260 research outputs found
Features of the Extension of a Statistical Measure of Complexity to Continuous Systems
We discuss some aspects of the extension to continuous systems of a
statistical measure of complexity introduced by Lopez-Ruiz, Mancini and Calbet
(LMC) [Phys. Lett. A 209 (1995) 321]. In general, the extension of a magnitude
from the discrete to the continuous case is not a trivial process and requires
some choice. In the present study, several possibilities appear available. One
of them is examined in detail. Some interesting properties desirable for any
magnitude of complexity are discovered on this particular extension.Comment: 22 pages, 0 figure
Electronic damage in quartz (c-SiO2) by MeV ion irradiations: Potentiality for optical waveguiding applications
The damage induced on quartz (c-SiO2) by heavy ions (F, O, Br) at MeV energies, where electronic stopping is dominant, has been investigated by RBS/C and optical methods. The two techniques indicate the formation of amorphous layers with an isotropic refractive index (n = 1.475) at fluences around 1014 cm−2 that are associated to electronic mechanisms. The kinetics of the process can be described as the superposition of linear (possibly initial Poisson curve) and sigmoidal (Avrami-type) contributions. The coexistence of the two kinetic regimes may be associated to the differential roles of the amorphous track cores and preamorphous halos. By using ions and energies whose maximum stopping power lies inside the crystal (O at 13 MeV, F at 15 MeV and F at 30 MeV) buried amorphous layer are formed and optical waveguides at the sample surface have been generated
Evidence of Impulsive Heating in Active Region Core Loops
Using a full spectral scan of an active region from the Extreme-Ultraviolet
Imaging Spectrometer (EIS) we have obtained Emission Measure EM
distributions in two different moss regions within the same active region. We
have compared these with theoretical transition region EMs derived for three
limiting cases, namely \textit{static equilibrium}, \textit{strong
condensation} and \textit{strong evaporation} from \cite{ebtel}. The EM
distributions in both the moss regions are strikingly similar and show a
monotonically increasing trend from . Using
photospheric abundances we obtain a consistent EM distribution for all ions.
Comparing the observed and theoretical EM distributions, we find that the
observed EM distribution is best explained by the \textit{strong condensation}
case (EM), suggesting that a downward enthalpy flux plays an important
and possibly dominant role in powering the transition region moss emission. The
downflows could be due to unresolved coronal plasma that is cooling and
draining after having been impulsively heated. This supports the idea that the
hot loops (with temperatures of 3{-}5 MK) seen in the core of active regions
are heated by nanoflares.Comment: 17 pages, 4 figures, Accepted for publication in The Astrophysical
Journa
QED self-energy contribution to highly-excited atomic states
We present numerical values for the self-energy shifts predicted by QED
(Quantum Electrodynamics) for hydrogenlike ions (nuclear charge ) with an electron in an , 4 or 5 level with high angular momentum
(). Applications include predictions of precision transition
energies and studies of the outer-shell structure of atoms and ions.Comment: 20 pages, 5 figure
Causality and the Entropy-Complexity Plane: Robustness and Missing Ordinal Patterns
We deal here with the issue of determinism versus randomness in time series.
One wishes to identify their relative weights in a given time series. Two
different tools have been advanced in the literature to such effect, namely, i)
the "causal" entropy-complexity plane [Rosso et al. Phys. Rev. Lett. 99 (2007)
154102] and ii) the estimation of the decay rate of missing ordinal patterns
[Amig\'o et al. Europhys. Lett. 79 (2007) 50001, and Carpi et al. Physica A 389
(2010) 2020-2029]. In this work we extend the use of these techniques to
address the analysis of deterministic finite time series contaminated with
additive noises of different degree of correlation. The chaotic series studied
here was via the logistic map (r = 4) to which we added correlated noise
(colored noise with f-k Power Spectrum, 0 {\leq} k {\leq} 2) of varying
amplitudes. In such a fashion important insights pertaining to the
deterministic component of the original time series can be gained. We find that
in the entropy-complexity plane this goal can be achieved without additional
computations.Comment: submitted to Physica
On Solving the Coronal Heating Problem
This article assesses the current state of understanding of coronal heating,
outlines the key elements of a comprehensive strategy for solving the problem,
and warns of obstacles that must be overcome along the way.Comment: Accepted by Solar Physics; Published by Solar Physic
Quantum walks: a comprehensive review
Quantum walks, the quantum mechanical counterpart of classical random walks,
is an advanced tool for building quantum algorithms that has been recently
shown to constitute a universal model of quantum computation. Quantum walks is
now a solid field of research of quantum computation full of exciting open
problems for physicists, computer scientists, mathematicians and engineers.
