503 research outputs found
LA COMUNIDAD DE LAS AVES EN TRES HÁBITATS DE LA PLANICIE DE TABASCO, MÉXICO
The wealth and diversity of the bird community in three ecosystems of the Tabasco plain, México, was evaluated, associated to habitats with flood influence (mangrove, arrowroot-tule and floodable grasslands). Four sampling stations were established in each habitat and observations were performed during drought and rainy seasons in 2010 with three sampling days in each station. The sampling method was through fixed-radius observation in eight spots for each season. The data were taken at sunrise, sundown and night. 23,926 individuals of 155 bird species were identified, showing greater wealth and abundance during the rainy season (141 species and 12,595 individuals), of which 123 species were resident, 22 migratory, seven transitory, two local migratory and one summer resident. According to the Clench, there is 89 % completeness in the community. The arrowroot-tule stands showed the highest wealth (122), followed by mangroves (177) and grasslands (110). The first ecosystem was the most diverse (H´=3.69), followed by mangroves (H´=3.58), and in these environments the greatest similarity was observed (S=0.951). Of the species, 13.54% are protected by NOM-059- SEMARNAT-2010. The low zones of the Tabasco plain are very important in maintaining bird communities, in addition to serving as feeding and refuge zones for resident and migratory species.Se evaluó la riqueza y diversidad de la comunidad de aves en tres tipos de ecosistemas de la planicie tabasqueña, asociados a hábitats con influencia de inundación (manglares, popales-tulares y pastizales inundables). Se establecieron 12 estaciones de muestreo, cuatro para cada hábitat. Se trabajó en dos temporadas del año 2010 (secas y lluvias), se muestrearon por tres días en cada estación. El método de muestreo fue por observación de radio fijo en ocho puntos por cada estación. Los datos se tomaron en tres momentos del día (amanecer, atardecer y noche). Se identificaron 23,926 individuos de 155 especies de aves, donde la temporada de lluvias fue más rica y abundante (141 especies y 12,595 individuos) en comparación con la secas. De las cuales 123 especies fueron residentes, 22 migratorias, siete transitorias, dos migrantes locales y una residente de verano. De acuerdo a la Clench la se cuenta con el 89% de la completitud de la comunidad. Los popales-tulares presentaron la mayor riqueza (122), seguida por los manglares (117) y los pastizales (110). Los popales-tulares fueron los más diversos (H´=3.69), seguido por los manglares (H´=3.58). Los popales-tulares y los manglares son los ambientes donde se observó la mayor similitud (S=0.951). El 13.54 % de las especies se encuentra protegida por la NOM-059-SEMARNAT-2010. Las zonas bajas de la planicie de Tabasco, son muy importantes en el mantenimiento de la comunidad de aves, además de poder servir como zonas de alimentación y refugio para especies residentes y migratorias
EFECTO DE TRATAMIENTOS PRE-GERMINATIVOS EN LA CALIDAD DE PLÁNTULAS GUAPINOL (HYMENAEA COURBARIL)
This research has evaluated the effect of five pre-germination treatments on the quality and structure of plant locust (Hymenaea courbaril) due to the high variability in the germination and emergency tillage. Five treatments were evaluated by measuring the rate of Germanization and emergency speed; quality parameters (height and diameter) together with biomass (fresh and dry weight) of seedlings, bringing the Dickson quality index were estimated. Each treatment group contained 50 replicates for 250 plants in the experiment. The data were processed with statistical SPSS V.22.0: variance, standard deviation, variance analysis, obtaining statistical tests of binary correlations, repeated measures analysis and analysis of variance (ANOVA), intra and inter groups, 95% (P-valor 0.05) of confidence. The results show differences between treatments three (hydration) and four (mechanical scarification) regarding treatment one (thermal) and two (chemical) where no statistically significant difference. Treatment five (witness) has less statistical difference with all other evaluated. These same data for determining a positive effect between application of pre germination treatments and increased seedling quality of 93.0%, this translates to a greater chance of survival of the plant to be transplanted in the field. It is tested combination treatments one and three.Esta investigación ha evaluado el efecto que tiene cinco tratamientos pre-germinativos en la calidad y estructura de las planta de guapinol (Hymenaea courbaril) debido a la elevada variabilidad en la germinación y emergencia con la siembra directa. Se evaluaron cinco tratamientos, midiendo el índice de germanización y velocidad de emergencia, parámetros de calidad (altura y diámetro) junto con la de biomasa (peso fresco y seco) de las plántulas, con lo que se estimó el índice de calidad de Dickson. Cada uno de los tratamientos consto de 50 repeticiones para un total de 250 plántulas dentro del experimento. Los datos se procesaron SPSS V.22.0 con los estadísticos: varianza, desviación estándar, análisis de varianza, obteniendo las pruebas estadísticas de correlaciones binarias, análisis de medidas repetidas y análisis de varianza (ANOVA), intra e inter grupos, a un 95% (P-valor 0.05) de confianza. Los resultados muestran diferencia entre los tratamientos tres (hidratación) y cuatro (escarificación mecánica) respecto al tratamiento uno (térmico) y dos (químico) donde no hay diferencia estadísticamente significativa. El tratamiento cinco (testigo) presenta diferencia estadística menor con todos los demás evaluados. Estos mismos datos permiten determinar un efecto positivo entre la aplicación de tratamientos pre-germinativos y el aumento de la calidad de la plántula de un 93.0%, esto se traduce a mayores posibilidades de sobrevivencia de la planta al ser trasplantada en campo. Debe probarse la combinación de los tratamientos uno y tres
Influence of entrance-channel magicity and isospin on quasi-fission
The role of spherical quantum shells in the competition between fusion and
quasi-fission is studied for reactions forming heavy elements. Measurements of
fission fragment mass distributions for different reactions leading to similar
