| 1. |
- Aamodt, K., et al.
(författare)
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The ALICE experiment at the CERN LHC
- 2008
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 3:S08002
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Forskningsöversikt (refereegranskat)abstract
- ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries, Its overall dimensions are 16 x 16 x 26 m(3) with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.
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| 2. |
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| 3. |
- Abate, E., et al.
(författare)
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Combined performance tests before installation of the ATLAS Semiconductor and Transition Radiation Tracking Detectors
- 2008
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- The ATLAS (A Toroidal LHC ApparatuS) Inner Detector provides charged particle tracking in the centre of the ATLAS experiment at the Large Hadron Collider (LHC). The Inner Detector consists of three subdetectors: the Pixel Detector, the Semiconductor Tracker (SCT), and the Transition Radiation Tracker (TRT). This paper summarizes the tests that were carried out at the final stage of SCT+TRT integration prior to their installation in ATLAS. The combined operation and performance of the SCT and TRT barrel and endcap detectors was investigated through a series of noise tests, and by recording the tracks of cosmic rays. This was a crucial test of hardware and software of the combined tracker detector systems. The results of noise and cross-talk tests on the SCT and TRT in their final assembled configuration, using final readout and supply hardware and software, are reported. The reconstruction and analysis of the recorded cosmic tracks allowed testing of the offline analysis chain and verification of basic tracker performance parameters, such as efficiency and spatial resolution, in combined operation before installation.
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| 4. |
- Abdesselam, A., et al.
(författare)
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Engineering for the ATLAS SemiConductor Tracker (SCT) end-cap
- 2008
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 3
-
Tidskriftsartikel (refereegranskat)abstract
- The ATLAS SemiConductor Tracker (SCT) is a silicon-strip tracking detector which forms part of the ATLAS inner detector. The SCT is designed to track charged particles produced in proton-proton collisions at the Large Hadron Collider (LHC) at CERN at an energy of 14 TeV. The tracker is made up of a central barrel and two identical end-caps. The barrel contains 2112 silicon modules, while each end-cap contains 988 modules. The overall tracking performance depends not only on the intrinsic measurement precision of the modules but also on the characteristics of the whole assembly, in particular, the stability and the total material budget. This paper describes the engineering design and construction of the SCT end-caps, which are required to support mechanically the silicon modules, supply services to them and provide a suitable environment within the inner detector. Critical engineering choices are highlighted and innovative solutions are presented - these will be of interest to other builders of large-scale tracking detectors. The SCT end-caps will be fully connected at the start of 2008. Further commissioning will continue, to be ready for proton-proton collision data in 2008.
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| 5. |
- Abdesselam, A., et al.
(författare)
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The ATLAS semiconductor tracker end-cap module
- 2007
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 575:3, s. 353-389
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Tidskriftsartikel (refereegranskat)abstract
- The challenges for the tracking detector systems at the LHC are unprecedented in terms of the number of channels, the required read-out speed and the expected radiation levels. The ATLAS Semiconductor Tracker. (SCT) end-caps have a total of about 3 million electronics channels each reading out every 25 ns into its own on-chip 3.3 mu s buffer. The highest anticipated dose after 10 years operation is 1.4x10(14) cm(-2) in units of 1 MeV neutron equivalent (assuming the damage factors scale with the non-ionising energy loss). The forward tracker has 1976 double-sided modules, mostly of area similar to 70 cm(2), each having 2 x 768 strips read out by six ASICs per side. The requirement to achieve an average perpendicular radiation length of 1.5% X-0, while coping with up to 7 W dissipation per module (after irradiation), leads to stringent constraints on the thermal design. The additional requirement of 1500e(-) equivalent noise charge (ENC) rising to only 1800e(-) ENC after irradiation, provides stringent design constraints on both the high-density Cu/Polyimide flex read-out circuit and the ABCD3TA read-out ASICs. Finally, the accuracy of module assembly must not compromise the 16 mu m (r phi) resolution perpendicular to the strip directions or 580 mu m radial resolution coming from the 40 mrad front-back stereo angle. A total of 2210 modules were built to the tight tolerances and specifications required for the SCT. This was 234 more than the 1976 required and represents a yield of 93%. The component flow was at times tight, but the module production rate of 40-50 per week was maintained despite this. The distributed production was not found to be a major logistical problem and it allowed additional flexibility to take advantage of where the effort was available, including any spare capacity, for building the end-cap modules. The collaboration that produced the ATLAS SCT end-cap modules kept in close contact at all times so that the effects of shortages or stoppages at different sites could be rapidly resolved.
