162 research outputs found
Imaging review of the lung parenchymal complications in patients with IPF
Idiopathic pulmonary fibrosis (IPF) is a chronic, pulmonary-limited, interstitial lung disease with a poor prognosis. This condition is characterized by different clinical scenarios, ranging from the most typical slow and progressive deterioration of symptoms to a rapid and abrupt decline of lung function. Rapid worsening of clinical course is due to superimposed complications and comorbidities that can develop in IPF patients, with a higher incidence rate compared to the general population. These conditions may require a different management of the patient and a therapy adjustment, and thus it is fundamental to recognize them. High Resolution Computed Tomography (HRCT) is sensitive, but not specific, in detecting these complications, and can evaluate the presence of radiological variations when previous examinations are available; it recognizes ground glass opacities or consolidation that can be related to a large spectrum of comorbidities, such as infection, lung cancer, or acute exacerbation. To reach the final diagnosis, a multidisciplinary discussion is required, particularly when the clinical context is related to imaging findings
One Star to Tag Them All (OSTTA): I. Radial velocities and chemical abundances for 20 poorly studied open clusters
Context: Open clusters are ideal laboratories to investigate a variety of
astrophysical topics, from the properties of the Galactic disc to stellar
evolution models. For this purpose, we need to know their chemical composition
in detail. Unfortunately, the number of systems with chemical abundances
determined from high resolution spectroscopy remains small. Aims: Our aim is to
increase the number of open clusters with radial velocities and chemical
abundances determined from high resolution spectroscopy by sampling a few stars
in clusters not studied previously. Methods: We obtained high resolution
spectra with the FIES spectrograph at NOT for 41 stars belonging to 20 open
clusters. These stars have high astrometric membership probabilities,
determined from the Gaia second data release. Results: We derived radial
velocities for all the observed stars, which were used to confirm their
membership to the corresponding clusters. For Gulliver\,37 we cannot be sure
the observed star is a real member. We derived atmospheric parameters for the
32 stars considered real cluster members. We discarded five stars because they
have very low gravity or atmospheric parameters were not properly constrained
due to low signal-to-noise ratio spectra. Therefore, detailed chemical
abundances were determined for 28 stars belonging to 17 clusters. For most of
them, this is the first chemical analysis available in the literature. Finally,
we compared the clusters in our sample to a large population of well studied
clusters. The studied systems follow the trends, both chemical and kinematical,
described by the majority of open clusters. Worth noticing that the three most
metal-poor studied clusters (NGC\,1027, NGC\,1750 and Trumpler 2) are enhanced
in Si but not in the other alpha-elements studied (Mg, Ca and Ti).Comment: 19 pages Accepted for publication on A&
Compact Modeling of Nonideal Trapping/Detrapping Processes in GaN Power Devices
Compact modeling of charge trapping processes in GaN transistors is of fundamental importance for advanced circuit design. The goal of this article is to propose a methodology for modeling the dynamic characteristics of GaN power HEMTs in the realistic case where trapping/detrapping kinetics are described by stretched exponentials, contrary to ideal pure exponentials, thus significantly improving the state of the art. The analysis is based on: 1) an accurate methodology for describing stretched-exponential transients and extracting the related parameters and 2) a novel compact modeling approach, where the stretched exponential behavior is reproduced via multiple RC networks, whose parameters are specifically tuned based on the results of 1). The developed compact model is then used to simulate the transient performance of the HEMT devices as a function of duty cycle and frequency, thus providing insight on the impact of traps during the realistic switching operatio
溜池地帯における共同田植と水利 : 兵庫県多紀郡沢田部落における事例的研究
textabstractClimbing fibers (CFs) originating in the inferior olive (IO) constitute one of the main inputs to the cerebellum. In the mammalian cerebellar cortex each of them climbs into the dendritic tree of up to ten Purkinje cells where they make hundreds of synaptic contacts and elicit the socalled all-or-none complex spikes controlling the output. While it has been proven that CFs contact molecular layer interneurons (MLIs) via spillover mechanisms, it remains to be elucidated to what extent CFs contact the main type of interneuron in the granular layer, i.e. the Golgi cells (GoCs). This issue is particularly relevant, because direct contacts would imply that CFs can also control computations at the input stage of the cerebellar cortical network. Here, we performed a systematic morphological investigation of labeled CFs and GoCs at the light microscopic level following their path and localization through the neuropil in both the granular and molecular layer. Whereas the appositions of CFs to Purkinje cells, stellate cells and basket cells in the molecular layer were prominent and numerous, those to cell-bodies and dendrites of GoCs in both the granular layer and molecular layer were virtually absent. Our results argue against the functional significance of direct synaptic contacts between CFs and interneurons at the input stage, but support those at the output stage
The GAPS Programme at TNG -- XXV. Stellar atmospheric parameters and chemical composition through GIARPS optical and near-infrared spectra
The detailed chemical composition of stars is important in many astrophysical
fields, among which the characterisation of exoplanetary systems. Previous
studies seem to indicate an anomalous chemical pattern of the youngest stellar
population in the solar vicinity with a sub-solar metal content. This can
influence various observational relations linking the properties of exoplanets
to the characteristics of the host stars, for example the giant
planet-metallicity relation. In this framework, we aim to expand our knowledge
of the chemical composition of intermediate-age stars and understand whether
these peculiarities are real or related to spectroscopic analysis techniques.