compound nuclei have been made near the fusion barrier. In general, more
quasi-fission is observed for reactions with non-magic nuclei. However, the
Ca+Pb reaction is an exception, showing strong evidence for
quasi-fission, though both nuclei are doubly magic. Time-dependent Hartree-Fock
calculations predict fast equilibration of in the two fragments early in
the collision. This transfer of nucleons breaks the shell effect, causing this
reaction to behave more like a non-magic one in the competition between fusion
and quasi-fission. Future measurements of fission in reactions with exotic
beams should be able to test this idea with larger asymmetries.Comment: accepted for publication in Physics Letters
Multimessenger astronomy with the Einstein Telescope
Gravitational waves (GWs) are expected to play a crucial role in the
development of multimessenger astrophysics. The combination of GW observations
with other astrophysical triggers, such as from gamma-ray and X-ray satellites,
optical/radio telescopes, and neutrino detectors allows us to decipher science
that would otherwise be inaccessible. In this paper, we provide a broad review
from the multimessenger perspective of the science reach offered by the third
generation interferometric GW detectors and by the Einstein Telescope (ET) in
particular. We focus on cosmic transients, and base our estimates on the
results obtained by ET's predecessors GEO, LIGO, and Virgo.Comment: 26 pages. 3 figures. Special issue of GRG on the Einstein Telescope.
Minor corrections include
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
Atmospheric parameters, such as pressure (P), temperature (T) and density,
affect the development of extensive air showers initiated by energetic cosmic
rays. We have studied the impact of atmospheric variations on extensive air
showers by means of the surface detector of the Pierre Auger Observatory. The
rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find
that the observed behaviour is explained by a model including the effects
associated with the variations of pressure and density. The former affects the
longitudinal development of air showers while the latter influences the Moliere
radius and hence the lateral distribution of the shower particles. The model is
validated with full simulations of extensive air showers using atmospheric
profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle
Physic
The exposure of the hybrid detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays.
It consists of a surface array to measure secondary particles at ground level
and a fluorescence detector to measure the development of air showers in the
atmosphere above the array. The "hybrid" detection mode combines the
information from the two subsystems. We describe the determination of the
hybrid exposure for events observed by the fluorescence telescopes in
coincidence with at least one water-Cherenkov detector of the surface array. A
detailed knowledge of the time dependence of the detection operations is
crucial for an accurate evaluation of the exposure. We discuss the relevance of
monitoring data collected during operations, such as the status of the
fluorescence detector, background light and atmospheric conditions, that are
used in both simulation and reconstruction.Comment: Paper accepted by Astroparticle Physic
The Fluorescence Detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a hybrid detector for ultra-high energy
cosmic rays. It combines a surface array to measure secondary particles at
ground level together with a fluorescence detector to measure the development
of air showers in the atmosphere above the array. The fluorescence detector
comprises 24 large telescopes specialized for measuring the nitrogen
fluorescence caused by charged particles of cosmic ray air showers. In this
paper we describe the components of the fluorescence detector including its
optical system, the design of the camera, the electronics, and the systems for
relative and absolute calibration. We also discuss the operation and the
monitoring of the detector. Finally, we evaluate the detector performance and
precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics
Research Section
Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory
The advent of the Auger Engineering Radio Array (AERA) necessitates the
development of a powerful framework for the analysis of radio measurements of
cosmic ray air showers. As AERA performs "radio-hybrid" measurements of air
shower radio emission in coincidence with the surface particle detectors and
fluorescence telescopes of the Pierre Auger Observatory, the radio analysis
functionality had to be incorporated in the existing hybrid analysis solutions
for fluoresence and surface detector data. This goal has been achieved in a
natural way by extending the existing Auger Offline software framework with
radio functionality. In this article, we lay out the design, highlights and
features of the radio extension implemented in the Auger Offline framework. Its
functionality has achieved a high degree of sophistication and offers advanced
features such as vectorial reconstruction of the electric field, advanced
signal processing algorithms, a transparent and efficient handling of FFTs, a
very detailed simulation of detector effects, and the read-in of multiple data
formats including data from various radio simulation codes. The source code of
this radio functionality can be made available to interested parties on
request.Comment: accepted for publication in NIM A, 13 pages, minor corrections to
author list and references in v
Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory
We present the results of searches for dipolar-type anisotropies in different
energy ranges above eV with the surface detector array of
the Pierre Auger Observatory, reporting on both the phase and the amplitude
measurements of the first harmonic modulation in the right-ascension
distribution. Upper limits on the amplitudes are obtained, which provide the
most stringent bounds at present, being below 2% at 99% for EeV
energies. We also compare our results to those of previous experiments as well
as with some theoretical expectations.Comment: 28 pages, 11 figure
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