| 1. |
- Aad, G., et al.
(författare)
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Readiness of the ATLAS Tile Calorimeter for LHC collisions
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:4, s. 1193-1236
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Tidskriftsartikel (refereegranskat)abstract
- The Tile hadronic calorimeter of the ATLAS detector has undergone extensive testing in the experimental hall since its installation in late 2005. The readout, control and calibration systems have been fully operational since 2007 and the detector has successfully collected data from the LHC single beams in 2008 and first collisions in 2009. This paper gives an overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data. The detector operation status, noise characteristics and performance of the calibration systems are presented, as well as the validation of the timing and energy calibration carried out with minimum ionising cosmic ray muons data. The calibration systems' precision is well below the design value of 1%. The determination of the global energy scale was performed with an uncertainty of 4%.
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| 2. |
- Aad, G., et al.
(författare)
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Studies of the performance of the ATLAS detector using cosmic-ray muons
- 2011
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 71:3
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Tidskriftsartikel (refereegranskat)abstract
- Muons from cosmic-ray interactions in the atmosphere provide a high-statistics source of particles that can be used to study the performance and calibration of the ATLAS detector. Cosmic-ray muons can penetrate to the cavern and deposit energy in all detector subsystems. Such events have played an important role in the commissioning of the detector since the start of the installation phase in 2005 and were particularly important for understanding the detector performance in the time prior to the arrival of the first LHC beams. Global cosmic-ray runs were undertaken in both 2008 and 2009 and these data have been used through to the early phases of collision data-taking as a tool for calibration, alignment and detector monitoring. These large datasets have also been used for detector performance studies, including investigations that rely on the combined performance of different subsystems. This paper presents the results of performance studies related to combined tracking, lepton identification and the reconstruction of jets and missing transverse energy. Results are compared to expectations based on a cosmic-ray event generator and a full simulation of the detector response.
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| 3. |
- Aad, G., et al.
(författare)
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The ATLAS Inner Detector commissioning and calibration
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:3, s. 787-821
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Tidskriftsartikel (refereegranskat)abstract
- The ATLAS Inner Detector is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field. Its installation was completed in August 2008 and the detector took part in data-taking with single LHC beams and cosmic rays. The initial detector operation, hardware commissioning and in-situ calibrations are described. Tracking performance has been measured with 7.6 million cosmic-ray events, collected using a tracking trigger and reconstructed with modular pattern-recognition and fitting software. The intrinsic hit efficiency and tracking trigger efficiencies are close to 100%. Lorentz angle measurements for both electrons and holes, specific energy-loss calibration and transition radiation turn-on measurements have been performed. Different alignment techniques have been used to reconstruct the detector geometry. After the initial alignment, a transverse impact parameter resolution of 22.1 +/- 0.9 mu m and a relative momentum resolution sigma (p) /p=(4.83 +/- 0.16)x10(-4) GeV(-1)xp (T) have been measured for high momentum tracks.
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| 4. |
- Aad, G., et al.
(författare)
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The ATLAS Simulation Infrastructure
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:3, s. 823-874
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Tidskriftsartikel (refereegranskat)abstract
- The simulation software for the ATLAS Experiment at the Large Hadron Collider is being used for large-scale production of events on the LHC Computing Grid. This simulation requires many components, from the generators that simulate particle collisions, through packages simulating the response of the various detectors and triggers. All of these components come together under the ATLAS simulation infrastructure. In this paper, that infrastructure is discussed, including that supporting the detector description, interfacing the event generation, and combining the GEANT4 simulation of the response of the individual detectors. Also described are the tools allowing the software validation, performance testing, and the validation of the simulated output against known physics processes.
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| 5. |
- Aad, G., et al.
(författare)
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Commissioning of the ATLAS Muon Spectrometer with cosmic rays
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:3, s. 875-916
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Tidskriftsartikel (refereegranskat)abstract
- The ATLAS detector at the Large Hadron Collider has collected several hundred million cosmic ray events during 2008 and 2009. These data were used to commission the Muon Spectrometer and to study the performance of the trigger and tracking chambers, their alignment, the detector control system, the data acquisition and the analysis programs. We present the performance in the relevant parameters that determine the quality of the muon measurement. We discuss the single element efficiency, resolution and noise rates, the calibration method of the detector response and of the alignment system, the track reconstruction efficiency and the momentum measurement. The results show that the detector is close to the design performance and that the Muon Spectrometer is ready to detect muons produced in high energy proton-proton collisions.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Bergeås Kuutmann, Elin, et al.
