| 1. |
- Edelson, R. A., et al.
(författare)
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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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| 3. |
- Aleksandrovskii, A. N., et al.
(författare)
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Negative thermal expansion of fullerite C60 at helium temperatures
- 1997
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 23:11, s. 943-946
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Tidskriftsartikel (refereegranskat)abstract
- The thermal expansion of fullerite C60 has been measured in the temperature range 2–9 K. A compacted fullerite sample with a diameter of about 6 mm and height of 2.4 mm was used. It was found that at temperatures below ~ 3.4 K the linear thermal expansion coefficient becomes negative. At temperatures above 5 K our results are in good agreement with the available literature data. A qualitative explanation of the results is proposed
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| 5. |
- Istomin, Sergey Ya., et al.
(författare)
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A new superconducting sulfide—'EuNb2S5'
- 1998
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Ingår i: Physica. C, Superconductivity. - : Elsewier. - 0921-4534 .- 1873-2143. ; 300, s. 67-70
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Tidskriftsartikel (refereegranskat)abstract
- A new low-temperature superconducting (Tc≈3 K) niobium sulfide ‘EuNb2S5' with a hexagonal structure (a=3.3556(8) Å, c=23.440(9) Å) was synthesized from a mixture of EuS, Nb(m) and S in evacuated and sealed silica tubes, heated at 1100°C for 48 h. This superconductor was characterized by EDX analysis, X-ray powder and electron diffraction studies. Electron diffraction revealed the presence of a supercell: asuper=bsuper=√7×a.
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| 9. |
- Kozlov, Alexander, et al.
(författare)
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impulse suppression of chaotic oscillations
- 1996
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Ingår i: Nonlinear dynamics. - 0924-090X .- 1573-269X. ; 1, s. 113-120
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Tidskriftsartikel (refereegranskat)abstract
- The methods of nonconstant feedback impulse control of chaos are introduced. the approach is based on the similarity of the return of the dissipative continuoustime systems with one dimensional maps. The metods are illustrated for the chua´s circuit Rössler oscillator, and phase-locked loop system.
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| 10. |
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