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International audience; In this work, numerical simulations are carried out to characterize the impact of obstacles on flame propagation velocity to properly assess the consequences of Unconfined Vapor Cloud Explosions (UVCE).Within this scope, an UVCE within a congested environment is simulated using RANS modeling of the turbulence. Combustion phenomena are characterized through the progress variable transport equation. The simulation is done with the open source library OpenFoam. Numerical results are compared with data from the INERIS and GDF-SUEZ experimental campaign EXJET (hydrogen-air and methane-air explosions).

[Departement_IRSTEA]Eaux [TR1_IRSTEA]GEUSI [ADD1_IRSTEA]Gestion intégrée de la ressource et des infrastructures; International audience; The Rhône Valley Human-Environment Observatory (OHM) studies hydrosystem dynamics and riverine societies along the French Rhône river course. Since 2010, data centralization and diffusion have been structured within a SDI (Spatial Data Infrastructure) which has strengthened the interactions between scientists and practitioners.; L'Observatoire Hommes-Milieux (OHM) Vallée du Rhône appréhende les dynamiques de l'hydrosystème et des sociétés riveraines sur l'ensemble du Rhône français. Depuis sa création en 2010, la mutualisation et la valorisation des données produites ont été structurées dans une Infrastructure de Données Spatio-temporelles (IDS), ce qui a renforcé les interactions avec les acteurs territoriaux.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARE; International audience; The relation between hydrological connectivity and species diversity appears to be strong in natural habitats. Several ecological concepts revealed this marked link, such as the Intermediate Disturbance Hypothesis (IDH), a nonequilibrium model used to describe the relationship between disturbance and species diversity. The IDH has been supported by several studies which highlight that highest species diversity is maintained by intermediate levels of disturbance. However, can this hypothesis likewise be validated for artificial systems? Large European rivers were severely impacted by human activities, especially to promote navigation. We therefore tested the link between hydrological connectivity and diversity in these anthroposystems. During the 19th century, submersible dikes were built in the main channel of the Rhone River (France) delimiting dike fields. These could represent engineered backwaters, present a hydrological connectivity gradient and, hence could be used to test the IDH in an artificial context. We studied environmental and biological variables in 12 dike fields with different connectivity level in two locations of the lower Rhone, “Péage de Roussillon” and “Arles”. Our study reveals a high ecological variability among dike fields. Variations of abiotic factors, biodiversity, and functional diversity are strongly linked to the hydrological connectivity gradient. A higher diversity is observed in dike field with intermediate connectivity level compared to isolated or permanently connected dike fields. In these artificial systems, first results are in agreement with the IDH. Interaction between hydrological connectivity and diversity appears to well describe anthroposystems functioning and must be taken into account in rehabilitation of modified large rivers.; Les relations entre la connectivité hydrologique et la diversité spécifique sont fortes en milieu naturel. Plusieurs concepts écologiques ont révélés ces liens, comme la théorie de la perturbation intermédiaires (IDH), un modèle sans-équilibre utilisé pour décrire la relation entre perturbation et diversité spécifique. L'IDH a été étayée par de nombreuses études qui ont montré qu'une plus grande diversité est maintenue par des niveaux de perturbation intermédiaire. Néanmoins, est-ce que cette hypothèse peut-être validée pour des systèmes artificiels ? Les grands cours d'eau européens ont été fortement modifiés par les activités humaines notamment par la navigation. On a donc testé le lien entre la connectivité hydrologique et la diversité dans ces systèmes anthropiques. Durant le 19ème siècle, des digues submersibles ont été construites dans le chenal principal du Rhône (France) délimitant des casiers dit Girardon (du nom de l'auteur de ces structures). Elles peuvent représenter des bras morts artificiels qui présentent un gradient de connectivité et donc peuvent être utilisées pour tester l'IDH dans un contexte artificiel. Nous avons étudié des variables environnementales et biologiques de 12 casiers Girardon avec différents niveaux de connectivité, sur deux secteurs du Rhône : Péage de Roussillon et Arles. Notre étude révèle une forte variabilité écologique entre les casiers. La variabilité des facteurs abiotiques, de la biodiversité et de la diversité fonctionnelle sont fortement liés au gradient de connectivité hydrologique des casiers. Une plus forte diversité est observée dans les casiers avec des niveaux de connectivité intermédiaire comparé aux casiers isolés ou connectés en permanence. Dans ces milieux artificiels, les premiers résultats sont en accord avec l'IDH. L'interaction entre la connectivité hydrologique et la diversité est un bon descripteur du fonctionnement des systèmes et doit être prise en compte dans la réhabilitation des grands cours d'eau modifiés.

