614 research outputs found

    Immunologie de l’Ɠil

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    RĂ©sumĂ©L’Ɠil impose au systĂšme immunitaire des contraintes d’efficacitĂ© et d’innocuitĂ© particuliĂšrement exigeantes et contradictoires. Interface avec le monde environnant, il constitue avec ses annexes un compartiment muqueux de l’organisme de petite dimension, particuliĂšrement exposĂ©, mais apparemment peu vulnĂ©rable grĂące Ă  une multiplicitĂ© de moyens de dĂ©fense : flore microbienne proche de celle de la peau ; clignement des paupiĂšres, flux continu du film lacrymal et composition complexe et variable de ce dernier qui doit ĂȘtre agressif Ă  l’égard des microorganismes, mais protecteur et nutritif pour la cornĂ©e et de plus optiquement favorable ; et enfin tissu lymphoĂŻde associĂ© aux muqueuses caractĂ©risĂ© lĂ  par la production abondante d’IgA1 et d’IgD et d’anticorps naturels. À la fois vitre et ultime barriĂšre, la cornĂ©e possĂšde tous les Ă©lĂ©ments nĂ©cessaires Ă  une rĂ©ponse efficace, mais par leur distribution ou leur Ă©tat basal, ne les utilisera qu’en dernier recours. L’Ɠil est en effet aussi un instrument d’optique prolongeant le systĂšme nerveux central ; les vaisseaux doivent donc ĂȘtre absents de l’axe optique et toute inflammation comporte le risque d’ĂȘtre dĂ©lĂ©tĂšre. Le « privilĂšge immunitaire » rĂ©sulte localement du contrĂŽle Ă©troit exercĂ© sur les cellules lymphoĂŻdes et rĂ©actions immunitaires par l’exclusion molĂ©culaire due aux barriĂšres hĂ©mato-oculaires, une ambiance molĂ©culaire inhibitrice et diverses interactions cellulaires pouvant gĂ©nĂ©rer apoptose ou cellules rĂ©gulatrices. De plus, ce contrĂŽle peut s’accompagner d’une rĂ©ponse systĂ©mique caractĂ©risĂ©e par une diminution de l’hypersensibilitĂ© retardĂ©e, une facilitation de la production d’anticorps ne fixant pas le complĂ©ment et la gĂ©nĂ©ration de cellules T rĂ©gulatrices spĂ©cifiques d’antigĂšnes, un phĂ©nomĂšne nommĂ© « dĂ©viation immunitaire associĂ©e Ă  la chambre antĂ©rieure de l’Ɠil ». Cependant, la relative inaccessibilitĂ© de l’Ɠil sain au systĂšme immunitaire pourrait rendre les mĂ©canismes de tolĂ©rance immunitaire pĂ©riphĂ©rique moins efficaces d’oĂč une vulnĂ©rabilitĂ© particuliĂšre aux Ă©tats auto-immuns et des autoanticorps antirĂ©tine dans des syndromes paranĂ©oplasiques. L’Ɠil est ainsi armĂ© pour rĂ©agir, mais sa rĂ©ponse est Ă©troitement contrĂŽlĂ©e et orientĂ©e ; les associations entre pathologies et systĂšmes HLA ou du complĂ©ment sont aussi des clefs pour mieux comprendre les mĂ©canismes molĂ©culaires Ă  l’Ɠuvre

    Feedback Corrections for Ground Motion Effects at ATF2

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    accelconf.web.cern.ch/accelconf/e08/papers/tupc122.pdfInternational audienceGoals of ATF2 will be to provide beams with a few tens of nanometers and stability at the nanometer level. To achieve this, several corrections have to be applied as tra- jectory corrections and optics correction. Once the most critical effects are found, they must be canceled by trajec- tory correction and rematching of the optics quickly and efïŹciently. A method using SVD-determined knobs and how it can be implemented in ATF2 are here described

    A Novel Faceted UTD Solver in Altair Feko for Antenna Placement Applications

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    2022 3rd URSI Atlantic and Asia Pacific Radio Science Meeting (AT-AP-RASC), , 30/05/2022-04/06/2022, , EspañaA new Faceted UTD solver as implemented in Altair Feko is introduced here. The solver is based on UTD (Uniform Theory of Diffraction) applied to planar and arbitrarily convex curved surfaces meshed with planar triangles. It is most suitable for antenna placement applications in the high frequency regime

    1,1,1,5,5,5-Hexafluoro-2,4-dimeth­oxy­pentane-2,4-diol

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    The title compound, C7H10F6O4, was isolated as an unexpected product from a reaction of tantalum(V) methoxide with hexa­fluoro­acetyl­acetone in a methanol solution. The asymmetric unit consists of one half-mol­ecule with the middle C atom lying on a twofold axis. The crystal structure is stabilized by O—H⋯O and an array of C—H⋯F hydrogen-bonding inter­actions. These inter­actions link the mol­ecules into a stable supra­molecular three-dimensional network. The mol­ecules pack in a ribbon-like form in the ac plane as a result of these inter­actions

    Recent Improvements in the Tracking Code Placet

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    The tracking code Placet has recently undergone several improvements. A redesign of its internal data structures and a new user interface based on the mathematical toolbox Octave considerably expanded its simulation capabilities. Several new lattice elements, optimization algorithms and physics processes were added to allow for more complete start-to-end simulations. Finally, the use of the AML language and the Universal Parser Library have extended its interfacing capability. A review of these new features is presented in this paper
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