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| 6. |
- Abdesselam, A., et al.
(författare)
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The barrel modules of the ATLAS semiconductor tracker
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 568:2, s. 642-671
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the silicon microstrip modules in the barrel section of the SemiConductor Tracker (SCT) of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The module requirements, components and assembly techniques are given, as well as first results of the module performance on the fully assembled barrels that make up the detector being installed in the ATLAS experiment.
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| 7. |
- Coustenis, A., et al.
(författare)
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TandEM : Titan and Enceladus mission
- 2009
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Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:3, s. 893-946
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Tidskriftsartikel (refereegranskat)abstract
- TandEM was proposed as an L-class (large) mission in response to ESA's Cosmic Vision 2015-2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini-Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (MontgolfiSre) and possibly several landing probes to be delivered through the atmosphere.
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| 8. |
- Niedermaier, O., et al.
(författare)
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"Safe" Coulomb excitation of Mg-30
- 2005
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 94:17, s. 172501 (artno)-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient γ spectrometer MINIBALL. Using Mg-30 ions accelerated to an energy of 2.25 MeV/u together with a thin Ni-nat target, Coulomb excitation of the first excited 2(+) states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation γ-ray yields the B(E2;0(gs)(+)→ 2(1)(+)) value of Mg-30 was determined to be 241(31)e(2) fm(4). Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope Mg-30 resides outside the "island of inversion."
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| 9. |
- Niedermaier, O., et al.
(författare)
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The neutron-rich Mg isotopes: first results from MINIBALL at REX-ISOLDE
- 2005
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 752, s. 273-273
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient γ spectrometer MINIBALL. Using Mg-30 ions accelerated to an energy of 2.25 MeV/u together with a thin Ni-nat target, Coulomb excitation of the first excited 2(+) states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation γ-ray yields the B(E2;0(gs)(+)→ 2(1)(+)) value of Mg-30 was determined to be 241(31)e(2) fm(4). Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope Mg-30 resides outside the "island of inversion."
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| 10. |
- Scheit, H., et al.
(författare)
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Coulomb excitation of neutron-rich beams at REX-ISOLDE
- 2005
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 25:Suppl. 1, s. 397-402
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Konferensbidrag (refereegranskat)abstract
- After the successful commissioning of the radioactive beam experiment at ISOLDE (REX-ISOLDE) - an accelerator for exotic nuclei produced by ISOLDE - in 2002 and the promotion to a CERN user facility in 2003, first physics experiments using these beams were performed. Initial experiments focused on the region of deformation in the vicinity of the neutron-rich Na and Mg isotopes. Preliminary results on the neutron-rich Na and Mg isotopes show the high potential and physics opportunities offered by the exotic isotope accelerator REX in conjunction with the modern Germanium gamma spectrometer MINIBALL.
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| 11. |
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| 12. |
- Laj, P., et al.
(författare)
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Measuring Atmospheric Composition Change
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1873-2844 .- 1352-2310. ; 43:33, s. 5351-5414
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Tidskriftsartikel (refereegranskat)abstract
- Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in-situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements. In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions.
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| 13. |
- Jeppesen, H. B., et al.
(författare)
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Investigation of the Li-9+H-2 -> Li-8+t reaction at REX-ISOLDE
- 2006
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 635, s. 17-17
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Tidskriftsartikel (refereegranskat)abstract
- The one-neutron transfer reaction Li-9 + H-2 -> Li-8 + t has been investigated in an inverse kinematics experiment by bombarding a deuterated polypropylene target with a 2.36 MeV/u Li-9 beam from the post-accelerator REX-ISOLDE at CERN. Excitation energies in Li-8 as well as angular distributions of the tritons were obtained and spectroscopic factors deduced. (c) 2006 Elsevier B.V. All rights reserved.
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| 14. |
- Smith, A., et al.
(författare)
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LunarEX-a proposal to cosmic vision
- 2009
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:3, s. 711-740
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Tidskriftsartikel (refereegranskat)
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| 15. |
- Jeppesen, H. B., et al.
(författare)
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Low energy reactions with radioactive ions at REX-ISOLDE - the Li-9+H-2 case
- 2005
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 748, s. 374-374
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Tidskriftsartikel (refereegranskat)abstract
- At the newly constructed postaccelerator REX-ISOLDE (Radioactive beam Experiment at ISOLDE) we have investigated reactions induced by a Li-9 beam incident on a deuterium target at an energy of 2.36 MeV/u. Most reaction channels were recorded. From one-neutron transfer the differential cross-section for the low lying Li-10 spectrum is found. The results from the other channels demonstrate the great applicability and many possibilities that REX-ISOLDE opens up.
