| 51. |
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| 52. |
- Markevich, V.P., et al.
(författare)
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Electronic properties of vacancy-oxygen complexes in SiGe alloys
- 2003
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 340, s. 790-4
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Tidskriftsartikel (refereegranskat)abstract
- Capacitance transient techniques, combined with ab initio modeling, were employed to study the electronic properties and structure of vacancy-oxygen (VO) complexes in unstrained Czochralski-grown Si1-xGex crystals (0
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| 53. |
- Markevich, V. P., et al.
(författare)
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Observation and theory of the V-O-H2 complex in silicon
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:19, s. 12964-12969
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of hydrogen with radiation-induced defects (RD's) in Czochralski-grown silicon crystals has been studied by infrared-absorption spectroscopy and ab initio modeling. Hydrogen and/or deuterium was introduced into the crystals by indiffusion from H2 (D2) gas at 1200-1300 °C. The samples were subsequently irradiated with fast electrons (E=2-4 MeV) and annealed in the temperature range of 100-600 °C. The centers produced by the irradiation were the same in both the untreated and treated cases, namely the A-center, Ci-Oi complex, and divacancy. A heat treatment of the H-treated samples resulted in the enhanced loss of these centers and the formation of centers containing hydrogen. The disappearance of the A centers in the temperature range of 100-150 °C is correlated with the appearance of three local vibrational modes (LVM's) at 943.5, 2126.4, and 2151.5 cm-1. The isotopic shifts of these lines were obtained from measurements on the samples doped with hydrogen and deuterium. The lines are identified as related to stretching vibrational modes of a complex that consists of one oxygen and two hydrogen atoms sharing a vacancy site (V-O-H2 complex). Ab initio calculations are used to explore the structures and properties of this defect. The origin of other LVM bands, which were observed upon annealing, is discussed.
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| 54. |
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| 55. |
- Murin, L.I., et al.
(författare)
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Isotopic effects on vibrational modes of thermal double donors in Si and Ge
- 2001
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Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 308-310, s. 290-293
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Tidskriftsartikel (refereegranskat)abstract
- The local vibrational modes of thermal double donors in Si and Ge are investigated by FTIR and ab initio modelling. At most, two oxygen modes are detected from each donor, which exhibit regular shifts with increasing donor number. By using mixtures of 16O and 18O, it is found that in Si the upper band does not yield any new modes suggesting that any oxygen atom is decoupled from any other. However, the lower frequency bands exhibit unique mixed modes proving for the first time that oxygen atoms are coupled together and in close spatial proximity. Ab initio calculations demonstrate that the modes and their isotopic shifts are consistent with a model involving two parallel chains of oxygen atoms linking second neighbour Si atoms, terminated by O-atoms close to the normal position for interstitial O. © 2001 Elsevier Science B.V. All rights reserved.
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| 56. |
- Noterdaeme, J. M., et al.
(författare)
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Heating, current drive and energetic particle studies on JET in preparation of ITER operation
- 2003
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 43:3, s. 202-209
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes the recent work on JET in the three areas of heating, current drive and energetic particles. The achievements have extended the possibilities of JET, have a direct connection to ITER operation and provide new and interesting physics. Toroidal rotation profiles of plasmas heated far off axis with little or no refuelling or momentum input are hollow with only small differences on whether the power deposition is located on the low field side or on the high field side. With LH current drive the magnetic shear was varied from slightly positive to negative. The improved coupling (through the use of plasma shaping and CD4) allowed up to 3.4 MW of PLH in internal transport barrier (ITB) plasmas with more than 15 MW of combined NBI and ICRF heating. The q-profile with negative magnetic shear and the ITB could be maintained for the duration of the high heating pulse (8 s). Fast ions have been produced in JET with ICRF to simulate alpha particles: by using third harmonic He-4 heating, beam injected He-4 at 120 kV were accelerated to energies above 2 MeV taking advantage of the unique capability of JET to use NBI with 4 He and to confine MeV class ions. ICRF heating was used to replicate the dynamics of alpha heating and the control of an equivalent Q = 10 `burn' was simulated.
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| 57. |
- Ohlson, CG, et al.
(författare)
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Stress markers in relation to job strain in human service organizations
- 2001
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Ingår i: Psychotherapy and psychosomatics. - : S. Karger AG. - 0033-3190 .- 1423-0348. ; 70:5, s. 268-275
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Tidskriftsartikel (refereegranskat)abstract
- <i>Background:</i> Workers in human service organizations are often confronted with conflicting demands in providing care or education. The aim of this cross-sectional study was to relate levels of endocrine stress markers to perceived job strain in two human service organizations. <i>Methods:</i> Employees in two local units of the social insurance organization and two local units of the individual and family care sections of the social welfare in Sweden were selected and 103 employees participated (56% participation rate). The perceived job strain was assessed with a standardized questionnaire containing questions of the demand-control model. Questions specially designed to measure emotional demands were also included. The stress markers cortisol, prolactin, thyroid-stimulating hormone, testosterone and IgA and IgG were analysed in blood samples. <i>Results:</i> The main finding was an association between high emotional strain and increased levels of prolactin. The levels of cortisol, but none of the other four stress markers, increased slightly with emotional strain. <i>Conclusions:</i> Emotional strain experienced in human service work may cause psychological stress. The increase in prolactin was modest but consistent with findings in other published studies on stress-related endocrine alterations.
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| 58. |
- Pellegrini, G., et al.
(författare)
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Technology development of 3D detectors for high-energy physics and imaging
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 487:02-jan, s. 19-26
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Tidskriftsartikel (refereegranskat)abstract
- Various fabrications routes to create '3D' detectors have been investigated and the electrical characteristics of these structures have been compared to simulations. The geometry of the detectors is hexagonal with a central anode surrounded by six cathode contacts. A uniform electric field is obtained with the maximum drift and depletion distance set by electrode spacings rather than detector thickness. This should improve the ability of silicon to operate in the presence of the severe bulk radiation damage expected in high-energy colliders. Moreover, 3D detectors made with other materials (e.g. GaAs, SiC) may be used, for example, in X-ray detection for medical imaging. Holes in the substrate were made either by etching with an inductively coupled plasma machine, by laser drilling or by photochemical etching. A number of different hole diameters and thickness have been investigated. Experimental characteristics have been compared to MEDICI simulations.
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| 59. |
- Sandgren, M., Gualfetti, P.J., Paech, C., Paech, S., Shaw, A., Gross, L.S., Saldajeno, M., Berglund, G.I., Jones, T.A. & Mitchinson, C.
(författare)
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The Humicloa grisea Cel12A enzyme structure at 1.2 Å resolution and the impact of its free cysteine residues on thermal stability
- 2003
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Ingår i: Protein Science. ; 12, s. 2782-2793
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Tidskriftsartikel (refereegranskat)
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| 60. |
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