197 research outputs found
Atmospheric Parameters and Metallicities for 2191 stars in the Globular Cluster M4
We report new metallicities for stars of Galactic globular cluster M4 using
the largest number of stars ever observed at high spectral resolution in any
cluster. We analyzed 7250 spectra for 2771 cluster stars gathered with the VLT
FLAMES+GIRAFFE spectrograph at VLT. These medium resolution spectra cover by a
small wavelength range, and often have very low signal-to-noise ratios. We
attacked this dataset by reconsidering the whole method of abundance analysis
of large stellar samples from beginning to end. We developed a new algorithm
that automatically determines the atmospheric parameters of a star. Nearly all
data preparation steps for spectroscopic analyses are processed on the
syntheses, not the observed spectra. For 322 Red Giant Branch stars with we obtain a nearly constant metallicity, ( = 0.02). No difference in the metallicity at the level of
is observed between the two RGB sequences identified by
\cite{Monelli:2013us}. For 1869 Subgiant and Main Sequence Stars we
obtain ( = 0.09) after fixing the
microturbulent velocity. These values are consistent with previous studies that
have performed detailed analyses of brighter RGB stars at higher spectroscopic
resolution and wavelength coverage. It is not clear if the small mean
metallicity difference between brighter and fainter M4 members is real or is
the result of the low signal-to-noise characteristics of the fainter stars. The
strength of our approach is shown by recovering a metallicity close to a single
value for more than two thousand stars, using a dataset that is non-optimal for
atmospheric analyses. This technique is particularly suitable for noisy data
taken in difficult observing conditions.Comment: 17 pages, 20 figures, 3 tables. Accepted for publication in The
Astronomical Journa
First evidence of multiple populations along the AGB from Str\"omgren photometry
Spectroscopic studies have demonstrated that nearly all Galactic globular
clusters (GCs) harbour multiple stellar populations with different chemical
compositions. Moreover, colour-magnitude diagrams based exclusively on
Str\"omgrem photometry have allowed us to identify and characterise multiple
populations along the RGB of a large number of clusters. In this paper we show
for the first time that Str\"omgren photometry is also very effcient at
identifying multiple populations along the AGB, and demonstrate that the AGB of
M3, M92, NGC362, NGC1851, and NGC6752 are not consistent with a single stellar
population. We also provide a catalogue of RGB and AGB stars photometrically
identified in these clusters for further spectroscopic follow-up studies.We
combined photometry and elemental abundances from the literature for RGB and
AGB stars in NGC6752 where the presence of multiple populations along the AGB
has been widely debated. We find that, while the MS, SGB, and RGB host three
stellar populations with different helium and light element abundances, only
two populations of AGB stars are present in the cluster. These results are
consistent with standard evolutionary theory.Comment: 9 pages, 3 figures, 1 table in the main article, 3 tables in the
appendix of which 2 tables containing coordinates and photometry of
photometrically identified RGB and AGB star
Laparoscopic Repair of Left Lumbar Hernia After Laparoscopic Left Nephrectomy
Laparoscopic transabdominal preperitoneal repair of a lumber hernia after laparoscopic retroperitoneal surgery can be performed safely with minimum postoperative pain
Molecular characterization of 18S rDNA partial sequence in Microcosmus (Stolidobranchiata, Pyuridae)
We present a 18S rDNA based molecular phylogeny of two species of the genus Microcosmus (M. sulcatus and M. claudicans) sampled in the Mediterranean, to investigate their phylogenetic position relative to species of the order Stolidobranchiata. The analysis is based on partial sequences (739 bp) of the 18S rDNA. Among the 18 variable sites found between the two species, 4 correspond to transitions (ts), 14 to transversions (tv) and 4 to deletions/insertions. In the considered Stolidobranchiata, we found 4.3% overall mean number of nucleotide differences and 0.06 (S.E. ±0.01) Kimura 2-parameter distance. The mean number of nucleotide differences between Microcosmus spp. and other Stolidobranchiata species was of 6% and 0.08 (S.E. ±0.01) Kimura 2-parameter distance. A molecular phylogeny obtained by Maximum Parsimony corroborates results of the traditional taxonomy
Atomic diffusion and mixing in old stars VI: The lithium content of M30
The prediction of the PLANCK-constrained primordial lithium abundance in the
Universe is in discordance with the observed Li abundances in warm Population
II dwarf and subgiant stars. Among the physically best motivated ideas, it has
been suggested that this discrepancy can be alleviated if the stars observed
today had undergone photospheric depletion of lithium. The cause of this
depletion is investigated by accurately tracing the behaviour of the lithium
abundances as a function of effective temperature. Globular clusters are ideal
laboratories for such an abundance analysis as the relative stellar parameters
of their stars can be precisely determined. We performed a homogeneous chemical
abundance analysis of 144 stars in the metal-poor globular cluster M30, ranging
from the cluster turnoff point to the tip of the red giant branch. NLTE
abundances for Li, Ca, and Fe were derived where possible. Stellar parameters
were derived by matching isochrones to the observed V vs V-I colour-magnitude
diagram. Independent effective temperatures were obtained from automated
profile fitting of the Balmer lines and by applying colour-T_eff calibrations
to the broadband photometry. Li abundances of the turnoff and early subgiant
stars form a thin plateau that is broken off abruptly in the middle of the SGB
as a result of the onset of Li dilution caused by the first dredge-up.
