9,336 research outputs found
The radial pulsation of AI Aurigae
We present an analysis of eleven years of Stromgren by photometry of the red
semiregular variable star AI Aurigae. An early period determination of 63.9
days is confirmed by the long-term light curve behaviour. The light curve shows
semi-regular changes with a mean period of 65 days reaching an amplitude of 0.6
mag in some cycles. The b-y colour changes perfectly parallel the V light
curve, suggesting radial oscillation to be the main reason for the observed
variations. We estimate the main characteristics of the star (mass, radius,
effective temperature) that suggest radial pulsation in fundamental or first
overtone mode.Comment: 7 pages, 3 figures, accepted for publication in A&
Using the MitoB method to assess levels of reactive oxygen species in ecological studies of oxidative stress
In recent years evolutionary ecologists have become increasingly interested in the effects of reactive
oxygen species (ROS) on the life-histories of animals. ROS levels have mostly been inferred indirectly
due to the limitations of estimating ROS from in vitro methods. However, measuring ROS (hydrogen
peroxide, H2O2) content in vivo is now possible using the MitoB probe. Here, we extend and refine
the MitoB method to make it suitable for ecological studies of oxidative stress using the brown trout
Salmo trutta as model. The MitoB method allows an evaluation of H2O2 levels in living organisms over
a timescale from hours to days. The method is flexible with regard to the duration of exposure and
initial concentration of the MitoB probe, and there is no transfer of the MitoB probe between fish. H2O2
levels were consistent across subsamples of the same liver but differed between muscle subsamples
and between tissues of the same animal. The MitoB method provides a convenient method for
measuring ROS levels in living animals over a significant period of time. Given its wide range of possible
applications, it opens the opportunity to study the role of ROS in mediating life history trade-offs in
ecological settings
Spectroscopic binaries among Hipparcos M giants II. Binary frequency
This paper is the second one in a series devoted to the study of properties
of binaries involving M giants. The binary frequency of field M giants is
derived and compared with the binary fraction of K giants. Diagrams of the
CORAVEL spectroscopic parameter Sb (measuring the average line-width) vs.
radial-velocity standard deviation for our samples are used to define
appropriate binarity criteria. These then serve to extract the binarity
fraction among the M giants. Comparison is made to earlier data on K giants
binarity frequency. The Sb parameter is discussed in relation to global stellar
parameters and the Sb vs. stellar radius relation is used to identify fast
rotators. We find that the spectroscopic binary detection rate among field M
giants, in a sample with a low number of velocity measurements (~2), unbiased
toward earlier known binaries, is 6.3%. This is less than half of the analogous
rate for field K giants, likely resulting from a real difference. This
difference originates in the greater difficulty of finding binaries among M
giants because of their smaller orbital velocity amplitudes and larger
intrinsic jitter and in the different distributions of K and M giants in the
eccentricity-period diagram. A larger detection rate was obtained in a smaller
M giant sample with more radial velocity measurements per object: 11.1%
confirmed plus 2.7% possible binaries. The CORAVEL spectroscopic parameter Sb
was found to correlate better with the stellar radius than with either
luminosity or effective temperature separately. Two outliers of the Sb vs.
stellar radius relation, HD 190658 and HD 219654, have been recognized as fast
rotators. The rotation is companion-induced, as both objects turn out to be
spectroscopic binaries.Comment: 12 pages, 7 figures, accepted for publication in A&A, language
editing changes onl
Second-order corrections to neutrino two-flavor oscillation parameters in the wave packet approach
We report about an analytic study involving the {\em intermediate} wave
packet formalism for quantifying the physically relevant information which
appear in the neutrino two-flavor conversion formula and help us to obtain more
precise limits and ranges for neutrino flavor oscillation. By following the
sequence of analytic approximations where we assume a strictly peaked momentum
distribution and consider the second-order corrections in a power series
expansion of the energy, we point out a {\em residual} time-dependent phase
which, coupled with the {\em spreading/slippage} effects, can subtly modify the
neutrino oscillation parameters and limits. Such second-order effects are
usually ignored in the relativistic wave packet treatment, but they present an
evident dependence on the propagation regime so that some small modifications
to the oscillation pattern, even in the ultra-relativistic limit, can be
quantified. These modifications are implemented in the confront with the
neutrino oscillation parameter range (mass-squared difference \Delta m^{\2}
and the mixing-angle ) where we assume the same wave packet parameters
previously noticed in the literature in a kind of {\em toy model} for some
reactor experiments. Generically speaking, our analysis parallels the recent
experimental purposes which concern with higher precision parameter
measurements. To summarize, we show that the effectiveness of a more accurate
determination of \Delta m^{\2} and depends on the wave packet width
and on the averaged propagating energy flux which still
correspond to open variables for some classes of experiments. \Comment: 25 pages, 5 figure
Candelilla wax edible coating with Flourensia cernua bioactives to prolong the quality of tomato fruits
The improvement of the postharvest quality of tomato fruits was evaluated using an edible coating functionalized with an Flourensia cernua extract evaluating the antifungal, structural, barrier, and optical properties. The formulation and evaluation of an edible coating and its application on tomato was evaluated using a response surface methodology to determine the ideal concentrations of candelilla wax, whey protein, and glycerol. Edible films showed good barrier properties, with water vapor permeability varying from 0.4350.404 g mm/m2 day kPa. The addition o F. cernua extract showed significant improvement in the transparency of films. The edible coating applied to tomato reduced weight and firmness loss. The sensory evaluation proved that the product obtained is acceptable for consumers. The edible coating added with F. cernua extract was the most effective in inhibiting the growth of pathogenic fungi and the visual appearance at the end of storage confirmed the beneficial effect of the edible coating.(undefined)info:eu-repo/semantics/publishedVersio
