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  • 1985-1989  (8)
Source
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Galactic tidal perturbations of long-period comets and the distribution of the inclinations (1989)
    Springer
    Earth, moon and planets 44 (1989), S. 29-37 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Perturbation of the perihelion distance q of long-period comets by the galactic tidal force is calculated using Cowell's method. It is shown that the maximum perturbation is suffered by those with i (inclination) close to 50
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00054331
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A neutron activation analysis of iridium concentration in Yamato carbonaceous chondrite (1988)
    Springer
    Earth, moon and planets 42 (1988), S. 301-302 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Iridium concentration in extra-terrestrial bodies is an important quantity in relation to Ir-rich geological layers. Ir concentration of a Yamato carbonaceous chondrite (Y-793321) has been measured by a neutron activation method. The measurement yields a value (0.57 ± 0.06) Μg per gramme for the chondrite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00058494
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Hypothesis of variable g and the secular accelerations of the Sun and the Moon (1986)
    Springer
    Earth, moon and planets 34 (1986), S. 139-148 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract It is known that the observed secular accelerations of the Sun and Moon are not consistent with the tidal interactions of the Earth with the Sun and Moon. Following Dicke, the hypothesis of variable constant of gravity is adopted and expressions for the accelerations are derived. It is shown that if the theoretical ratio of the acceleration is equated the observed one, a unique value for —ġ/G can be calculated. Adopting the accelerations obtained by Fotheringham, Newton, Muller and Stephenson, and Stephenson, it is found that — ġ/G ranges from 1.4 × 10−11 to 3.3 × 10−11 yr−1. This estimate is consistent with the one based upon the comparison of the lunar accelerations measured with respect to atomic and ephemis times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00055131
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    A thermal modelling of cometary activity with a crystallized water ice nucleus (1987)
    Springer
    Earth, moon and planets 37 (1987), S. 141-146 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Arguments are presented to suggest that surface layers of the nuclei of periodic comets consist of crystallized rather than amorphous water ice and thermal modelling of such nuclei is presented. The rate of sublimation of water from a rotating nucleus is found to be greater than that from a uniformly heated nucleus. When the model is applied to P/Halley, the sublimation rate at perihelion is found to be 8.1 × 1029 mol s−1 for a nucleus rotating with a period of 50 hours and 7.6 × 1029 for a uniformly heated nucleus on the premise that the effective radius of the nucleus is 2.5 km. The total sublimation of water per revolution is 5.38 × 1036 molecules for P/Halley and 3.91 × 1036 molecules per P/Crommelin. The result so obtained is discussed in relation to the observational data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00130889
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Radioactive heating and layered structure of cometary nuclei (1988)
    Springer
    Earth, moon and planets 40 (1988), S. 303-313 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Following the work of Whipple and Stefanik, radioactive heating by uranium, thorium and pottasium of a cometary nucleus is discussed. The assumed composition is that of interstellar medium. If thermal diffusivity is 10−4 cm2s−1, the central temperature of a nucleus with radius 10 km can be above 50 K, while if the thermal diffusivity is 5 × 10−3, the central temperature can be only 25 K or so. Volatile gases such as N2 and CO will flow toward the outer part of the nucleus and are lost in their first several approaches to the sun. This mechanism appears capable of explaining the depletion of N2 and CO relative to the interstellar abundance. It is argued that unfamiliar activity of comet Bowell could be explained by sublimation mainly of N2 and CO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192648
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Photometric and photo accoustic measurement of the absorbance of micro-organisms and its relation to the micro-organism-grain hypothesis (1985)
    Springer
    Astrophysics and space science 117 (1985), S. 401-406 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Absorption ofE. Coli and other micro-organisms are measured by the standard optical spectroscopy and by the photo-accoustic method. The former method does not yield an extinction peak at λ=220 nm but yields a weak one at λ=270 nm, while by the latter method absorption peaks at λ=220 nm and a weaker one at λ=270 nm have been found for the spore of Bacillus subtilis. The well-known amino-acid, triptophan shows absorption peaks at λ=220 and 280 nm. It is tentatively concluded that for the micro-organism model of interstellar grains to be viable, they may have to be spores rather than ordinary cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00650165
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    A spectroscopic study of the microorganism model of interstellar grains (1986)
    Springer
    Astrophysics and space science 124 (1986), S. 377-388 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The microorganism model of interstellar grains is investigated by spectroscopy from the infrared (IR), visible to the ultraviolet (UV) wave regions.E. coli, yeast and spores ofBacillus subtilis exhibit absorption bands at λ=3.1 and 9.7 μm; they also exhibit several absorptions at 6∼8 μm which are in agreement with the observed IS extinction curves. To obtain the extinction curves in the visible and UV regions, dry films of microorganism are prepared on a MgF2 plate or synthesized quartz plate and their spectra measured. In the wavelength region 190∼400 nm, conventional spectrophotometers are adopted for the measurement. The extinction curve of the film ofE. coli is similar to the observed IS curve. For the wave-range 100〈λ〈400 nm, a vacuum UV spectrometer is adopted to avoid absorptions due to O2 in the atmosphere. The extinction spectra by this method are in agreement with the result obtained by the conventional method where comparison is possible. The extinction curves ofE. coli and yeast are such that they incrase towards the short wavelength and exhibit a peak at λ-190 nm, which is different from the well-known IS peak at λ=220 nm. It remains to be seen whether interstellar low temperatures (10∼40 K) can shift the peak position in the extinction curve of biochemical materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656048
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Organic model of interstellar grains (1987)
    Springer
    Astrophysics and space science 132 (1987), S. 409-414 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Extinction efficiency of grains is calculated from the Mie formula on the premise that the grains are of organic composition. The optical constants adopted for the calculations are those ofE. coli, polystyrene and bovine albumin. The grain radiusa is assumed to obey a distribution of the formN(a) ∝a −α and the value of α is chosen so as to make the calculated extinction curve match the observed interstellar extinction curve. Although the calculated curve gives a reasonably good fit to the observed extinction curve for wavelength less than 2100 Å, at longer wavelength region agreement is poor. It is concluded that another component is required for the organic model to be viable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00641771
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    Paper (German National Licenses)
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