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| 16. |
- Aksyutina, Yu, et al.
(författare)
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Lithium isotopes beyond the drip line
- 2008
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 666:5, s. 430-434
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Tidskriftsartikel (refereegranskat)abstract
- The unbound isotopes 10Li, 12Li and 13Li have been observed after nucleon-knockout reactions at relativistic energies with 11Li and 14Be beams impinging on a liquid hydrogen target. The channels , and were analysed in the ALADIN-LAND setup at GSI. The 10Li data confirm earlier findings, while the 12Li and 13Li nuclei were observed for the first time. The relative-energy spectrum shows that the ground state of 12Li can be described as a virtual s-state with a scattering length of -13.7(1.6) fm. A broad energy spectrum was found for the channel. Based on the assumption that the relative-energy spectrum is dominated by a correlated background presumably stemming from initial correlations in the 14Be ground-state, evidence for a 13Li resonance at 1.47(31) MeV above the threshold with a width around 2 MeV has been found.
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| 17. |
- Chulkov, L. V., et al.
(författare)
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Three-body correlations in electromagnetic dissociation of Borromean nuclei: The He-6 case
- 2005
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 759:1-2, s. 23-42
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Tidskriftsartikel (refereegranskat)abstract
- Dissociation of He-6 on a lead target has been studied at 240 MeV/u. The four-momenta of the two neutrons in coincidence with alpha-particles have been measured and used to reconstruct the three-body energy and angular correlations in the final state. For the first time, three-body correlations were included in the analysis of the He-6 dissociation data, and compared with calculations assuming a dipole mode for the electromagnetic dissociation. In addition, the experimental data have been analyzed using a series expansion of the final transition amplitude into hyperspherical functions, showing the importance of both nn and alpha n final-state interactions. It is shown that the dissociation process is governed by a transition of one neutron from the p-shell in the 6He ground state to the s-shell in the continuum further indicating that the role of the transition through an intermediate He-5(3/2(-)) state is more important than expected. (c) 2005 Elsevier B.V. All rights reserved.
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| 18. |
- Carr, C., et al.
(författare)
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RPC : The rosetta plasma consortium
- 2007
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Ingår i: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 128:1-4, s. 629-647
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Forskningsöversikt (refereegranskat)abstract
- The Rosetta Plasma Consortium (RPC) will make in-situ measurements of the plasma enviromnent of comet 67P/Churyumov-Gerasimenko. The consortium will provide the complementary data sets necessary for an understanding of the plasma processes in the inner coma, and the structure and evolution of the coma with the increasing cometary activity. Five sensors have been selected to achieve this: the Ion and Electron Sensor (IES), the Ion Composition Analyser (ICA), the Langmuir Probe (LAP), the Mutual Impedance Probe (MIP) and the Magnetometer (MAG). The sensors interface to the spacecraft through the Plasma Interface Unit (PIU). The consortium approach allows for scientific, technical and operational coordination, and makes Optimum use of the available mass and power resources.
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| 19. |
- Edberg, Niklas J. T., et al.
(författare)
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Simultaneous measurements of Martian plasma boundaries by Rosetta and Mars Express
- 2009
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Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 57:8-9, s. 1085-1096
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Tidskriftsartikel (refereegranskat)abstract
- We present the first two-spacecraft near-simultaneous observations of the Martian bow shock (BS), magnetic pileup boundary (MPB) and photo-electron boundary (PEB) obtained by the plasma instruments onboard Rosetta and Mars Express during the Rosetta Mars fly by on February 25, 2007. Our observations are compared with shape models for the BS and MPB derived from previous statistical studies. The MPB is found at its expected position but the BS for this event is found significantly closer to the planet than expected for the rather slow and moderately dense solar wind. Cross-calibration of the density measurements on the two spacecraft gives a density profile through the magnetosheath, indicating an increasing solar wind flux during the Rosetta passage which is consistent with the multiple BS crossings at the Rosetta exit.
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| 20. |
- Edberg, Niklas, et al.
