| 1. |
- 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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| 2. |
- Li, Jian-Liang, et al.
(författare)
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A genome scan for modifiers of age at onset in Huntington disease : The HD MAPS study.
- 2003
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 73:3, s. 682-7
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Tidskriftsartikel (refereegranskat)abstract
- Huntington disease (HD) is caused by the expansion of a CAG repeat within the coding region of a novel gene on 4p16.3. Although the variation in age at onset is partly explained by the size of the expanded repeat, the unexplained variation in age at onset is strongly heritable (h2=0.56), which suggests that other genes modify the age at onset of HD. To identify these modifier loci, we performed a 10-cM density genomewide scan in 629 affected sibling pairs (295 pedigrees and 695 individuals), using ages at onset adjusted for the expanded and normal CAG repeat sizes. Because all those studied were HD affected, estimates of allele sharing identical by descent at and around the HD locus were adjusted by a positionally weighted method to correct for the increased allele sharing at 4p. Suggestive evidence for linkage was found at 4p16 (LOD=1.93), 6p21-23 (LOD=2.29), and 6q24-26 (LOD=2.28), which may be useful for investigation of genes that modify age at onset of HD.
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| 3. |
- Djoussé, Luc, et al.
(författare)
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Evidence for a modifier of onset age in Huntington disease linked to the HD gene in 4p16.
- 2004
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Ingår i: Neurogenetics. - : Springer Science and Business Media LLC. - 1364-6745 .- 1364-6753. ; 5:2, s. 109-14
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Tidskriftsartikel (refereegranskat)abstract
- Huntington disease (HD) is a neurodegenerative disorder caused by the abnormal expansion of CAG repeats in the HD gene on chromosome 4p16.3. A recent genome scan for genetic modifiers of age at onset of motor symptoms (AO) in HD suggests that one modifier may reside in the region close to the HD gene itself. We used data from 535 HD participants of the New England Huntington cohort and the HD MAPS cohort to assess whether AO was influenced by any of the three markers in the 4p16 region: MSX1 (Drosophila homeo box homologue 1, formerly known as homeo box 7, HOX7), Delta2642 (within the HD coding sequence), and BJ56 ( D4S127). Suggestive evidence for an association was seen between MSX1 alleles and AO, after adjustment for normal CAG repeat, expanded repeat, and their product term (model P value 0.079). Of the variance of AO that was not accounted for by HD and normal CAG repeats, 0.8% could be attributed to the MSX1 genotype. Individuals with MSX1 genotype 3/3 tended to have younger AO. No association was found between Delta2642 (P=0.44) and BJ56 (P=0.73) and AO. This study supports previous studies suggesting that there may be a significant genetic modifier for AO in HD in the 4p16 region. Furthermore, the modifier may be present on both HD and normal chromosomes bearing the 3 allele of the MSX1 marker.
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| 4. |
- Germain, K, et al.
(författare)
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Colonisation of poplar trees by gfp-expressing bacterial endophytes
- 2004
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Ingår i: FEMS Microbiology Ecology. - 0168-6496. ; 48:1, s. 109-118
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Tidskriftsartikel (refereegranskat)abstract
- With the exception of nitrogen fixing bacteria, there is little known about the colonisation patterns or population sizes of bacterial endophytes in deciduous trees. This study describes the isolation, identification, construction and re-colonisation patterns of three green fluorescent protein(gfp):kanamycinR labelled bacterial endophytes when re-introduced into poplar trees, their original host plant. Two of these endophytes showed considerable colonisation in the roots and stems of inoculated plants. gfp expressing cells of all three strains were observed to colonise the xylem tissue of the root. All three strains proved to be efficient rhizosphere colonisers, supporting the theory that the rhizosphere can serve as a source of bacterial endophytes.
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| 5. |
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