3,204 research outputs found
Distribution of Time-Averaged Observables for Weak Ergodicity Breaking
We find a general formula for the distribution of time-averaged observables
for systems modeled according to the sub-diffusive continuous time random walk.
For Gaussian random walks coupled to a thermal bath we recover ergodicity and
Boltzmann's statistics, while for the anomalous subdiffusive case a weakly
non-ergodic statistical mechanical framework is constructed, which is based on
L\'evy's generalized central limit theorem. As an example we calculate the
distribution of : the time average of the position of the particle,
for unbiased and uniformly biased particles, and show that exhibits
large fluctuations compared with the ensemble average .Comment: 5 pages, 2 figure
Monte Carlo evaluation of FADE approach to anomalous kinetics
In this paper we propose a comparison between the CTRW (Monte Carlo) and
Fractional Derivative approaches to the modelling of anomalous diffusion
phenomena in the presence of an advection field. Galilei variant and invariant
schemes are revised.Comment: 13 pages, 6 figure
A non-perturbative determination of Z_V and b_V for O(a) improved quenched and unquenched Wilson fermions
By considering the local vector current between nucleon states and imposing
charge conservation we determine, for improved Wilson fermions, its
renormalisation constant and quark mass improvement coefficient. The
computation is performed for both quenched and two flavour unquenched fermions.Comment: 3 pages, 4 figures, Lattice(2002)(improve
Transport Properties of Highly Aligned Polymer Light-Emitting-Diodes
We investigate hole transport in polymer light-emitting-diodes in which the
emissive layer is made of liquid-crystalline polymer chains aligned
perpendicular to the direction of transport. Calculations of the current as a
function of time via a random-walk model show excellent qualitative agreement
with experiments conducted on electroluminescent polyfluorene demonstrating
non-dispersive hole transport. The current exhibits a constant plateau as the
charge carriers move with a time-independent drift velocity, followed by a long
tail when they reach the collecting electrode. Variation of the parameters
within the model allows the investigation of the transition from non-dispersive
to dispersive transport in highly aligned polymers. It turns out that large
inter-chain hopping is required for non-dispersive hole transport and that
structural disorder obstructs the propagation of holes through the polymer
film.Comment: 4 pages, 5 figure
Night Sleep and Parental Bedtime Practices in Low-Risk Preterm and Full-Term Late Talkers
Night sleep and parental bedtime practices have rarely been investigated in late talkers. This study aimed to explore: night sleep, parental bedtime practices, and their associations in late talkers as well as individual, socio-demographic, and socio-relational factors affecting them. Parents of 47 30-month-old late talkers, born low-risk preterm (n = 24) or full-term (n = 23), with an expressive vocabulary size <= 10th percentile measured by the MacArthur-Bates Communicative Development Inventory Words and Sentences, and normal cognitive abilities measured by the Bayley Scales, completed the Infant Sleep Questionnaire, the Parental Interactive Bedtime Behaviour Scale, and the Parenting Stress Index Short Form. Results showed slight settling difficulties, night wakings, and frequent co-sleeping in late talkers. Encouraging autonomy practices were frequently used by parents, rather than active physical comforting ones. Recurrent settling difficulties were reported by parents who often applied encouraging autonomy practices, whereas greater night waking problems and frequent co-sleeping were reported by parents who often left their child crying. Low-risk preterm birth and mother's parenting stress predicted total sleep difficulties and night wakings; first-born, high maternal education level and mother's parenting stress predicted settling difficulties; mother's parenting stress was the only predictor for co-sleeping and leaving to cry. These findings have relevant implications for improving late talkers' night sleep and their parents' bedtime practices
Non-perturbative scale evolution of four-fermion operators
We apply the Schroedinger Functional (SF) formalism to determine the
renormalisation group running of four-fermion operators which appear in the
effective weak Hamiltonian of the Standard Model. Our calculations are done
using Wilson fermions and the parity-odd components of the operators.
Preliminary results are presented for the operator .Comment: Lattice2002(improve
Some Insights in Superdiffusive Transport
In this paper we deal with high-order corrections for the Fractional
Derivative approach to anomalous diffusion, in super-diffusive regime, which
become relevand whenever one attempts to describe the behavior of particles
close to normal diffusion.Comment: 14 pages, 7 figure
Adaptability and innovation in healthcare facilities. Lessons from the past for future developments
Fractional diffusion in periodic potentials
Fractional, anomalous diffusion in space-periodic potentials is investigated.
The analytical solution for the effective, fractional diffusion coefficient in
an arbitrary periodic potential is obtained in closed form in terms of two
quadratures. This theoretical result is corroborated by numerical simulations
for different shapes of the periodic potential. Normal and fractional spreading
processes are contrasted via their time evolution of the corresponding
probability densities in state space. While there are distinct differences
occurring at small evolution times, a re-scaling of time yields a mutual
matching between the long-time behaviors of normal and fractional diffusion
Temperature and Field Dependence of the Mobility in Liquid-Crystalline Conjugated Polymer Films
The transport properties of organic light-emitting diodes in which the
emissive layer is composed of conjugated polymers in the liquid-crystalline
phase have been investigated. We have performed simulations of the current
transient response to an illumination pulse via the Monte Carlo approach, and
from the transit times we have extracted the mobility of the charge carriers as
a function of both the electric field and the temperature. The transport
properties of such films are different from their disordered counterparts, with
charge carrier mobilities exhibiting only a weak dependence on both the
electric field and temperature. We show that for spatially ordered polymer
films, this weak dependence arises for thermal energy being comparable to the
energetic disorder, due to the combined effect of the electrostatic and thermal
energies. The inclusion of spatial disorder, on the other hand, does not alter
the qualitative behaviour of the mobility, but results in decreasing its
absolute value.Comment: 9 pages, 8 figures, submitted to Phys. Rev.
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