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- Bensby, Thomas, et al.
(författare)
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Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars IV. Two bulge populations
- 2011
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 533
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Tidskriftsartikel (refereegranskat)abstract
- Based on high-resolution (R approximate to 42 000 to 48 000) and high signal-to-noise (S/N approximate to 50 to 150) spectra obtained with UVES/VLT, we present detailed elemental abundances (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, and Ba) and stellar ages for 12 new microlensed dwarf and subgiant stars in the Galactic bulge. Including previous microlensing events, the sample of homogeneously analysed bulge dwarfs has now grown to 26. The analysis is based on equivalent width measurements and standard 1-D LTE MARCS model stellar atmospheres. We also present NLTE Li abundances based on line synthesis of the Li-7 line at 670.8 nm. The results from the 26 microlensed dwarf and subgiant stars show that the bulge metallicity distribution (MDF) is double-peaked; one peak at [Fe/H] approximate to -0.6 and one at [Fe/H] approximate to +0.3, and with a dearth of stars around solar metallicity. This is in contrast to the MDF derived from red giants in Baade's window, which peaks at this exact value. A simple significance test shows that it is extremely unlikely to have such a gap in the microlensed dwarf star MDF if the dwarf stars are drawn from the giant star MDF. To resolve this issue we discuss several possibilities, but we can not settle on a conclusive solution for the observed differences. We further find that the metal-poor bulge dwarf stars are predominantly old with ages greater than 10 Gyr, while the metal-rich bulge dwarf stars show a wide range of ages. The metal-poor bulge sample is very similar to the Galactic thick disk in terms of average metallicity, elemental abundance trends, and stellar ages. Speculatively, the metal-rich bulge population might be the manifestation of the inner thin disk. If so, the two bulge populations could support the recent findings, based on kinematics, that there are no signatures of a classical bulge and that the Milky Way is a pure-disk galaxy. Also, recent claims of a flat IMF in the bulge based on the MDF of giant stars may have to be revised based on the MDF and abundance trends probed by our microlensed dwarf stars.
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- Sudhakar, P., et al.
(författare)
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Biomarkers for IBD using OLINK Proteomics inflammation panel : Preliminary results from the COLLIBRI consortium
- 2022
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Ingår i: Journal of Crohn's & Colitis. - : Oxford University Press. - 1873-9946 .- 1876-4479. ; 16:Suppl. 1, s. I123-I124
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Background: Circulating serum proteins have provided insights into disease pathogenesis and are being used to identify prognostic, diagnostic and therapeutic biomarkers for chronic inflammatory diseases. With this pilot project, the Collaborative IBD Biomarker Research Initiative (COLLIBRI) consortium aimed to unravel disease heterogeneity in inflammatory bowel disease (IBD).Methods: Serum samples were cross-sectionally obtained from 3,390 indi -viduals (Crohn’s disease (CD), n=1815; ulcerative colitis (UC), n=1170;healthy, n=405) recruited at nine centres from Sweden and Belgium. Relative levels of 92 proteins were analysed using the Proseek Multiplex Inflammation I Probe kit 96x96 (Olink Proteomics, Uppsala, Sweden) and reported as arbitrary units, i.e., normalised protein expression on a log2 scale. Using a multivariate integrative approach, we identified protein signatures distinguishing CD and UC samples and attempted to identify clusters or subgroups within patients. Recruiting centre, cohort and batch information were considered for the integrative analysis. Optimisation was performed for identifying the number of components and features per component using 5-fold cross-validation and Leave-One-Group-Out-Cross-Validation, respectively. Information on transcriptional regulators was retrieved from the ReMap project using the orthogonal regulatory resource ChEA3.Results: A panel of 8 proteins was identified which could segregate CD and UC patients (Figure 1). FGF19 exhibited a consistent trend of expression (downregulated in CD) across all batches of datasets. An integrated AUC of 72.5% was achieved across the different batches of samples used in the study with the highest AUC (79.2%, P-value 8.5e-07) being recorded for a single batch of samples (CD = 42, UC = 56). On a centre-specific dataset, the cross-centre integrated signature achieved an AUC of 75.1%. We identified three transcription factors (MEF2A, BATF, NFKB2), of which the two latter ones are known to modulate intestinal inflammation and which could potentially regulate the expression of at least half of the genes encoding the proteins in the predictive 8-protein panel.Conclusion: We identified an integrated proteomic biomarker panel capable of separating CD and UC patients. Through further integration of confounder variables along with using other supervised and unsupervised approaches, subsequent analyses may further refine the molecul arheterogeneity among CD and UC patients. Our results demonstrate the need for large datasets to identify relevant clusters of patients with IBD, since the diagnosis exhibits a high degree of clinical heterogeneity.
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