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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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| 2. |
- Cummins, D., et al.
(författare)
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Ultrafast electrochromic windows based on redox-chromophore modified nanostructured semiconducting and conducting films
- 2000
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 104:48, s. 11449-11459
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Tidskriftsartikel (refereegranskat)abstract
- Described is the construction of an ultrafast electrochromic window. One electrode of this window is based on a transparent nanostructured TiO2 (anatase) film (4.0 mum. thick) supported on conducting glass (F-doped tin oxide, 10 Ohm cm(-2), 0.5 mum thick) and modified by chemisorption of a monolayer of the redox chromophore bis(2-phosphonoethyl)-4,4'-bipyridinium dichloride. The other electrode is based on a transparent nanostructured SnO2 film (3.0 mum thick) supported on conducting glass (F-doped tin oxide, 10 Ohm cm-2, 0.5 mum thick) and modified by chemisorption of a monolayer of the redox chromophore [beta-(10-phenothiazyl)propoxy]phosphonic acid. The electrolyte used is LiClO4 (0.2 mol dm(-3)) in gamma -butyrolactone. The excellent performance of a 2.5 cm x 2.5 cm window over 10 000 electrochromic test cycles-switching times (coloring and bleaching) of less than 250 ms, coloration efficiency of 270 cm(2) C-1, steady-state currents (colored and bleached) of less than 6 muA cm(-2), and memory of greater than 600 s (time required for low end transmittance to increase by 5%)-suggest a practical technology.
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| 5. |
- Ryan, D, et al.
(författare)
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Heterosupramolecular chemistry : Recognition Initiated and Inhibited Silver Nanocrystal Aggregation
- 2000
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 122:26, s. 6252-6257
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Tidskriftsartikel (refereegranskat)abstract
- Near size-monodisperse silver nanocrystals stabilized by chemisorption of a mixture of an alkane thiol (85%) and an alkane thiol incorporating a dibenzo-24-crown-8 moiety (15%) have been prepared. Using dynamic light scattering and nuclear magnetic resonance, it is shown that addition of bis-dibenzylammonium dication initiates aggregation of the silver nanocrystal dispersion by pseudorotaxane assembly. It is also shown that addition of excess dibenzylammonium cation or dibenzo-24-crown-8 inhibits further aggregation. This novel demonstration of controlled nanocrystal aggregation points the way toward the programmed assembly of complex nanocrystal architectures in solution.
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| 6. |
- Ryan, EJ, et al.
(författare)
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Booster immunization of children with an acellular pertussis vaccine enhances Th2 cytokine production and serum IgE responses against pertussis toxin but not against common allergens
- 2000
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Ingår i: Clinical and Experimental Immunology. - : Oxford University Press (OUP). - 0009-9104 .- 1365-2249. ; 121:2, s. 193-200
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Tidskriftsartikel (refereegranskat)abstract
- Acellular pertussis vaccines (Pa) protect against severe pertussis in children. However, serum antibody responses decline quickly after immunization. Studies in animal models suggest that cell-mediated immunity also contributes to protection against Bordetella pertussis, and it has already been demonstrated that Pa induce T cells that secrete type-1 and type-2 cytokines in children. In this study we examined the persistence of the T cell response and the effect of booster immunization in 4-6-year-old children. Cell-mediated immunity to B. pertussis antigens was detected in a high proportion of children more than 42 months after their last immunization. Peripheral blood mononuclear cells (PBMC) from the majority of children secreted interferon-gamma (IFN-?) and a smaller proportion IL-5, in response to specific antigen stimulation in vitro. However, following booster immunization, significantly higher concentrations of IL-5, but not IFN-?, were produced by PBMC in response to B. pertussis antigens. Furthermore, plasma IL-4 and IL-5 concentrations were increased, whereas IFN-? concentrations were reduced following booster immunization. It has been suggested that childhood immunization with Th2-inducing vaccines may predispose some children to atopic disease. Although we found that pertussis toxin (PT)-specific IgE was significantly increased after booster immunization in both atopic and non-atopic children, the levels of IgE to common allergens and the prevalence of positive skin prick test were unaffected by the booster vaccination. Thus, despite the enhancement of type-2 responses to B. pertussis antigens, booster vaccination with Pa does not appear to be a risk factor for allergy.
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