484 research outputs found
A Student-Led Campaign to Help Tackle Neglected Tropical Diseases
The authors propose that innovative student-led campaigns to address neglected diseases can and do make a practical difference
The black hole mass distribution in early-type galaxies: cusps in HST photometry interpreted through adiabatic black hole growth
The surface brightness profiles of early-type galaxies have central cusps.
Two characteristic profile types are observed with HST: `core' profiles have a
break at a resolved radius and logarithmic cusp slope gamma < 0.3 inside that
radius; `power-law' profiles have no clear break and gamma > 0.3. With few
exceptions, galaxies with M_V
-20.5 have power-law profiles. Both profile types occur in galaxies with -22 <
M_V < -20.5. We show that these results are consistent with the hypothesis
that: (i) all early-type galaxies have black holes (BHs) that grew
adiabatically in homogeneous isothermal cores; and (ii) these `progenitor'
cores followed scaling relations similar to those of the fundamental plane.
The models studied here are the ones first proposed by Young. Models with BH
masses and progenitor cores that obey established scaling relations predict (at
Virgo) that galaxies with M_V < -21.2 have core profiles and galaxies with M_V
> -21.2 have power-law profiles. This reproduces both the sense and the
absolute magnitude of the observed transition. Intrinsic scatter in BH and
galaxy properties can explain why both types of galaxies are observed around
the transition magnitude. The observed bimodality in cusp slopes may be due to
a bimodality in M_bh/L, with rapidly rotating disky galaxies having larger
M_bh/L than slowly rotating boxy galaxies.
Application to individual galaxies with HST photometry yields a roughly
linear correlation between BH mass and V-band galaxy luminosity, log M_bh =
-1.83 + log L (solar units). This agrees with the average relation for nearby
galaxies with kinematically determined BH masses, and also with predictions
from quasar statistics (shortened abstract).Comment: 41 pages, LaTeX, with 11 PostScript figures. Submitted to the
Astronomical Journal. Postscript version also available from
http://sol.stsci.edu/~marel/abstracts/abs_R23.htm
Centro de Estudos Municipais e Metropolitanos: CEMME
1 fôlder (4 p.) : color. ; 14 x 21 cmFôlder de apresentação do "Centro de Estudos Municipais e Metropolitanos (CEMME)", departamento da Fundação João Pinheiro (FJP), mostrando seus objetivos e projetos para o segundo semestre de 1996 e primeiro semestre de 1997
QSO's from Galaxy Collisions with Naked Black Holes
In the now well established conventional view (see Rees [1] and references
therein), quasi-stellar objects (QSOs) and related active galactic nuclei (AGN)
phenomena are explained as the result of accretion of plasma onto giant black
holes which are postulated to form via gravitational collapse of the high
density regions in the centers of massive host galaxies. This model is
supported by a wide variety of indirect evidence and seems quite likely to
apply at least to some observed AGN phenomena. However, one surprising set of
new Hubble Space Telescope (HST) observations [2-4] directly challenges the
conventional model, and the well known evolution of the QSO population raises
some additional, though not widely recognized, difficulties. We propose here an
alternative possibility: the Universe contains a substantial independent
population of super-massive black holes, and QSO's are a phenomenon that occurs
due to their collisions with galaxies or gas clouds in the intergalactic medium
(IGM). This hypothesis would naturally explain why the QSO population declines
very rapidly towards low redshift, as well as the new HST data.Comment: plain TeX file, no figures, submitted to Natur
Young stars and non-stellar emission in the aligned radio galaxy 3C 256
We present ground-based images of the z=1.824 radio galaxy 3C 256 in the
standard BVRIJHK filters and an interference filter centered at 8800A, a Hubble
Space Telescope image in a filter dominated by Ly-alpha emission (F336W), and
spectra covering rest-frame wavelengths from Ly-alpha to [O III] 5007. Together
with published polarimetry observations, we use these to decompose the overall
spectral energy distribution into nebular continuum emission, scattered quasar
light, and stellar emission. The nebular continuum and scattered light together
comprise half (one third) of the V-band (K-band) light within a 4-arcsec
aperture, and are responsible for the strong alignment between the
optical/near-infrared light and the radio emission. The stellar emission is
dominated by a population estimated to be 100-200 Myr old (assuming a Salpeter
IMF), and formed in a short burst with a peak star formation rate of 1-4x10^3
Msun/yr. The total stellar mass is estimated to be no more than 2x10^{11} Msun,
which is far less than other luminous radio galaxies at similar redshifts, and
suggests that 3C 256 will undergo further star formation or mergers.Comment: 35 pages including 10 figures; to appear in Nov 10 Ap
Massive Ellipticals at High Redshift: NICMOS Imaging of Z~1 Radio Galaxies
We present deep, continuum images of eleven high-redshift (0.811 < z < 1.875)
3CR radio galaxies observed with NICMOS. Our images probe the rest-frame
optical light where stars are expected to dominate the galaxy luminosity. The
rest-frame UV light of eight of these galaxies demonstrates the well-known
``alignment effect''. Most of the radio galaxies have rounder, more symmetric
morphologies at rest-frame optical wavelengths. Here we show the most direct
evidence that in most cases the stellar hosts are normal elliptical galaxies
with de Vaucouleurs law light profiles. For a few galaxies very faint traces of
the UV-bright aligned component are also visible in the infrared images. We
derive both the effective radius and surface-brightness for nine of eleven
sample galaxies by fitting surface-brightness models to them. We find their
sizes are similar to those of local FRII radio source hosts and are in general
larger than other local galaxies. The derived host galaxy luminosities are very
high and lie at the bright end of luminosity functions constructed at similar
redshifts. The galaxies in our sample are also brighter than the rest-frame