(författare)
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Measurement of Pion and Proton Response and Longitudinal Shower Profiles up to 20 Nuclear Interaction Lengths with the ATLAS Tile Calorimeter
- 2010
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 615:2, s. 158-181
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Tidskriftsartikel (refereegranskat)abstract
- The response of pions and protons in the energy range of 20–180 GeV, produced at CERN's SPS H8 test-beam line in the ATLAS iron–scintillator Tile hadron calorimeter, has been measured. The test-beam configuration allowed the measurement of the longitudinal shower development for pions and protons up to 20 nuclear interaction lengths. It was found that pions penetrate deeper in the calorimeter than protons. However, protons induce showers that are wider laterally to the direction of the impinging particle. Including the measured total energy response, the pion-to-proton energy ratio and the resolution, all observations are consistent with a higher electromagnetic energy fraction in pion-induced showers. The data are compared with GEANT4 simulations using several hadronic physics lists. The measured longitudinal shower profiles are described by an analytical shower parametrization within an accuracy of 5–10%. The amount of energy leaking out behind the calorimeter is determined and parametrized as a function of the beam energy and the calorimeter depth. This allows for a leakage correction of test-beam results in the standard projective geometry.
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| 12. |
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| 13. |
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| 14. |
- Edling, Christer, et al.
(författare)
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Positron emission tomography studies of healthy volunteers : No effects on the dopaminergic terminals and synthesis after short-term exposure to toluene
- 1997
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Ingår i: Human and Experimental Toxicology. - : SAGE Publications. - 0960-3271 .- 1477-0903. ; 16:3, s. 171-176
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Tidskriftsartikel (refereegranskat)abstract
- Despite extensive research, the mechanisms for the effects of organic solvents on the central nervous system are still unknown. One mechanism proposed is that solvents interfere with the synthesis of neurotransmitters. In the present study 11 male healthy volunteers were exposed during 15 min to 100 p.p.m. toluene at light physical exercise, and the dopamine decarboxylase activity and number of terminals in putamen were measured before and after exposure by positron emission tomography. Two different tracers were used [beta-11C]L-DOPA for decarboxylase activity during the in vivo synthesis of dopamine, and [11C]nomifensine to estimate the number of terminals. Although there was a slight increase in the rate of dopamine synthesis in the putamen after the exposure, this difference was not statistically significant (P = 0.4). No effect was observed with regard to the uptake of nomifensine. There was no significant relationship between the dose of toluene and rate of dopamine synthesis, and no significant correlation between the time from end of exposure to start of the PET-camera and DOPA. Our findings indicate that short term exposure to 100 p.p.m. of toluene does not affect the rate of dopamine synthesis or the number of presynaptic terminals.
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| 15. |
- Åsman, Barbro, et al.
(författare)
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A Search for New Physics in Dijet Mass and Angular Distributions in 36 pb$^{-1}$ of $pp$ Collisions at $\sqrt{s}=7$ TeV Measured with the ATLAS Detector
- 2011
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 13, s. 053044-
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Tidskriftsartikel (refereegranskat)abstract
- A search for new interactions and resonances produced in LHC proton-proton (pp) collisions at a centre-of-mass energy root s = 7 TeV was performed with the ATLAS detector. Using a dataset with an integrated luminosity of 36 pb(-1), dijet mass and angular distributions were measured up to dijet masses of similar to 3.5 TeV and were found to be in good agreement with Standard Model predictions. This analysis sets limits at 95% CL on various models for new physics: an excited quark is excluded for mass between 0.60 and 2.64 TeV, an axigluon hypothesis is excluded for axigluon masses between 0.60 and 2.10 TeV and quantum black holes are excluded in models with six extra space-time dimensions for quantum gravity scales between 0.75 and 3.67 TeV. Production cross section limits as a function of dijet mass are set using a simplified Gaussian signal model to facilitate comparisons with other hypotheses. Analysis of the dijet angular distribution using a novel technique simultaneously employing the dijet mass excludes quark contact interactions with a compositeness scale 3 below 9.5 TeV.
