi rst time, collectives with animist, analogist and naturalist modes of identifi cation had to negotiate and conciliate their «worlds» and «natures». In this article we explore the mediating role of the nature-Pachamama in the Bolivian context and its power to integrate and reassemble successfully diverging perspectives and notions of being in a new national constitution.In recent years, Bolivia and Ecuador have been the scene of radical ontological turns induced by processes of building new political constitutions. For the fi rst time, collectives with animist, analogist and naturalist modes of identifi cation had to negotiate and conciliate their «worlds» and «natures». In this article we explore the mediating role of the nature-Pachamama in the Bolivian context and its power to integrate and reassemble successfully diverging perspectives and notions of being in a new national constitution

Constrained Regional Recovery of Continental Water Mass Time-variations from GRACE-based Geopotential Anomalies over South America

International audienceWe propose a ''constrained'' least-squares approach to estimate regional maps of equivalent-water heights by inverting GRACE-based potential anomalies at satellite altitude. According to the energy integral method, the anomalies of difference of geopotential between the two GRACE vehicles are derived from along-track K-Band Range-Rate (KBRR) residuals that correspond mainly to the continental water storage changes, once a priori known accelerations (i.e. static field, polar movements, atmosphere and ocean masses including tides) are removed during the orbit adjustment process. Newton's first law merely enables the Difference of Potential Anomalies from accurate KBRR data and the equivalent-water heights to be recovered. Spatial constraints versus spherical distance between elementary surface tiles are introduced to stabilize the linear system to cancel the effects of the north-south striping. Unlike the ''mascons'' approach, no basis of orthogonal functions (e.g., spherical harmonics) is used, so that the proposed regional method does not suffer from drawbacks related to any spectrum truncation. Time series of 10-day regional maps over South America for 2006-2009 also prove to be consistent with independent datasets, namely the outputs of hydrological models, ''mascons'' and global GRACE solutions

Continental Water Storage Changes Sensed by GRACE Satellite Gravimetry

Since its launch in March 2002, the Gravity Recovery And Climate Experiment (GRACE) mission has been mapping the time variations of the Earth’s gravity field with a precision of 2–3 cm in terms of geoid height at the surface resolution of 300–400 km. The unprecedented precision of this twin satellite system enables to detect tiny changes of gravity that are due to the water mass variations inside the fluid envelops of our planet. Once they are corrected from known gravitational contributions of the atmosphere and the oceans, the monthly and (bi)weekly GRACE solutions reveal the continental water storage redistributions, and mainly the dominant seasonal cycle in the largest drainage river basins such as Amazon, Congo, Mississippi. The potential differences measured between the twin GRACE satellites represent the sum of integrated surface waters (lakes and rivers), soil moisture, snow, ice and groundwater. Once they are inverted for estimating surface water mass densities, GRACE solutions are also used to establish the long-term mass balance of the ice sheets impacted by global warming, for quantifying the interannual variations of the major aquifers, as well as for surveying the hydrological signatures of intense meteorological events lasting a few days such as tropical hurricanes. This chapter describes GRACE gravity products and the different data processings used for mapping continental water storage variations, it also presents the most remarkable results concerning global continental hydrology and climate changes