272 research outputs found
Evaluating GAIA performances on eclipsing binaries. III. Orbits and stellar parameters for UW LMi, V432 Aur and CN Lyn
The orbits and physical parameters of three detached F and G-type eclipsing
binaries have been derived combining Hipparcos H(P) photometry with 8480-8740
Ang ground-based spectroscopy, simulating the photometric+spectroscopic
observations that the GAIA mission will obtain. Tycho B(T) and V(T) light
curves are too noisy to be modeled for the three targets, and only mean Tycho
colors are retained to constrain the temperature. No previous combined
photometric+spectroscopic solution exists in literature for any of the three
targets. Quite remarkably, CN Lyn turned out to be an equal masses F5 triple
system. Distances from the orbital solutions agree within the astrometric error
with the Hipparcos parallaxes.Comment: A&A, accepted in pres
APPLICABIILITA’ DELL’APPROCCIO MULTICOSTELLATION CON L’AUSILIO DI SOFTWARE COMMERCIALI NELLA RETE UNIPA
Lo sviluppo dei sistemi di radio navigazione satellitare richiede lo studio di soluzioni nuove, in particolar modo per quanto riguarda l'integrazione di più sistemi satellitari. In numerosi lavori è stata studiata l'influenza che l'utilizzo congiunto dei sistemi satellitari GLONASS e GPS hanno in un rilievo topografico.
Tuttavia, scopo di questo articolo scientifico non è tanto quello di valutare questa influenza, ma di dare un forte apporto allo sviluppo di un nuova metodologia, del tutto innovativa, denominata Multiconstellation. L'approccio Multiconstellation, come è noto in letteratura, è stato introdotto qualche anno or sono dai ricercatori dell'area Geomatica dell'Università La Sapienza di Roma; da allora sono stati compiuti alcuni lavori con tale approccio con sessioni limitata ad una durata di 30 minuti, su basi di lunghezza minima.
Con questo nuovo metodo, modificando i files RINEX originali mediante l'utilizzo del software Multicon, è possibile raddoppiare il numero di basi linearmente indipendenti per sessione, dimezzando pertanto il numero di sessioni da utilizzare e quindi il tempo necessario per eseguire l'intero rilievo. Considerando che nella pratica professionale un topografo utilizza spesso strumenti noleggiati e software commerciali per le elaborazioni dei dati, dimezzare i tempi complessivi di un rilevo implica diminuire i costi complessivi dello stesso. Essendo quindi evidenti i vantaggi teorici di questo nuovo approccio rispetto a quello tradizionale, si è pensato di valutare la sua affidabilità in termini di precisioni raggiungibili con sessioni di durata più lunga di quelle utilizzate negli anni scorsi, cioè con durata temporale estesa tra le 3 e le 12 ore, considerando i dati provenienti dalla rete sperimentale gestita dal DICAM dell’Università di Palermo, mediante l’utilizzo dei principali software commerciali delle più prestigiose case produttrici mondiali (Leica LGO ver.8,0, Topcon Pinnacle ver 1.0, Topcon Tools ver. 8.0, Trimble Business Center)
Evaluating GAIA performances on eclipsing binaries. II. Orbits and stellar parameters for V781 Tau, UV Leo and GK Dra
The orbits and physical parameters of three close, double-lined G0 eclipsing
binaries have been derived combining H_P, V_T, B_T photometry from the
Hipparcos/Tycho mission with 8480-8740 \AA ground-based spectroscopy. The setup
is mimicking the photometric and spectroscopic observations that should be
obtained by GAIA. The binaries considered here are all of G0 spectral type, but
each with its own complications: V781 Tau is an overcontact system with
components of unequal temperature, UV Leo shows occasional surface spots and GK
Dra contains a delta-Scuti variable. Such peculiarities will be common among
binaries to be discovered by GAIA. We find that the values of masses, radii and
temperatures for such stars can be derived with a 1-2% accuracy using the
adopted GAIA-like observing mode.Comment: accepted for publication in Astronomy and Astrophysics, contains 5
Tables and 3 Figures; correction of an important typ
Fem and Von Mises analysis of OSSTEM ® dental implant structural components: evaluation of different direction dynamic loads
Abstract
PURPOSE:
The objective of this investigation is to study prosthodontics and internal components resistance to the masticatory stress and considering different force directions by using Finite Element Method analysis (FEM). The structural materials of the components are usually Titanium alloy grade 4 or 5 and thus, guarantee the integration of the fixture in the bone due to the osteointegration phenomena. Even if the long-term dental implant survival rate is easy to be obtained and confirmed by numerous researches, the related clinical success, due to the alteration of the mechanical and prosthodontics components is still controversial.
METHODS:
By applying engineering systems of investigations like FEM and Von Mises analyses, it has been investigated how dental implant material was held against the masticatory strength during the dynamic masticatory cycles. A three-dimensional system involved fixture, abutment and the connection screws, which were created and analyzed. The elastic features of the materials used in the study were taken from recent literature data.
RESULTS:
Data revealed a different response for both types of devices, although implant neck and dental abutment showed better results for all conditions of loading while the abutment screw represented aweak point of the system.