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| 16. |
- Åsman, Barbro, et al.
(författare)
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Measurement of the $W\to\ell\nu$ and $Z/gamma^\ast\to\ell\ell$ Production Cross Sections in Proton-Proton Collisions at $\sqrt{s}=7$ TeV with the ATLAS Detector
- 2010
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :12, s. 060-
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Tidskriftsartikel (refereegranskat)abstract
- First measurements of the W → ℓν and Z/γ * → ℓℓ (ℓ = e, μ) production cross sections in proton-proton collisions at Ös = 7 \textTeV s=7TeV are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W → ℓν and 179 Z/γ * → ℓℓ candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb. The measured total W and Z/γ ∗-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels are sW\texttot Wtot. BR(W → ℓν) = 9.96 ± 0.23(stat) ± 0.50(syst) ± 1.10(lumi) nb and sZ / g \texttot totZ BR(Z/γ ∗ → ℓℓ) = 0.82 ± 0.06 (stat) ± 0.05 (syst) ± 0.09(lumi) nb (within the invariant mass window 66 < m ℓℓ < 116GeV). The W/Z cross-section ratio is measured to be 11.7 ± 0.9(stat) ± 0.4(syst). In addition, measurements of the W + and W − production cross sections and of the lepton charge asymmetry are reported. Theoretical predictions based on NNLO QCD calculations are found to agree with the measurements
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| 17. |
- Åsman, Barbro, et al.
(författare)
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Search for the Standard Model Higgs boson in the decay channel H -> ZZ((*)) -> 4l with 4.8 fb(-1) of pp collision data at root s=7 TeV with ATLAS
- 2012
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 710:3, s. 383-402
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Tidskriftsartikel (refereegranskat)abstract
- This Letter presents a search for the Standard Model Higgs boson in the decay channel H -> ZZ((*)) -> l(+)l(-)l(-)+l(')-, where l,l' = e or mu, using proton-proton collisions at root s = 7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb(-1). The four-lepton invariant mass distribution is compared with Standard Model background expectations to derive upper limits on the cross section of a Standard Model Higgs boson with a mass between 110 GeV and 600 GeV. The mass ranges 134-156 GeV, 182-233 GeV, 256-265 GeV and 268-415 GeV are excluded at the 95% confidence level. The largest upward deviations from the background-only hypothesis are observed for Higgs boson masses of 125 GeV, 244 GeV and 500 GeV with local significances of 2.1, 2.2 and 2.1 standard deviations, respectively. Once the look-elsewhere effect is considered, none of these excesses are significant.
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| 18. |
- Aad, G., et al.
(författare)
-
- 2012
-
Tidskriftsartikel (refereegranskat)
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| 19. |
- Aad, G., et al.
(författare)
-
- 2012
-
Tidskriftsartikel (refereegranskat)
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| 20. |
- Aad, G., et al.
(författare)
-
- 2012
-
Tidskriftsartikel (refereegranskat)
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| 21. |
- Aad, G., et al.
(författare)
-
- 2013
-
Tidskriftsartikel (refereegranskat)
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| 22. |
- Aad, G., et al.
(författare)
-
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; :9
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Tidskriftsartikel (refereegranskat)
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| 23. |
- Aad, G., et al.
(författare)
-
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; :7
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Tidskriftsartikel (refereegranskat)
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| 24. |
- Aad, G., et al.
(författare)
-
- 2012
-
Ingår i: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; :9
-
Tidskriftsartikel (refereegranskat)
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| 25. |
- Aad, G., et al.
(författare)
-
- 2012
-
Ingår i: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; :9
-
Tidskriftsartikel (refereegranskat)
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| 26. |
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| 27. |
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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
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| 36. |
- Aad, G., et al.
(författare)
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The ATLAS Experiment at the CERN Large Hadron Collider
- 2008
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 3:S08003
-
Forskningsöversikt (refereegranskat)abstract
- The ATLAS detector as installed in its experimental cavern at point 1 at CERN is described in this paper. A brief overview of the expected performance of the detector when the Large Hadron Collider begins operation is also presented.
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| 37. |
- Abata, E., et al.
