4,162 research outputs found
Glycaemic status, insulin resistance, and risk of infection-related mortality:a cohort study
Importance: the impact of non-diabetic hyperglycaemia and insulin resistance on infection-related mortality risk remains unknown.Objective: we investigated the association of glycaemic status and insulin resistance with infection-related mortality in individuals with and without diabetes.Design: cohort study based on Kangbuk Samsung Health Study and national death records.Participants: about 666 888 Korean adults who underwent fasting blood measurements including glucose, glycated haemoglobin (HbA1c), and insulin during health-screening examinations were followed for up to 15.8 years.Main outcome and measures: infection-related mortality, therefore we used Cox proportional hazards regression analyses to estimate hazard ratios (HRs) and 95% CIs for infection-related mortality. Vital status and infection-related mortality were ascertained through national death records. Variable categories were created based on established cut-offs for glucose and HbA1c levels and homeostatic model assessment of insulin resistance (HOMA-IR) quintiles.Results: during a median follow-up of 8.3 years, 313 infectious disease deaths were dentified. The associations of glucose and HbA1c levels with infection-related mortality were J-shaped (P for quadratic trend<.05). The multivariable-adjusted HR (95% CIs) for infection-related mortality comparing glucose levels <5, 5.6-6.9, and â„7.0 mmol/L to 5.0â5.5 mmol/L (the reference) were 2.31 (1.47â3.64), 1.65 (1.05â2.60), and 3.41 (1.66â7.00), respectively. Among individuals without diabetes, the multivariable-adjusted HR for infection-related mortality for insulin resistance (HOMA-IR â„75th centile versus <75th centile) was 1.55 (1.04â2.32).Conclusions and relevance: both low and high glycaemic levels and insulin resistance were independently associated with increased infection-related mortality risk, indicating a possible role of abnormal glucose metabolism in increased infection-related mortality.<br/
Super Helium-Rich Population and the Origin of Extreme Horizontal-Branch Stars in Globular Clusters
Recent observations for the color-magnitude diagrams (CMDs) of the massive
globular cluster Omega Centauri have shown that it has a striking double main
sequence (MS), with a minority population of bluer and fainter MS well
separated from a majority population of MS stars. Here we confirm, with the
most up-to-date Y2 isochrones, that this special feature can only be reproduced
by assuming a large variation (Delta Y = 0.15) of primordial helium abundance
among several distinct populations in this cluster. We further show that the
same helium enhancement required for this special feature on the MS can by
itself reproduce the extreme horizontal-branch (HB) stars observed in Omega
Cen, which are hotter than normal HB stars. Similarly, the complex features on
the HBs of other globular clusters, such as NGC 2808, are explained by large
internal variations of helium abundance. Supporting evidence for the
helium-rich population is also provided by the far-UV (FUV) observations of
extreme HB stars in these clusters, where the enhancement of helium can
naturally explain the observed fainter FUV luminosity for these stars. The
presence of super helium-rich populations in some globular clusters suggests
that the third parameter, other than metallicity and age, also influences CMD
morphology of these clusters.Comment: 4 pages, 4 figures, accepted for publication in the Astrophysical
Journal Letter
RR Lyrae Stars in the Field of Sagittarius II
We present the detection of RR Lyrae variable stars in the field of the Sagittarius. II (Sgr II) ultra-faint dwarf (UFD) galaxy. Using B, V time-series photometry obtained with the Korea Microlensing Telescope Network (KMTNet) 1.6 m telescope at CTIO and G-band data from Gaia Data Release 2 (DR2), we identified and characterized two ab-type and four c-type RR Lyrae variables. Five out of the six stars are clustered within three half-light radii (similar to 4'.8) of the galaxy indicating their association with Sgr. II, while the RRab star V4 is located similar to 22' from the galaxy center. By excluding V4, the high c-type fraction (0.8) and the period of the only RRab star V3 (P-V3 similar or equal to 0.666 days) suggest an Oosterhoff. II (Oo II) classification for Sgr. II. Located close to the locus of Oo. II clusters in the period-amplitude diagram, V3 is similar to RRab stars in other UFDs having Oosterh off-intermediate and Oo. II properties. Sgr. II is, however, more compact than usual UFDs, placed in between star clusters and dwarf galaxies in the size-luminosity plane, and therefore spectroscopic studies are eventually required to ascertain the true nature of this stellar system. We derive the metallicity ([Fe/H] RRab similar or equal to -2.1 +/- 0.3) and heliocentric distance (similar to 64 +/- 3 kpc) of Sgr. II from the RR Lyrae stars, and estimate its age (similar to 12 Gyr) based on our stellar population models. The Oosterhoff properties of UFDs can be explained with the evolution effect of RR Lyrae stars in the instability strip.Funding for the DPAC has been provided by national institutions, in
particular the institutions participating in the Gaia Multilateral Agreement. S.C.R was partially supported by the Basic Science Research Program through the NRF of Korea funded by the Ministry of Education (2018R1A2B2006445). Support for this work was also provided by the NRF to the Center for Galaxy Evolution Research (2017R1A5A1070354). H. Jerjen acknowledges the support of the Australian Research Council through Discovery Project DP150100862. H. Jeong acknowledges support from the Basic Science Research Program through the National Research Foundation (NRF) of Korea, funded by the Ministry of Education (NRF2013R1A6A3A04064993). This research was made possible through the use of the APASS, funded by the Robert Martin Ayers Sciences Fund
A Spectro-photometric Search for Galaxy Clusters in SDSS
Recent large-scale galaxy spectroscopic surveys, such as the Sloan Digital
Sky Survey (SDSS), enable us to execute a systematic, relatively-unbiased
search for galaxy clusters. Such surveys make it possible to measure the 3-d
distribution of galaxies but are hampered by the incompleteness problem due to
fiber collisions. In this study we aim to develop a density measuring technique
that alleviates the problem and derives densities more accurately by adding
additional cluster member galaxies that follow optical color-magnitude
relations for the given redshift. The new density measured with both
spectroscopic and photometric data shows a good agreement with apparent
information on cluster images and is supported by follow-up observations. By
adopting this new method, a total of 924 galaxy clusters are found
from the SDSS DR5 database in the redshift range , of which 212 are
new. Local maximum-density galaxies successfully represent cluster centers. We
provide the cluster catalogue including a number of cluster parameters.Comment: Web-page address has been revised and minor corrections are don
- âŠ