3,568 research outputs found
Daily variability of Ceres' Albedo detected by means of radial velocities changes of the reflected sunlight
Bright features have been recently discovered by Dawn on Ceres, which extend
previous photometric and Space Telescope observations. These features should
produce distortions of the line profiles of the reflected solar spectrum and
therefore an apparent radial velocity variation modulated by the rotation of
the dwarf planet. Here we report on two sequences of observations of Ceres
performed in the nights of 31 July, 26-27 August 2015 by means of the
high-precision HARPS spectrograph at the 3.6-m La Silla ESO telescope. The
observations revealed a quite complex behaviour which likely combines a radial
velocity modulation due to the rotation with an amplitude of approx +/- 6 m/s
and an unexpected diurnal effect. The latter changes imply changes in the
albedo of Occator's bright features due to the blaze produced by the exposure
to solar radiation. The short-term variability of Ceres' albedo is on
timescales ranging from hours to months and can both be confirmed and followed
by means of dedicated radial velocity observations.Comment: 5 pag, 1fig, two tables, MNRAS Letters 201
Isotope Spectroscopy
The measurement of isotopic ratios provides a privileged insight both into
nucleosynthesis and into the mechanisms operating in stellar envelopes, such as
gravitational settling. In this article, we give a few examples of how isotopic
ratios can be determined from high-resolution, high-quality stellar spectra. We
consider examples of the lightest elements, H and He, for which the isotopic
shifts are very large and easily measurable, and examples of heavier elements
for which the determination of isotopic ratios is more difficult. The presence
of 6Li in the stellar atmospheres causes a subtle extra depression in the red
wing of the 7Li 670.7 nm doublet which can only be detected in spectra of the
highest quality. But even with the best spectra, the derived Li abundance
can only be as good as the synthetic spectra used for their interpretation. It
is now known that 3D non-LTE modelling of the lithium spectral line profiles is
necessary to account properly for the intrinsic line asymmetry, which is
produced by convective flows in the atmospheres of cool stars, and can mimic
the presence of 6Li. We also discuss briefly the case of the carbon isotopic
ratio in metal-poor stars, and provide a new determination of the nickel
isotopic ratios in the solar atmosphere.Comment: AIP Thinkshop 10 "High resolution optical spectroscopy", invited
talk, AN in pres
Nuclear matter hole spectral function in the Bethe-Brueckner-Goldstone approach
The hole spectral function is calculated in nuclear matter to assess the
relevance of nucleon-nucleon short range correlations. The calculation is
carried out within the Brueckner scheme of many-body theory by using several
nucleon-nucleon realistic interactions. Results are compared with other
approaches based on variational methods and transport theory. Discrepancies
appear in the high energy region, which is sensitive to short range
correlations, and are due to the different many-body treatment more than to the
specific N-N interaction used. Another conclusion is that the momentum
dependence of the G-matrix should be taken into account in any self consistent
approach.Comment: 7 pages, 5 figure
CXCR4 pos circulating progenitor cells coexpressing monocytic and endothelial markers correlating with fibrotic clinical features are present in the peripheral blood of patients affected by systemic sclerosis
There is still controversy regarding the role of circulating endothelial and
progenitor cells (CECs/CEPs) in the pathogenesis of systemic sclerosis (SSc).
Using a sequential Boolean gating strategy based on a 4-color flow cytometric
protocol, an increased number of CD31(pos)/CD184(pos)(CXCR4)/CD34(pos)/CD45(pos)
and CD31(pos)/CD117(pos) (c-kit-R) /CD34(pos)/ CD45(pos) hematopoietic
circulating progenitor cells (HCPCs) was detected in SSc patients compared with
healthy subjects. In SSc, no circulating mature and progenitor endothelial cells
were observed, while an enhanced generation of erythroid progenitor cells was
found to be correlated with the presence of CD117+ HCPCs. The presence of freshly
detected CXCR4posHCPC was correlated either to the in vitro cultured
spindle-shaped endothelial like cells (SELC) with an endo/myelomonocytic profile
or to SDF-1 and VEGF serum level. These data are related to more fibrotic
clinical features of the disease, thus supporting a possible role of these cells
in fibrosis
Curiouser and curiouser: The peculiar chemical composition of the Li: The Na-rich star in ω Centauri
We present a multi-instrument spectroscopic analysis of the unique Li- and Na-rich giant star #25664 in ω Centauri, using spectra acquired with FLAMES-GIRAFFE, X-shooter, UVES, and HARPS. Li and Na abundances have been derived from the UVES spectrum using transitions weakly sensitive to non-local thermodynamic equilibrium and assumed isotopic ratios. This new analysis confirms the surprising Li and Na abundances of this star (A(Li)NLTE = +2.71 ± 0.07 dex, [Na/Fe]NLTE = +1.00 ± 0.05 dex). Additionally, we provide new pieces of evidence for its chemical characterisation. The 12C13C isotopic ratio (15 ± 2) shows that this star has not yet undergone the extra-mixing episode usually associated with the red giant branch bump. Therefore, we can rule out the scenario of efficient deep extra mixing during the red giant branch phase envisaged to explain the high Li and Na abundances. Also, the star exhibits high abundances of both C and N ([C/Fe] = +0.45 ± 0.16 dex and [N/Fe] = +0.99 ± 0.20 dex), which is not compatible with the typical C-N anti-correlation observed in globular cluster stars. We found evidence of a radial velocity variability in #25664, suggesting that the star could be part of a binary system, likely having accreted material from a more massive companion when the latter was evolving in the asymptotic giant branch (AGB) phase. Viable candidates for the donor star are AGB stars with 3-4 M⊙ and super-AGB stars (~7-8 M⊙), both of which are able to produce Li- and Na-rich material. Alternatively, the star could have formed from the pure ejecta of a super-AGB star before the dilution with primordial gas occurred
Millstones as indicators of relative sea-level changes in northern Sicily and southern Calabria coast lines, Italy
