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Träfflista för sökning "WFRF:(Wagner L) srt2:(1990-1994)"

Sökning: WFRF:(Wagner L) > (1990-1994)

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1.
  • Penston, M. V., et al. (författare)
  • The extended narrow line region of NGC 4151. I. Emission line ratios and their implications
  • 1990
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 236:1, s. 53-6262
  • Tidskriftsartikel (refereegranskat)abstract
    • The paper presents the first results from long-slit spectra of the Seyfert galaxy NGC 4151 which give average diagnostic ratios of weak lines in the extended narrow line region (ENLR) of that galaxy and the first direct density measurement in an ENLR. These data confirm that the ENLR is kinematically undisturbed gas in the disc of the galaxy which is illuminated by an ionizing continuum stronger by a factor of 13 than a power law interpolated between observed ultraviolet and X-ray fluxes. Explanations of this apparent excess include a hot thermal continuum, time variations and an anisotropic radiation field. The authors give reasons for favouring anisotropy which might be caused by shadowing by a thick accretion disc or by relativistic beaming. Shadowing by a molecular torus is unlikely, given the absence of an infrared signal from the reradiated flux absorbed by any torus. Anisotropy would have important implications for the bolometric luminosity and nature of active galactic nuclei
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2.
  • van Biesen, T, et al. (författare)
  • Structural and functional analyses of the FinP antisense RNA regulatory system of the F conjugative plasmid
  • 1993
  • Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 10:1, s. 35-43
  • Tidskriftsartikel (refereegranskat)abstract
    • The efficiency of conjugation of F-like plasmids is regulated by the FinOP fertility inhibition system. The transfer (tra) operon is under the direct control of the TraJ transcriptional activator which, in turn, is negatively regulated by FinP, an antisense RNA, and FinO, a 22 kDa protein. Recently, FinO has been shown to extend the chemical stability of FinP in vivo in the absence of traJ mRNA. The in vitro secondary structures of both the FinP and TraJ RNAs were determined by the use of single- and double-strand-specific nucleases; both RNAs were found to have double stem-loop structures that are complementary to each other and, therefore, FinP RNA and TraJ RNA have the potential to form a duplex with each other. This was verified by in vitro binding experiments. The reaction was shown to be biomolecular with an apparent rate constant (kapp) of 5 x 10(5)M-1s-1, a value that is similar to those found for other natural antisense RNA systems. Preliminary evidence for the in vivo formation of the FinP-TraJ RNA duplex was obtained by primer extension of the traJ mRNA; the presence of both FinO and FinP was required to cause a dramatic reduction in the steady-state level of traJ mRNA, perhaps as a result of RNase III degradation of the resulting RNA duplex.
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