118 research outputs found
Prevalence of Intestinal Parasites in Young Quichua Children in the Highlands of Rural Ecuador
The prevalence of intestinal parasites in young Quichua children was assessed in 20 rural communities in the highlands of Ecuador in August 2005. The caregivers of 293 children aged 12–60 months were interviewed about the status of child health, household socioeconomic and environmental factors, and water-use practices and were requested to collect a faecal sample from the study child. Two hundred three (69.3%) of the 293 children provided faecal samples that were tested for parasites. The overall prevalences of infection for specific agents were Entamoeba histolytica or dispar 57.1%, Ascaris lumbricoides 35.5%, Entamoeba coli 34.0%, Giardia intestinalis (lamblia) 21.1%, Hymenolepis nana 11.3%, Cryptosporidium parvum 8.9%, Chilomastix mesnili 1.7%, Hymenolepis diminuta 1.0%, Strongyloides stercoralis 0.7%, and Trichuris trichiura 0.5%. The prevalence of parasites increased with age. Water storage, water treatment, consistent latrine-use, and participation in a community-based clean water project were not strongly associated with the prevalence of intestinal parasites, although having dirt floors was a risk factor for infection with E. histolytica or dispar and G. intestinalis
Herschel and Odin observations of H2O, CO, CH, CH+, and NII in the barred spiral galaxy NGC 1365. Bar-induced activity in the outer and inner circumnuclear tori
The Odin satellite is now into its twentieth year of operation, much
surpassing its design life of two years. One of its major pursuits was the
search for and study of H2O in the Solar System and the Milky Way galaxy.
Herschel has observed the central region of NGC 1365 in two positions, and both
its SPIRE and PACS observations are available in the Herschel Science Archive.
Herschel PACS images have been produced of the 70 and 160 micron infrared
emission from the whole galaxy, and also of the cold dust distribution as
obtained from the ratio of the 160 to 70 micron images. The Herschel SPIRE
observations have been used to produce maps of the 557 GHz o-H2O, 752 GHz
p-H2O, 691 GHz CO(6-5), 1037 GHz CO(9-8), 537 GHz CH, 835 GHz CH+, and the 1461
GHz NII lines; however, these observations have no effective velocity
resolution. Odin has recently observed the 557 GHz o-H2O ground state line in
the central region with high (5 km/s) spectral resolution. The emission and
absorption of H2O at 557 GHz, with a velocity resolution of 5 km/s, has been
marginally detected in NGC 1365 with Odin. The H2O is predominantly located in
a shocked 15" (1.3 kpc) region near some central compact radio sources and
hot-spot HII regions, close to the northeast component of the molecular torus
surrounding the nucleus. An analysis of the H2O line intensities and velocities
indicates that a shock-region is located here. This is corroborated by a
statistical image deconvolution of our SEST CO(3-2) observations, yielding 5"
resolution, and a study of our VLA HI absorption observations. Additionally, an
enticing 20" HI ridge is found to extend south-southeast from the nucleus,
coinciding in position with the southern edge of an OIII outflow cone,
emanating from the nucleus. The molecular chemistry of the shocked central
region is analyzed with special emphasis on the CO, H2O and CH, CH+ results.Comment: 25 pages, 11 figure
A comparison between Pa alpha and H alpha emission: The relation between HII region mean reddening, local gas density and metallicity
We measure reddenings to HII regions in NGC 2903, NGC 1512, M51, NGC 4449 and
NGC 6946 from Hubble Space Telescope Pa alpha and H alpha images. Extinctions
range from A_V ~ 5 - 0 depending upon the galaxy. For the galaxies with HST
images in both lines, NGC 2903, NGC 1512 and M51, the Pa alpha and H alpha
emission are almost identical in morphology which implies that little emission
from bright HII regions is hidden from view by regions of comparatively high
extinction. The scatter in the measured extinctions is only +- 0.5 mag.