We analysed high-resolution optical and near-infrared GIARPS spectra of
intermediate-age stars (< 700Myr). To overcome issues related to the young ages
of the stars, we applied a new spectroscopic method that uses titanium lines to
derive the atmospheric parameters, in particular surface gravities and
microturbulence velocity parameter. We also derived abundances of 14 different
atomic species. The lack of systematic trends between elemental abundances and
effective temperatures validates our method. However, we observed that the
coolest (<5400 K) stars in the sample, display higher abundances for the Cr II,
and for high-excitation potential C I lines. We found a positive correlation
between the higher abundances measured of C I and Cr II and the activity index
logR. Instead, we found no correlations between the C abundances
obtained from CH molecular band at 4300\AA, and both effective temperatures and
activity. Thus, we suggest that these are better estimates for C abundances in
young and cool stars. Finally, we found an indication of an increasing
abundance ratio [X/H] with the condensation temperature for HD167389,
indicating possible episodes of planet engulfment.Comment: 18 pages, 9 figures, accepted for publication in A&
The Gaia-ESO survey: mapping the shape and evolution of the radial abundance gradients with open clusters
The spatial distribution of elemental abundances and their time evolution are
among the major constraints to disentangle the scenarios of formation and
evolution of the Galaxy. We used the sample of open clusters available in the
final release of the Gaia-ESO survey to trace the Galactic radial abundance and
abundance to iron ratio gradients, and their time evolution. We selected member
stars in 62 open clusters, with ages from 0.1 to about 7~Gyr, located in the
Galactic thin disc at Galactocentric radii from about 6 to 21~kpc. We analysed
the shape of the resulting [Fe/H] gradient, the average gradients [El/H] and
[El/Fe] combining elements belonging to four different nucleosynthesis
channels, and their individual abundance and abundance ratio gradients. We also
investigated the time evolution of the gradients dividing open clusters in
three age bins. The[Fe/H] gradient has a slope of -0.054 dex~kpc-1. We saw
different behaviours for elements belonging to different channels. We found
that the youngest clusters in the inner disc have lower metallicity than their
older counterpart and they outline a flatter gradient. We considered some
possible explanations, including the effects of gas inflow and migration. We
suggested that it might be a bias introduced by the standard spectroscopic
analysis producing lower metallicities in low gravity stars. To delineate the
shape of the `true' gradient, we should limit our analysis to stars with low
surface gravity logg>2.5 and xi<1.8 km~s-1. Based on this reduced sample, we
can conclude that the gradient has minimally evolved over the time-frame
outlined by the open clusters, indicating a slow and stationary formation of
the thin disc in the latest Gyr. We found a secondary role of clusters'
migration in shaping the gradient, with a more prominent role of migration for
the oldest clusters.Comment: 25 pages, 14 figures and 4 tables in the main text, 3 figures and 7
tables in the Appendix. Accepted for publication in A&
HADES RV Programme with HARPS-N at TNG XII. The abundance signature of M dwarf stars with planets
Most of our current knowledge on planet formation is still based on the
analysis of main-sequence, solar-type stars. Conversely, detailed chemical
studies of large samples of M-dwarf planet hosts are still missing. We develop
for the first time a methodology to determine stellar abundances of elements
others than iron for M dwarf stars from high-resolution, optical spectra. Our
methodology is based on the use of principal component analysis and sparse
Bayesian's methods. We made use of a set of M dwarfs orbiting around an FGK
primary with known abundances to train our methods. We applied our methods to
derive stellar metalliticies and abundances of a large sample of M dwarfs
observed within the framework of current radial velocity surveys. We then used
a sample of nearby FGK stars to cross-validate our technique by comparing the
derived abundance trends in the M dwarf sample with those found on the FGK
stars. The metallicity distribution of the different subsamples shows that M
dwarfs hosting giant planets show a planet-metallicity correlation as well as a
correlation with the stellar mass. M dwarfs hosting low-mass planets do not
seem to follow the planet-metallicity correlation. We also found that the
frequency of low-mass planets does not depend on the mass of the stellar host.
