133 research outputs found
The edge of the young Galactic disc
In this work we report and discuss the detection of two distant diffuse
stellar groups in the third Galactic quadrant. They are composed of young
stars, with spectral types ranging from late O to late B, and lie at
galactocentric distances between 15 and 20 kpc. These groups are located in the
area of two cataloged open clusters (VdB-Hagen~04 and Ruprecht~30), projected
towards the Vela-Puppis constellations, and within the core of the Canis Major
over-density. Their reddening and distance has been estimated analyzing their
color-color and color-magnitude diagrams, derived from deep photometry.
The existence of young star aggregates at such extreme distances from the
Galactic center challenges the commonly accepted scenario in which the Galactic
disc has a sharp cut-off at about 14 kpc from the Galactic center, and
indicates that it extends to much greater distances (as also supported by
recent detection of CO molecular complexes well beyond this distance). While
the groups we find in the area of Ruprecht~30 are compatible with the Orion and
Norma-Cygnus spiral arms, respectively, the distant group we identify in the
region of VdB-Hagen~4 lies in the external regions of the Norma-Cygnus arm, at
a galactocentric distance (20 kpc) where no young stars had been detected
so far in the optical.Comment: 45 pages, 11 eps figure, accepted for publication in the
Astrophysical Journa
Photometry of a Galactic field at l = 232, b = -6. The old open cluster Auner 1, the Norma-Cygnus spiral arm and the signature of the warped Galactic Thick Disk
We perform a detailed photometric study of the stellar populations in a
Galactic Field at l = 232, b = -6 in the Canis Major (CMa) constellation. We
present the first U,B,V,I photometry of the old open cluster Auner1 and
determine it to be 3.25 Gyr old and to lie at 8.9 kpc from the Sun. In the
background of the cluster, at more than 9 kpc, we detect a young population
most probably associated to the Norma Cygnus spiral arm. Furthermore, we detect
the signature of an older population and identify its Turn Off and Red Giant
Branch. This population is found to have a mean age of 7 Gyrs and a mean
metallicity of Z = 0.006 . We reconstruct the geometry of the stellar
distribution and argue that this older population - often associated to the
Canis Major {\it galaxy}- belongs in fact to the warped old thin/thick disk
component along this line of sight.Comment: 19 pages, 7 eps figures (some degraded), accepted for publication in
the Astronomical Journa
Stellar populations in the Canis Major over-density
We performed a photometric multicolor survey of the core of the Canis Major
over-density at l 244, -8.0, reaching V = 22 and covering 0.3 x 1 degree. The
main aim is to unravel the complex mixture of stellar populations toward this
Galactic direction, where in the recent past important signatures of an
accretion event have been claimed to be detected. While our previous
investigations were based on disjointed pointings aimed at revealing the large
scale structure of the third Galactic Quadrant, we now focus on a complete
coverage of a smaller field centered on the Canis Major over-density. A large
wave-length baseline, in the UBVRI bands, allows us to build up a suite of
colour colour and colour magnitude diagrams, providing a much better diagnostic
tool to disentangle the stellar populations of the region. In fact, the simple
use of one colour magnitude diagram, widely employed in all the previous
studies defending the existence of the Canis Major galaxy, does not allow one
to separate the effects of the different parameters (reddening, age,
metallicity, and distance) involved in the interpretation of data, forcing to
rely on heavy modeling. In agreement with our previous studies in the same
general region of the Milky Way, we recognize a young stellar population
compatible with the expected structure and extension of the Local (Orion) and
Outer (Norma-Cygnus) spiral arms in the Third Galactic Quadrant. Moreover we
interpret the conspicuous intermediate-age metal poor population as belonging
to the Galactic thick disk, distorted by the effect of strong disk warping at
this latitude, and to the Galactic halo.Comment: 9 pages, 12 eps figures (some of them somewhat degraded in
resolution), accepted for publication in MNRA
CaracterizaciĂłn del secretoma asociado a metĂĄstasis de cĂĄncer colorrectal mediante SILAC utilizando el sistema celular KM12
Comunicaciones a congreso
Whole-Brain Structural Connectivity in Dyskinetic Cerebral Palsy and Its Association With Motor and Cognitive Function
Dyskinetic cerebral palsy (CP) has long been associated with basal ganglia and thalamus lesions. Recent evidence further points at white matter (WM) damage. This study aims to identify altered WM pathways in dyskinetic CP from a standardized, connectome-based approach, and to assess structure-function relationship in WM pathways for clinical outcomes. Individual connectome maps of 25 subjects with dyskinetic CP and 24 healthy controls were obtained combining a structural parcellation scheme with whole-brain deterministic tractography. Graph theoretical metrics and the network-based statistic were applied to compare groups and to correlate WM state with motor and cognitive performance. Results showed a widespread reduction of WM volume in CP subjects compared to controls and a more localized decrease in degree (number of links per node) and fractional anisotropy (FA), comprising parieto-occipital regions and the hippocampus. However, supramarginal gyrus showed a significantly higher degree. At the network level, CP subjects showed a bilateral pathway with reduced FA, comprising sensorimotor, intraparietal and fronto-parietal connections. Gross and fine motor functions correlated with FA in a pathway comprising the sensorimotor system, but gross motor also correlated with prefrontal, temporal and occipital connections. Intelligence correlated with FA in a network with fronto-striatal and parieto-frontal connections, and visuoperception was related to right occipital connections. These findings demonstrate a disruption in structural brain connectivity in dyskinetic CP, revealing general involvement of posterior brain regions with relative preservation of prefrontal areas. We identified pathways in which WM integrity is related to clinical features, including but not limited to the sensorimotor system