We compare the reddenings we measure in five galaxies using the Pa alpha to H
alpha ratios to those measured previously from the Balmer decrement in the LMC
and as a function of radius in M101 and M51. We find that luminosity weighted
mean extinctions of these ensembles of HI regions are correlated with gas
surface density and metallicity. The correlation is consistent with the mean
extinction depending on dust density where the dust to gas mass ratio scales
with the metallicity. This trend is expected if HII regions tend to be located
near the mid-plane of a gas disk and emerge from their parent molecular clouds
soon after birth. In environments with gas densities below a few hundred
Msol/pc^2 star formation rates estimated from integrated line fluxes and mean
extinctions are likely to be fairly accurate.Comment: accepted for publication in A
A New High Resolution CO Map of the inner 2.'5 of M51 I. Streaming Motions and Spiral Structure
[Abridged] The Owens Valley mm-Array has been used to map the CO 1--0
emission in the inner 2'.5 of the grand design spiral galaxy M51 at 2''-3''
resolution. The molecular spiral arms are revealed with unprecedented clarity:
supermassive cloud complexes, Giant Molecular Associations, are for the first
time resolved both along and perpendicular to the arms. Major complexes occur
symmetrically opposite each other in the two major arms. Streaming motions can
be studied in detail along the major and minor axes of M51. The streaming
velocities are very large, 60-150 km/s. For the first time, sufficient
resolution to resolve the structure in the molecular streaming motions is
obtained. Our data support the presence of galactic shocks in the arms of M51.
In general, velocity gradients across arms are higher by a factor of 2-10 than
previously found. They vary in steepness along the spiral arms, becoming
particularly steep in between GMAs. The steep gradients cause conditions of
strong reverse shear in several regions in the arms, and thus the notion that
shear is generally reduced by streaming motions in spiral arms will have to be
modified. Of the three GMAs studied on the SW arm, only one shows reduced
shear. We find an expansion in the NE molecular arm at 25'' radius SE of the
center. This broadening occurs right after the end of the NE arm at the Inner
Lindblad Resonance. Bifurcations in the molecular spiral arm structure, at a
radius of 73'', may be evidence of a secondary compression of the gas caused by
the 4/1 ultraharmonic resonance. Inside the radius of the ILR, we detect narrow
(~ 5'') molecular spiral arms possibly related to the K-band arms found in the
same region. We find evidence of non-circular motions in the inner 20'' which
are consistent with gas on elliptical orbits in a bar.Comment: 29 pages, 15 figures, uses latex macros for ApJ; accepted for
publication in Ap
Expansion history and f(R) modified gravity
We attempt to fit cosmological data using modified Lagrangians
containing inverse powers of the Ricci scalar varied with respect to the
metric. While we can fit the supernova data well, we confirm the behaviour at medium to high redshifts reported elsewhere and argue
that the easiest way to show that this class of models are inconsistent with
the data is by considering the thickness of the last scattering surface. For
the best fit parameters to the supernova data, the simplest 1/R model gives
rise to a last scattering surface of thickness , inconsistent
with observations.Comment: accepted in JCAP, presentation clarified, results and conclusions
unchange
H2O line mapping at high spatial and spectral resolution - Herschel observations of the VLA1623 outflow
Apart from being an important coolant, H2O is known to be a tracer of
high-velocity molecular gas. Recent models predict relatively high abundances
behind interstellar shockwaves. The dynamical and physical conditions of the
H2O emitting gas, however, are not fully understood yet. We aim to determine
the abundance and distribution of H2O, its kinematics and the physical
conditions of the gas responsible for the H2O emission. The observed line
profile shapes help us understand the dynamics in molecular outflows. We mapped
the VLA1623 outflow, in the ground-state transitions of o-H2O, with the HIFI
and PACS instruments. We also present observations of higher energy transitions
of o-H2O and p-H2O obtained with HIFI and PACS towards selected outflow
positions. From comparison with non-LTE radiative transfer calculations, we
estimate the physical parameters of the water emitting regions. The observed
water emission line profiles vary over the mapped area. Spectral features and
