599 research outputs found
The M4 Core Project with HST - IV. Internal Kinematics from Accurate Radial Velocities of 2771 Cluster Members
We present a detailed study of the internal kinematics of the Galactic
Globular Cluster M 4 (NGC 6121), by deriving the radial velocities from 7250
spectra for 2771 stars distributed from the upper part of the Red Giant Branch
down to the Main Sequence. We describe new approaches to determine the
wavelength solution from day-time calibrations and to determine the radial
velocity drifts that can occur between calibration and science observations
when observing with the GIRAFFE spectrograph at VLT. Two techniques to
determine the radial velocity are compared, after a qualitative description of
their advantages with respect to other commonly used algorithm, and a new
approach to remove the sky contribution from the spectra obtained with
fibre-fed spectrograph and further improve the radial velocity precision is
presented. The average radial velocity of the cluster is km s with an average dispersion of km
s. Using the same dataset and the same statistical approach of previous
analyses, 20 additional binary candidates are found, for a total of 87
candidates. A new determination of the internal radial velocity dispersion as a
function of cluster distance is presented, resulting in a dispersion of
km s within 2 from the center of cluster and steadily
decreasing outward. We statistically confirm the small amplitude of the cluster
rotation, as suggested in the past by several authors. This new analysis
represents a significant improvement with respect to previous results in
literature and provides a fundamental observational input for the modeling of
the cluster dynamics.Comment: 17 pages, 17 figures. Accepted for publication in MNRAS on September
15, 201
A simplex method for the calibration of a MEG device
MagnetoEncephaloGraphy (MEG) devices are helmet-shaped arrays of sensors that measure the tiny magnetic fields produced by neural currents. As they operate at low temperature, they are typically immersed in liquid helium. However, during the cooling process the sensor position and shape can change, with respect to nominal values, due to thermal stress. This implies that an accurate sensor calibration is required before a MEG device is utilized in either neuroscientific research or clinical workflow. Here we describe a calibration scheme developed for the optimal use of a MEG system recently realized at the "Istituto di Cibernetica e Biofisica" of the Italian CNR. To achieve the calibration goal a dedicated magnetic source is used (calibration device) and the geometric parameters of the sensors are determined through an optimisation procedure, based on the Nelder-Mead algorithm, which maximises the correlation coefficient between the predicted and the recorded magnetic field. Then the sensitivity of the sensors is analytically estimated. The developed calibration procedure is validated with synthetic data mimicking a real scenario
Evidence of very low metallicity and high ionization state in a strongly lensed, star-forming dwarf galaxy at z=3.417
We investigate the gas-phase metallicity and Lyman Continuum (LyC) escape
fraction of a strongly gravitationally lensed, extreme emission-line galaxy at
z=3.417, J1000+0221S, recently discovered by the CANDELS team. We derive
ionization and metallicity sensitive emission-line ratios from H+K band
LBT/LUCI medium resolution spectroscopy. J1000+0221S shows high ionization
conditions, as evidenced by its enhanced [OIII]/[OII] and [OIII]/Hbeta ratios.
Consistently, strong-line methods based on the available line ratios suggest
that J1000+0221S is an extremely metal-poor galaxy, with a metallicity of
12+log(O/H) < 7.44 (< 5% solar), placing it among the most metal-poor
star-forming galaxies at z > 3 discovered so far. In combination with its low
stellar mass (2x10^8 Msun) and high star formation rate (5 Msun/yr), the
metallicity of J1000+0221S is consistent with the extrapolation to low masses
of the mass-metallicity relation traced by Lyman-break galaxies at z > 3, but
it is 0.55 dex lower than predicted by the fundamental metallicity relation at
z < 2.5. These observations suggest the picture of a rapidly growing galaxy,
possibly fed by the massive accretion of pristine gas. Additionally, deep
LBT/LBC in the UGR bands are used to derive a limit to the LyC escape fraction,
thus allowing us to explore for the first time the regime of sub-L* galaxies at
z > 3. We find a 1sigma upper limit to the escape fraction of 23%, which adds a
new observational constraint to recent theoretical models predicting that
sub-L* galaxies at high-z have high escape fractions and thus are the
responsible for the reioization of the Universe.Comment: 5 pages, 3 figures and 1 table. Accepted for publication in ApJ
Letter
S-ICD is effective in preventing sudden death in Arrhythmogenic Cardiomyopathy athletes during exercise
Here we describe the cases of two elite athletes, with a diagnosis of Arrhythmogenic Cardiomyopathy (ACM), in which a Subcutaneous Implantable Cardioverter Defibrillator (S-ICD) has been implanted. Both patients experienced a ventricular tachycardia during exercise and received effective S-ICD shocks that interrupted arrhythmias. This report reveals for the first time that the S-ICD is effective in reverting arrhythmias in ACM patients, even during exercise. Moreover, these cases may confirm that competition/physical activity is associated with ICD shocks
Metallicity evolution, metallicity gradients and gas fractions at z~3.4
We used near-infrared integral field spectroscopic observations from the
AMAZE and LSD programs to constrain the metallicity in a sample of 40 star
forming galaxies at 3<z<5 (most of which at z~3.4). We measure metallicities by
exploiting strong emission line diagnostics. We found that a significant
fraction of star-forming galaxies at z~3.4 deviate from the Fundamental
Metallicity Relation (FMR), with a metallicity up to a factor of ten lower than
expected according to the FMR. This deviation does not correlate with the
dynamical properties of the galaxy or with the presence of interactions. To
investigate the origin of the metallicity deviations in more detail, we also
infer information on the gas content, by inverting the Schmidt-Kennicutt
relation. In agreement with recent CO observational data, we found that, in
contrast with the steeply rising trend at 0<z<2, the gas fraction in massive
galaxies remains constant, with indication of a marginal decline, at 2<z<3.5.
