3,642 research outputs found
Structure and Feedback in 30 Doradus I: Observations
We have completed a a new optical imaging and spectrophotometric survey of a
140 x 80 pc region of 30 Doradus centered on R136, covering key optical
diagnostic emission lines including \Ha, \Hb, \Hg, [O III]
4363, 4959, 5007, [N II] 6548, 6584, [S II]
6717, 6731 [S III] 6312 and in some locations [S III]
9069. We present maps of fluxes and intensity ratios for these lines,
and catalogs of isolated ionizing stars, elephant-trunk pillars, and edge-on
ionization fronts. The final science-quality spectroscopic data products are
available to the public. Our analysis of the new data finds that, while stellar
winds and supernovae undoubtedly produce shocks and are responsible for shaping
the nebula, there are no global spectral signatures to indicate that shocks are
currently an important source of ionization. We conclude that the considerable
region covered by our survey is well described by photoionization from the
central cluster where the ionizing continuum is dominated by the most massive O
stars. We show that if 30 Dor were viewed at a cosmological distance, its
integrated light would be dominated by its extensive regions of lower
surface-brightness rather than by the bright, eye-catching arcs.Comment: 42 pages, 16 figures, Accepted for publication in ApJ
BUILDING PERFORMANCE AND OCCUPANCY EVALUATION FOR PUBLIC BUILDING STOCK MANAGEMENT: A STATE OF THE ART
A novel ultrafast-low-dose computed tomography protocol allows concomitant coronary artery evaluation and lung cancer screening
BACKGROUND:Cardiac computed tomography (CT) is often performed in patients who are at high risk for lung cancer in whom screening is currently recommended. We tested diagnostic ability and radiation exposure of a novel ultra-low-dose CT protocol that allows concomitant coronary artery evaluation and lung screening.
METHODS: We studied 30 current or former heavy smoker subjects with suspected or known coronary artery disease who underwent CT assessment of both coronary arteries and thoracic area (Revolution CT, General Electric). A new ultrafast-low-dose single protocol was used for ECG-gated helical acquisition of the heart and the whole chest. A single IV iodine bolus (70-90 ml) was used. All patients with CT evidence of coronary stenosis underwent also invasive coronary angiography.
RESULTS: All the coronary segments were assessable in 28/30 (93%) patients. Only 8 coronary segments were not assessable in 2 patients due to motion artefacts (assessability: 98%; 477/485 segments). In the assessable segments, 20/21 significant stenoses (> 70% reduction of vessel diameter) were correctly diagnosed. Pulmonary nodules were detected in 5 patients, thus requiring to schedule follow-up surveillance CT thorax. Effective dose was 1.3 ± 0.9 mSv (range: 0.8-3.2 mSv). Noteworthy, no contrast or radiation dose increment was required with the new protocol as compared to conventional coronary CT protocol.
CONCLUSIONS:The novel ultrafast-low-dose CT protocol allows lung cancer screening at time of coronary artery evaluation. The new approach might enhance the cost-effectiveness of coronary CT in heavy smokers with suspected or known coronary artery disease
A deep Chandra, VLA and Spitzer IRAC study of the very low luminosity nucleus of the elliptical NGC821
The relatively nearby (distance=24.1 Mpc) elliptical galaxy NGC821 hosts an
extreme example of a quiescent central massive black hole, for which deep
Chandra observations revealed a nuclear source for the first time (with L(2-10
keV)/L_Edd ~ 3.6X10^{-8}). We present here a multiwavelength study of this
nucleus, including VLA observations that detect a radio counterpart to the
Chandra nuclear source at 1.4 GHz, with a flux density of 127 m and
possibly a flat spectral shape; we also consider new Spitzer IRAC observations
and archival HST images. With these data we discuss possible scenarios for the
accretion modalities of the sole material that is available for fuelling, i.e.,
the stellar mass losses steadily replenishing the circumnuclear region. The
final stages of accretion could be radiatively inefficient and coupled to a
compact nuclear jet/outfow. The stellar mass losses could instead end up in a
standard disc only if a Compton-thick AGN is present. Two extended sources
detected by Chandra close to the nucleus could be due to several unresolved
knots in a jet. If a jet is present, though, its kinetic energy would be only a
very small fraction of the energy associated with the rest mass of the material
being accreted. Starformation close to the nucleus is not shown by the
available data. Deeper NICMOS, radio and far-IR observations should further
constrain the accretion process.Comment: 32 pages, 4 figures; minor changes; accepted for publication in ApJ.
This is the companion paper of astro-ph/070163
Enhanced Optical Cooling of Ion Beams for LHC
The possibility of the enhanced optical cooling (EOC) of Lead ions in LHC is
investigated. Non-exponential feature of cooling and requirements to the ring
lattice, optical and laser systems are discussed. Comparison with optical
stochastic cooling (OSC) is represented.Comment: 4 page
Implant surfaces exposed to the oral cavity and treated with toothpaste containing oxygen releasing compound : a morphological controlled clinical trial
Aim of the present in vivo study is to assess if a toothpaste containing an oxygen releasing compound (AX) is able to
reduce the biofilm formation on implants with rough surface compared to a control toothpaste, without affecting the microstructure of the tested surface.
Methods: In this double blind, cross-over, controlled clinical trial, a total of fourteen healthy volunteers were recruited. For each
subject, two mandibular splints (test and control) were created with one implant fixed on the right lingual side of the mandibular
arch. The splint was continuously worn for 5 days and the daily hygiene was performed wearing the splint and using the test
(AX) or control toothpaste. Implants were analyzed at scanning-electron-microscopy and at laser profilometer for the assessment of biofilm adhesion (% of areas free from biofilm-FA) and surface changes (morphology and roughness).
Results: FA resulted significantly higher in test than in control implants. No differences were found between groups in term of
biofilm organization, surface microstructure and roughness.
Discussion: Daily use of toothpaste containing AX seems to reduce the amount of biofilm adherent to the rough implant surface
without corrosion or degradation of the titanium surface
Decoupled and inhomogeneous gas flows in S0 galaxies
A recent analysis of the "Einstein" sample of early-type galaxies has
revealed that at any fixed optical luminosity Lb S0 galaxies have lower mean
X-ray luminosity Lx per unit Lb than ellipticals. Following a previous
analytical investigation of this problem (Ciotti & Pellegrini 1996), we have
performed 2D numerical simulations of the gas flows inside S0 galaxies in order
to ascertain the effectiveness of rotation and/or galaxy flattening in reducing
the Lx/Lb ratio. The flow in models without SNIa heating is considerably
ordered, and essentially all the gas lost by the stars is cooled and
accumulated in the galaxy center. If rotation is present, the cold material
settles in a disk on the galactic equatorial plane. Models with a time
decreasing SNIa heating host gas flows that can be much more complex. After an
initial wind phase, gas flows in energetically strongly bound galaxies tend to
reverse to inflows. This occurs in the polar regions, while the disk is still
in the outflow phase. In this phase of strong decoupling, cold filaments are
created at the interface between inflowing and outflowing gas. Models with more
realistic values of the dynamical quantities are preferentially found in the
wind phase with respect to their spherical counterparts of equal Lb. The
resulting Lx of this class of models is lower than in spherical models with the
same Lb and SNIa heating. At variance with cooling flow models, rotation is
shown to have only a marginal effect in this reduction, while the flattening is
one of the driving parameters for such underluminosity, in accordance with the
analytical investigation.Comment: 32 pages LaTex file, plus 5 .ps figures and macro aasms4.sty --
Accepted on Ap
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