431 research outputs found
Abundance of Petrolisthes armatus (Crustacea: Porcellanidae) on a tropical estuarine intertidal rocky beach, Gulf of Nicoya estuary, Costa Rica
Se estudió, de diciembre de 1997 a noviembre de 1998 (14 fechas), la población del cagrejo porcelánido Petrolisthes armatus en dos sitios en una playa rocosa de entre mareas en el Golfo de Nicoya, costa pacífica de Costa Rica. Se hizo arrastres horizontales, en marea alta, con una red de plancton (280 micrómetros de malla) para verificar la presencia de sus larvas. Los cangrejos fueron recolectados cada 3 m a lo largo de tres transectos de 18 m de longitud en cada sitio. Se utilizó un recipiente sin fondo pero con un borde de tela adherido para evitar el escape de los organismos. Se
recolectó un total de 15 382 P. armatus. Los machos incluyeron 2 777 individuos y 3 518 las hembras, para una relación entre sexos de 1: 1.26. Se encontró hembras ovígeras en todas las fechas y éstas estuvieron representadas por 2 937 cangrejos (83% del total). Los arrastres de plancton capturaron 73 larvas de P.armatus (Zoea I), con una densidad promedio de 1.2 larvas/ m3. No se encontró diferencias estadísticamente significativas entre las abundancias presentes durante las estaciones seca y lluviosa típicas del Golfo de Nicoya. P. armatus se reproduce aparentemente durante todo el año en el Golfo. Sin embargo, hubo presencia de máximos de abundancia en ambas estaciones, lo que hace las oscilaciones poblaciones de esta especie similares a las presentadas por otros crustáceos en el Golfo de Nicoya.Population of the porcellanid crab Petrolisthes armatus was studied on a rocky intertidal beach located at the Punta Morales peninsula in the mid upper Gulf of Nicoya estuary, Pacific coast of Costa Rica, from December 1997 to November 1998 (14 dates). Horizontal plankton tows (280 micron mesh net) were also made to verify the presence of P. armatus larvae.Crabs were collected every 3 m along three 18 m long transects, at two sites on the beach, by placing a bottomless bucket fringed with canvas to prevent the organisms from escaping under the rim. A total of 15 382 P. armatus were collected. Only 146 (0.95%) crabs had a carapace lenght longer than 10 mm, and 8 995 (58.5%) were in the size range of 2 to 4.5 mm. The remaining crabs 6 241 (40.5%) were in the size range of 4.6 to 10 mm. Male and female
P. armatus were represented by 2 777 and 3 518 individuals respectively, with a sex ratio of 1:1.26. Ovigerous females were found at all dates and included 2 937 individuals (83 % of females). Plankton tows yielded only 73 larvae of P. armatus(Zoea 1), with a density of 1.2 larvae/m3. No statistically significant seasonal trends in the population of this species were detected. P. armatus appears to reproduce continuously the year around in Punta Morales, and some peaks of abundance were present during the dry and rainy seasons. These trends are similar to trends reported for other crustacean species in the Gulf of Nicoya.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de BiologíaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR
Detection of frequency spacings in the young O-type binary HD 46149 from CoRoT photometry
Using the CoRoT space based photometry of the O-type binary HD46149, stellar
atmospheric effects related to rotation can be separated from pulsations,
because they leave distinct signatures in the light curve. This offers the
possibility of characterising and exploiting any pulsations seismologically.
Combining high-quality space based photometry, multi-wavelength photometry,
spectroscopy and constraints imposed by binarity and cluster membership, the
detected pulsations in HD46149 are analyzed and compared with those for a grid
of stellar evolutionary models in a proof-of-concept approach. We present
evidence of solar-like oscillations in a massive O-type star, and show that the
observed frequency range and spacings are compatible with theoretical
predictions. Thus, we unlock and confirm the strong potential of this
seismically unexplored region in the HR diagram.Comment: 11 pages, 12 figures, accepted for publication in A&
How does the beach ecosystem change without tourists during COVID-19 lockdown?
