1,993 research outputs found
Asymptotic behavior and uniqueness for an ultrahyperbolic equation with variable coefficients
AbstractThis paper describes the asymptotic behavior of solutions of a class of semilinear ultrahyperbolic equations with variable coefficients. One consequence of the general analysis is a uniqueness theorem for a mixed boundary-value problem. Another demonstrates unique continuation at infinity. These results extend previous work by M. H. Protter, [Asymptotic decay for ultrahyperbolic operators, in âContributions to Analysisâ (Lars Ahlfors et al., Eds.), Academic Press, New York, 1974], and A. C. Murray and M. M. Protter, [Indiana U. Math. J. 24 (1974), 115â130], on a more restricted class of equations
A Randomized Controlled Trial on Very Early Speech and Language Therapy in Acute Stroke Patients with Aphasia
Background: Aphasia affects one third of acute stroke patients. There is a considerable spontaneous recovery in aphasia, but impaired communication ability remains a great problem. Communication difficulties are an impediment to rehabilitation. Early treatment of the language deficits leading to increased communication ability would improve rehabilitation. The aim of this study is to elucidate the efficacy of very early speech and language therapy (SLT) in acute stroke patients with aphasia. Methods: A prospective, open, randomized, controlled trial was carried out with blinded endpoint evaluation of SLT, starting within 2 days of stroke onset and lasting for 21 days. 123 consecutive patients with acute, first-ever ischemic stroke and aphasia were randomized. The SLT treatment was Language Enrichment Therapy, and the aphasia tests used were the Norsk grunntest for afasi (NGA) and the Amsterdam-Nijmegen everyday language test (ANELT), both performed by speech pathologists, blinded for randomization. Results: The primary outcome, as measured by ANELT at day 21, was 1.3 in the actively treated patient group and 1.2 among controls. NGA led to similar results in both groups. Patients with a higher level of education (>12 years) improved more on ANELT by day 21 than those with Conclusions: Very early intensive SLT with the Language Enrichment Therapy program over 21 days had no effect on the degree of aphasia in unselected acute aphasic stroke patients. In aphasic patients with more fluency, SLT resulted in a significant improvement as compared to controls. A higher educational level of >12 years was beneficial
Recommended from our members
Scale-invariant moving finite elements for nonlinear partial differential equations in two dimensions
A scale-invariant moving finite element method is proposed for the adaptive solution of nonlinear partial differential equations. The mesh movement is based on a finite element discretisation of a scale-invariant conservation principle incorporating a monitor function, while the time discretisation of the resulting system of ordinary differential equations is carried out using a scale-invariant time-stepping which yields uniform local accuracy in time.
The accuracy and reliability of the algorithm are successfully tested against exact self-similar solutions where available, and otherwise against a state-of-the-art h-refinement scheme for solutions of a two-dimensional porous medium equation problem with a moving boundary. The monitor functions used are the dependent variable and a monitor related to the surface area of the solution manifold
Ridge Formation and De-Spinning of Iapetus via an Impact-Generated Satellite
We present a scenario for building the equatorial ridge and de-spinning
Iapetus through an impact-generated disk and satellite. This impact puts debris
into orbit, forming a ring inside the Roche limit and a satellite outside. This
satellite rapidly pushes the ring material down to the surface of Iapetus, and
then itself tidally evolves outward, thereby helping to de-spin Iapetus. This
scenario can de-spin Iapetus an order of magnitude faster than when tides due
to Saturn act alone, almost independently of its interior geophysical
evolution. Eventually, the satellite is stripped from its orbit by Saturn. The
range of satellite and impactor masses required is compatible with the
estimated impact history of Iapetus.Comment: 19 pages, 3 figures; Icarus, in pres
The SuperCOSMOS Sky Survey. Paper III: Astrometry
In this, the third in a series of three papers concerning the SuperCOSMOS Sky
Survey, we describe the astrometric properties of the database. We describe the
algorithms employed in the derivation of the astrometric parameters of the
data, and demonstrate their accuracies by comparison with external datasets
using the first release of data, the South Galactic Cap survey. We show that
the celestial coordinates, which are tied to the International Celestial
Reference Frame via the Tycho-2 reference catalogue, are accurate to better
than +/- 0.2 arcsec at J,R=19,18 rising to +/- 0.3 arcsec at J,R=22,21 with
positional dependent systematic effects from bright to faint magnitudes at the
+/- 0.1 arcsec level. The proper motion measurements are shown to be accurate
to typically +/- 10 mas/yr at J,R=19,18 rising to +/- 50 mas/yr at J,R=22,21
and are tied to zero using the extragalactic reference frame. We show that the
zeropoint errors in the proper motions are 17 and are no
larger than 10 mas/yr for R < 17 mas/yr.Comment: 15 pages, 12 figures; accepted for publication in MNRA
Frozen spatial chaos induced by boundaries
We show that rather simple but non-trivial boundary conditions could induce
the appearance of spatial chaos (that is stationary, stable, but spatially
disordered configurations) in extended dynamical systems with very simple
dynamics. We exemplify the phenomenon with a nonlinear reaction-diffusion
equation in a two-dimensional undulated domain. Concepts from the theory of
dynamical systems, and a transverse-single-mode approximation are used to
describe the spatially chaotic structures.Comment: 9 pages, 6 figures, submitted for publication; for related work visit
http://www.imedea.uib.es/~victo
Topological Defects, Orientational Order, and Depinning of the Electron Solid in a Random Potential
We report on the results of molecular dynamics simulation (MD) studies of the
classical two-dimensional electron crystal in the presence disorder. Our study
is motivated by recent experiments on this system in modulation doped
semiconductor systems in very strong magnetic fields, where the magnetic length
is much smaller than the average interelectron spacing , as well as by
recent studies of electrons on the surface of helium. We investigate the low
temperature state of this system using a simulated annealing method. We find
that the low temperature state of the system always has isolated dislocations,
even at the weakest disorder levels investigated. We also find evidence for a
transition from a hexatic glass to an isotropic glass as the disorder is
increased. The former is characterized by quasi-long range orientational order,
and the absence of disclination defects in the low temperature state, and the
latter by short range orientational order and the presence of these defects.
The threshold electric field is also studied as a function of the disorder
strength, and is shown to have a characteristic signature of the transition.
Finally, the qualitative behavior of the electron flow in the depinned state is
shown to change continuously from an elastic flow to a channel-like, plastic
flow as the disorder strength is increased.Comment: 31 pages, RevTex 3.0, 15 figures upon request, accepted for
publication in Phys. Rev. B., HAF94MD
- âŠ