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Constraints on parton distribution functions and extraction of the strong coupling constant from the inclusive jet cross section in pp collisions at sqrt(s) = 7 TeV
No full textReplaced with published version. Added journal reference and DOI ; see paper for full list of authorsInternational audienceThe inclusive jet cross section for proton-proton collisions at a centre-of-mass energy of 7 TeV was measured by the CMS Collaboration at the LHC with data corresponding to an integrated luminosity of 5.0 inverse femtobarns. The measurement covers a phase space up to 2 TeV in jet transverse momentum and 2.5 in absolute jet rapidity. The statistical precision of these data leads to stringent constraints on the parton distribution functions of the proton. The data provide important input for the gluon density at high fractions of the proton momentum and for the strong coupling constant at large energy scales. Using predictions from perturbative quantum chromodynamics at next-to-leading order, complemented with electroweak corrections, the constraining power of these data is investigated and the strong coupling constant at the Z boson mass M[Z] is determined to be alpha[S(M[Z])} = 0.1185 +/- 0.0019 (exp) +0.0060 -0.0037 (theo), which is in agreement with the world average
Investigation des Interactions Toxine-Cellule et du Confinement des Récepteurs dans la Membrane Cellulaire
No full textThe cell membrane is the interface of communication and exchange between thecell and the outside world. As such, its structure and composition is of integralimportance to the cell’s continued survival. The proteins within the membraneprovide the necessary functionalities to the membrane for successfully acting outits role. The membrane receptors experience a highly heterogeneous environmentin the cell membrane that enhances their efficiency. We studied this environmentvia single particle tracking of cell membrane receptors tagged with luminescentlanthanide-doped nanoparticles. The nanoparticles provided a continuous,uninterrupted signal of the movements, yielding trajectories of several minutes.We then used a method based on statistical Bayesian inference to analyse andcompare the trajectories obtained and, hence, extract a confinement potential ofarbitrary shape.We first validated the Bayesian inference approach by demonstrating that thismethod can also be used to calibrate an optical tweezers setup. Furthermore, weshowed that this method outperforms established calibration methods for opticaltraps. We then applied this approach to the confined trajectories of epsilon-toxin(produced by Clostridium perfringens) receptors in Madin-Darby canine kidneycells. In particular, we studied the evolution of the confinement potential anddiffusivity within the domains upon addition of domain-destabilizing agents, aswell as the occasional ‘hopping’ events, during which receptors are seen to hopinto an adjacent confinement domain, and the associated 'hopping' energies.Additionally, we inquired into the effect of an externally applied force,implemented via a hydrodynamic flow on the receptors, and discovered an actindependentconfinement of the microdomains in addition to the lipid-dependentconfinement.To further investigate the nature of membrane receptor confinement, weclassified the potentials obtained from raft and non-raft proteins using a decisiontreemethod and a clustering algorithm. The results showed that non-raft proteinsreside in domains that produce a steeper potential boundary with a flatterpotential in the centre of the domain as compared to raft proteins.Finally, we extended the single-particle tracking of toxins to three dimensions byregistering the width of the point-spread function of the nanoparticle signal. Inthis way, we were able to observe the internalization trajectory of a heavy-chainsegment of the botulinum toxin A of Clostridium botulinum in cells of the intestinalmouse cell line m-ICcl2.La membrane cellulaire est l’interface de communication et d’échange entre lacellule et le monde extérieur. En tant que telle, sa structure et composition ont uneimportance centrale à la viabilité de la cellule. Les protéines qui résident dans lamembrane apportent la fonctionnalité nécessaire pour permettre à la membraned’accomplir ces tâches. Ces récepteurs se retrouvent dans un environnement dehaute hétérogénéité qui renforce leur efficacité. Nous avons étudié cetenvironnent en suivant des récepteurs uniques dans la membrane grâce auxnanoparticules dopées aux terres rares. Ces nanoparticules produisent dessignaux continus, non-interrompus, permettant de suivre des trajectoires pendantplusieurs minutes. Nous avons ensuite utilisé une méthode basée sur l’inférencebayésienne pour analyser et comparer les trajectoires obtenues, et pour extrairele potentiel de confinement de forme arbitraire correspondant à chaquetrajectoire.Nous avons d’abord validé l’approche de l’inférence bayésienne en démontrantque cette méthode peut également être utilisée pour la calibration d’un montagede pinces optiques. Par ailleurs, nous avons démontré que cette approche estsupérieure aux techniques couramment utilisées pour la calibration des pincesoptiques. Puis, nous avons appliqué cette méthode aux trajectoires des récepteursde la toxine epsilon (de Clostridium perfringens) dans des cellules rénales canines Madin-Darby (MDCK). En particulier, nous avons étudié l’évolution du potentiel deconfinement et de la diffusivité à l’intérieur des domaines confinant les récepteurspendant l’action d’un agent déstabilisant les