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21.
Environmental pollution affects parasite populations and communities, both directly and through effects on intermediate and final hosts. In this work, we present a comparative study on the structure and composition of metazoan parasite communities in the bogue, Boops boops, from two localities (Galician coast, Spain) affected by the Prestige oil-spill (POS). We focus on the distribution of both individual parasite species and larger functional groupings by using both univariate and multivariate analyses. Our results indicate directional trends in community composition that might be related to the Prestige oil-spill disturbance of the natural coastal communities off Galicia. Endoparasite communities in B. boops reflected a notable change in the composition and abundance of the benthic fauna in the localities studied post-spill probably due to organic enrichment after the POS. 相似文献
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Pablo F. Velázquez Yolanda Gómez Alejandro Esquivel Alejandro C. Raga 《Monthly notices of the Royal Astronomical Society》2007,382(4):1965-1970
The bipolar morphology of the planetary nebula (PN) K 3 − 35 observed in radio-continuum images was modelled with 3D hydrodynamic simulations with the adaptive grid code yguazú-a . We find that the observed morphology of this PN can be reproduced considering a precessing jet evolving in a dense AGB circumstellar medium, given by a mass-loss rate and a terminal velocity v w = 10 km s−1 . Synthetic thermal radio-continuum maps were generated from numerical results for several frequencies. Comparing the maps and the total fluxes obtained from the simulations with the observational results, we find that a model of precessing dense jets, where each jet injects material into the surrounding CSM at a rate (equivalent to a density of 8 × 104 cm−3 ), a velocity of 1500 km s−1 , a precession period of 100 yr and a semi-aperture precession angle of 20° agrees well with the observations. 相似文献
24.
Oscar Peralta Darrel Baumgardner Graciela B. Raga 《Journal of Atmospheric Chemistry》2007,57(2):153-169
Spectrothermography, defined as the evaluation of thermograms of carbon evolved from heated aerosol samples, is a technique
for evaluating differences in particle characteristics as they relate to emission sources and processes that modify particle
evolution. Here we describe the inherent uncertainties and demonstrate the utility of this technique with an evaluation of
samples that were collected with eight stage cascade impactors at three sites in Mexico City over a period of 5 months. The
study was implemented with statistical analysis based on tests for goodness of fit to separate thermograms with distinctive
shapes related to the relative amounts of organic and elemental carbon mass that evolves as a function of temperature. Thermograms
with unique shapes were found for particles with aerodynamic diameters of 1–10, 0.56–1, 0.32–0.56 and 0.18–0.32 μm with further
differentiation of curves related to the relative amounts of gasoline and diesel fuel that was combusted in the region of
the three sites. The common shapes fit 32–42% of samples in each particle size range and indicate that this type of analysis
can help distinguish differences in the primary sources of organic and elemental carbon.
相似文献
| Darrel BaumgardnerEmail: |
25.
Marine debris represents an important threat for sea turtles, but information on this topic is scarce in some areas, such as the Mediterranean sea. This paper quantifies marine debris ingestion in 54 juvenile loggerhead sea turtles (Caretta caretta) illegally captured by fishermen in Spanish Mediterranean waters. Curved carapace length was measured, necropsies were performed and debris abundance and type was recorded. Different types of debris appeared in the gastrointestinal tract of 43 turtles (79.6%), being plastics the most frequent (75.9%). Tar, paper, Styrofoam, wood, reed, feathers, hooks, lines, and net fragments were also present. A regression analysis showed that the volume of debris increased proportionally to the size of the turtles. The high variety of debris found and the large differences in ingestion among turtles indicated low feeding discrimination of this species that makes it specially prone to debris ingestion. Our data suggest that more severe control of litter spills and greater promotion of environmental educational programmes are needed in the Western Mediterranean. 相似文献
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We present results of MHD axisymmetrical cylindrical simulations performed to study Hα emission maps from jets, with a toroidal field geometry for the magnetic field. Our code uses a linear Riemann solver, integrates equations in 2.5 dimensions and includes the calculation of the ionization fraction and the effects of the emission due to the collisional excitation of [O I] and [O II] lines, radiative recombination of H and the collisional ionization of H and excitation of Lyman-α. The simulations with variable ejection velocities show that the magnetic field produces an increase in the emission from all of the knots except for the first bow shock. 相似文献
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A. Raga H. Sobral M. Villagrán-Muniz R. Navarro-González E. Masciadri 《Monthly notices of the Royal Astronomical Society》2001,324(1):206-212
We present a comparison between a plasma-generated 'starting jet' experiment and an axisymmetric numerical simulation of the flow. The experimental flow and the numerical simulation give results that agree both qualitatively and quantitatively, showing that the complex vortical structures arising in the flow are surprisingly well reproduced by the numerical model. This result inspires confidence in the accuracy of astrophysical jet numerical simulations. Also, even though the Mach number of our laboratory jet is somewhat low ( M ∼0.5), the dimensionless parameters of this jet are not very far from those expected for Faranoff–Riley class I radio jets. 相似文献
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We present results of a numerical simulation of a stellar jet from a source with supersonic variations in the outflow velocity. The simulation is compared with both analytical predictions and observations. 相似文献
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We present an analytic model for the thin-shell, radiative interaction between a hypersonic, plane-parallel wind and a rigid, spherical obstacle. This problem has clear applications, e.g., to the interaction of winds from young stars and dense cloudlets, and to the interaction of the wind from a binary partner with the photosphere of the second star. We also present a comparison of the analytic model with a full, axisymmetric numerical simulation. We find only a partial agreement between the numerical simulation and the analytic model, apparently as a result of the very strong 'thin-shell' instabilities of the post-bow shock flow. Our analytic model predicts the surface density, flow velocity and the energy radiated per unit area, as well as the total luminosity of the bow shock. The model can therefore be used directly for carrying out comparisons with observations of different astrophysical objects. 相似文献
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We have performed 3D numerical simulations of an over-pressurized Herbig–Haro-type jet which propagates into a sidestreaming environment. The interaction between the jet and the sidewind results in a perpendicular acceleration of the jet material, and a consequent curvature of the jet as it moves into the anisotropic medium. We find that an approximately steady configuration is achieved both for a sidewind that is perpendicular to the jet and for a sidewind inclined at 45° towards the jet source. The curvature obtained in both these models is consistent with analytic models of the jet/sidewind problem. We have also calculated Hα maps, which show an emitting sheath around the upwind (with respect to the sidewind) side of the jet beam. This emitting sheath may explain part of the observed emission from curved stellar jets. 相似文献