1,263 research outputs found
Antidepressant medication and ocular factors in association with the need for anti-VEGF retreatment in neovascular age-related macular degeneration.
Vascular endothelial growth factor (VEGF) is a key player in the pathogenesis of neovascular age-related macular degeneration (nAMD) and is also involved in the final common pathway of antidepressant medication. This study investigated the relationship between the need for anti-VEGF retreatment in patients with nAMD and antidepressant medication, and the potential impact of ocular structural factors.
Data from two identical prospective 2-year treatment protocols using ranibizumab or aflibercept in a variable-dosing regimen ('Observe-and-Plan') were analysed. Retreatment requirement was compared with antidepressant medication intake (primary outcome) and a variety of ocular factors from baseline and from month 3 response (secondary outcomes), using univariate and multivariate analyses.
Of the 206 included patients (227 eyes), 19 were on antidepressant medication. Their nAMD eyes significantly more often had pigment epithelium detachment (PED, p=0.04). Multivariate analysis revealed a significant association between anti-VEGF retreatment requirement and antidepressant medication use (p=0.027), as well as thicker central retinal thickness at month 3 (p<0.0001) and month 3 PED height (p=0.001).
This study provides evidence that treatment with antidepressant medication increases the anti-VEGF retreatment requirement in patients with nAMD, possibly through the interplay of antidepressant medication, depression status and VEGF levels
First experimental results of very high accuracy centroiding measurements for the neat astrometric mission
NEAT is an astrometric mission proposed to ESA with the objectives of
detecting Earth-like exoplanets in the habitable zone of nearby solar-type
stars. NEAT requires the capability to measure stellar centroids at the
precision of 5e-6 pixel. Current state-of-the-art methods for centroid
estimation have reached a precision of about 2e-5 pixel at two times Nyquist
sampling, this was shown at the JPL by the VESTA experiment. A metrology system
was used to calibrate intra and inter pixel quantum efficiency variations in
order to correct pixelation errors. The European part of the NEAT consortium is
building a testbed in vacuum in order to achieve 5e-6 pixel precision for the
centroid estimation. The goal is to provide a proof of concept for the
precision requirement of the NEAT spacecraft. In this paper we present the
metrology and the pseudo stellar sources sub-systems, we present a performance
model and an error budget of the experiment and we report the present status of
the demonstration. Finally we also present our first results: the experiment
had its first light in July 2013 and a first set of data was taken in air. The
analysis of this first set of data showed that we can already measure the pixel
positions with an accuracy of about 1e-4 pixel.Comment: SPIE conference proceeding
Апроксимація згортки розподілів Вейбулла за допомогою сплайн-експоненційних розподілів
Calculable technology of spline-exponential approximation to Weibull renewal has proposed. The comparative analysis of results of methods of approximation is conducted with the results of construction of analytical renewal function for the Weibull distribution.Предложена вычислительная технология аппроксимации свёртки распределений Вейбулла с помощью сплайн-экспоненциальных распределений. Проведён сравнительный анализ результатов методов аппроксимации с результатами построения аналитической функции распределения свёртки.Запропоновано обчислювальну технологiю апроксимацiї згортки розподiлів Вейбулла за допомогою сплайн-експоненцiйних розподілів. Проведено порівняльний аналіз результатів апроксимаційних методів з результатами побудови аналітичної функції розподілу згортки.
A detector interferometric calibration experiment for high precision astrometry
Context: Exoplanet science has made staggering progress in the last two
decades, due to the relentless exploration of new detection methods and
refinement of existing ones. Yet astrometry offers a unique and untapped
potential of discovery of habitable-zone low-mass planets around all the
solar-like stars of the solar neighborhood. To fulfill this goal, astrometry
must be paired with high precision calibration of the detector.
Aims: We present a way to calibrate a detector for high accuracy astrometry.
An experimental testbed combining an astrometric simulator and an
interferometric calibration system is used to validate both the hardware needed
for the calibration and the signal processing methods. The objective is an
accuracy of 5e-6 pixel on the location of a Nyquist sampled polychromatic point
spread function.
Methods: The interferometric calibration system produced modulated Young
fringes on the detector. The Young fringes were parametrized as products of
time and space dependent functions, based on various pixel parameters. The
minimization of func- tion parameters was done iteratively, until convergence
was obtained, revealing the pixel information needed for the calibration of
astrometric measurements.
Results: The calibration system yielded the pixel positions to an accuracy
estimated at 4e-4 pixel. After including the pixel position information, an
astrometric accuracy of 6e-5 pixel was obtained, for a PSF motion over more
than five pixels. In the static mode (small jitter motion of less than 1e-3
pixel), a photon noise limited precision of 3e-5 pixel was reached
Multiwavelength campaign on Mrk 509. XIII. Testing ionized-reflection models on Mrk 509
Active Galactic Nuclei (AGN) are the most luminous persistent objects in the
universe. An excess of X-ray emission below about 2 keV, called soft-excess, is
very common in Type 1 AGN spectra. The origin of this feature remains debated.
Originally modeled with a blackbody, there are now several possibilities to
model the soft-excess, including warm Comptonization and blurred ionized
reflection. In this paper, we test ionized-reflection models on Mrk 509, a
bright Seyfert 1 galaxy for which we have a unique data set, in order to
determine whether it can be responsible for the strong soft-excess. We use ten
simultaneous XMM-Newton and INTEGRAL observations performed every four days. We
present here the results of the spectral analysis, the evolution of the
parameters and the variability properties of the X-ray emission. The
application of blurred ionized-reflection models leads to a very strong
reflection and an extreme geometry, but fails to reproduce the broad-band
spectrum of Mrk 509. Two different scenarios for blurred ionized reflection are
discussed: stable geometry and lamp-post configuration. In both cases we find
that the model parameters do not follow the expected relations, indicating that
the model is fine-tuned to fit the data without physical justification. A
large, slow variation of the soft-excess without counterpart in the hard X-rays
could be explained by a change in ionization of the reflector. However, such a
change does not naturally follow from the assumed geometrical configuration.