International audience

High-altitude lakes are vulnerable ecosystems that require protection and sustainability management, although their overallfunctioning is still poorly understood. In France protected area managers and scientists are cooperating to address this problem.Their results show the huge diversity of these altitude lakes and imply specificities in their functioning and in the way they respondto stressors. Multidisciplinary studies on these ecosystems, on their individual history and the stressors they face, need to be developedin a number of lakes, alongside long-term monitoring surveys. This is the objective of the Sentinel lakes network.

Ecological monitoring of the French Rhône River, around the nuclear power plant on the Montélimar dam (CNPE Cruas-Meysse), provides an estimate of interannual change in several physical-chemical and biological parameters (phytoplankton and benthic fauna). This study presents hydrobiological monitoring results since 2007, an integral part of the long-term time series data collected since the initial studies. Algae communities upstream and downstream from Cruas are mainly composed of diatoms, as in most European rivers. Since 2010, the proportion of Chlorophyceae and Cyanobacteria has been increasing. For benthic fauna, there has been a significant change in the population since 2004, with the appearance and settlement of more than ten exotic taxa, some of them invasive, such as the crustacean Amphipodes Dikerogammarus, or very abundant, such as Isopodes Jaera istri. Others show very considerable interannual variations in their abundance (Corophium, Hypania invalida, Hemimysis anomala), which is a sign that environmental conditions often change, in particular temperatures. Nevertheless, the population of native macroinvertebrates seems to have been declining sharply in recent years., La surveillance écologique du fleuve Rhône, au droit du Centre Nucléaire de Production Électrique (CNPE Cruas-Meysse) implanté sur la retenue de Montélimar, permet d'évaluer l'évolution interannuelle d'un certain nombre de paramètres physico-chimiques et biologiques (phytoplancton et faune benthique). Cette étude présente les résultats du suivi hydrobiologique depuis l’année 2007, partie intégrante de la chronique à long terme entreprise depuis les études initiales. Les communautés algales en amont et en aval de Cruas sont composées majoritairement de diatomées comme la plupart des fleuves européens. Depuis 2010, la proportion des Chlorophycées et des Cyanobactéries est en forte augmentation. Pour la faune benthique, un changement de peuplement est important depuis 2004, avec l’apparition et l’installation de plus d’une dizaine de taxons exotiques, certains devenus envahissants, comme les Crustacés Amphipodes Dikerogammarus, ou très abondants comme les Isopodes Jaera istri. D’autres ont des variations interannuelles d’abondances très importantes (Corophium, Hypania invalida, Hemimysis anomala), signes d’une forte variabilité des conditions environnementales, notamment thermiques. En revanche, les invertébrés autochtones semblent eux en forte régression depuis quelques années.

Chaoborus larvae are voracious predators of zooplankton able to change their specific composition and size structure. Thus they appear as competitors of fish. They also represent food for planktophage fish. The temporal dynamics of Chaoborus larvae was studied (from january to october 1997) in the fishery of Bakro (5°33’N and 3°15’W) situated in lake Ayamé I (Côte d’Ivoire). Two peaks of density were observed : the most pronouced in March (end of the major dry season) with 747 ind./m2, and another, less pronouced in June (end of the major rainy season), with 280 ind./m2. Differences between densities may well be explained by the advent of the rainy season which leads to a decline in trophic resources (zooplankton) and exposes Chaoborus larvae to predation by fish.Key-words : Chaoborus larvae, Dynamics, lake Ayamé I, Côte d’Ivoire,West Africa.

International audience; Aquatic fauna and flora of intermittent Mediterranean streams are adapted to predicable hydrological stress (biological and ecological traits). Mediterranean streams in southern France show a low-fl ow period of 4 months (usually from June to October). This period is characterised by: 1) the drought of the flowing aquatic habitats and 2) the persistence of cool perennial pools where lotic taxa can survive. Such predicable hydrological stress in classified as a press category perturbation. However, climate changes increased the drought period, leading to a less predicable constraint which can be classified as a ramp category perturbation. The main question of this study is to show the response of invertebrate communities to this increase of the dry period, due to less rainfall. This study shows the response of the invertebrate communities to a progressive period drought due to a year-scale lack of rainfall that occurred between 2002 and 2007. Invertebrate communities of the main-stem and perennial and intermittent flow tributaries were sampled over 5 years. The results show that cumulative decrease of the water discharge over the 5 years period 1) led to an overall biodiversity erosion 2) emphasized unexpected diffuse sources of pollution. At the catchment scale, intermittent tributaries harboured around 70 % of the taxa recorded in the catchment and thus play a major role in the biodiversity maintain in Mediterranean catchments, highly impacted by anthropogenic activities. Detailed examination of the catchment's hydrographical system and the preservation of intermittent water bodies should be an important part of the catchment management, and support the need for catchment-scale conservation of freshwater invertebrates

