3,357 research outputs found
Properties of pattern formation and selection processes in nonequilibrium systems with external fluctuations
We extend the phase field crystal method for nonequilibrium patterning to
stochastic systems with external source where transient dynamics is essential.
It was shown that at short time scales the system manifests pattern selection
processes. These processes are studied by means of the structure function
dynamics analysis. Nonequilibrium pattern-forming transitions are analyzed by
means of numerical simulations.Comment: 15 poages, 8 figure
Flame propagation in random media
We introduce a phase-field model to describe the dynamics of a
self-sustaining propagating combustion front within a medium of randomly
distributed reactants. Numerical simulations of this model show that a flame
front exists for reactant concentration , while its vanishing at
is consistent with mean-field percolation theory. For , we find
that the interface associated with the diffuse combustion zone exhibits kinetic
roughening characteristic of the Kardar-Parisi-Zhang equation.Comment: 4, LR541
Interviewing suspects: examining the association between skills, questioning, evidence disclosure, and interview outcomes
The interviewing of suspects is an important element in the investigation of crime. However, studies concerning actual performance of investigators when undertaking such interviews remain sparse. Nevertheless, in England and Wales, since the introduction of a prescribed framework over 20 years ago, field studies have generally shown an improvement in interviewing performance, notwithstanding ongoing concerns largely relating to the more demanding aspects (such as building/maintaining rapport, intermittent summarising and the logical development of topics). Using a sample of 70 real-life interviews, the present study examined questioning and various evidence disclosure strategies (which have also been found demanding), examining their relationships between interview skills and interview outcomes. It was found that when evidence was disclosed gradually (but revealed later), interviews were generally both more skilled and involved the gaining of comprehensive accounts, whereas when evidence was disclosed either early or very late, interviews were found to be both less skilled and less likely to involve this outcome. These findings contribute towards an increased research base for the prescribed framework
Evaluation of early and late presentation of patients with ocular mucous membrane pemphigoid to two major tertiary referral hospitals in the United Kingdom
PURPOSE: Ocular mucous membrane pemphigoid (OcMMP) is a sight-threatening autoimmune disease in which referral to specialists units for further management is a common practise. This study aims to describe referral patterns, disease phenotype and management strategies in patients who present with either early or established disease to two large tertiary care hospitals in the United Kingdom.\ud
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PATIENTS AND METHODS: In all, 54 consecutive patients with a documented history of OcMMP were followed for 24 months. Two groups were defined: (i) early-onset disease (EOD:<3 years, n=26, 51 eyes) and (ii) established disease (EstD:>5 years, n=24, 48 eyes). Data were captured at first clinic visit, and at 12 and 24 months follow-up. Information regarding duration, activity and stage of disease, visual acuity (VA), therapeutic strategies and clinical outcome were analysed.\ud
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RESULTS: Patients with EOD were younger and had more severe conjunctival inflammation (76% of inflamed eyes) than the EstD group, who had poorer VA (26.7%=VA<3/60, P<0.01) and more advanced disease. Although 40% of patients were on existing immunosuppression, 48% required initiation or switch to more potent immunotherapy. In all, 28% (14) were referred back to the originating hospitals for continued care. Although inflammation had resolved in 78% (60/77) at 12 months, persistence of inflammation and progression did not differ between the two phenotypes. Importantly, 42% demonstrated disease progression in the absence of clinically detectable inflammation.\ud
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CONCLUSIONS: These data highlight that irrespective of OcMMP phenotype, initiation or escalation of potent immunosuppression is required at tertiary hospitals. Moreover, the conjunctival scarring progresses even when the eye remains clinically quiescent. Early referral to tertiary centres is recommended to optimise immunosuppression and limit long-term ocular damage.\ud
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Extreme clonal diversity and divergence in populations of a selfing hermaphroditic fish.
High-speed silicon-organic hybrid (SOH) modulator with 1,6 fJ/bit and 180 pm/V in-device nonlinearity
Transformation kinetics of alloys under non-isothermal conditions
The overall solid-to-solid phase transformation kinetics under non-isothermal
conditions has been modeled by means of a differential equation method. The
method requires provisions for expressions of the fraction of the transformed
phase in equilibrium condition and the relaxation time for transition as
functions of temperature. The thermal history is an input to the model. We have
used the method to calculate the time/temperature variation of the volume
fraction of the favored phase in the alpha-to-beta transition in a zirconium
alloy under heating and cooling, in agreement with experimental results. We
also present a formulation that accounts for both additive and non-additive
phase transformation processes. Moreover, a method based on the concept of path
integral, which considers all the possible paths in thermal histories to reach
the final state, is suggested.Comment: 16 pages, 7 figures. To appear in Modelling Simul. Mater. Sci. En
Scaling, Propagation, and Kinetic Roughening of Flame Fronts in Random Media
We introduce a model of two coupled reaction-diffusion equations to describe
the dynamics and propagation of flame fronts in random media. The model
incorporates heat diffusion, its dissipation, and its production through
coupling to the background reactant density. We first show analytically and
numerically that there is a finite critical value of the background density,
below which the front associated with the temperature field stops propagating.
The critical exponents associated with this transition are shown to be
consistent with mean field theory of percolation. Second, we study the kinetic
roughening associated with a moving planar flame front above the critical
density. By numerically calculating the time dependent width and equal time
height correlation function of the front, we demonstrate that the roughening
process belongs to the universality class of the Kardar-Parisi-Zhang interface
equation. Finally, we show how this interface equation can be analytically
derived from our model in the limit of almost uniform background density.Comment: Standard LaTeX, no figures, 29 pages; (to appear in J. Stat. Phys.
vol.81, 1995). Complete file available at
http://www.physics.helsinki.fi/tft/tft.html or anonymous ftp at
ftp://rock.helsinki.fi/pub/preprints/tft
Phase-field approach to heterogeneous nucleation
We consider the problem of heterogeneous nucleation and growth. The system is
described by a phase field model in which the temperature is included through
thermal noise. We show that this phase field approach is suitable to describe
homogeneous as well as heterogeneous nucleation starting from several general
hypotheses. Thus we can investigate the influence of grain boundaries,
localized impurities, or any general kind of imperfections in a systematic way.
We also put forward the applicability of our model to study other physical
situations such as island formation, amorphous crystallization, or
recrystallization.Comment: 8 pages including 7 figures. Accepted for publication in Physical
Review
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