| 1. |
- Edelson, R. A., et al.
(författare)
-
Multiwavelength observations of short-timescale variability in NGC 4151. IV. Analysis of multiwavelength continuum variability
- 1996
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 364-377377
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Tidskriftsartikel (refereegranskat)abstract
- 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)
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| 2. |
- Dunham, I, et al.
(författare)
-
The DNA sequence of human chromosome 22
- 1999
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 402:6761, s. 489-495
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Crenshaw, D. M., et al.
(författare)
-
Multiwavelength observations of short-timescale variability in NGC 4151. I. Ultraviolet observations
- 1996
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 322-335335
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 4. |
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| 5. |
- Clark, R M, et al.
(författare)
-
Relative deformations of superdeformed bands in Ce-131,Ce-132
- 1996
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 76:19, s. 3510-3513
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Tidskriftsartikel (refereegranskat)abstract
- The quadrupole moments Q(0) of five superdeformed bands in Ce-131,Ce-132 have been established using the Doppler-shift attenuation method; for the first time, we can compare relative deformations of yrast and excited bands in different nuclei to an accuracy of similar or equal to(5-7)%. Four of the five bands have very similar deformations, while the excited band in Ce-131 has a somewhat larger quadrupole moment. Important new information is presented on the shape-driving force of the vi(13/2) orbital, the stability of the second minimum with respect to particle excitations, the relative deformations of identical bands, the nature of the sidefeeding, and the time scale of the decay process.
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| 6. |
- Joss, D T, et al.
(författare)
-
Lifetime measurements of a triaxial band in Ce-133
- 1998
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Ingår i: Acta Physica Hungarica A. - 1219-7580 .- 1588-2675. ; 7:1, s. 111-112
-
Tidskriftsartikel (refereegranskat)abstract
- The Doppler shift attenuation method has been used to determine the transition quadrupole moment of a triaxial band belonging to the gamma-soft nucleus, Ce-133. Doppler broadened lineshape (DBLS) analysis has revealed the magnitude of the Q(t) value to be similar to 2.4 eb. This contribution provides new information of (i) the transition quadrupole moment of this band (ii) the lifetimes of in-band and sidefeeding transitions and (iii) the relative deformations of coexisting nuclear shapes.
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| 7. |
- Joss, D T, et al.
(författare)
-
Lifetime measurements of a triaxial band in Ce-133
- 1998
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 58:6, s. 3219-3222
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Tidskriftsartikel (refereegranskat)abstract
- Lifetimes of states within a triaxial band belonging to;the gamma-soft nucleus Ce-133 have been determined through a Doppler-broadened line shape analysis. A value, Q(t)approximate to 2.2 eb, has been found for the transition quadrupole moment which is considerably smaller than that of superdeformed structures (Q(t)approximate to 7.4 e b) in this mass region. The results are discussed in terms of deformation self-consistent calculations based on the total Routhian surface formalism. [S0556-2813(98)01912-8].
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| 8. |
- Simon, M P, et al.
(författare)
-
Deregulation of the platelet-derived growth factor B-chain gene via fusion with collagen gene COL1A1 in dermatofibrosarcoma protuberans and giant-cell fibroblastoma.
- 1997
-
Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 15:1, s. 95-8
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Tidskriftsartikel (refereegranskat)abstract
- Dermatofibrosarcoma protuberans (DP), an infiltrative skin tumour of intermediate malignancy, presents specific features such as reciprocal translocations t(17;22)(q22;q13) and supernumerary ring chromosomes derived from the t(17;22). In this report, the breakpoints from translocations and rings in DP and its juvenile form, giant cell fibroblastoma (GCF), were characterised on the genomic and RNA level. These rearrangements fuse the platelet-derived growth factor B-chain (PDGFB, c-sis proto-oncogene) and the collagen type I alpha 1 (COL1A1) genes. PDGFB has transforming activity and is a potent mitogen for a number of cell types, but its role in oncogenic processes is not fully understood. COL1A1 is a major constituent of the connective tissue matrix. Neither PDGFB nor COL1A1 have so far been implicated in any tumour translocations. These gene fusions delete exon 1 of PDGFB, and release this growth factor from its normal regulation.
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| 9. |
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| 10. |
- ERKENS, U, et al.
(författare)
-
MONITORING OF ACTIVE GALACTIC NUCLEI .6. THE QUASAR MKN-876
- 1995
-
Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 296:1, s. 90-98
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We present the results of a 6 month monitoring campaign of Mkn 876, a low luminosity quasar with M(abs) approximate to -24. High resolution spectroscopy and direct imaging in the Johnson filters B, V, R, I was carried out in the first half of 1990. Line a
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