New data are presented for late Holocene relative sea-level changes in two coastal sites of Sicily and
Calabria, southern Italy. Reconstructions are based on precise measurements of submerged archaeological
remains that are valuable indicators of past sea-level position. The archaeological remains are
millstone quarries carved on sandstone coastal rocks and nowadays partially submerged which, to the
authors’ knowledge, are used for the first time as sea-level markers. Millstones of similar typology are
located on the coast of Capo d’Orlando (northern Sicily) and Capo dell’Armi (southern Calabria). When
the archeologically-based sea-level position is compared with the shoreline elevation provided by
geological markers (Holocene beachrock, Late Pleistocene marine terraces), a refined understanding of
relative sea-level changes and rates of vertical tectonic movements for these coastline locations is gained
Human, All Too Human? An All-Around Appraisal of the “Artificial Intelligence Revolution” in Medical Imaging
Artificial intelligence (AI) has seen dramatic growth over the past decade, evolving from a niche super specialty computer application into a powerful tool which has revolutionized many areas of our professional and daily lives, and the potential of which seems to be still largely untapped. The field of medicine and medical imaging, as one of its various specialties, has gained considerable benefit from AI, including improved diagnostic accuracy and the possibility of predicting individual patient outcomes and options of more personalized treatment. It should be noted that this process can actively support the ongoing development of advanced, highly specific treatment strategies (e.g., target therapies for cancer patients) while enabling faster workflow and more efficient use of healthcare resources. The potential advantages of AI over conventional methods have made it attractive for physicians and other healthcare stakeholders, raising much interest in both the research and the industry communities. However, the fast development of AI has unveiled its potential for disrupting the work of healthcare professionals, spawning concerns among radiologists that, in the future, AI may outperform them, thus damaging their reputations or putting their jobs at risk. Furthermore, this development has raised relevant psychological, ethical, and medico-legal issues which need to be addressed for AI to be considered fully capable of patient management. The aim of this review is to provide a brief, hopefully exhaustive, overview of the state of the art of AI systems regarding medical imaging, with a special focus on how AI and the entire healthcare environment should be prepared to accomplish the goal of a more advanced human-centered world
3D Patient-Specific Virtual Models for Presurgical Planning in Patients with Recto-Sigmoid Endometriosis Nodules: A Pilot Study
Background and Objective: In recent years, 3D printing has been used to support surgical planning or to guide intraoperative procedures in various surgical specialties. An improvement in surgical planning for recto-sigmoid endometriosis (RSE) excision might reduce the high complication rate related to this challenging surgery. The aim of this study was to build novel presurgical 3D models of RSE nodules from magnetic resonance imaging (MRI) and compare them with intraoperative findings. Materials and Methods: A single-center, observational, prospective, cohort, pilot study was performed by enrolling consecutive symptomatic women scheduled for minimally invasive surgery for RSE between November 2019 and June 2020 at our institution. Preoperative MRI were used for building 3D models of RSE nodules and surrounding pelvic organs. 3D models were examined during multi-disciplinary preoperative planning, focusing especially on three domains: degree of bowel stenosis, nodule's circumferential extension, and bowel angulation induced by the RSE nodule. After surgery, the surgeon was asked to subjectively evaluate the correlation of the 3D model with the intra-operative findings and to express his evaluation as "no correlation", "low correlation", or "high correlation" referring to the three described domains. Results: seven women were enrolled and 3D anatomical virtual models of RSE nodules and surrounding pelvic organs were generated. In all cases, surgeons reported a subjective "high correlation" with the surgical findings. Conclusion: Presurgical 3D models could be a feasible and useful tool to support surgical planning in women with recto-sigmoidal endometriotic involvement, appearing closely related to intraoperative findings
Curiouser and curiouser: The peculiar chemical composition of the Li: The Na-rich star in ω Centauri
We present a multi-instrument spectroscopic analysis of the unique Li- and Na-rich giant star #25664 in ω Centauri, using spectra acquired with FLAMES-GIRAFFE, X-shooter, UVES, and HARPS. Li and Na abundances have been derived from the UVES spectrum using transitions weakly sensitive to non-local thermodynamic equilibrium and assumed isotopic ratios. This new analysis confirms the surprising Li and Na abundances of this star (A(Li)NLTE = +2.71 ± 0.07 dex, [Na/Fe]NLTE = +1.00 ± 0.05 dex). Additionally, we provide new pieces of evidence for its chemical characterisation. The 12C13C isotopic ratio (15 ± 2) shows that this star has not yet undergone the extra-mixing episode usually associated with the red giant branch bump. Therefore, we can rule out the scenario of efficient deep extra mixing during the red giant branch phase envisaged to explain the high Li and Na abundances. Also, the star exhibits high abundances of both C and N ([C/Fe] = +0.45 ± 0.16 dex and [N/Fe] = +0.99 ± 0.20 dex), which is not compatible with the typical C-N anti-correlation observed in globular cluster stars. We found evidence of a radial velocity variability in #25664, suggesting that the star could be part of a binary system, likely having accreted material from a more massive companion when the latter was evolving in the asymptotic giant branch (AGB) phase. Viable candidates for the donor star are AGB stars with 3-4 M⊙ and super-AGB stars (~7-8 M⊙), both of which are able to produce Li- and Na-rich material. Alternatively, the star could have formed from the pure ejecta of a super-AGB star before the dilution with primordial gas occurred
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