300 research outputs found
X-ray power law spectra in active galactic nuclei
X-ray spectra of active galactic nuclei (AGN) are usually described as power
law spectra, characterized by the spectral slope or photon index
. Here we discuss the X-ray spectral properties within the framework of
clumpy accretion flows, and estimate the power law slope as a function of the
source parameters. We expect harder spectra in massive objects than in less
massive sources, and steeper spectra in higher accretion rate systems. The
predicted values of the photon index cover the range of spectral slopes
typically observed in Seyfert galaxies and quasars. The overall trends are
consistent with observations, and may account for the positive correlation of
the photon index with Eddington ratio (and the possible anticorrelation with
black hole mass) observed in different AGN samples. Spectral properties are
also closely related to variability properties. We obtain that shorter
characteristic time scales are associated with steeper spectra. This agrees
with the observed `spectral-timing' correlation.Comment: 6 pages, 1 figure, Astronomy and Astrophysics, accepte
Epidemiology of the 2012 influenza season in Victoria, Australia
Objective: To assess the magnitude and severity of the 2012 influenza season in Victoria, Australia using surveillance data
from five sources.
Methods: Data from influenza notifications, sentinel general practices, a sentinel hospital network, a sentinel locum service
and strain typing databases for 2012 were descriptively analysed.
Results: Influenza and influenza-like illness activity was moderate compared to previous years, although a considerable
increase in notified laboratory-confirmed influenza was observed. Type A influenza comprised between 83% and 87%
of cases from the general practitioners, hospitals and notifiable surveillance data. Influenza A/H3 was dominant in
July and August, and most tested isolates were antigenically similar to the A/Perth/16/2009 virus used in the vaccine.
There was a smaller peak of influenza type B in September. No tested viruses were resistant to any neuraminidase inhibitor
antivirals. Higher proportions of type A/H3, hospitalized cases and those with a comorbid condition indicated for influenza
vaccination were aged 65 years or older. Influenza vaccination coverage among influenza-like illness patients was 24% in
sentinel general practices and 50% in hospitals.
Discussion: The 2012 influenza season in Victoria was average compared to previous years, with an increased dominance
of A/H3 accompanied by increases in older and hospitalized cases. Differences in magnitude and the epidemiological
profile of cases detected by the different data sources demonstrate the importance of using a range of surveillance data to
assess the relative severity of influenza seasons.VIDRL receives support for its influenza surveillance programme from the Victorian Government Department of Health. The Melbourne WHO Collaborating Centre for Reference and Research on Influenza is supported by the Australian Government Department of Health and Ageing. FluCAN is supported by the Department of Health and Ageing
The anti-correlation between the hard X-ray photon index and the Eddington ratio in LLAGNs
We find a significant anti-correlation between the hard X-ray photon index
and the Eddington ratio L_Bol/L_Edd for a sample of Low-Ionization Nuclear
Emission-line Regions (LINERs) and local Seyfert galaxies, compiled from
literatures with Chandra or XMM-Newton observations. This result is in contrast
with the positive correlation found in luminous active galactic nuclei (AGNs),
while it is similar to that of X-ray binaries (XRBs) in low/hard state. Our
result is qualitatively consistent with the spectra produced from advection
dominated accretion flows (ADAFs). It implies that the X-ray emission of
low-luminosity active galactic nuclei (LLAGNs) may originate from the
Comptonization process in ADAF, and the accretion process in LLAGNs may be
similar to that of XRBs in the low/hard state, which is different from that in
luminous AGNs.Comment: 10 pages, 1 figure, accepted to MNRA
CAIXA: a catalogue of AGN in the XMM-Newton archive III. Excess Variance Analysis
We report on the results of the first XMM systematic "excess variance" study
of all the radio quiet, X-ray un-obscured AGN. The entire sample consist of 161
sources observed by XMM for more than 10 ks in pointed observations which is
the largest sample used so far to study AGN X-ray variability on time scales
less than a day. We compute the excess variance for all AGN, on different
time-scales (10, 20, 40 and 80 ks) and in different energy bands (0.3-0.7,
0.7-2 and 2-10 keV). We observe a highly significant and tight (~0.7 dex)
correlation between excess variance and MBH. The subsample of reverberation
mapped AGN shows an even smaller scatter (~0.45 dex) comparable to the one
induced by the MBH uncertainties. This implies that X-ray variability can be
used as an accurate tool to measure MBH and this method is more accurate than
the ones based on single epoch optical spectra. The excess variance vs.
