694 research outputs found
The Kinematics and Physical Conditions pf the Ionized Gas in Markarian 509. II. STIS Echelle Observations
We present observations of the UV absorption lines in the luminous Seyfert 1
galaxy Mrk 509, obtained with the medium resolution (lambda/Delta-lambda ~
40,000) echelle gratings of the Space Telescope Imaging Spectrograph on the
Hubble Space Telescope. The spectra reveal the presence of eight kinematic
components of absorption in Ly-alpha, C IV, and N V, at radial velocities of
-422, -328, -259, -62, -22, +34, +124, and +210 km s^-1 with respect to an
emission-line redshift of z = 0.03440, seven of which were detected in an
earlier Far Ultraviolet Spectrographic Explorer (FUSE) spectrum. The component
at -22 km s^-1 also shows absorption by Si IV. The covering factor and velocity
width of the Si IV lines were lower than those of the higher ionization lines
for this component, which is evidence for two separate absorbers at this
velocity. We have calculated photoionization models to match the UV column
densities in each of these components. Using the predicted O VI column
densities, we were able to match the O VI profiles observed in the FUSE
spectrum. Based on our results, none of the UV absorbers can produce the X-ray
absorption seen in simultaneous Chandra observations; therefore, there must be
more highly ionized gas in the radial velocity ranges covered by the UV
absorbers.Comment: 30 pages, three figures (Figure 1 is in color). Accepted for
publication in the Astrophysical Journa
Mori Dream Spaces
This article is based on the 7th Takagi Lectures that the author delivered at the University of Tokyo on November 21-23, 2009.We explore the circle of ideas connecting finite generation of the Cox ring, Mori dream spaces and invariant theory
Evaluation of an inflammation-based prognostic score in patients with inoperable gastro-oesophageal cancer
There is increasing evidence that the presence of an ongoing systemic inflammatory response is associated with poor outcome in patients with advanced cancer. The aim of the present study was to examine whether an inflammation-based prognostic score (Glasgow Prognostic score, GPS) was associated with survival, in patients with inoperable gastro-oesophageal cancer. Patients diagnosed with inoperable gastro-oesophageal carcinoma and who had measurement of albumin and C-reactive protein concentrations, at the time of diagnosis, were studied (n=258). Clinical information was obtained from a gastro-oesophageal cancer database and analysis of the case notes. Patients with both an elevated C-reactive protein (>10 mg l−1) and hypoalbuminaemia (<35 g l−1) were allocated a GPS score of 2. Patients in whom only one of these biochemical abnormalities was present were allocated a GPS score of 1, and patients with a normal C-reactive protein and albumin were allocated a score of 0. On multivariate survival analysis, age (hazard ratio (HR) 1.22, 95% CI 1.02–1.46, P<0.05), stage (HR 1.55, 95% CI 1.30–1.83, P<0.001), the GPS (HR 1.51, 95% CI 1.22–1.86, P<0.001) and treatment (HR 2.53, 95% CI 1.80–3.56, P<0.001) were significant independent predictors of cancer survival. A 12-month cancer-specific survival in patients with stage I/II disease receiving active treatment was 67 and 60% for a GPS of 0 and 1, respectively. For stage III/IV disease, 12 months cancer-specific survival was 57, 25 and 12% for a GPS of 0, 1 and 2, respectively. In the present study, the GPS predicted cancer-specific survival, independent of stage and treatment received, in patients with inoperable gastro-oesophageal cancer. Moreover, the GPS may be used in combination with conventional staging techniques to improve the prediction of survival in patients with inoperable gastro-oesophageal cancer
The High Energy view of the Broad Line Radio Galaxy 3C 111
We present the analysis of Suzaku and XMM-Newton observations of the
broad-line radio galaxy (BLRG) 3C 111. Its high energy emission shows
variability, a harder continuum with respect to the radio quiet AGN population,
and weak reflection features. Suzaku found the source in a minimum flux level;
a comparison with the XMM-Newton data implies an increase of a factor of 2.5 in
the 0.5-10 keV flux, in the 6 months separating the two observations. The iron
K complex is detected in both datasets, with rather low equivalent width(s).
