1,232 research outputs found
The influence of massive stars in the interstellar medium of IC 1613: the supernova remnant S8 and the nebula S3 associated with a WO star
We present a detailed kinematical analysis of two selected nebulae in the
Local Group irregular galaxy IC 1613. The nebulae are: S8, the only known
supernova remnant in this galaxy, and S3, a Wolf-Rayet nebula associated with
the only WO star in this galaxy. For S8, we have obtained and analyzed its
radial velocity field, where we found complex profiles which can be fitted by
several velocity components. These profiles also show the presence of high
velocity, low density gas. From this, we have obtained the expansion velocity,
estimated the preshock density and calculated the basic kinematical parameters
of this SNR. We suggest that in S8 we are seing a SNR partially hidden by dust.
This suggestion comes from the fact that the SNR is located between two
superbubbles where a ridge of obscured material unveils the existence of dust.
Moreover, we show that this hypothesis prevails when energetic arguments are
taken into account. In the case of S3, this nebula shows bipolar structure. By
means of its kinematics, we have analyzed its two lobes, the ``waist'', as well
as its relation with the nearest superbubbles. For the first time we are able
to see closed the NW lobe, showing a clover leaf shape. This fact allows a
better quantitative knowledge of the nebula as a whole. Furthermore, we found
evidence of an expansion motion in the NW lobe. In the light of our results, we
can express that these nebulae are the product of very massive stellar
evolution. It is surprising the influence these stars still have in shaping
their surrounding gas, and on the energy liberation towards the interstellar
medium of this galaxy.Comment: Accepted for publication in the Astronomical Journal, July issue. 11
pages, 12 figures. High resolution figures can be found at
http://www.inaoep.mx/~mago/PAPERS/AJ
The Young Stellar Population of IC1613. I. A New Catalogue of OB Associations
Context: Determining the parameters of massive stars is crucial to understand
many processes in galaxies and the Universe, since these objects are important
sources of ionization, chemical enrichment and momentum. 10m class telescopes
enable us to perform detailed quantitative spectroscopic analyses of massive
stars in other galaxies, sampling areas of different metallicity. Relating the
stars to their environment is crucial to understand the physical processes
ruling their formation and evolution.
Aims: In preparation for the GTC, our goal is to build a catalogue of massive
star candidates in the metal-poor irregular galaxy IC1613 with high astrometric
accuracy, apt for the current generation of multi-object spectrographs. A
census of OB associations in this galaxy is also needed, to provide important
additional information about age and environment of the candidate OB stars.
Methods: From INT-WFC observations, we have built an astrometric and
photometric catalogue of stars in IC1613. Candidate blue massive stars are
preselected from their colors. A friends-of-friends algorithm is developed to
find their clustering in the galaxy. While a common physical origin for all the
members of the associations cannot be ensured, this is a necessary first step
to place candidate OB stars in a population context.
Results: We have produced a deep catalogue of targets in IC1613 that covers a
large field of view. To achieve high astrometric accuracy a new astrometric
procedure is developed for the INT-WFC data. We have also built a catalogue of
OB associations in IC1613. We have found that they concentrate in the central
regions, specially in the HII bubbles. The study of extinction confirms that it
is patchy, with local values of color-excess above the foreground value.Comment: Accepted for publication in Astronomy and Astrophysics. 16 pages +
appendix (14 pages); 20 figure
Kinematics of the ionized gas in the Local Group irregular galaxy IC 1613
We present Halpha and [SII] observations for the Local Group irregular galaxy
IC 1613 using the PUMA scanning Fabry-Perot interferometer. Our goal is to
analyze the kinematics of the ionized gas in the complex sample of superbubbles
located in the whole extension of our field (10 arcmin), which includes most of
the optical emission of this galaxy, and to study the inter-relationship
between young stellar associations and nebulae based on a previous study that
we have made on the stellar associations of the central region of this galaxy.
The ionized gas in this galaxy is distributed in classical HII regions and in a
series of superbubbles (also called giant shells) covering a large fraction of
the optical extent of the galaxy. We present a catalog of kinematical
properties of both the HII regions of this galaxy and the superbubbles. We have
also compared the kinematics of the ionized gas in HII regions to search for
possible dynamic differences between neutral and ionized gas.Comment: 22 pages, 14 figures, 9 Tables. Accepted for publication in A&A Main
Journa
Is HCG31 undergoing a merger or a fly-by interaction?
We present Fabry-Perot and multi-object spectroscopy of the galaxies in
Hickson compact group 31 (HCG31). Based upon our H data cubes, galaxies
A and C are a single entity, showing no discontinuity in their kinematics.
Kinematically, galaxy E is probably a component of the A+C complex; otherwise
it is a recently detached fragment. Galaxy F appears, both kinematically and
chemically, to have formed from material tidally removed from the A+C complex.
