241 research outputs found
A catalogue of open cluster radii determined from Gaia proper motions
In this work we improve a previously published method to calculate in a
reliable way the radius of an open cluster. The method is based on the
behaviour of stars in the proper motion space as the sampling changes in the
position space. Here we describe the new version of the method and show its
performance and robustness. Additionally, we apply it to a large number of open
clusters using data from Gaia DR2 to generate a catalogue of 401 clusters with
reliable radius estimations. The range of obtained apparent radii goes from
Rc=1.4+-0.1 arcmin (for the cluster FSR 1651) to Rc=25.5+-3.5 arcmin (for
NGC~2437). Cluster linear sizes follow very closely a lognormal distribution
with a mean characteristic radius of Rc=3.7 pc, and its high radius tail can be
fitted by a power law as N \propto Rc^(-3.11+-0.35). Additionally, we find that
number of members, cluster radius and age follow the relationship Nc \propto
Rc^(1.2+-0.1) Tc^(-1.9+-0.4) where the younger and more extensive the cluster,
the more members it presents. The proposed method is not sensitive to low
density or irregular spatial distributions of stars and, therefore, is a good
alternative or complementary procedure to calculate open cluster radii not
having previous information on star memberships.Comment: 13 pages including 9 figures and 2 tables (main table will be
available online). Accepted for publication in MNRA
A method for determining the radius of an open cluster from stellar proper motions
We propose a method for calculating the radius of an open cluster in an
objective way from an astrometric catalogue containing, at least, positions and
proper motions. It uses the minimum spanning tree (hereinafter MST) in the
proper motion space to discriminate cluster stars from field stars and it
quantifies the strength of the cluster-field separation by means of a
statistical parameter defined for the first time in this paper. This is done
for a range of different sampling radii from where the cluster radius is
obtained as the size at which the best cluster-field separation is achieved.
The novelty of this strategy is that the cluster radius is obtained
independently of how its stars are spatially distributed. We test the
reliability and robustness of the method with both simulated and real data from
a well-studied open cluster (NGC 188), and apply it to UCAC4 data for five
other open clusters with different catalogued radius values. NGC 188, NGC 1647,
NGC 6603 and Ruprecht 155 yielded unambiguous radius values of 15.2+/-1.8,
29.4+/-3.4, 4.2+/-1.7 and 7.0+/-0.3 arcmin, respectively. ASCC 19 and Collinder
471 showed more than one possible solution but it is not possible to know
whether this is due to the involved uncertainties or to the presence of complex
patterns in their proper motion distributions, something that could be inherent
to the physical object or due to the way in which the catalogue was sampled.Comment: 12 pages including 14 figures and 1 table. Accepted for publication
in MNRA
Constraints to the magnetospheric properties of T Tauri stars - II. The Mg II ultraviolet feature
The atmospheric structure of T Tauri Stars (TTSs) and its connection with the
large scale outflow is poorly known. Neither the effect of the magnetically
mediated inter- action between the star and the disc in the stellar atmosphere
is well understood. The Mg II multiplet is a fundamental tracer of TTSs
atmospheres and outflows, and is the strongest feature in the near-ultraviolet
spectrum of TTSs. The International Ultraviolet Explorer and Hubble Space
Telescope data archives provide a unique set to study the main physical
compounds contributing to the line profile and to derive the properties of the
line formation region. The Mg II profiles of 44 TTSs with resolution 13,000 to
30,000 are available in these archives. In this work, we use this data set to
measure the main observables: flux, broadening, asymmetry, terminal velocity of
the outflow, and the velocity of the Discrete Absorption Components. For some
few sources repeated observations are available and variability has been
studied. There is a warm wind that at sub-AU scales absorbs the blue wing of
the Mg II profiles. The main result found in this work is the correlation
between the line broadening, Mg II flux, terminal velocity of the flow and
accretion rate. Both outflow and magnetospheric plasma contribute to the Mg II
flux. The flux-flux correlation between Mg II and C IV or He II is confirmed;
however, no correlation is found between the Mg II flux and the ultraviolet
continuum or the H2 emission.Comment: 21 pages, 20 figure
Constraints to the magnetospheric properties of T Tauri stars. I. The C II], Fe II] and Si II] ultraviolet features
The C II] feature at ~2325 Angstrom is very prominent in the spectra of T
Tauri stars (TTSs). This feature is a quintuplet of semiforbidden transitions
excited at electron temperatures around 10,000 K that, together with the nearby
Si II] and Fe II] features, provides a reliable optically thin tracer for
accurate measurement of the plasma properties in the magnetospheres of TTSs.
