2,002 research outputs found
Las especies del gĂŠnero Myotis (Chiroptera: Vespertilionidae) en el bajo delta del ParanĂĄ y la pampa ondulada, Argentina
El gĂŠnero Myotis se distribuye en todo el mundo, excepto en los polos, e incluye mĂĄs de 100 especies, de las cuales 12 se presentan en Argentina. El conocimiento sobre los murciĂŠlagos de este gĂŠnero es escaso en amplias ĂĄreas de Argentina, como por ejemplo en la Pampa Ondulada y el Bajo Delta del ParanĂĄ. En este trabajo se estudian las especies de Myotis colectadas en tres localidades del ĂĄrea mencionada: dos en el departamento Islas del Ibicuy (provincia de Entre RĂos), y una en el Parque Costero Sur (provincia de Buenos Aires). Se presentan datos morfomĂŠtricos y caracterĂsticas de los ejemplares colectados, aportando informaciĂłn sobre la variabilidad intraespecĂfica de cada especie colectada en el ĂĄrea. En total se colectaron 51 ejemplares pertenecientes a 5 especies: M. albescens, M. dinellii, M. levis, M. ruber y M. riparius. Esta Ăşltima especie es registrada por primera vez para las provincias de Entre RĂos y Buenos Aires.The genus Myotis is distributed worldwide, except at the poles. It includes more than 100 species, 12 of which are present in Argentina. Knowledge about the bats of this genus is sparse in large areas of Argentina, including the Rolling Pampa and Lower Delta of the Parana River. Here, we present a study about the species of Myotis collected in three locations: two at Islas del Ibicuy department (Entre RĂos province), and one at Parque Costero del Sur (Buenos Aires province). Morphometric data and characteristics of the collected specimens are described, providing information on intraspecific variability of each species collected in the area. We collected 51 specimens belonging to 5 species of this genus: M. albescens, M. dinellii, M. levis, M. ruber and M. riparius. The latter is recorded for first time in the provinces of Entre RĂos and Buenos Aires.ISSN 1666-053
Study of the one-dimensional off-lattice hot-monomer reaction model
Hot monomers are particles having a transient mobility (a ballistic flight)
prior to being definitely absorbed on a surface. After arriving at a surface,
the excess energy coming from the kinetic energy in the gas phase is dissipated
through degrees of freedom parallel to the surface plane. In this paper we
study the hot monomer-monomer adsorption-reaction process on a continuum
(off-lattice) one-dimensional space by means of Monte Carlo simulations. The
system exhibits second-order irreversible phase transition between a reactive
and saturated (absorbing) phases which belong to the directed percolation (DP)
universality class. This result is interpreted by means of a coarse-grained
Langevin description which allows as to extend the DP conjecture to transitions
occurring in continuous media.Comment: 13 pages, 5 figures, final version to appear in J. Phys.
Population genetics in compressible flows
We study competition between two biological species advected by a
compressible velocity field. Individuals are treated as discrete Lagrangian
particles that reproduce or die in a density-dependent fashion. In the absence
of a velocity field and fitness advantage, number fluctuations lead to a
coarsening dynamics typical of the stochastic Fisher equation. We then study
three examples of compressible advecting fields: a shell model of turbulence, a
sinusoidal velocity field and a linear velocity sink. In all cases, advection
leads to a striking drop in the fixation time, as well as a large reduction in
the global carrying capacity. Despite localization on convergence zones, one
species goes extinct much more rapidly than in well-mixed populations. For a
weak harmonic potential, one finds a bimodal distribution of fixation times.
The long-lived states in this case are demixed configurations with a single
boundary, whose location depends on the fitness advantage.Comment: 10 pages, 5 figures, submitte
Transition to Stochastic Synchronization in Spatially Extended Systems
Spatially extended dynamical systems, namely coupled map lattices, driven by
additive spatio-temporal noise are shown to exhibit stochastic synchronization.
In analogy with low-dymensional systems, synchronization can be achieved only
if the maximum Lyapunov exponent becomes negative for sufficiently large noise
amplitude. Moreover, noise can suppress also the non-linear mechanism of
information propagation, that may be present in the spatially extended system.