Galaxies B and G are kinematically distinct from this complex. Galaxy Q also
has a radial velocity compatible with group membership. Galaxies A, B, C, and F
have nearly identical oxygen abundances, despite spanning a luminosity range of
5mag. Galaxy B's oxygen abundance is normal for its luminosity, while galaxy
F's abundance is that expected given its origin as a tidal fragment of the A+C
complex. The oxygen abundances in galaxies A and C are also understandable if
the A+C complex is a late-type spiral suffering strong gas inflow and star
formation as a result of a tidal interaction. Given the kinematics of both the
galaxies and the \ion{H}{i} gas, the oxygen abundances, and the position of
galaxy G, we propose that an interaction of galaxy G with the A+C complex,
rather than a merger of galaxies A and C, is a more complete explanation for
the tidal features and other properties of HCG31. In this case, the A+C complex
need not be a merger in progress, though this is not ruled out.Comment: accepted for publication by Astronomy & Astrophysic
Monitoring an Alien Invasion: DNA Barcoding and the Identification of Lionfish and Their Prey on Coral Reefs of the Mexican Caribbean
BACKGROUND: In the Mexican Caribbean, the exotic lionfish Pterois volitans has become a species of great concern because of their predatory habits and rapid expansion onto the Mesoamerican coral reef, the second largest continuous reef system in the world. This is the first report of DNA identification of stomach contents of lionfish using the barcode of life reference database (BOLD). METHODOLOGY/PRINCIPAL FINDINGS: We confirm with barcoding that only Pterois volitans is apparently present in the Mexican Caribbean. We analyzed the stomach contents of 157 specimens of P. volitans from various locations in the region. Based on DNA matches in the Barcode of Life Database (BOLD) and GenBank, we identified fishes from five orders, 14 families, 22 genera and 34 species in the stomach contents. The families with the most species represented were Gobiidae and Apogonidae. Some prey taxa are commercially important species. Seven species were new records for the Mexican Caribbean: Apogon mosavi, Coryphopterus venezuelae, C. thrix, C. tortugae, Lythrypnus minimus, Starksia langi and S. ocellata. DNA matches, as well as the presence of intact lionfish in the stomach contents, indicate some degree of cannibalism, a behavior confirmed in this species by the first time. We obtained 45 distinct crustacean prey sequences, from which only 20 taxa could be identified from the BOLD and GenBank databases. The matches were primarily to Decapoda but only a single taxon could be identified to the species level, Euphausia americana. CONCLUSIONS/SIGNIFICANCE: This technique proved to be an efficient and useful method, especially since prey species could be identified from partially-digested remains. The primary limitation is the lack of comprehensive coverage of potential prey species in the region in the BOLD and GenBank databases, especially among invertebrates
A review on probabilistic graphical models in evolutionary computation
Thanks to their inherent properties, probabilistic graphical models are one of the prime candidates for machine learning and decision making tasks especially in uncertain domains. Their capabilities, like representation, inference and learning, if used effectively, can greatly help to build intelligent systems that are able to act accordingly in different problem domains. Evolutionary algorithms is one such discipline that has employed probabilistic graphical models to improve the search for optimal solutions in complex problems. This paper shows how probabilistic graphical models have been used in evolutionary algorithms to improve their performance in solving complex problems. Specifically, we give a survey of probabilistic model building-based evolutionary algorithms, called estimation of distribution algorithms, and compare different methods for probabilistic modeling in these algorithms
Magnetic fields in Local Group dwarf irregulars
We wish to clarify whether strong magnetic fields can be effectively
generated in typically low-mass dwarf galaxies and to assess the role of dwarf
galaxies in the magnetization of the Universe. We performed a search for radio
emission and magnetic fields in an unbiased sample of 12 Local Group (LG)
irregular and dwarf irregular galaxies with the 100m Effelsberg telescope at
2.64 and 4.85GHz. Magnetic fields in LG dwarfs are three times weaker than in
the normal spirals (<4.2+-1.8muG). The production of total magnetic fields
appears to be regulated mainly by the star-formation surface density, with the
power-law exponent of 0.30+-0.04, or by the gas surface density (with the
exponent 0.47+-0.09). In addition, we find systematically stronger fields in
objects of higher global star-formation rate. The dwarf galaxies follow a
similar far-infrared relationship (with a slope of 0.91+-0.08) to that
determined for high surface brightness spiral galaxies. The magnetic field
strength in dwarf galaxies does not correlate with their maximum rotational
velocity, indicating a small-scale rather than a large-scale dynamo process. If
magnetization of the Universe by galactic outflows is coeval with its metal
enrichment, we show that more massive objects (such as Lyman Break Galaxies)
can efficiently magnetize the intergalactic medium with a magnetic field
strength of about 0.8nG out to a distance of 160-530kpc at redshifts 5-3,
respectively. Several times weaker fields and shorter magnetization distances
are expected from primordial dwarf galaxies. We also predict that most
star-forming local dwarfs might have magnetized their surroundings up to about
0.1muG within about 5kpc distance. Strong magnetic fields (>6muG) are observed
only in dwarfs of extreme characteristics while typical LG dwarfs are
unsuitable objects for the efficient supply of magnetic fields to the
intergalactic medium.Comment: Published in Astronomy and Astrophysics, 15 pages, 11 figures, minor
changes to version 1, Fig. 6 changed, discussion of interactions enlarge
Memorias del Séptimo Foro de la Enseñanza de las Matemåticas
En el Séptimo Foro de Enseñanza de las Matemåtica Ibero 2017 se abordaron temas relacionados con el uso de la historia de las matemåticas en el aula, las transformaciones en las habilidades, destrezas y conocimientos en los alumnos universitarios en la primera década del 2000, el uso de plataformas digitales en la enseñanza de las matemåticas; se expuso sobre situaciones problema en la vida cotidiana relacionados con las matemåticas escolares y la modelación matemåtica, sobre la historia de la enseñanza de las matermåticas, entre otros temas.ITESO, A.C.Universidad Iberoamericana, Campus Santa F
Global, regional, and national burden of osteoarthritis, 1990â2020 and projections to 2050: a systematic analysis for the Global Burden of Disease Study 2021
Background
Osteoarthritis is the most common form of arthritis in adults, characterised by chronic pain and loss of mobility. Osteoarthritis most frequently occurs after age 40 years and prevalence increases steeply with age. WHO has designated 2021â30 the decade of healthy ageing, which highlights the need to address diseases such as osteoarthritis, which strongly affect functional ability and quality of life. Osteoarthritis can coexist with, and negatively effect, other chronic conditions. Here we estimate the burden of hand, hip, knee, and other sites of osteoarthritis across geographies, age, sex, and time, with forecasts of prevalence to 2050.
