913 research outputs found
Metastable states of the Ising chain with Kawasaki dynamics
We consider a ferromagnetic Ising chain evolving under Kawasaki dynamics at
zero temperature. We investigate the statistics of the metastable
configurations in which the system gets blocked (statistics of energy, spin
correlations, distribution of domain sizes). A systematic comparison is made
with analytical predictions for the ensemble of all blocked configurations
taken with equal a priori weights (Edwards approach).Comment: 22 pages, 3 Tables, 6 Figure
Statistics of the occupation time for a class of Gaussian Markov processes
We revisit the work of Dhar and Majumdar [Phys. Rev. E 59, 6413 (1999)] on
the limiting distribution of the temporal mean M_{t}=t^{-1}\int_{0}^{t}du
\sign y_{u}, for a Gaussian Markovian process depending on a parameter
, which can be interpreted as Brownian motion in the scale of time
. This quantity, for short the mean `magnetization', is
simply related to the occupation time of the process, that is the length of
time spent on one side of the origin up to time t. Using the fact that the
intervals between sign changes of the process form a renewal process in the
time scale t', we determine recursively the moments of the mean magnetization.
We also find an integral equation for the distribution of . This allows
a local analysis of this distribution in the persistence region ,
as well as its asymptotic analysis in the regime where is large. We
finally put the results thus found in perspective with those obtained by Dhar
and Majumdar by another method, based on a formalism due to Kac.Comment: latex, 31 page
Segment Grammar: A formalism for incremental sentence generation
Incremental sentence generation imposes special constraints on the representation of the grammar and the design of the formulator (the module which is responsible for constructing the syntactic and morphological structure). In the model of natural speech production presented here, a formalism called Segment Grammar is used for the representation of linguistic knowledge. We give a definition of this formalism and present a formulator design which relies on it. Next, we present an object- oriented implementation of Segment Grammar. Finally, we compare Segment Grammar with other formalisms
Safety and tolerability of etravirine (ETR; TMC125) in hepatitis B and/or C co-infected patients in DUET-1 and DUET-2: pooled 48-week results
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Internal rotation of red giants by asteroseismology
We present an asteroseismic approach to study the dynamics of the stellar
interior in red-giant stars by asteroseismic inversion of the splittings
induced by the stellar rotation on the oscillation frequencies. We show
preliminary results obtained for the red giant KIC4448777 observed by the space
mission Kepler.Comment: 3 pages, 4 figures, the 40th Liege International Astrophysical
Colloquium Liac40, 'Ageing low mass stars: from red giants to white dwarfs',
to be published on EPJ Web of Conference
Partial survival and inelastic collapse for a randomly accelerated particle
We present an exact derivation of the survival probability of a randomly
accelerated particle subject to partial absorption at the origin. We determine
the persistence exponent and the amplitude associated to the decay of the
survival probability at large times. For the problem of inelastic reflection at
the origin, with coefficient of restitution , we give a new derivation of
the condition for inelastic collapse, , and determine
the persistence exponent exactly.Comment: 6 page
Sign-time distribution for a random walker with a drifting boundary
We present a derivation of the exact sign-time distribution for a random
walker in the presence of a boundary moving with constant velocity.Comment: 5 page
Physical Activity Status in Patients With Coronary Heart Disease: Results From the Cross-Sectional EUROASPIRE Surveys.
BACKGROUND: The study aim was to assess the physical activity levels as well as the intention to become physically active in patients with stable coronary heart disease (CHD) with a special focus on the association with their risk profile. METHODS: Analyses are based on the cross-sectional EUROASPIRE IV surveys. Information was available on 8966 patients in EUROASPIRE III and on 7998 patients in EUROASPIRE IV. Physical activity level according to patients risk profile and their medical management was assessed, the intention to become physically active was investigated and a time trend analysis was performed. RESULTS: A better cardiovascular risk profile as well as receiving physical activity advice or weight loss advice was associated with better physical activity levels. The physical activity status improved significantly over time, the proportion of patients reporting vigorous physical activity for at least 20 minutes ≥ 3 times/week increased from 14.1% to 20.2% (P < .001). Similarly, a significantly greater proportion of patients are in the maintenance stage (36.6% vs. 27.4%) and a smaller proportion in the precontemplation stage (43.2% vs. 52.3%). CONCLUSION: Although an increase was seen in the proportion of patients being adequately physical active, physical activity levels remain suboptimal in many CHD patients
Internal rotation of the red-giant star KIC 4448777 by means of asteroseismic inversion
In this paper we study the dynamics of the stellar interior of the early
red-giant star KIC 4448777 by asteroseismic inversion of 14 splittings of the
dipole mixed modes obtained from {\it Kepler} observations. In order to
overcome the complexity of the oscillation pattern typical of red-giant stars,
we present a procedure which involves a combination of different methods to
extract the rotational splittings from the power spectrum. We find not only
that the core rotates faster than the surface, confirming previous inversion
results generated for other red giants (Deheuvels et al. 2012,2014), but we
also estimate the variation of the angular velocity within the helium core with
a spatial resolution of and verify the hypothesis of a sharp
discontinuity in the inner stellar rotation (Deheuvels et al. 2014). The
results show that the entire core rotates rigidly with an angular velocity of
about ~nHz and provide evidence for an
angular velocity decrease through a region between the helium core and part of
the hydrogen burning shell; however we do not succeed to characterize the
rotational slope, due to the intrinsic limits of the applied techniques. The
angular velocity, from the edge of the core and through the hydrogen burning
shell, appears to decrease with increasing distance from the center, reaching
an average value in the convective envelope of
~nHz. Hence, the core in KIC~4448777 is
rotating from a minimum of 8 to a maximum of 17 times faster than the envelope.
We conclude that a set of data which includes only dipolar modes is sufficient
to infer quite accurately the rotation of a red giant not only in the dense
core but also, with a lower level of confidence, in part of the radiative
region and in the convective envelope.Comment: accepted for publication on Ap
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