Measurement of the cosmic ray spectrum above eV using inclined events detected with the Pierre Auger Observatory
A measurement of the cosmic-ray spectrum for energies exceeding
eV is presented, which is based on the analysis of showers
with zenith angles greater than detected with the Pierre Auger
Observatory between 1 January 2004 and 31 December 2013. The measured spectrum
confirms a flux suppression at the highest energies. Above
eV, the "ankle", the flux can be described by a power law with
index followed by
a smooth suppression region. For the energy () at which the
spectral flux has fallen to one-half of its extrapolated value in the absence
of suppression, we find
eV.Comment: Replaced with published version. Added journal reference and DO
Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory
The Auger Engineering Radio Array (AERA) is part of the Pierre Auger
Observatory and is used to detect the radio emission of cosmic-ray air showers.
These observations are compared to the data of the surface detector stations of
the Observatory, which provide well-calibrated information on the cosmic-ray
energies and arrival directions. The response of the radio stations in the 30
to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of
the incoming electric field. For the latter, the energy deposit per area is
determined from the radio pulses at each observer position and is interpolated
using a two-dimensional function that takes into account signal asymmetries due
to interference between the geomagnetic and charge-excess emission components.
The spatial integral over the signal distribution gives a direct measurement of
the energy transferred from the primary cosmic ray into radio emission in the
AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air
shower arriving perpendicularly to the geomagnetic field. This radiation energy
-- corrected for geometrical effects -- is used as a cosmic-ray energy
estimator. Performing an absolute energy calibration against the
surface-detector information, we observe that this radio-energy estimator
scales quadratically with the cosmic-ray energy as expected for coherent
emission. We find an energy resolution of the radio reconstruction of 22% for
the data set and 17% for a high-quality subset containing only events with at
least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO
Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy
We measure the energy emitted by extensive air showers in the form of radio
emission in the frequency range from 30 to 80 MHz. Exploiting the accurate
energy scale of the Pierre Auger Observatory, we obtain a radiation energy of
15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV
arriving perpendicularly to a geomagnetic field of 0.24 G, scaling
quadratically with the cosmic-ray energy. A comparison with predictions from
state-of-the-art first-principle calculations shows agreement with our
measurement. The radiation energy provides direct access to the calorimetric
energy in the electromagnetic cascade of extensive air showers. Comparison with
our result thus allows the direct calibration of any cosmic-ray radio detector
against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI.
Supplemental material in the ancillary file
Large-scale analysis of structural brain asymmetries in schizophrenia via the ENIGMA consortium
Left-right asymmetry is an important organizing feature of the healthy brain that may be altered in schizophrenia, but most studies have used relatively small samples and heterogeneous approaches, resulting in equivocal findings. We carried out the largest case-control study of structural brain asymmetries in schizophrenia, using MRI data from 5,080 affected individuals and 6,015 controls across 46 datasets in the ENIGMA consortium, using a single image analysis protocol. Asymmetry indexes were calculated for global and regional cortical thickness, surface area, and subcortical volume measures. Differences of asymmetry were calculated between affected individuals and controls per dataset, and effect sizes were meta-analyzed across datasets. Small average case-control differences were observed for thickness asymmetries of the rostral anterior cingulate and the middle temporal gyrus, both driven by thinner left-hemispheric cortices in schizophrenia. Analyses of these asymmetries with respect to the use of antipsychotic medication and other clinical variables did not show any significant associations. Assessment of age- and sex-specific effects revealed a stronger average leftward asymmetry of pallidum volume between older cases and controls. Case-control differences in a multivariate context were assessed in a subset of the data (N = 2,029), which revealed that 7% of the variance across all structural asymmetries was explained by case-control status. Subtle case-control differences of brain macro-structural asymmetry may reflect differences at the molecular, cytoarchitectonic or circuit levels that have functional relevance for the disorder. Reduced left middle temporal cortical thickness is consistent with altered left-hemisphere language network organization in schizophrenia
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