204 research outputs found
How Europeans move: a moderate-to-vigorous physical activity and sitting time paradox in the European Union
Objectives: This study aimed to assess the interactions between physical activity (PA) and sedentary behaviour in a large population taking account of major sociodemographic characteristics. Study design: Cross-sectional population-based study. Methods: Data from 28,031 individuals living in the European Union who were aged ≥15 years were retrieved from a cross-sectional survey, the Eurobarometer 2017. Interactions among the four mobility components (vigorous, moderate, walking activity and sitting time) were assessed at the individual level across age, gender and place of residence, and at the country level by compositional data analysis, hierarchical linear regressions and principal component analysis. Results: The most frequently reported PA was walking; however, sitting time represented >95% of the reported weekly times, whereas moderate-to-vigorous PA (MVPA) represented <1%. Women reported less PA and sitting time, age decreased total PA and increased sitting time, and individuals living in large urban areas reported lower PA and higher sitting times. MVPA decreased with age (β = -0.047, P < 0.001) and was lower in women (β = -0.760, P < 0.001) and those living in large urban areas (β = -0.581, P < 0.001), while walking and sitting times increased with age, being higher in women and lower in those living in rural areas. At the country level, sitting time was positively associated with moderate activity (β = 0.389, P = 0.041) and marginally non-significant with MVPA (β = 0.330, P = 0.087). Conclusions: Walking was the highest contributor to weekly PA, whereas sitting time was paradoxically associated with higher MVPA. Specific measures to reduce sitting time are required to achieve an active lifestyle
Beryllium abundances in stars hosting giant planets
We have derived beryllium abundances in a wide sample of stars hosting
planets, with spectral types in the range F7V-K0V, aimed at studying in detail
the effects of the presence of planets on the structure and evolution of the
associated stars. Predictions from current models are compared with the derived
abundances and suggestions are provided to explain the observed
inconsistencies. We show that while still not clear, the results suggest that
theoretical models may have to be revised for stars with Teff<5500K. On the
other hand, a comparison between planet host and non-planet host stars shows no
clear difference between both populations. Although preliminary, this result
favors a ``primordial'' origin for the metallicity ``excess'' observed for the
planetary host stars. Under this assumption, i.e. that there would be no
differences between stars with and without giant planets, the light element
depletion pattern of our sample of stars may also be used to further
investigate and constraint Li and Be depletion mechanisms.Comment: A&A in press -- accepted on the 22/02/2002 (11 pages, 6 figures
included
Efficient Effort Equilibrium in Cooperation with Pairwise Cost Reduction
There are multiple situations in which bilateral interaction between agents results in considerable cost reductions. Such interaction can occur in settings where agents are interested in sharing resources, knowledge or infrastructures. Their common purpose is to obtain individual advantages, e.g. by reducing their respective individual costs. Achieving this pairwise cooperation often requires the agents involved to make some level of effort. It is natural to think that the amount by which one agent could reduce the costs of the other may depend on how much effort the latter exerts. In the first stage, agents decide how much effort they are to exert, which has a direct impact on their pairwise cost reductions. We model this first stage as a non-cooperative game, in which agents determine the level of pairwise effort to reduce the cost of their partners. In the second stage, agents engage in a bilateral interaction between independent partners. We study this bilateral cooperation as a cooperative game in which agents reduce each other's costs as a result of cooperation, so that the total reduction in the cost of each agent in a coalition is the sum of the reductions generated by the rest of the members of that coalition. In the non-cooperative game that precedes cooperation with pairwise cost reduction, the agents anticipate the cost allocation that results from the cooperative game in the second stage by incorporating the effect of the effort exerted into their cost functions. Based on this model, we explore the costs, benefits, and challenges associated with setting up a pairwise effort network. We identify a family of cost allocations with weighted pairwise reduction which are always feasible in the cooperative game and contain the Shapley value. We show that there are always cost allocations with weighted pairwise reductions that generate an optimal level of efficient effort and provide a procedure for finding the efficient effort equilibrium
Discontinuous transitions in double exchange materials
It is shown that the double exchange Hamiltonian, with weak antiferromagnetic
interactions, has a rich variety of first order transitions between phases with
different electronic densities and/or magnetizations. For band fillings in the
range , and at finite temperatures, a discontinuous
transition between phases with similar electronic densities but different
magnetizations takes place. This sharp transition, which is not suppressed by
electrostatic effects, and survives in the presence of an applied field, is
consistent with the phenomenology of the doped manganites near the transition
temperature.Comment: three more variational ansatzs considere
Satisfacción de usuarios de servicios deportivos en Orihuela (Alicante)
The aim of this study was to evaluate the perceived quality and user satisfaction of the municipal sports facility "Water Palace" in Orihuela (Alicante). The sample was formed by 36 users of the facility. Questionnaire EPOD (Nuviala, Tamayo, Iranzo and Falcón, 2008) was administered to the sample in order to measure the users satisfaction. The most significant results show that users are satisfied with the sports facility, with the best results in the image of the organization, the activities and technical aspects. The lowest scores appear in sports facilities and material. Therefore, it is concluded that, as future implications in the management of the facility, it is advisable to focus the attention on the dimensions related to sports facilities and material because they obtained the lowest scores.El objetivo del presente estudio ha sido evaluar la calidad percibida y satisfacción de usuarios de la instalación deportiva municipal del "Palacio del Agua" en la localidad alicantina de Orihuela. La muestra estuvo formada por 36 usuarios de dicha instalación. Se aplicó el cuestionario EPOD (Escala de Percepción de Organizaciones Deportivas), de Nuviala, Tamayo, Iranzo y Falcón (2008), el cual mide la satisfacción de usuarios de organizaciones que prestan servicios deportivos. Los resultados más significativos muestran que los usuarios están satisfechos con la instalación deportiva, obteniendo los mejores resultados en los apartados de imagen de la organización, actividades y aspectos técnicos. Sin embargo, se denotan puntuaciones más bajas en el apartado de instalación y material. Por todo ello, se concluye que, como futuras implicaciones en la gestión de la instalación, se debería focalizar la atención en las dimensiones relacionadas con la instalación y el material, ya que obtienen las puntuaciones más bajas
Are beryllium abundances anomalous in stars with giant planets?