(författare)
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Study of energy response and resolution of the ATLAS barrel calorimeter to hadrons of energies from 20 to 350 GeV
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 621:1-3, s. 134-150
-
Tidskriftsartikel (refereegranskat)abstract
- A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20-350 GeV and beam impact points and angles corresponding to pseudo-rapidity values in the range 0.2-0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit. (C) 2010 Published by Elsevier B.V.
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| 38. |
- Abdallah, J., et al.
(författare)
-
Mechanical construction and installation of the ATLAS tile calorimeter
- 2013
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 8, s. T11001-
-
Tidskriftsartikel (refereegranskat)abstract
- This paper summarises the mechanical construction and installation of the Tile Calorimeter for the ATLAS experiment at the Large Hadron Collider in CERN, Switzerland. The Tile Calorimeter is a sampling calorimeter using scintillator as the sensitive detector and steel as the absorber and covers the central region of the ATLAS experiment up to pseudorapidities +/- 1.7. The mechanical construction of the Tile Calorimeter occurred over a period of about 10 years beginning in 1995 with the completion of the Technical Design Report and ending in 2006 with the installation of the final module in the ATLAS cavern. During this period approximately 2600 metric tons of steel were transformed into a laminated structure to form the absorber of the sampling calorimeter. Following instrumentation and testing, which is described elsewhere, the modules were installed in the ATLAS cavern with a remarkable accuracy for a structure of this size and weight.
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| 39. |
- Abdallah, J., et al.
(författare)
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The optical instrumentation of the ATLAS Tile Calorimeter
- 2013
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 8, s. P01005-
-
Tidskriftsartikel (refereegranskat)abstract
- The Tile Calorimeter, covering the central region of the ATLAS experiment up to pseudorapidities of +/-1.7, is a sampling device built with scintillating tiles that alternate with iron plates. The light is collected in wave-length shifting (WLS) fibers and is read out with photomultipliers. In the characteristic geometry of this calorimeter the tiles lie in planes perpendicular to the beams, resulting in a very simple and modular mechanical and optical layout. This paper focuses on the procedures applied in the optical instrumentation of the calorimeter, which involved the assembly of about 460,000 scintillator tiles and 550,000 WLS fibers. The outcome is a hadronic calorimeter that meets the ATLAS performance requirements, as shown in this paper.
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| 40. |
- Abrikosov, Igor A., et al.
(författare)
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Finite Temperature, Magnetic, and Many-Body Effects in Ab Initio Simulations of Alloy Thermodynamics
- 2013
-
Ingår i: TMS2013 Supplemental Proceedings. - Hoboken, NJ, USA : John Wiley & Sons. - 9781118605813 - 9781118663547 ; , s. 617-626
-
Bokkapitel (refereegranskat)abstract
- Ab initio electronic structure theory is known as a useful tool for prediction of materials properties. However, majority of simulations still deal with calculations in the framework of density functional theory with local or semi-local functionals carried out at zero temperature. We present new methodological solution.s, which go beyond this approach and explicitly take finite temperature, magnetic, and many-body effects into account. Considering Ti-based alloys, we discuss !imitations of the quasiharmonic approximation for the treatment of lattice vibrations, and present an accurate and easily extendable method to calculate free ,energies of strongly anharmonic solids. We underline the necessity to going beyond the state-of-the-art techniques for the determination of effective cluster interactions in systems exhibiting mctal-to-insulator transition, and describe a unified cluster expansion approach developed for this class of materials. Finally, we outline a first-principles method, disordered local moments molecular dynamics, for calculations of thermodynamic properties of magnetic alloys, like Cr1-x,.AlxN, in their high-temperature paramagnetic state. Our results unambiguously demonstrate importance of finite temperature effects in theoretical calculations ofthermodynamic properties ofmaterials.
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| 41. |
- Al Shemaili, Jasem, et al.
