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1,461 result(s) for "Lefèvre, R."
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Substrate-Dependent Trans-Stimulation of Organic Cation Transporter 2 Activity
The search of substrates for solute carriers (SLCs) constitutes a major issue, owing notably to the role played by some SLCs, such as the renal electrogenic organic cation transporter (OCT) 2 (SLC22A2), in pharmacokinetics, drug–drug interactions and drug toxicity. For this purpose, substrates have been proposed to be identified by their cis-inhibition and trans-stimulation properties towards transporter activity. To get insights on the sensitivity of this approach for identifying SLC substrates, 15 various exogenous and endogenous OCT2 substrates were analysed in the present study, using 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (DiASP) as a fluorescent OCT2 tracer substrate. All OCT2 substrates cis-inhibited DiASP uptake in OCT2-overexpressing HEK293 cells, with IC50 values ranging from 0.24 µM (for ipratropium) to 2.39 mM (for dopamine). By contrast, only 4/15 substrates, i.e., acetylcholine, agmatine, choline and metformin, trans-stimulated DiASP uptake, with a full suppression of the trans-stimulating effect of metformin by the reference OCT2 inhibitor amitriptyline. An analysis of molecular descriptors next indicated that trans-stimulating OCT2 substrates exhibit lower molecular weight, volume, polarizability and lipophilicity than non-trans-stimulating counterparts. Overall, these data indicated a rather low sensitivity (26.7%) of the trans-stimulation assay for identifying OCT2 substrates, and caution with respect to the use of such assay may therefore be considered.
Quantification and mapping of the impact of the recent air pollution abatement on limestone and window glass in Paris
The air pollution abatement consequences for limestone and window glass during the recent period (1997–2014) were quantified in Paris by a 3-step approach: (1) in-the-field measurement of pollution and climatic parameters; (2) weathering calculation by means of dose–response functions in 100 m × 100 m grid cells of the Paris plan; (3) mapping the geographic distribution of the calculated damage. In order to get a global damage estimation of different materials, a set of maps were generated: (1) the total surface of buildings and monuments façades in the part of Paris inscribed on the UNESCO List between the Ile Saint-Louis and the Concorde Square; (2) the surface of limestone and window glass of each façade; (3) the yearly spatial distribution of SO 2 , NO 2 and PM10 concentration; (4) the potential surface damage of materials in response to climatic and pollution doses. The calculated responses are in agreement with those measured in the field during several campaigns of exposure of limestone and window glass in Paris performed during the same period; (5) the effective damage to limestone and window glass. The decreases of the potential and of the effective damage are quantified and mapped. They are driven by the decrease in air pollutant concentrations.
On the corrosion and soiling effects on materials by air pollution in Athens, Greece
In the frame of the European project, entitled MULTI-ASSESS, specimens of structural metals, glass, stone and concrete materials were exposed to air pollution at a station, which was installed for this purpose on a building, located in the centre of Athens. The main purpose of this project was to determine the corrosion and soiling effects of air pollution on materials. A set of the specimens was exposed in a position that was sheltered from rain and partly from wind, and another set was exposed in unsheltered positions on the roof of the above said building. In addition, other specimens were exposed at different heights on the same building, in order to investigate for the first time the corrosion and soiling effects on various materials as a function of height. For the determination of these effects, chemical analysis of the specimens was performed and basic parameters as the weight change, the layer thickness and the optical properties were calculated. Finally, the results obtained are discussed and their plausible interpretation is attempted.
Test of lepton universality in beauty-quark decays
The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton–proton collision data collected with the LHCb detector at CERN’s Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons. The Large Hadron Collider beauty collaboration reports a test of lepton flavour universality in decays of bottom mesons into strange mesons and a charged lepton pair, finding evidence of a violation of this principle postulated in the standard model.
