Elastic Scattering of 270 MeV 3-He Particles

This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit

Iron enhances hepatic fibrogenesis and activates TGF-β signaling in murine hepatic stellate cells

Introduction Although excess iron induces oxidative stress in the liver, it is unclear whether it directly activates the hepatic stellate cells (HSC). Methods We evaluated effects of excess iron on fibrogenesis and TGF-β signaling in murine HSC. Cells were treated with holotransferrin (0.005–5 g/L) for 24 h, with or without the iron chelator deferoxamine (10 µM). Gene expressions (α-SMA, Col1-α1, Serpine-1, TGF-β, Hif1-α, Tfrc and Slc40a1) were analyzed by qRT-PCR, while TfR1, ferroportin, ferritin, vimentin, collagen, TGF-β RII and phospho-Smad2 proteins were evaluated by immunofluorescence, western blot and ELISA. Results HSC express the iron-uptake protein TfR1, and the iron-export protein ferroportin. Holotransferrin up-regulated TfR1 expression by 1.8-fold (p<0.03) and ferritin accumulation (iron storage) by 2-fold (p<0.01), and activated HSC with 2-fold elevations (p<0.03) in α-SMA mRNA and collagen secretion, and a 1.6-fold increase (p<0.01) in vimentin protein. Moreover, holotransferrin activated the TGF-β pathway with TGF-β mRNA elevated 1.6-fold (p=0.05), and protein levels of TGF-β RII and phospho-Smad2 increased by 1.8-fold (p<0.01) and 1.6-fold (p<0.01), respectively. By contrast, iron chelation decreased ferritin levels by 30% (p<0.03), inhibited collagen secretion by 60% (p<0.01), repressed fibrogenic genes α-SMA (0.2-fold; p<0.05) and TGF-β (0.4-fold; p<0.01), and reduced levels of TGF-β RII and phospho-Smad2 proteins. Conclusion HSC express iron transport proteins. Holotransferrin (iron) activates HSC fibrogenesis and the TGF-β pathway, while iron depletion by chelation reverses this, suggesting that this could be a useful adjunct therapy for patients with fibrosis. Further studies in primary human HSC and animal models are necessary to confirm this

Vibration-induced "thermally activated" jamming transition in granular media

The quasi-static frequency response of a granular medium is measured by a forced torsion oscillator method, with forcing frequency $f_{p}$ in the range $10^{-4}$ Hz to 5 Hz, while weak vibrations at high-frequency $f_{s}$, in the range 50 Hz to 200 Hz, are generated by an external shaker. The intensity of vibration, $\Gamma$, is below the fluidization limit. A loss factor peak is observed in the oscillator response as a function of $\Gamma$ or $f_{p}$. In a plot of $\ln f_{p}$ against $1/\Gamma$, the position of the peak follows an Arrhenius-like behaviour over four orders of magnitude in $f_{p}$. The data can be described as a stochastic hopping process involving a probability factor $\exp(-\Gamma_{j}/\Gamma)$ with $\Gamma_{j}$ a $f_{s}$-dependent characteristic vibration intensity. A $f_{s}$-independent description is given by $\exp(-\tau_{j}/\tau)$, with $\tau_{j}$ an intrinsic characteristic time, and $\tau =\Gamma ^{n}/2\pi f_{s}$, n=0.5-0.6, an empirical control parameter with unit of time. $\tau$ is seen as the effective average time during which the perturbed grains can undergo structural rearrangement. The loss factor peak appears as a crossover in the dynamic behaviour of the vibrated granular system, which, at the time-scale $1/f_{p}$, is solid-like at low $\Gamma$, and the oscillator is jammed into the granular material, and is fluid-like at high $\Gamma$, where the oscillator can slide viscously.Comment: Final version to appear in PR

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

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review