accretion rate dependence is weaker than expected based on the PSD break
frequency scaling, suggesting that both the PSD high frequency break and the
normalisation depend on accretion rate in such a way that they almost
completely counterbalance each other. A highly significant correlation between
excess variance and 2-10 keV spectral index is observed. Both the variability
vs. LBol and FWHM_Hbeta correlations are consistent with being just by-products
of the correlation with MBH. The soft and medium variability is very well
correlated with the hard variability, suggesting that the additional soft
components (i.e. soft excess, warm absorber) add a minor contribution to the
total variability. Once the variability is rescaled for MBH and mdot, no
significant difference between narrow-line and broad-line Seyfert 1 is
observed. The results are in agreement with a picture where, to first
approximation, all local AGN have the same variability properties once rescaled
for MBH and accretion rate.Comment: 24 pages, 17 figures; accepted for publication in A&
Metallic behavior and related phenomena in two dimensions
For about twenty years, it has been the prevailing view that there can be no
metallic state or metal-insulator transition in two dimensions in zero magnetic
field. In the last several years, however, unusual behavior suggestive of such
a transition has been reported in a variety of dilute two-dimensional electron
and hole systems. The physics behind these observations is presently not
understood. We review and discuss the main experimental findings and suggested
theoretical models.Comment: To be published in Rev. Mod. Phy
Evaluation of Macitentan in Patients With Eisenmenger Syndrome.
Eisenmenger syndrome describes congenital heart disease-associated severe pulmonary hypertension accompanied by right-to-left shunting. The multicenter, double-blind, randomized, placebo-controlled, 16-week, phase III MAESTRO study (Macitentan in Eisenmenger Syndrome to Restore Exercise Capacity) evaluated the efficacy and safety of the endothelin receptor antagonist macitentan in patients with Eisenmenger syndrome.
Patients with Eisenmenger syndrome aged ≥12 years and in World Health Organization functional class II-III were randomized 1:1 to placebo or macitentan 10 mg once daily for 16 weeks. Patients with complex cardiac defects, Down syndrome and background PAH therapy were eligible. The primary end point was change from baseline to week 16 in 6-minute walk distance. Secondary end points included change from baseline to week 16 in World Health Organization functional class. Exploratory end points included NT-proBNP (N-terminal pro-B-type natriuretic peptide) at end of treatment expressed as a percentage of baseline. In a hemodynamic substudy, exploratory end points included pulmonary vascular resistance index (PVRi) at week 16 as a percentage of baseline.
Two hundred twenty six patients (macitentan n=114; placebo n=112) were randomized. At baseline, 60% of patients were in World Health Organization functional class II and 27% were receiving phosphodiesterase type-5 inhibitors. At week 16, the mean change from baseline in 6-minute walk distance was 18.3 m and 19.7 m in the macitentan and placebo groups (least-squares mean difference, -4.7 m; 95% confidence limit (CL), -22.8, 13.5; P=0.612). World Health Organization functional class improved from baseline to week 16 in 8.8% and 14.3% of patients in the macitentan and placebo groups (odds ratio, 0.53; 95% CL, 0.23, 1.24). NT-proBNP levels decreased with macitentan versus placebo (ratio of geometric means, 0.80; 95% CL, 0.68, 0.94). In the hemodynamic substudy (n=39 patients), macitentan decreased PVRi compared with placebo (ratio of geometric means, 0.87; 95% CL, 0.73, 1.03). The most common adverse events with macitentan versus placebo were headache (11.4 versus 4.5%) and upper respiratory tract infection (9.6 versus 6.3%); a hemoglobin decrease from baseline of ≥2 g/dL occurred in 36.0% versus 8.9% of patients. Five patients (3 macitentan; 2 placebo) prematurely discontinued treatment and 1 patient died (macitentan group).
