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| 3. |
- Sikstrom, C. M, et al.
(författare)
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New Zr II oscillator strengths and the zirconium conflict in the HgMn star chi Lupi
- 1999
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Ingår i: Astronomy & Astrophysics. - 0004-6361. ; 343:1, s. 297-302
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Tidskriftsartikel (refereegranskat)abstract
- Lifetimes on the sub-nanosecond scale for the levels v(2)D(3/2), v(2)F(3/2) and v(2)F(5/2) in the 4d5s5p configuration in Zr II have been measured, using the method of laser-induced fluorescence. Combined with branching fractions obtained with the Lund Ultraviolet (UV) Fourier Transform Spectrometer (FTS), experimental oscillator strengths have been derived. From Hubble Space Telescope/Goddard High-Resolution Spectrograph spectra, the zirconium abundance in the HgMn star chi Lupi has been determined from Zr II and Zr III lines. More than an order of magnitude difference in the Zr II abundance has been derived from these ionization stages. The difference is much too large to be explained by uncertainties in the oscillator strengths. Possible explanations of this difference have to be found in the stellar models, such as the influence of non-LTE or diffusion.
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| 5. |
- Biemont, E, et al.
(författare)
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Lifetimes and oscillator strengths for ultraviolet transitions in neutral sulfur
- 1998
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 502:2, s. 1010-1014
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Tidskriftsartikel (refereegranskat)abstract
- A consistent set of f-values for vacuum ultraviolet lines of S I is deduced from a combination of laser lifetime measurements and theoretical branching ratios. The new results are compared with results deduced from absorption by interstellar gas toward zeta Ophiuchi, and good agreement is observed for most transitions.
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| 6. |
- Biemont, E, et al.
(författare)
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Radiative lifetimes, branching fractions and transition probabilities in Ge I - solar implications
- 1999
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 303:4, s. 721-726
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Tidskriftsartikel (refereegranskat)abstract
- New radiative lifetimes have been measured for the 5s (3)P(0,1,2)degrees and 5s (1)P(1)degrees levels of Ge I using a laser-produced plasma subject to selective laser excitation. A diffraction grating based emission spectrometer of moderately high resolution has been used to remeasure the branching ratios of the 4p-5s depopulating transitions. The oscillator strengths of astrophysical interest, which have been derived from these new data, are compared with theoretical values calculated within a pseudo-relativistic Hartree-Fock approach. The new set of f-values has been compared with the few results available in the literature, which are generally characterized by a large scatter and a low accuracy. The solar photospheric abundance of germanium deduced from the new atomic data of the present work is A(Ge) = 3.58 +/- 0.05, on the usual logarithmic scale, in agreement with the meteoritic value.
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- Lernmark, Å, et al.
(författare)
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Heterogeneity of islet pathology in two infants with recent onset diabetes mellitus
- 1995
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Ingår i: Virchows Archiv. - 0945-6317. ; 425:6, s. 631-640
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms by which the beta cells of pancreatic islets are destroyed in insulin-dependent diabetes mellitus (IDDM) are poorly understood. In this report the pancreatic histo- and immunopathology of two children, both HLA-DR 3/4, DQ 2/8 positive and who both died from cerebral oedema within a day of clinical diagnosis of IDDM, were investigated. Patient 1, a 14-month-old girl, had a 4-week history of polydipsia and polyuria. Patient 2, a 3-year-old boy, had 2 days of illness. Both patients had a similarly severe loss of insulin cells but differed markedly as to the extent of lymphocytic islet infiltration (insulitis). Apart from insulitis, marked islet macrophage infiltration was demonstrated in both patients with the HAM-56 monoclonal antibody. Neither patient showed aberrant expression of HLA class II antigens on insulin-immunoreactive cells, but allele-specific HLA-DQ8 expression was evident on endothelial cells. Glutamic acid decarboxylase immunoreactivity was detected in both insulin- and glucagon-immunoreactive cells. It is concluded that the heterogeneity of islet pathology, especially insulitis, may reflect different dynamics and extent rather than different pathomechanisms of immune destruction of islets in IDDM.
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