CONCLUSION:
The data of this virtual model showed all the features of different prosthetic retention systems under the masticatory load. Clinicians should find better prosthetic balance in order to better distribute the stress over the component and to guarantee patients' clinical long-term results
The Temperature Scale of Metal-Rich M Giants Based on TiO Bands: Population Synthesis in the Near Infrared
We have computed a grid of high resolution synthetic spectra for cool stars
(2500<Teff<6000 K) in the wavelength range 6000 -- 10200A, by employing an
updated line list of atomic and molecular lines, together with state-of-the-art
model atmospheres.
As a by-product, by fitting TiO bandheads in spectra of well-known M giants,
we have derived the electronic oscillator strengths of the TiO gamma prime,
delta, epsilon and phi systems. The derived oscillator strenghts for the gamma
prime, epsilon and phi systems differ from the laboratory and ab initio values
found in the literature, but are consistent with the model atmospheres and line
lists employed, resulting in a good match to the observed spectra of M giants
of known parameters.
The behavior of TiO bands as a function of the stellar parameters Teff, log g
and [Fe/H] is presented and the use of TiO spectral indices in stellar
population studies is discussed.Comment: ApJ accepted, 27 pages + 11 figures, AASLatex v4.
Laparoscopic treatment of abdominal unicentric castleman's disease: a case report and literature review.
BACKGROUND:
Castleman's disease is a rare lymphoproliferative disorder of unknown etiology that most commonly presents as a mediastinal nodal mass. It is exceptionally uncommon for Castleman's disease to present in the mesentery and, only 53 cases have ever been described in the literature. Standard treatment for this lymphoproliferative disorder involving a single node is a complete "en bloc" surgical resection which has proven to be a curative approach in almost all cases without recurrence after 20 years of follow up. All 53 reported cases of mesenteric Castleman's disease, except one, were treated with laparotomy.
CASE PRESENTATION:
We report on a case of mesenteric Castleman's disease localized in the mesentery which is the second reported case if its kind and was treated by a laparoscopic-assisted procedure. Our female patient had an uneventful postoperative course and was discharged in the 5th post-operative day. No signs of recurrence were present as evidenced by physical examination and total body CT scan 24 months after the operation. We compare our case with the other reported cases in which Castleman's disease presented as an isolated mass in the abdomen.
CONCLUSION:
Although a rare disease, Unicentric Castleman's disease should always be considered when a solid asymptomatic abdominal mass is occasionally presented. The laparoscopic approach (LA) allows for the achievement of better results than open surgery, including a reduction in postoperative pain and length of hospital stay. In cases of masses of an uncertain nature, LA must be considered the last diagnostic tool and the first treatment one
Evaluating Gaia performances on eclipsing binaries. IV. Orbits and stellar parameters for SV Cam, BS Dra and HP Dra
This is the fourth in a series of papers that aim both to provide reasonable
orbits for a number of eclipsing binaries and to evaluate the expected
performance of Gaia of these objects and the accuracy that is achievable in the
determination of such fundamental stellar parameters as mass and radius. In
this paper, we attempt to derive the orbits and physical parameters for three
eclipsing binaries in the mid-F to mid-G spectral range. As for previous
papers, only the Hp, Vt, Bt photometry from the Hipparcos/Tycho mission and
ground-based radial velocities from spectroscopy in the region 8480-8740 A are
used in the analyses. These data sets simulate the photometric and
spectroscopic data that are expected to be obtained by Gaia, the approved ESA
Cornerstone mission to be launched in 2011. The systems targeted in this paper
are SV Cam, BS Dra and HP Dra. SV Cam and BS Dra have been studied previously,
allowing comparisons of the derived parameters with those from full scale and
devoted ground-based investigations. HP Dra has no published orbital solution.
SV Cam has a beta Lyrae type light curve and the others have Algol-like light
curves. SV Cam has the complication of light curve anomalies, usually
attributed to spots; BS Dra has non-solar metallicity, and HP Dra appears to
have a small eccentricity and a sizeable time derivative in the argument of the
periastron. Thus all three provide interesting and different test cases.Comment: 10 pages, 4 figures, 5 tables, A&A accepte
Asiago eclipsing binaries program. I. V432 Aur
The orbit and physical parameters of the previously unsolved eclipsing binary
V432 Aur, discovered by Hipparcos, have been derived with errors better than 1%
from extensive Echelle spectroscopy and B, V photometry. Synthetic spectral
analysis of both components has been performed, yielding T_eff and log g in
close agreement with the orbital solution, a metallicity [Z/Z_sun]=-0.60 and
rotational synchronization for both components. Direct comparison on the
theoretical L, T_eff plane with the Padova evolutionary tracks and isochrones
for the masses of the two components (1.22 and 1.08 M_sun) provides a perfect
match and a 3.75 Gyr age. The more massive and cooler component is approaching
the base of the giant branch and displays a probable pulsation activity with an
amplitude of Delta V = 0.075 mag and Delta rad.vel. = 1.5 km/sec. With a T_eff
= 6080 K it falls to the red of the nearby instability strip populated by delta
Sct and gamma Dor types of pulsating variables. Orbital modeling reveals a
large and bright surface spot on it. The pulsations activity and the large
spot(s) suggest the presence of macro-turbulent motions in its atmosphere. They
reflect in a line broadening that at cursory inspection could be taken as
indication of a rotation faster than synchronization, something obviously odd
for an old, expanding star.Comment: A&A, 11 pages, accepted Jan 7, 200
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