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81.
Luigi Caputi Francesco Toscano Michele Arienzo Luciano Ferrara Gabriele Procaccini Paolo Sordino 《Marine Ecology》2019,40(2)
The capacity for ascidians to inhabit coastal sea floor worldwide relies on their peculiar tolerance to environmental variables and pollution, which is considered, together with high levels of genetic diversity, among the main drivers of their invasive potential. In spite of the continued interest in the genetics of invasive species, little attention has been paid toward the microevolutionary processes that drive structure and fate of ascidian populations over time under chemically polluted conditions. Understanding the interplay between environmental and population dynamics is critical to predict the biodiversity of marine coastal ecosystems. In the present study, a local population of the ascidian Ciona robusta living in the Fusaro Lagoon has been monitored over a 13‐month period of sampling. Physico‐chemical parameters (temperature, salinity, turbidity, dissolved oxygen, heavy metals), genetic composition (microsatellites, ITS‐2), abundance and biomass (wet and dry weight) were assessed with the aim to infer fine‐scale temporal variation of population structure with respect to rapid environmental change. Analysis of biomass showed that C. robusta is highly sensitive to salinity and oxygen concentrations. Further, genetic analysis suggested a highly dynamic population structure, likely due to the strong clustering of temporal samples and distinct responses to environmental conditions, including bioaccumulation of heavy metals. Here, we hypothesize that rapid variation in allele frequencies of neutral markers in C. robusta populations may increase the ability of the species to colonize habitats that are subject to strong variation and are under heavy human pressure. 相似文献
82.
Gravity field and interior of Rhea from Cassini data analysis 总被引:1,自引:0,他引:1
Luciano Iess Nicole J. Rappaport Jonathan Lunine Sami W. Asmar Francesco Zingoni 《Icarus》2007,190(2):585-593
The Cassini spacecraft encountered Rhea on November 26, 2005. Analysis of the Doppler data acquired at and around closest approach yields the mass of Rhea and the quadrupole moments of its gravity field with unprecedented accuracy. We obtained which corresponds to a density of . Our results for J2 and C22 are (7.947±0.892)×10−4 and (2.3526±0.0476)×10−4, respectively. These values are consistent with hydrostatic equilibrium. From the value of C22, we infer the non-dimensional moment of inertia C/MR2=0.3721±0.0036. Our models of Rhea's interior based on the gravity data favor an almost undifferentiated satellite. A discontinuity between a core and a mantle is possible but not required by the data. Models with a constant silicate mass fraction throughout the body cannot account for the determined quadrupole coefficients. The data exclude fully differentiated models in which the core would be composed of unhydrated silicates and the mantle would be composed of pure ice. If the mantle contains 10% in mass of silicates, the core extends to 630 km in radius and has a silicate mass fraction of 40%. A continuous model in which the silicates are more concentrated toward the center of the body than in the outer layers is allowed by the gravity data but excluded by thermal evolution considerations. The one model that fits the gravity data and is self-consistent when energy transport and ice melting are qualitatively considered is an “almost undifferentiated” Rhea, in which a very large uniform core is surrounded by a relatively thin ice shell containing no rock at all. 相似文献
83.
84.
Ernazar B. Abdikamalov Harald Dimmelmeier Luciano Rezzolla John C. Miller 《Monthly notices of the Royal Astronomical Society》2009,392(1):52-76
An increase in the central density of a neutron star may trigger a phase transition from hadronic matter to deconfined quark matter in the core, causing it to collapse to a more compact hybrid star configuration. We present a study of this, building on previous work by Lin et al.. We follow them in considering a supersonic phase transition and using a simplified equation of state, but our calculations are general relativistic (using 2D simulations in the conformally flat approximation) as compared with their 3D Newtonian treatment. We also improved the treatment of the initial phase transformation, avoiding the introduction of artificial convection. As before, we find that the emitted gravitational wave spectrum is dominated by the fundamental quasi-radial and quadrupolar pulsation modes but the strain amplitudes are much smaller than suggested previously, which is disappointing for the detection prospects. However, we see significantly smaller damping and observe a non-linear mode resonance which substantially enhances the emission in some cases. We explain the damping mechanisms operating, giving a different view from the previous work. Finally, we discuss the detectability of the gravitational waves, showing that the signal-to-noise ratio for current or second generation interferometers could be high enough to detect such events in our Galaxy, although third generation detectors would be needed to observe them out to the Virgo cluster, which would be necessary for having a reasonable event rate. 相似文献
85.
