420 research outputs found
Five-year follow-up of bilateral stimulation of the subthalamic nucleus in advanced Parkinson's disease
Background: Although the short-term benefits of bilateral stimulation of the subthalamic nucleus in patients with advanced Parkinson's disease have been well documented, the long-term outcomes of the procedure are unknown.
Methods: We conducted a five-year prospective study of the first 49 consecutive patients whom we treated with bilateral stimulation of the subthalamic nucleus. Patients were assessed at one, three, and five years with levodopa (on medication) and without levodopa (off medication), with use of the Unified Parkinson's Disease Rating Scale. Seven patients did not complete the study: three died, and four were lost to follow-up.
Results: As compared with base line, the patients' scores at five years for motor function while off medication improved by 54 percent (P<0.001) and those for activities of daily living improved by 49 percent (P<0.001). Speech was the only motor function for which off-medication scores did not improve. The scores for motor function on medication did not improve one year after surgery, except for the dyskinesia scores. On-medication akinesia, speech, postural stability, and freezing of gait worsened between year 1 and year 5 (P<0.001 for all comparisons). At five years, the dose of dopaminergic treatment and the duration and severity of levodopa-induced dyskinesia were reduced, as compared with base line (P<0.001 for each comparison). The average scores for cognitive performance remained unchanged, but dementia developed in three patients after three years. Mean depression scores remained unchanged. Severe adverse events included a large intracerebral hemorrhage in one patient. One patient committed suicide.
Conclusions: Patients with advanced Parkinson's disease who were treated with bilateral stimulation of the subthalamic nucleus had marked improvements over five years in motor function while off medication and in dyskinesia while on medication. There was no control group, but worsening of akinesia, speech, postural stability, freezing of gait, and cognitive function between the first and the fifth year is consistent with the natural history of Parkinson's disease
Non-uniqueness in conformal formulations of the Einstein constraints
Standard methods in non-linear analysis are used to show that there exists a
parabolic branching of solutions of the Lichnerowicz-York equation with an
unscaled source. We also apply these methods to the extended conformal thin
sandwich formulation and show that if the linearised system develops a kernel
solution for sufficiently large initial data then we obtain parabolic solution
curves for the conformal factor, lapse and shift identical to those found
numerically by Pfeiffer and York. The implications of these results for
constrained evolutions are discussed.Comment: Arguments clarified and typos corrected. Matches published versio
A fast empirical method for galaxy shape measurements in weak lensing surveys
We describe a simple and fast method to correct ellipticity measurements of
galaxies from the distortion by the instrumental and atmospheric point spread
function (PSF), in view of weak lensing shear measurements. The method performs
a classification of galaxies and associated PSFs according to measured shape
parameters, and corrects the measured galaxy ellipticites by querying a large
lookup table (LUT), built by supervised learning. We have applied this new
method to the GREAT10 image analysis challenge, and present in this paper a
refined solution that obtains the competitive quality factor of Q = 104,
without any shear power spectrum denoising or training. Of particular interest
is the efficiency of the method, with a processing time below 3 ms per galaxy
on an ordinary CPU.Comment: 8 pages, 6 figures. Metric values updated according to the final
GREAT10 analysis software (Kitching et al. 2012, MNRAS 423, 3163-3208), no
qualitative changes. Associated code available at
http://lastro.epfl.ch/megalu
A practical guide to troubleshooting pallidal deep brain stimulation issues in patients with dystonia
High frequency deep brain stimulation (DBS) of the internal portion of the globus pallidus has, in the last two decades, become a mainstream therapy for the management of medically-refractory dystonia syndromes. Such increasing uptake places an onus on movement disorder physicians to become familiar with this treatment modality, in particular optimal patient selection for the procedure and how to troubleshoot problems relating to sub-optimal efficacy and therapy-related side effects. Deep brain stimulation for dystonic conditions presents some unique challenges. For example, the frequent lack of immediate change in clinical status following stimulation alterations means that programming often relies on personal experience and local practice rather than real-time indicators of efficacy. Further, dystonia is a highly heterogeneous disorder, making the development of unifying guidelines and programming algorithms for DBS in this population difficult. Consequently, physicians may feel less confident in managing DBS for dystonia as compared to other indications e.g. Parkinson's disease. In this review, we integrate our years of personal experience of the programming of DBS systems for dystonia with a critical appraisal of the literature to produce a practical guide for troubleshooting common issues encountered in patients with dystonia treated with DBS, in the hope of improving the care for these patients
Fast-neutron induced background in LaBr3:Ce detectors
The response of a scintillation detector with a cylindrical 1.5-inch LaBr3:Ce
crystal to incident neutrons has been measured in the energy range En = 2-12
MeV. Neutrons were produced by proton irradiation of a Li target at Ep = 5-14.6
MeV with pulsed proton beams. Using the time-of-flight information between
target and detector, energy spectra of the LaBr3:Ce detector resulting from
fast neutron interactions have been obtained at 4 different neutron energies.
