638 research outputs found
Clinical survey of neurosensory side-effects of mandibular parasymphyseal bone harvesting
The aim of the present survey was to assess neurosensory disturbances and/or tooth-pulp sensitivity losses after mandibular parasymphyseal bone-harvesting procedures. Twenty-eight harvesting areas in 16 patients were surveyed. Mucosal and skin sensitivity of the chin/lower lip, divided into four regions, were determined via Pointed-Blunt and Two-Point-Discrimination Tests. Pulp sensitivity of the mandibular teeth from the left second bicuspid to the right second bicuspid was tested by cold vitality preoperatively and 12 months postoperatively. Teeth were grouped according to sensitivity alterations and distance from the harvesting defects, as measured on CT scans, and statistically significant differences sought. At 12 months, 29% of preoperatively vital cuspids overlying the harvesting defects revealed pulp-sensitivity losses; no patient reported anaesthesia or analgesia; hypoaesthesia was present in 4% (8 sites; 2 patients), hypoalgesia was present in 3% (5 sites; 2 patients) and Two-Point-Discrimination Tests yielded pathologic responses in 5% of tested areas (10 sites; 4 patients). Teeth with and without pulp sensitivity changes were statistically indistinguishable regarding distances between root apices or mental foramen and the harvesting defect. The loss of pulp sensitivity in any tooth cannot be predicted simply on the basis of the distance between its apex and the harvesting osteotomy line
The low Sr/Ba ratio on some extremely metal-poor stars
It has been noted that, in classical extremely metal-poor (EMP) stars, the
abundance ratio of Sr and Ba, is always higher than [Sr/Ba] = -0.5, the value
of the solar r-only process; however, a handful of EMP stars have recently been
found with a very low Sr/Ba ratio. We try to understand the origin of this
anomaly by comparing the abundance pattern of the elements in these stars and
in the classical EMP stars. Four stars with very low Sr/Ba ratios were observed
and analyzed within LTE approximation through 1D (hydrostatic) model
atmosphere, providing homogeneous abundances of nine neutron-capture elements.
In CS 22950-173, the only turnoff star of the sample, the Sr/Ba ratio is, in
fact, found to be higher than the r-only solar ratio, so the star is discarded.
The remaining stars (CS 29493-090, CS 30322-023, HE 305-4520) are cool evolved
giants. They do not present a clear carbon enrichment. The abundance patterns
of the neutron-capture elements in the three stars are strikingly similar to a
theoretical s-process pattern. This pattern could at first be attributed to
pollution by a nearby AGB, but none of the stars presents a clear variation in
the radial velocity indicating the presence of a companion. The stellar
parameters seem to exclude any internal pollution in a TP-AGB phase for at
least two of these stars. The possibility that the stars are early-AGB stars
polluted during the core He flash does not seem compatible with the theory.Comment: Accepted for publication in Astronomy and Astrophysic
Experimental tests to recover the photovoltaic power by battery system
The uncertainty and variability of the Renewable Energy Sources (RES) power plants within the power grid is an open issue. The
present study focuses on the use of batteries to overcome the limitations associated with the photovoltaic inverter operation,
trying to maximize the global energy produced. A set of switches, was placed between a few photovoltaic modules and a
commercial inverter, capable to change configuration of the plant dynamically. Such system stores the power that the inverter is
not able to let into the grid inside batteries. At the base of this optimization, there is the achievement of two main configurations
in which the batteries and the photovoltaic modules are electrically connected in an appropriate manner as a function of inverter
efficiency and thus solar radiation. A control board and the relative program, to change the configuration, was designed and
implemented, based on the value of the measured radiation, current, batteries voltage, and calculated inverter efficiency. Finally
from the cost and impact analysis we can say that, today the technology of lithium batteries, for this application, is still too
expensive in comparison with lead-acid batteries
Volume changes of grafted autogenous bone in sinus augmentation procedure
to evaluate associations between the osseous remodelling add 3-dimensional features of both the grafted bone and the recipient site as well as the density of the grafted bone,and to assess the relation between the degree of bone resorption and the type of autogenous bone.grafting procedure or the source(block or particulate bone from iliac crest or block bone from chin
Abundances of lithium, oxygen, and sodium in the turn-off stars of Galactic globular cluster 47 Tuc
We aim to determine abundances of Li, O and Na in a sample of of 110 turn-off
(TO) stars, in order to study the evolution of light elements in this cluster
and to put our results in perspective with observations of other globular and
open clusters, as well as with field stars. We use medium resolution spectra
obtained with the GIRAFFE spectrograph at the ESO 8.2m Kueyen VLT telescope and
use state of the art 1D model atmospheres and NLTE line transfer to determine
the abundances. We also employ CO5BOLD hydrodynamical simulations to assess the
impact of stellar granulation on the line formation and inferred abundances.