In this paper we present beryllium (Be) abundances in a large sample of 41
extra-solar planet host stars, and for 29 stars without any known
planetary-mass companion, spanning a large range of effective temperatures. The
Be abundances were derived through spectral synthesis done in standard Local
Thermodynamic Equilibrium, using spectra obtained with various instruments. The
results seem to confirm that overall, planet-host stars have ``normal'' Be
abundances, although a small, but not significant, difference might be present.
This result is discussed, and we show that this difference is probably not due
to any stellar ``pollution'' events. In other words, our results support the
idea that the high-metal content of planet-host stars has, overall, a
``primordial'' origin. However, we also find a small subset of planet-host
late-F and early-G dwarfs that might have higher than average Be abundances.
The reason for the offset is not clear, and might be related either to the
engulfment of planetary material, to galactic chemical evolution effects, or to
stellar-mass differences for stars of similar temperature.Comment: 15 pages, 9 figures, accepted for publication in Astronomy &
Astrophysic
The Eccentricity-Mass Distribution of Exoplanets: Signatures of Different Formation Mechanisms?
We examine the distributions of eccentricity and host star metallicity of
exoplanets as a function of their mass. Planets with M sin i >~ 4 M_J have an
eccentricity distribution consistent with that of binary stars, while planets
with M sin i <~ 4 M_J are less eccentric than binary stars and more massive
planets. In addition, host star metallicities decrease with planet mass. The
statistical significance of both of these trends is only marginal with the
present sample of exoplanets. To account for these trends, we hypothesize that
there are two populations of gaseous planets: the low-mass population forms by
gas accretion onto a rock-ice core in a circumstellar disk and is more abundant
at high metalliticities, and the high-mass population forms directly by
fragmentation of a pre-stellar cloud. Planets of the first population form in
initially circular orbits and grow their eccentricities later, and may have a
mass upper limit from the total mass of the disk that can be accreted by the
core. The second population may have a mass lower limit resulting from
opacity-limited fragmentation. This would roughly divide the two populations in
mass, although they would likely overlap over some mass range. If most objects
in the second population form before the pre-stellar cloud becomes highly
opaque, they would have to be initially located in orbits larger than ~30 AU,
and would need to migrate to the much smaller orbits in which they are
observed. The higher mean orbital eccentricity of the second population might
be caused by the larger required intervals of radial migration, and the brown
dwarf desert might be due to the inability of high-mass brown dwarfs to migrate
inwards sufficiently in radius.Comment: 7 pages, 4 figures. Version with expanded discussion section.
Accepted for publication in A&
Nitrogen abundances in Planet-harbouring stars
We present a detailed spectroscopic analysis of nitrogen abundances in 91
solar-type stars, 66 with and 25 without known planetary mass companions. All
comparison sample stars and 28 planet hosts were analysed by spectral synthesis
of the near-UV NH band at 3360 \AA observed at high resolution with the
VLT/UVES,while the near-IR NI 7468 \AA was measured in 31 objects. These two
abundance indicators are in good agreement. We found that nitrogen abundance
scales with that of iron in the metallicity range -0.6 <[Fe/H]< +0.4 with the
slope 1.08 \pm 0.05. Our results show that the bulk of nitrogen production at
high metallicities was coupled with iron. We found that the nitrogen abundance
distribution in stars with exoplanets is the high [Fe/H] extension of the curve
traced by the comparison sample of stars with no known planets. A comparison of
our nitrogen abundances with those available in the literature shows a good
agreement.Comment: 15 pages, 7 figures, Accepted for publication in A&
Light elements in stars with exoplanets
It is well known that stars orbited by giant planets have higher abundances
of heavy elements when compared with average field dwarfs. A number of studies
have also addressed the possibility that light element abundances are different
in these stars. In this paper we will review the present status of these
studies. The most significant trends will be discussed.Comment: 10 pages, 6 figures. Submitted to the proceedings of IAU symposium
268: Light elements in the universe
Phase diagram and influence of defects in the double perovskites
The phase diagram of the double perovskites of the type Sr_{2-x} La_x Fe Mo
O_6 is analyzed, with and without disorder due to antisites. In addition to an
homogeneous half metallic ferrimagnetic phase in the absence of doping and
disorder, we find antiferromagnetic phases at large dopings, and other
ferrimagnetic phases with lower saturation magnetization, in the presence of
disorder.Comment: 4 pages, 3 postscript figures, some errata correcte
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