When combined with the metallicity information, we infer that to explain both
the low metallicity and gas content in z~3.4 galaxies, both prominent outflows
and massive pristine gas inflows are needed. In ten galaxies we can also
spatially resolve the metallicity distribution. We found that the metallicity
generally anticorrelates with the distribution of star formation and with the
gas surface density. We discuss these findings in terms of pristine gas inflows
towards the center, and outflows of metal rich gas from the center toward the
external regions. (Abridged)Comment: Replaced to match the published versio
Trans-arterial radioembolization in intermediate-advanced hepatocellular carcinoma: systematic review and meta-analyses.
Published onlineJournal ArticleThis is the final version of the article. Available from Impact Journals via the DOI in this record.Trans-arterial radioembolization (TARE) is a recognized, although not explicitly recommended, experimental therapy for unresectable hepatocellular carcinoma (HCC).A systematic literature review was performed to identify published studies on the use of TARE in intermediate and advanced stages HCC exploring the efficacy and safety of this innovative treatment.Twenty-one studies reporting data on overall survival (OS) and time to progression (TTP), were included in a meta-analysis. The pooled post-TARE OS was 63% (95% CI: 56-70%) and 27% (95% CI: 21-33%) at 1- and 3-years respectively in intermediate stage HCC, whereas OS was 37% (95% CI: 26-50%) and 13% (95% CI: 9-18%) at the same time intervals in patients with sufficient liver function (Child-Pugh A-B7) but with an advanced HCC because of the presence of portal vein thrombosis. When an intermediate and advanced case-mix was considered, OS was 58% (95% CI: 48-67%) and 17% (95% CI: 12-23%) at 1- and 3-years respectively. As for TTP, only four studies reported data: the observed progression probability was 56% (95% CI: 41-70%) and 73% (95% CI: 56-87%) at 1 and 2 years respectively. The safety analysis, focused on the risk of liver decompensation after TARE, revealed a great variability, from 0-1% to more than 36% events, influenced by the number of procedures, patient Child-Pugh stage and treatment duration.Evidence supporting the use of radioembolization in HCC is mainly based on retrospective and prospective cohort studies. Based on this evidence, until the results of the ongoing randomized trials become available, radioembolization appears to be a viable treatment option for intermediate-advanced stage HCC.The present study was funded by ASBM Srl through an unrestricted grant to CERGAS, Bocconi University, Via Roentgen 1, 20136 Milan, Italy
The lung microbiota: role in maintaining pulmonary immune homeostasis and its implications in cancer development and therapy
Like other body districts, lungs present a complex bacteria community. An emerging function of lung microbiota is to promote and maintain a state of immune tolerance, to prevent uncontrolled and not desirable inflammatory response caused by inhalation of harmless environmental stimuli. This effect is mediated by a continuous dialog between commensal bacteria and immune cells resident in lungs, which express a repertoire of sensors able to detect microorganisms. The same receptors are also involved in the recognition of pathogens and in mounting a proper immune response. Due to its important role in preserving lung homeostasis, the lung microbiota can be also considered a mirror of lung health status. Indeed, several studies indicate that lung bacterial composition drastically changes during the occurrence of pulmonary pathologies, such as lung cancer, and the available data suggest that the modifications of lung microbiota can be part of the etiology of tumors in lungs and can influence their progression and response to therapy. These results provide the scientific rationale to analyze lung microbiota composition as biomarker for lung cancer and to consider lung microbiota a new potential target for therapeutic intervention to reprogram the antitumor immune microenvironment. In the present review, we discussed about the role of lung microbiota in lung physiology and summarized the most relevant data about the relationship between lung microbiota and cancer
Fast Gibbs sampling for high-dimensional Bayesian inversion
Solving ill-posed inverse problems by Bayesian inference has recently
attracted considerable attention. Compared to deterministic approaches, the
probabilistic representation of the solution by the posterior distribution can
be exploited to explore and quantify its uncertainties. In applications where
