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  • 1
    ISSN: 1434-601X
    Keywords: 25.85.Ge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Isomeric yield ratios of 30 fission products in 24 MeV proton-induced fission of238U were measured by the use of the ion-guide isotope separator on-line. The obtained isomeric yield ratios were converted to the angular momenta of primary fission fragments based on the statistical model. The deduced angular momenta were examined from various aspects. It is found that in general the angular momentum continuously increases with the fragment mass number including the region of symmetric mass division. However, there are some exceptions. For Sn isotopes the deduced angular momenta are quite small due to the spherical shape of the nuclear shell configuration. It is also concluded from the consideration of the charge distribution that the angular momentum of fission product scatters considerably within the narrow range of mass division. The dependence of the angular momentum on the available energy of fragments at scission point indicates that the individual fragment possesses a characteristic deformation at scission and/or the deduced angular momentum is seriously affected by the particle excitation after scission.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1433-0350
    Keywords: Ependymoma ; Ependymoblastoma ; Infancy ; First year of life
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract During 1987, 23 survey forms for ependymoma cases diagnosed in the 1st year of life were selected from 88 neurosurgical institutes in Japan in collaboration with the International Society for Pediatric Neurosurgery. There were no specific perinatal episodes. The most common clinical manifestations were symptoms of intracranial hypertension and hydrocephalus. Two of seven children with infratentorial ependymomas were alive, and all of the children with such supratentorial tumors were still alive. Of those with ependymoma, three of four in the total extirpation group, and three of seven in the subtotal or partial removal group were alive. The 1-year survival rate was 54% for ependymoma and 58.3% for ependymoblastoma. For 36% of the cases with ependymoma and 14.6% with ependymoblastoma, a 2-year survival rate was observed. Since the prognosis of these tumors is poor, they should be extirpated as often as possible. Collins' law held true in approximately half of the cases.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Human evolution 6 (1991), S. 201-212 
    ISSN: 1824-310X
    Keywords: Primate evolution ; selection pressure ; social interaction ; active selection ; brain and neocortex ; morphological character
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Selection pressures in the evolution of morphological characters which are exclusive to primates were discussed. While the evolutionary change in some morphological characters of primates can be explained by natural or sexual selection, there are also morphological characters of primates, such as some regions of neocortices, which are involved in social interactions and whose evolutionary changes can hardly be explained by natural or sexual selection alone. Furthermore, recent studies have demonstrated that relative sizes of brain, neocortex and some thalamic nuclei of brains differ significantly by social structure in primates. Based on these and other findings, we propose here that “active” selection pressures may have favored a variety of morphological characters related to social interactions, the selection pressures which are derived from social interactions and are operative within animals or troops. The introduction of concept of active selection will be useful in developing conceptual frameworks for understanding of the mechanism of evolution of primates, in particular, of hominids.
    Type of Medium: Electronic Resource
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