Urban tourist beach ecosystems provide the essential service of recreation. These ecosystems also support critical ecological functions where biodiversity conservation is not usually a priority. The sudden lockdown due to the COVID-19 pandemic created a unique opportunity to evaluate the effects of human absence in these urban-coastal ecosystems. This study examined bioindicators from 29 urban tourist beaches in seven Latin-American countries and assesses their response to lockdown about some relevant anthropogenic stressors such as pollution, noise, human activities, and user density. The presence of animals and plants, as well as the intensity of stressors, were assessed through a standardized protocol during lockdown conditions. Additionally, the environmental conditions of the beaches before and during lockdown were qualitatively compared using multivariate non-parametric statistics. We found notable positive changes in biological components and a clear decrease in human stressors on almost all the beaches. Dune vegetation increased on most sites. Similarly, high burrow densities of ghost crabs were observed on beaches, except those where cleaning activity persisted. Because of the lockdown, there was an exceptionally low frequency of beach users, which in turn reduced litter, noise and unnatural odors. The observed patterns suggest that tourist beaches can be restored to natural settings relatively quickly. We propose several indicators to measure changes in beaches once lockdown is relaxed. Adequate conservation strategies will render the recreational service of tourist beaches more environmental-friendly
Might some gamma ray bursts be an observable signature of natural wormholes?
The extragalactic microlensing scenario for natural wormholes is examined. It
is shown that the main features of wormhole lensing events upon the light of
distant Active Galactic Nuclei (AGNs) are similar to some types of already
observed Gamma Ray Bursts (GRBs). Using recent satellite data on GRBs, an upper
limit to the negative mass density -- g cm --
under the form of wormhole-like objects is presented.Comment: extended version, additions on GRB physics, background sources and
cosmological consequences. Two ps figures. Accpeted for publication in Phys.
Rev.
Spatial clustering in the ESO-Sculptor Survey: two-point correlation functions by galaxy type at redshifts 0.1 - 0.5
We calculate the spatial two-point auto and cross-correlation functions for
the 765 galaxies with Rc<21.5 and 0.1<z<0.51 in the ESO-Sculptor survey, and
explore the segregation effects among the populations of giant (early-type,
late spiral) and dwarf (dE, dI) galaxies. At separation of 0.3 h^-1 Mpc, pairs
of early-type galaxies dominate the clustering over all the other types of
pairs. At intermediate scales, 0.3-5 h^-1 Mpc, mixed pairs of dwarf and giant
galaxies contribute equally as pairs of giant galaxies, whereas the latter
dominate at ~10 h^-1 Mpc. We detect the signature of the transition between the
1-halo and 2-halo regimes which is expected in the scenario of galaxy formation
by hierarchical merging of dark matter halos. The early-type galaxies largely
outdo the late spiral galaxies in their 1-halo component, whereas the 2-halo
components of both giant populations are comparable. The dwarf galaxies have an
intermediate 1-halo component between the 2 giant galaxy types, and their
2-halo component is weak and consistent with null clustering. The present
analysis indicates that the early-type galaxies are preferentially located near
the centers of the most massive halos, whereas late spiral galaxies tend to
occupy their outskirts or the centers of less massive halos. This analysis also
unveils new results on the spatial distribution of dwarf galaxies: at the scale
at which they significantly cluster inside the halos (<0.3 h^-1 Mpc), they are
poorly mixed with the late spiral galaxies, and appear preferentially as
satellites of early-type galaxies.Comment: Astronomy & Astrophysics, in press. 29 pages, 15 color figures, 3
table
Designer Magnetoplasmonics with Nickel Nanoferromagnets
We introduce a new perspective on magnetoplasmonics in nickel nanoferromagnets by exploiting the phase tunability of the optical polarizability due to localized surface plasmons and simultaneous magneto-optical activity. We demonstrate how the concerted action of nanoplasmonics and magnetization can manipulate the sign of rotation of the reflected light’s polarization (i.e., to produce Kerr rotation reversal) in ferromagnetic nanomaterials and, further, how this effect can be dynamically controlled and employed to devise conceptually new schemes for biochemosensing. © 2011 American Chemical Society.A.D. and Z.P. acknowledge support from the Swedish Research Council and Swedish Foundation for Strategic Research (Framework program Functional Electromagnetic Metamaterials,