(författare)
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Frondoside A enhances the antiproliferative effects of gemcitabine in pancreatic cancer
- 2014
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Ingår i: European Journal of Cancer. - : Elsevier BV. - 0959-8049 .- 1879-0852. ; 50:7, s. 1391-1398
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Tidskriftsartikel (refereegranskat)abstract
- Pancreatic cancer has a very poor prognosis. While gemcitabine is the mainstay of therapy and improves quality of life, it has little impact on survival. More effective treatments are desperately needed for this disease. Frondoside A is a triterpenoid glycoside isolated from the Atlantic sea cucumber, Cucumaria frondosa. Frondoside A potently inhibits pancreatic cancer cell growth and induces apoptosis in vitro and in vivo. The aim of the present study was to investigate whether frondoside A could enhance the anti-cancer effects of gemcitabine. Effects of frondoside A and gemcitabine alone and in combination on proliferation were investigated in two human pancreatic cancer cell lines, AsPC-1 and S2013. To investigate possible synergistic effects, combinations of low concentrations of the two drugs were used for a 72 h treatment period in vitro. Growth inhibition was significantly greater with the drug combinations than their additive effects. Combinations of frondoside A and gemcitabine were tested in vivo using the athymic mouse model. Xenografts of AsPC-1 and S2013 cells were allowed to form tumours prior to treatment with the drugs alone or in combination for 30 days. Tumours grew rapidly in placebo-treated animals. Tumour growth was significantly reduced in all treatment groups. At the lowest dose tested, gemcitabine (4 mg/kg/dose), combined with frondoside A (100 mu g/kg/day) was significantly more effective than with either drug alone. To conclude: The present data suggest that combinations of frondoside A and gemcitabine may provide clinical benefit for patients with pancreatic cancer.
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| 42. |
- Al Shemaili, Jasem, et al.
(författare)
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Pharmacokinetics in Mouse and Comparative Effects of Frondosides in Pancreatic Cancer
- 2016
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Ingår i: Marine Drugs. - : MDPI AG. - 1660-3397. ; 14:6
-
Tidskriftsartikel (refereegranskat)abstract
- The frondosides are triterpenoid glycosides from the Atlantic sea cucumber Cucumaria frondosa. Frondoside A inhibits growth, invasion, metastases and angiogenesis and induces apoptosis in diverse cancer types, including pancreatic cancer. We compared the growth inhibitory effects of three frondosides and their aglycone and related this to the pharmocokinetics and route of administration. Frondoside A potently inhibited growth of pancreatic cancer cells with an EC50 of similar to 1 mu M. Frondoside B was less potent (EC50 similar to 2.5 mu M). Frondoside C and the aglycone had no effect. At 100 mu g/kg, frondoside A administered to CD2F1 mice as an i.v. bolus, the Cp-max was 129 nM, Cl-tb was 6.35 mL/min/m(2), and half-life was 510 min. With i.p. administration the Cp-max was 18.3 nM, Cl-tb was 127 mL/min/m(2) and half-life was 840 min. Oral dosing was ineffective. Frondoside A (100 mu g/kg/day i.p.) markedly inhibited growth cancer xenografts in nude mice. The same dose delivered by oral gavage had no effect. No evidence of acute toxicity was seen with frondoside A. Frondoside A is more potent inhibitor of cancer growth than other frondosides. The glycoside component is essential for bioactivity. Frondoside A is only effective when administered systemically. Based on the current and previous studies, frondoside A appears safe and may be valuable in the treatment of cancer.
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| 43. |
- Alling, Björn, et al.
(författare)
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Dynamic and structural stability of cubic vanadium nitride
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 91:5, s. 054101-
-
Tidskriftsartikel (refereegranskat)abstract
- Structural phase transitions in epitaxial stoichiometric VN/MgO(011) thin films are investigated using temperature-dependent synchrotron x-ray diffraction (XRD), selected-area electron diffraction (SAED), resistivity measurements, high-resolution cross-sectional transmission electron microscopy, and ab initio molecular dynamics (AIMD). At room temperature, VN has the B1 NaCl structure. However, below T-c = 250 K, XRD and SAED results reveal forbidden (00l) reflections of mixed parity associated with a noncentrosymmetric tetragonal structure. The intensities of the forbidden reflections increase with decreasing temperature following the scaling behavior I proportional to (T-c - T)(1/2). Resistivity measurements between 300 and 4 K consist of two linear regimes resulting from different electron/phonon coupling strengths in the cubic and tetragonal-VN phases. The VN transport Eliashberg spectral function alpha F-2(tr)(h omega), the product of the phonon density of states F(h omega) and the transport electron/phonon coupling strength alpha(2)(tr)(h omega), is determined and used in combination with AIMD renormalized phonon dispersion relations to show that anharmonic vibrations stabilize the NaCl structure at T greater than T-c. Free-energy contributions due to vibrational entropy, often neglected in theoretical modeling, are essential for understanding the room-temperature stability of NaCl-structure VN, and of strongly anharmonic systems in general.