The spectra of 20 (out of 27) TTSs observed with the Space Telescope Imaging
Spectrograph (STIS) on board the Hubble Space Telescope (HST) have good enough
signal to noise ratio (S/N) at the C II] wavelength. For these stars we have
determined electron densities (ne) and temperatures (Te) in the line emission
region as well as the profile broadening (sigma). For most of the stars in the
sample (17) we obtain 10^{4.1} < Te < 10^{4.5} K and 10^{8} < ne < 10^{12}
cm^{-3}. These stars have suprathermal line broadening (35 < sigma < 165 km
s^{-1}), except TW Hya and CY Tau with thermal line broadening. Both C II] line
luminosity and broadening are found to correlate with the accretion rate. Line
emission seems to be produced in the magnetospheric accretion flow, close to
the disk. There are three exceptions: DG Tau, RY Tau and FU Ori. The line
centroids are blueshifted indicating that the line emission in these three
stars is dominated by the outflow.Comment: 13 pages, 15 figures, published in MNRAS minor change
Variation of the ultraviolet extinction law across the Taurus-Auriga star forming complex. A GALEX based study
The Taurus-Auriga molecular complex (TMC) is the main laboratory for the
study of low mass star formation. The density and properties of interstellar
dust are expected to vary across the TMC. These variations trace important
processes such as dust nucleation or the magnetic field coupling with the
cloud. In this article, we show how the combination of near ultraviolet (NUV)
and infrared (IR) photometry can be used to derive the strength of the 2175
\AA\ bump and thus any enhancement in the abundance of small dust grains and
PAHs in the dust grains size distribution. This technique is applied to the
envelope of the TMC, mapped by the GALEX All Sky Survey (AIS). UV and IR
photometric data have been retrieved from the GALEX-AIS and the 2MASS
catalogues. NUV and K-band star counts have been used to identify the areas in
the cloud envelope where the 2175 \AA\ bump is weaker than in the diffuse ISM
namely, the low column density extensions of L1495, L1498 and L1524 in Taurus,
L1545, L1548, L1519, L1513 in Auriga and L1482-83 in the California region.
This finding agrees with previous results on dust evolution derived from
Spitzer data and suggests that dust grains begin to decouple from the
environmental galactic magnetic field already in the envelope.Comment: Accepted in Monthly Notices of the Royal Astronomical Societ
Different prognostic impact of recurrent gene mutations in chronic lymphocytic leukemia depending on IGHV gene somatic hypermutation status: a study by ERIC in HARMONY
Recent evidence suggests that the prognostic impact of gene mutations in patients with chronic lymphocytic leukemia (CLL) may differ depending on the immunoglobulin heavy variable (IGHV) gene somatic hypermutation (SHM) status. In this study, we assessed the impact of nine recurrently mutated genes (BIRC3, EGR2, MYD88, NFKBIE, NOTCH1, POT1, SF3B1, TP53, and XPO1) in pre-treatment samples from 4580 patients with CLL, using time-to-first-treatment (TTFT) as the primary end-point in relation to IGHV gene SHM status. Mutations were detected in 1588 (34.7%) patients at frequencies ranging from 2.3-9.8% with mutations in NOTCH1 being the most frequent. In both univariate and multivariate analyses, mutations in all genes except MYD88 were associated with a significantly shorter TTFT. In multivariate analysis of Binet stage A patients, performed separately for IGHV-mutated (M-CLL) and unmutated CLL (U-CLL), a different spectrum of gene alterations independently predicted short TTFT within the two subgroups. While SF3B1 and XPO1 mutations were independent prognostic variables in both U-CLL and M-CLL, TP53, BIRC3 and EGR2 aberrations were significant predictors only in U-CLL, and NOTCH1 and NFKBIE only in M-CLL. Our findings underscore the need for a compartmentalized approach to identify high-risk patients, particularly among M-CLL patients, with potential implications for stratified management
Towards precision medicine: defining and characterizing adipose tissue dysfunction to identify early immunometabolic risk in symptom-free adults from the GEMM family study