Our results confirm the existence of Na-O abundance anti-correlation and hint
towards a possible Li-O anti-correlation in the TO stars of 47 Tuc. We find no
convincing evidence supporting the existence of Li-Na correlation. The obtained
3D NLTE mean lithium abundance in a sample of 94 TO stars where Li lines were
detected reliably,
dex, appears to be significantly lower than what is observed in other globular
clusters. At the same time, star-to-star spread in Li abundance is also larger
than seen in other clusters. The highest Li abundance observed in 47 Tuc is
about 0.1 dex lower than the lowest Li abundance observed among the un-depleted
stars of the metal-poor open cluster NGC 2243. The lithium abundances in 47
Tuc, when put into context with observations in other clusters and field stars,
suggest that stars that are more metal-rich than [FeH] \sim -1.0 experience
significant lithium depletion during their lifetime on the main sequence, while
the more metal-poor stars do not. Rather strikingly, our results suggest that
initial lithium abundance with which the star was created may only depend on
its age (the younger the star, the higher its Li content) and not on its
metallicity.Comment: 24 pages, 13 figures; discussion and conclusions expanded. Accepted
for publication in A&
New ATLAS9 And MARCS Model Atmosphere Grids for the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
We present a new grid of model photospheres for the SDSS-III/APOGEE survey of
stellar populations of the Galaxy, calculated using the ATLAS9 and MARCS codes.
New opacity distribution functions were generated to calculate ATLAS9 model
photospheres. MARCS models were calculated based on opacity sampling
techniques. The metallicity ([M/H]) spans from -5 to 1.5 for ATLAS and -2.5 to
0.5 for MARCS models. There are three main differences with respect to previous
ATLAS9 model grids: a new corrected H2O linelist, a wide range of carbon
([C/M]) and alpha element [alpha/M] variations, and solar reference abundances
from Asplund et al. 2005. The added range of varying carbon and alpha element
abundances also extends the previously calculated MARCS model grids. Altogether
1980 chemical compositions were used for the ATLAS9 grid, and 175 for the MARCS
grid. Over 808 thousand ATLAS9 models were computed spanning temperatures from
3500K to 30000K and log g from 0 to 5, where larger temperatures only have high
gravities. The MARCS models span from 3500K to 5500K, and log g from 0 to 5.
All model atmospheres are publically available online.Comment: 8 pages, 6 figures, 5 tables, accepted for publication in The
Astronomical Journa
A Double Main Sequence in the Globular Cluster NGC 6397
High-precision multi-band HST photometry reveals that the main sequence (MS)
of the globular cluster NGC 6397 splits into two components, containing ~30%
and ~70% of the stars. This double sequence is consistent with the idea that
the cluster hosts two stellar populations: (i) a primordial population that has
a composition similar to field stars, and containing ~30% of the stars, and
(ii) a second generation with enhanced sodium and nitrogen, depleted carbon and
oxygen, and a slightly enhanced helium abundance (Delta Y~0.01). We examine the
color difference between the two sequences across a variety of color baselines
and find that the second sequence is anomalously faint in m_F336W. Theoretical
isochrones indicate that this could be due to NH depletion.Comment: 19 pages, 11 figures, accepted for pubblication in Ap
X-Shooter GTO: evidence for a population of extremely metal-poor, alpha-poor stars
The extremely metal-poor stars are the direct descendants of the first
generation stars. They carry the chemical signature of the pristine Universe at
the time they formed, shortly after the Big Bang. We aim to derive information
about extremely metal-poor stars from their observed spectra. Four extremely
metal-poor stars were selected from the Sloan Digital Sky Survey (SDSS) and
observed during the guaranteed observing time of X-Shooter. The X-Shooter
spectra were analysed using an automatic code, MyGIsFOS, which is based on a
traditional analysis method. It makes use of a synthetic grid computed from
one-dimensional, plane-parallel, hydrostatic model atmospheres. The low
metallicity derived from the SDSS spectra is confirmed here. Two kinds of stars
are found. Two stars are confirmed to be extremely metal-poor, with no evidence
of any enhancement in carbon. The two other stars are strongly enhanced in
carbon. We could not derive iron abundance for one of them, while [Ca/H] is
below -4.5. Two of the stars are members of the rare population of extremely
metal-poor stars low in alpha elements.Comment: A&A in pres
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