86.
Fabrizio Nestola Joseph R. Smyth Luciano Secco Marco Bruno Alberto Dal Negro 《Geochimica et cosmochimica acta》2009,73(2):489-3427
A non-stoichiometric sample of spinel with composition T(Mg0.4Al0.6)M(Al1.8□0.2)O4 was investigated by single-crystal X-ray diffraction in situ up to about 8.7 GPa using a diamond anvil cell. The P(V) data were fitted using a third-order Birch-Murnaghan equation of state and the unit-cell volume V0, the bulk modulus KT0 and its first pressure derivative K′ were refined simultaneously providing the following coefficients: V0 = 510.34(6) Å3, KT0 = 171(2) GPa, K′ = 7.3(6). This KT0 value represents the lowest ever found for spinel crystal structures. Comparing our data with a stoichiometric and natural MgAl2O4 (pure composition) we observe a decrease in KT0 by about 11.5% and a strong increase in K′ by about 33%. These results demonstrate how an excess of Al accompanied by the formation of significant cation vacancies at octahedral site strongly affects the thermodynamic properties of spinel structure. If we consider that the estimated mantle composition is characterized by 3-5% of Al2O3 this could imply an Mg/Al substitution with possible formation of cation vacancies. The results of our study indicate that geodynamic models should take into account the potential effect of Mg/Al substitution on the incompressibility of the main mantle-forming minerals (olivine, wadsleyite, ringwoodite, Mg-perovskite). 相似文献
87.
Sebastiano Imposa Jean-Pierre Fourno Rosario Raffaele Antonio Scaltrito Luciano Scarfi 《Central European Journal of Geosciences》2009,1(4):416-423
A one-dimensional velocity model and station corrections for the Middle-Durance fault zone (south-eastern France) were computed by inverting P-wave arrival times recorded on a local seismic network of 8 stations. A total of 93 local events with a minimum of 6 P-phases, RMS 0.4 s and a maximum gap of 220° were selected. Comparison with previous earthquake locations shows an improvement for the relocated earthquakes. Tests were carried out to verify the robustness of inversion results in order to corroborate the conclusions drawn from our findings. The obtained minimum 1-D velocity model can be used to improve routine earthquake locations and represents a further step toward more detailed seismotectonic studies in this area of south-eastern France. 相似文献
88.
Luciano Morselli Elena Bernardi Ivano Vassura Fabrizio Passarini Enrico Tesini 《Journal of Atmospheric Chemistry》2008,59(3):151-170
The results of a 8 year survey of wet and dry depositions collected in Bologna (Northern Italy) are presented and discussed:
monthly fluxes of the main ions (hydrogen, sodium, potassium, calcium, magnesium, ammoniacal and nitrate nitrogen, sulphate
and chloride) have been registered and statistically discussed. The trend of hydrogen ion, whose largest correlation in the
global deposition was found with sulphate, is clearly downwards, with peaks mainly in winter months. By means of a data factor
analysis, three main sources to explain the variability of the deposition chemistry were recognized: an anthropogenic contribution
(particularly represented by NO3
−, SO4
2−, H+), the sea spray (Na+, Cl− and, to a lesser extent, K+ and Mg2+) and a terrigenous fraction, particularly characterized by higher Ca2+ concentration; however, some concentration peaks of this ion have been found in association with some episodes of Saharan
dust transportation. 相似文献
89.
Luciano Telesca Michele Lovallo Joan Martì Molist Carmen López Moreno Rafael Abella Meléndez 《地学学报》2014,26(6):425-429
We investigated the dynamics of the continuous seismic signal recorded before and during the 2011–2012 El Hierro eruption (Canary Islands) using the innovative approach of the Fisher–Shannon method, a suitable statistical tool for detecting dynamic changes in complex systems. Our findings identify dynamic changes in the seismic signal that can be correlated with different stress states of the magmatic setting and the plumbing system in the volcano at El Hierro. The results contribute to the understanding of the fracturing pattern in the crust during a new intrusion and eruption of an overpressurized batch of magma. 相似文献