881 research outputs found
Characterization of a defective PbWO4 crystal cut along the a-c crystallographic plane: structural assessment and a novel photoelastic stress analysis
Among scintillators, the PWO is one of the most widely used, for instance in
CMS calorimeter at CERN and PANDA project. Crystallographic structure and
chemical composition as well as residual stress condition, are indicators of
homogeneity and good quality of the crystal. In this paper, structural
characterization of a defective PbWO4 (PWO) crystal has been performed by X-ray
Diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and Photoelasticity in
the unusual a-c crystallographic plane. XRD and EDS analysis have been used to
investigate crystallographic orientation and chemical composition, while stress
distribution, which indicates macroscopic inhomogeneities and defects, has been
obtained by photoelastic approaches, in Conoscopic and Sphenoscopic
configuration. Since the sample is cut along the a-c crystallographic plane, a
new method is proposed for the interpretation of the fringe pattern. The
structural analysis has detected odds from the nominal lattice dimension, which
can be attributed to the strong presence of Pb and W. A strong inhomogeneity
over the crystal sample has been revealed by the photoelastic inspection. The
results give reliability to the proposed procedure which is exploitable in
crystals with other structures.Comment: 18 pages, 10 figures, revised versio
On the HI-Hole and AGB Stellar Population of the Sagittarius Dwarf Irregular Galaxy
Using two HST/ACS data-sets that are separated by ~2 years has allowed us to
derive the relative proper-motion for the Sagittarius dwarf irregular (SagDIG)
and reduce the heavy foreground Galactic contamination. The proper-motion
decontaminated SagDIG catalog provides a much clearer view of the young
red-supergiant and intermediate-age asymptotic giant branch populations. We
report the identification of 3 Milky Way carbon-rich dwarf stars, probably
belonging to the thin disk, and pointing to the high incidence of this class at
low Galactic latitudes. A sub-group of 4 oxygen-rich candidate stars depicts a
faint, red extension of the well-defined SagDIG carbon-rich sequence. The
origin of these oxygen-rich candidate stars remains unclear, reflecting the
uncertainty in the ratio of carbon/oxygen rich stars. SagDIG is also a gas-rich
galaxy characterized by a single large cavity in the gas disk (HI-hole), which
is offset by ~360 pc from the optical centre of the galaxy. We nonetheless
investigate the stellar feedback hypothesis by comparing the proper-motion
cleaned stellar populations within the HI-hole with appropriately selected
comparison regions, having higher HI densities external to the hole. The
comparison shows no significant differences. In particular, the centre of the
HI-hole (and the comparison regions) lack stellar populations younger than ~400
Myr, which are otherwise abundant in the inner body of the galaxy. We conclude
that there is no convincing evidence that the SagDIG HI-hole is the result of
stellar feedback, and that gravitational and thermal instabilities in the gas
are the most likely mechanism for its formation.Comment: Accepted for publication in A&A, 11 pages, 6 jpeg figure
Current status of laboratory and imaging diagnosis of neonatal necrotizing enterocolitis
Necrotizing enterocolitis continues to be a devastating disease process for very low birth weight infants in Neonatal Intensive Care Units. The aetiology and pathogenesis of necrotizing enterocolitis are not definitively understood. It is known that necrotizing enterocolitis is secondary to a complex interaction of multiple factors that results in mucosal damage, which leads to intestinal ischemia and necrosis. Advances in neonatal care, including resuscitation and ventilation support technology, have seen increased survival rates among premature neonates and a concomitant detection in the incidence of this intestinal disease.Diagnosis can be difficult, and identifying infants at the onset of disease remains a challenge. Early diagnosis, which relies on imaging findings, and initiation of prompt therapy are essential to limit morbidity and mortality. Moreover, early management is critical and life-saving.This review summarizes what is known on the laboratory and instrumental diagnostic strategies needed to improve neonatal outcomes and, possibily, to prevent the onset of an overt necrotizing enterocolitis