(författare)
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Rosetta and Mars Express observations of the influence of high solar wind pressure on the Martian plasma environment
- 2009
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 27:12, s. 4533-4545
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Tidskriftsartikel (refereegranskat)abstract
- We report on new simultaneous in-situ observations at Mars from Rosetta and Mars Express (MEX) on how the Martian plasma environment is affected by high pressure solar wind. A significant sharp increase in solar wind density, magnetic field strength and turbulence followed by a gradual increase in solar wind velocity is observed during similar to 24 h in the combined data set from both spacecraft after Rosetta's closest approach to Mars on 25 February 2007. The bow shock and magnetic pileup boundary are coincidently observed by MEX to become asymmetric in their shapes. The fortunate orbit of MEX at this time allows a study of the inbound boundary crossings on one side of the planet and the outbound crossings on almost the opposite side, both very close to the terminator plane. The solar wind and interplanetary magnetic field (IMF) downstream of Mars are monitored through simultaneous measurements provided by Rosetta. Possible explanations for the asymmetries are discussed, such as crustal magnetic fields and IMF direction. In the same interval, during the high solar wind pressure pulse, MEX observations show an increased amount of escaping planetary ions from the polar region of Mars. We link the high pressure solar wind with the observed simultaneous ion outflow and discuss how the pressure pulse could also be associated with the observed boundary shape asymmetry.
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| 21. |
- Jeppesen, H. B., et al.
(författare)
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Study of Li-10 via the Li-9(H-2, p) reaction at REX-ISOLDE
- 2006
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 642:5-6, s. 449-454
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Tidskriftsartikel (refereegranskat)abstract
- The Click to view the MathML source reaction has been investigated at 2.36 MeV/u at the REX-ISOLDE facility. In this Letter we focus on the Click to view the MathML source channel which potentially holds spectroscopic information on the unbound nucleus 10Li. The experimental excitation energy spectrum and angular distribution are compared with CCBA calculations. These calculations clearly support the existence of a low-lying (s) virtual state, with a (negative) scattering length of the order asnot, vert, similar1324 fm and a p1/2 resonance with an energy of Ersimilar, equals0.38 MeV and a width of Γsimilar, equals0.2 MeV.
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| 22. |
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| 23. |
- Simon, H., et al.
(författare)
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Systematic investigation of the drip-line nuclei 11Li and 14Be and their unbound subsystems 10Li and 13Be
- 2007
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 791:3-4, s. 267-
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Tidskriftsartikel (refereegranskat)abstract
- Fragmentation reactions in a carbon target with beams of 11Li and 14Be at relativistic energies have been studied in a kinematically complete experiment at the ALADIN-LAND setup at GSI. Excited states in 11Li and 14Be were obtained from the data in the inelastic channel. The measured cross sections with the core nucleus in the final state show that in the 14Be case core polarization plays an important role. In the one-neutron knockout channels the measured angular correlations between fragment and neutron are asymmetric, which demonstrates the presence of states with different parities in the 11Li and 14Be ground states. For 10Li a low-lying virtual s-state, a p-state and evidence for a d-state could be extracted from the data, while the 12Be+n system shows resonances with more complicated structure.
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| 24. |
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| 25. |
- Adewumi, Oluseun, et al.
(författare)
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Characterization of human embryonic stem cell lines by the International Stem Cell Initiative
- 2007
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Ingår i: Nature Biotechnology. - : Springer Science and Business Media LLC. - 1087-0156 .- 1546-1696. ; 25:7, s. 803-816
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Tidskriftsartikel (refereegranskat)abstract
- The International Stem Cell Initiative characterized 59 human embryonic stem cell lines from 17 laboratories worldwide. Despite diverse genotypes and different techniques used for derivation and maintenance, all lines exhibited similar expression patterns for several markers of human embryonic stem cells. They expressed the glycolipid antigens SSEA3 and SSEA4, the keratan sulfate antigens TRA-1-60, TRA-1-81, GCTM2 and GCT343, and the protein antigens CD9, Thy1 (also known as CD90), tissue- nonspecific alkaline phosphatase and class 1 HLA, as well as the strongly developmentally regulated genes NANOG, POU5F1 (formerly known as OCT4), TDGF1, DNMT3B, GABRB3 and GDF3. Nevertheless, the lines were not identical: differences in expression of several lineage markers were evident, and several imprinted genes showed generally similar allele-specific expression patterns, but some gene-dependent variation was observed. Also, some female lines expressed readily detectable levels of XIST whereas others did not. No significant contamination of the lines with mycoplasma, bacteria or cytopathic viruses was detected.