Warm Comptonization remains the most probable origin of the soft-excess in this
object. Nevertheless, it is possible that both ionized reflection and warm
Comptonization mechanisms can explain the soft-excess in all objects, one
dominating the other one, depending on the physical conditions of the disk and
the corona.Comment: 12 pages, A&A accepte
Anatomy of the AGN in NGC 5548: V. A clear view of the X-ray narrow emission lines
Context. Our consortium performed an extensive multi-wavelength campaign of
the nearby Seyfert 1 galaxy NGC 5548 in 2013-14. The source appeared unusually
heavily absorbed in the soft X-rays, and signatures of outflowing absorption
were also present in the UV. He-like triplets of neon, oxygen and nitrogen, and
radiative recombination continuum (RRC) features were found to dominate the
soft X-ray spectrum due to the low continuum flux.
Aims. Here we focus on characterising these narrow emission features using
data obtained from the XMM-Newton RGS (770 ks stacked spectrum).
Methods. We use SPEX for our initial analysis of these features.
Self-consistent photoionisation models from Cloudy are then compared with the
data to characterise the physical conditions of the emitting region.
Results. Outflow velocity discrepancies within the O VII triplet lines can be
explained if the X-ray narrow-line region (NLR) in NGC 5548 is absorbed by at
least one of the six warm absorber components found by previous analyses. The
RRCs allow us to directly calculate a temperature of the emitting gas of a few
eV ( K), favouring photoionised conditions. We fit the data with a
Cloudy model of log erg cm s, log cm and log v km s for the emitting
gas; this is the first time the X-ray NLR gas in this source has been modelled
so comprehensively. This allows us to estimate the distance from the central
source to the illuminated face of the emitting clouds as pc,
consistent with previous work.Comment: Accepted by A&A, 15 pages, 6 figure
High resolution X-ray spectroscopy of the Seyfert 1 Mrk841: insights into the warm absorber and warm emitter
The Seyfert 1 galaxy Mrk841 was observed five times between 2001 and 2005 by
the XMM-Newton X-ray observatory. The source is well known for showing spectral
complexity in the variable iron line and in the soft X-ray excess. This paper
reports on the first study of Mrk841 soft X-ray spectrum at high spectral
resolution. The availability of multiple exposures obtained by the Reflection
Grating Spectrometer (RGS) cameras allows a thorough study of the complex
absorption and emission spectral features in the soft X-ray band.The three
combined exposures obtained in January 2001 and the two obtained in January and
July 2005 were analysed using the SPEX software. We detect a two-phase warm
absorber: a medium ionisation component (logxi~1.5-2.2 ergs s cm^{-1}) is
responsible for a deep absorption feature in the Unresolved Transition Array of
the Fe M-shell and for several absorption lines in the OVI-VIII band; a higher
ionisation phase with logxi~3 ergs s cm^{-1} is required to fit absorption in
the NeIX-X band. The ionisation state and the column density of the gas present
moderate variation from 2001 to 2005 for both phases. The high ionisation
component of the warm absorber has no effect in the Fe K band. No significant
velocity shift of the absorption lines is measured in the RGS data. Remarkably,
the 2005 spectra show emission features consistent with photoionisation in a
high density (n_e>10^{11} cm^{-3}) gas: a prominent OVII line triplet is
clearly observed in January 2005 and narrow Radiative Recombination Continua
(RRC) of OVII and CVI are observed in both 2005 data sets. A broad Gaussian
line around 21.7 Angstrom is also required to fit all the data sets. The
derived radial distance for the emission lines seems to suggest that the
photoionisation takes place within the optical Broad Line Region of the source.Comment: In press on A&A, replaced version includes language editing and typo
on velocities corrected in Table
Multiwavelength campaign on Mrk 509 XIV. Chandra HETGS spectra
We present in this paper the results of a 270 ks Chandra HETGS observation in
the context of a large multiwavelength campaign on the Seyfert galaxy Mrk 509.
The HETGS spectrum allows us to study the high ionisation warm absorber and the
Fe-K complex in Mrk 509. We search for variability in the spectral properties
of the source with respect to previous observations in this campaign, as well
as for evidence of ultra-fast outflow signatures. The Chandra HETGS X-ray
spectrum of Mrk 509 was analysed using the SPEX fitting package. We confirm the
basic structure of the warm absorber found in the 600 ks XMM-Newton RGS
observation observed three years earlier, consisting of five distinct
ionisation components in a multikinematic regime. We find little or no
variability in the physical properties of the different warm absorber phases
with respect to previous observations in this campaign, except for component D2
which has a higher column density at the expense of component C2 at the same
outflow velocity (-240 km/s). Contrary to prior reports we find no -700 km/s
outflow component. The O VIII absorption line profiles show an average covering
factor of 0.81 +/- 0.08 for outflow velocities faster than -100 km/s, similar
to those measured in the UV. This supports the idea of a patchy wind. The
relative metal abundances in the outflow are close to proto-solar. The narrow
component of the Fe Kalpha emission line shows no changes with respect to
previous observations which confirms its origin in distant matter. The narrow
line has a red wing that can be interpreted to be a weak relativistic emission
line. We find no significant evidence of ultra-fast outflows in our new
spectrum down to the sensitivity limit of our data.Comment: 12 pages, 9 figures, accepted for publication in Astronomy &
Astrophysic
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