domaines de confinement, ainsi queles événement de ‘hopping’ pendant lesquels le récepteur change de domaine deconfinement, et déterminé les énergies de ‘hopping’ associées. De plus, nousavons observé l’effet d’une force externe appliquée au récepteur, produite par unflux hydrodynamique. L’application d’une force a mis en évidence une dépendancedu confinement des récepteurs du cytosquelette d’actine en plus du confinementproduit par la distribution des lipides.Pour approfondir notre investigation du confinement des récepteurs de lamembrane, nous avons classifié les potentiels de confinement obtenus pour lesrécepteurs résidant à l’intérieur et à l’extérieur des radeaux lipidiques. Lespotentiels ressentis par les récepteurs en dehors des domaines lipidiques sontplus plats au centre du domaine de confinement et plus abrupts vers les bords dudomaine par rapport aux potentiels ressentis par les protéines dans les radeaux.Enfin, nous avons étendu la technique de suivi de particules uniques en 3D enutilisant la largeur de la fonction de réponse du signal de la nanoparticule. De cettemanière, nous avons observé le mouvement d’internalisation de nanoparticulescouplées à un fragment de la chaine lourde de la toxine botulique A de Clostridiumbotulinum dans des cellules intestinales de souris de la lignée m-ICcl2
A convergent route to substituted azetidines and to Boc-protected 4-aminomethylpyrroles
No full textInternational audienceThe radical addition of xanthates to Boc-protected azetine gives adducts, which can be reductively dexanthylated to furnish variously substituted azetidines. In the case of α-xanthyl ketones, treatment of the initial adducts with ammonia or primary amines, furnishes 2,4-disubstituted, 2,3,4-trisubstituted, and polycyclic pyrroles having a protected aminomethyl group at position-4. An unusual ring opening was observed in the case of a cyclobutanone precursor. It also proved possible to add an azetidinyl radical to an indole ring. Most of these products would be very difficult to obtain by more conventional routes
Multiscale identification of the random elasticity field at mesoscale of a heterogeneous microstructure using multiscale experimental observations
No full textInternational audienceThis paper deals with a multiscale statistical inverse method for performing the experimental identification of the elastic properties of materials at macroscale and at mesoscale within the framework of a heterogeneous microstructure which is modeled by a random elastic media. New methods are required for carrying out such multiscale identification using experimental measurements of the displacement fields carried out at macroscale and at mesoscale with only a single specimen submitted to a given external load at macroscale. In this paper, for a heterogeneous microstructure, a new identification method is presented and formulated within the framework of the three-dimensional linear elasticity. It permits the identification of the effective elasticity tensor at macroscale, and the identification of the tensor-valued random field, which models the apparent elasticity field at mesoscale. A validation is presented first with simulated experiments using a numerical model based on the hypothesis of 2D-plane stresses. Then, we present the results given by the proposed identification procedure for experimental measurements obtained by digital image correlation (DIC) on cortical bone
Multiphoton light-sheet microscopy using wavelength mixing: fast multicolor imaging of the beating Zebrafish heart with low photobleaching.
No full textInternational audienceTwo-photon laser scanning microscopy has become a standard to map thick and live tissues. However, its application for fast and multicolor imaging remains challenging. To address this issue, we report on the implementation of mixed wavelength excitation in a two-photon light-sheet microscope. We illustrate the potential of the technique by recording sustained multicolor two-photon movies of the beating heart in zebrafish embryos with negligible photobleaching at 28 million pixels/second. In particular, 3D reconstructions of the heart periodic motion are obtained with sufficient spatiotemporal resolution to track the fast movements of individual cells during a cardiac cycle. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only
Sequential State Estimation for Electrophysiology Models with Front Level-Set Data Using Topological Gradient Derivations
No full textInternational audienceWe propose a new sequential estimation method for making an electrophysiology model patient-specific, with data in the form of level sets of the electrical potential. Our method incorporates a novel correction term based on topological gradients, in order to track solutions of complex patterns. Our assessments demonstrate the effectiveness of this approach, including in a realistic case of atrial fibrillation
Quelques problèmes additifs : bases, pseudo-puissances et ensembles k-libres
