11 research outputs found
Massive stars in metal-poor dwarf galaxies are often extreme rotators
We probe how common extremely rapid rotation is among massive stars in the
early universe by measuring the OBe star fraction in nearby metal-poor dwarf
galaxies. We apply a new method that uses broad-band photometry to measure the
galaxy-wide OBe star fractions in the Magellanic Clouds and three more distant,
more metal-poor dwarf galaxies. We find OBe star fractions of ~20% in the Large
Magellanic Cloud (0.5 Z_Solar), and ~30% in the Small Magellanic Cloud (0.2
Z_Solar) as well as in the so-far unexplored metallicity range from 0.1 Z_solar
to 0.2 Z_solar occupied by the other three dwarf galaxies. Our results imply
that extremely rapid rotation is common among massive stars in metal-poor
environments such as the early universe.Comment: Conference proceedings for a talk in IAU Symposium 361: Massive Stars
Near and Far, Ballyconnell, Ireland, 9-13 May 202
Towards an understanding of the Of?p star HD 191612: optical spectroscopy
We present extensive optical spectroscopy of the early-type magnetic star HD
191612 (O6.5f?pe-O8fp). The Balmer and HeI lines show strongly variable
emission which is highly reproducible on a well-determined 538-d period. Metal
lines and HeII absorptions (including many selective emission lines but
excluding He II 4686A emission) are essentially constant in line strength, but
are variable in velocity, establishing a double-lined binary orbit with P(orb)
= 1542d, e=0.45. We conduct a model-atmosphere analysis of the primary, and
find that the system is consistent with a O8: giant with a B1: main-sequence
secondary. Since the periodic 538-d changes are unrelated to orbital motion,
rotational modulation of a magnetically constrained plasma is strongly favoured
as the most likely underlying `clock'. An upper limit on the equatorial
rotation is consistent with this hypothesis, but is too weak to provide a
strong constraint.Comment: Accepted for MNRA
The Chemical Composition of Two Supergiants in the Dwarf Irregular Galaxy WLM
[Abridged] The chemical composition of two stars in WLM has been determined
from high quality UVES data obtained at the VLT UT2 (program 65.N-0375). The
model atmospheres analysis shows that they have the same metallicity, [Fe/H] =
-0.38 +/-0.20, and [Mg/Fe] = -0.24 +/-0.16. This result suggests that the
[alpha(Mg)/Fe] ratio in WLM may be suppressed relative to solar abundances
(also supported by differential abundances relative to similar stars in NGC6822
and the SMC). The absolute Mg abundance, [Mg/H] = -0.62 is high relative to
what is expected from the nebulae though, where two independent spectroscopic
analyses of the HII regions in WLM yield [O/H] = -0.89. Intriguingly, the
oxygen abundance determined from the OI 6158 feature in one WLM star is [O/H] =
-0.21 +/-0.10, corresponding to five times higher than the nebular oxygen
abundance. This is the first time that a significant difference between young
stellar and nebular oxygen abundances has been found, and presently, there is
no simple explanation for this difference. If the stellar abundances reflect
the true composition of WLM, then this galaxy lies well above the
metallicity-luminosity relationship for dwarf irregular galaxies. It also
suggests that WLM is more chemically evolved than currently interpreted from
its color-magnitude diagram.Comment: 27 pages, 7 tables, 10 figures. accepted for publication in the
Astronomical Journa
Genetic mechanisms of critical illness in COVID-19.
Host-mediated lung inflammation is present1, and drives mortality2, in the critical illness caused by coronavirus disease 2019 (COVID-19). Host genetic variants associated with critical illness may identify mechanistic targets for therapeutic development3. Here we report the results of the GenOMICC (Genetics Of Mortality In Critical Care) genome-wide association study in 2,244 critically ill patients with COVID-19 from 208 UK intensive care units. We have identified and replicated the following new genome-wide significant associations: on chromosome 12q24.13 (rs10735079, P = 1.65 × 10-8) in a gene cluster that encodes antiviral restriction enzyme activators (OAS1, OAS2 and OAS3); on chromosome 19p13.2 (rs74956615, P = 2.3 × 10-8) near the gene that encodes tyrosine kinase 2 (TYK2); on chromosome 19p13.3 (rs2109069, P = 3.98 × 10-12) within the gene that encodes dipeptidyl peptidase 9 (DPP9); and on chromosome 21q22.1 (rs2236757, P = 4.99 × 10-8) in the interferon receptor gene IFNAR2. We identified potential targets for repurposing of licensed medications: using Mendelian randomization, we found evidence that low expression of IFNAR2, or high expression of TYK2, are associated with life-threatening disease; and transcriptome-wide association in lung tissue revealed that high expression of the monocyte-macrophage chemotactic receptor CCR2 is associated with severe COVID-19. Our results identify robust genetic signals relating to key host antiviral defence mechanisms and mediators of inflammatory organ damage in COVID-19. Both mechanisms may be amenable to targeted treatment with existing drugs. However, large-scale randomized clinical trials will be essential before any change to clinical practice
Recommendations for head and neck surgical oncology practice in a setting of acute severe resource constraint during the COVID-19 pandemic: an international consensus.
The speed and scale of the global COVID-19 pandemic has resulted in unprecedented pressures on health services worldwide, requiring new methods of service delivery during the health crisis. In the setting of severe resource constraint and high risk of infection to patients and clinicians, there is an urgent need to identify consensus statements on head and neck surgical oncology practice. We completed a modified Delphi consensus process of three rounds with 40 international experts in head and neck cancer surgical, radiation, and medical oncology, representing 35 international professional societies and national clinical trial groups. Endorsed by 39 societies and professional bodies, these consensus practice recommendations aim to decrease inconsistency of practice, reduce uncertainty in care, and provide reassurance for clinicians worldwide for head and neck surgical oncology in the context of the COVID-19 pandemic and in the setting of acute severe resource constraint and high risk of infection to patients and staff
Recommendations for head and neck surgical oncology practice in a setting of acute severe resource constraint during the COVID-19 pandemic: an international consensus
The speed and scale of the global COVID-19 pandemic has resulted in unprecedented pressures on health services worldwide, requiring new methods of service delivery during the health crisis. In the setting of severe resource constraint and high risk of infection to patients and clinicians, there is an urgent need to identify consensus statements on head and neck surgical oncology practice. We completed a modified Delphi consensus process of three rounds with 40 international experts in head and neck cancer surgical, radiation, and medical oncology, representing 35 international professional societies and national clinical trial groups. Endorsed by 39 societies and professional bodies, these consensus practice recommendations aim to decrease inconsistency of practice, reduce uncertainty in care, and provide reassurance for clinicians worldwide for head and neck surgical oncology in the context of the COVID-19 pandemic and in the setting of acute severe resource constraint and high risk of infection to patients and staff