Interactions between macrophages and adipocytes are early molecular factors influencing adipose tissue (AT) dysfunction, resulting in high leptin, low adiponectin circulating levels and low-grade metaflammation, leading to insulin resistance (IR) with increased cardiovascular risk. We report the characterization of AT dysfunction through measurements of the adiponectin/leptin ratio (ALR), the adipo-insulin resistance index (Adipo-IRi), fasting/postprandial (F/P) immunometabolic phenotyping and direct F/P differential gene expression in AT biopsies obtained from symptom-free adults from the GEMM family study. AT dysfunction was evaluated through associations of the ALR with F/P insulin-glucose axis, lipid-lipoprotein metabolism, and inflammatory markers. A relevant pattern of negative associations between decreased ALR and markers of systemic low-grade metaflammation, HOMA, and postprandial cardiovascular risk hyperinsulinemic, triglyceride and GLP-1 curves was found. We also analysed their plasma non-coding microRNAs and shotgun lipidomics profiles finding trends that may reflect a pattern of adipose tissue dysfunction in the fed and fasted state. Direct gene differential expression data showed initial patterns of AT molecular signatures of key immunometabolic genes involved in AT expansion, angiogenic remodelling and immune cell migration. These data reinforce the central, early role of AT dysfunction at the molecular and systemic level in the pathogenesis of IR and immunometabolic disorders
Las ciencias sociales y sus abordajes en los estudios avanzados
Este libro tiene como uno de sus objetivos principales impulsar un ejercicio académico de tipo interdisciplinario entre investigadores y egresados del programa de Doctorado en Ciencias Sociales de la Universidad Autónoma del Estado México (UAEM). Si bien se trata de un esfuerzo incipiente porque los autores que escriben, presentan artículos de investigación en los que desarrollan temas de su campo disciplinar, se trata de un libro relevante porque inaugura una actividad editorial que involucraría a profesores y estudiantes de diferentes líneas de investigación y de distintas disciplinas y les daría la posibilidad de interactuar intelectualmente con el fin de consolidar un diálogo interdisciplinario, que seguramente hará posible desarrollar discusiones de tipo interdisciplinar sobre problemas concretos.Este libro tiene como uno de sus objetivos principales impulsar un ejercicio académico de tipo interdisciplinario entre investigadores y egresados del programa de Doctorado en Ciencias Sociales de la Universidad Autónoma del Estado México (uaem).1 Si bien se trata de un esfuerzo incipiente porque los autores que escriben, presentan artículos de investigación en los que desarrollan temas de su campo disciplinar, se trata de un libro relevante porque inaugura una actividad editorial que involucraría a profesores y estudiantes de diferentes líneas de investigación y de distintas disciplinas y les daría la posibilidad de interactuar intelectualmente con el fin de consolidar un diálogo interdisciplinario,UAE
Expansion of Signal Transduction Pathways in Fungi by Extensive Genome Duplication
International audienceno abstrac
Association between solar insolation and a history of suicide attempts in bipolar I disorder
In many international studies, rates of completed suicide and suicide attempts have a seasonal pattern that peaks in spring or summer. This exploratory study investigated the association between solar insolation and a history of suicide attempt in patients with bipolar I disorder. Solar insolation is the amount of electromagnetic energy from the Sun striking a surface area on Earth. Data were collected previously from 5536 patients with bipolar I disorder at 50 collection sites in 32 countries at a wide range of latitudes in both hemispheres. Suicide related data were available for 3365 patients from 310 onset locations in 51 countries. 1047 (31.1%) had a history of suicide attempt. There was a significant inverse association between a history of suicide attempt and the ratio of mean winter solar insolation/mean summer solar insolation. This ratio is smallest near the poles where the winter insolation is very small compared to the summer insolation. This ratio is largest near the equator where there is relatively little variation in the insolation over the year. Other variables in the model that were positively associated with suicide attempt were being female, a history of alcohol or substance abuse, and being in a younger birth cohort. Living in a country with a state-sponsored religion decreased the association. (All estimated coefficients p <0.01). In summary, living in locations with large changes in solar insolation between winter and summer may be associated with increased suicide attempts in patients with bipolar disorder. Further investigation of the impacts of solar insolation on the course of bipolar disorder is needed.Peer reviewe
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