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Search for new phenomena in monophoton final states in proton-proton collisions at sqrt(s) = 8 TeV
No full textsee paper for full list of authorsInternational audienceResults are presented from a search for new physics in final states containing a photon and missing transverse momentum. The data correspond to an integrated luminosity of 19.6 inverse femtobarns collected in proton-proton collisions at sqrt(s) = 8 TeV with the CMS experiment at the CERN LHC. No deviation from the standard model predictions is observed for these final states. New, improved limits are set on dark matter production and on parameters of models with large extra dimensions. In particular, the first limits from the LHC on branon production are found and significantly extend previous limits from LEP and the Tevatron. An upper limit of 14.0 fb on the cross section is set at the 95% confidence level for events with a monophoton final state with photon transverse momentum greater than 145 GeV and missing transverse momentum greater than 140 GeV
On the radiative impact of aerosols on photolysis rates: comparison of simulations and observations in the Lampedusa island during the ChArMEx/ADRIMED campaign
No full textInternational audienceThe Mediterranean basin is characterized by large concentrations of aerosols from both natural and anthro-pogenic sources. These aerosols affect tropospheric photo-chemistry by modulating the photolytic rates. Three simulations of the atmospheric composition at basin scale have been performed with the CHIMERE chemistry-transport model for the period from 6 June to 15 July 2013 covered by the ADRIMED campaign, a campaign of intense measurements in the western Mediterranean basin. One simulation takes into account the radiative effect of the aerosols on photo-chemistry, the second one does not, and the third one is designed to quantify the model sensitivity to a bias in the ozone column. These simulations are compared to satellite and ground-based measurements, with a particular focus on the area of Lampedusa. Values of the aerosol optical depth (AOD) are obtained from the MODIS instrument on the AQUA and TERRA satellites as well as from stations in the AERONET network and from the MFRSR sun photometer deployed at Lampedusa. Additional measurements from instruments deployed at Lampedusa either permanently or exceptionally are used for other variables: MFRSR sun photometer for AOD, diode array spectrometer for actinic fluxes, LIDAR for the aerosol backscatter, sequential sampler for speciation of aerosol and Brewer spectrophotometer for the total ozone column. It is shown that CHIMERE has a significant ability to reproduce observed peaks in the AOD, which in Lampe-dusa are mainly due to dust outbreaks during the ADRIMED period, and that taking into account the radiative effect of the aerosols in CHIMERE considerably improves the ability of the model to reproduce the observed day-today variations of the photolysis rate of ozone to O2 and O(1D), J (O1D), and that of NO2 to NO and O(3P), J(NO2). While in the case of J(O1D) other variation factors such as the stratospheric ozone column are very important in representing correctly the day-to-day variations, the day-to-day variations of J(NO2) are captured almost completely by the model when the optical effects of the aerosols are taken into account. Finally, it is shown that the inclusion of the direct radiative effect of the aerosols in the CHIMERE model leads to reduced J(O1D) and J(NO2) values over all the simulation domain, which range from a few percents over continental Europe and the northeast Atlantic Ocean to about 20 % close to and downwind from Saharan dust sources. The effect on the modelled ozone concentration is 2-fold: the effect of aerosols leads to reduced ozone concentrations over the Mediterranean Sea and continental Europe, close to the sources of NOx , but it also leads to increased ozone concentrations over remote areas such as the Sahara and the tropical Atlantic Ocean
Generic controllability of the bilinear Schrödinger equation on 1-D domains: the case of measurable potentials
No full textInternational audienceIn recent years, several sufficient conditions for the controllability of the Schrödinger equation have been proposed. In this article, we discuss the genericity of these conditions with respect to the variation of the controlled or the uncontrolled potential. In the case where the Schrödinger equation is set on a domain of dimension one, we improve the results in the literature, removing from the previously known genericity results some unnecessary technical assumptions on the regularity of the potentials
Protein:Ligand binding free energies: A stringent test for computational protein design
No full textInternational audienceA computational protein design method is extended to allow Monte Carlo simulations where two ligands are titrated into a protein binding pocket, yielding binding free energy differences. These provide a stringent test of the physical model, including the energy surface and sidechain rotamer definition. As a test, we consider tyrosyl-tRNA synthetase (TyrRS), which has been extensively redesigned experimentally. We consider its specificity for its substrate l-tyrosine (l-Tyr), compared to the analogs d-Tyr, p-acetyl-, and p-azido-phenylalanine (ac-Phe, az-Phe). We simulate l- and d-Tyr binding to TyrRS and six mutants, and compare the structures and binding free energies to a more rigorous “MD/GBSA” procedure: molecular dynamics with explicit solvent for structures and a Generalized Born + Surface Area model for binding free energies. Next, we consider l-Tyr, ac- and az-Phe binding to six other TyrRS variants. The titration results are sensitive to the precise rotamer definition, which involves a short energy minimization for each sidechain pair to help relax bad contacts induced by the discrete rotamer set. However, when designed mutant structures are rescored with a standard GBSA energy model, results agree well with the more rigorous MD/GBSA. As a third test, we redesign three amino acid positions in the substrate coordination sphere, with either l-Tyr or d-Tyr as the ligand. For two, we obtain good agreement with experiment, recovering the wildtype residue when l-Tyr is the ligand and a d-Tyr specific mutant when d-Tyr is the ligand. For the third, we recover His with either ligand, instead of wildtype Gln. © 2015 Wiley Periodicals, Inc
A comparison between two-scale asymptotic expansions and Bloch wave expansions for the homogenization of periodic structures
