Producing baryons from neutralinos in small H2 clumps over cosmological ages

Extreme scattering events in quasars suggest the existence of dark $\rm H_2$ clumps of mass $\rm \sim 10^{-3} M_\odot$ and size $\rm \sim 10 AU$. Such clumps are extremely dense compared to WIMPs clumps of the same mass obtained by N-body simulations. A WIMP clump gravitationally attracted by a central $\rm H_2$ clump would experience a first infall during which its density increases by $\rm 10^6$ in $\rm \sim 1 Myr$. In this poster I begin to explore the phenomenology of mixed clumps made with $\rm H_2$ and WIMPs. Molecular clouds built with clumps are efficient machines to transform smooth distributions of WIMPs into concentrated networks. If WIMPs are neutralinos gravitationally attracted in clumps of such molecular clouds, they may either enrich the baryon sector over cosmological ages, or remain mixed with cold $\rm H_2$ clouds until the clumps evaporate either by collision or by stellar UV heating. A phenomenological model based on an hypothetic dark baryonic component (DBC) that was invoked in the past to explain one of the main drawbacks of CDM profiles, their overly dense cores, is briefly revisited in this context. The DBC is replaced by a mix of $\rm H_2$ and WIMPs, with a small fraction of HI produced by internal $\rm H_2$ collisions, in slightly dispersive clumpy clouds that may migrate from the halo towards inner parts of a galaxy and disk.Comment: 6 pages, 1 figure, submitted to Conference: XII International Symposium on Nuclei in the Cosmos August 5-12, 2012 Cairns, Australi

Epidemiology and Evolution of Fungal Pathogens in Plants and Animals

International audienc

ATP-P2X7 Receptor Modulates Axon Initial Segment Composition and Function in Physiological Conditions and Brain Injury

© 2014 The Author. All rights reserved. Axon properties, including action potential initiation and modulation, depend on both AIS integrity and the regulation of ion channel expression in the AIS. Alteration of the axon initial segment (AIS) has been implicated in neurodegenerative, psychiatric, and brain trauma diseases, thus identification of the physiological mechanisms that regulate the AIS is required to understand and circumvent AIS alterations in pathological conditions. Here, we show that the purinergic P2X7 receptor and its agonist, adenosine triphosphate (ATP), modulate both structural proteins and ion channel density at the AIS in cultured neurons and brain slices. In cultured hippocampal neurons, an increment of extracellular ATP concentration or P2X7-green fluorescent protein (GFP) expression reduced the density of ankyrin G and voltage-gated sodium channels at the AIS. This effect is mediated by P2X7-regulated calcium influx and calpain activation, and impaired by P2X7 inhibition with Brilliant Blue G (BBG), or P2X7 suppression. Electrophysiological studies in brain slices showed that P2X7-GFP transfection decreased both sodium current amplitude and intrinsic neuronal excitability, while P2X7 inhibition had the opposite effect. Finally, inhibition of P2X7 with BBG prevented AIS disruption after ischemia/reperfusion in rats. In conclusion, our study demonstrates an involvement of P2X7 receptors in the regulation of AIS mediated neuronal excitability in physiological and pathological conditions.Plan Nacional I+D+i (Spain), INSERM and Agence National de la Recherche (EXCION, EPISOM)Peer Reviewe

Development of shower simulation and reconstruction tools for gamma-ray astronomy with the future ground based detectors

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

L'Alios spécial des gisements Tardenoisiens de la région Parisienne

Giraud Ed., Vignard Ed. L'Alios spécial des gisements Tardenoisiens de la région Parisienne. In: Bulletin de la Société préhistorique de France, tome 41, n°4-6, 1944. pp. 108-112

Un Rendez-vous de chasse Mésolithique « Les Rochers », commune d'Auffargis (Seine-et-Oise)

Giraud Ed., Vignard Ed. Un Rendez-vous de chasse Mésolithique « Les Rochers », commune d'Auffargis (Seine-et-Oise). In: Bulletin de la Société préhistorique de France, tome 43, n°7-8, 1946. pp. 248-258

ATP-P2X7 Receptor Modulates Axon Initial Segment Composition and Function in Physiological Conditions and Brain Injury