No full textWidely studied in N or Z, we are interested in additive bases in infinite abelian groups. We get some results about the functions E, X and S, which caracterize the behaviour of a basis when we remove an element. We also study the set A of pseudo s-th powers, which is an additive basis of order s+1. We wonder what is the minimal size of an additive complement of sA, that is a set B such that sA+B contains all large enough integers. With respect to this problem, we prove quite precise theorems which are tantamount to asserting that a threshold phenomenon occurs. Finally, we establish the maximal size of a k-free set in Z/nZ. The study of this quantity strongly depends on the arithmetical relative properties of n and k. That is why we use different methods depending on cases. In particular, we show a result on combinatorial trees for the general case.Habituellement étudié dans N ou Z, on s'intéresse aux bases additives dans les groupes abéliens infinis. On obtient des résultats sur les fonctions E, X et S, qui caractérisent le comportement d'une base lorsqu'on lui enlève un élément. On étudie également l'ensemble A des pseudo-puissances s-ièmes. Celles-ci forment presque sûrement une base additive d'ordre s+1. On cherche à affiner ce résultat en déterminant des compléments additifs de sA de taille minimale, c'est-à-dire des ensembles B tels que sA+B contient presque sûrement tout entier suffisamment grand. Enfin, nous montrons quelle est la taille maximale d'un ensemble k-libre dans Z/nZ. La contrainte modulaire joue ici un rôle prépondérant. Les méthodes employées sont très différentes, selon la relation arithmétique entre k et n. En particulier, nous démontrons un résultat sur des arbres combinatoires, dans l'étude du cas général
Étude du transport turbulent dans les plasmas du tokamak Tore Supra : observation des écoulements perpendiculaires stationnaires et du modeacoustique géodésique
No full textTokamaks are toroidal machines designed to magnetically confine plasma and to host reactions of nuclear fusion. Their performance is limited by turbulent transport, which precise mechanisms are not fully elucidated. Turbulent fluctuations cause the onset of macroscopic mean flows, in the direction perpendicular to both magnetic field and small radius, called zonal flows. Their shear is known to decrease both fluctuation level and transport. Diagnostics of Doppler backscattering have been installed on Tore Supra (CEA Cadarache). They could measure the perpendicular velocity of turbulent fluctuations in different zones of the plasma.First, it is shown that, on average, fluctuations flow twice as fast at the low field side of the machine than at its top. The difference, significantly higher than predicted by common models, is put in perspective with the properties of magnetic equilibrium and the behaviour of fluctuations.Then, variations of the velocity, due to the zonal flow branch called geodesic acoustic mode (GAM), are examined in a series of experiments where collisionality is varied. Those observations have been quantitatively compared with a gyrokinetic simulation with the code GYSELA, using the equilibrium profiles from the experiments. GAM frequency in experiments is lower than predicted, especially at low collisionalities. In addition, the instationarity of GAM has been characterized with the Hilbert-Huang transform. Burts of GAM oscillations have similar statistics between experiments and simulation and their duration could be related with the nonlinear interaction between the GAM and turbulence and with the continuum damping which is observed in the simulation.Les tokamaks, machines toroïdales à confinement magnétique conçues pour porter un plasma aux conditions nécessaires à l'obtention de réactions de fusion, ont des performances limitées par le transport turbulent, dont les mécanismes ne sont pas tous élucidés. Les fluctuations turbulentes alimentent des écoulements macroscopiques, dits flots zonaux, dont le cisaillement réduit en retour le niveau de fluctuation. Des dispositifs de rétrodiffusion Doppler ont été installés sur Tore Supra (CEA Cadarache) et permettent de mesurer la vitesse perpendiculaire des fluctuations.Premièrement, il est montré que la vitesse moyenne est près de deux fois supérieure du côté externe du plasma que dans sa partie supérieure, au-delà des prédictions conventionnelles. Ces asymétries sont mises en perspective avec certains aspects de l'équilibre magnétique et des caractéristiques des fluctuations.Puis, les oscillations de la vitesse, attribuées à la branche des flots zonaux dite mode géodésique acoustique (GAM), ont été caractérisées dans des expériences où la collisionalité varie. Elles sont comparées aux prédictions théoriques et aux résultats d'une simulation avec le code gyrocinétique GYSELA, utilisant les profils expérimentaux d'équilibre. La fréquence du GAM dans l'expérience est plus faible que prédit, en particulier aux plus basses collisionalités. Les variations de son intensité, détectées avec la transformée de Hilbert-Huang, montrent des bouffées d'oscillations de distributions analogues entre expérience et simulation, et dont la durée pourrait être liée à son interaction non-linéaire avec la turbulence ainsi qu'au phénomène d'amortissement de continuum observé dans la simulation
Compact data structures for triangulations
No full textInternational audienceThe main problem consists in designing space-efficient data structures allowing to represent the connectivity of triangle meshes while supporting fast navigation and local updates
Amplified short-wavelength light scattered by relativistic electrons in the laser-induced optical lattice
No full textInternational audienceThe scheme of the x-ray free electron laser based on the optical undulator created by two overlapped transverse laser beams is analyzed. A kinetic theoretical description and an ad hoc numerical model are developed to account for the finite energy spread, angular divergence, and the spectral properties of the electron beam in the optical lattice. The theoretical findings are compared to the results of the one- and three-dimensional numerical modeling with the spectral free electron laser code plares