322 research outputs found
Parsec-scale dust distributions in Seyfert galaxies - Results of the MIDI AGN snapshot survey
The emission of warm dust dominates the mid-infrared spectra of active
galactic nuclei (AGN). Only interferometric observations provide the necessary
angular resolution to resolve the nuclear dust and to study its distribution
and properties. The investigation of dust in AGN cores is hence one of the main
science goals for the MID-infrared Interferometric instrument MIDI at the VLTI.
As the first step, the feasibility of AGN observations was verified and the
most promising sources for detailed studies were identified. This was carried
out in a "snapshot survey" with MIDI using Guaranteed Time Observations. In the
survey, observations were attempted for 13 of the brightest AGN in the
mid-infrared which are visible from Paranal. The results of the three
brightest, best studied sources have been published in separate papers. Here we
present the interferometric observations for the remaining 10, fainter AGN. For
8 of these, interferometric measurements could be carried out. Size estimates
or limits on the spatial extent of the AGN-heated dust were derived from the
interferometric data of 7 AGN. These indicate that the dust distributions are
compact, with sizes on the order of a few parsec. The derived sizes roughly
scale with the square root of the luminosity in the mid-infrared, s ~ sqrt(L),
with no clear distinction between type 1 and type 2 objects. This is in
agreement with a model of nearly optically thick dust structures heated to T ~
300 K. For three sources, the 10 micron feature due to silicates is tentatively
detected either in emission or in absorption. Based on the results for all AGN
studied with MIDI so far, we conclude that in the mid-infrared the differences
between individual galactic nuclei are greater than the generic differences
between type 1 and type 2 objects.Comment: 18 pages, 8 figures, updated to version published in A&A 502, 67-8
Updating quasar bolometric luminosity corrections. II. Infrared bolometric corrections
We present infrared bolometric luminosity corrections derived from the
detailed spectral energy distributions of 62 bright quasars of low- to
moderate-redshift (z=0.03-1.4). At 1.5, 2, 3, 7, 12, 15, and 24 microns we
provide bolometric corrections of the mathematical forms L_iso=\zeta \lambda
L_\lambda and log(L_iso)=A+B log(\lambda L_\lambda). Bolometric corrections for
radio-loud and radio-quiet objects are consistent within 95% confidence
intervals, so we do not separate them. Bolometric luminosities estimated using
these corrections are typically smaller than those derived from some commonly
used in the literature. We investigate the possibility of a luminosity
dependent bolometric correction and find that, while the data are consistent
with such a correction, the dispersion is too large and the luminosity range
too small to warrant such a detailed interpretation. Bolometric corrections at
1.5 m are appropriate for objects with properties that fall in the range
log(L_bol)=45.4-47.3 and bolometric corrections at all other wavelengths are
appropriate for objects with properties that fall in the range
log(L_bol)=45.1-47.0.Comment: 13 pages, 4 tables, 8 figures, accepted to MNRA
Emergency revascularization in patients with cardiogenic shock on admission: a report from the SHOCK trial and registry
Aims To determine clinical correlates and optimal treatment strategy in patients with cardiogenic shock (CS) on admission. Methods and results In SHould we emergently revascularize Occluded Coronaries in cardiogenic shocK? (SHOCK) trial and registry patients with left ventricular (LV) dysfunction (n=1053), CS on admission occurred in 26% of directly admitted patients (n=166/627). Time from myocardial infarction to CS was shorter, initial haemodynamic profile poorer, and aggressive treatment less frequent in CS on admission than in delayed CS patients. CS on admission patients constituted a smaller relative proportion (11%) of the transferred (n=48/426) when compared with the directly admitted cohort (P<0.001). In-hospital mortality was higher (75 vs. 56%; P<0.001) with more rapid death (24-h mortality 40 vs. 17%; P<0.001) in CS on admission than in delayed CS patients. Emergency revascularization reduced in-hospital mortality in CS on admission (60 vs. 82%; P=0.001) and in delayed CS patients similarly (46 vs. 62%; P<0.001; interaction P=0.25). After adjustment for clinical differences, CS on admission was an independent predictor of in-hospital mortality (P=0.008). Conclusion CS on admission patients have a worse outcome but benefit equally from emergency revascularization as delayed CS patients, emphasizing the need for rapid and direct access of CS on admission patients to facilities providing this car
Ammonia (J,K) = (1,1) to (4,4) and (6,6) inversion lines detected in the Seyfert 2 galaxy NGC 1068
We present the detection of the ammonia (NH3) (J,K) = (1,1) to (4,4) and
(6,6) inversion lines toward the prototypical Seyfert 2 galaxy NGC 1068, made
with the Green Bank Telescope (GBT). This is the first detection of ammonia in
a Seyfert galaxy. The ortho-to-para-NH3 abundance ratio suggests that the
molecule was formed in a warm medium of at least 20 K. For the NH3 column
density and fractional abundance, we find (1.09\pm0.23)\times10^14 cm^-2 and
(2.9\pm0.6)\times10^-8, respectively, from the inner 1.2 kpc of NGC 1068. The
