Membranous glomerulonephritis in the mouse

Membranous glomerulonephritis in the mouse. Glomerulonephritis was induced in C57.B110 mice by a single injection of rabbit IgG against homologous, pronase-digested, renal tubular antigens. The heterologous phase was characterized by a transient increase of glomerular permeability with fixation of rabbit IgG to the capillary walls, in a linear or fine-granular pattern, and to the brush borders of the proximal tubuli. The autologous phase was marked by the immune response to the injected protein, during which subepithelial immune deposits, consisting of mouse IgG1, rabbit IgG, and mouse C3 developed. Small amounts were still present at 1 year after the injection of antiserum. The antibody response of the mice correlated with the development and resolution of the deposits. None of the mice developed a nephrotic syndrome. Control mice treated with normal rabbit IgG did not show immune deposits in their kidneys at any stage despite a comparable antibody response to rabbit IgG. Immunoelectronmicroscopy showed that the rabbit antibodies fixed directly to an antigen in the cell membrane of the glomerular visceral epithelium. It seems, therefore, likely that in situ formation of subepithelial immune complexes occurred in the autologous phase by fixation of mouse immunoglobulins to rabbit IgG already present in the glomerular wall.Glomérulonéphrite extra-membraneuse chez la souris. Une glomérulonéphrite a été induite chez des souris C57.B110 par une injection unique d'IgG de lapin contre des antigènes tubulaires rénaux homologues, digérés par de la pronase. La phase hétérologue était caractérisée par une augmentation transitoire de la perméabilité glomérulaire avec fixation d'IgG de lapin aux parois capillaires, d'une façon linéaire ou finement granuleuse, et aux bordures en brosse des tubules proximaux. La phase autologue était marquée par la réponse immune à la protéine injectée, pendant laquelle des dépôts immuns sous-épithéliaux, consistant en de l'IgG1 de souris, de l'IgG de lapin et du C3 de souris, se sont développés. Il en restait encore de faibles quantités 1 an après l'injection de l'antisérum. La réponse anticorps des souris était corrélée avec le développement et la disparition des dépôts. Aucune des souris n'a développé de syndrome néphrotique. Les souris contrôles traitées avec de l'IgG de lapin normal n'ont pas eu de dépôts immuns dans le rein à aucun stade, malgré une réponse anticorps aux IgG de lapin comparable. La microscopie immuno-électronique a montré que les anticorps de lapin se fixaient directement à un antigène situé sur la membrane des cellules de l'épithélium viscéral glomérulaire. Il semble donc probable que la formation in situ de complexes immuns sous-épithéliaux est survenue à la phase autologue par fixation d'immunoglobulines de souris à de l'IgG de lapin déjà présente dans la paroi glomérulaire

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Operation and performance of the ATLAS semiconductor tracker

The semiconductor tracker is a silicon microstrip detector forming part of the inner tracking system of the ATLAS experiment at the LHC. The operation and performance of the semiconductor tracker during the first years of LHC running are described. More than 99% of the detector modules were operational during this period, with an average intrinsic hit efficiency of (99.74±0.04)%. The evolution of the noise occupancy is discussed, and measurements of the Lorentz angle, δ-ray production and energy loss presented. The alignment of the detector is found to be stable at the few-micron level over long periods of time. Radiation damage measurements, which include the evolution of detector leakage currents, are found to be consistent with predictions and are used in the verification of radiation background simulations

Measurement of the cross section of high transverse momentum Z→bb̄ production in proton–proton collisions at √s = 8 TeV with the ATLAS detector

This Letter reports the observation of a high transverse momentum Z→bb̄ signal in proton–proton collisions at √s=8 TeV and the measurement of its production cross section. The data analysed were collected in 2012 with the ATLAS detector at the LHC and correspond to an integrated luminosity of 19.5 fb−¹. The Z→bb̄ decay is reconstructed from a pair of b -tagged jets, clustered with the anti-ktkt jet algorithm with R=0.4R=0.4, that have low angular separation and form a dijet with pT>200 GeVpT>200 GeV. The signal yield is extracted from a fit to the dijet invariant mass distribution, with the dominant, multi-jet background mass shape estimated by employing a fully data-driven technique that reduces the dependence of the analysis on simulation. The fiducial cross section is determined to be σZ→bb¯fid=2.02±0.20 (stat.) ±0.25 (syst.)±0.06 (lumi.) pb=2.02±0.33 pb, in good agreement with next-to-leading-order theoretical predictions

Measurement of event-shape observables in Z→ℓ+ℓ− events in pp collisions at √ s=7 TeV with the ATLAS detector at the LHC

Event-shape observables measured using charged particles in inclusive $Z$-boson events are presented, using the electron and muon decay modes of the $Z$ bosons. The measurements are based on an integrated luminosity of $1.1 {\rm fb}^{-1}$ of proton--proton collisions recorded by the ATLAS detector at the LHC at a centre-of-mass energy $\sqrt{s}=7$ TeV. Charged-particle distributions, excluding the lepton--antilepton pair from the $Z$-boson decay, are measured in different ranges of transverse momentum of the $Z$ boson. Distributions include multiplicity, scalar sum of transverse momenta, beam thrust, transverse thrust, spherocity, and $\mathcal{F}$-parameter, which are in particular sensitive to properties of the underlying event at small values of the $Z$-boson transverse momentum. The Sherpa event generator shows larger deviations from the measured observables than Pythia8 and Herwig7. Typically, all three Monte Carlo generators provide predictions that are in better agreement with the data at high $Z$-boson transverse momenta than at low $Z$-boson transverse momenta and for the observables that are less sensitive to the number of charged particles in the event.Comment: 36 pages plus author list + cover page (54 pages total), 14 figures, 4 tables, submitted to EPJC, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-0

Evidence for the associated production of a W boson and a top quark in ATLAS at √s = 7 TeV

Contains fulltext : 103353.pdf (preprint version ) (Open Access

Search for supersymmetry in events with photons, bottom quarks, and missing transverse momentum in proton-proton collisions at a centre-of-mass energy of 7 TeV with the ATLAS detector

Contains fulltext : 111247.pdf (preprint version ) (Open Access