45 research outputs found
New fundamental parameters of the Galactic open clusters Berkeley 26, Czernik 27, Melotte 72, NGC 2479 and BH 37
We have obtained CCD UBVI_{KC} photometry down to V ~ 21.0 for the open
clusters Berkeley 26, Czernik 27, Melotte 72, NGC 2479 and BH 37. The latter
has never been studied before. Cluster stellar density profiles were obtained
from star counts in appropriate-sized boxes distributed throughout the entire
observed fields. Based on different measured indices, we estimate the ages of
Berkeley 26, Melotte 72 and NGC 2479. On the other hand, we indicate possible
solutions for the cluster fundamental parameters by matching theoretical
isochrones which reasonably reproduce the main cluster features in their CMDs.
In the case of NGC 2479, the cluster E(B-V) and E(V-I) colour excesses and
apparent distance modulus were estimated from the fit of the Zero-Age Main
Sequence (ZAMS) to the colour-colour and colour-magnitude diagrams,
respectively.Comment: MNRAS accepte
Photometry of seven overlooked open clusters in the First and Fourth Galactic Quadrants
CCD BVI photometry is presented for 7 previously unstudied star clusters
projected toward the inner side of the Galaxy: Trumpler 23, Lynga 3, Collinder
307, Ruprecht 134, ESO552SC16, AL 5 and Kronberger 3. Color magnitude diagrams
of the cluster regions allow us to conclude that Lynga 3 and ESO552SC16, are
not clusters, but groups of bright stars probably located in the
Carina-Sagittarius spiral arm. AL 5 and Kronberger 3 are so embedded in a dense
stellar field that we cannot confirm their nature. Trumpler~ 3 and Ruprecht 134
are two intermediate-age open clusters located well inside the solar ring which
deserve further attention. Finally, Collinder 307 is an obscured younger
cluster (250 Myr) located in the Carina-Sagittarius spiral arm. Our results
emphasize the difficulty to search for open clusters in the inner regions of
the Galaxy due to the richness of the field and the patchy nature of the
interstellar absorption, but at the same time significantly contribute to a
better understanding of this complicated regions of the Milky Way.Comment: 11 pages, 16 degraded eps figures, in press in MNRA
The massive star binary fraction in young open clusters - III. IC 2944 and the Cen OB2 association
Using an extended set of multi-epoch high-resolution high signal-to-noise
ratio optical spectra, we readdress the multiplicity properties of the O-type
stars in IC 2944 and in the Cen OB2 association. We present new evidence of
binarity for five objects and we confirm the multiple nature of another two. We
derive the first orbital solutions for HD 100099, HD 101436 and HD 101190 and
we provide additional support for HD 101205 being a quadruple system. The
minimal spectroscopic binary fraction in our sample is f_min = 0.57. Using
numerical simulations, we show that the detection rate of our observational
campaign is close to 90 per cent, leaving thus little room for undetected
spectroscopic binary systems. The statistical properties of the O-star
population in IC 2944 are similar, within the uncertainties, to the results
obtained in the earlier papers in this series despite the fact that sample size
effects limit the significance of the comparison. Using newly derived
spectroscopic parallaxes, we reassess the distance to IC 2944 and obtained
2.3+/-0.3 kpc, in agreement with previous studies. We also confirm that, as far
as the O stars are concerned, the IC 2944 cluster is most likely a single
entity.Comment: 15 pages, 8 Tables, 19 Figure
Investigating the borderline between a young star cluster and a small stellar association: a test case with Bochum1
Usually, a loose stellar distribution can be classified as an OB stellar
group, an association, or a young open cluster. We make use of comparisons with
the typical OB association Vul OB1. In the present paper we discuss the nature
of Bochum 1, a typical example of an object affected by the above
classification problem.The field-decontaminated CMD of Bochum 1 presents main
sequence (MS) and pre-main sequence (PMS) stars. We report two new small
angular-size, compact young clusters and one embedded cluster in the area of
Bochum 1. Vul OB1 harbours the young open cluster NGC 6823 and the very compact