The old and heavy bulge of M31 I. Kinematics and stellar populations
We present new optical long-slit data along 6 position angles of the bulge
region of M31. We derive accurate stellar and gas kinematics reaching 5 arcmin
from the center, where the disk light contribution is always less than 30%, and
out to 8 arcmin along the major axis, where the disk makes 55% of the total
light. We show that the velocity dispersions of McElroy (1983) are severely
underestimated (by up to 50 km/s) and previous dynamical models have
underestimated the stellar mass of M31's bulge by a factor 2. Moreover, the
light-weighted velocity dispersion of the galaxy grows to 166 km/s, thus
reducing the discrepancy between the predicted and measured mass of the black
hole at the center of M31. The kinematic position angle varies with distance,
pointing to triaxiality. We detect gas counterrotation near the bulge minor
axis. We measure eight emission-corrected Lick indices. They are approximately
constant on circles. We derive the age, metallicity and alpha-element
overabundance profiles. Except for the region in the inner arcsecs of the
galaxy, the bulge of M31 is uniformly old (>12 Gyr, with many best-fit ages at
the model grid limit of 15 Gyr), slightly alpha-elements overabundant
([alpha/Fe]~0.2) and at solar metallicity, in agreement with studies of the
resolved stellar components. The predicted u-g, g-r and r-i Sloan color
profiles match reasonably well the dust-corrected observations. The stellar
populations have approximately radially constant mass-to-light ratios (M/L_R ~
4-4.5 for a Kroupa IMF), in agreement with stellar dynamical estimates based on
our new velocity dispersions. In the inner arcsecs the luminosity-weighted age
drops to 4-8 Gyr, while the metallicity increases to above 3 times the solar
value.Comment: Accepted for publication in A&
Non invasive tools for the diagnosis of liver cirrhosis
Liver cirrhosis (LC), the end stage of many forms of chronic hepatitis of different etiologies is a diffuse
process characterized by fibrosis and the conversion of normal liver architecture into structurally abnormal nodules surrounded by annular fibrosis. This chronic
progressive clinical condition, leads to liver cell failure and portal hypertension, which can favour the onset of hepatocellular carcinoma. Defining the phase of the natural history is crucial for therapeutic choice and prognosis. Liver biopsy is currently considered the
best available standard of reference but it has some limits, so alternative tools have been developed to substitute liver biopsy when assessing liver fibrosis.
Serum markers offer a cost-effective alternative to liver biopsy being less invasive and theoretically without
complications. They can be classified into direct and indirect markers which may be used alone or in combination to produce composite scores. Diagnostic
imaging includes a number of instruments and techniques to estimate liver fibrosis and cirrhosis like
ultrasound (US), US Doppler, contrast enhanced US and Elastography. US could be used for the diagnosis of
advanced LC while is not able to evaluate progression of fibrosis, in this case Elastography is more reliable.
This review aims to revise the most recent data from the literature about non invasive methods useful in
defining liver fibrosis
VLT multi-epoch radial velocity survey toward NGC 6253. Analysis of three transiting planetary candidates
We measured the radial velocity of 139 stars in the region of NGC 6253,
discussing cluster's membership and binarity in this sample, complementing our
analysis with photometric, proper motion, and radial velocity data available
from previous studies of this cluster, and analyzing three planetary transiting
candidates we found in the field of NGC 6253. Spectra were obtained with the
UVES and GIRAFFE spectrographs at the VLT, during three epochs in August 2008.