kinetic temperature can be constrained to 80\pm20 K for the bulk of the
molecular gas, while some fraction has an even higher temperature of 140\pm30
K.Comment: 5 pages, 3 figures, accepted by A&
A randomised controlled trial of high vs low volume initiation and rapid vs slow advancement of milk feeds in infants with birthweights 1000 g in a resource-limited setting
Background: Optimal feeding regimens for infants ≤ 1000 g have not been established and are a global healthcare concern. Aims and objectives: A controlled trial to establish the safety and efficacy of high vs low volume initiation and rapid vs slow advancement of milk feeds in a resource-limited setting was undertaken. Methods: Infants ≤ 1000 g birthweight were randomised to one of four arms, either low (4 ml/kg/day) or high (24 ml/kg/day) initiation and either slow (24 ml/kg/day) or rapid (36 ml/kg/day) advancement of exclusive feeds of human milk (mother’s or donor) until a weight of 1200 g was reached. After this point, formula was used to supplement insufficient mother’s milk. The primary outcome was time to reach 1500 g. Results: infants were recruited (51: low/slow; 47: low/rapid; 52: high/slow; 50: high/rapid). Infants on rapid advancement regimens reached 1500 g most rapidly (hazard ratio 1.48, 95% CI 1.05–2.09, P=0.03). The rapid advancement groups also regained birthweight more rapidly (hazard ratio 1.77, 95% CI 1.26–2.50, P=0.001). There was no apparent effect of high vs low initiation volumes but there was some evidence of interaction between interventions. There were no significant differences in other secondary outcomes, including necrotising enterocolitis, feed intolerance and late-onset sepsis. Conclusions: In this small pilot study, higher initiation feed volumes and larger daily increments appeared to be well tolerated and resulted in more rapid early weight gain. These data provide justification for a larger study in resource-limited settings to address mortality, necrotising enterocolitis and other important outcomes
Resolving the complex structure of the dust torus in the active nucleus of the Circinus galaxy
To test the dust torus model for active galactic nuclei directly, we study
the extent and morphology of the nuclear dust distribution in the Circinus
galaxy using high resolution interferometric observations in the mid-infrared
with the MIDI instrument at the Very Large Telescope Interferometer. We find
that the dust distribution in the nucleus of Circinus can be explained by two
components, a dense and warm disk-like component of 0.4 pc size and a slightly
cooler, geometrically thick torus component with a size of 2.0 pc. The disk
component is oriented perpendicular to the ionisation cone and outflow and
seems to show the silicate feature at 10 micron in emission. It coincides with
a nuclear maser disk in orientation and size. From the energy needed to heat
the dust, we infer a luminosity of the accretion disk corresponding to 20% of
the Eddington luminosity of the nuclear black hole. We find that the
interferometric data are inconsistent with a simple, smooth and axisymmetric
dust emission. The irregular behaviour of the visibilities and the shallow
decrease of the dust temperature with radius provide strong evidence for a
clumpy or filamentary dust structure. We see no evidence for dust reprocessing,
as the silicate absorption profile is consistent with that of standard galactic
dust. We argue that the collimation of the ionising radiation must originate in
the geometrically thick torus component. Our findings confirm the presence of a
geometrically thick, torus-like dust distribution in the nucleus of Circinus,
as required in unified schemes of Seyfert galaxies. Several aspects of our data
require that this torus is irregular, or "clumpy".Comment: 20 pages, 16 figures, accepted for publication by A&
Resource implications of adopting a restrictive neonatal blood transfusion policy
Background. Blood transfusions (BTFs) are not without risk and pose a significant financial burden on resource-limited services. In line with current international evidence, the nursery at Groote Schuur Hospital (GSH), Cape Town, South Africa, introduced a restrictive BTF protocol to minimise transfusions and manage costs.Objective. To determine whether adopting a restrictive BTF policy results in fewer transfusions. Methods. Data were retrospectively collected on all infants who received BTFs in the GSH nursery over a 6-month period following adoption of a restrictive BTF policy in 2010. BTF figures for a similar time period before the restrictive policy, during 2008, were obtained for comparison.Results. After introduction of the restrictive BTF policy, 42 of 1 097 infants admitted (3.8%) received a total of 64 BTFs. In comparison, 102 of a total of 940 infants (10.9%) admitted during a period of the same length before introduction of the restrictive BTF policy received a total of 121 transfusions. Comparison between the number of BTFs administered before and after the restrictive policy showed a highly statistically significant difference (p<0.001). The total cost of the blood products used in the two 6-month periods was R91 870 v. R48 640, based on current prices. Conclusions. By adopting a restrictive policy, we were able to halve the number of BTFs, reduce risks associated with transfusions, and achieve significant cost benefits. Following evidence-based guidelines results in high standards of care, while also making the most effective use of resources.
