1,489 research outputs found
Gemini spectroscopy of the outer disk star cluster BH176
BH176 is an old metal-rich star cluster. It is spatially and kinematically
consistent with belonging to the Monoceros Ring. It is larger in size and more
distant from the Galactic plane than typical open clusters, and it does not
belong to the Galactic bulge. Our aim is to determine the origin of this unique
object by accurately determining its distance, metallicity, and age. The best
way to reach this goal is to combine spectroscopic and photometric methods. We
present medium-resolution observations of red clump and red giant branch stars
in BH176 obtained with the Gemini South Multi-Object Spectrograph.We derive
radial velocities, metallicities, effective temperatures, and surface gravities
of the observed stars and use these parameters to distinguish member stars from
field objects. We determine the following parameters for BH176:
km/s, , age Gyr, , distance
kpc, -element abundance dex (the
mean of [Mg/Fe], and [Ca/Fe]). BH176 is a member of old Galactic open clusters
that presumably belong to the thick disk. It may have originated as a massive
star cluster after the encounter of the forming thin disk with a high-velocity
gas cloud or as a satellite dwarf galaxy.Comment: 15 pages, 7 fufures, Accepted for publication in Astronomy &
Astrophysic
Introducing the concept of spiral microbeam radiation therapy (spiralMRT).
Motivation With interlaced microbeam radiation therapy (MRT) a first kilovoltage radiotherapy (RT) concept combining spatially fractionated entrance beams and homogeneous dose distribution at the target exists. However, this technique suffers from its high sensitivity to positioning errors of the target relative to the radiation source. With spiral microbeam radiation therapy (spiralMRT), this publication introduces a new irradiation geometry, offering similar spatial fractionation properties as interlaced MRT, while being less vulnerable to target positioning uncertainties.Methods The dose distributions achievable with spiralMRT in a simplified human head geometry were calculated with Monte Carlo simulations based on Geant4 and the dependence of the result on the microbeam pitch, total field size, and photon energy were analysed. A comparison with interlaced MRT and conventional megavoltage tomotherapy was carried out.Results SpiralMRT can deliver homogeneous dose distributions, while using spatially fractionated entrance beams. The valley dose of spiralMRT entrance beams is by up to 40% lower than the corresponding tomotherapy dose, thus indicating a better normal tissue sparing. The optimum photon energy is found to be around [Formula: see text].Conclusions SpiralMRT is a promising approach to delivering homogeneous dose distributions with spatially fractionated entrance beams, possibly decreasing normal tissue side effects in hypofractionated RT
CASE REPORT. BILATERAL CONSOLIDATION OF THE LUNGS IN A PRETERM INFANT: AN UNUSUAL CENTRAL VENOUS CATHETER COMPLICATIO
NGC 6438 : A triple system?
We provide photographic and photoelectric information as well as CCD imaging and medium resolution spectroscopy on this system located at a distance of -32 Mpc. The SO galaxy has twisted isophotes which also show changes in the ellipticity. Profiles toward the north of this galaxy are 0.1 and 0.2 magnitudes brighter in the B and V bands respectively, than in any other direction, probably due to the presence of dust in the Irregular system. Several blue regions (B-V = 0.26 - 0.40) are found in the Irregular object indicating ongoing star formation. One of these regions is located in an extreme of the northern arm, its luminosity being similar to that of the nucleus which is very close to it. Analysis of the spectra shows typical absorption lines and a weak [Nil] emission in the SO galaxy whereas Ha, [Nil] and [SII] emission lines are observed both in the nucleus and in the blue region mentioned above. We determine a high reddening E(B-V) = 1.4 in the nuclear region of this system. Rotation curves show a different behavior for the nucleus and the blue region, which have Vmax >180 km/sec and Vmax = 80 km/sec respectively. All tins evidence could support the idea that NGC 6438 is an interacting triplet, one SO galaxy and two disk galaxies undergoing a merger.Asociación Argentina de Astronomí
Prone positioning and convalescent plasma therapy in a critically ill pregnant woman with COVID-19
Prone positioning is feasible in pregnancy and may have contributed to the positive outcome in this case. Doctors should not be reluctant to move a patient to a prone position just because they are pregnant
The merging/AGN connection II. Ionization of the circumnuclear regions
We report the first results of a study of a sample of 20 galaxy
mergers/interacting systems, using the VIMOS and PMAS integral field
spectrographs. For each object, we extracted the integrated spectrum of the
central regions and analyzed the ionization state using classical diagnostic
diagrams (Veilleux & Osterbrock 1987). There is evidence of AGN ionization in 4
of the objects, i.e. 20% of the sample, a considerably higher fraction than
found in previous studies ~4%Comment: 4 pages, 2 figures, accepted for publishing in A&A Letter
Flexibility properties in Complex Analysis and Affine Algebraic Geometry
In the last decades affine algebraic varieties and Stein manifolds with big
(infinite-dimensional) automorphism groups have been intensively studied.
Several notions expressing that the automorphisms group is big have been
proposed. All of them imply that the manifold in question is an
Oka-Forstneri\v{c} manifold. This important notion has also recently merged
from the intensive studies around the homotopy principle in Complex Analysis.
This homotopy principle, which goes back to the 1930's, has had an enormous
impact on the development of the area of Several Complex Variables and the
number of its applications is constantly growing. In this overview article we
present 3 classes of properties: 1. density property, 2. flexibility 3.
Oka-Forstneri\v{c}. For each class we give the relevant definitions, its most
significant features and explain the known implications between all these
properties. Many difficult mathematical problems could be solved by applying
the developed theory, we indicate some of the most spectacular ones.Comment: thanks added, minor correction
A CH star in the globular cluster NGC 6426
We report on the serendipitous discovery of a carbon star near the centre of
the low-metallicity globular cluster NGC 6426. We determined its membership and
chemical properties using medium-resolution spectra. The radial velocity of
-159 km/s makes it a member of the cluster. We used photometric data from the
literature and the COMARCS stellar atmospheric models to derive its luminosity,
effective temperature, surface gravity, metallicity, and approximate C, N, and
O abundance ratios. According to these properties, we suggest that this star is
a genuine carbon rich low-metallicity AGB star.Comment: 5 pages, accepted for publication in MNRA
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