The intensity of the iron K complex does not respond to the change in continuum
flux. An ultra-fast, high-ionization outflowing gas is clearly detected in the
XIS data; the absorber is most likely unstable. Indeed, during the XMM-Newton
observation, which was 6 months after, the absorber was not detected. No clear
roll-over in the hard X-ray emission is detected, probably due to the emergence
of the jet as a dominant component in the hard X-ray band, as suggested by the
detection above ~ 100 keV with the GSO on-board Suzaku, although the present
data do not allow us to firmly constrain the relative contribution of the
different components. The fluxes observed by the gamma-ray satellites CGRO and
Fermi would be compatible with the putative jet component if peaking at
energies E ~ 100 MeV. In the X-ray band, the jet contribution to the continuum
starts to be significant only above 10 keV. If the detection of the jet
component in 3C 111 is confirmed, then its relative importance in the X-ray
energy band could explain the different observed properties in the high-energy
emission of BLRGs, which are otherwise similar in their other multiwavelength
properties. Comparison between X-ray and gamma-ray data taken at different
epochs suggests that the strong variability observed for 3C 111 is probably
driven by a change in the primary continuum.Comment: Accepted for publication in MNRAS; 15 pages, 9 figures, 5 table
The Swift BAT-detected Seyfert 1 Galaxies: X-ray Broadband Properties and Warm Absorbers
We present results from an analysis of the broad-band, 0.3-195 keV, X-ray
spectra of 48 Seyfert 1-1.5 sources detected in the very hard X-rays with the
Swift Burst Alert Telescope (BAT). This sample is selected in an all-sky survey
conducted in the 14-195 keV band. Therefore, our sources are largely unbiased
towards both obscuration and host galaxy properties. Our detailed and uniform
model fits to Suzaku/BAT and XMM-Newton/BAT spectra include the neutral
absorption, direct power-law, reflected emission, soft excess, warm absorption,
and narrow Fe K-alpha emission properties for the entire sample. We
significantly detect O VII and O VIII edges in 52% of our sample. The strength
of these detections are strongly correlated with the neutral column density
measured in the spectrum. Among the strongest detections, X-ray grating and UV
observations, where available, indicate outflowing material. The ionized column
densities of sources with O VII and O VIII detections are clustered in a narrow
range with N\,cm, while sources without strong
detections have column densities of ionized gas an order of magnitude lower.
Therefore, we note that sources without strong detections likely have warm
ionized outflows present but at low column densities that are not easily probed
with current X-ray observations. Sources with strong complex absorption have a
strong soft excess, which may or may not be due to difficulties in modeling the
complex spectra of these sources. Still, the detection of a flat Gamma ~ 1 and
a strong soft excess may allow us to infer the presence of strong absorption in
low signal-to-noise AGN spectra. Additionally, we include a useful correction
from the Swift BAT luminosity to bolometric luminosity, based on a comparison
of our spectral fitting results with published spectral energy distribution
fits from 33 of our sources.Comment: 60 pages (pre-print format), 14 figures, accepted to Ap
The relationship between quality of life (EORTC QLQ-C30) and survival in patients with gastro-oesopohageal cancer
It remains unclear whether any aspect of quality of life has a role in predicting survival in an unselected cohort of patients with gastro-oesophageal cancer. Therefore the aim of the present study was to examine the relationship between quality of life (EORTC QLQ-C30), clinico-pathological characteristics and survival in patients with gastro-oesophageal cancer. Patients presenting with gastric or oesophageal cancer, staged using the UICC tumour node metastasis (TNM) classification and who received either potentially curative surgery or palliative treatment between November 1997 and December 2002 (n=152) participated in a quality of life study, using the EORTC QLQ-C30 core questionnaire. On univariate analysis, age (P < 0.01), tumour length (P < 0.0001), TNM stage (P<0.0001), weight loss (P<0.0001), dysphagia score (P<0.001), performance status (P<0.1) and treatment (P<0.0001) were significantly associated with cancer-specific survival. EORTC QLQ-C30, physical functioning (P<0.0001), role functioning (P<0.001), cognitive functioning (P<0.01), social functioning (P<0.0001), global quality of life (P<0.0001), fatigue (P<0.0001), nausea/vomiting (P<0.01), pain (P<0.001), dyspnoea (P<0.0001), appetite loss (P<0.0001) and constipation (P<0.05) were also significantly associated with cancer-specific survival. On multivariate survival analysis, tumour stage (P<0.0001), treatment (P<0.001) and appetite loss (P<0.0001) were significant independent predictors of cancer-specific survival. The present study highlights the importance of quality of life (EORTC QLQ-C30) measures, in particular appetite loss, as a prognostic factor in these patients
Role of the dimerized gap due to anion ordering in spin-density wave phase of (TMTSF)ClO at high magnetic fields
Magnetoresistance measurements have been carried out along the highly
