15,875 research outputs found
Simultaneous computation of dynamical and equilibrium information using a weighted ensemble of trajectories
Equilibrium formally can be represented as an ensemble of uncoupled systems
undergoing unbiased dynamics in which detailed balance is maintained. Many
non-equilibrium processes can be described by suitable subsets of the
equilibrium ensemble. Here, we employ the "weighted ensemble" (WE) simulation
protocol [Huber and Kim, Biophys. J., 1996] to generate equilibrium trajectory
ensembles and extract non-equilibrium subsets for computing kinetic quantities.
States do not need to be chosen in advance. The procedure formally allows
estimation of kinetic rates between arbitrary states chosen after the
simulation, along with their equilibrium populations. We also describe a
related history-dependent matrix procedure for estimating equilibrium and
non-equilibrium observables when phase space has been divided into arbitrary
non-Markovian regions, whether in WE or ordinary simulation. In this
proof-of-principle study, these methods are successfully applied and validated
on two molecular systems: explicitly solvated methane association and the
implicitly solvated Ala4 peptide. We comment on challenges remaining in WE
calculations
El género Holomitrium (Dicranaceae, Bryophyta), nuevo registro en Argentina y Uruguay
The genus Holomitrium Brid. is recorded for first time from Argentina and Uruguay. Only one species, H. arboreum, is present in the study area. A brief description, photographs and illustrations of the species are provided.El género Holomitrium (Dicranaceae, Bryophyta), nuevo registro en Argentina y Uruguay. El género Holomitrium Brid. es registrado por primera vez en Argentina y Uruguay. Sólo una especie, H. arboreum, está presente en el área de estudio. Se realiza una breve descripción y se proporcionan fotografías e ilustraciones de la especie.Fil: Suarez, Guillermo Martin. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Schiavone, Maria M.. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; ArgentinaFil: Colotti, Maria T.. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentin
Polytrichadelphus bolivianus una nueva especie de Polytrichaceae para el Noroeste de Argentina
Polytrichadelphus bolivianus Herzog, un musgo de los Bosques Montanos de Bolivia es registrado por primera vez para Argentina. Ha sido recolectado en 1997 y 1998 por Schiavone y otros en el norte de la provincia de Salta, pero hasta el momento no había sido identificado. Se presenta una descripción, ilustración y lectotipificación de la especie.Fil: Colotti, Maria T.. Fundación Miguel Lillo; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; ArgentinaFil: Suarez, Guillermo Martin. Fundación Miguel Lillo; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán; ArgentinaFil: Schiavone, María M.. Fundación Miguel Lillo; Argentina. Universidad Nacional de Tucuman. Facultad de Cs.naturales E Instituto Miguel Lillo. Instituto Miguel Lillo; Argentin
Quantum correlations versus Multisimultaneity: an experimental test
Multisimultaneity is a causal model of relativistic quantum physics which
assigns a real time ordering to any set of events, much in the spirit of the
pilot-wave picture. Contrary to standard quantum mechanics, it predicts a
disappearance of the correlations in a Bell-type experiment when both analysers
are in relative motion such that, each one in its own inertial reference frame,
is first to select the output of the photons. We tested this prediction using
acousto-optic modulators as moving beam-splitters and interferometers separated
by 55 m. We didn't observe any disappearance of the correlations, thus refuting
Multisimultaneity.Comment: 4 pages, 3 figures, RevTex 4 versio
Resilience and well-being among children of migrant parents in South-East Asia
There has been little systematic empirical research on the well-being of children in transnational households in South-East Asia—a major sending region for contract migrants. This study uses survey data collected in 2008 from children aged 9, 10 and 11 and their caregivers in Indonesia, the Philippines, and Vietnam (N=1,498). Results indicate that while children of migrant parents, especially migrant mothers, are less likely to be happy compared to children in non-migrant households, greater resilience in child well-being is associated with longer durations of maternal absence. There is no evidence for a direct parental migration effect on school enjoyment and performance. The analyses highlight the sensitivity of results to the dimension of child well-being measured and who makes the assessment.Publisher PDFPeer reviewe
