Le thon : enjeux et stratégies pour l'océan Indien

La pêche réunionnaise est, depuis les cinq dernières années, placée à contre temps complet de l'immense majorité des autres pêcheries communautaires (Union européenne), dans une situation de développement rapide de l'ensemble de ses segments (pêche artisanale, grande pêche hauturière antarctique, pêche palangrière). Le plus rapide de ces développements est certainement celui du segment palangrier qui, né il y a 5 ans, va cette année 1996 égaliser, voire dépasser la pêche artisanale, soit près de 1 500 t/an. Cette pêcherie est composée par 9 armements alignant 28 navirees de 12 à 33 m dont 20 sont opérationnels en 1996. Sa production est constituée pour les espèces majeures, de 2/3 d'espadons et de 1/3 de thonidés. La zone de pêche exploitée est très vaste, depuis l'équateur jusqu'au 35°Sud. Les rendements, après avoir présenté une augmentation très significative de 1992 à 1994, présentent un tassement certain de 1994 à 1996 pour tous les navires de la flotte. Ce développement se poursuit aujourd'hui au niveau de la région COI par un développement des flottilles palangrières régionales, amorcé aux Seychelles et bientôt à Maurice. Un équilibre d'exploitation pérenne doit impérativement s'appuyer sur les recherches halieutiques et socio-économiques d'accompagnement de cette pêcherie. (Résumé d'auteur

Implementing an analog speedometer in STISIM Drive using Parallax BSTAMP microcontroller

In a non-instrumental cab, STISIM Drive software normally projects the speed of the vehicle through a dashboard presented on the simulation screen. The simulated dashboard can be displayed with several graphical options. In all cases, there is a loss of information arising from the road. A solution is to integrate the speedometer into a dashboard and to disable the simulated projection. This solution increases the virtual immersion of the driver and presents speed in a more realistic way. We are proposing a simple solution based on Parallax Inc. Basic Stramp microcontroller. In addition to its low cost and simplicity, this solution allows integration of other technical elements of the driving experience (e.g., activation of turn signals, horn, etc.)

Entanglement of Dirac fields in non-inertial frames

We analyze the entanglement between two modes of a free Dirac field as seen by two relatively accelerated parties. The entanglement is degraded by the Unruh effect and asymptotically reaches a non-vanishing minimum value in the infinite acceleration limit. This means that the state always remains entangled to a degree and can be used in quantum information tasks, such as teleportation, between parties in relative uniform acceleration. We analyze our results from the point of view afforded by the phenomenon of entanglement sharing and in terms of recent results in the area of multi-qubit complementarity.Comment: 15 pages, with 8 figures (Mar 2006); accepted to Physical Review A, July 2006 - slightly revise

Characterization of pairs of toxic and nontoxic misfolded protein oligomers elucidates the structural determinants of oligomer toxicity in protein misfolding diseases

Conspectus: The aberrant misfolding and aggregation of peptides and proteins into amyloid aggregates occurs in over 50 largely incurable protein misfolding diseases. These pathologies include Alzheimer’s and Parkinson’s diseases, which are global medical emergencies owing to their prevalence in increasingly aging populations worldwide. Although the presence of mature amyloid aggregates is a hallmark of such neurodegenerative diseases, misfolded protein oligomers are increasingly recognized as of central importance in the pathogenesis of many of these maladies. These oligomers are small, diffusible species that can form as intermediates in the amyloid fibril formation process or be released by mature fibrils after they are formed. They have been closely associated with the induction of neuronal dysfunction and cell death. It has proven rather challenging to study these oligomeric species because of their short lifetimes, low concentrations, extensive structural heterogeneity, and challenges associated with producing stable, homogeneous, and reproducible populations. Despite these difficulties, investigators have developed protocols to produce kinetically, chemically, or structurally stabilized homogeneous populations of protein misfolded oligomers from several amyloidogenic peptides and proteins at experimentally ameneable concentrations. Furthermore, procedures have been established to produce morphologically similar but structurally distinct oligomers from the same protein sequence that are either toxic or nontoxic to cells. These tools offer unique opportunities to identify and investigate the structural determinants of oligomer toxicity by a close comparative inspection of their structures and the mechanisms of action through which they cause cell dysfunction. This Account reviews multidisciplinary results, including from our own groups, obtained by combining chemistry, physics, biochemistry, cell biology, and animal models for pairs of toxic and nontoxic oligomers. We describe oligomers comprised of the amyloid-β peptide, which underlie Alzheimer’s disease, and α-synuclein, which are associated with Parkinson’s disease and other related neurodegenerative pathologies, collectively known as synucleinopathies. Furthermore, we also discuss oligomers formed by the 91-residue N-terminal domain of [NiFe]-hydrogenase maturation factor from E. coli, which we use as a model non-disease-related protein, and by an amyloid stretch of Sup35 prion protein from yeast. These oligomeric pairs have become highly useful experimental tools for studying the molecular determinants of toxicity characteristic of protein misfolding diseases. Key properties have been identified that differentiate toxic from nontoxic oligomers in their ability to induce cellular dysfunction. These characteristics include solvent-exposed hydrophobic regions, interactions with membranes, insertion into lipid bilayers, and disruption of plasma membrane integrity. By using these properties, it has been possible to rationalize in model systems the responses to pairs of toxic and nontoxic oligomers. Collectively, these studies provide guidance for the development of efficacious therapeutic strategies to target rationally the cytotoxicity of misfolded protein oligomers in neurodegenerative conditions

Acquired factor V inhibitor in a context of sepsis and disseminated intravascular coagulation

International audienc

Persistent non-solar forcing of Holocene storm dynamics in coastal sedimentary archives

Considerable climatic variability on decadal to millennial timescales has been documented for the past 11,500 years of interglacial climate. This variability has been particularly pronounced at a frequency of about 1,500 years, with repeated cold intervals in the North Atlantic. However, there is growing evidence that these oscillations originate from a cluster of different spectral signatures, ranging from a 2,500-year cycle throughout the period to a 1,000-year cycle during the earliest millennia. Here we present a reappraisal of high-energy estuarine and coastal sedimentary records from the southern coast of the English Channel, and report evidence for five distinct periods during the Holocene when storminess was enhanced during the past 6,500 years.We find that high storm activity occurred periodically with a frequency of about 1,500 years, closely related to cold and windy periods diagnosed earlier. We show that millennial-scale storm extremes in northern Europe are phase-locked with the period of internal ocean variability in the North Atlantic of about 1,500 years. However, no consistent correlation emerges between spectral maxima in records of storminess and solar irradiation. We conclude that solar activity changes are unlikely to be a primary forcing mechanism of millennial-scale variability in storminess

Un colloque sur la pluridisciplinariaté dans les problèmes d'environnement : quelques enseignements et orientations pour l'avenir

International audienceAn experiment has been carried out in Rennes (Brittany, West of France) in June 2000 to estimate atrazine and alachlor volatilisation fluxes after application over a maize crop. Fluxes were calculated using the classical aerodynamic micrometeorological method from vertical gradients of pesticide concentrations, temperature and wind speed. Volatilisation fluxes showed a diurnal pattern of the order of few ng/m2/s for atrazine and the order of a few 10 ng/m2/s for alachlor, leading to cumulated losses of approximately 0.1% of the theoretical application dose for atrazine and several-fold of that in the case of alachlor