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| 26. |
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| 27. |
- Karlsson, P. G., et al.
(författare)
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Metal organic chemical vapor deposition of ultrathin ZrO2 films on Si(1 0 0) and Si(1 1 1) studied by electron spectroscopy
- 2007
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 601:4, s. 1008-1018
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Tidskriftsartikel (refereegranskat)abstract
- The growth of ultrathin ZrO2 films on Si(100)-(2x1) and Si(111)-(7x7) has been studied with core level photoelectron spectroscopy and X-ray absorption spectroscopy. The films were deposited sequentially by chemical vapor deposition in ultra-high vacuum using zirconium tetra-tert-butoxide as precursor. Deposition of a > 50Å thick film leads in both cases to tetragonal ZrO2 (t-ZrO2), whereas significant differences are found for thinner films. On Si(111)-(7x7) the local structure of t-ZrO2 is not observed until a film thickness of 51Å is reached. On Si(100)-(2x1) the local geometric structure of t-ZrO2 is formed already at a film thickness of 11Å. The higher tendency for the formation of t-ZrO2 on Si(100) is discussed in terms of Zr–O valence electron matching to the number of dangling bonds per surface Si atom. The Zr–O hybridization within the ZrO2 unit depends furthermore on the chemical composition of the surrounding. The precursor t-butoxy ligands undergo efficient C–O scission on Si(100), leaving carbonaceous fragments embedded in the interfacial layer. In contrast, after small deposits on Si(111) stable t-butoxy groups are found. These are consumed upon further deposition. Stable methyl and, possibly, also hydroxyl groups are found on both surfaces within a wide film thickness range.
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| 28. |
- Karlsson, P.G., et al.
(författare)
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Ultrathin ZrO2 films on Si-rich SiC(0 0 0 1)-(3 × 3) : Growth and thermal stability
- 2007
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 601:11, s. 2390-2400
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Tidskriftsartikel (refereegranskat)abstract
- The growth and thermal stability of ultrathin ZrO2 films on the Si-rich SiC(0 0 0 1)-(3 × 3) surface have been explored using photoelectron spectroscopy (PES) and X-ray absorption spectroscopy (XAS). The films were grown in situ by chemical vapor deposition using the zirconium tetra tert-butoxide (ZTB) precursor. The O 1s XAS results show that growth at 400 °C yields tetragonal ZrO2. An interface is formed between the ZrO2 film and the SiC substrate. The interface contains Si in several chemically different states. This gives evidence for an interface that is much more complex than that formed upon oxidation with O2. Si in a 4+ oxidation state is detected in the near surface region. This shows that intermixing of SiO2 and ZrO2 occurs, possibly under the formation of silicate. The alignment of the ZrO2 and SiC band edges is discussed based on core level and valence PES spectra. Subsequent annealing of a deposited film was performed in order to study the thermal stability of the system. Annealing to 800 °C does not lead to decomposition of the tetragonal ZrO2 (t-ZrO2) but changes are observed within the interface region. After annealing to 1000 °C a laterally heterogeneous layer has formed. The decomposition of the film leads to regions with t-ZrO2 remnants, metallic Zr silicide and Si aggregates. © 2007 Elsevier B.V. All rights reserved.
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| 29. |
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| 30. |
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| 31. |
- Richter, H. O, et al.
(författare)
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Neuroanatomical correlates of voluntary inhibition of accommodation/vergence under monocular open-loop viewing conditions.
- 2005
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 21:11, s. 3077-3088
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this work is to identify human neural circuits involved in inhibition of accommodation/vergence by contrasting the cortical functions subservient to negative voluntary accommodation/vergence (NVA) with those evoked by active fixation in darkness (FIX). Five subjects with normal corrected acuity were studied using positron emission tomography and the H O bolus technique. The dominant right eye viewed a laser speckle pattern (633 nm) whose direction and velocity of motion were determined by the refractive state of the eye. The speckle pattern was presented at a distance of 1.8 m (0.55 D). The non-dominant eye was patched. Subjects performed two tasks counterbalanced for order effects: (i) attempted fixation on the remembered target in darkness with the dominant eye open and ‘fixating’; and (ii) voluntary reduction of the laser speckle flow during each alternate 20-s epoch when a convex +2.0 D lens was placed in front of the right eye causing the speckle pattern to move downwards at 3 °/s. Comparison of the condition of NVA with the condition of FIX indicated widespread occipital activation. Decreases in absolute regional cerebral blood flow occurred in the superior parietal cortex (BA 5), frontal cortex (BA 8 and 10) and within the postcentral/precentral gyrus (BA 1/2/3/4) bilaterally where deactivation clusters eclipsed the presumed neck and shoulder areas. Negative accommodation/vergence appears to be driven by a reduction of parasympathetic tone, and has the effect of shutting down brain regions known to be involved in regulating visual search as well as a centrally controlled eye–head–neck–shoulder motor programme responsible for posturing gaze.
