L’influence des dispositifs de médiation dans la structuration des pratiques culturelles. Le cas des correspondants du Centre Pompidou

Pour étudier la médiation comme projet, procédure et processus, l’article se propose d’étudier les effets de l’action déployée par les médiateurs en fondant l’analyse sur une référence empirique : celle des correspondants de Beaubourg pour les années 1970-1980. L’analyse des effets de l’action des médiateurs permet d’en découvrir la pluralité : effets d’incitation, effets d’identification, effets de régulation, effets de fidélisation, que l’on découvre être régulièrement à l’origine de la transformation, souvent sensible, de pratiques culturelles. Les dispositifs de médiation opèrent donc un pouvoir de structuration des pratiques en transformant des façons de vivre des relations à l’art, des expériences culturelles. La mise en évidence de la multiplicité des effets des actions développées par les médiateurs suggère qu’ils définissent la part invisible des politiques de la culture, part invisible qui s’explique par le pouvoir ignoré, parce que rarement étudié, de ces mêmes médiateurs.So as to study mediation as project, procedures and process, this article undertakes an empirical analysis of the effects of the action of mediators, via a case study of the correspondents of the Beaubourg in 1970-1980. This study reveals numerous effects of mediators’ actions. At the origin of the transformation of cultural practices one observes effects of encouragement, identification, regulation, and loyalty-building. These mechanisms of mediation have the power to structure practices and transform ways of living the relation to art and cultural experiences. Revelation of the multiple effects of actions undertaken by mediators suggests that they define an invisible portion of cultural policies, a dimension that is not seen because mediators’ power is ignored, being rarely studied

Le paradoxe de l’avènement d’un événement : la « fin de l’histoire » à l’épreuve de la chute du Mur

Cet article critique la rhétorique aporétique de la fin de l’histoire en posant le problème de l’irruption d’un événement, la chute du mur de Berlin, et de l’avènement concomitant du discours de la « fin de l’histoire ». Énigmatique est en effet la concomitance paradoxale de cet événement historique et de l’avènement d’un discours qui en nie la logique. L’avènement d’un tel syntagme trahit, en une figure proche du déni, l’existence même de ce qu’il semble vouloir nier : l’histoire. Or, en affirmant au contraire, et en actes, la puissance de celle-ci, l’événement de la chute du Mur rappelle plutôt l’inanité d’une conception prétendant prophétiser l’avènement de sa « fin ».This article critically examines the aporetic rhetoric of the end of history by posing the question of the sudden emergence of an event, the fall of the Berlin Wall, and of the concomitant advent of the discourse of the ‘end of history’. Indeed, the paradoxical concomitance of this historical event and of the discourse which denies its logic, is enigmatic. The advent of such a syntagm betrays, in a figure close to denial, the very existence of what it seems to want to deny: history. And yet, by affirming, on the contrary and in actions, the power of history, the event of the fall of the Wall reminds one of the futility, rather, of a conception claiming to prophesy the advent of its ‘end’

Nitrogen isotopic fractionation during abiotic synthesis of organic solid particles

The formation of organic compounds is generally assumed to result from abiotic processes in the Solar System, with the exception of biogenic organics on Earth. Nitrogen-bearing organics are of particular interest, notably for prebiotic perspectives but also for overall comprehension of organic formation in the young solar system and in planetary atmospheres. We have investigated abiotic synthesis of organics upon plasma discharge, with special attention to N isotope fractionation. Organic aerosols were synthesized from N2-CH4 and N2-CO gaseous mixtures using low-pressure plasma discharge experiments, aimed at simulating chemistry occurring in Titan s atmosphere and in the protosolar nebula, respectively. Nitrogen is efficiently incorporated into the synthesized solids, independently of the oxidation degree, of the N2 content of the starting gas mixture, and of the nitrogen speciation in the aerosols. The aerosols are depleted in 15N by 15-25 permil relative to the initial N2 gas, whatever the experimental setup is. Such an isotopic fractionation is attributed to mass-dependent kinetic effect(s). Nitrogen isotope fractionation upon electric discharge cannot account for the large N isotope variations observed among solar system objects and reservoirs. Extreme N isotope signatures in the solar system are more likely the result of self-shielding during N2 photodissociation, exotic effect during photodissociation of N2 and/or low temperature ion-molecule isotope exchange. Kinetic N isotope fractionation may play a significant role in the Titan s atmosphere. We also suggest that the low delta15N values of Archaean organic matter are partly the result of abiotic synthesis of organics that occurred at that time

Convergence speed of a link-state protocol for IPv6 router autoconfiguration

This report presents a model for the NAP protocol, dedicated to the auto-configuration of IPv6 routers. If the auto-configuration of hosts is defined by IPv6 and mandatory, IPv6 routers still have to be manually configured. In order to succeed in new networking domains, a full auto-configuration feature must be offered. NAP offers a fully distributed solution that uses a link state OSPFv3-like approach to perform prefix collision detection and avoidance. In this report, we present a model for NAP and analyze the average and maximum autoconfiguration delay as a function of the network size and the prefix space size

