1,922 research outputs found
The Galactic bulge as seen in optical surveys
The bulge is a region of the Galaxy of tremendous interest for understanding
galaxy formation. However measuring photometry and kinematics in it raises
several inherent issues, such as severe crowding and high extinction in the
visible. Using the Besancon Galaxy model and a 3D extinction map, we estimate
the stellar density as a function of longitude, latitude and apparent magnitude
and we deduce the possibility of reaching and measuring bulge stars with Gaia.
We also present an ongoing analysis of the bulge using the Canada-France-Hawaii
Telescope.Comment: In SF2A-2008: Proceedings of the Annual meeting of the French Society
of Astronomy and Astrophysic
Urine Test Strips to Exclude Cerebral Spinal Fluid Blood
Introduction: Determining the presence or absence of red blood cells (RBC) or their breakdown products in cerebrospinal fluid (CSF) is essential for the evaluation of subarachnoid hemorrhage (SAH) in headache patients. Current methodology for finding blood in the CSF is either spectrophotometric detection of pigment, which is time consuming and labor intensive, or visual assesment of samples for color change (xanthochromia), which is inaccurate. Bayer MultistixÂź urine test strips are designed to test urine for RBC by detecting the presence of hemoglobin. The aim of this pilot study was to evaluate the perfomance of urine reagent test strips for ruling out the presence of RBC in CSF.Methods: We compared color changes on MultistixÂź urine test strips to the standard of spectrophotometric absorbtion at 415nm and initial RBC counts in 138 visually clear CSF samples.Results: We performed Pearson Chi-Square and likelihood ratios on the results and found a correlation between a negative result on the urine test strip and less than 5 RBC per high power field and a spectrophotometric absorbance of less than 0.02% at 415nm in a CSF sample.Conclusion: These results warrant further investigation in the form of a prospective clinical validation as it may alter the emergency department evaluation for SAH. [West J Emerg Med. 2011;12(1):63-66.
High precision microlensing maps of the Galactic bulge
We present detailed maps of the microlensing optical depth and event density
over an area of 195 sq. deg towards the Galactic bulge. The maps are computed
from synthetic stellar catalogues generated from the Besancon Galaxy Model,
which comprises four stellar populations and a three-dimensional extinction map
calibrated against the Two-Micron All-Sky Survey. The optical depth maps have a
resolution of 15 arcminutes, corresponding to the angular resolution of the
extinction map. We compute optical depth and event density maps for all
resolved sources above I=19, for unresolved (difference image) sources
magnified above this limit, and for bright standard candle sources in the
bulge. We show that the resulting optical depth contours are dominated by
extinction effects, exhibiting fine structure in stark contrast to previous
theoretical optical depth maps. Optical depth comparisons between Galactic
models and optical microlensing survey measurements cannot safely ignore
extinction or assume it to be smooth. We show how the event distribution for
hypothetical J and K-band microlensing surveys, using existing ground-based
facilities such as VISTA, UKIRT or CFHT, would be much less affected by
extinction, especially in the K band. The near infrared provides a substantial
sensitivity increase over current I-band surveys and a more faithful tracer of
the underlying stellar distribution, something which upcoming variability
surveys such as VVV will be able to exploit. Synthetic population models offer
a promising way forward to fully exploit large microlensing datasets for
Galactic structure studies.Comment: 8 pages, submitted to MNRA
The Milky Way's external disc constrained by 2MASS star counts
Context. Thanks to recent large scale surveys in the near infrared such as
2MASS, the galactic plane that most suffers from extinction is revealed and its
overall structure can be studied. Aims. This work aims at constraining the
structure of the Milky Way external disc as seen in 2MASS data, and in
particular the warp. Methods. We use the Two Micron All Sky Survey (hereafter
2MASS) along with the Stellar Population Synthesis Model of the Galaxy,
developed in Besancon, to constrain the external disc parameters such as its
scale length, its cutoff radius, and the slope of the warp. In order to
properly interpret the observations, the simulated stars are reddened using a
three dimensional extinction map. The shape of the stellar warp is then
compared with previous results and with similar structures in gas and dust.
Results. We find new constraints on the stellar disc, which is shown to be
asymmetrical, similar to observations of HI. The positive longitude side is
found to be easily modelled with a S shape warp but with a slope significantly
smaller than the slope seen in the HI warp. At negative longitudes, the disc
presents peculiarities which are not well reproduced by any simple model.
