308 research outputs found
Prognosis of Ocular Myasthenia Gravis: Retrospective Multicenter Analysis
PURPOSE:
To calculate the rate and timing of conversion from ocular myasthenia gravis to generalized myasthenia gravis.
DESIGN:
Retrospective multicenter analysis.
SUBJECTS:
Patients included in the study were diagnosed with ocular myasthenia gravis without the presence of generalized disease at onset.
METHODS:
We conducted a retrospective multicenter analysis. We reviewed charts of 158 patients who met diagnostic criteria for ocular myasthenia gravis. Patients were divided into 2 subgroups: an immunosuppressant treatment group and a nonimmunosuppressant treatment group. Timing of conversion to generalized disease and duration of follow-up also was evaluated. Additional data such as clinical symptoms at presentation, laboratory test results, and chest imaging results also were recorded.
MAIN OUTCOME MEASURES:
Conversion rates to generalized myasthenia at 2 years, effect of immunosuppression on conversion, and timing of conversion.
RESULTS:
The 158-patient cohort included 76 patients who received immunosuppressant therapy; the remaining 82 patients did not. The overall conversion rate to generalized disease was 20.9%. At 2 years, generalized myasthenia developed in 8 of 76 patients in the treated group and in 15 of 82 patients in the nonimmunotherapy group (odds ratio, 0.52; 95% confidence interval, 0.20-1.32). Median time for conversion to generalized disease was 20 months in the nonimmunosuppressant group and 24 months in the immunosuppressant group. Conversion occurred after 2 years of symptom onset in 30% of patients.
CONCLUSIONS:
Conversion rates from ocular to generalized myasthenia gravis may be lower than previously reported both in immunosuppressed and nonimmunosuppressed patients. A subset of patients may continue to convert to generalized disease beyond 2 years from onset of symptoms, and close monitoring should be continued.info:eu-repo/semantics/publishedVersio
muCool: A novel low-energy muon beam for future precision experiments
Experiments with muons () and muonium atoms () offer
several promising possibilities for testing fundamental symmetries. Examples of
such experiments include search for muon electric dipole moment, measurement of
muon and experiments with muonium from laser spectroscopy to gravity
experiments. These experiments require high quality muon beams with small
transverse size and high intensity at low energy.
At the Paul Scherrer Institute, Switzerland, we are developing a novel device
that reduces the phase space of a standard beam by a factor of
with efficiency. The phase space compression is achieved by
stopping a standard beam in a cryogenic helium gas. The stopped
are manipulated into a small spot with complex electric and magnetic
fields in combination with gas density gradients. From here, the muons are
extracted into the vacuum and into a field-free region. Various aspects of this
compression scheme have been demonstrated. In this article the current status
will be reported.Comment: 8 pages, 5 figures, TCP 2018 conference proceeding
Microlensing Detections of Planets in Binary Stellar Systems
We demonstrate that microlensing can be used for detecting planets in binary
stellar systems. This is possible because in the geometry of planetary binary
systems where the planet orbits one of the binary component and the other
binary star is located at a large distance, both planet and secondary companion
produce perturbations at a common region around the planet-hosting binary star
and thus the signatures of both planet and binary companion can be detected in
the light curves of high-magnification lensing events. We find that identifying
planets in binary systems is optimized when the secondary is located in a
certain range which depends on the type of the planet. The proposed method can
detect planets with masses down to one tenth of the Jupiter mass in binaries
with separations <~ 100 AU. These ranges of planet mass and binary separation
are not covered by other methods and thus microlensing would be able to make
the planetary binary sample richer.Comment: 5 pages, two figures in JPG forma
Dynamics of Multi-Player Games
We analyze the dynamics of competitions with a large number of players. In
our model, n players compete against each other and the winner is decided based
on the standings: in each competition, the mth ranked player wins. We solve for
the long time limit of the distribution of the number of wins for all n and m
and find three different scenarios. When the best player wins, the standings
are most competitive as there is one-tier with a clear differentiation between
strong and weak players. When an intermediate player wins, the standings are
two-tier with equally-strong players in the top tier and clearly-separated
players in the lower tier. When the worst player wins, the standings are least
competitive as there is one tier in which all of the players are equal. This
behavior is understood via scaling analysis of the nonlinear evolution
equations.Comment: 8 pages, 8 figure
Resolving the L/T transition binary SDSS J2052-1609 AB
Binaries provide empirical key constraints for star formation theories, like
the overall binary fraction, mass ratio distribution and the separation
distribution. They play a crucial role to calibrate the output of theoretical
models, like absolute magnitudes, colors and effective temperature depending on
mass, metallicity and age. We present first results of our on-going
high-resolution imaging survey of late type brown dwarfs. The survey aims at
resolving tight brown dwarf binary systems to better constrain the T dwarf
binary fraction. We intent to follow-up the individual binaries to determine
orbital parameters. Using NACO at the VLT we performed AO-assisted
near-infrared observations of SDSS J2052-1609. High-spatial resolution images
of the T1 dwarf were obtained in H and Ks filters. We resolved SDSS J2052-1609
into a binary system with a separation of 0.101" \pm 0.001". Archival data from
HST/NICMOS taken one year previous to our observations proves the components to
be co-moving. Using the flux ratio between the components we infer J, H and Ks
magnitudes for the resolved system. From the near-IR colors we estimate
spectral types of T1 +1 -4 and T2.5 \pm 1 for component A and B, respectively.
