599 research outputs found
Compositional characterisation of the Themis family
Context. It has recently been proposed that the surface composition of icy
main-belt asteroids (B-,C-,Cb-,Cg-,P-,and D-types) may be consistent with that
of chondritic porous interplanetary dust particles (CPIDPs). Aims. In the light
of this new association, we re-examine the surface composition of a sample of
asteroids belonging to the Themis family in order to place new constraints on
the formation and evolution of its parent body. Methods. We acquired NIR
spectral data for 15 members of the Themis family and complemented this dataset
with existing spectra in the visible and mid-infrared ranges to perform a
thorough analysis of the composition of the family. Assuming end-member
minerals and particle sizes (<2\mum) similar to those found in CPIDPs, we used
a radiative transfer code adapted for light scattering by small particles to
model the spectral properties of these asteroids. Results. Our best-matching
models indicate that most objects in our sample possess a surface composition
that is consistent with the composition of CP IDPs.We find ultra-fine grained
Fe-bearing olivine glasses to be among the dominant constituents. We further
detect the presence of minor fractions of Mg-rich crystalline silicates. The
few unsuccessfully matched asteroids may indicate the presence of interlopers
in the family or objects sampling a distinct compositional layer of the parent
body. Conclusions. The composition inferred for the Themis family members
suggests that the parent body accreted from a mixture of ice and anhydrous
silicates (mainly amorphous) and subsequently underwent limited heating. By
comparison with existing thermal models that assume a 400km diameter
progenitor, the accretion process of the Themis parent body must have occurred
relatively late (>4Myr after CAIs) so that only moderate internal heating
occurred in its interior, preventing aqueous alteration of the outer shell.Comment: 9 pages, 5 figures, accepted for publication in A&
An Extreme-AO Search for Giant Planets around a White Dwarf --VLT/SPHERE performance on a faint target GD 50
CONTEXT. Little is known about the planetary systems around single white
dwarfs although there is strong evidence that they do exist.
AIMS. We performed a pilot study with the extreme-AO system on the
Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) on the Very
Large Telescopes (VLT) to look for giant planets around a young white dwarf, GD
50.
METHODS. We were awarded science verification time on the new ESO instrument
SPHERE. Observations were made with the InfraRed Dual-band Imager and
Spectrograph in classical imaging mode in H band.
RESULTS. Despite the faintness of the target (14.2 mag in R band), the AO
loop was closed and a strehl of 37\% was reached in H band. No objects were
detected around GD 50. We achieved a 5-sigma contrast of 6.2, 8.0 and 8.25 mags
at 0{\farcs}2, 0{\farcs}4 and 0{\farcs}6 and beyond, respectively. We exclude
any substellar objects more massive than 4.0 M at 6.2 AU, 2.9
M at 12.4 AU and 2.8 M at 18.6 AU and beyond. This
rivals the previous upper limit set by Spitzer. We further show that SPHERE is
the most promising instrument available to search for close-in substellar
objects around nearby white dwarfs.Comment: A&A letters, accepte
Deep Learning for Predicting Congestive Heart Failure
Congestive heart failure (CHF) is one of the most debilitating cardiac disorders. It is a costly disease in terms of both lives and financial outlays, given the high rate of hospital re-admissions and mortality. Heart failure (HF) is notoriously difficult to identify on time, and is frequently accompanied by additional comorbidities that further complicate diagnosis. Many decision support systems (DSS) have been developed to facilitate diagnosis and to raise the standard of screening and monitoring operations, even for non-expert staff. This is confirmed in the literature by records of highly performing diagnosis-aid systems, which are unfortunately not very relevant to expert cardiologists. In order to assist cardiologists in predicting the trajectory of HF, we propose a deep learning-based system which predicts severity of disease progression by employing medical patient history. We tested the accuracy of four models on a labeled dataset, composed of 1037 records, to predict CHF severity and progression, achieving results comparable to studies based on much larger datasets, none of which used longitudinal multi-class prediction. The main contribution of this work is that it demonstrates that a fairly complicated approach can achieve good results on a medium size dataset, providing a reasonably accurate means of determining the evolution of CHF well in advance. This potentially constitutes a significant aid for healthcare managers and expert cardiologists in designing different therapies for medication, healthy lifestyle changes and quality of life (QoL) management, while also promoting allocation of resources with an evidence-based approach. © 2022 by the authors
beta Pic b position relative to the Debris Disk
Context. We detected in 2009 a giant, close-by planet orbiting {\beta} Pic, a
young star surrounded with a disk, extensively studied for more than 20 years.