Abundance trends with effective temperature for Fe and Ca are observed and
compared to predictions from stellar structure models including atomic
diffusion and ad hoc additional mixing below the surface convection zone. The
comparison shows that the stars in M30 are affected by atomic diffusion and
additional mixing. After applying a conservative correction for atomic
diffusion, we find an initial Li abundance of A(Li) = for the
globular cluster M30.Comment: 13 pages, 7 tables (Tab. 1 and 5 can be obtained at ADS) and 8
figure
Finding the Pareto Optimal Equitable Allocation of Homogeneous Divisible Goods Among Three Players
We consider the allocation of a finite number of homogeneous divisible items among three players. Under the assumption that each player assigns a positive value to every item, we develop a simple algorithm that returns a Pareto optimal and equitable allocation. This is based on the tight relationship between two geometric objects of fair division: The Individual Pieces Set (IPS) and the Radon\u2013Nykodim Set (RNS). The algorithm can be considered as an extension of the Adjusted Winner procedureby Brams and Taylor to the three-player case, without the guarantee of envy-freeness
Discovery of Extended Main Sequence Turnoffs in Galactic Open Clusters
The color-magnitude diagrams (CMDs) of Galactic open clusters are widely considered to be the prototypes of single stellar populations. By using photometry in ultraviolet and optical bands we discovered that the nearby young cluster NGC 6705 (M11) exhibits an extended main-sequence turnoff (eMSTO) and a broadened main sequence (MS). This is the first evidence of multiple stellar populations in a Galactic open cluster. By using high-resolution Very Large Telescope (VLT) spectra we provide direct evidence that the multiple sequences along the CMD correspond to stellar populations with different rotation rates. Specifically, the blue MS (bMS) is formed of slow-rotating stars, while red-MS (rMS) stars are fast rotators. Moreover, we exploit photometry from Gaia data release 2 (DR2) to show that three Galactic open clusters, namely NGC 2099, NGC 2360, and NGC 2818, exhibit the eMSTO, thus suggesting that it is a common feature among these objects. Our previous work on the Large Magellanic Cloud star cluster NGC 1818 shows that slowly and rapidly rotating stars populate the bMS and rMS observed in its CMD. The similarities between M11 and the young clusters of the Magellanic Clouds (MCs) suggest that rotation is responsible for the appearance of multiple populations in the CMDs of both Milky Way open clusters and MCs young clusters.A.F.M.
and L.C. acknowledge support by the Australian Research
Council through Discovery Early Career Researcher Award
DE160100851 and the Future Fellowship FT160100402.
