3,989 research outputs found
Group membership and staff turnover affect outcomes in group CBT for persistent pain
The effects of two contextual factors, group membership and staff turnover, on the outcome of group cognitive behavioral therapy (CBT) for persistent pain were investigated. The data came from end of treatment and one month follow-up assessments of 3050 individuals who attended an intensive group programme over sixteen years. Intraclass correlations (ICC) showed significant intragroup effects on self-efficacy (ICC = 0.16 at end of treatment; 0.12 at one month), catastrophizing (ICC = 0.06; 0.13) and distance walked (ICC = 0.20; 0.19). This underlines the importance of modelling group membership when analyzing data from group interventions. Linear regression showed that high periods of staff turnover were significantly related to poorer outcomes on self-efficacy and distance walked at end of treatment, with the effect on self-efficacy persisting to one month follow-up. Having demonstrated significant contextual effects in an existing data set, further research is needed to explore the mechanisms by which these effects operate
Balltracking: an highly efficient method for tracking flow fields
We present a method for tracking solar photospheric flows that is highly efficient, and demonstrate it using high resolution MDI continuum images. The method involves making a surface from the photospheric granulation data, and allowing many small floating tracers or balls to be moved around by the evolving granulation pattern. The results are tested against synthesised granulation with known flow fields and compared to the results produced by Local Correlation tracking (LCT). The results from this new method have similar accuracy to those produced by LCT. We also investigate the maximum spatial and temporal resolution of the velocity field that it is possible to extract, based on the statistical properties of the granulation data. We conclude that both methods produce results that are close to the maximum resolution possible from granulation data. The code runs very significantly faster than our similarly optimised LCT code, making real time applications on large data sets possible. The tracking method is not limited to photospheric flows, and will also work on any velocity field where there are visible moving features of known scale length
Fast algorithm for border bases of Artinian Gorenstein algebras
Given a multi-index sequence , we present a new efficient algorithm
to compute generators of the linear recurrence relations between the terms of
. We transform this problem into an algebraic one, by identifying
multi-index sequences, multivariate formal power series and linear functionals
on the ring of multivariate polynomials. In this setting, the recurrence
relations are the elements of the kerne l\sigma of the Hankel operator
$H$\sigma associated to . We describe the correspondence between
multi-index sequences with a Hankel operator of finite rank and Artinian
Gorenstein Algebras. We show how the algebraic structure of the Artinian
Gorenstein algebra \sigma\sigma yields the
structure of the terms $\sigma\alpha N nAK[x 1 ,. .. , xnIHIA$ and the tables of multiplication by the variables in these
bases. It is an extension of Berlekamp-Massey-Sakata (BMS) algorithm, with
improved complexity bounds. We present applications of the method to different
problems such as the decomposition of functions into weighted sums of
exponential functions, sparse interpolation, fast decoding of algebraic codes,
computing the vanishing ideal of points, and tensor decomposition. Some
benchmarks illustrate the practical behavior of the algorithm
Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere
We study horizontal supergranule-scale motions revealed by TRACE observation
of the chromospheric emission, and investigate the coupling between the
chromosphere and the underlying photosphere. A highly efficient
feature-tracking technique called balltracking has been applied for the first
time to the image sequences obtained by TRACE (Transition Region and Coronal
Explorer) in the passband of white light and the three ultraviolet passbands
centered at 1700 {\AA}, 1600 {\AA}, and 1550 {\AA}. The resulting velocity
fields have been spatially smoothed and temporally averaged in order to reveal
horizontal supergranule-scale motions that may exist at the emission heights of
these passbands. We find indeed a high correlation between the horizontal
velocities derived in the white-light and ultraviolet passbands. The horizontal
velocities derived from the chromospheric and photospheric emission are
comparable in magnitude. The horizontal motions derived in the UV passbands
might indicate the existence of a supergranule-scale magnetoconvection in the
chromosphere, which may shed new light on the study of mass and energy supply
to the corona and solar wind at the height of the chromosphere. However, it is
also possible that the apparent motions reflect the chromospheric brightness
evolution as produced by acoustic shocks which might be modulated by the
photospheric granular motions in their excitation process, or advected partly
by the supergranule-scale flow towards the network while propagating upward
from the photosphere. To reach a firm conclusion, it is necessary to
investigate the role of granular motions in the excitation of shocks through
numerical modeling, and future high-cadence chromospheric magnetograms must be
scrutinized.Comment: 5 figures, accepted by Astronomy & Astrophysic
FINITE SIZE SCALING FOR FIRST ORDER TRANSITIONS: POTTS MODEL
The finite-size scaling algorithm based on bulk and surface renormalization
of de Oliveira (1992) is tested on q-state Potts models in dimensions D = 2 and
3. Our Monte Carlo data clearly distinguish between first- and second-order
phase transitions. Continuous-q analytic calculations performed for small
lattices show a clear tendency of the magnetic exponent Y = D - beta/nu to
reach a plateau for increasing values of q, which is consistent with the
first-order transition value Y = D. Monte Carlo data confirm this trend.Comment: 5 pages, plain tex, 5 EPS figures, in file POTTS.UU (uufiles
Large-q expansion of the energy and magnetization cumulants for the two-dimensional q-state Potts model
We have calculated the large-q expansion for the energy cumulants and the
magnetization cumulants at the phase transition point in the two-dimensional
q-state Potts model to the 21st or 23rd order in using the finite
lattice method. The obtained series allow us to give very precise estimates of
the cumulants for on the first order transition point. The result
confirms us the correctness of the conjecture by Bhattacharya et al. on the
asymptotic behavior not only of the energy cumulants but also of the
magnetization cumulants for .Comment: 36 pages, LaTeX, 20 postscript figures, to appear in Nuclear Physics
Smc5/6: a link between DNA repair and unidirectional replication?
Of the three structural maintenance of chromosome (SMC) complexes, two directly regulate chromosome dynamics. The third, Smc5/6, functions mainly in homologous recombination and in completing DNA replication. The literature suggests that Smc5/6 coordinates DNA repair, in part through post-translational modification of uncharacterized target proteins that can dictate their subcellular localization, and that Smc5/6 also functions to establish DNA-damage-dependent cohesion. A nucleolar-specific Smc5/6 function has been proposed because Smc5/6 yeast mutants display penetrant phenotypes of ribosomal DNA (rDNA) instability. rDNA repeats are replicated unidirectionally. Here, we propose that unidirectional replication, combined with global Smc5/6 functions, can explain the apparent rDNA specificity
Potts q-color field theory and scaling random cluster model
We study structural properties of the q-color Potts field theory which, for
real values of q, describes the scaling limit of the random cluster model. We
show that the number of independent n-point Potts spin correlators coincides
with that of independent n-point cluster connectivities and is given by
generalized Bell numbers. Only a subset of these spin correlators enters the
determination of the Potts magnetic properties for q integer. The structure of
the operator product expansion of the spin fields for generic q is also
identified. For the two-dimensional case, we analyze the duality relation
between spin and kink field correlators, both for the bulk and boundary cases,
obtaining in particular a sum rule for the kink-kink elastic scattering
amplitudes.Comment: 27 pages; 6 figures. Published version, some comments and references
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