embedded cluster Cr 404. The Vul OB1 association includes the H II region
Sh2-86, and its stellar content is younger ( Myr) than that of Bochum
1 ( Myr), which shows no gas emission. Bochum 1 harbours one of the
newly found compact clusters as its core. The RDP of Bochum 1 is irregular and
cannot be fitted by a King-like profile, which suggests important erosion or
dispersion of stars from a primordial cluster. Similarly to Bochum 1, the
decontaminated CMD of NGC 6823 presents conspicuous MS and PMS sequences. Taken
separately, RDPs of MS and PMS stars follow a King-like profile. The core shows
an important excess density of MS stars that mimics the profile of a post-core
collapse cluster. At such young age, it can be explained by an excess of stars
formed in the prominent core. The present study suggests that Bochum 1 is a
star cluster fossil remain that might be dynamically evolving into an OB
association. Bochum 1 can be a missing link connecting early star cluster
dissolution with the formation of low-mass OB associations.Comment: 13 pages, 13 figures; accepted by A&
Epidemiology of Exertional Rhabdomyolysis Susceptibility in Standardbred Horses Reveals Associated Risk Factors and Underlying Enhanced Performance
BACKGROUND: Exertional rhabdomyolysis syndrome is recognised in many athletic horse breeds and in recent years specific forms of the syndrome have been identified. However, although Standardbred horses are used worldwide for racing, there is a paucity of information about the epidemiological and performance-related aspects of the syndrome in this breed. The objectives of this study therefore were to determine the incidence, risk factors and performance effects of exertional rhabdomyolysis syndrome in Standardbred trotters and to compare the epidemiology and genetics of the syndrome with that in other breeds. METHODOLOGY/PRINCIPAL FINDINGS: A questionnaire-based case-control study (with analysis of online race records) was conducted following identification of horses that were determined susceptible to exertional rhabdomyolysis (based on serum biochemistry) from a total of 683 horses in 22 yards. Thirty six exertional rhabdomyolysis-susceptible horses were subsequently genotyped for the skeletal muscle glycogen synthase (GYS1) mutation responsible for type 1 polysaccharide storage myopathy. A total of 44 susceptible horses was reported, resulting in an annual incidence of 6.4 (95% CI 4.6-8.2%) per 100 horses. Female horses were at significantly greater risk than males (odds ratio 7.1; 95% CI 2.1-23.4; p = 0.001) and nervous horses were at a greater risk than horses with calm or average temperaments (odds ratio 7.9; 95% CI 2.3-27.0; p = 0.001). Rhabdomyolysis-susceptible cases performed better from standstill starts (p = 0.04) than controls and had a higher percentage of wins (p = 0.006). All exertional rhabdomyolysis-susceptible horses tested were negative for the R309H GYS1 mutation. CONCLUSIONS/SIGNIFICANCE: Exertional rhabdomyolysis syndrome in Standardbred horses has a similar incidence and risk factors to the syndrome in Thoroughbred horses. If the disorder has a genetic basis in Standardbreds, improved performance in susceptible animals may be responsible for maintenance of the disorder in the population
Young stars and brown dwarfs surrounding Alnilam (eps Ori) and Mintaka (del Ori)
Aims: We look for new regions for the search of substellar objects. Methods:
Two circular areas, 45 arcmin-radius each, centred on the young massive star
systems Alnilam and Mintaka in the Orion Belt, have been explored. The regions
are very young (less than 10 Ma), have low extinction, and are neighbours to
sigma Orionis (~3 Ma), a young open cluster very rich in brown dwarfs and
planetary-mass objects. We have used Virtual Observatory tools, the
astro-photometric Tycho-2, DENIS and 2MASS catalogues, 10 control fields at
similar galactic latitudes, and X-ray, mid-infrared and spectroscopic data from
the literature. Results: We have compiled exhaustive lists of known young stars
and new candidate members in the Ori OB1b association, and of fore- and
background sources. A total of 136 stars display features of extreme youth,
like early spectral types, lithium in absorption, or mid-infrared flux excess.
