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Träfflista för sökning "WFRF:(Peterson G.) srt2:(1995-1999)"

Sökning: WFRF:(Peterson G.) > (1995-1999)

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1.
  • Crenshaw, D. M., et al. (författare)
  • Multiwavelength observations of short-timescale variability in NGC 4151. I. Ultraviolet observations
  • 1996
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 470:1, s. 322-335335
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Presents the results of an intensive ultraviolet monitoring campaign on the Seyfert 1 galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously with the International Ultraviolet Explorer for 9.3 days, yielding a pair of LWP and SWP spectra every ~70 minutes, and during 4 hr periods for 4 days prior to and 5 days after the continuous-monitoring period. The sampling frequency of the observations is an order of magnitude higher than that of any previous UV monitoring campaign on a Seyfert galaxy. The continuum fluxes in bands from 1275 to 2688 Aring went through four significant and well-defined ldquoeventsrdquo of duration 2-3 days during the continuous-monitoring period. The authors find that the amplitudes of the continuum variations decrease with increasing wavelength, which extends a general trend for this and other Seyfert galaxies to smaller timescales (i.e., a few days). The continuum variations in all the UV bands are simultaneous to within an accuracy of ~0.15 days, providing a strict constraint on continuum models. The emission-line light curves show only one major event during the continuous monitoring (a slow rise followed by a shallow dip) and do not correlate well with continuum light curves over the short duration of the campaign, because the timescale for continuum variations is apparently smaller than the response times of the emission lines</p>
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2.
  • Edelson, R. A., et al. (författare)
  • Multiwavelength observations of short-timescale variability in NGC 4151. IV. Analysis of multiwavelength continuum variability
  • 1996
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 470:1, s. 364-377377
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>For pt.III see ibid., vol.470, no.1, p.349-63 (1996). Combines data from the three preceding papers in order to analyze the multi wave-band variability and spectral energy distribution of the Seyfert 1 galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in medium-energy (~1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA=6%) variations (uncorrelated with those at lower energies) were seen at soft gamma-ray energies of ~100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime, the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 Aring. These data do not probe extreme ultraviolet (1200 Aring to 0.1 keV) or hard X-ray (250 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of lsim0.15 day between 1275 Aring and the other ultraviolet bands, lsim0.3 day between 1275 Aring and 1.5 keV, and lsim1 day between 1275 and 5125 Aring. These tight limits represent more than an order of magnitude improvement over those determined in previous multi-wave-band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (ales-2.5)</p>
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5.
  • Chulkov, L. V., et al. (författare)
  • Large spin alignment of the unbound He-5 fragment after fragmentation of 240 MeV/nucleon He-6
  • 1997
  • Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 79:2, s. 201-204
  • Tidskriftsartikel (refereegranskat)abstract
    • Peripheral fragmentation of a 240 MeV/nucleon beam of the halo nucleus He-6 incident on carbon target has been studied in a kinematically complete experiment. It is found that one-neutron stripping to the unbound nucleus He-5 is the dominant fragmentation mechanism and that it leads to a spin alignment of He-5 in a plane perpendicular to the He-5 momentum vector. This is expected to be a common feature for all neutron halo nuclei.
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  • Karawajczyk, G., et al. (författare)
  • The differential release of eosinophil granule proteins : Studies on patients with acute bacterial and viral infections
  • 1995
  • Ingår i: Clinical and Experimental Allergy. - 0954-7894 .- 1365-2222. ; 25:8, s. 713-719
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>BACKGROUND: Earlier in vitro studies have suggested that the eosinophil may release its granule proteins selectively depending on the stimulus to which the cell is exposed.</p> <p>OBJECTIVE: The object of the present study was to study the question of selective release in vivo by means of serum measurements of the two eosinophil granule proteins eosinophil cationic protein (ECP) and eosinophil peroxidase (EPO) in acute infections.</p> <p>METHODS: Fourty-six subjects with acute infections were studied before treatment, 20 with bacterial infections and 26 with viral infections. Serum ECP, EPO and MPO were measured by specific RIA.</p> <p>RESULTS: In acute bacterial infections ECP, but not EPO, was significantly raised in serum (P &lt; 0.0001) compared with non-infected healthy subjects. In acute bacterial infections ECP was significantly correlated to the levels of the neutrophil marker myeloperoxidase (MPO) (rs = 0.96, P &lt; 0.0001) but not to EPO. In acute viral infections neither ECP nor EPO were on average raised. However, almost 20% the patients had elevated levels of bot proteins. In the viral infections the serum-levels of ECP and EPO were correlated (rs = 0.63, P &lt; 0.001), but no correlation was found with MPO.</p> <p>CONCLUSION: It is concluded that eosinophils are activated during acute bacterial infections and that this activation results in the preferential mobilisation of ECP. The simultaneous assay of the two eosinophil proteins, ECP and EPO, may give new insight into the role of the eosinophil in disease.</p>
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  • Resultat 1-10 av 29
  • [1]23Nästa
 
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