2,164 research outputs found
Algebras for parameterised monads
Parameterised monads have the same relationship to adjunctions with parameters as monads do to adjunctions. In this paper, we investigate algebras for parameterised monads. We identify the Eilenberg-Moore category of algebras for parameterised monads and prove a generalisation of Beck’s theorem characterising this category. We demonstrate an application of this theory to the semantics of type and effect systems
On high energy tails in inelastic gases
We study the formation of high energy tails in a one-dimensional kinetic
model for granular gases, the so-called Inelastic Maxwell Model. We introduce a
time- discretized version of the stochastic process, and show that continuous
time implies larger fluctuations of the particles energies. This is due to a
statistical relation between the number of inelastic collisions undergone by a
particle and its average energy. This feature is responsible for the high
energy tails in the model, as shown by computer simulations and by analytical
calculations on a linear Lorentz model.Comment: 8 pages, 2 figures, submitted to physica
Flow curves of colloidal dispersions close to the glass transition: Asymptotic scaling laws in a schematic model of mode coupling theory
The flow curves, viz. the curves of stationary stress under steady shearing,
are obtained close to the glass transition in dense colloidal dispersions using
asymptotic expansions in a schematic model of mode coupling theory. The shear
thinning of the viscosity in fluid states and the yielding of glassy states is
discussed. At the transition between fluid and shear-molten glass, simple and
generalized Herschel-Bulkley laws are derived with power law exponents that can
be computed for different particle interactions from the equilibrium structure
factor.Comment: 14 pages, 14 figures, 4 tables, Eur. Phys. J. E (submitted
Langevin Simulations of Two Dimensional Vortex Fluctuations: Anomalous Dynamics and a New -exponent
The dynamics of two dimensional (2D) vortex fluctuations are investigated
through simulations of the 2D Coulomb gas model in which vortices are
represented by soft disks with logarithmic interactions. The simulations
trongly support a recent suggestion that 2D vortex fluctuations obey an
intrinsic anomalous dynamics manifested in a long range 1/t-tail in the vortex
correlations. A new non-linear IV-exponent a, which is different from the
commonly used AHNS exponent, a_AHNS and is given by a = 2a_AHNS - 3, is
confirmed by the simulations. The results are discussed in the context of
earlier simulations, experiments and a phenomenological description.Comment: Submitted to PRB, RevTeX format, 28 pages and 13 figures, figures in
postscript format are available at http://www.tp.umu.se/~holmlund/papers.htm
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Is anxiety associated with negative interpretations of ambiguity in children and adolescents? A systematic review and meta-analysis
Background
The tendency to interpret ambiguity as threat (‘negative interpretation’) has been implicated in cognitive models of anxiety. A significant body of research has examined the association between anxiety and negative interpretation, and reviews suggest there is a robust positive association in adults. However, evidence with children and adolescents has been inconsistent. This study aimed to provide a systematic quantitative assessment of the association between anxiety and negative interpretation in children and adolescents.
Methods
Following systematic searches and screening for eligibility, 345 effects sizes from 77 studies were meta-analysed.
Results
Overall a medium positive association was found between anxiety and negative interpretation in children and adolescents (d ̂ = 0.62). Two variables significantly moderated this effect. Specifically, the association increased in strength with increasing age and when the content of ambiguous scenarios matched the anxiety subtype under investigation.
Conclusions
Results extend findings from adult literature by demonstrating an association in children and adolescents with evidence for content specificity in the association. Age effects imply a role for development. Results raise considerations for when and for whom clinical treatments for anxiety focusing on interpretation bias are appropriate. The vast majority of studies included in the review have used correlational designs and there are a limited number of studies with you ng children. The results should be considered with these limitations in mind
Explosive events - swirling transition region jets
In this paper, we extend our earlier work to provide additional evidence for
an alternative scenario to explain the nature of so-called `explosive events'.
The bi-directed, fast Doppler motion of explosive events observed
spectroscopically in the transition region emission is classically interpreted
as a pair of bidirectional jets moving upward and downward from a reconnection
site. We discuss the problems of such a model. In our previous work, we focused
basically on the discrepancy of fast Doppler motion without detectable motion
in the image plane. We now suggest an alternative scenario for the explosive
events, based on our observations of spectral line tilts and bifurcated
structure in some events. Both features are indicative of rotational motion in
narrow structures. We explain the bifurcation as the result of rotation of
hollow cylindrical structures and demonstrate that such a sheath model can also
be applied to explain the nature of the puzzling `explosive events'. We find
that the spectral tilt, the lack of apparent motion, the bifurcation, and a
rapidly growing number of direct observations support an alternative scenario
of linear, spicular-sized jets with a strong spinning motion.Comment: 9 pages, 3 figures, accepted for publication in Solar Physic
Time--Distance Helioseismology Data Analysis Pipeline for Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory (SDO/HMI) and Its Initial Results
The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory
(SDO/HMI) provides continuous full-disk observations of solar oscillations. We
develop a data-analysis pipeline based on the time-distance helioseismology
method to measure acoustic travel times using HMI Doppler-shift observations,
and infer solar interior properties by inverting these measurements. The
pipeline is used for routine production of near-real-time full-disk maps of
subsurface wave-speed perturbations and horizontal flow velocities for depths
ranging from 0 to 20 Mm, every eight hours. In addition, Carrington synoptic
maps for the subsurface properties are made from these full-disk maps. The
pipeline can also be used for selected target areas and time periods. We
explain details of the pipeline organization and procedures, including
processing of the HMI Doppler observations, measurements of the travel times,
inversions, and constructions of the full-disk and synoptic maps. Some initial
results from the pipeline, including full-disk flow maps, sunspot subsurface
flow fields, and the interior rotation and meridional flow speeds, are
presented.Comment: Accepted by Solar Physics topical issue 'Solar Dynamics Observatory
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