the inverse solution is subject to further analysis procedures, this can be a
significant advantage. Alongside theoretical progress, various new
computational techniques allow to sample very high dimensional posterior
distributions: In [Lucka2012], a Markov chain Monte Carlo (MCMC) posterior
sampler was developed for linear inverse problems with -type priors. In
this article, we extend this single component Gibbs-type sampler to a wide
range of priors used in Bayesian inversion, such as general priors
with additional hard constraints. Besides a fast computation of the
conditional, single component densities in an explicit, parameterized form, a
fast, robust and exact sampling from these one-dimensional densities is key to
obtain an efficient algorithm. We demonstrate that a generalization of slice
sampling can utilize their specific structure for this task and illustrate the
performance of the resulting slice-within-Gibbs samplers by different computed
examples. These new samplers allow us to perform sample-based Bayesian
inference in high-dimensional scenarios with certain priors for the first time,
including the inversion of computed tomography (CT) data with the popular
isotropic total variation (TV) prior.Comment: submitted to "Inverse Problems
Isolation and characterization of cardiac mesenchymal stromal cells from endomyocardial bioptic samples of arrhythmogenic cardiomyopathy patients
A normal adult heart is composed of several different cell types, among which cardiac mesenchymal stromal cells represent an abundant population. The isolation of these cells offers the possibility of studying their involvement in cardiac diseases, and, in addition, provides a useful primary cell model to investigate biological mechanisms. Here, the method for the isolation of C-MSC from arrhythmogenic cardiomyopathy patients\u2019 bioptic samples is described. The endomyocardial biopsy sampling is guided in the right ventricular areas adjacent to the scar visualized by electro-anatomical mapping. The digestion of the biopsies in collagenase and their plating on a plastic dish in culture medium to allow C-MSC growth is described. The isolated cells can be expanded in culture for several passages. To confirm their mesenchymal phenotype, the description of immuno-phenotypical characterization is provided. C-MSC are able to differentiate into several cell types like adipocytes, chondrocytes, and osteoblasts: in the context of ACM, characterized by adipocyte deposits in patients\u2019 hearts, the protocols for the adipogenic differentiation of C-MSC and the characterization of lipid droplet accumulation are described
A mass threshold in the number density of passive galaxies at z2
The process that quenched star formation in galaxies at intermediate and high
redshift is still the subject of considerable debate. One way to investigate
this puzzling issue is to study the number density of quiescent galaxies at
z~2, and its dependence on mass. Here we present the results of a new study
based on very deep Ks-band imaging (with the HAWK-I instrument on the VLT) of
two HST CANDELS fields (the UKIDSS Ultra-deep survey (UDS) field and
GOODS-South). The new HAWK-I data (taken as part of the HUGS VLT Large Program)
reach detection limits of Ks>26 (AB mag). We select a sample of
passively-evolving galaxies in the redshift range 1.4<z<2.5. Thanks to the
depth and large area coverage of our imaging, we have been able to extend the
selection of quiescent galaxies a magnitude fainter than previous analyses.
Through extensive simulations we demonstrate, for the first time, that the
observed turn-over in the number of quiescent galaxies at K>22 is real. This
has enabled us to establish unambiguously that the number counts of quiescent
galaxies at z~2 flatten and slightly decline at magnitudes fainter than
Ks~22(AB mag.). We show that this trend corresponds to a stellar mass threshold
below which the mechanism that halts the star
formation in high-redshift galaxies seems to be inefficient. Finally we compare
the observed pBzK number counts with those of quiescent galaxies extracted from
four different semi-analytic models. We find that none of the models provides a
statistically acceptable description of the number density of quiescent
galaxies at these redshifts. We conclude that the mass function of quiescent
galaxies as a function of redshift continues to present a key and demanding
challenge for proposed models of galaxy formation and evolution.Comment: Accepted for publication on Astronomy and Astrophysic
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