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  • 1
    ISSN: 1434-601X
    Schlagwort(e): 21.60 ; 23.20 ; 27.90 ; 29.30
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The Coulomb excitation measurements for the230Th nucleus with32S,84Kr and142Nd projectiles are presented. The use of different projectiles allowed us to get information in the ground-state band and side bands. The energy spectrum of the ground-state band and of the lowest negative-parity band have been investigated up to the spin valueI=24+ andI=19−(21), respectively. Five side bands (K π=0+, 2 1 + , 2 2 + , 1−, 2−) were observed also. The branching ratios for a large number of transitions in the spin regionI≦10 for π=+1 andI≦9 for π=− 1 are analysed. The full set of experimental data contains information on the mixing of the adiabatic states and on the nuclear response to the electromagnetic field ofγ-radiation. It is shown that the experimental data may be explained taking into account the coupling of the ground-β- and twoγ-bands and also of theK π=0−, 1− and 2− negative-parity bands. An enhancement of the transitions from theγ-to theβ-band in respect to the transitions from theγ to the ground band and from theβ- to the ground band is reported. The mixing of the negative-parity bands is found to be typical for the alignment of the octupole-vibrational angular momentum. The strong spin dependence of the intrinsic matrix elements of the electric-dipole operator follows from the branching ratios of inter- and intra-band transitions from theK π=0− states.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1573-5117
    Schlagwort(e): Echinodermata ; ophiuroidea ; reproduction ; gonad index ; carbon and nitrogen production
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Ophiothrix fragilis forms dense aggregations (up to 2000 individuals. m-2) and represents more than 60% of the biomass on the pebbles of the sessile epifauna community in the Dover Strait (eastern English Channel). This population shows a relative stability (in terms of density and magnitude of benthic recruitment) which contrasts with the variability of influx and of local hydrodynamical conditions. Gonadal change was studied in the Dover Strait during 1995 and 1996 and for another population offshore Roscoff (western English Channel) in 1996. Gonadal growth appeared to be cyclical, with higher gonad indices in June and July and a resting phase between September and February for the population of the English Channel. This change showed little inter-annual variability for the population of the Dover Strait, but a high spatial variability between populations of the English Channel. The population offshore Roscoff had lower gonad indices; this difference could be linked to lower temperature and lower food availability (phytoplanktonic production). However, whatever the gonadal growth pattern was, the main spawning of July was synchronous for females and males in both areas. Carbon and nitrogen production towards the pelagic system during the spawning period was very important (up to 20 g C. m-2 and 5 g N. m-2) and was up to 16% and 13% of the annual carbon and nitrogen production of the population in the Dover Strait. After the spawning period, larvae are brought under strong hydrodynamic conditions during ca. four weeks before metamorphosis and settlement. This is probably the most important period for the understanding of the stability of the population.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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