Test of lepton universality with B0 → K0ℓ+ℓ− decays
A bstract A test of lepton universality, performed by measuring the ratio of the branching fractions of the B 0 → K *0 μ + μ − and B 0 → K *0 e + e − decays, R K * 0 , is presented. The K *0 meson is reconstructed in the final state K + π − , which is required to have an invariant mass within 100 MeV /c 2 of the known K * (892) 0 mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb −1 , collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared, q 2 , to be R K * 0 = 0.66 − + 0.07 0.11 stat ± 0.03 syst f o r 0.045 < q 2 < 1.1 GeV 2 / c 4 , 0.69 − + 0.07 0.11 stat ± 0.05 syst f o r 1.1 < q 2 < 6.0 GeV 2 / c 4 . The corresponding 95.4% confidence level intervals are [0 . 52 , 0 . 89] and [0 . 53 , 0 . 94]. The results, which represent the most precise measurements of R K * 0 to date, are compatible with the Standard Model expectations at the level of 2.1–2.3 and 2.4–2.5 standard deviations in the two q 2 regions, respectively.
Angular analysis of the B0 → K0μ+μ− decay using 3 fb−1 of integrated luminosity
A bstract An angular analysis of the B 0 → K *0 (→ K + π − ) μ + μ − decay is presented. The dataset corresponds to an integrated luminosity of 3.0 fb −1 of pp collision data collected at the LHCb experiment. The complete angular information from the decay is used to determine CP -averaged observables and CP asymmetries, taking account of possible contamination from decays with the K + π − system in an S-wave configuration. The angular observables and their correlations are reported in bins of q 2 , the invariant mass squared of the dimuon system. The observables are determined both from an unbinned maximum likelihood fit and by using the principal moments of the angular distribution. In addition, by fitting for q 2 -dependent decay amplitudes in the region 1.1 < q 2 < 6.0 GeV 2 / c 4 , the zero-crossing points of several angular observables are computed. A global fit is performed to the complete set of CP -averaged observables obtained from the maximum likelihood fit. This fit indicates differences with predictions based on the Standard Model at the level of 3.4 standard deviations. These differences could be explained by contributions from physics beyond the Standard Model, or by an unexpectedly large hadronic effect that is not accounted for in the Standard Model predictions.
Angular analysis of the rare decay Bs0→ ϕμ+μ
A bstract An angular analysis of the rare decay B s 0 → ϕμ + μ − is presented, using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 8.4 fb − 1 . The observables describing the angular distributions of the decay B s 0 → ϕμ + μ − are determined in regions of q 2 , the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.
Differential branching fractions and isospin asymmetries of B → K()μ+μ− decays
A bstract The isospin asymmetries of B → Kμ + μ − and B → K * μ + μ − decays and the partial branching fractions of the B 0 → K 0 μ + μ − , B + → K + μ + μ − and B + → K *+ μ + μ − decays are measured as functions of the dimuon mass squared, q 2 . The data used correspond to an integrated luminosity of 3 fb −1 from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions favour lower values than their respective theoretical predictions, however they are all individually consistent with the Standard Model.
Measurements of prompt charm production cross-sections in pp collisions at s=13 TeV
A bstract Production cross-sections of prompt charm mesons are measured with the first data from pp collisions at the LHC at a centre-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 4.98 ± 0.19 pb −1 collected by the LHCb experiment. The production cross-sections of D 0 , D + , D s + , and D *+ mesons are measured in bins of charm meson transverse momentum, p T , and rapidity, y , and cover the range 0 < p T < 15GeV/c and 2.0 < y < 4.5. The inclusive cross-sections for the four mesons, including charge conjugation, within the range of 1 < p T < 8 GeV/c are found to be σ pp → D 0 X = 2460 ± 3 ± 130 μ b σ pp → D + X = 1000 ± 3 ± 110 μ b σ pp → D s + X = 460 ± 13 ± 100 μ b σ pp → D ∗ + X = 880 ± 5 ± 140 μ b where the uncertainties are due to statistical and systematic uncertainties, respectively.
Angular analysis and differential branching fraction of the decay Bs0 → ϕμ+μ
A bstract An angular analysis and a measurement of the differential branching fraction of the decay B s 0  →  ϕμ + μ − are presented, using data corresponding to an integrated luminosity of 3 . 0 fb −1 of pp collisions recorded by the LHCb experiment at s = 7 and 8 TeV. Measurements are reported as a function of q 2 , the square of the dimuon invariant mass and results of the angular analysis are found to be consistent with the Standard Model. In the range 1 < q 2 < 6 GeV 2 /c 4 , where precise theoretical calculations are available, the differential branching fraction is found to be more than 3 σ below the Standard Model predictions.