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- Christlieb, N., et al.
(författare)
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The Hamburg/ESO R-process Enhanced Star survey (HERES). I. Project description, and discovery of two stars with strong enhancements of neutron-capture elements
- 2004
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 428:3, s. 1027-1037
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Tidskriftsartikel (refereegranskat)abstract
- We report on a dedicated effort to identify and study metal-poor stars strongly enhanced in r-process elements ([r/Fe]>1 dex; hereafter r-IIstars), the Hamburg/ESO R-process Enhanced Star survey (HERES).Moderate-resolution (∼2 Å) follow-up spectroscopy has been obtained for metal-poor giant candidates selected from the Hamburg/ESO objective-prism survey (HES) as well as the HK survey to identify sharp-lined stars with [Fe/H]<-2.5 dex. For several hundred confirmed metal-poor giants brighter than B∼ 16.5 mag (most of them from theHES), ``snapshot'' spectra (R∼ 20 000; S/N ∼ 30 per pixel) are being obtained with VLT/UVES, with the main aim of finding the 2-3% r-II stars expected to be among them. These are studied in detail by means of higher resolution and higher S/N spectra. In this paper we describe a pilot study based on a set of 35 stars, including 23 from the HK survey,eight from the HES, and four comparison stars. We discovered two new r-II stars, CS 29497-004 ([Eu/Fe]=1.64± 0.22) and CS 29491-069([Eu/Fe]=1.08± 0.23). A first abundance analysis of CS 29497-004 yields that its abundances of Ba to Dy are on average enhanced by 1.5 dex with respect to iron and the Sun and match a scaled solar r-process pattern well, while Th is underabundant relative to that pattern by 0.3dex, which we attribute to radioactive decay. That is, CS 29497-004 seems not to belong to the class of r-process enhanced stars displaying an ``actinide boost'', like CS 31082-001 (Hill et al. 2002), or CS30306-132 (Honda et al. 2004b). The abundance pattern agrees well with predictions of the phenomenological model of Qian & Wasserburg.Based in large part on observations collected at the European Southern Observatory, Paranal, Chile (proposal number 68.B-0320).}
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- Ristow, M, et al.
(författare)
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Frataxin deficiency in pancreatic islets causes diabetes due to loss of beta cell mass
- 2003
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Ingår i: Journal of Clinical Investigation. - 0021-9738. ; 112:4, s. 527-534
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Tidskriftsartikel (refereegranskat)abstract
- Diabetes is caused by an absolute (type 1) or relative (type 2) deficiency of insulin-producing beta cells. We have disrupted expression of the mitochondrial protein frataxin selectively in pancreatic beta cells. Mice were born healthy but subsequently developed impaired glucose tolerance progressing to overt diabetes mellitus. These observations were explained by impairment of insulin secretion due to a loss of beta cell mass in knockout animals. This phenotype was preceded by elevated levels of reactive oxygen species in knockout islets, an increased frequency of apoptosis, and a decreased number of proliferating beta cells. Hence, disruption of the frataxin gene in pancreatic beta cells causes diabetes following cellular growth arrest and apoptosis, paralleled by an increase in reactive oxygen species in islets. These observations might provide insight into the deterioration of beta cell function observed in different subtypes of diabetes in humans.
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- Shergur J, Brown BA, Fedoseyev V, Koster U, Kratz KL, Sweryniak D, Walters WB, Wohr A, Fedorov D, Hannawald M, Hjorth-Jensen M, Mishin V, Pfeiffer B, Ressler JJ, Fynbo HOU, Hoff P, Mach H, Nilsson T, Wilhelmsen-Rolander K, Simon H, Bickley A and the ISOLD
(författare)
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Beta-Decay Studies of 135-137Sn using Selective Resonance Laser Ionization Techniques
- 2002
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Ingår i: Phys. Rev.. ; C65, s. 34313-
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Tidskriftsartikel (refereegranskat)
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