A.P.M. has been supported by the European Research Council
through the Starting Grant âGALFORâ (716082) and the FAREMIUR project R164RM93XW âSEMPLICEâ. A.S., L.B.N., and
F.V. are partially supported by the MINECO (Spanish Ministry of
Economy) through grants ESP2017-82674-R and ESP2016-
80079-C2-1-R (MINECO/FEDER, UE), SGR-1131 (Generalitat
Catalunya), and MDM-2014-0369 of ICCUB (Unidad de
Excelencia âMarĂa de Maeztuâ)
Clinical and prognostic implications of the genetic diagnosis of hereditary NET syndromes in asymptomatic patients
Neuroendocrine tumors (NETs) can be sporadic or they can arise in complex hereditary syndromes. Patients with hereditary NETs can be identified before the development of tumors by performing genetic screenings. The aim of the study was to evaluate the clinical and prognostic impact of a preclinical genetic screening in subjects with hereditary NET syndromes. 46 subjects referred for hereditary NET syndrome [22 MEN1, 12 MEN2, 12 Familial Paragangliomatosis (FPGL)] were enrolled and divided in 2 groups (group A, 20 subjects with clinical appearance of NET before the genetic diagnosis; group B, 26 subjects with genetic diagnosis of hereditary NET syndromes before the clinical appearance of NETs). The main outcome measures were severity of disease, prognosis, and survival. The rate of surgery for MEN1-, MEN2-, FPGL4-related tumors was 90% in group A and 35% in group B (p<0.01). Both symptoms related to tumors and symptoms related to therapies were significantly less frequent in group B than in group A (p<0.05). Tumor stage was locally advanced or metastatic in 50% of group A and in no one of group B (p<0.01). The mortality rate was 25% in group A and 0% in group B (p<0.05). An early genetic screening for hereditary NET syndromes results in an improvement in clinical presentation and morbidity. A potential impact of the genetic screening on the mortality rate of these subjects is suggested and needs to be investigated in further and more appropriate studies
First evidence of multiple populations along the AGB from Strömgren photometry
Spectroscopic studies have demonstrated that nearly all Galactic globular clusters (GCs) harbour multiple stellar populations with different chemical compositions. Moreover, colour-magnitude diagrams based exclusively on Strömgrem photometry have allowed us to identify and characterise multiple populations along the RGB of a large number of clusters. In this paper we show for the first time that Strömgren photometry is also very efficient at identifying multiple populations along the AGB, and demonstrate that the AGB of Mâ3, Mâ92, NGCâ362, NGCâ1851, and NGCâ6752 are not consistent with a single stellar population. We also provide a catalogue of RGB and AGB stars photometrically identified in these clusters for further spectroscopic follow-up studies. We combined photometry and elemental abundances from the literature for RGB and AGB stars in NGCâ6752 where the presence of multiple populations along the AGB has been widely debated. We find that, while the MS, SGB, and RGB host three stellar populations with different helium and light element abundances, only two populations of AGB stars are present in the cluster. These results are consistent with standard evolutionary theory.P.G. acknowledges support from grant No. 2011- 5042 from the Swedish Research Council. S.F acknowledge the grant The New Milky Way from the Knut and Alice Wallenberg Foundation. P.G. and S.F. acknowledges support from the Swedish National Space Board. AS acknowledges support from MINECO (ESP2015-66134-R) and Generalitat de Catalunya (SGR2014-1458). L.C gratefully acknowledge support from the Australian Research Council (grants DP150100250, FT160100402). A. P. M. acknowledges support by the Australian Research Council through Discovery Early Career Researcher Award DE150101816
Knowledge, attitude, and practice of artificial intelligence in emergency and trauma surgery, the ARIES project : an international web-based survey
Aim We aimed to evaluate the knowledge, attitude, and practices in the application of AI in the emergency setting among international acute care and emergency surgeons. Methods An online questionnaire composed of 30 multiple choice and open-ended questions was sent to the members of the World Society of Emergency Surgery between 29th May and 28th August 2021. The questionnaire was developed by a panel of 11 international experts and approved by the WSES steering committee. Results 200 participants answered the survey, 32 were females (16%). 172 (86%) surgeons thought that AI will improve acute care surgery. Fifty surgeons (25%) were trained, robotic surgeons and can perform it. Only 19 (9.5%) were currently performing it. 126 (63%) surgeons do not have a robotic system in their institution, and for those who have it, it was mainly used for elective surgery. Only 100 surgeons (50%) were able to define different AI terminology. Participants thought that AI is useful to support training and education (61.5%), perioperative decision making (59.5%), and surgical vision (53%) in emergency surgery. There was no statistically significant difference between males and females in ability, interest in training or expectations of AI (p values 0.91, 0.82, and 0.28, respectively, Mann-Whitney U test). Ability was significantly correlated with interest and expectations (p < 0.0001 Pearson rank correlation, rho 0.42 and 0.47, respectively) but not with experience (p = 0.9, rho - 0.01). Conclusions The implementation of artificial intelligence in the emergency and trauma setting is still in an early phase. The support of emergency and trauma surgeons is essential for the progress of AI in their setting which can be augmented by proper research and training programs in this area.Peer reviewe
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