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Sökning: WFRF:(Nilsson E) > Malmö universitet

  • Resultat 1-10 av 24
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1.
  • Biemont, E., et al. (författare)
  • Lifetime measurements and calculations in Y+ and Y2+ ions
  • 2011
  • Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 414:4, s. 3350-3359
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a new set oftheoretical transition probabilities in Y II, obtained using a multiconfiguration relativistic Hartree-Fock method including core polarization. The overall quality of the calculations is assessed by comparisons with new and previous lifetime measurements. In this paper, we report new measurements of five lifetimes in the 4d5p and 5s5p configurations, in the energy range of 32 048-44 569 cm(-1), obtained by the time-resolved laser-induced fluorescence method. A similar theoretical model, applied to Y III, leads to results in good agreement with new laser measurements of two 5p levels obtained in this work and with previous beam-foil results for 5d and 6s levels. An extensive set of oscillator strengths is also proposed for Y III.
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2.
  • Bäckström, E., et al. (författare)
  • The FERRUM project: metastable lifetimes in Cr ii
  • 2011
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 420:2, s. 1636-1639
  • Tidskriftsartikel (refereegranskat)abstract
    • Parity forbidden radiative transitions from metastable levels are observed in spectra of low-density astrophysical plasmas. These lines are used as probes of the physical conditions, made possible due to the long lifetime of their upper level. In a joint effort, the FERRUM project aims to obtain new and accurate atomic data for the iron-group elements, and part of this project concerns forbidden lines. The radiative lifetimes of the metastable energy levels 3 d4(a 3 D)4 s   c4 D 5/2 and 3 d4(a 3 D)4 s   c4 D 7/2 of singly ionized chromium have been measured. The experiment has been performed at the ion storage ring CRYRING. We employed a laser-probing technique developed for measuring long lifetimes. In this article, we present the lifetimes of these levels to be τ5/2= 1.28(16) s and τ7/2= 1.37(7) s, respectively. A comparison with previous theoretical work shows good agreement and the result is discussed in a theoretical context.
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3.
  • Engström, Lars, et al. (författare)
  • The FERRUM project : Experimental transition probabilities from highly excited even 5s levels in Cr ii
  • 2014
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 570
  • Tidskriftsartikel (refereegranskat)abstract
    • We report lifetime measurements of the five levels in the 3d4(a5D)5s e6D term in Cr ii at an energy around 83 000 cm-1, and log(g f ) values for 38 transitions from the investigated levels. The lifetimes are obtained using time-resolved, laser-induced fluorescence on ions from a laser-produced plasma. Since the levels have the same parity as the low-lying states directly populated in the plasma, we used a two-photon excitation scheme. This process is greatly facilitated by the presence of the 3d4(a5D)4p z6F levels at roughly half the energy di erence. The f -values are obtained by combining the experimental lifetimes with branching fractions derived using relative intensities from a hollow cathode lamp recorded with a Fourier transform spectrometer.
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6.
  • Goncalves, Isabel, et al. (författare)
  • Activator protein-1 in carotid plaques is related to cerebrovascular symptoms and cholesteryl ester content
  • 2011
  • Ingår i: Cardiovascular pathology. - : Elsevier. - 1054-8807 .- 1879-1336. ; 20:1, s. 36-43
  • Tidskriftsartikel (refereegranskat)abstract
    • Transcription factor activator protein-1 regulates genes involved in inflammation and repair. The aim of this study was to determine whether transcription factor activator protein-1 activity in carotid plaques is related to symptoms, lipid accumulation, or extracellular matrix composition. Methods: Twenty-eight atherosclerotic carotid plaques were removed by endarterectomy and divided into two groups based on the presence or absence of ipsilateral symptoms (b1 month ago). Activator protein-1 DNA binding activity was assessed, and subunit (c-Jun, JunD, JunB, c-Fos, FosB, Fra-1, Fra-2) protein levels analyzed by immunoblotting. Distribution of c-Jun in plaques was analyzed by immunohistochemistry. Results: Plaques associated with symptoms had increased activator protein-1 activity and increased expression of c-Jun and JunD, as compared to asymptomatic plaques. Fra-1 and Fra-2 were present in equal amounts in both groups, whereas JunB, FosB, and c-Fos were undetectable. Activator protein-1 activity correlated with cholesteryl ester and elastin in plaques and decreased with age. Activator protein-1 activity did not correlate with collagen, calcified tissue, or proteoglycan content. Conclusions: Activator protein-1 is increased in plaques associated with symptoms. The correlation between activator protein-1 and cholesteryl esters suggests that high activator protein-1 is a marker of plaque vulnerability. Activator protein-1 expression can also reflect the activation of repair processes.
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7.
  • Gunnarsson, Mikael, et al. (författare)
  • No radiation protection reasons for restrictions on C-14 urea breath tests in children.
  • 2002
  • Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 75:900, s. 982-986
  • Tidskriftsartikel (refereegranskat)abstract
    • Traditional 14C urea breath tests are normally not used for younger children because the radiation exposure is unknown. High sensitivity accelerator mass spectrometry and an ultra-low amount (440 Bq) of 14C urea were therefore used both to diagnose Helicobacter pylori (HP) infection in seven children, aged 3–6 years, and to make radiation dose estimates. The activity used was 125 times lower than the amount normally used for older children and 250 times lower than that used for adults. Results were compared with previously reported biokinetic and dosimetric data for adults and older children aged 7–14 years. 14C activity concentrations in urine and exhaled air per unit administered activity for younger children (3–6 years) correspond well with those for older children (7–14 years). For a child aged 3–6 years who is HP negative, the urinary bladder wall receives the highest absorbed dose, 0.3 mGy MBq-1. The effective dose is 0.1 mSv MBq-1 for the 3-year-old child and 0.07 mSv MBq-1 for the 6-year-old child. For two children, the 10 min and 20 min post-14C administration samples of exhaled air showed a significantly higher amount of 14C activity than for the rest of the children, that is 6% and 19% of administered activity exhaled per hour compared with 0.3–0.9% (mean 0.5%) of administered activity exhaled per hour indicating that these two children that is were HP positive. For a 3-year-old HP positive child, absorbed dose to the urinary bladder wall was 0.3 mGy MBq-1 and effective dose per unit of administered activity was 0.4 mSv MBq-1. Using 55 kBq, which is a normal amount for older children when liquid scintillation counters are used for measurement, the effective dose will be approximately 6 µSv to a 3-year-old HP negative child and 20 µSv to a HP positive child. Thus there is no reason for restrictions on performing a normal 14C urea breath test, even on young children.
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8.
  • Gurell, J., et al. (författare)
  • The FERRUM project : laboratory-measured transition probabilities for Cr II
  • 2010
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 511, s. A68-A68
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims. We measure transition probabilities for Cr II transitions from the z 4HJ, z 2DJ, y 4FJ, and y 4GJ levels in the energy range 63 000 to 68 000 cm-1.Methods. Radiative lifetimes were measured using time-resolved laser-induced fluorescence from a laser-produced plasma. In addition, branching fractions were determined from intensity-calibrated spectra recorded with a UV Fourier transform spectrometer. The branching fractions and radiative lifetimes were combined to yield accurate transition probabilities and oscillator strengths.Results. We present laboratory measured transition probabilities for 145 Cr II lines and radiative lifetimes for 14 Cr II levels. The laboratory-measured transition probabilities are compared to the values from semi-empirical calculations and laboratory measurements in the literature.
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  • Resultat 1-10 av 24

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