We showed that if located on an inclined orbit, the planet could explain
several peculiarities of {\beta} Pictoris system. However, the available data
did not permit to measure the inclination of {\beta} Pic b with respect to the
disk, and in particular to establish in which component of the disk - the main,
extended disk or the inner inclined component/disk-, the planet was located.
Comparison between the observed planet position and the disk orientation
measured on previous imaging data was not an option because of potential biases
in the measurements. Aims. Our aim is to measure precisely the planet location
with respect to the dust disk using a single high resolution image, and
correcting for systematics or errors that degrades the precision of the disk
and planet relative position measurements. Methods. We gathered new NaCo data
at Ks band, with a set-up optimized to derive simultaneously the orientation(s)
of the disk(s) and that of the planet. Results. We show that the projected
position of {\beta} Pic b is above the midplane of the main disk. With the
current data and knowledge on the system, this implies that {\beta} Pic b
cannot be located in the main disk. The data rather suggest the planet being
located in the inclined component.Comment: 13 pages, 6 figures, to appear in Astronomy and Astrophysic
The emotional and social burden of heart failure: integrating physicians’, patients’, and caregivers’ perspectives through narrative medicine
Background: The The Roadmap Using Story Telling project used a narrative medicine (NM) framework to assess the perspectives of people with heart failure (HF), their informal caregivers and HF specialists of the impact of HF on the daily life of patients and their carers. Methods: Italian HF specialists participated on a voluntary basis, completing their own narratives, and inviting patients and their caregivers to write anonymously about their experiences, all on a dedicated online platform. The narratives were analyzed according to standard NM methodology. Results: 82 narratives were collected from patients, 61 from caregivers, and 104 from HF specialists. Analysis of the three points of view revealed the extent of the burden of illness on the entire family, particularly that of the caregiver. The impact was mainly experienced as emotional and social limitations in patients’ and their caregivers’ daily lives. The analysis of all three points of view highlighted a strong difference between how HF is perceived by patients, caregivers, and HF specialists. Conclusions: This NM project illustrates the complex issues of living with HF and gave insights to integrate three different perspectives into the HF pathway of care
Direct exoplanet detection and characterization using the ANDROMEDA method: Performance on VLT/NaCo data
Context. The direct detection of exoplanets with high-contrast imaging
requires advanced data processing methods to disentangle potential planetary
signals from bright quasi-static speckles. Among them, angular differential
imaging (ADI) permits potential planetary signals with a known rotation rate to
be separated from instrumental speckles that are either statics or slowly
variable. The method presented in this paper, called ANDROMEDA for ANgular
Differential OptiMal Exoplanet Detection Algorithm is based on a maximum
likelihood approach to ADI and is used to estimate the position and the flux of
any point source present in the field of view. Aims. In order to optimize and
experimentally validate this previously proposed method, we applied ANDROMEDA
to real VLT/NaCo data. In addition to its pure detection capability, we
investigated the possibility of defining simple and efficient criteria for
automatic point source extraction able to support the processing of large
surveys. Methods. To assess the performance of the method, we applied ANDROMEDA
on VLT/NaCo data of TYC-8979-1683-1 which is surrounded by numerous bright
stars and on which we added synthetic planets of known position and flux in the
field. In order to accommodate the real data properties, it was necessary to
develop additional pre-processing and post-processing steps to the initially
proposed algorithm. We then investigated its skill in the challenging case of a
well-known target, Pictoris, whose companion is close to the detection
limit and we compared our results to those obtained by another method based on
principal component analysis (PCA). Results. Application on VLT/NaCo data
demonstrates the ability of ANDROMEDA to automatically detect and characterize
point sources present in the image field. We end up with a robust method
bringing consistent results with a sensitivity similar to the recently
published algorithms, with only two parameters to be fine tuned. Moreover, the
companion flux estimates are not biased by the algorithm parameters and do not
require a posteriori corrections. Conclusions. ANDROMEDA is an attractive
alternative to current standard image processing methods that can be readily
applied to on-sky data
Dynamics of the Beta Pictoris planetary system and its falling evaporating bodies
For decades, the spectral variations of Beta Pictoris have been modelled as