These results seem in agreement with previous works. However, we note that for
giant planet hosts our metallicities predict a weaker planet metallicity
correlation but a stronger mass-dependency than photometric values. We show,
for the first time, that there seems to be no differences in the abundance
distribution of elements different from iron between M dwarfs with and without
known planets. Our data shows that low-mass stars with planets follow the same
metallicity, mass, and abundance trends than their FGK counterparts.Comment: Accepted for publication by Astronomy & Astrophysic
OP0063 QUANTITATIVE COMPUTED TOMOGRAPHY PREDICTS 10-YEAR MORTALITY IN INTERSTITIAL LUNG DISEASE RELATED TO SYSTEMIC SCLEROSI
Background:
Interstitial lung disease (ILD) is the main cause of death in Systemic Sclerosis (SSc). Chest CT is the gold standard in detecting ILD although it is not easy to understand its prognostic value. ILD qualitative assessment is almost worthless. Goh et al. semi quantitative score of ILD extent is related to mortality risk but it is burdened by relevant inter/intra-readers variability. An operator independent algorithm based on voxel-wise analysis proved to identify SSc patients with an increased risk of mortality according to prediction models.
Objectives:
To verify if quantitative analysis of chest CT (QCT) predict 10 years-mortality in SSc patients.
Methods:
SSc patients with availability of a chest CT were enrolled in 13 different centers. The CT voxel-wise analysis with a free software (www.horosproject.com) provided QCT indexes: kurtosis, skewness, mean lung attenuation and standard deviation. Patients
Gaia-ESO survey: Lithium abundances in open cluster Red Clump stars
Context. It has recently been suggested that all giant stars with masses below 2 M⊙ suffer an episode of surface lithium enrichment between the tip of the red giant branch (RGB) and the red clump (RC).
Aims. We test if the above result can be confirmed in a sample of RC and RGB stars that are members of open clusters.
Methods. We discuss Li abundances in six open clusters with ages between 1.5 and 4.9 Gyr (turn-off masses between 1.1 and 1.7 M⊙). We compare these observations with the predictions of different models that include rotation-induced mixing, thermohaline instability, mixing induced by the first He flash, and energy losses by neutrino magnetic moment.
Results. In six clusters, we find close to 35% of RC stars have Li abundances that are similar or higher than those of upper RGB stars. This can be a sign of fresh Li production. Because of the extra-mixing episode connected to the luminosity bump, the expectation has been for RC stars to have systematically lower surface Li abundances. However, we cannot confirm that this possible Li production is ubiquitous. For about 65% of RC giants, we can only determine upper limits in abundances that could be hiding very low Li content.
Conclusions. Our results indicate the possibility that Li is being produced in the RC, at levels that would not typically permit the classification of these the stars as Li rich. The determination of their carbon isotopic ratio would help to confirm that the RC giants have suffered extra mixing followed by subsequent Li enrichment. The Li abundances of the RC stars can be qualitatively explained by the models including an additional mixing episode close to the He flash.</jats:p
The GAPS Programme at TNG XLII. A characterisation study of the multi-planet system around the 400 Myr-old star HD 63433 (TOI-1726)
For more than two years, we monitored with the HARPS-N spectrograph the 400
Myr-old star HD\,63433, which hosts two close-in (orbital periods
and days) sub-Neptunes detected by the TESS space telescope, and
it was announced in 2020. Using radial velocities and additional TESS
photometry, we aim to provide the first measurement of their masses, improve
the measure of their size and orbital parameters, and study the evolution of
the atmospheric mass-loss rate due to photoevaporation. We tested
state-of-the-art analysis techniques and different models to mitigate the
dominant signals due to stellar activity that are detected in the radial
velocity time series. We used a hydro-based analytical description of the
atmospheric mass-loss rate, coupled with a core-envelope model and stellar
evolutionary tracks, to study the past and future evolution of the planetary
masses and radii. We derived new measurements of the planetary orbital periods
and radii ( d, ;
d, ), and determined
mass upper limits (11 ; 31 ;
95 confidence level), with evidence at a 2.1--2.7 significance
level that HD\,63433\,c might be a dense mini-Neptune with a Neptune-like mass.
For a grid of test masses below our derived dynamical upper limits, we found
that HD\,63433\,b has very likely lost any gaseous H-He envelope, supporting
HST-based observations that are indicative of there being no ongoing
atmospheric evaporation. HD\,63433\,c will keep evaporating over the next
5 Gyr if its current mass is 15 , while it
should be hydrodynamically stable for higher masses.Comment: 22 pages, accepted for publication on Astronomy & Astrophysic
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