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Ultrafast Spectroscopy Evidence for Picosecond Ligand Exchange at the Binding Site of a Heme Protein: Heme-Based Sensor YddV
No full textInternational audienceAn important question for the functioning of heme proteins is whether different ligands present within the protein moiety can readily exchange with heme-bound ligands. Studying the dynamics of the heme domain of the Escherichia coli sensor protein YddV upon dissociation of NO from the ferric heme by ultrafast spectroscopy, we demonstrate that when the hydrophobic leucine residue in the distal heme pocket is mutated to glycine, in a substantial fraction of the protein water replaces NO as an internal ligand in as fast as ∼4 ps. This process, which is near-barrierless and occurs orders of magnitude faster than the corresponding process in myoglobin, corresponds to a ligand swap of NO with a water molecule present in the heme pocket, as corroborated by molecular dynamics simulations. Our findings provide important new insight into ligand exchange in heme proteins that functionally interact with different external ligands
Search for supersymmetry in pp collisions at sqrt(s) = 8 TeV in final states with boosted W bosons and b jets using razor variables
No full textSubmitted to Phys. Rev. D ; see paper for full list of authorsInternational audienceA search for supersymmetry in hadronic final states with highly boosted W bosons and b jets is presented, focusing on compressed scenarios. The search is performed using proton-proton collision data at a center-of-mass energy of 8 TeV, collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.7 inverse-femtobarns. Events containing candidates for hadronic decays of boosted W bosons are identified using jet substructure techniques, and are analyzed using the razor variables M[R] and R^2, which characterize a possible signal as a peak on a smoothly falling background. The observed event yields in the signal regions are found to be consistent with the expected contributions from standard model processes, which are predicted using control samples in the data. The results are interpreted in terms of gluino pair production followed by their exclusive decay into top squarks and top quarks. The analysis excludes gluino masses up to 1.1 TeV for light top squarks decaying solely to a charm quark and a neutralino, and up to 700 GeV for heavier top squarks decaying solely to a top quark and a neutralino
Azimuthal decorrelation of jets widely separated in rapidity in pp collisions at sqrt(s) = 7 TeV
No full textSubmitted to J. High Energy Phys - see paper for full list of authorsInternational audienceThe decorrelation in the azimuthal angle between the most forward and the most backward jets (Mueller-Navelet jets) is measured in data collected in pp collisions with the CMS detector at the LHC at sqrt(s) = 7 TeV. The measurement is presented in the form of distributions of azimuthal-angle differences, Delta(phi), between the Mueller-Navelet jets, the average cosines of (pi-Delta(phi)), 2(pi-Delta(phi)), and 3(pi-Delta(phi)), and ratios of these cosines. The jets are required to have transverse momenta, pT, in excess of 35 GeV and rapidities, |y|, of less than 4.7. The results are presented as a function of the rapidity separation, Delta(y), between the Mueller-Navelet jets, reaching Delta(y) up to 9.4 for the first time. The results are compared to predictions of various Monte Carlo event generators and to analytical predictions based on the DGLAP and BFKL parton evolution schemes
Numerical methods for an optimal multiple stopping problem
No full textInternational audienceThis paper deals with numerical solutions to an optimal multiple stopping problem. The corresponding dynamic programing (DP) equation is a variational inequality satisfied by the value function in the viscosity sense. The convergence of the numerical scheme is shown by viscosity arguments. An optimal quantization method is used for computing the conditional expectations arising in the DP equation. Numerical results are presented for the price of swing option and the behavior of the value function
Measurement of the inclusive jet cross section in pp collisions at sqrt(s) = 2.76 TeV
No full textSubmitted to Eur. Phys. J. C ; see paper for full list of authorsInternational audienceThe double-differential inclusive jet cross section is measured as a function of jet transverse momentum pT and absolute rapidity y, using proton-proton collision data collected with the CMS experiment at the LHC, at a center-of-mass energy of sqrt(s) = 2.76 TeV and corresponding to an integrated luminosity of 5.43 inverse-picoboarns. Jets are reconstructed within the pT range of 74 to 592 GeV and the rapidity range |y| < 3.0. The reconstructed jet spectrum is corrected for detector resolution. The measurements are compared to the theoretical prediction at next-to-leading-order QCD using different sets of parton distribution functions. This inclusive cross section measurement explores a new kinematic region and is consistent with QCD predictions
Optimal Skorokhod embedding given full marginals and Azéma -Yor peacocks *
