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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 52 (1996), S. 888-891 
    ISSN: 1420-9071
    Schlagwort(e): Ageing ; rat ; brain ; gene expression ; differential display
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract We have used the polymerase chain reaction (PCR)-based technique of differential display to analyse changes in gene expression during ageing of the rat brain. In this approach we have compared three young adult (6 months) with three old adult (20 months) animals. RNA preparations from the homogenised brains were subjected to reverse transcriptase (RT)-PCR using 36 different combinations of primer pairs. Any PCR product which was consistently found to be more prominent in the three young brains compared to the three old brains, and vice versa, was scored as potentially representing a gene which was differentially expressed during the ageing of this tissue. Out of a possible 2000+PCR products we identified 44 that might represent genes that exhibit differential expression during ageing of the rat brain. An initial screen of these fragments, by Southern-blotting the PCR products and hybridising them with cDNA probes derived from either young or old brain RNA preparations, indicated that 40% of them represented genes that were differentially expressed. This approach is likely to prove invaluable for identifying cohorts of genes that show differential expression during the ageing process.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 330 (1988), S. 387-395 
    ISSN: 1434-601X
    Schlagwort(e): 24.30.−V
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Broad energy distributions in fast neutron beams have been achieved by appropriate filtering of the236U fission radiation provided from the RENT converter facility at the FRM research reactor. Transmission measurements in such beams result in average cross sections to which resonance reactions and shape elastic scattering contribute. We used a silicon (124.5 cm) filtered beam with a median energy of 143 keV (width 20 keV) and beams with 1.3 MeV (0.55 to 3 MeV) and 2.1 MeV (1 to 5.5 MeV) obtained through different filter combinations of lead and polyethylene. The relative high energies and the broad spectra made it possible to determine experimentally the contributions ofs- andp-wave resonance reactions to the average cross section even for light nuclei. Using the three different beams we determined the average cross sections for the elements in the mass regionA=9 to 65. Analysing the measured cross sections by means of theR matrix formalism provided a complete set ofp-wave strength functions and distant level parameters. Moreover, single particle shell effects in the cross sections were observed. In conclusion we obtained informations on the 2P and the 3S size resonances and about the validity of the optical model for neutron reactions with light nuclei.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Environmental and ecological statistics 6 (1999), S. 183-195 
    ISSN: 1573-3009
    Schlagwort(e): adaptive sampling ; clustered population ; Rao-Blackwell theorem.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Thompson (1990) introduced the adaptive cluster sampling design and developed two unbiased estimators, the modified Horvitz-Thompson (HT) and Hansen-Hurwitz (HH) estimators, for this sampling design and noticed that these estimators are not a function of the minimal sufficient statistics. He applied the Rao-Blackwell theorem to improve them. Despite having smaller variances, these latter estimators have not received attention because a suitable method or algorithm for computing them was not available. In this paper we obtain closed forms of the Rao-Blackwell versions which can easily be computed. We also show that the variance reduction for the HH estimator is greater than that for the HT estimator using Rao-Blackwell versions. When the condition for extra samples is $$y 〉 0$$ , one can expect some Rao-Blackwell improvement in the HH estimator but not in the HT estimator. Two examples are given.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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