Le présent document marque un deuxième état d'avancement du programme MedAquaRive. Il fait état des différents bilans (chimie, biologie) in-situ effectués dans le réseau hydrographique du haut de l'Arc, et des résultats obtenus dans les essais d'évaluation toxicologique sur les algues et sur les macro-invertébrés benthiques. Compte tenu du contexte climatique régional, une partie des éléments exploités dans ce rapport font référence en majorité à données acquises pendant l'année hydrologique 2006-2007.

International audience; The taxonomic richness erosion and the role of tributaries in the maintenance of the taxonomic richness were considered in a Mediterranean catchment in southeastern France. Nine stations were chosen along the Arc stream (three stations downstream from an organic effluent and one station upstream from the pollution source) and on two groups of tributaries (three intermittent and two perennial). High biodiversity erosion was noticed in the main stem, revealing diffuse sources of pollution added to the expected effect of the localized organic pollution. Jackknife richness estimator and beta diversity indicated that the intermittent tributaries had the highest richness values and harboured 70% of the taxa recorded at the catchment scale. The intermittent flow tributaries seem to play a major role in maintaining the taxonomic richness in such catchments, highly impacted by anthropogenic activities. The detailed examination and the preservation of these ecosystems should be an important step in catchment management, and support the need for catchment-scale conservation of freshwater invertebrates.; L'érosion de la richesse taxinomique ainsi que le rôle des affluents temporaires dans le maintien de cette richesse taxinomique on été étudiés dans un petit bassin versant méditerranéen du Sud-Est de la France. Neuf stations d'études on été choisies le long de la rivière Arc (une station en amont de la station d'épuration de Trets et trois en aval), ainsi que sur deux types d'affluents (trois affluents temporaires et deux permanents). Une importante érosion de la richesse taxinomique a été observée le long de la rivière Arc, même dans la station située en amont de la source de pollution organique localisée ; ceci suggère l'existence de pollutions diffuses dans le bassin versant. L'estimation de la richesse par la méthode Jackknife ainsi que la diversité bêta montrent que les affluents temporaires abritent 70% des macroinvertébrés benthiques recensés dans cette partie du bassin versant. Ces affluents semblent jouer un rôle important dans le maintien de la richesse taxinomique dans ce type de bassin et plaide pour la conservation de la faune benthique d'invertébrés à l'échelle du bassin versant

Le présent document marque l'état d'avancement de l'étude MedAquaRive en 2006, qui fait suite aux bilans des actions Aquagest 2003-2004. Une continuité de suivis biologiques sur les stations du haut de l'Arc (cours d'eau principal et affluents) a été assurée. Les années hydrologiques 2004-2005 et 2005-2006 ont été des plus contraignantes pour la vie aquatique suite aux déficits de pluviosité. En chimie, les actions ont consisté à: (1) sélectionner des substances chimiques reflétant les activités agricoles et urbaines de cette zone, pesticides pour les premières et antibiotiques et désinfectants pour les secondes; (2) réaliser une campagne d'échantillonnage échelonnée de mi-mars à septembre; (3) développer et valider une méthodologie analytique pour le dosage de traces de substances antimicrobiennes (antibiotiques et désinfectants). Dans l'étude du fonctionnement hyporhéique, le plan d'échantillonnage sur 3 stations de l'Arc avait pour objectifs les relations hydrauliques entre les eaux de surface et les eaux de subsurface et l'estimation des activités des biofilms. En écologie algale, les actions ont porté sur la variabilité inter-stations de la biomasse épilithique (3 station sur l'Arc et 2 affluents); sur la comparaison des inventaires spécifiques 2003, 2004 et 2006 et sur la comparaison des abondances. En écologie des macro-invertébrés sur l'Arc, les résultats présentés concernent l'année 2005 aux trois stations de l'Arc. Sur les 4 affluents suivis, une synthèse qualitative sur une base IBGN a été réalisée depuis 2003; leurs peuplements globaux ont été discutés sur la base d'une analyse statistique prenant en compte les taxons rares; des enquêtes complémentaires dans le bassin versant ont été réalisées pour statuer sur des spots de biodiversité.