size--surface-brightness locus defined by the low-redshift sources. Passive
evolution roughly aligns the z ~ 1 galaxies with the low-redshift samples. The
optical host is sometimes centered on a local minimum in the rest-frame UV
emission, suggesting the presence of substantial dust obscuration. We also see
good evidence of nuclear point sources in three galaxies. Overall, our results
are consistent with the hypothesis that these galaxies have already formed the
bulk of their stars at redshifts greater than z >~ 2, and that the AGN
phenomenon takes place within otherwise normal, perhaps passively evolving,
galaxies. (abridged)Comment: 28 pages, 14 figures, accepted to ApJ. Uses AASTEX and emulateapj
A Faraday Rotation Search for Magnetic Fields in Large Scale Structure
Faraday rotation of radio source polarization provides a measure of the
integrated magnetic field along the observational lines of sight. We compare a
new, large sample of Faraday rotation measures (RMs) of polarized extragalactic
sources with galaxy counts in Hercules and Perseus-Pisces, two nearby
superclusters. We find that the average of RMs in these two supercluster areas
are larger than in control areas in the same galactic latitude range. This is
the first RM detection of magnetic fields that pervade a supercluster volume,
in which case the fields are at least partially coherent over several
megaparsecs. Even the most conservative interpretation of our observations,
according to which Milky Way RM variations mimic the background supercluster
galaxy overdensities, puts constraints on the IGM magneto-ionic ``strength'' in
these two superclusters. We obtain an approximate typical upper limit on the
field strength of about 0.3 microGauss l/(500 kpc), when we combine our RM data
with fiducial estimates of electron density from the environments of giant
radio galaxies, and of the warm-hot intergalactic medium (WHIM).Comment: 8 pages, 3 figures, 1 table, to appear in the Astrophysical Journa
Infrared Images of Distant 3C Radio Galaxies
We have obtained J and K images of radio galaxies with redshifts of up to 3.4, including 3C 41, 54, 124, 194, 256, 257, 265, 294, 326.1, 356, 437, 441, & 454.1, and B2 0902+34. The observations were made using the Infrared Imager (IRIM) on the KPNO 4m telescope. Stellar image sizes (FWHM) are from 0.85 to 1.2 arcseconds, roughly 10 kpc for H_0=50. The limiting sensitivity (3σ in 1 square arcsecond) of the deepest images is approximately K=21 (2.7μJy)
Self-medication amongst pregnant women in a tertiary care teaching hospital in India
Background: Self-medication is a popular practice in developing countries where there is no strict regulation of drugs sold in local pharmacies. General public is usually unaware of the adverse effects of drugs used for common illness and continue using them without prescription during pregnancy. This study was carried out to know the extent of self-medication practised by pregnant women and various factors associated with it.Methods: A questionnaire based, cross-sectional study of pregnant women visiting the OB GYN-OPD of a tertiary care teaching hospital was conducted. 303 eligible subjects were questioned and statistical analysis was carried out.Results: Total 16.5% women were found to be self-medicating during pregnancy for common conditions like headache (26%), fever (23%) and common cold (19%). Odds Ratio between the self-medicating and non-self-medicating groups for variables like age (<25 years; ≥25 years), education (illiterate; literate) and gestational age (<20 weeks; ≥20 weeks) are 1.6, 2 and 1.73 respectively. Women with a history of self-medicating before pregnancy were significantly more likely to continue doing so during pregnancy (p value <0.00001).Conclusions: A significant proportion of pregnant women have been found to self-medicate without knowing the adverse effects of the drug used. Thus, spreading awareness against this health-predicament is necessary
Adaptive design of a clinical decision support tool: What the impact on utilization rates means for future CDS research
© The Author(s) 2019. OBJECTIVE: We employed an agile, user-centered approach to the design of a clinical decision support tool in our prior integrated clinical prediction rule study, which achieved high adoption rates. To understand if applying this user-centered process to adapt clinical decision support tools is effective in improving the use of clinical prediction rules, we examined utilization rates of a clinical decision support tool adapted from the original integrated clinical prediction rule study tool to determine if applying this user-centered process to design yields enhanced utilization rates similar to the integrated clinical prediction rule study. MATERIALS & METHODS: We conducted pre-deployment usability testing and semi-structured group interviews at 6 months post-deployment with 75 providers at 14 intervention clinics across the two sites to collect user feedback. Qualitative data analysis is bifurcated into immediate and delayed stages; we reported on immediate-stage findings from real-time field notes used to generate a set of rapid, pragmatic recommendations for iterative refinement. Monthly utilization rates were calculated and examined over 12 months. RESULTS: We hypothesized a well-validated, user-centered clinical decision support tool would lead to relatively high adoption rates. Then 6 months post-deployment, integrated clinical prediction rule study tool utilization rates were substantially lower than anticipated based on the original integrated clinical prediction rule study trial (68%) at 17% (Health System A) and 5% (Health System B). User feedback at 6 months resulted in recommendations for tool refinement, which were incorporated when possible into tool design; however, utilization rates at 12 months post-deployment remained low at 14% and 4% respectively. DISCUSSION: Although valuable, findings demonstrate the limitations of a user-centered approach given the complexity of clinical decision support. CONCLUSION: Strategies for addressing persistent external factors impacting clinical decision support adoption should be considered in addition to the user-centered design and implementation of clinical decision support
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