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41.
Michele Bossi Gianantonio Guerrero Luciano Mantegazza Marco Scardia 《Astrophysics and Space Science》1981,79(2):463-468
Photoelectric observations of the suspected Delta-Scuti star HR 5492 are given. The present data do not show any light variation greater than 0.01 mag. In spite of the very small light variations, the data analysis shows the presence of two periodicities, which are statistically significant. While the longest period (1.
.
d
296) cannot be justified with the present data, the shorter one (0.
.
d
044) is in excellent agreement with the hypothesis of an F4V star that is radially pulsating in the fundamental mode, even if this star is well outside the cold border of the instability strip. 相似文献
42.
Abstract— An oxide layer adjacent to the surface of the Hoba Ni-Fe meteorite was analyzed chemically and mineralogically. Maghemite, magnetite, goethite and lepidocrocite were the main Fe minerals found in the oxide layer surrounding Hoba. Most of the Ni from the unweathered original meteorite was distributed among the above minerals with spinel-type oxides (maghemite and magnetite) having the largest Ni fraction. Some Ni migrated to the limestone in which the meteorite is embedded. No evidence for zaratite or akaganeite was found in the oxide layer. Sulfate derived from the oxidation of troilite precipitated as gypsum. Phosphate accumulation in limestone in contact with the meteorite is probably due to phosphate adsorbed on Fe-oxides. Maghemite with some magnetite was the oxidation product immediately next to the meteorite metal surface, which accommodated most of the Ni and Fe from the meteorite into its structure. Upon oxidation, some of the Ni, which was incorporated into calcite, was released. Cobalt associated with the oxides stayed within the oxide structure regardless of the oxidation state and did not migrate to the limestone. This suggests that Co may be a good tracer for oxides of meteoritic origin. 相似文献
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In the context of current and future microwave surveys mainly dedicated to the accurate mapping of Cosmic Microwave Background (CMB), mm and sub-mm emissions from Solar System will represent a potential source of contamination as well as an opportunity for new Solar System studies. In particular, the forthcoming ESA Planck mission will be able to observe the point-like thermal emission from planets and some large asteroids as well as the diffused Zodiacal Light Emission (ZLE). After a brief introduction to the field, we focus on the identification of Solar System discrete objects in the Planck time ordered data. 相似文献
46.
Isotopic fractionation factors for oxygen and silicon in selected silicates (quartz, enstatite, forsterite, lizardite, kaolinite) are calculated using first-principles methods based on density-functional theory. Good agreement between theory and experiment is found in the case of oxygen. In the case of silicon, agreement and differences with existing estimates of equilibrium fractionation factors are discussed. The relationship between silicon and oxygen fractionation factors, silicate polymerization degree and chemical composition is studied and compared with previous semi-empirical models. 相似文献
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Maria Di Rosa Chiara Frassi Michele Marroni Francesca Meneghini Luca Pandolfi 《地学学报》2020,32(1):34-43
Despite the important role played by the Sardinia‐Corsica block in the reconstruction of the Western Mediterranean geodynamics, the extent of involvement of the “Autochthonous” European margin exposed in Corsica (France) (i.e., Hercynian Corsica) in the Alpine orogeny remains uncertain. Stratigraphic and sedimentological studies in the post‐Variscan deposits on the Hercynian Corsica are scarce and even scarcer are the structural and metamorphic constraints. To face these uncertainties, we present new stratigraphic, structural and metamorphic data from the area of Razzo Bianco, Central Corsica, where a complete sequence belonging to the European continental margin is exposed. Field and structural investigations demonstrate that the sequence represents the easternmost edge of the downgoing European plate. Metamorphic studies on the Eocene deposits indicate that the margin was buried at depth up to blueschist facies conditions and, subsequently, it was progressively exhumed mainly through the activation of oblique top‐to‐the NW shear zones. 相似文献
50.
Johanna Mattila Glen Chaplin Michele R. Eilers Kenneth L. Heck Jr. Jonathan P. O'Neal John F. Valentine 《Journal of Sea Research》1999,41(4):209
Fish, epibenthos and macroinfauna were collected in a Zostera marina bed and nearby unvegetated sediments in the estuary of the Damariscotta River, on the mid-coast of Maine. Samples of epibenthic fauna and fish were collected at low tides both during day and night, and samples of infauna at low tides during the day. The mean density of Zostera shoots in the study area was 335 m−2. Abundance and species number of fish were greater at night than during the day and greater in eelgrass beds (Z. marina) than in unvegetated habitats. Daytime fish collections were dominated by Atlantic silversides (Medinia medinia), while juvenile winter flounder (Pseudopleuronectes americanus) dominated night collections. Also Zostera-associated epifaunal abundances and number of species were significantly higher at night than during the day. Mysis stenolepis, Idotea balthica and Littorina obtusata were dominant species in the epifauna samples. Of the total of 37 invertebrate species encountered, only five occurred both in the infaunal and epifaunal samples. Nineteen different taxa were collected from the benthic core samples. The most abundant invertebrate infaunal taxa were sipunculids, the polychaete Nereis virens, and oligochaetes. Infaunal invertebrate abundances and species diversity were significantly higher in eelgrass beds than in unvegetated sediments. The abundance and number of species of benthic invertebrates were also positively correlated to seagrass biomass. Community diversity values (H′) were relatively low but fit well in the general pattern of decreasing diversity towards northern latitudes. 相似文献