Brain areas involved in heart autonomic control are not well characterized. Insulae have been proposed as control centers. A lesion in these areas may induce a cardiac autonomic dysfunction (arrhythmias, atrioventricular conduction abnormalities). Asystolia has not been previously reported. A 65-year-old man suffered an acute ischemia of the right middle cerebral artery (MCA) territory. NIHSS score was 19 points. Brain CT scan was normal. Transcranial Doppler (TCD) showed occlusion of the right MCA. Fibrinolysis was initiated 135 minutes after stroke onset with TCD monitoring. Twenty minutes later he suffered cardiac arrest with asystolia trace in the ECG monitor. Fibrinolysis was stopped during resuscitation. Four minutes later, he recovered with the same NIHSS score. Aggressive resuscitation maneuvers were not necessary. A repeated brain CT scan showed infarct signs in the whole MCA territory and a new TCD did not show any change. Serial blood analyses including cardiac nzymes were normal. The patient experienced four brief cardiac arrests in the next nine hours, so a temporary cardiac pacemaker was placed for four days. He was treated with aspirin and was discharged 14 days after admission. He has not experienced recurrences during a 6-month follow-up. We could not diagnose the etiology of the cardiac arrests. All the episodes occurred in the acute stroke stage and arrhythmia, atrioventricular block, myocardial ischemia or structural lesions were not found in the cardiac study. We propose that ischemia in the right insula induced sudden and transitory interruptions of the sympathetic cardiac tone.

INTRODUCTION The acute vertebrobasilar occlussion is usually a life-treatening disease leading to death or major disability. The treatment with heparin and the selective fibrinolysis no show good results, for this reason the local intra-arterial fibrinolysis appear as the choice treatment in patients with stroke and a agiography with basilar artery occlussion or intracranial vertebral artery occlusion. This tecnique has been proved to be effective treatment for selected patients with acute thromboembolic occlusion of the middle cerebral artery, ophthalmic artery and vertebrobasilar system, reducing the mortality in the vertebrobasilar system from 90% to 40%. CLINICAL CASE We present a 63 years-old man with a vertebrobasilar thrombosis of a probable cardioembolic origen. He was treated with r-TPA local intra-arterial fibrinolysis, to get a recanalization of vertebrobasilar system. In the control TC we see a haemorragic sufusion in the brain stem. The follow-up see a patient with tetraparesis and palsy of the low cranial nerves and normal superior cerebral functions. CONCLUSIONS The local intra-arterial fibrinolysis is the choise treatment in the vertebrobasilar thrombosis because the high morbimortality of this patology and the inefficacy of the others therapeutics. The result depend of many factors as the thrombo location, the neurologic state, the evolution time, the start of treatment, the colateral circulation, the nervous tissue reserve, etc, that have dificult predict the result, but it is best of the natural history of the disease. Is necesary, change the concept of emergency and the attitude front the isquemic cerebral disease at the sanitary leaders, the doctors, and the general population, for dispose of more means to cofront this pathology, which permit diminish the morbimortality and reduce the grade of incapacity.

The acute vertebrobasilar occlussion is usually a life-treatening disease leading to death or major disability. The treatment with heparin and the selective fibrinolysis no show good results, for this reason the local intra-arterial fibrinolysis appear as the choice treatment in patients with stroke and a agiography with basilar artery occlussion or intracranial vertebral artery occlusion. This tecnique has been proved to be effective treatment for selected patients with acute thromboembolic occlusion of the middle cerebral artery, ophthalmic artery and vertebrobasilar system, reducing the mortality in the vertebrobasilar system from 90% to 40%.We present a 63 years-old man with a vertebrobasilar thrombosis of a probable cardioembolic origen. He was treated with r-TPA local intra-arterial fibrinolysis, to get a recanalization of vertebrobasilar system. In the control TC we see a haemorragic sufusion in the brain stem. The follow-up see a patient with tetraparesis and palsy of the low cranial nerves and normal superior cerebral functions.The local intra-arterial fibrinolysis is the choise treatment in the vertebrobasilar thrombosis because the high morbimortality of this patology and the inefficacy of the others therapeutics. The result depend of many factors as the thrombo location, the neurologic state, the evolution time, the start of treatment, the colateral circulation, the nervous tissue reserve, etc, that have dificult predict the result, but it is best of the natural history of the disease. Is necesary, change the concept of emergency and the attitude front the isquemic cerebral disease at the sanitary leaders, the doctors, and the general population, for dispose of more means to cofront this pathology, which permit diminish the morbimortality and reduce the grade of incapacity.