Methods
In this systematic analysis for the Global Burden of Disease Study, osteoarthritis prevalence in 204 countries and territories from 1990 to 2020 was estimated using data from population-based surveys from 26 countries for knee osteoarthritis, 23 countries for hip osteoarthritis, 42 countries for hand osteoarthritis, and US insurance claims for all of the osteoarthritis sites, including the other types of osteoarthritis category. The reference case definition was symptomatic, radiographically confirmed osteoarthritis. Studies using alternative definitions from the reference case definition (for example self-reported osteoarthritis) were adjusted to reference using regression models. Osteoarthritis severity distribution was obtained from a pooled meta-analysis of sources using the Western Ontario and McMaster Universities Arthritis Index. Final prevalence estimates were multiplied by disability weights to calculate years lived with disability (YLDs). Prevalence was forecast to 2050 using a mixed-effects model.
Findings
Globally, 595 million (95% uncertainty interval 535â656) people had osteoarthritis in 2020, equal to 7·6% (95% UI 6·8â8·4) of the global population, and an increase of 132·2% (130·3â134·1) in total cases since 1990. Compared with 2020, cases of osteoarthritis are projected to increase 74·9% (59·4â89·9) for knee, 48·6% (35·9â67·1) for hand, 78·6% (57·7â105·3) for hip, and 95·1% (68·1â135·0) for other types of osteoarthritis by 2050. The global age-standardised rate of YLDs for total osteoarthritis was 255·0 YLDs (119·7â557·2) per 100â000 in 2020, a 9·5% (8·6â10·1) increase from 1990 (233·0 YLDs per 100â000, 109·3â510·8). For adults aged 70 years and older, osteoarthritis was the seventh ranked cause of YLDs. Age-standardised prevalence in 2020 was more than 5·5% in all world regions, ranging from 5677·4 (5029·8â6318·1) per 100â000 in southeast Asia to 8632·7 (7852·0â9469·1) per 100â000 in high-income Asia Pacific. Knee was the most common site for osteoarthritis. High BMI contributed to 20·4% (95% UI â1·7 to 36·6) of osteoarthritis. Potentially modifiable risk factors for osteoarthritis such as recreational injury prevention and occupational hazards have not yet been explored in GBD modelling.
Interpretation
Age-standardised YLDs attributable to osteoarthritis are continuing to rise and will lead to substantial increases in case numbers because of population growth and ageing, and because there is no effective cure for osteoarthritis. The demand on health systems for care of patients with osteoarthritis, including joint replacements, which are highly effective for late stage osteoarthritis in hips and knees, will rise in all regions, but might be out of reach and lead to further health inequity for individuals and countries unable to afford them. Much more can and should be done to prevent people getting to that late stage
Search for a vector-like quark TâČ â tH via the diphoton decay mode of the Higgs boson in proton-proton collisions at = 13 TeV
A search for the electroweak production of a vector-like quark TâČ, decaying to a top quark and a Higgs boson is presented. The search is based on a sample of proton-proton collision events recorded at the LHC at = 13 TeV, corresponding to an integrated luminosity of 138 fbâ1. This is the first TâČ search that exploits the Higgs boson decay to a pair of photons. For narrow isospin singlet TâČ states with masses up to 1.1 TeV, the excellent diphoton invariant mass resolution of 1â2% results in an increased sensitivity compared to previous searches based on the same production mechanism. The electroweak production of a TâČ quark with mass up to 960 GeV is excluded at 95% confidence level, assuming a coupling strength ÎșT = 0.25 and a relative decay width Î/MTâČ < 5%
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