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| 32. |
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| 33. |
- Richter, J H, et al.
(författare)
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Electronic structure of lithium-doped anatase TiO2 prepared in ultrahigh vacuum
- 2005
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 71:23, s. 1-235418
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Tidskriftsartikel (refereegranskat)abstract
- Insertion of lithium in anatase TiO2, giving LixTiO2, is performed under ultrahigh vacuum (UHV) conditions and studied using synchrotron radiation based electron spectroscopy. Core level photoemission spectra are directly compared to results obtained after electrochemical insertion, illustrating the usefulness of the UHV approach. The growth of a state of mainly Ti 3d character in the band gap is monitored and the amount of charge transferred from Li to the band gap state is quantified. The result that the Ti 3d level is occupied by 0.85 +/- 0.10 electronic charge is in good agreement with theoretical predictions. Binding energy shifts of the core levels suggest that the population of the Ti 3d states does not follow a simple rigid band behavior. It is concluded that the formation of the Li-poor phase (x < 2%) is associated with pinning of the Fermi level to the bottom of the conduction band. The Li-poor phase can therefore be envisaged as related to defects. Changes in the valence photoemission spectrum and O 1s x-ray absorption spectrum are interpreted in terms of a decreased O 2p-Ti 3d interaction upon Li insertion. Shifts in the sample work function are finally found to agree reasonably well with the measured cell voltage for electrochemical Li insertion into a nanoporous anatase film.
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| 34. |
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| 35. |
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| 36. |
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| 37. |
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| 38. |
- Dutt, Amit, et al.
(författare)
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Drug-sensitive FGFR2 mutations in endometrial carcinoma
- 2008
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 105:25, s. 8713-8717
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Tidskriftsartikel (refereegranskat)abstract
- Oncogenic activation of tyrosine kinases is a common mechanism of carcinogenesis and, given the druggable nature of these enzymes, an attractive target for anticancer therapy. Here, we show that somatic mutations of the fibroblast growth factor receptor 2 (FGFR2) tyrosine kinase gene, FGFR2, are present in 12% of endometrial carcinomas, with additional instances found in lung squamous cell carcinoma and cervical carcinoma. These FGFR2 mutations, many of which are identical to mutations associated with congenital craniofacial developmental disorders, are constitutively activated and oncogenic when ectopically expressed in NIH 3T3 cells. Inhibition of FGFR2 kinase activity in endometrial carcinoma cell lines bearing such FGFR2 mutations inhibits transformation and survival, implicating FGFR2 as a novel therapeutic target in endometrial carcinoma.
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| 39. |
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| 40. |
- Grehk, Mikael, et al.
(författare)
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Initial stages of metal-organic chemical-vapor deposition of ZrO2 on a FeCrAl alloy
- 2008
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Ingår i: Thin Solid Films. - Amsterdam : Elsevier BV. - 0040-6090 .- 1879-2731. ; 516:6, s. 875-879
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Tidskriftsartikel (refereegranskat)abstract
- The initial stages of metal-organic chemical-vapor deposition of ZrO2 on a model FeCrAl alloy was investigated using synchrotron radiation photoelectron spectroscopy, X-ray absorption spectroscopy, scanning Auger microprobe, and time of flight secondary mass spectrometry. The coatings were grown in ultra-high vacuum at 400 degrees C and 800 degrees C using the single source precursor zirconium tetra-tert-butoxide. At 400 degrees C the coatings mainly consist of tetragonal ZrO2 and at 800 degrees C a mixed ZrO2/Al2O3 layer is formed. The Al metal diffuses from the FeCrAl bulk to the metal/coating interface at 400 degrees C and to the surface of the coating at 800 degrees C. The result indicates that the reaction mechanism of the growth process is different at the two investigated temperatures.
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| 41. |
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| 42. |
- Karlsson, P. G., et al.
