1,399 research outputs found
Decay of weak solutions to the 2D dissipative quasi-geostrophic equation
We address the decay of the norm of weak solutions to the 2D dissipative
quasi-geostrophic equation. When the initial data is in only, we prove
that the norm tends to zero but with no uniform rate, that is, there are
solutions with arbitrarily slow decay. For the initial data in ,
with , we are able to obtain a uniform decay rate in . We
also prove that when the norm of the initial data
is small enough, the norms, for have uniform
decay rates. This result allows us to prove decay for the norms, for , when the initial data is in .Comment: A paragraph describing work by Carrillo and Ferreira proving results
directly related to the ones in this paper is added in the Introduction. Rest
of the article remains unchange
Association between Nutritional Status and Positive Childhood Disability Screening Using the Ten Questions Plus Tool in Sarlahi, Nepal
The study was conducted to examine the association between the indicators of malnutrition and disability of children as reported by caregivers. The Ten Questions Plus questionnaire was administered to caregivers of 1,902 children aged 1–9 years, during August 2007–March 2008, in rural Nepal. Height and weight of children were also measured. The main outcome was a positive response to one or more questions. In total, 514 (27%) children had a positive response to at least one question. Moderate stunting [odds ratio (OR)=1.47, 95% confidence interval (CI) 1.02–2.12) and severe (OR=2.39, 95% CI 1.60–3.57) stunting were independently associated with reported delay in sitting, standing, or walking. Severe stunting was also associated with report of delayed learning compared to other children of similar age (OR=2.01, 95% CI 1.27–3.20). Parental report of disability was quite prevalent in this setting, with over a quarter of the sample screening positive. Chronic malnutrition may be associated with delayed motor and mental development
An Improved Description of the Dielectric Breakdown in Oxides Based on a Generalized Weibull distribution
In this work, we address modal parameter fluctuations in statistical
distributions describing charge-to-breakdown and/or
time-to-breakdown during the dielectric breakdown regime of
ultra-thin oxides, which are of high interest for the advancement of electronic
technology. We reobtain a generalized Weibull distribution (-Weibull), which
properly describes data when oxide thickness fluctuations are
present, in order to improve reliability assessment of ultra-thin oxides by
time-to-breakdown extrapolation and area scaling. The incorporation
of fluctuations allows a physical interpretation of the -Weibull
distribution in connection with the Tsallis statistics. In support to our
results, we analyze data of SiO-based MOS devices obtained
experimentally and theoretically through a percolation model, demonstrating an
advantageous description of the dielectric breakdown by the -Weibull
distribution.Comment: 5 pages, 3 figure
Ground state of a polydisperse electrorheological solid: Beyond the dipole approximation
The ground state of an electrorheological (ER) fluid has been studied based
on our recently proposed dipole-induced dipole (DID) model. We obtained an
analytic expression of the interaction between chains of particles which are of
the same or different dielectric constants. The effects of dielectric constants
on the structure formation in monodisperse and polydisperse electrorheological
fluids are studied in a wide range of dielectric contrasts between the
particles and the base fluid. Our results showed that the established
body-centered tetragonal ground state in monodisperse ER fluids may become
unstable due to a polydispersity in the particle dielectric constants. While
our results agree with that of the fully multipole theory, the DID model is
much simpler, which offers a basis for computer simulations in polydisperse ER
fluids.Comment: Accepted for publications by Phys. Rev.
Modelling the Interfacial Flow of Two Immiscible Liquids in Mixing Processes
This paper presents an interface tracking method for modelling the flow of immiscible metallic liquids in mixing processes. The methodology can provide an insight into mixing processes for studying the fundamental morphology development mechanisms for immiscible interfaces. The volume-of-fluid (VOF) method is adopted in the present study, following a review of various modelling approaches for immiscible fluid systems. The VOF method employed here utilises the piecewise linear for interface construction scheme as well as the continuum surface force algorithm for surface force modelling. A model coupling numerical and experimental data is established. The main flow features in the mixing process are investigated. It is observed that the mixing of immiscible metallic liquids is strongly influenced by the viscosity of the system, shear forces and turbulence. The numerical results show good qualitative agreement with experimental results, and are useful for optimisating the design of mixing casting processes
Entanglement and Quantum Phase Transitions via Adiabatic Quantum Computation
For a finite XY chain and a finite two-dimensional Ising lattice, it is shown
that the paramagnetic ground state is adiabatically transformed to the GHZ
state in the ferromagnetic phase by slowly turning on the magnetic field. The
fidelity between the GHZ state and an adiabatically evolved state shows a
feature of the quantum phase transition.Comment: Revise
Quasi-Periodic Releases of Streamer Blobs and Velocity Variability of the Slow Solar Wind near the Sun
We search for persistent and quasi-periodic release events of streamer blobs
during 2007 with the Large Angle Spectrometric Coronagraph on the \textit{Solar
and Heliospheric Observatory} and assess the velocity of the slow solar wind
along the plasma sheet above the corresponding streamer by measuring the
dynamic parameters of blobs. We find 10 quasi-periodic release events of
streamer blobs lasting for three to four days. In each day of these events, we
observe three-five blobs. The results are in line with previous studies using
data observed near the last solar minimum. Using the measured blob velocity as
a proxy for that of the mean flow, we suggest that the velocity of the
background slow solar wind near the Sun can vary significantly within a few
hours. This provides an observational manifestation of the large velocity
variability of the slow solar wind near the Sun.Comment: 14 pages, 5 figures, accepted by Soalr Physic
Long-range quantum discord in critical spin systems
We show that quantum correlations as quantified by quantum discord can
characterize quantum phase transitions by exhibiting nontrivial long-range
decay as a function of distance in spin systems. This is rather different from
the behavior of pairwise entanglement, which is typically short-ranged even in
critical systems. In particular, we find a clear change in the decay rate of
quantum discord as the system crosses a quantum critical point. We illustrate
this phenomenon for first-order, second-order, and infinite-order quantum phase
transitions, indicating that pairwise quantum discord is an appealing quantum
correlation function for condensed matter systems
Three efficient numerical models to analyse the step problem in shallow water
In this paper, the problem of acoustic wave propagation in a waveguide of infinite extent is modelled, taking into account constant depth in each section of the sea. Efficient numerical strategies in the frequency domain are addressed to investigate two-dimensional acoustic wave propagation in a shallow water configuration, considering a step in the rigid bottom and a flat free surface. The time domain responses are obtained by means of an inverse Fast Fourier Transform (FFT) of results computed in the frequency domain. The numerical approaches used here are based on the Boundary Element Method (BEM) and the Method of Fundamental Solutions (MFS). In the numerical models only the inclined or vertical interface between the sub-regions of different depth are discretized, as Green׳s functions that take into account the presence of free and rigid surfaces are used. These Green׳s functions are obtained either by eigenfunction expansion or by Ewald׳s method. A detailed discussion on the performance of these formulations is carried out, with the aim of finding an efficient numerical formulation to solve the step problem in shallow water
LRRK2 A419V is not associated with Parkinson's disease in different Chinese populations
10.1371/journal.pone.0036123PLoS ONE77
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