In this paper we review theoretical advances on the foundations of both
discrete- and continuous-time quantum walks, together with the role that
randomness plays in quantum walks, the connections between the mathematical
models of coined discrete quantum walks and continuous quantum walks, the
quantumness of quantum walks, a summary of papers published on discrete quantum
walks and entanglement as well as a succinct review of experimental proposals
and realizations of discrete-time quantum walks. Furthermore, we have reviewed
several algorithms based on both discrete- and continuous-time quantum walks as
well as a most important result: the computational universality of both
continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing
Journa
Peabody Picture Vocabulary Test-III: Normative data for Spanish-speaking pediatric population
OBJECTIVE: To generate normative data for the Peabody Picture Vocabulary Test-III (PPVT-III) in Spanish-speaking
pediatric populations.
METHOD: The sample consisted of 4,373 healthy children from nine countries in Latin America (Chile, Cuba, Ecuador,
Honduras, Guatemala, Mexico, Paraguay, Peru, and Puerto Rico) and Spain. Each participant was administered the PPVT-III
as part of a larger neuropsychological battery. PPVT-III scores were normed using multiple linear regressions and standard
deviations of residual values. Age, age2, sex, and mean level of parental education (MLPE) were included as predictors in
the analyses.
RESULTS: The final multiple linear regression models showed main effects for age in all countries, such that scores increased
linearly as a function of age. In addition, age2 had a significant effect in all countries, except Guatemala and Paraguay. Models
showed that children whose parent(s) had a MLPE >12 years obtained higher scores compared to children whose parent(s)
had a MLPE ≤12 years in all countries, except for Cuba, Peru, and Puerto Rico. Sex affected scores for Chile, Ecuador,
Guatemala, Mexico, and Spain.
CONCLUSIONS: This is the largest Spanish-speaking pediatric normative study in the world, and it will allow neuropsychologists from these countries to have a more accurate interpretation of the PPVT-III when used in pediatric populations
The Role of Type II Spicules in the Upper Solar Atmosphere
We examine the suggestion that most of the hot plasma in the Sun's corona
comes from type II spicule material that is heated as it is ejected from the
chromosphere. This contrasts with the traditional view that the corona is
filled via chromospheric evaporation that results from coronal heating. We
explore the observational consequences of a hypothetical spicule dominated
corona and conclude from the large discrepancy between predicted and actual
observations that only a small fraction of the hot plasma can be supplied by
spicules (<2% in active regions, <5% in the quiet Sun, and <8% in coronal
holes). The red-blue asymmetries of EUV spectral lines and the ratio of lower
transition region (LTR; T<0.1 MK) to coronal emission measures are both
predicted to be 2 orders of magnitude larger than observed. Furthermore, hot
spicule material would cool dramatically by adiabatic expansion as it rises
into the corona, so substantial coronal heating would be needed to maintain the
high temperatures that are seen at all altitudes. We suggest that the corona
contains a mixture of thin strands, some of which are populated by spicule
injections, but most of which are not. A majority of the observed hot emission
originates in non-spicule strands and is explained by traditional coronal
heating models. However, since these models predict far too little emission
from the LTR, most of this emission comes from the bulk of the spicule material
that is only weakly heated and visible in He II (304 A) as it falls back to the
surface.Comment: 11 pages, 5 figures, publishe
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