752 research outputs found
Reconstructed Rough Growing Interfaces; Ridgeline Trapping of Domain Walls
We investigate whether surface reconstruction order exists in stationary
growing states, at all length scales or only below a crossover length, . The later would be similar to surface roughness in growing crystal
surfaces; below the equilibrium roughening temperature they evolve in a
layer-by-layer mode within a crossover length scale , but are always
rough at large length scales. We investigate this issue in the context of KPZ
type dynamics and a checker board type reconstruction, using the restricted
solid-on-solid model with negative mono-atomic step energies. This is a
topology where surface reconstruction order is compatible with surface
roughness and where a so-called reconstructed rough phase exists in
equilibrium. We find that during growth, reconstruction order is absent in the
thermodynamic limit, but exists below a crossover length , and that this local order fluctuates critically. Domain walls become
trapped at the ridge lines of the rough surface, and thus the reconstruction
order fluctuations are slaved to the KPZ dynamics
Crossover Scaling Functions in One Dimensional Dynamic Growth Models
The crossover from Edwards-Wilkinson () to KPZ () type growth is
studied for the BCSOS model. We calculate the exact numerical values for the
and massgap for using the master equation. We predict
the structure of the crossover scaling function and confirm numerically that
and , with . KPZ type growth is
equivalent to a phase transition in meso-scopic metallic rings where attractive
interactions destroy the persistent current; and to endpoints of facet-ridges
in equilibrium crystal shapes.Comment: 11 pages, TeX, figures upon reques
Dry matter yield and herbage quality of field margin vegetation as a function of vegetation development and management regime
AbstractDry matter (DM] yield and herbage quality of unfertilized mown field margin strips were studied during early succession in a field experiment over a period of three years. The experiment aimed to maximize botanical diversity and was conducted at two different locations with contrasting soil type and comprised four vegetation types (spontaneously regenerated versus sown vegetation) and three herbage removal strategies (herbage left versus herbage removed). The experimental factors investigated were location, vegetation and herbage removal. Margin strips were mown twice a year with a late first cut around 15 June and a regrowth cut around 15 September to meet nature conservation objectives. Average DM yield over the first three years was not significantly affected by herbage removal but increased significantly over time, irrespective of vegetation or herbage removal. Initially, sown margin strips significantly outyielded unsown margin strips, but differences in DM yield converged over time. The mid-June cut yielded significantly more than the regrowth cut but its herbage quality was significantly lower. Herbage from the unsown margin strip had a significantly better forage quality than herbage from sown margin strips. Forage quality decreased over time, irrespective of location or vegetation. Changes over time in DM yield and quality were attributed to changes in species composition. The herbage quality of field margins was lower than the herbage quality of intensively managed grassland, limiting its use in rations for highly productive livestock
Distressed personality is associated with lower psychological well-being and life satisfaction, but not disability or disease activity in rheumatoid arthritis patients
The distressed personality type (“type D personality”) has been shown to be associated with low quality of life and higher morbidity and mortality in various patient groups. Because the role of type D personality is unknown in patients with rheumatoid arthritis (RA), the aim of the present study was to investigate the association of type D personality with aspects of quality of life and disease activity in RA patients. In addition, a potential buffering effect by accepting mindfulness was examined. Participants were 147 patients between 22 and 87 years of age. Patients completed relevant questionnaires at home and the disease activity score was determined. After controlling for potentially confounding variables, multivariate analyses of covariance showed an association of type D personality with a lower satisfaction with life (p < 0.001) and a lower psychological well-being (p < 0.001), but not disease activity in RA patients. Although mindfulness was associated with a higher satisfaction with life (p = 0.02) and positive mood (p = 0.01), it did not diminish the unfavourable associations between type D and well-being. In conclusion, although type D personality is related with lower well-being, it does not seem to be associated with disability or disease activity in RA patients
Anomalous Roughness in Dimer-Type Surface Growth
We point out how geometric features affect the scaling properties of
non-equilibrium dynamic processes, by a model for surface growth where
particles can deposit and evaporate only in dimer form, but dissociate on the
surface. Pinning valleys (hill tops) develop spontaneously and the surface
facets for all growth (evaporation) biases. More intriguingly, the scaling
properties of the rough one dimensional equilibrium surface are anomalous. Its
width, , diverges with system size , as
instead of the conventional universal value . This originates
from a topological non-local evenness constraint on the surface configurations.Comment: Published version in PR
Solitonic excitations in the Haldane phase of a S=1 chain
We study low-lying excitations in the 1D antiferromagnetic
valence-bond-solid (VBS) model. In a numerical calculation on finite systems
the lowest excitations are found to form a discrete triplet branch, separated
from the higher-lying continuum. The dispersion of these triplet excitations
can be satisfactorily reproduced by assuming approximate wave functions. These
wave functions are shown to correspond to moving hidden domain walls, i.e. to
one-soliton excitations.Comment: RevTex 3.0, 24 pages, 2 figures on request by fax or mai
Crossover from Isotropic to Directed Percolation
Directed percolation is one of the generic universality classes for dynamic
processes. We study the crossover from isotropic to directed percolation by
representing the combined problem as a random cluster model, with a parameter
controlling the spontaneous birth of new forest fires. We obtain the exact
crossover exponent at using Coulomb gas methods in 2D.
Isotropic percolation is stable, as is confirmed by numerical finite-size
scaling results. For , the stability seems to change. An intuitive
argument, however, suggests that directed percolation at is unstable and
that the scaling properties of forest fires at intermediate values of are
in the same universality class as isotropic percolation, not only in 2D, but in
all dimensions.Comment: 4 pages, REVTeX, 4 epsf-emedded postscript figure
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