Mapping the radial structure of AGN tori
We present mid-IR interferometric observations of 6 type 1 AGNs at multiple
baseline lengths of 27--130m, reaching high angular resolutions up to
lambda/B~0.02 arcseconds. For two of the targets, we have simultaneous near-IR
interferometric measurements as well. The multiple baseline data directly probe
the radial distribution of the material on sub-pc scales. Within our sample,
which is small but spans over ~2.5 orders of magnitudes in the UV/optical
luminosity L of the central engine, the radial distribution clearly and
systematically changes with luminosity. First, we show that the brightness
distribution at a given mid-IR wavelength seems to be rather well described by
a power law, which makes a simple Gaussian or ring size estimation quite
inadequate. Here we instead use a half-light radius R_1/2 as a representative
size. We then find that the higher luminosity objects become more compact in
normalized half-light radii R_1/2 /R_in in the mid-IR, where R_in is the dust
sublimation radius empirically given by the L^1/2 fit of the near-IR
reverberation radii. This means that, contrary to previous studies, the
physical mid-IR emission size (e.g. in pc) is not proportional to L^1/2, but
increases with L much more slowly, or in fact, nearly constant at 13 micron.
Combining the size information with the total flux specta, we infer that the
radial surface density distribution of the heated dust grains changes from a
steep ~r^-1 structure in high luminosity objects to a shallower ~r^0 structure
in those of lower luminosity. The inward dust temperature distribution does not
seem to smoothly reach the sublimation temperature -- on the innermost scale of
~R_in, a relatively low temperature core seems to co-exist with a slightly
distinct brightness concentration emitting roughly at the sublimation
temperature.Comment: accepted for publication in A&
Does rapid urbanization aggravate health disparities? Reflections on the epidemiological transition in Pune, India
Background: Rapid urbanization in low- and middle-income countries reinforces risk and epidemiological transition in urban societies, which are characterized by high socioeconomic gradients. Limited availability of disaggregated morbidity data in these settings impedes research on epidemiological profiles of different population subgroups. Objective: The study aimed to analyze the epidemiological transition in the emerging megacity of Pune with respect to changing morbidity and mortality patterns, also taking into consideration health disparities among different socioeconomic groups. Design: A mixed-methods approach was used, comprising secondary analysis of mortality data, a survey among 900 households in six neighborhoods with different socioeconomic profiles, 46 in-depth interviews with laypeople, and expert interviews with 37 health care providers and 22 other health care workers. Results: The mortality data account for an epidemiological transition with an increasing number of deaths due to non-communicable diseases (NCDs) in Pune. The share of deaths due to infectious and parasitic diseases remained nearly constant, though the cause of deaths changed considerably within this group. The survey data and expert interviews indicated a slightly higher prevalence of diabetes and hypertension among higher socioeconomic groups, but a higher incidence and more frequent complications and comorbidities in lower socioeconomic groups. Although the self-reported morbidity for malaria, gastroenteritis, and tuberculosis did not show a socioeconomic pattern, experts estimated the prevalence in lower socioeconomic groups to be higher, though all groups in Pune would be affected. Conclusions: The rising burden of NCDs among all socioeconomic groups and the concurrent persistence of communicable diseases pose a major challenge for public health. Improvement of urban health requires a stronger focus on health promotion and disease prevention for all socioeconomic groups with a holistic understanding of urban health. In order to derive evidence-based solutions and interventions, routine surveillance data become indispensable
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