the result of the evaporation of exocomets close to the star, termed falling
evaporating bodies (FEBs). Resonant perturbations by a giant planet have been
proposed to explain the dynamical origin of these stargrazers. The disk is now
known to harbour two giant planets, Beta Pic b and c, orbiting the star at 9.9
au and 2.7 au. While the former almost matches the planet formerly suspected,
the discovery of the latter complicates the picture. We first question the
stability of the two-planet system. Then we investigate the dynamics of a disk
of planetesimals orbiting the star with both planets to check the validity of
the FEB generation mechanism. Symplectic N-body simulations are used to
determine which regions of the planetesimal disk are dynamically stable. Then
we focus on regions where disk particles are able to reach high eccentricities
thanks to resonant mechanisms. The first result is that the system is
dynamically stable. Both planets may temporarily fall in 7:1 mean motion
resonance (MMR). Then, simulations reveal that the whole region extending
between ~1.5 au and ~25 au is unstable to planetary perturbations. However, a
disk below 1.5 au survives, which appears to constitute an active source of
FEBs via high-order MMRs with Beta Pic c. Beta Pic b acts as a distant
perturber that helps sustain the whole process. These simulations rule out the
preceding FEB generation mechanism model, which placed their origin at around
4-5 au. Conversely, FEBs are likely to originate from a region much further in
and related to MMRs with Beta Pic c. That mechanism also appears to last
longer, as new planetesimals are able to continuously enter the MMRs and evolve
towards the FEB state. Subsequently, the physical nature of the FEBs may differ
from that previously thought, and presumably may not be icy.Comment: 14 pages, 10 figures. To appear in Astronomy & Astrophysic
Proteomic analysis of dopamine and \u3b1-synuclein interplay in a cellular model of Parkinson's disease pathogenesis
Altered dopamine homeostasis is an accepted mechanism in the pathogenesis
of Parkinson\u2019s disease. a-Synuclein overexpression and impaired disposal
contribute to this mechanism. However, biochemical alterations
associated with the interplay of cytosolic dopamine and increased a-synuclein
are still unclear. Catecholaminergic SH-SY5Y human neuroblastoma
cells are a suitable model for investigating dopamine toxicity. In the present
study, we report the proteomic pattern of SH-SY5Y cells overexpressing
a-synuclein (1.6-fold induction) after dopamine exposure. Dopamine
itself is able to upregulate a-synuclein expression. However, the effect is
not observed in cells that already overexpress a-synuclein as a consequence
of transfection. The proteomic analysis highlights significant changes in 23
proteins linked to specific cellular processes, such as cytoskeleton structure
and regulation, mitochondrial function, energetic metabolism, protein synthesis,
and neuronal plasticity. A bioinformatic network enrichment procedure
generates a significant model encompassing all proteins and allows us
to enrich functional categories associated with the combination of factors
analyzed in the present study (i.e. dopamine together with a-synuclein). In
particular, the model suggests a potential involvement of the nuclear factor kappa B pathway that is experimentally confirmed. Indeed, a-synuclein significantly
reduces nuclear factor kappa B activation, which is completely quenched by dopamine treatment.Altered dopamine homeostasis is an accepted mechanism in the pathogenesis of Parkinson's disease. \u3b1-Synuclein overexpression and impaired disposal contribute to this mechanism. However, biochemical alterations associated with the interplay of cytosolic dopamine and increased \u3b1-synuclein are still unclear. Catecholaminergic SH-SY5Y human neuroblastoma cells are a suitable model for investigating dopamine toxicity. In the present study, we report the proteomic pattern of SH-SY5Y cells overexpressing \u3b1-synuclein (1.6-fold induction) after dopamine exposure. Dopamine itself is able to upregulate \u3b1-synuclein expression. However, the effect is not observed in cells that already overexpress \u3b1-synuclein as a consequence of transfection. The proteomic analysis highlights significant changes in 23 proteins linked to specific cellular processes, such as cytoskeleton structure and regulation, mitochondrial function, energetic metabolism, protein synthesis, and neuronal plasticity. A bioinformatic network enrichment procedure generates a significant model encompassing all proteins and allows us to enrich functional categories associated with the combination of factors analyzed in the present study (i.e. dopamine together with \u3b1-synuclein). In particular, the model suggests a potential involvement of the nuclear factor kappa B pathway that is experimentally confirmed. Indeed, \u3b1-synuclein significantly reduces nuclear factor kappa B activation, which is completely quenched by dopamine treatment. \ua9 2010 The Authors Journal compilation \ua9 2010 FEBS
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