conducting a axis in the FISDW phase of hydrogened and deuterated
(TMTSF)ClO for various cooling rates through the anion ordering
temperature. With increasing the cooling rate, a) the high field phase boundary
, observed at 27 T in hydrogened samples for slowly cooled,
is shifted towards a lower field, b) the last semimetallic SDW phase below
is suppressed, and c) the FISDW insulating phase above
is enhanced in both salts. The cooling rate dependence of
the FISDW transition and of in both salts can be explained
by taking into account the peculiar SDW nesting vector stabilized by the
dimerized gap due to anion ordering.Comment: 6pages,6figures(EPS), accepted for publication in PR
Recommended from our members
The Physics Analysis of a Gas Attenuator with Argon as a Working Gas (Rev. 1)
A gas attenuator is an important element of the LCLS facility. The attenuator has to operate in a broad range of x-ray energies, provide attenuation coefficient between 1 and 10{sup 4} with the accuracy of 1% and, at the same time, be reliable and allow for many months of un-interrupted operation. A detailed design study of the attenuator based on the use of nitrogen as a working gas has been recently carried out by S. Shen [1]. In this note we assess the features of the attenuator based on the use of argon. We concentrate on the physics issues; the design features will probably be not that different from the aforementioned nitrogen attenuator. Although specific results obtained in our note pertain to argon, the general framework (and many equations obtained) are applicable also to the nitrogen attenuator. In the past, an analysis of the attenuator based on the use of a noble gas has already been carried out [2]. This analysis was performed for an extremely stringent set of specifications. In particular, a very large diameter for the unobstructed x-ray beam was set (1 cm) to accommodate the spontaneous radiation; the attenuator was supposed to cover the whole range of energies of the coherent radiation, from 800 eV to 8000 eV; the maximum attenuation was set at the level of 10{sup 4}; the use of solid attenuators was not allowed, as well as the use of rotating shutters. The need to reach a sufficient absorption at the high-energy end of the spectrum predetermined the choice of Xe as the working gas (in order to have a reasonable absorption at a not-too-high pressure). A sophisticated differential pumping system that included a Penning-type ion pump was suggested in order to minimize the gas leak into the undulator/accelerator part of the facility. A high cost of xenon meant also that an efficient (and expensive) gas-recovery system would have to be installed. The main parameter that determined the high cost and the complexity of the system was a large radius of the orifice. The present viewpoint allows for much smaller size of the orifice, a = 1.5 mm. The use of solid attenuators is also allowed for a higher-energy end of the spectrum. It is, therefore, worthwhile to reconsider various parameters of the gas attenuator for these much less stringent conditions. As a working gas we consider now the argon, which, on the one hand, provides reasonable absorption lengths and, on the other hand, is inexpensive enough to be exhausted into the atmosphere (no need for recovery). We concentrate on the processes in the main attenuation cell and just outside it, not touching upon a performance of the differential pumping system. The graphs presented in this report can serve for a general orientation only, not for getting exact numerical values of various parameters
Limits to Quantum Gravity Effects from Observations of TeV Flares in Active Galaxies
We have used data from the TeV gamma-ray flare associated with the active
galaxy Markarian 421 observed on 15 May 1996 to place bounds on the possible
energy-dependence of the speed of light in the context of an effective quantum
gravitational energy scale. The possibility of an observable time dispersion in
high energy radiation has recently received attention in the literature, with
some suggestions that the relevant energy scale could be less than the Planck
mass and perhaps as low as 10^16 GeV. The limits derived here indicate this
energy scale to be in excess of 4x10^16 GeV at the 95% confidence level. To the
best of our knowledge, this constitutes the first convincing limit on such
phenomena in this energy regime.Comment: 6 pages, including 2 figure
Nonequilibrium perturbation theory for spin-1/2 fields
A partial resummation of perturbation theory is described for field theories
containing spin-1/2 particles in states that may be far from thermal
equilibrium. This allows the nonequilibrium state to be characterized in terms
of quasiparticles that approximate its true elementary excitations. In
particular, the quasiparticles have dispersion relations that differ from those
of free particles, finite thermal widths and occupation numbers which, in
contrast to those of standard perturbation theory evolve with the changing
nonequilibrium environment. A description of this kind is essential for
estimating the evolution of the system over extended periods of time. In
contrast to the corresponding description of scalar particles, the structure of
nonequilibrium fermion propagators exhibits features which have no counterpart
in the equilibrium theory.Comment: 16 pages; no figures; submitted to Phys. Rev.
- …