(författare)
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Initial stages of ZrO2 chemical vapor deposition on Si(100)-(2x1) from zirconium tetra-tert-butoxide
- 2008
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 602:10, s. 1803-1809
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Tidskriftsartikel (refereegranskat)abstract
- The initial stages of chemical vapor deposition of ZrO2 from zirconium tetra-tert-butoxide (ZTB) on Si(100)-(2 x 1) have been studied by scanning tunnelling microscopy (STM) and synchrotron radiation excited photoelectron spectroscopy (PES). The STM images and core level (PES) spectra indicate that the predominant surface modifications induced by ZTB are due to silicon carbonization and formation of zirconium dioxide. The carbonization reaction leads to formation of subsurface carbon and two types of reconstructions are discussed: dimer vacancies and dimer vacancies in conjunction with a rotated surface Si-dimer. Indications for the formation of small amounts of zirconium silicide are also found. No evidence for silicon oxidation can be observed with PES, in contrast to the interface properties previously found after larger exposures to ZTB.
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| 43. |
- Karlsson, P. G., et al.
(författare)
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Metal organic chemical vapor deposition of ultrathin ZrO2 films on Si(100) and Si(111) studied by electron spectroscopy
- 2007
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 601:4, s. 1008-1018
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Tidskriftsartikel (refereegranskat)abstract
- The growth of ultrathin ZrO2 films on Si(100)-(2 x 1) and Si(111)-(7 x 7) has been studied with core level photoelectron spectroscopy and X-ray absorption spectroscopy. The films were deposited sequentially by chemical vapor deposition in ultra-high vacuum using zirconium tetra-tert-butoxide as precursor. Deposition of a > 50 angstrom thick film leads in both cases to tetragonal ZrO2 (t-ZrO2), whereas significant differences are found for thinner films. On Si(111)-(7 x 7) the local structure of t-ZrO2 is not observed until a film thickness of 51 angstrom is reached. On Si(100)-(2 x 1) the local geometric structure of t-ZrO2 is formed already at a film thickness of 11 angstrom. The higher tendency for the formation of t-ZrO2 on Si(100) is discussed in terms of Zr-O valence electron matching to the number of dangling bonds per surface Si atom, The Zr-O hybridization within the ZrO2 unit depends furthermore on the chemical composition of the surrounding. The precursor t-butoxy ligands undergo efficient C-O scission on Si(100), leaving carbonaceous fragments embedded in the interfacial layer. In contrast, after small deposits on Si(111) stable t-butoxy groups are found. These are consumed upon further deposition. Stable methyl and, possibly, also hydroxyl groups are found on both surfaces within a wide film thickness range. (c) 2006 Elsevier B.V. All rights reserved.
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| 44. |
- Karlsson, P. G., et al.
(författare)
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Ultrathin ZrO2 films on Si-rich SiC(0001)-(3x3): Growth and thermal stability
- 2007
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 601:11, s. 2390-2400
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Tidskriftsartikel (refereegranskat)abstract
- The growth and thermal stability of ultrathin ZrO2 films on the Si-rich Si(0001)-(3 x 3) surface have been explored using photoelectron spectroscopy (PES) and X-ray absorption spectroscopy (XAS). The films were grown in situ by chemical vapor deposition using the zirconium tetra tert-butoxide (ZTB) precursor. The O 1s XAS results show that growth at 400 degrees C yields tetragonal ZrO2. An interface is formed between the ZrO2 film and the SiC substrate. The interface contains Si in several chemically different states. This gives evidence for an interface that is much more complex than that formed upon oxidation with O-2. Si in a 4+ oxidation state is detected in the near surface region. This shows that intermixing of SiO2 and ZrO2 occurs, possibly under the formation of silicate. The alignment of the ZrO2 and SiC band edges is discussed based on core level and valence PES spectra. Subsequent annealing of a deposited film was performed in order to study the thermal stability of the system. Annealing to 800 degrees C does not lead to decomposition of the tetragonal ZrO2 (t-ZrO2) but changes are observed within the interface region. After annealing to 1000 degrees C a laterally heterogeneous layer has formed. The decomposition of the film leads to regions with t-ZrO2 remnants, metallic Zr silicide and Si aggregates. (c) 2007 Elsevier B.V. All rights reserved.
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| 45. |
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| 46. |
- Richter, J., et al.