No full textin pressInternational audienceIn this paper we make a comparison between the two-scale asymptotic expansion method for periodic homogenization and the so-called Bloch wave method. It is well-known that the homogenized tensor coincides with the Hessian matrix of the first Bloch eigenvalue when the Bloch parameter vanishes. In the context of the two-scale asymptotic expansion method, there is the notion of high order homogenized equation [5] where the homogenized equation can be improved by adding small additional higher order differential terms. The next non-zero high order term is a fourth-order term, accounting for dispersion effects (see e.g. [23], [18], [15]). Surprisingly, this homogenized fourth-order tensor is not equal to the fourth-order tensor arising in the Taylor expansion of the first Bloch eigenvalue, which is often called Burnett tensor. Here, we establish an exact relation between the homogenized fourth-order tensor and the Burnett fourth-order tensor. It was proved in [11] that the Burnett fourth-order tensor has a sign. For the special case of a simple laminate we prove that the homogenized fourth-order tensor may change sign. In the elliptic case we explain the difference between the homogenized and Burnett fourth-order tensors by a difference in the source term which features an additional corrector term. Finally, for the wave equation, the two fourth-order tensors coincide again, so dispersion is unambiguously defined, and only the source terms differ as in the elliptic case
Estimation of passive and active properties in the human heart using 3D tagged MRI
No full textInternational audienceAdvances in medical imaging and image processing are paving the way for personalised cardiac biomechani-cal modelling. Models provide the capacity to relate kinematics to dynamics and—through patient-specific modelling— derived material parameters to underlying cardiac muscle pathologies. However, for clinical utility to be achieved, model-based analyses mandate robust model selection and parameterisation. In this paper, we introduce a patient-specific biomechanical model for the left ventricle aiming to balance model fidelity with parameter identifiability. Using non-invasive data and common clinical surrogates, we illustrate unique identifiability of passive and active parameters over the full cardiac cycle. Identifiability and accuracy of the estimates in the presence of controlled noise are verified with a number of in silico datasets. Unique parametrisation is then obtained for three datasets acquired in vivo. The model predictions show good agreement with the data extracted from the images providing a pipeline for personalised biomechan-ical analysis
Severe convection in the Mediterranean from microwave observations and a convection-permitting model
No full textInternational audienceThis study investigates severe convection in the Mediterranean during the first Special Observation Period (SOP-1; 5 September to 6 November 2012) of the Hydrological Cycle in the Mediterranean Experiment (HyMeX) with the objectives of providing novel information about severe convection on its vertical structure, spatio-temporal variability as well as evaluating the ability of a convection-permitting model to reproduce this variability. Two criteria, namely deep convection (DC) and convective overshooting (COV), are computed using the water vapour channels of the Microwave Humidity Sounder (MHS). Special attention is paid to the COV as it is associated with particularly severe weather. For the first time, the COV criterion was assessed in the Mediterranean, using two case-studies conjointly observed by the airborne RASTA radar and MHS. COV is characterised by high ice water content (up to 2 g m−3) in the mid and upper troposphere (up to 12.5 km in the stratosphere). During the SOP-1, DC and COV occurred about 0.1 and 0.03% of the total observation time, respectively. The Atlantic weather regimes appear to affect the temporal distribution of these convective events. Most of the DC and COV occurrences were found along the western coasts of Italy and Greece, mainly during the 10–15 October and 25 October–3 November episodes. These two episodes, for which severe meteorological events (e.g. tornadoes) were reported, are significant when compared with the 2002–2013 climatology (above the 75th percentile). Both criteria are also employed to assess the current ability of the Meso-NH model to forecast severe convection using a model-to-satellite approach. The forecast DC and COV are found to be highly correlated in time with the observations, but are strongly underestimated. This suggests that the model missed a significant part of the most intense convective events and their associated hazards, and underlines the need for better characterisation of model uncertainties associated with severe convection
Precise measurement of the top quark mass in dilepton decays using optimized neutrino weighting
No full text10 pages, 2 figures, 2 tables, subm. to Phys. Lett. B ; see paper for full list of authorsInternational audienceWe measure the top quark mass in dilepton final states of top-antitop events in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using data corresponding to an integrated luminosity of 9.7 fb^-1 at the Fermilab Tevatron Collider. The analysis features a comprehensive optimization of the neutrino weighting method to minimize the statistical uncertainties. We also improve the calibration of jet energies using the calibration determined in top-antitop to lepton+jets events, which reduces the otherwise limiting systematic uncertainty from the jet energy scale. The measured top quark mass is mt = 173.32 +/- 1.36(stat) +/- 0.85(syst) GeV
An incremental variational formulation for the prediction of the effective work-hardening behavior and field statistics of elasto-(visco)plastic composites
No full textInternational audienceA new nonlinear and variational homogenization procedure that incorporates the fluctuations of the plastic strains within the phases is proposed to assess the local and effective responses of elasto-(visco)plastic composites with local work-hardening. The formulation is an extension of the EIV approach of Lahellec and Suquet (2007a) initially proposed for elasto-viscoplastic composites without both threshold and hardening. This extension relies both on an appropriate linearization of the stored-energy function which accounts for the isotropic and kinematic hardening and an incorporation of the elastic unloading. The accuracy of the approach is then assessed by comparisons with reference numerical solutions and other nonlinear homogenization schemes of the literature carried out on both porous elasto-plastic materials and several reinforced elasto-(visco)plastic composites subjected to cyclic proportional loadings