components, tracing gas in different excitation conditions, allow us to
constrain the density and temperature of the gas. The H2O emission originates
in a region where temperatures are comparable to that of the warm H2 gas
(T\gtrsim200K). Thus, the H2O emission traces a gas component significantly
warmer than the gas responsible for the low-J CO emission. The H2O column
densities at the CO peak positions are low, i.e. N(H2O) \simeq (0.03-10)x10e14
cm-2. The H2O abundance with respect to H2 in the extended outflow is estimated
at X(H2O)<1x10e-6, significantly lower than what would be expected from most
recent shock models. The H2O emission traces a gas component moving at
relatively high velocity compared to the low-J CO emitting gas. However, other
dynamical quantities such as the momentum rate, energy and mechanical
luminosity are estimated to be the same, independent of the molecular tracer
used, CO or H2O.Comment: 14 pages, 13 figures, 4 table
Thermal Emission as a Test for Hidden Nuclei in Nearby Radio Galaxies
The clear sign of a hidden quasar inside a radio galaxy is the appearance of
quasar spectral features in its polarized (scattered) light. However that
observational test requires suitably placed scattering material to act as a
mirror, allowing us to see the nuclear light. A rather robust and more general
test for a hidden quasar is to look for the predicted high mid-IR luminosity
from the nuclear obscuring matter. The nuclear waste heat is detected and well
isolated in the nearest narrow line radio galaxy, Cen A. This confirms other
indications that Cen A does contain a modest quasar-like nucleus. However we
show here that M87 does not: at high spatial resolution, the mid-IR nucleus is
seen to be very weak, and consistent with simple synchrotron emission from the
base of the radio jet. This fairly robustly establishes that there are "real"
narrow line radio galaxies, without the putative accretion power, and with
essentially all the luminosity in kinetic form. Next we show the intriguing
mid-IR morphology of Cygnus A, reported previously by us and later discussed in
detail by Radomski et al. (2002). All of this mid-IR emission is consistent
with reprocessing by a hidden quasar, known to exist from spectropolarimetry by
Ogle et al. (1997) and other evidence.Comment: 21 pages, 5 figure
Hubble Space Telescope NICMOS Imaging of the Core of M87
We present broad-band 1.1, 1.6 and 2.2 micron images and a 2.37 micron
narrow-band image of the inner 19" of the nearby radio galaxy M87, obtained
with the Near Infrared Camera and Multi-Object Spectrometer of the Hubble Space
Telescope (HST). The isophotes of the broad-band images are almost perfectly
circular to within approximately 0.5" (~ 50 pc) of the active nucleus, and an
r**1/4 law provides a good fit to the galaxy profile to within the same
distance. This result agrees with predictions that the nuclear supermassive
black hole will produce a nearly spherical distribution of the surrounding
stars within a galaxy crossing time. A difference image formed from the 1.6
micron image and a V-band image obtained with the HST Wide Field Planetary
Camera 2 does not show any clear evidence of a physically thick dusty torus
around the nucleus, consistent with its lack of strong thermal infrared
emission. The images and associated colors also confirm that the regions beyond
the nucleus do not contain strongly concentrated dust,in contrast to many other
radio galaxies. In combination with other recent observations, these results
indicate that M87 represents the dynamically evolved product of past galaxy
mergers, and suggest that its nucleus is in the final stages of activity.Comment: Accepted for publication in the Astronomical Journa
Lorentz Invariance Violation induced time delays in GRBs in different cosmological models
Lorentz Invariance Violation (LIV) manifesting itself by energy dependent
modification of standard relativistic dispersion relation has recently
attracted a considerable attention. Ellis et al. previously investigated the
energy dependent time offsets in different energy bands on a sample of gamma
ray bursts and, assuming standard cosmological model, they found a weak
indication for redshift dependence of time delays suggestive of LIV. Going
beyond the CDM cosmology we extend this analysis considering also four
alternative models of dark energy (quintessence with constant and variable
equation of state, Chaplygin gas and brane-world cosmology). It turns out that
the effect noticed by Ellis et al. is also present in those models and is the
strongest for quintessence with variable equation of state.Comment: 14 pages, 1 figur
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