Magnetic moments of the low-lying , resonances within the framework of the chiral quark model
The magnetic moments of the low-lying spin-parity ,
resonances, like, for example, ,
, as well as their transition magnetic moments, are
calculated using the chiral quark model. The results found are compared with
those obtained from the nonrelativistic quark model and those of unitary chiral
theories, where some of these states are generated through the dynamics of two
hadron coupled channels and their unitarization
Systematic study of optical potential strengths in reactions on Sn 120 involving strongly bound, weakly bound, and exotic nuclei
We present new experimental angular distributions for the elastic scattering of Li6+Sn120 at three bombarding energies. We include these data in a wide systematic involving the elastic scattering of He4,6,Li7, Be9,B10, and O16,18 projectiles on the same target at energies around the respective Coulomb barriers. Considering this data set, we report on optical model analyses based on the double-folding São Paulo potential. Within this approach, we study the sensitivity of the data fit to different models for the nuclear matter densities and to variations in the optical potential strengths.Fil: Alvarez, M. A. G.. Universidad de Sevilla; EspañaFil: Fernández GarcÃa, J. P.. Universidad de Sevilla; EspañaFil: León GarcÃa, J. L.. Universidad de Sevilla; EspañaFil: RodrÃguez Gallardo, M.. Universidad de Sevilla; EspañaFil: Gasques, L. R.. Universidade de Sao Paulo; BrasilFil: Chamon, L. C.. Universidade de Sao Paulo; BrasilFil: Zagatto, V. A. B.. Universidade de Sao Paulo; BrasilFil: Lépine Szily, A.. Universidade de Sao Paulo; BrasilFil: Oliveira, J. R. B.. Universidade de Sao Paulo; BrasilFil: Scarduelli, V.. Universidade Federal Fluminense; BrasilFil: Carlson, B. V.. Instituto Tecnologico de Aeronautica.; BrasilFil: Casal, J.. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Arazi, Andres. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentina. Comisión Nacional de EnergÃa Atómica; ArgentinaFil: Torres, D. A.. Universidad Nacional de Colombia; ColombiaFil: Ramirez, F.. Universidad Nacional de Colombia; Colombi
Spectroscopic binaries among Hipparcos M giants III. The eccentricity-period diagram and mass-transfer signatures
This paper is the third one in a series devoted to studying the properties of
binaries involving M giants. We use a new set of orbits to construct the first
(e-logP) diagram of an extensive sample of M giant binaries, to obtain their
mass-function distribution, and to derive evolutionary constraints for this
class of binaries and related systems. The orbital properties of binaries
involving M giants were analysed and compared with those of related families of
binaries (K giants, post-AGB stars, barium stars, Tc-poor S stars). The orbital
elements of post-AGB stars and M giants are not different, which may very
indicate that, for the considered sample of post-AGB binaries, the post-AGB
star left the AGB at quite an early stage (M4 or so). Neither are the orbital
elements of post-mass-transfer binaries like barium stars very different from
those of M giants, suggesting that the mass transfer did not alter the orbital
elements much, contrary to current belief. Finally, we show that binary systems
with e < 0.4 log P - 1 (with periods expressed in days) are predominantly
post-mass-transfer systems, because (i) the vast majority of barium and S
systems match this condition, and (ii) these systems have companion masses
peaking around 0.6 solar mass, as expected for white dwarfs. The latter
property has been shown to hold as well for open-cluster binaries involving K
giants, for which a lower bound on the companion mass may easily be set.Comment: 14 pages, 12 figures, accepted for publication in A&A, language
editing changes onl
The Sensitivity of HAWC to High-Mass Dark Matter Annihilations
The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view
detector sensitive to gamma rays of 100 GeV to a few hundred TeV. Located in
central Mexico at 19 degrees North latitude and 4100 m above sea level, HAWC
will observe gamma rays and cosmic rays with an array of water Cherenkov
detectors. The full HAWC array is scheduled to be operational in Spring 2015.
In this paper, we study the HAWC sensitivity to the gamma-ray signatures of
high-mass (multi- TeV) dark matter annihilation. The HAWC observatory will be
sensitive to diverse searches for dark matter annihilation, including
annihilation from extended dark matter sources, the diffuse gamma-ray emission
from dark matter annihilation, and gamma-ray emission from non-luminous dark
matter subhalos. Here we consider the HAWC sensitivity to a subset of these
sources, including dwarf galaxies, the M31 galaxy, the Virgo cluster, and the
Galactic center. We simulate the HAWC response to gamma rays from these sources
in several well-motivated dark matter annihilation channels. If no gamma-ray
excess is observed, we show the limits HAWC can place on the dark matter
cross-section from these sources. In particular, in the case of dark matter
annihilation into gauge bosons, HAWC will be able to detect a narrow range of
dark matter masses to cross-sections below thermal. HAWC should also be
sensitive to non-thermal cross-sections for masses up to nearly 1000 TeV. The
constraints placed by HAWC on the dark matter cross-section from known sources
should be competitive with current limits in the mass range where HAWC has
similar sensitivity. HAWC can additionally explore higher dark matter masses
than are currently constrained.Comment: 15 pages, 4 figures, version to be published in PR
The clustering of ultra-high energy cosmic rays and their sources
The sky distribution of cosmic rays with energies above the 'GZK cutoff'
holds important clues to their origin. The AGASA data, although consistent with
isotropy, shows evidence for small-angle clustering, and it has been argued
that such clusters are aligned with BL Lacertae objects, implicating these as
sources. It has also been suggested that clusters can arise if the cosmic rays
come from the decays of very massive relic particles in the Galactic halo, due
to the expected clumping of cold dark matter. We examine these claims and show
that both are in fact not justified.Comment: 13 pages, 8 figures, version in press at Phys. Rev.
- …