International audienceAxon properties, including action potential initiation and modulation, depend on both AIS integrity and the regulation of ion channel expression in the AIS. Alteration of the axon initial segment (AIS) has been implicated in neurodegenerative, psychiatric, and brain trauma diseases, thus identification of the physiological mechanisms that regulate the AIS is required to understand and circumvent AIS alterations in pathological conditions. Here, we show that the puri-nergic P2X7 receptor and its agonist, adenosine triphosphate (ATP), modulate both structural proteins and ion channel density at the AIS in cultured neurons and brain slices. In cultured hippocampal neurons, an increment of extracellular ATP concentration or P2X7-green fluorescent protein (GFP) expression reduced the density of ankyrin G and voltage-gated sodium channels at the AIS. This effect is mediated by P2X7-regulated calcium influx and calpain activation, and impaired by P2X7 inhibition with Brilliant Blue G (BBG), or P2X7 suppression. Electrophysiological studies in brain slices showed that P2X7-GFP transfection decreased both sodium current amplitude and intrinsic neuronal excitability, while P2X7 inhibition had the opposite effect. Finally, inhibition of P2X7 with BBG prevented AIS disruption after ischemia/reperfusion in rats. In conclusion, our study demonstrates an involvement of P2X7 receptors in the regulation of AIS mediated neuronal excitability in physiological and pathological conditions

Les bobos n’existent pas

Omniprésent dans les médias, mais aussi dans le champ politique et dans le langage ordinaire, le terme « bobo » n’est pas neutre. Son usage et ses variantes (« boboïsation », « boboïsé ») tendent à simplifier, et donc aussi à masquer, l’hétérogénéité des populations et la complexité des processus affectant les espaces urbains qu’ils prétendent décrire. En réduisant les « bobos  » à des caricatures, on juge des caractères, des intentions et des volontés, en oubliant que les représentations et les pratiques des individus et des groupes sociaux prennent place dans des trajectoires singulières et un monde hiérarchisé. Ainsi, scientifiquement parlant, les bobos n’existent pas, et des expressions telles que « boboïsation » ou « boboïsé » ne conviennent pas pour saisir et caractériser la diversité des logiques et des mécanismes, voire, parfois, les contradictions à l’œuvre dans les phénomènes de « gentrification ». C’est ce que montre cet ouvrage, qui propose un regard historique et sociologique sur le mot « bobo » et ses usages dans les univers médiatiques, politiques et culturels, comme dans les discours des populations impliquées

Release-dependent variations in synaptic latency: a putative code for short- and long-term synaptic dynamics.: Release-dependent latency variation at cortical synapses

International audienceIn the cortex, synaptic latencies display small variations ( approximately 1-2 ms) that are generally considered to be negligible. We show here that the synaptic latency at monosynaptically connected pairs of L5 and CA3 pyramidal neurons is determined by the presynaptic release probability (Pr): synaptic latency being inversely correlated with the amplitude of the postsynaptic current and sensitive to manipulations of Pr. Changes in synaptic latency were also observed when Pr was physiologically regulated in short- and long-term synaptic plasticity. Paired-pulse depression and facilitation were respectively associated with increased and decreased synaptic latencies. Similarly, latencies were prolonged following induction of presynaptic LTD and reduced after LTP induction. We show using the dynamic-clamp technique that the observed covariation in latency and synaptic strength is a synergistic combination that significantly affects postsynaptic spiking. In conclusion, amplitude-related variation in latency represents a putative code for short- and long-term synaptic dynamics in cortical networks

GSK3 and b-catenin determines functional expression of sodium channels at the axon initial segment

Neuronal action potentials are generated through voltage-gated sodium channels, which are tethered by ankyrinG at the membrane of the axon initial segment (AIS). Despite the importance of the AIS in the control of neuronal excitability, the cellular and molecular mechanisms regulating sodium channel expression at the AIS remain elusive. Our results show that GSK3a/b and b-catenin phosphorylated by GSK3 (S33/37/T41) are localized at the AIS and are new components of this essential neuronal domain. Pharmacological inhibition of GSK3 or b-catenin knockdown with shRNAs decreased the levels of phosphorylated-b-catenin, ankyrinG, and voltagegated sodium channels at the AIS, both ‘‘in vitro’’ and ‘‘in vivo’’, therefore diminishing neuronal excitability as evaluated via sodium current amplitude and action potential number. Thus, our results suggest a mechanism for the modulation of neuronal excitability through the control of sodium channel density by GSK3 and b-catenin at the AIS.This work was supported by grants SAF2009-12249-C02-02 and SAF2009-12249- C02-01 from the Ministerio de Ciencia e Innovacion (Spain), by the Centro de Investigacio´ n Biome´ dica en Red de Enfermedades Neurodegenerativas (CIBERNED, Spain), INSERM and Agence National de la Recherche (EXCION, EPISOM). Mo´nica Tapia is supported by a CSIC-JAE fellowship.Peer reviewe