(författare)
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An Iranian (Farsi) version of the temperament and character inventory : A cross-cultural comparison
- 2007
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Ingår i: Psychological Reports. - 0033-2941 .- 1558-691X. ; 100:3 II, s. 1218-1228
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Tidskriftsartikel (refereegranskat)abstract
- The Temperament and Character Inventory is a widely used personality questionnaire. It was developed to measure the four temperament dimensions of Novelty Seeking, Harm Avoidance, Reward Dependence, and Persistence, as well as three character dimensions, such as Self-directedness, Cooperativeness, and Self-transcendence, described in Cloninger's unified biosocial theory of personality. In a sample of 300 Germans, 300 Swedes, and 316 Iranian subjects, a factorial structure analysis using the Procrustes rotation method showed the structure of personality to be generally equivalent across cultures. Noteworthy cultural differences between the overall Asian and European subjects reflected by the data were observed in various Temperament and Character dimensions. Seemingly, there are cultural differences in the expression of the various personality facets that require a replacement of many items in the Iranian version. The Temperament and Character Inventory is sensitive to age, sex, and cultural differences in personality. © Psychological Reports 2007.
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| 47. |
- Richter, J. H., et al.
(författare)
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Electronic structure of a laterally graded ZrO2-TiO2 film on Si(100) prepared by metal-organic chemical vapor deposition in ultrahigh vacuum
- 2008
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 103:9, s. 094109-094109-8
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Tidskriftsartikel (refereegranskat)abstract
- A TiO2-ZrO2 film with laterally graded stoichiometry has been prepared by metal-organic chemical vapor deposition in ultrahigh vacuum. The film was characterized in situ using synchrotron radiation photoelectron spectroscopy (PES) and x-ray absorption spectroscopy. PES depth profiling clearly shows that Ti ions segregate toward the surface region when mixed with ZrO2. The binding energy of the ZrO2 electronic levels is constant with respect to the local vacuum level. The binding energy of the TiO2 electronic levels is aligned to the Fermi level down to a Ti/Zr ratio of about 0.5. At a Ti/Zr ratio between 0.1 and 0.5, the TiO2 related electronic levels become aligned to the local vacuum level. The addition of small amounts of TiO2 to ZrO2 results in a ZrO2 band alignment relative to the Fermi level that is less asymmetric than for pure ZrO2. The band edge positions shift by -0.6 eV for a Ti/Zr ratio of 0.03. This is explained in terms of an increase in the work function when adding TiO2, an effect that becomes emphasized by Ti surface segregation.
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| 48. |
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| 49. |
- Sandell, A., et al.
(författare)
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Probing and modifying the empty-state threshold of anatase TiO2 : Experiments and ab initio theory
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:7, s. 075113-
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Tidskriftsartikel (refereegranskat)abstract
- O 1s x-ray absorption spectroscopy (XAS) in conjunction with photoelectron spectroscopy has been used to explore the conduction-band edge of single crystalline and nanostructured anatase TiO2. The experiments are supported by ab initio density-functional calculations in which both the initial and core hole final states are considered. The calculations show that the states at the conduction-band edge of anatase are of pure d(xy) character. This is also the case in the presence of an O 1s core hole. In the O 1s XAS process pure Ti d states cannot be probed and, by appropriate energy referencing, the separation between the Ti d derived conduction-band edge and the threshold of the unoccupied Ti d-O p states can therefore be revealed. The electronic charge needed per Ti to eliminate this offset is discussed in quantitative terms. The theoretical and experimental values are in good agreement, showing that 4 +/- 2% of an electronic charge per Ti ion is sufficient to change the character of the empty states at threshold from pure Ti d to Ti d-O p.
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| 50. |
- Sandell, Anders, et al.
(författare)
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Surface chemistry of HfI4 on Si(100)-(2x1) studied by core level photoelectron spectroscopy
- 2007
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 601:4, s. 917-923
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Tidskriftsartikel (refereegranskat)abstract
- The chemistry of HfI4 adsorbed on the Si(100)-(2 x 1) surface has been studied by core level photoelectron spectroscopy in ultra-high vacuum. Two stable surface intermediates are identified: HfI3 and HfI2, both of which remain upon heating to 690 K. The dissociation of HfI4 is accompanied by the formation of SiI. In addition, HfI4 is observed up to 300 K. Complete desorption of iodine occurs in the temperature regime 690-780 K. Deposition of HfI4 at 870 K results in a layer consisting of metallic Hf, whereas deposition at 1120 K results in the formation of Hf silicide. The results indicate that the metallic Hf formed at 870 K is in the form of particles. Oxidation of this film by O2 at low pressure does not result in complete Hf oxidation. This suggests that complete oxidation of Hf is a critical step when using HfI4 as precursor in atomic layer deposition.
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