Other two young brown dwarf and 289 star candidates have been identified from
an optical/near-infrared colour-magnitude diagram. We list additional 74 known
objects that might belong to the association. This catalogue can serve as an
input for characterisation of the stellar and high-mass substellar populations
in the Orion Belt. Finally, we have investigated the surface densities and
radial distributions of young objects surrounding Alnilam and Mintaka, and
compared them with those in the sigma Orionis cluster. We report a new open
cluster centred on Mintaka. Conclusions: Both regions can be analogs to the
sigma Orionis cluster, but more massive, more extended, slightly older, and
less radially concentrated.Comment: Accepted for publication in A&A. It will be published on line in
Sect. 14 (Catalogs and data). Tables in Appendix A will soon be available at
the CD
Obesity and the food system transformation in Latin America
The Latin America and the Caribbean (LAC) region faces a major diet-related health problem accompanied by enormous economic and social costs. The shifts in diet are profound: major shifts in intake of less-healthful low-nutrient-density foods and sugary beverages, changes in away-from-home eating and snacking and rapid shifts towards very high levels of overweight and obesity among all ages along with, in some countries, high burdens of stunting. Diet changes have occurred in parallel to, and in two-way causality with, changes in the broad food system – the set of supply chains from farms, through midstream segments of processing, wholesale and logistics, to downstream segments of retail and food service (restaurants and fast food chains). An essential contribution of this piece is to marry and integrate the nutrition transition literature with the literature on the economics of food system transformation. These two literatures and debates have been to date largely ‘two ships passing in the night’. This review documents in-depth the recent history of rapid growth and transformation of that broad food system in LAC, with the rapid rise of supermarkets, large processors, fast food chains and food logistics firms. The transformation is the story of a ‘double-edged sword’, showing its links to various negative diet side trends, e.g. the rise of consumption of fast food and highly processed food, as well as in parallel, to various positive trends, e.g. the reduction of the cost of food, de-seasonalization, increase of convenience of food preparation reducing women's time associated with that and increase of availability of some nutritious foods like meat and dairy. We view the transformation of the food system, as well as certain aspects of diet change linked to long-run changes in employment and demographics (e.g. the quest for convenience), as broad parameters that will endure for the next decades without truly major regulatory and fiscal changes. We then focus in on what are the steps that are being and can be taken to curb the negative effects on diet of these changes. We show that countries in LAC are already among the global leaders in initiating demand-related solutions via taxation and marketing controls. But we also show that this is only a small step forward. To shift LAC's food supply towards prices that incentivize consumption of healthier diets and demand away from the less healthy component is not simple and will not happen immediately. We must be cognizant that ultimately, food industry firms must be incentivized to market the components of healthy diets. This will primarily need to be via selective taxes and subsidies, marketing controls, as well as food quality regulations, consumer education and, in the medium term, consumers' desires to combine healthier foods with their ongoing quest for convenience in the face of busy lives. In the end, the food industry in LAC will orient itself towards profitable solutions, ie those demanded by the broad mass of consumers
Groundwater diversion from a deep-rock repository for spent nuclear fuel: Ecohydrological assessment of environmental impacts
Forsmark in Mideastern Sweden is chosen as site for the planned Swedish deep-rock repository for spent nuclear fuel. The construction, operation and decommissioning of the repository require assessments of various types of risks for health and environment on a wide range of temporal scales. This study is focused on the assessment of environmental impacts during the relatively short construction and operation phases, during which the repository will be kept drained by means of groundwater diversion. This diversion may influence hydrogeological and hydrological conditions and thereby cause ecological and other types of consequences in the surroundings of the repository. We here describe methodology and some main findings from the ecohydrological assessment of consequences for aquatic and terrestrial ecosystems in Forsmark. The assessment combines the results of a number of steps, including ecological field inventories and predictive water-flow modelling. The results of the study show that subsurface disposal of radioactive waste is an important application of ecohydrological concepts in assessments of sites with nature values