No full textInternational audienceWe consider the optimal Skorokhod embedding problem (SEP) given full marginals over the time interval [0, 1]. The problem is related to the study of extremal martingales associated with a peacock (" process increasing in convex order " , by Hirsch, Profeta, Roynette and Yor [16]). A general duality result is obtained by convergence techniques. We then study the case where the reward function depends on the maximum of the embedding process, which is the limit of the martingale transport problem studied in Henry-Labord ere, Ob lój , Spoida and Touzi [13]. Under technical conditions, some explicit characteristics of the solutions to the optimal SEP as well as to its dual problem are obtained. We also discuss the associated martingale inequality
On the vertical distribution of smoke in the Amazonian atmosphere during the dry season
No full textInternational audienceLidar observations of smoke aerosols have been analysed from six flights of the Facility for Airborne Atmospheric Measurements BAe-146 research aircraft over Brazil during the biomass burning season (September 2012). A large aerosol optical depth (AOD) was observed, typically ranging 0.4–0.9, along with a typical aerosol extinction coefficient of 100–400 Mm −1. The data highlight the persistent and widespread nature of the Amazonian haze, which had a consistent vertical structure, observed over a large distance (∼ 2200 km) during a period of 14 days. Aerosols were found near the surface; but the larger aerosol load was typically found in elevated layers that extended from 1–1.5 to 4– 6 km. The measurements have been compared to model predictions with the Met Office Unified Model (MetUM) and the ECMWF-MACC model. The MetUM generally reproduced the vertical structure of the Amazonian haze observed with the lidar. The ECMWF-MACC model was also able to reproduce the general features of smoke plumes albeit with a small overestimation of the AOD. The models did not always capture localised features such as (i) smoke plumes originating from individual fires, and (ii) aerosols in the vicinity of clouds. In both these circumstances, peak extinction coefficients of the order of 1000–1500 Mm −1 and AODs as large as 1–1.8 were encountered, but these features were either underestimated or not captured in the model predictions. Smoke injection heights derived from the Global Fire Assimilation System (GFAS) for the region are compatible with the general height of the aerosol layers
Consistent inconsistencies? Evidence from decision under risk
No full textInternational audienceConventional economic theory assumes that agents should be consistent across decisions. However, it is often observed that experimental subjects fail to report consistent preferences. So far, these inconsistencies are almost always examined singly. We thus wonder whether the more inconsistent individuals in one task are also more inconsistent in other tasks. We propose an experiment in which subjects are asked to report their preferences over risky bets so as to obtain, for each subject, three measures of inconsistencies: classical preference reversals, framing effects and preference instability. In line with previous experimental findings, subjects are largely inconsistent according to each of these three measures and there are considerable individual differences. The main result is that we find no correlation among these three measures of inconsistency
L'empire romain ne doit pas être géré comme une petite île grecque
No full textInternational audienceDepuis quelques années, des systèmes de crypto-devises ont fait leur apparition, permettant d'acheter des biens ou services de manière décentralisée en s'affranchissant de tout système bancaire. Bitcoin est un système pair-à-pair de crypto-devises considéré comme l'un des pionniers de ce type de système. Un adversaire peut chercher à mettre en dé-faut le système en insérant des données incohérentes dans l'historique des transactions, appelé blockchain. En exploitant une situation de compétition, il peut alors acquérir des biens ou services gratuitement. Afin de bloquer ces comporte-ments, PeerCensus propose d'utiliser des techniques d'accord basées sur les identités présentes dans la blockchain. Dans cet article, nous proposons une évaluation probabiliste de la fiabilité de l'architecture PeerCensus
Optimum plasma grid bias for a negative hydrogen ion source operation with Cs
No full textInternational audienceThe functions of a biased plasma grid of a negative hydrogen (H−) ion source for both pure volume and Cs seeded operations are reexamined. Proper control of the plasma grid bias in pure volume sources yields: enhancement of the extracted negative ion current, reduction of the co-extracted electron current, flattening of the spatial distribution of plasma potential across the filter magnetic field, change in recycling from hydrogen atomic/molecular ions to atomic/molecular neutrals, and enhanced concentration of H− ions near the plasma grid. These functions are maintained in the sources seeded with Cs with additional direct emission of negative ions under positive ion and neutral hydrogen bombardment onto the plasma electrode