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| 44. |
- Andersson, Björn, 1985, et al.
(författare)
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Nitrogen fixation in shallow-water sediments: Spatial distribution and controlling factors
- 2014
-
Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 59:6, s. 1932-1944
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogenase activity (NA) in shallow-water (< 1 m) sediments was investigated at 60 randomly selected sites along a 150 km stretch on the brackish-water Swedish west coast, without targeting any specific type of sediments, such as microbial mats. Benthic nitrogen (N) fixation and diazotrophs (nifH genes) were found at all sites, regardless of the presence of cyanobacterial or microbial mats. The majority of sites showed N fixation rates between 0.03 and 1 mmol N m−2 d−1. These rates were similar to those of benthic denitrification previously measured in the area. Maximum rates up to 3.4 mmol N m−2 d−1 were measured. A structural equation model was used to investigate direct and indirect effects of biogeochemical and physical factors on NA. Number of nifH genes had the largest direct positive influence on NA, whereas increasing wave exposure had an indirect negative effect on NA through its influence on the diazotrophic abundance. Increased salinity, previously been shown to suppress NA in coastal waters, was found to directly stimulate benthic N fixation, likely by generating favorable conditions for diazotrophic sulfate-reducing bacteria. Our field data confirmed previously observed negative effects of dissolved inorganic nitrogen on NA, which have so far mainly been experimentally studied. Both NA rates and the number of nifH genes correlated positively with pore-water dissolved inorganic phosphorus concentrations. These findings show that the potential for N fixation in illuminated sediments can be considerable, stretching beyond cyanobacterial mats, being controlled by complex interactions between biotic and abiotic factors.
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| 45. |
- Andersson, Helén, 1982-, et al.
(författare)
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Low levels of the air pollutant 1-nitropyrene induce DNA damage, increased levels of reactive oxygen species and endoplasmic reticulum stress in human endothelial cells
- 2009
-
Ingår i: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 262:1, s. 57-64
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Tidskriftsartikel (refereegranskat)abstract
- Both epidemiological and experimental studies suggest that exposure to high levels of air pollution is a risk factor associated with cardiovascular disease. Traffic emission is a major source of exposure to persistent air pollutants such as nitrated polycyclic aromatic hydrocarbons (nitro-PAHs). 1-Nitropyrene (1-NP), one of the most abundant nitro-PAHs in diesel exhausts, was selected as a model nitro-PAH for the present study. The aim of the study was to investigate the effects of 1-NP in human umbilical vein endothelial cells (HUVECs) and the metabolic pathways involved. The nitroreductase inhibitor dicoumarol and the coplanar aryl hydrocarbon receptor (AhR) ligand PCB 126 were used to modulate the metabolism of 1-NP. The results revealed that low levels (< or =10microM) of 1-NP induced DNA damage, increased levels of reactive oxygen species (ROS) and increased protein expression of the endoplasmic reticulum (ER) stress chaperone GRP78. A decrease in cell viability was only observed following exposure to a higher level of 1-NP (15microM). Inhibition of nitroreductive metabolism by dicoumarol attenuated the induction of DNA damage, intracellular ROS levels and GRP78 expression. This suggests that the effects of 1-NP on HUVEC were mediated by metabolites mainly formed at nitroreduction. Our findings suggest that the human blood vessel endothelium is a sensitive target tissue for the major nitro-PAH constituent in diesel exhaust.
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| 46. |
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| 47. |
- Andersson, Maria A., et al.