project RMA08). J.Å. acknowledges support from the Swedish Research Council, the Swedish Foundation for Strategic Research (Future Research Leader Programme), and the G€oran Gustafsson Foundation. J.Å. is a Royal Swedish Academy of Sciences Research Fellow supported by a grant from the Knut and Alice Wallenberg Foundation. V.B. acknowledges the G€oran Gustafsson Foundation and the Blanceflor Boncompagni-Ludovisi Foundation. P.V. acknowledges funding from the Basque Government
through the ETORGAI Program, Project No. ER-
2010/00032 and Program No. PI2009-17, the Spanish Ministry of Science and Education under Projects No. CSD2006-53 and No. MAT2009-07980. J.N. acknowledges funding for the Generalitat de Catalunya and the Spanish Ministry of Science and
Education through No. 2009-SGR-1292 and No. MAT2010-20616-C02 projects.Peer Reviewe
The Pierre Auger Observatory III: Other Astrophysical Observations
Astrophysical observations of ultra-high-energy cosmic rays with the Pierre
Auger ObservatoryComment: Contributions to the 32nd International Cosmic Ray Conference,
Beijing, China, August 201
A search for point sources of EeV photons
Measurements of air showers made using the hybrid technique developed with
the fluorescence and surface detectors of the Pierre Auger Observatory allow a
sensitive search for point sources of EeV photons anywhere in the exposed sky.
A multivariate analysis reduces the background of hadronic cosmic rays. The
search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an
energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been
detected. An upper limit on the photon flux has been derived for every
direction. The mean value of the energy flux limit that results from this,
assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial
direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in
which EeV cosmic ray protons are emitted by non-transient sources in the
Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Reconstruction of inclined air showers detected with the Pierre Auger Observatory
We describe the method devised to reconstruct inclined cosmic-ray air showers
with zenith angles greater than detected with the surface array of
the Pierre Auger Observatory. The measured signals at the ground level are
fitted to muon density distributions predicted with atmospheric cascade models
to obtain the relative shower size as an overall normalization parameter. The
method is evaluated using simulated showers to test its performance. The energy
of the cosmic rays is calibrated using a sub-sample of events reconstructed
with both the fluorescence and surface array techniques. The reconstruction
method described here provides the basis of complementary analyses including an
independent measurement of the energy spectrum of ultra-high energy cosmic rays
using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of
Cosmology and Astroparticle Physics (JCAP
Azimuthal asymmetry in the risetime of the surface detector signals of the Pierre Auger Observatory
The azimuthal asymmetry in the risetime of signals in Auger surface detector
stations is a source of information on shower development. The azimuthal
asymmetry is due to a combination of the longitudinal evolution of the shower
and geometrical effects related to the angles of incidence of the particles
into the detectors. The magnitude of the effect depends upon the zenith angle
and state of development of the shower and thus provides a novel observable,
, sensitive to the mass composition of cosmic rays
above eV. By comparing measurements with predictions from
shower simulations, we find for both of our adopted models of hadronic physics
(QGSJETII-04 and EPOS-LHC) an indication that the mean cosmic-ray mass
increases slowly with energy, as has been inferred from other studies. However,
the mass estimates are dependent on the shower model and on the range of
distance from the shower core selected. Thus the method has uncovered further
deficiencies in our understanding of shower modelling that must be resolved
before the mass composition can be inferred from .Comment: Replaced with published version. Added journal reference and DO
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