9,977 research outputs found
Cosmic-ray propagation properties for an origin in SNRs
We have studied the impact of cosmic-ray acceleration in SNR on the spectra
of cosmic-ray nuclei in the Galaxy using a series expansion of the propagation
equation, which allows us to use analytical solutions for part of the problem
and an efficient numerical treatment of the remaining equations and thus
accurately describes the cosmic-ray propagation on small scales around their
sources in three spatial dimensions and time. We found strong variations of the
cosmic-ray nuclei flux by typically 20% with occasional spikes of much higher
amplitude, but only minor changes in the spectral distribution. The locally
measured spectra of primary cosmic rays fit well into the obtained range of
possible spectra. We further showed that the spectra of the secondary element
Boron show almost no variations, so that the above findings also imply
significant fluctuations of the Boron-to-Carbon ratio. Therefore the commonly
used method of determining CR propagation parameters by fitting
secondary-to-primary ratios appears flawed on account of the variations that
these ratios would show throughout the Galaxy.Comment: Accepted for publication in Ap
Evidence for directed percolation universality at the onset of spatiotemporal intermittency in coupled circle maps
We consider a lattice of coupled circle maps, a model arising naturally in
descriptions of solid state phenomena such as Josephson junction arrays. We
find that the onset of spatiotemporal intermittency (STI) in this system is
analogous to directed percolation (DP), with the transition being to an unique
absorbing state for low nonlinearities, and to weakly chaotic absorbing states
for high nonlinearities. We find that the complete set of static exponents and
spreading exponents at all critical points match those of DP very convincingly.
Further, hyperscaling relations are fulfilled, leading to independent controls
and consistency checks of the values of all the critical exponents. These
results lend strong support to the conjecture that the onset of STI in
deterministic models belongs to the DP universality class.Comment: Submitted to Physical Review
Health economics: identifying leading producers, countries relative specialization and themes
El área de investigación en economía de la salud tuvo una gran evolución a partir de la década de 1960 y está en constante crecimiento. Actualmente, el gasto en salud es un tema clave en todo el mundo. La bibliometría proporciona varios métodos para explorar el impacto y la evolución de la investigación. Así pues, el principal objetivo del presente estudio es comprender la situación actual de la investigación en materia de economía de la salud para el período 2010-2019. Se analizaron tres aspectos diferentes: la producción de los países, el índice de prioridad relativa y los temas principales. El conjunto de datos se obtuvo a partir de los documentos indizados en la base de datos Web of Science de 2010 a 2019. Se utilizó el software SciMAT para obtener el análisis temático mediante el análisis de mapas de la ciencia. Las revistas Health economics, Value in Health, Journal of Health Economics y European Journal of Health Economics son los principales productoras. Estados Unidos, Inglaterra y Alemania son los que tienen una mayor producción; los Países Bajos, Inglaterra y Australia son los que tienen el índice de prioridad relativa más alto. Los años de vida ajustados en función de la calidad y la desigualdad en materia de salud son los temas con mayor número de documentos y medidas de impacto. Este estudio es un marco útil basado en ciencia que servirá de base para futuras acciones de investigación.Health economics research area was a high evolution from the 1960s and it is constantly growing. Currently, the health expenditure is a key issue worldwide. Bibliometrics provides several methods to explore the impact and evolution of the research. Thus, the main aim of the present study is to understand the current status of the research in health economics for the period 2010-2019. Three different aspects were analyzed: countries production, relative priority index and main themes. The dataset was obtained from the documents indexed in the Web of Science database from 2010 to 2019. SciMAT software was used to obtain the thematic analysis by means of science mapping analysis. The journals Health economics, Value in Health, Journal of Health Economics, and European Journal of Health Economics are the main producers. USA, England and Germany are those with highest production; Netherlands, England and Australia are those with the highest relative priority index. Quality adjusted life years and Health inequality are the themes with the highest number of documents and impact measures. This study is a useful evidence-based framework on which to base future research actions
The "K-Correction" for Irradiated Emission Lines in LMXBs: Evidence for a Massive Neutron Star in X1822-371 (V691 CrA)
We study the K-correction for the case of emission lines formed in the X-ray
illuminated atmosphere of a Roche lobe filling star. We compute the
K-correction as function of the mass ratio 'q' and the disc flaring angle
'alpha' using a compact binary code where the companion's Roche lobe is divided
into 10^5 resolution elements. We also study the effect of the inclination
angle in the results. We apply our model to the case of the neutron star
low-mass X-ray binary X1822-371 (V691 CrA), where a K-emission velocity
K_em=300 +-8 km/s has been measured by Casares et al. (2003). Our numerical
results, combined with previous determination of system parameters, yields
1.61Msun < M_NS < 2.32Msun and 0.44Msun < M_2 < 0.56Msun for the two binary
components(i. e. 0.24 < q < 0.27), which provide a compelling evidence for a
massive neutron star in this system. We also discuss the implications of these
masses into the evolutionary history of the binary.Comment: 6 pages, 5 figures. Accepted for publication in Ap
Measured and perceived physical responses in multidimensional fitness training through exergames in older adults
Exergames have been used to increase physical
activity levels to produce health benefits in older adults.