Neutron-induced gamma rays emitted by the LaBr3:Ce crystal were also measured
in a nearby Ge detector at the lowest proton beam energy. In addition, we
obtained data for neutron irradiation of a large-volume high-purity Ge detector
and of a NE-213 liquid scintillator detector, both serving as monitor detectors
in the experiment. Monte-Carlo type simulations for neutron interactions in the
liquid scintillator, the Ge and LaBr3:Ce crystals have been performed and
compared with measured data. Good agreement being obtained with the data, we
present the results of simulations to predict the response of LaBr3:Ce
detectors for a range of crystal sizes to neutron irradiation in the energy
range En = 0.5-10 MeVComment: 28 pages, 10 figures, 4 Table
A comparison of the strong lensing properties of the Sersic and the NFW profiles
We investigate the strong lensing properties of the Sersic profile as an
alternative to the NFW profile, focusing on applications to lens modelling of
clusters. Given an underlying Sersic dark matter profile, we study whether an
NFW profile can provide an acceptable fit to strong lensing constraints in the
form of single or multiple measured Einstein radii. We conclude that although
an NFW profile that fits the lensing constraints can be found in many cases,
the derived parameters may be biased. In particular, we find that for n~2,
which corresponds to massive clusters, the mass at r_200 of the best fit NFW is
overestimated (by a factor of ~2) and the concentration is very low (c~2). The
differences are important enough to warrant the inclusion of Sersic profile for
future analysis of strong lensing clusters.Comment: 19 pages (single column format), 11 figures. Accepted for publication
by JCA
Modelling of the Complex CASSOWARY/SLUGS Gravitational Lenses
We present the first high-resolution images of CSWA 31, a gravitational lens
system observed as part of the SLUGS (Sloan Lenses Unravelled by Gemini
Studies) program. These systems exhibit complex image structure with the
potential to strongly constrain the mass distribution of the massive lens
galaxies, as well as the complex morphology of the sources. In this paper, we
describe the strategy used to reconstruct the unlensed source profile and the
lens galaxy mass profiles. We introduce a prior distribution over
multi-wavelength sources that is realistic as a representation of our knowledge
about the surface brightness profiles of galaxies and groups of galaxies. To
carry out the inference computationally, we use Diffusive Nested Sampling, an
efficient variant of Nested Sampling that uses Markov Chain Monte Carlo (MCMC)
to sample the complex posterior distributions and compute the normalising
constant. We demonstrate the efficacy of this approach with the reconstruction
of the group-group gravitational lens system CSWA 31, finding the source to be
composed of five merging spiral galaxies magnified by a factor of 13.Comment: Accepted for publication in MNRA
On the evolution of environmental and mass properties of strong lens galaxies in COSMOS
Among the 100 strong lens candidates found in the COSMOS field, 20 with
redshifts in the range [0.34,1.13], feature multiple images of background
sources. Using the multi-wavelength coverage of the field and its spectroscopic
follow-up, we characterize the evolution with redshift of the environment and
of the dark-matter (DM) fraction of the lens galaxies. We present new redshift
of the strong lens candidates. The lens environment is characterized by the
projected 10 closest galaxies around each lens and by the number of galaxies
with a projected distance less than 1Mpc at the lens galaxy redshift. In both
cases, we perform similar measurements on a control sample of twin non-lens
early type galaxies (ETGs). In addition, we identify group members and field
galaxies in the X-ray and optical catalogs of galaxy groups. From those
catalogs, we measure the external shear contribution at the lens galaxy
positions. The systems are then modeled using a SIE plus the external shear due
to the groups. We observe that the average stellar mass of lens galaxies
increases with z and that the environment of lens galaxies is compatible with
that of the twins. During the lens modeling, we notice that, when let free, the
external shear points in a direction which is the mean direction of the
external shear due to groups and of the closest galaxy to the lens. We notice
that the DM fraction of the lens galaxies within the Einstein radius decreases
as the redshift increases. Given these, we conclude that, while the environment
of lens galaxies is compatible with that of non-lens ETGS, their mass
properties evolves significantly with redshift: it is still not clear whether
this advocates in favor of a stronger lensing bias toward massive objects at
high redshift or is simply representative of the high proportion of massive and
high stellar density galaxies at high redshift.Comment: Accepted for publication in A&A. Significant modifications in the
paper but similar conclusion
Non-invasive intervention for motor signs of Parkinson's disease: the effect of vibratory stimuli
A Bayesian approach to strong lensing modelling of galaxy clusters
In this paper, we describe a procedure for modelling strong lensing galaxy
clusters with parametric methods, and to rank models quantitatively using the
Bayesian evidence. We use a publicly available Markov chain Monte-Carlo (MCMC)
sampler ('Bayesys'), allowing us to avoid local minima in the likelihood
functions. To illustrate the power of the MCMC technique, we simulate three
clusters of galaxies, each composed of a cluster-scale halo and a set of
perturbing galaxy-scale subhalos. We ray-trace three light beams through each
model to produce a catalogue of multiple images, and then use the MCMC sampler
to recover the model parameters in the three different lensing configurations.
We find that, for typical Hubble Space Telescope (HST)-quality imaging data,
the total mass in the Einstein radius is recovered with ~1-5% error according
to the considered lensing configuration. However, we find that the mass of the
galaxies is strongly degenerated with the cluster mass when no multiple images
appear in the cluster centre. The mass of the galaxies is generally recovered
with a 20% error, largely due to the poorly constrained cut-off radius.
Finally, we describe how to rank models quantitatively using the Bayesian
evidence. We confirm the ability of strong lensing to constrain the mass
profile in the central region of galaxy clusters in this way. Ultimately, such
a method applied to strong lensing clusters with a very large number of
multiple images may provide unique geometrical constraints on cosmology. The
implementation of the MCMC sampler used in this paper has been done within the
framework of the Lenstool software package, which is publicly available.Comment: Accepted to "Gravitational Lensing" Focus Issue of the New Journal of
Physics (invited), 35 pages, 11 figures at reduced resolutio
- …