A first estimate of the total system mass yields Mtot > 78 Mjup, assuming a
circular orbit.Comment: 5 pages, 3 figures, 3 tables, accepted for publication by A&
Asteroseismic modelling of the metal-poor star Tau Ceti
Context. Asteroseismology is an effcient tool not only for testing stellar
structure and evolutionary theory but also constraining the parameters of stars
for which solar-like oscillations are detected, presently. As an important
southern asteroseismic target, Tau Ceti, is a metal-poor star. The main
features of the oscillations and some frequencies of ? Ceti have been
identified. Many scientists propose to comprehensively observe this star as
part of the Stellar Observations Network Group. Aims. Our goal is to obtain the
optimal model and reliable fundamental parameters for the metal-poor star Tau
Ceti by combining all non-asteroseismic observations with these seismological
data. Methods. Using the Yale stellar evolution code (YREC), a grid of stellar
model candidates that fall within all the error boxes in the HR diagram have
been constructed, and both the model frequencies and large- and small-
frequency separations are calculated using the Guenther's stellar pulsation
code. The \chi2c minimization is performed to identify the optimal modelling
parameters that reproduce the observations within their errors. The frequency
corrections of near-surface effects to the calculated frequencies using the
empirical law, as proposed by Kjeldsen and coworkers, are applied to the
models. Results. We derive optimal models, corresponding to masses of about
0.775 - 0.785 M? and ages of about 8 - 10 Gyr. Furthermore, we find that the
quantities derived from the non-asteroseismic observations (effective
temperature and luminosity) acquired spectroscopically are more accurate than
those inferred from interferometry for ? Ceti, because our optimal models are
in the error boxes B and C, which are derived from spectroscopy results.Comment: 8 pages, 5 figures, accepted by A&
The Earth as an extrasolar transiting planet: Earth's atmospheric composition and thickness revealed by Lunar eclipse observations
An important goal within the quest for detecting an Earth-like extrasolar
planet, will be to identify atmospheric gaseous bio-signatures. Observations of
the light transmitted through the Earth's atmosphere, as for an extrasolar
planet, will be the first step for future comparisons. We have completed
observations of the Earth during a Lunar eclipse, a unique situation similar to
that of a transiting planet. We aim at showing what species could be detected
in its atmosphere at optical wavelengths, where a lot of photons are available
in the masked stellar light. We present observations of the 2008 August 16 Moon
eclipse performed with the SOPHIE spectrograph at the Observatoire de
Haute-Provence. Locating the spectrograph fibers in the penumbra of the
eclipse, the Moon irradiance is then a mix of direct, unabsorbed Sun light and
solar light that has passed through the Earth's limb. This mixture essentially
reproduces what is recorded during the transit of an extrasolar planet. We
report here the clear detection of several Earth atmospheric compounds in the
transmission spectra, such as ozone, molecular oxygen, and neutral sodium as
well as molecular nitrogen and oxygen through the Rayleigh signature. Moreover,
we present a method that allows us to derive the thickness of the atmosphere
versus the wavelength for penumbra eclipse observations. We quantitatively
evaluate the altitude at which the atmosphere becomes transparent for important
species like molecular oxygen and ozone, two species thought to be tightly
linked to the presence of life. The molecular detections presented here are an
encouraging first attempt, necessary to better prepare for the future of
extremely-large telescopes and transiting Earth-like planets. Instruments like
SOPHIE will be mandatory when characterizing the atmospheres of transiting
Earth-like planets from the ground and searching for bio-marker signatures.Comment: 15 pages, 14 figures, 2 tables. Accepted for publication in Astronomy
and Astrophysic
Precision Astrometry of a Sample of Speckle Binaries and Multiples with the Adaptive Optics Facilities at the Hale and Keck II Telescopes
Using the adaptive optics facilities at the 200-in Hale and 10-m Keck II, we
observed in the near infrared a sample of 12 binary and multiple stars and one
open cluster. We used the near diffraction limited images of these systems to
measure the relative separations and position angles between their components.
In this paper, we investigate and correct for the influence of the differential
chromatic refraction and chip distortions on our relative astrometric
measurements. Over one night, we achieve an astrometric precision typically
well below 1 miliarcsecond and occasionally as small as 40 microarcseconds.
Such a precision is in principle sufficient to astrometrically detect planetary
mass objects around the components of nearby binary and multiple stars. Since
we have not had sufficiently large data sets for the observed sample of stars
to detect planets, we provide the limits to planetary mass objects based on the
obtained astrometric precision.Comment: 18 pages, 8 figures, 9 tables, to appear in MNRA
Uncertainties in models of stellar structure and evolution
Numerous physical aspects of stellar physics have been presented in Ses- sion
2 and the underlying uncertainties have been tentatively assessed. We try here
to highlight some specific points raised after the talks and during the general
discus- sion at the end of the session and eventually at the end of the
workshop. A table of model uncertainties is then drawn with the help of the
participants in order to give the state of the art in stellar modeling
uncertainties as of July 2013.Comment: Proc. of the workshop "Asteroseismology of stellar populations in the
Milky Way" (Sesto, 22-26 July 2013), Astrophysics and Space Science
Proceedings, (eds. A. Miglio, L. Girardi, P. Eggenberger, J. Montalban
Physical activity to improve cognition in older adults: can physical activity programs enriched with cognitive challenges enhance the effects? A systematic review and meta-analysis
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