(författare)
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Evaluation of the potential genotoxicity of chromium picolinate in mammalian cells in vivo and in vitro
- 2007
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Ingår i: Food and Chemical Toxicology. - : Elsevier BV. - 0278-6915 .- 1873-6351. ; 45:7, s. 1097-1106
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Tidskriftsartikel (refereegranskat)abstract
- Chromium picolinate (CrPic) is a synthetic nutritional supplement primarily used for weight loss and muscle building. Recent studies have indicated that CrPic might be genotoxic and these findings together with the wide-spread consumer use, have increased the concern about its safety. In the present study we investigated the potential genotoxicity of CrPic in mice given a single intraperitoneal injection (up to 3 mg/kg b.wt.) by evaluating the frequency of micronucleated polychromatic erythrocytes (fMNPCE) in peripheral blood, and DNA damage in lymphocytes and hepatocytes. The fMNPCE was evaluated after 42 h and DNA damage after 16 h. Using the Comet assay DNA damage was also monitored in extended-term cultures of human lymphocytes and in L5178Y mouse lymphoma cells that had been exposed for 3 h to 500 μM CrPic under different exposure conditions.A slight, but significant CrPic-induced increase in DNA damage (P < 0.001) was observed in the human lymphocytes, but only when these cells were exposed in the absence of serum. In all other experiments CrPic was found to be without genotoxic effects, both in vivo and in vitro. Taken together, our results suggest that a high concentration of CrPic might be DNA damaging, but only under non-physiological conditions.
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| 48. |
- Andersson, Maria, 1976-
(författare)
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Chemically Induced DNA Damage in Extended-term Cultures of Human Lymphocytes
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Generation of DNA damage is regarded to be an important initial event in the development cancer. Consequently, a battery of tests have been developed to detect different types of genotoxic effects in order to be able to predict the potential genotoxicity and mutagenicity of chemicals, including both pharmaceutical drugs and various types of environmental and occupational agents, as well as dietary factors. The aim of this thesis was to evaluate whether the combination of the comet assay and the extended-term cultures of human lymphocytes (ETC) can be used as an alternative in vitro system to more commonly used transformed mammalian cell lines, and primary cell cultures from humans, when testing the potential genotoxicity of chemicals. Using the comet assay, a panel of reference compounds showed that the ETC were found to detect the DNA-damaging effects with no remarkable difference to what has been reported in other cell types. Moreover, in comparison with a well-established rodent cell line, the mouse lymphoma L5178Y cells, the ETC showed similar sensitivity to the DNA damaging effects of the genotoxic agents hydrogen peroxide and catechol. Although there was an interindividual variation in induced DNA damage and the subsequent repair when using ETC from different blood donors, it did not seem to be of crucial importance for the identification of DNA-damaging agents. The demonstrated difference in sensitivity to catechol-induced DNA damage between freshly isolated peripheral lymphocytes and ETC may very well be due to their different proliferative status but despite this difference, both in vitro systems were able to identify catechol as a DNA-damaging agent at the same concentration.Based on these results, it is proposed that the ETC and the comet assay are a useful combination when testing for the potential DNA damaging effects of chemicals. Representing easily cultivated cells possessing the normal human karyotype, where one blood sample can be used for numerous experiments performed over a long time, extended-term cultures appear to be a useful alternative, both to transformed mammalian cell lines, and primary cell cultures from humans. In fact, the extended-term lymphocytes, with or without S9 and/or lesion specific DNA repair enzymes, should be used more frequently when screening for the potential genotoxicity of chemicals.
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| 49. |
- Andersson, Maria, et al.
(författare)
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Evaluation of catechol-induced DNA damage in human lymphocytes : A comparison between freshly isolated lymphocytes and T-lymphocytes from extended-term cultures
- 2007
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Ingår i: Toxicology in Vitro. - : Elsevier BV. - 0887-2333 .- 1879-3177. ; 21:4, s. 716-722
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Tidskriftsartikel (refereegranskat)abstract
- Extended-term cultures of proliferating human T-lymphocytes (ETC) may be a practical alternative to freshly isolated non-proliferating peripheral blood lymphocytes (PBL) when studying genotoxicity in vitro. To investigate if the pattern of DNA damage differs between the two in vitro systems, catechol-induced DNA damage was evaluated in PBL and ETC derived from the same blood sample, using three different donors. DNA damage was monitored using the comet assay. Whereas 3 h of exposure to 0.5 mM catechol was found to be without DNA damaging effects, 3 mM was found to induce significant damage both in the PBL and the ETC (the latter being clearly less sensitive). The level of reactive oxygen species (ROS) was also measured in the ETC using the fluorescent probe carboxy-H2DCFA. ROS was found to be considerably increased both at 0.5 and 3 mM catechol. The demonstrated difference in sensitivity towards catechol-induced DNA damage between PBL and ETC may be due to their different proliferative status, but despite this difference both in vitro systems were able to identify catechol as a DNA damaging agent at the same concentration.
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| 50. |
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