Quantum Mechanics at Planck's scale and Density Matrix
In this paper Quantum Mechanics with Fundamental Length is chosen as Quantum
Mechanics at Planck's scale. This is possible due to the presence in the theory
of General Uncertainty Relations. Here Quantum Mechanics with Fundamental
Length is obtained as a deformation of Quantum Mechanics. The distinguishing
feature of the proposed approach in comparison with previous ones, lies on the
fact that here density matrix subjects to deformation whereas so far
commutators have been deformed. The density matrix obtained by deformation of
quantum-mechanical density one is named throughout this paper density
pro-matrix. Within our approach two main features of Quantum Mechanics are
conserved: the probabilistic interpretation of the theory and the well-known
measuring procedure corresponding to that interpretation. The proposed approach
allows to describe dynamics. In particular, the explicit form of deformed
Liouville's equation and the deformed Shr\"odinger's picture are given. Some
implications of obtained results are discussed. In particular, the problem of
singularity, the hypothesis of cosmic censorship, a possible improvement of the
definition of statistical entropy and the problem of information loss in black
holes are considered. It is shown that obtained results allow to deduce in a
simple and natural way the Bekenstein-Hawking's formula for black hole entropy
in semiclassical approximation.Comment: 18 pages,Latex,new reference
Propulsion in a viscoelastic fluid
Flagella beating in complex fluids are significantly influenced by
viscoelastic stresses. Relevant examples include the ciliary transport of
respiratory airway mucus and the motion of spermatozoa in the mucus-filled
female reproductive tract. We consider the simplest model of such propulsion
and transport in a complex fluid, a waving sheet of small amplitude free to
move in a polymeric fluid with a single relaxation time. We show that, compared
to self-propulsion in a Newtonian fluid occurring at a velocity U_N, the sheet
swims (or transports fluid) with velocity U / U_N = [1+De^2 (eta_s)/(eta)
]/[1+De^2], where eta_s is the viscosity of the Newtonian solvent, eta is the
zero-shear-rate viscosity of the polymeric fluid, and De is the Deborah number
for the wave motion, product of the wave frequency by the fluid relaxation
time. Similar expressions are derived for the rate of work of the sheet and the
mechanical efficiency of the motion. These results are shown to be independent
of the particular nonlinear constitutive equations chosen for the fluid, and
are valid for both waves of tangential and normal motion. The generalization to
more than one relaxation time is also provided. In stark contrast with the
Newtonian case, these calculations suggest that transport and locomotion in a
non-Newtonian fluid can be conveniently tuned without having to modify the
waving gait of the sheet but instead by passively modulating the material
properties of the liquid.Comment: 21 pages, 1 figur
Strategy for the inversion of Hinode spectropolarimetric measurements in the quiet Sun
In this paper we propose an inversion strategy for the analysis of
spectropolarimetric measurements taken by {\em Hinode} in the quiet Sun. The
spectropolarimeter of the Solar Optical Telescope aboard {\em Hinode} records
the Stokes spectra of the \ion{Fe}{i} line pair at 630.2 nm with unprecendented
angular resolution, high spectral resolution, and high sensitivity. We discuss
the need to consider a {\em local} stray-light contamination to account for the
effects of telescope diffraction. The strategy is applied to observations of a
wide quiet Sun area at disk center. Using these data we examine the influence
of noise and initial guess models in the inversion results. Our analysis yields
the distributions of magnetic field strengths and stray-light factors. They
show that quiet Sun internetwork regions consist mainly of hG fields with
stray-light contaminations of about 0.8.Comment: To appear in Publications of the Astronomical Society of Japan, 8
pages, 10 figure
Testing for heteroskedasticity of the residuals in fuzzy rule-based models
International audienceIn this paper, we propose a new diagnostic checking tool for fuzzy rule-based modelling of time series. Through the study of the residuals in the Lagrange Multiplier testing framework we devise a hypothesis test which allows us to determine if the residual time series is homoscedastic or not, that is, if it has the same variance throughout time. This is another important step towards a statistically sound modelling strategy for fuzzy rule-based models
- …