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Multifractal analysis of earthquake catalogues 总被引：1，自引：0，他引：1
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Franco Cataldo Giovanni Strazzulla Susana Iglesias-Groth 《Monthly notices of the Royal Astronomical Society》2009,394(2):615-623
The stability of C60 and C70 fullerenes in the interstellar medium deposited on dust surface or embedded in meteorites and comets has been simulated with γ irradiation and with He+ ion bombardment. It is shown by vibrational spectroscopy that a γ radiation dose of 2.6 MGy (1 Gy = 1 joule absorbed energy per kilogram) causes partial oligomerization of both C60 and C70 fullerenes. Oligomers are made by fullerene cages chemically connected each other which can yield back free fullerenes by a thermal treatment. The amount of irreversibly polymerized fullerenes caused by 2.6 MGy as deduced as the toluene insoluble fraction has been determined as 1.7 and 15 per cent by weight, respectively, for C60 and C70 fullerene. The radiation dose generated by radionuclides decay and expected to be delivered to fullerenes buried at a depth of more than 20 m in comets and meteorites is about 3 MGy per 109 yr. Since fullerenes are by far resistant to such radiation dose they can survive for at least some billion years inside comets and meteorites and in fact have been detected inside certain carbonaceous chondrites. On the other hand, the direct exposure of fullerenes to cosmic rays for instance when they are adsorbed or deposited on the surface of carbon dust corresponds to the delivery of a radiation dose comprised between 30 and 65 MGy per 109 yr. Experimental bombardment of both C60 and C70 fullerenes for instance with He+ ions has shown that the complete amorphization occurs at about 250 MGy. Thus in ∼4 Gyr exposure to cosmic rays it is expected a complete amorphization. 相似文献
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Paula Sardiña Daniel H. Cataldo Demetrio Boltovskoy 《Aquatic Sciences - Research Across Boundaries》2009,71(4):479-486
We conducted a field experiment to assess the influence of conspecific adults on recruitment success of the golden mussel
Limnoperna fortunei. Tiles, 225 cm2 surface area, were used as artificial substrates in four treatments: control (blank tiles), low (800 mussels m−2), medium (4,000 mussels m−2) and high (12,000 mussels m−2) density treatments. Results indicated that recruitment was strongly affected by the presence and density of conspecifics.
After one and 3 months of exposure, numbers of recruits were significantly higher on tiles with conspecific adults than on
blank tiles, and there was a positive and significant relationship between the number of recruits and the number of adults
in the three treatments assayed. Also, after 3 months of exposure, recruits in all treatments with adults present were larger
than recruits in the control treatment. Our results suggest that conspecific adults have a positive effect on recruitment
success and growth of newly settled juveniles through factors that enhance larval settling or that contribute to the survival
of settlers in areas colonized by adult conspecifics. 相似文献
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In this paper we consider a spatially flat Friedmann-Robertson-Walker (FRW) cosmological model with cosmological constant,
containing a stiff fluid and a classical Dirac field. The proposed cosmological scenario describes the evolution of effective
dark matter and dark energy components reproducing, with the help of that effective multifluid configuration, the quintessential
behavior. We find the value of the scale factor where the effective dark energy component crosses the phantom divide. The
model we introduce, which can be considered as a modified ΛCDM one, is characterized by a set of parameters which may be constrained
by the astrophysical observations available up to date. 相似文献
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Astrophysical and cosmochemical data show that many kinds of hydrocarbons are widespread in space, including giant molecular clouds, diffuse interstellar medium, comets, interplanetary dust particles, and carbonaceous meteorites. Here an effort is made to show the close relation between high-molecular weight hydrocarbons observed in space and existing on Earth. Results of astrochemical modelling of dust grains in dense collapsing cores of giant molecular clouds are also presented. They show that about 10% of the total abundance of dust grains may be the result of aliphatic hydrocarbons. This dust serves as initial material for comets, formed in protosolar nebula. The problem of survival of cometary organics during impact onto the Earth is discussed, and it is shown that the so-called soft-landing comet hypothesis may explain the accumulation of complex hydrocarbons on the Earth's surface. We conclude that a significant fraction of terrestrial prebiotic petroleum was delivered by extraterrestrial matter. 相似文献
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Dieter Heymann Franco Cataldo Mark h. Thiemens Roelof Fokkens Nico m. m. Nibbering Ronald d. Vis 《Meteoritics & planetary science》2000,35(2):355-361
Abstract— Toluene extracts from two (CSn)x photopolymers were examined with high‐performance liquid chromatography (HPLC), matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectrometry, particle‐induced x‐ray emission (PIXE), and 12C(d,p)13C nuclear microprobing. the extracts contained elemental s and at least from 17 to 20 distinct cmsn compounds with m/z less than ～500 amu. Whereas H2S is the dominant S‐bearing compound of the normal jovian atmosphere, elemental S, CS, and CS2 were observed at Shoemaker‐Levy 9 cometary impact sites and at altitudes of the transiently disturbed jovian atmosphere where photodissociation and photopolymerization occur. It is uncertain whether the CS2 molecular densities were sufficiently large for both to occur, but photopolymerization could have occurred during larger impacts of Jupiter's history. Because the known stable CmSn compounds are yellow, orange and deep red, they could contribute significantly to the colors of the jovian clouds. 相似文献
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In this article we investigate and develop specific aspects of Friedmann-Robertson-Walker (FRW) scalar field cosmologies related to the interpretation that canonical and phantom scalar field sources may be interpreted as cosmological configurations with a mixture of two interacting barotropic perfect fluids: a matter component ρ 1(t) with a stiff equation of state (p 1=ρ 1), and an “effective vacuum energy” ρ 2(t) with a cosmological constant equation of state (p 2=?ρ 2). An important characteristic of this alternative equivalent formulation in the framework of interacting cosmologies is that it gives, by choosing a suitable form of the interacting term Q, an approach for obtaining exact and numerical solutions. The choice of Q merely determines a specific scalar field with its potential, thus allowing to generate closed, open and flat FRW scalar field cosmologies. 相似文献
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Following the increase in seismic activity which occurred near Isernia (Molise, Central Italy) in January 1986, a digital seismic network of four stations with three-component, short-period seismometers, was installed in the area by the Osservatorio Vesuviano. The temporary network had an average station spacing of about 8–10 km and, in combination with permanent local seismic stations, allowed the accurate determination of earthquake locations during an operating period of about one month. Among the 1517 detected earthquakes, 170 events were selected with standard errors on epicentre and depth not greater than respectively 0.5 and 1.5 km. The most frequent focal depths ranged between 4 and 8 km, while the epicentres distribution covered a small area NE of Isernia of about 10 km2. A main rupture zone could not be clearly identified from the spatial distribution of the earthquakes, suggesting a rupture mechanism involving heterogeneous materials. The activity was characterized by low energy levels, the largest earthquake, on January 18, 1986, havingM
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=4.0. The time sequence of events and pattern of seismic energy release revealed a strong temporal clustering of events, similar to the behaviour commonly associated with seismic swarms. 相似文献