A first example of phase transition is observed when both the linear and the
non-linear mechanisms of information production disappear at the same critical
value of the noise amplitude. The corresponding critical properties can be
hardly identified numerically, but some general argument suggests that they
could be ascribed to the Kardar-Parisi-Zhang universality class. Conversely,
when the non-linear mechanism prevails on the linear one, another type of phase
transition to stochastic synchronization occurs. This one is shown to belong to
the universality class of directed percolation.Comment: 21 pages, Latex - 14 EPS Figs - To appear on Physical Review
Reduction of Dispersion in Ultrasonically-Enhanced Micropacked Beds
Channeling of gas can reduce mass transfer performance in multiphase micropacked-bed reactors. Viscous and capillary forces cause this undesired and often unpredictable phenomenon in systems with catalyst particle sizes of hundreds of micrometers. In this work, we acoustically modify flow in a micropacked-bed reactor to reduce gas channeling by applying high-power sonication at low ultrasonic frequencies (âź40 kHz). Experimental residence time distributions reveal two orders of magnitude reduction in dispersion with ultrasound, allowing for nearly plug-flow behavior at high flow rates in the bed. Sonication appears to partially fluidize the packed-bed under pressurized cocurrent two-phase flow, effectively improving dispersion characteristics.This research was partially funded by the EU project MAPSYN: Microwave, Acoustic and Plasma SYNtheses, under Grant CPIP 309376 of the European Union Seventh Framework Program
KELT-8b: A highly inflated transiting hot Jupiter and a new technique for extracting high-precision radial velocities from noisy spectra
We announce the discovery of a highly inflated transiting hot Jupiter
discovered by the KELT-North survey. A global analysis including constraints
from isochrones indicates that the V = 10.8 host star (HD 343246) is a mildly
evolved, G dwarf with K, , , an inferred mass
M, and radius
R. The planetary companion has mass , radius
, surface gravity , and density
g cm. The planet is on a roughly
circular orbit with semimajor axis AU and
eccentricity . The best-fit linear ephemeris is
BJD and
days. This planet is one of the most inflated of all known transiting
exoplanets, making it one of the few members of a class of extremely low
density, highly-irradiated gas giants. The low stellar and large
implied radius are supported by stellar density constraints from follow-up
light curves, plus an evolutionary and space motion analysis. We also develop a
new technique to extract high precision radial velocities from noisy spectra
that reduces the observing time needed to confirm transiting planet candidates.
This planet boasts deep transits of a bright star, a large inferred atmospheric
scale height, and a high equilibrium temperature of
K, assuming zero albedo and perfect heat redistribution, making it one of the
best targets for future atmospheric characterization studies.Comment: Submitted to ApJ, feedback is welcom
KELT-7b: A hot Jupiter transiting a bright V=8.54 rapidly rotating F-star
We report the discovery of KELT-7b, a transiting hot Jupiter with a mass of
MJ, radius of RJ, and an orbital
period of days. The bright host star (HD33643;
KELT-7) is an F-star with , Teff K, [Fe/H]
, and . It has a mass of
Msun, a radius of Rsun, and
is the fifth most massive, fifth hottest, and the ninth brightest star known to
host a transiting planet. It is also the brightest star around which KELT has
discovered a transiting planet. Thus, KELT-7b is an ideal target for detailed
characterization given its relatively low surface gravity, high equilibrium
temperature, and bright host star. The rapid rotation of the star (
km/s) results in a Rossiter-McLaughlin effect with an unusually large amplitude
of several hundred m/s. We find that the orbit normal of the planet is likely
to be well-aligned with the stellar spin axis, with a projected spin-orbit
alignment of degrees. This is currently the second most
rapidly rotating star to have a reflex signal (and thus mass determination) due
to a planetary companion measured.Comment: Accepted to The Astronomical Journa
Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC
Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H âÎł Îł, H â Z Zâ â4l and H âW Wâ âlνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of âs = 7 TeV and âs = 8 TeV, corresponding to an integrated luminosity of about 25 fbâ1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined ďŹts probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson
Standalone vertex ďŹnding in the ATLAS muon spectrometer
A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at âs = 7 TeV collected with the ATLAS detector at the LHC during 2011
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