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  • 1990-1994  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Have stellar and supernovae radiations altered the pristine nature of comets? (1990)
    Springer
    Earth, moon and planets 49 (1990), S. 239-245 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Effect of stellar and supernova radiations on cometary nuclei in the Oort cloud is investigated. Radiation dose received by a comet is calculated and compared with the one which Halley's comet receives by one perihelion passage. Stellar radiation provides 10 to 50% of Halley unit over 4 billion years. Inclusion of sublimation of volatile molecules such as CO or N2 does not allow the temperature to rise to 30 K by irradiation of bright OB stars, contrary to the claim of Stern and Shull. A chance encounter with a SN provides radiation dose which is just sufficient to raise to 30 K the surface layer which is 1 m thick on the assumption that the radiation is wholly communicated to the interior. Thus, the comets remain pristine under the effect of stellar and SN radiations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00055177
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Maximum non-gravitational acceleration due to out-gassing cometary nuclei (1991)
    Springer
    Earth, moon and planets 52 (1991), S. 87-92 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Maximum possible acceleration due to out-gassing from cometary nuclei is calculated for H2O and CO(N2) molecules. It is found that the maximum excess velocity at great distance is 0.18 km s−1 so that excess velocities less than this value are compatible with the non-gravitational acceleration due to non-symmetric out-gassing. On the other hand, Comet 1975q and comet 1955V have excess velocities 0.81 and 0.80 km s−1 respectively. These comets may be regarded as the candidates for possible interstellar comets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00113834
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Periodicity and decay of craters over the past 600 myr (1992)
    Springer
    Earth, moon and planets 58 (1992), S. 57-63 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The data set of Grieve which provides diameters and ages of craters is analyzed to obtain periodicity of the formation rate and decay constant of craters. It is confirmed that large craters (D ⩾ 10 km) do not exhibit any periodicity while small ones appear to satisfy the Broadbent criterion for quantum (periodicity) hypothesis at P ≃ 29.5 myr. The result is consistent with a recent study of Bailey who showed that large craters are largely due to asteroids. Allowing for the decay of craters, an excess of 4 small craters within the nearest past is detected. In this sense, one may argue that the solar system is now in a moderate comet shower.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00058073
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Are periodicities in crater formations and mass (1994)
    Springer
    Earth, moon and planets 64 (1994), S. 207-216 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Periodicities in crater formation rate and mass-extinctions are reviewed. The former exhibits a period of 30 million yr, while the latter appear to have a periodicity at 26 myr. Results obtained earlier that small craters better satisfy the adopted criterion for statistical testing is shown due to the fact that there is a strong clustering of small craters in a recent past (〈10 myr). On the basis of the dataset of craters compiled by Grieve, it is shown that there are several craters for which no mass extinctions correspond. The difference in the periods of the craters and of mass extinctions and the lack of mass extinctions that correspond to large craters appear to suggest that the two periodicities are not interrelated, and large impacts merely act as triggers for the mass-extinctions; the only exception being theK/T boundary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00572148
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    On the possible hazard on the major cities caused by asteroid impact in the Pacific ocean (1994)
    Springer
    Earth, moon and planets 65 (1994), S. 7-13 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Semi-quantitative investigation is made of hazard expected from an asteroidal impact in the Pacific. An impact ofd (diameter) = 200 m asteroid has a probability of hitting somewhere in the Pacific once in 15000 y. By carrying out a Monte Carlo simulation, such an impact, on average, is shown to create a tsunami as high as 16, 14, 15, and 21 m at Japan, Taiwan, Shanghai and Hawaii, respectively. Wooden houses, stone and brick houses, and reinforced concrete buildings are likely to be demolished by tsunamis of height 2, 7 and 20 m respectively. Thus, there is a probability of 1% or so that most of the artificial constructions on the coast lines of the Pacific be destroyed in the next century by an asteroidal impact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00572195
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    The ultraviolet spectra of carbonaceous chondrites (1992)
    Springer
    Celestial mechanics and dynamical astronomy 54 (1992), S. 229-231 
    Details
    ISSN: 1572-9478
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00049554
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Organic models of interstellar grains (1992)
    Springer
    Celestial mechanics and dynamical astronomy 54 (1992), S. 275-277 
    Details
    ISSN: 1572-9478
    Keywords: Interstellar grains ; organic material
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A number of experimental studies have been carried out to verify the claim that interstellar grains largely consist of organic material, including biological cells. Our spectroscopic studies on biological cells and organic extracts from carbonaceous compounds have failed to identify the well-known 2200 Å interstellar extinction peak with the organic material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00049564
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Similarity between the structure and stability of isothermal and polytropic gas spheres (1992)
    Springer
    Astrophysics and space science 193 (1992), S. 173-183 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract As shown by Chiéze, polytropic gas spheres imbedded in an ambient medium with a given pressure exhibit a relation between the mass and radius similar to isothermal gas spheres, providedn(polytropic index)〉3 or 〈−1. Here, further investigation is made of the polytropic spheres. Not only the relation between radius and external pressure, but the relation between the central density (ρ c ) and the mass (M) is similar to isothermal spheres and neutron star models. Dynamical calculation shows that the stability of polytropic spheres is lost at the configuration which corresponds to the first peak in the ρ c —M relation, as is the case for neutron star models in general relativity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00643199
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    The ultraviolet spectra of thin evaporated films of carbonaceous chondrite (1993)
    Springer
    Astrophysics and space science 206 (1993), S. 111-117 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Absorption spectra in the visible to the near ultraviolet were measured on the Belgica chondrite B-7904 in a form of thin solid film made by the vacuum evaporation. The spectra obtained exhibit a sharp peak at 226 nm and a broad bump around 280nm. These features were found arising from the meteorite component FeS (troilite). The peak at 226 nm shows a doublet structure with the band-width considerably narrower than the 217.5 nm feature in the interstellar extinction. The absorption spectra obtained previously with the pulverized chondrites suspended in a liquid were also found reproducible by the pulverized FeS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658387
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    The ultraviolet extinction by hollow spherical particles of graphite (1991)
    Springer
    Astrophysics and space science 182 (1991), S. 75-80 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the discrete dipole approximation, we have calculated the extinction efficiency of hollow spherical particles of graphite as a possible constituent of interstellar grains. The particles had a shell structure with the basal plane perpendicular to the radius. The calculations were made on the particles having the outer radiusR 0=10 and 5nm in the wave number region from 0.8 to 8.0 μm−1 using the anisotropic optical constants. It was found that the hollow particles with the inner radiusR 1≅0.65R 0 yield an extinction feature at 4.6 μm−1, which fits fairly well to one observed in the interstellar extinction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00646442
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    Paper (German National Licenses)
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