The mean radial velocity of the cluster is -29.11+/-0.85 km/s. Using both
radial velocities and proper motions we found 35 cluster's members, among which
12 are likely cluster's close binary systems. One star may have a sub-stellar
companion, requiring a more intensive follow-up. Our results are in good
agreement with past radial velocity and photometric measurements. Furthermore,
using our photometry, astrometry and spectroscopy we identified a new sub-giant
branch eclipsing binary system, member of the cluster. The cluster's close
binary frequency at 29% +/- 9% (34% +/-10% once including long period
binaries), appears higher than the field binary frequency equal to (22% +/- 5%,
though these estimates are still consistent within the uncertainties. Among the
three transiting planetary candidates the brightest one (V=15.26) is worth to
be more intensively investigated with higher percision spectroscopy. We
discussed the possibility to detect sub-stellar companions (brown dwarfs and
planets) with the radial velocity technique (both with UVES/GIRAFFE and HARPS)
around turn-off stars of old open clusters [abridged].Comment: 25 pages, 18 figures, 8 tables. Accepted for publication in A&
Variable stars in the open cluster NGC 6791 and its surrounding field
Aims: This work presents a high--precision variability survey in the field of
the old, super metal-rich open cluster NGC 6791.
Methods: The data sample consists of more than 75,000 high-precision CCD time
series measurements in the V band obtained mainly at the Canada-France-Hawaii
Telescope, with additional data from S. Pedro Martir and Loiano observatories,
over a time span of ten nights. The field covers an area of 42x28 arcmin^2.
Results: We have discovered 260 new variables and re-determined periods and
amplitudes of 70 known variable stars. By means of a photometric evaluation of
the membership in NGC 6791, and a preliminary membership based on the proper
motions, we give a full description of the variable content of the cluster and
surrounding field in the range 16<V<23.5. Accurate periods can be given for the
variables with P<4.0 d, while for ones with longer periods the limited
time-baseline hampered precise determinations. We categorized the entire sample
as follows: 6 pulsating, 3 irregular, 3 cataclysmic, 89 rotational variables
and 61 eclipsing systems; moreover, we detected 168 candidate variables for
which we cannot give a variability class since their periods are much longer
than our time baseline.
Conclusions: On the basis of photometric considerations, and of the positions
of the stars with respect to the center of the cluster, we inferred that 11 new
variable stars are likely members of the cluster, for 22 stars the membership
is doubtful and 137 are likely non-members. We also detected an outburst of
about 3 mag in the light curve of a very faint blue star belonging to the
cluster and we suggest that this star could be a new U Gem (dwarf nova)
cataclysmic variable.Comment: 24 pages, 19 Figures, A&A accepte
Pu\uf2 la misura della densit\ue0 tumorale essere considerata un parametro attendibile nella valutazione della risposta ai trattamenti antiangiogenetici ed un fattore predittivo della PFS nell'HCC avanzato?
A phenobarbital overdose: a case report
Background: Phenobarbital is a long-acting barbiturate,
responsible for many cases of poisoning, from unintentional
overdose or attempted suicide. We report a case of phenobarbital
overdose in a patient with history of depression.
Patients and Methods: A 60 year old woman was admitted to
our Internal Medicine Unit for drowsiness, irritability, difficulties in
the maintenance of an upright position, dysphasia and weakness.
She was suffering from depression and epilepsy and treated with
phenobarbital 150 mg/die.
Results: At the admittance, she had high fever and neck stiffness;
phenobarbital serum levels were 71.2 mcg/ml (3 times u.n.l.);
aminotransferases were 12-17u.n.l. Arterial blood pressure was
80/50 mmHg. An inflammatory meningeal process was excluded
by lumbar puncture; a brain and spinal cord CT scan excluded
spine bone lesions and ischemic stroke. In the suspect of an
overdose, a protocol of urine alkalinization was applied resulting
in a reduction of phenobarbital levels below the therapeutic range
in about 6 days, with state of consciousness, cognitive and
behavioral functions improvement. A rapid normalization in
aminotransferases levels was noted and serology for hepatitis
viruses (HAV, HBV, CMV, EBV, HSV) resulted negative.
Conclusions: In our patient phenobarbital was responsible for
stupor, hypotension, hypertonicity and aminotransferases
elevation, whereas fever was due to a concomitant pulmonary
inflammatory process resolved after antibiotic therapy. Despite the
use of these drugs has been progressively reduced, the number
overdose reports remains still hig
Software applicativo per la gestione delle stazioni della rete sismica mobile in dotazione all’Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Catania
- …