1,749 research outputs found
Cochlear implantation in elderly: indication and results
The aim of the study was to investigate the outcome of CI among elderly cochlear implant recipients. Results from our study have shown that elder patient implanted above 75 yrs can obtain significant hearing benefit from cochlear implantation. Similarly to the results reported by Vermeer1, in our study subjects implanted at elder age show lower scores compared to younger adult implantees
XMM-Newton discovery of a sharp spectral feature at ~7 keV in the Narrow-Line Seyfert 1 galaxy 1H 0707-495
We report the first detection of a sharp spectral feature in a Narrow-Line
Seyfert 1 galaxy. Using XMM-Newton we have observed 1H0707-495 and find a drop
in flux by a factor of more than 2 at a rest-frame energy of ~7 keV without any
detectable narrow Fe K alpha line emission. The energy of this feature suggests
a connection with the neutral iron K photoelectric edge, but the lack of any
obvious absorption in the spectrum at lower energies makes the interpretation
challenging. We explore two alternative explanations for this unusual spectral
feature: (i) partial covering absorption by clouds of neutral material and (ii)
ionised disc reflection with lines and edges from different ionisation stages
of iron blurred together by relativistic effects. We note that both models
require an iron overabundance to explain the depth of the feature. The X-ray
light curve shows strong and rapid variability, changing by a factor of four
during the observation. The source displays modest spectral variability which
is uncorrelated with flux.Comment: 5 pages incl. 6 figures, accepted for publication in MNRA
X-ray Reflection from Inhomogeneous Accretion Disks: II. Emission Line Variability and Implications for Reverberation Mapping
One of the principal scientific objectives of the upcoming Constellation-X
mission is to attempt to map the inner regions of accretion disks around black
holes in Seyfert galaxies by reverberation mapping of the Fe K fluorescence
line. This area of the disk is likely radiation pressure dominated and subject
to various dynamical instabilities. Here, we show that density inhomogeneities
in the disk atmosphere resulting from the photon bubble instability (PBI) can
cause rapid changes in the X-ray reflection features, even when the
illuminating flux is constant. Using a simulation of the development of the
PBI, we find that, for the disk parameters chosen, the Fe K and O VIII Ly\alpha
lines vary on timescales as short as a few hundredths of an orbital time. In
response to the changes in accretion disk structure, the Fe K equivalent width
(EW) shows variations as large as ~100 eV. The magnitude and direction
(positive or negative) of the changes depends on the ionization state of the
atmosphere. The largest changes are found when the disk is moderately ionized.
The O VIII EW varies by tens of eV, as well as exhibiting plenty of rapid,
low-amplitude changes. This effect provides a natural explanation for some
observed instances of short timescale Fe K variability which was uncorrelated
with the continuum (e.g., Mrk 841). New predictions for Fe K reverberation
mapping should be made which include the effects of this accretion disk driven
line variability and a variable ionization state. Reflection spectra averaged
over the evolution of the instability are well fit by constant density models
in the 2-10 keV region.Comment: 20 pages, 3 figures. Accepted by Ap
Computer Components and Systems
Contains reports on three research projects.United States Navy, Bureau of Ships (Contract NObsr 77603
A softer look at MCG--6-30-15 with XMM-Newton
We present analysis and results from the Reflection Grating Spectrometer
during the 320 ks XMM observation of the Seyfert 1 galaxy MCG-6-30-15. The
spectrum is marked by a sharp drop in flux at 0.7 keV which has been
interpreted by Branduardi-Raymont et al. as the blue wing of a relativistic
OVIII emission line and by Lee at al. as a dusty warm absorber. We find that
the drop is well explained by the FeI L2,3 absorption edges and obtain
reasonable fits over the 0.32-1.7 keV band using a multizone, dusty warm
absorber model. Some residuals remain which could be due to emission from a
relativistic disc, but at a much weaker level than from any model relying on
relativistic emission lines alone. A model based on such emission lines can be
made to fit if sufficient (warm) absorption is added, although the line
strengths exceed those expected. The EPIC pn difference spectrum between the
highest and lowest flux states of the source indicates that this is a power-law
in the 3-10 keV band which, if extrapolated to lower energies, reveals the
absorption function acting on the intrinsic spectrum, provided that any
emission lines do not scale exactly with the continuum. We find that this
function matches our dusty warm absorber model well. The soft X-ray spectrum is
therefore dominated by absorption structures, with the equivalent width of any
individual emission lines in the residuals being below about 30 eV. (abridged)Comment: 8 pages, 10 figures, submitted to MNRA
Resolving the cosmic X-ray background with a next-generation high-energy X-ray observatory
The cosmic X-ray background (CXB), which peaks at an energy of ~30 keV, is
produced primarily by emission from accreting supermassive black holes (SMBHs).
The CXB therefore serves as a constraint on the integrated SMBH growth in the
Universe and the accretion physics and obscuration in active galactic nuclei
(AGNs). This paper gives an overview of recent progress in understanding the
high-energy (>~10 keV) X-ray emission from AGNs and the synthesis of the CXB,
with an emphasis on results from NASA's NuSTAR hard X-ray mission. We then
discuss remaining challenges and open questions regarding the nature of AGN
obscuration and AGN physics. Finally, we highlight the exciting opportunities
for a next-generation, high-resolution hard X-ray mission to achieve the
long-standing goal of resolving and characterizing the vast majority of the
accreting SMBHs that produce the CXB.Comment: Science White paper submitted to Astro2020 Decadal Survey; 5 pages, 3
figures, plus references and cover pag
Sex-related differences in premature cardiovascular disease in familial hypercholesterolemia
BACKGROUND: Familial hypercholesterolemia (FH) is associated with an increased prevalence of premature atherosclerotic cardiovascular disease (ASCVD), however, little is known about sex-specific differences in premature ASCVD and its risk factors.
OBJECTIVE: The present study seeks to assess the burden and risk factors for premature ASCVD among men and women with FH.
METHODS: In this study we retrospectively examined sex-specific differences in ASCVD prevalence, risk factor burdens, and lipid treatment outcomes in 782 individuals with clinically or genetically confirmed FH treated in 5 U.S. lipid and genetics clinics. A generalized linear model using Binomial distribution with random study site effect and sex-stratified analysis was used to determine the strongest predictors of premature ASCVD, and lipid treatment outcomes. Covariates included age, sex, diabetes mellitus (DM), hypertension, and current smoking.
RESULTS: Among the cohort, 98/280 men (35%) and 89/502 women (18%) had premature ASCVD (defined as \u3c55 years in men and \u3c65 years in women). Women with premature ASCVD had higher mean treated total cholesterol (216 vs. 179 mg/dl, p=\u3c0.001) and LDL-C (135 vs. 109 mg/dl, p= 0.005).
CONCLUSION: These data confirm that high percentages of women and men with FH develop premature ASCVD, and suggest that FH may narrow the observed sex difference in premature ASCVD onset. These data support more aggressive prevention and treatment strategies in FH, including in women, to reduce non-lipid risk factors and residual hypercholesterolemia
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