Tree cover in Central Africa: Determinants and sensitivity under contrasted scenarios of global change

Tree cover is a key variable for ecosystem functioning, and is widely used to study tropical ecosystems. But its determinants and their relative importance are still a matter of debate, especially because most regional and global analyses have not considered the influence of agricultural practices. More information is urgently needed regarding how human practices influence vegetation structure. Here we focused in Central Africa, a region still subjected to traditional agricultural practices with a clear vegetation gradient. Using remote sensing data and global databases, we calibrated a Random Forest model to correlatively link tree cover with climatic, edaphic, fire and agricultural practices data. We showed that annual rainfall and accumulated water deficit were the main drivers of the distribution of tree cover and vegetation classes (defined by the modes of tree cover density), but agricultural practices, especially pastoralism, were also important in determining tree cover. We simulated future tree cover with our model using different scenarios of climate and land-use (agriculture and population) changes. Our simulations suggest that tree cover may respond differently regarding the type of scenarios, but land-use change was an important driver of vegetation change even able to counterbalance the effect of climate change in Central Africa. (Résumé d'auteur

Bilateral rhegmatogenous retinal detachment after external-beam radiotherapy: just a coincidence?

Purpose: To report an unusual case of almost simultaneous bilateral rhegmatogenous retinal detachment in the context of external-beam radiotherapy for a tumor at a non-ocular target site and in the absence of pre-existing ocular pathology. Methods: Observational case report with review of corresponding literature. Results: A 63-year-old man was referred for bilateral retinal detachment which was associated with many horseshoe tears and proliferative vitreoretinopathy. He had undergone surgery for a carcinoma of the left maxillary sinus 4 months prior to the presentation and had then received external-beam radiotherapy for 3 months. There was no familial history of retinal detachment and/or eye trauma in this hyperopic patient with clear native lenses. No chorioretinal pathology was apparent that could have predisposed the retinas to tearing. Conclusions: Simultaneous bilateral retinal detachment is exceptional, especially in a patient with no risk factors. The effect of radiotherapy on the vitreoretinal interface is discussed in the light of existing data and may have been responsible for our patient's retinal detachmen

Ocular manifestations in congenital toxoplasmosis

Background: Retinochoroiditis is the most common ocular manifestation of congenital toxoplasmosis, but other associated ophthalmological pathologies can also occur. The aim of this study was to determine the nature of the latter in treated cases of the disease and to assess their impact on visual function. Methods: Four hundred and thirty consecutive children with serologically confirmed congenital toxoplasmosis were included in this study. Data were prospectively collected using standardized ophthalmological assessment forms. The presence of retinochoroiditis and of associated pathologies was ascertained, and their impact on visual function was assessed. Results: After a median follow-up of 12 years [range 0.6-26 years], 130 children manifested retinochoroiditis. We detected 22 foci of retinochoroiditis at birth and 264 additional ones during the follow-up period. Of these, 48 (17%) were active when first diagnosed. Twenty-five of the 130 children (19%) had other associated ocular pathologies. Of these, 21 (16%) had a strabismus, which was due to macular lesions in 86% of the cases; 7 (5.4%) presented with unilateral microphthalmia, and 4 (3%) with cataracts. Most of these events were detected after the onset of retinochoroiditis. None of the children presented with ocular involvement in the absence of chorioretinal lesions. Macular lesions occurred more frequently in children with associated pathologies (p<0.0001), and associated pathologies were likewise more common in individuals with macular lesions (p=0.0003). Visual impairment occurred in 31/130 cases, and in all but 3 of these eyes it was due not to an associated pathology but to macular retinochoroiditis. Conclusions: At the end of the follow-up period, ocular involvement existed in 30% of the treated children with congenital toxoplasmosis. Associated eye pathologies were manifested less frequently than anticipated. They may occur later in life and are an indirect marker of the severity of congenital toxoplasmosis, but they do not have a direct impact on visual acuity. The overall functional prognosis of congenital toxoplasmosis is better than would be expected on the basis of literature findings, with only 2 of the 130 children suffering bilateral visual impairmen

Scanning Mobility Particle Sizer: Fast data Inversion and uncertainty analysis

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CAMPAGNE DE MESURE POUR UNE ÉTUDE DE L'EXPOSITION DE LA POPULATION FRANÇAISE AU CHAMP MAGNÉTIQUE 50 HZ

Longtemps considérés comme inoffensifs, les champs magnétiques (CM) alternatifs de fréquence 50 Hz liés à l'électricité en particulier, sont suspectés depuis une trentaine d'années d'être responsables de pathologies, notamment de leucémies chez l'enfant. Les dernières expertises collectives [1] ont conclu que la dernière grande interrogation en ce qui concerne les CM basse fréquence est l'association statistique observée dans plusieurs analyses conjointes entre l'augmentation du risque de leucémie de l'enfant et une exposition aux CM supérieure à 0,4 μT en valeur moyenne sur 24 heures