Macitentan did not show superiority over placebo on the primary end point of change from baseline to week 16 in exercise capacity in patients with Eisenmenger syndrome.
URL: https://www.clinicaltrials.gov . Unique identifier: NCT01743001
X-ray variability of 104 active galactic nuclei. XMM-Newton power-spectrum density profiles
AGN, powered by accretion onto SMBHs, are thought to be scaled up versions of
Galactic black hole X-ray binaries (BH-XRBs). In the past few years evidence of
such correspondence include similarities in the broadband shape of the X-ray
variability power spectra, with characteristic bend times-scales scaling with
mass. We have performed a uniform analysis of the power spectrum densities
(PSDs) of 104 nearby (z<0.4) AGN using 209 XMM-Newton/pn observations. The PSDs
have been estimated in three energy bands: 0.2-10, 0.2-2, and 2-10 keV. The
sample comprises 61 Type-1 AGN, 21 Type-2 AGN, 15 NLSy1, and 7 BLLACS. We have
fitted each PSD to two models: (1) a single power-law model and (2) a bending
power-law model. Among the entire sample, 72% show significant variability in
at least one of the three bands tested. A high percentage of low-luminosity AGN
do not show any significant variability. The PSD of the majority of the
variable AGN was well described by a simple power-law with a mean index of 2.
In 15 sources we found that the bending power law model was preferred with a
mean slope of 3 and a mean bend frequency of 2.E-04 Hz. Only KUG1031+398
(REJ1034+396) shows evidence for quasi-periodic oscillations. The `fundamental
plane' relating variability timescale, black hole mass, and luminosity is
demonstrated using the new X-ray timing results presented here together with a
compilation of the previously detected timescales from the literature. Both
quantitative (i.e. scaling with BH mass) and qualitative (overall PSD shapes)
found in this sample of AGN are in agreement with the expectations for the
SMBHs and BH-XRBs being the same phenomenon scaled-up with the size of the BH.
The steep PSD slopes above the high frequency bend bear a closer resemblance to
those of the `soft/thermal dominated' BH-XRB states than other states.Comment: 19 pages, 8 figures, accepted for publication in A&
Howard's War on Terror: A Conceivable, Communicable and Coercive Foreign Policy Discourse
This article explores the relationship between language and political possibility. It is argued that John Howard’s language from 11 September 2001 to mid 2003 helped to enable the ‘War on Terror’ in an Australian context in three principal ways. Firstly, through contingent and contestable constructions of Australia, the world and their relationship, Howard’s language made interventionism conceivable. Secondly, emphasising shared values, mateship and mutual sacrifice in war, Howard embedded his foreign policy discourse in the cultural terrain of ‘mainstream Australia’, specifically framing a foreign policy discourse that was communicable to ‘battlers’ and disillusioned ‘Hansonites’. Thirdly, positioning alternatives as ‘un-Australian’, Howard’s language was particularly coercive, silencing potential oppositional voices
Performance of the CMS Cathode Strip Chambers with Cosmic Rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device
in the CMS endcaps. Their performance has been evaluated using data taken
during a cosmic ray run in fall 2008. Measured noise levels are low, with the
number of noisy channels well below 1%. Coordinate resolution was measured for
all types of chambers, and fall in the range 47 microns to 243 microns. The
efficiencies for local charged track triggers, for hit and for segments
reconstruction were measured, and are above 99%. The timing resolution per
layer is approximately 5 ns
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