Finally, comparing with the warp seen in the dust, it seems to follow a slope
intermediate between the gas and the stars.Comment: 9 pages. Accepted for publication in Astronomy and Astrophysic
Grasping the Links in the Chain: Understanding the Unintended Consequences of International Counter-Narcotics Measures for the EU
No abstract available
Deep K_s-near-infrared Surface Photometry of 80 Dwarf Irregular Galaxies in the Local Volume
We present deep near-infrared (K_s) images and surface photometry for 80 dwarf irregular galaxies (dIs) within ~5 Mpc of the Milky Way. The galaxy images were obtained at five different facilities between 2004 and 2006. The image reductions and surface photometry have been performed using methods specifically designed for isolating faint galaxies from the high and varying near-infrared sky level. Fifty-four of the 80 dIs have surface brightness profiles which could be fit to a hyperbolic-secant (sech) function, while the remaining profiles could be fit to the sum of a sech and a Gaussian function. From these fits, we have measured central surface brightnesses, scale lengths, and integrated magnitudes. This survey is part of a larger study of the connection between large-scale structure and the global properties of dIs, the hypothesized building-blocks of more massive galaxies
Scotland Registry for Ankylosing Spondylitis (SIRAS) â Protocol
Funding SIRAS was funded by unrestricted grants from Pfizer and AbbVie. The project was reviewed by both companies, during the award process, for Scientific merit, to ensure that the design did not compromise patient safety, and to assess the global regulatory implications and any impact on regulatory strategy.Publisher PD
The Extinction and Distance of Maffei 1
We have obtained low- and high-resolution spectra of the core of the
highly-reddened elliptical galaxy Maffei 1. From these data, we have obtained
the first measurement of the Mg2 index, and have measured the velocity
dispersion and radial velocity with improved accuracy. To evaluate the
extinction, a correlation between the Mg2 index and effective V-I colour has
been established for elliptical galaxies. Using a new method for correcting for
effective wavelength shifts, we find A_V = 4.67 +/- 0.19 mag, which is lower by
0.4 mag than previously thought. To establish the distance, the Fundamental
Plane for elliptical galaxies has been constructed in I. The velocity
dispersion of Maffei 1, measured to be 186.8 +/- 7.4 km/s, in combination with
modern wide-field photometry in I, leads to a distance of 2.92 +/- 0.37 Mpc.
The Dn-sigma relation, which is independently calibrated, gives 3.08 +/- 0.85
Mpc and 3.23 +/- 0.67 Mpc from photometry in B and K`, respectively. The
weighted mean of the three estimates is 3.01 +/- 0.30 Mpc. The distance and
luminosity make Maffei 1 the nearest giant elliptical galaxy. The radial
velocity of Maffei 1 is +66.4 +/- 5.0 km/s, significantly higher than the
accepted value of -10 km/s. The Hubble distance corresponding to the mean
velocity of Maffei 1, Maffei 2 and IC342 is 3.5 Mpc. Thus, it is unlikely that
Maffei 1 has had any influence on Local Group dynamics
The large scale dust lanes of the Galactic bar
(abridged) By comparing the distribution of dust and gas in the central
regions of the Galaxy, we aim to obtain new insights into the properties of the
offset dust lanes leading the bar's major axis in the Milky Way. On the one
hand, the molecular emission of the dust lanes is extracted from the observed
CO l-b-V distribution according to the interpretation of a dynamical model. On
the other hand, a three dimensional extinction map of the Galactic central
region constructed from near-infrared observations is used as a tracer of the
dust itself and clearly reveals dust lanes in its face-on projection.
Comparison of the position of both independent detections of the dust lanes is
performed in the (l, b) plane. These two completely independent methods are
used to provide a coherent picture of the dust lanes in the Milky Way bar. In
both the gas and dust distributions, the dust lanes are found to be out of the
Galactic plane, appearing at negative latitudes for l > 0 deg and at positive
latitudes for l < 0 deg. However, even though there is substantial overlap
between the two components, they are offset from one another with the dust
appearing to lie closer to the b = 0 deg plane. Two scenarios are proposed to
explain the observed offset. The first involves grain destruction by the bar
shock and reformation downstream. Due to the decrease in velocity caused by the
shock, this occurs at lower z. The second assumes that the gas and dust remain
on a common tilted plane, but that the molecular gas decouples from the Milky
Way's magnetic field, itself strong enough to resist the shear of the bar's
shock. The diffuse gas and dust remain coupled to the field and are carried
further downstream. This second scenario has recently been suggested in order
to explain observations of the barred galaxy NGC 1097.Comment: 4 pages, 5 figures, accepted for publication in Astronomy and
Astrophysics letter
Does the revised cardiac risk index predict cardiac complications following elective lung resection?
Background:
Revised Cardiac Risk Index (RCRI) score and Thoracic Revised Cardiac Risk Index (ThRCRI) score were developed to predict the risks of postoperative major cardiac complications in generic surgical population and thoracic surgery respectively. This study aims to determine the accuracy of these scores in predicting the risk of developing cardiac complications including atrial arrhythmias after lung resection surgery in adults.
Methods:
We studied 703 patients undergoing lung resection surgery in a tertiary thoracic surgery centre. Observed outcome measures of postoperative cardiac morbidity and mortality were compared against those predicted by risk.
Results:
Postoperative major cardiac complications and supraventricular arrhythmias occurred in 4.8% of patients. Both index scores had poor discriminative ability for predicting postoperative cardiac complications with an area under receiver operating characteristic (ROC) curve of 0.59 (95% CI 0.51-0.67) for the RCRI score and 0.57 (95% CI 0.49-0.66) for the ThRCRI score.
Conclusions:
In our cohort, RCRI and ThRCRI scores failed to accurately predict the risk of cardiac complications in patients undergoing elective resection of lung cancer. The British Thoracic Society (BTS) recommendation to seek a cardiology referral for all asymptomatic pre-operative lung resection patients withâ>â3 RCRI risk factors is thus unlikely to be of clinical benefit
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