However, only a small number of studies have quantified the
physical activity levels produced by custom-made Exergames and
their capacity to elicit recommended levels of exercise. This study
investigates the effectiveness of custom-made Exergames,
designed for multidimensional fitness training, in eliciting
recommended levels of exercise. We rely on both objective
(accelerometry) and subjective (perceived exertion) information
collected in two different modalities of exercise, consisting of 40-
minutes sessions: Exergaming and conventional training
(Control). A between-subjects analysis was done involving two
groups of active older adults (n=33). Participants in the Control Between condition performed physical activity in conventional
group fitness training, while the intervention group used
individualized Exergaming as training modality. In addition, a
sub-group of the Exergaming participants also performed a
conventional training session (Control-Within), which enabled a
within-subjects comparison. Results show that participants spent
significantly more time in moderate-to-vigorous intensities
during Exergaming, interestingly, perceiving significantly lower
exertion levels. The between-subjects analysis only presented
statistically significant differences for the perceived exertion
scale. This study helps to unveil the impact of custom-made
Exergames in physical activity levels during training when
compared to conventional training for the older adult population.info:eu-repo/semantics/publishedVersio
Phase transition of a two dimensional binary spreading model
We investigated the phase transition behavior of a binary spreading process
in two dimensions for different particle diffusion strengths (). We found
that cluster mean-field approximations must be considered to get
consistent singular behavior. The approximations result in a continuous
phase transition belonging to a single universality class along the phase transition line. Large scale simulations of the particle density
confirmed mean-field scaling behavior with logarithmic corrections. This is
interpreted as numerical evidence supporting that the upper critical dimension
in this model is .The pair density scales in a similar way but with an
additional logarithmic factor to the order parameter. At the D=0 endpoint of
the transition line we found DP criticality.Comment: 8 pages, 10 figure
PACS photometry of the Herschel Reference Survey - Far-infrared/sub-millimeter colours as tracers of dust properties in nearby galaxies
We present Herschel/PACS 100 and 160 micron integrated photometry for the 323
galaxies in the Herschel Reference Survey (HRS), a K-band-, volume-limited
sample of galaxies in the local Universe. Once combined with the Herschel/SPIRE
observations already available, these data make the HRS the largest
representative sample of nearby galaxies with homogeneous coverage across the
100-500 micron wavelength range. In this paper, we take advantage of this
unique dataset to investigate the properties and shape of the
far-infrared/sub-millimeter spectral energy distribution in nearby galaxies. We
show that, in the stellar mass range covered by the HRS (8<log(M*/Msun)<12),
the far-infrared/sub-millimeter colours are inconsistent with a single modified
black-body having the same dust emissivity index beta for all galaxies. In
particular, either beta decreases, or multiple temperature components are
needed, when moving from metal-rich/gas-poor to metal-poor/gas-rich galaxies.
We thus investigate how the dust temperature and mass obtained from a single
modified black-body depend on the assumptions made on beta. We show that, while
the correlations between dust temperature, galaxy structure and star formation
rate are strongly model dependent, the dust mass scaling relations are much
more reliable, and variations of beta only change the strength of the observed
trends.Comment: 26 pages, 8 figures, 2 tables. Accepted for publication in MNRA
The extinction law in high redshift galaxies
We estimate the dust extinction laws in two intermediate redshift galaxies.
The dust in the lens galaxy of LBQS1009-0252, which has an estimated lens
redshift of zl~0.88, appears to be similar to that of the SMC with no
significant feature at 2175 A. Only if the lens galaxy is at a redshift of
zl~0.3, completely inconsistent with the galaxy colors, luminosity or location
on the fundamental plane, can the data be fit with a normal Galactic extinction
curve. The dust in the zl=0.68 lens galaxy for B0218+357, whose reddened image
lies behind a molecular cloud, requires a very flat ultraviolet extinction
curve with (formally) R(V)=12 +- 2. Both lens systems seem to have unusual
extinction curves by Galactic standards.Comment: 15 pages, 3 figures. ApJ in pres
Natural based products for cleaning copper and copper alloys artefacts
Copper alloys objects can deteriorate their conservation state through irreversible corrosion. Since in the cultural heritage field every artefact is unique and any loss irreplaceable, solutions for conservation are needed. Hence, there is the necessity to stop the corrosion process with a suitable cleaning and conservation process to avoid further degradation processes without changing its morphological aspect. Chelating solutions are commonly used in chemical cleaning, mainly sodium salts of ethylenediaminetetraacetic acid (EDTA). However, it is resistant to water purification procedures and is not biodegradable. The goal of this study was to see if applying an ecologically friendly chelating agent as an alternative to EDTA cleaning procedures for cultural heritage was suitable. In this study were chosen six natural-based chelators that could be a new green non-toxic alternative to EDTA in corrosion-inhibiting properties. They were tested for cleaning copper artefacts exposed to atmospheric environment in polluted areas. The study considered four amino acids, a glucoheptonate (CSA) and an industrial green chelator (GLDA). The effectiveness was tested on corrosion copper compounds and on laboratory corroded copper sheets. Finally, the cleaning efficacy was tested on four Roman coins and a modern copper painting. To define the cleaning efficacy, surface analytical investigations have been carried out by means ICP-OES, UV-VIS, µ-Raman, spectro-colorimetry, XRD and FTIR. Among the amino acids, alanine was the most effective, showing an unaltered noble patina and a good effective copper recovery from corrosion patinas
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