| 1. |
- Castro-Tirado, A. J., et al.
(författare)
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GRB 030227 : The first multiwavelength afterglow of an INTEGRAL GRB
- 2003
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 411:1, s. 315-319
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Tidskriftsartikel (refereegranskat)abstract
- We present multiwavelength observations of a gamma-ray burst detected byINTEGRAL (GRB 030227) between 5.3 hours and ~ 1.7days after the event. Here we report the discovery of a dim opticalafterglow (OA) that would not have been detected by many previoussearches due to its faintess (R ~ 23). This OA was seen to declinefollowing a power law decay with index alpha R = -0.95 +/-0.16. The spectral index beta_ opt/NIR yielded -1.25 +/- 0.14. Thesevalues may be explained by a relativistic expansion of a fireball (withp = 2.0) in the cooling regime. We also find evidence for inverseCompton scattering in X-rays.Based on observations with INTEGRAL, an ESA project with instruments andscience data centre funded by ESA member states (especially the PIcountries: Denmark, France, Germany, Italy, Switzerland, Spain), CzechRepublic and Poland, and with the participation of Russia and the USA.Also partially based on observations collected by the Gamma-Ray BurstCollaboration at ESO (GRACE) at the European Southern Observatory, Chile(ESO Large Programme 165.H-0464).
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| 2. |
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| 3. |
- Fateh-Alavi, K., et al.
(författare)
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The effect of stabilizer concentration on the air-plasma-induced surface oxidation of crosslinked polydimethylsiloxane
- 2002
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Ingår i: Polymer degradation and stability. - 0141-3910 .- 1873-2321. ; 78:1, s. 17-25
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Tidskriftsartikel (refereegranskat)abstract
- The concentrations of three stabilizers-a hindered phenol (Irganox 1076), a hindered amine light stabilizer (Tinuvin 770) and a bifunctional stabilizer with chain-breaking hindered phenol and secondary amine and hydroperoxide-decomposing sulphide moieties (Irganox 565)-in crosslinked polydimethylsiloxane were varied using swelling solutions of the stabilizers at different concentrations. The concentration of the stabilizer in the rubber was assessed by UV-Vis spectroscopy of Soxhlet and microwave assisted extracts. Irganox 1076 and Tinuvin 770 were soluble in polydimethylsiloxane to at least 0.2-0.3 wt.%, whereas the solubility of Irganox 565 was considerably lower. The samples were exposed to GHz air plasma and the surface structures of the exposed samples were studied by X-ray photoelectron spectroscopy, and by optical and scanning electron microscopy after uniaxial stretching. The plasma exposure time required for the formation of an oxidised glassy layer increased in a linear fashion with increasing stabilizer concentration, suggesting that the consumption rate was constant in time during the plasma exposure. Tinuvin 770 showed the strongest overall protecting effect whereas Irganox 565 showed the strongest protecting effect per mass fraction of stabilizer. Irganox 1076 was of moderate efficiency. The results suggest that efficient protection towards air plasma is achieved with hindered amine stabilizers or with stabilizers combining chain-breaking and hydroperoxide-decomposing functions. Differential scanning calorimetry showed that Tinuvin 770 and Irganox 565 protected polydimethylsiloxane against thermal oxidation at elevated temperatures. The chemical consumption of these stabilizers followed basically the classical scheme with zero-order kinetics and a rate constant obeying the Arrhenius law.
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| 4. |
- Monteverde, M, et al.
(författare)
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Fluorinated Hg-1223 under pressure : the ultimate Tc of the cuprates?
- 2004
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Ingår i: Physica. C, Superconductivity. - : Elsevier B.V. - 0921-4534 .- 1873-2143. ; 408-410, s. 23-24
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Tidskriftsartikel (refereegranskat)abstract
- High pressure experiments have revealed that Tc is affected by two main pressure-dependent parameters: the doping level of the CuO2 planes and by an intrinsic factor. The origin of the intrinsic factor is still unclear as, depending on the experiment, it is associated with the reduction of the c or the a lattice parameters. F incorporation into the Hg-1223 structure yields an enhancement of Tc up to a susceptibility onset of 138 K, mainly related to a compression of the a crystallographic axis. We have obtained a new high Tc record (166 K ± 1.5 K) by applying pressure (23 GPa) in the fluorinated Hg-1223 superconductor optimally doped. Tc increases with increasing pressure, reaching different maximum values, depending on the F doping level, and decreases for a further increase of pressure. This saturation of Tc may be the highest Tc that can be obtained for the cuprates, considering the particular structural characteristics of this system.
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| 5. |
- Núñez, Eugenia, et al.
(författare)
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Crystal structure, melting behaviour and equilibrium melting point of star polyesters with crystallisable poly(ε–caprolactone) arms
- 2004
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 45:15, s. 5251-5263
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Tidskriftsartikel (refereegranskat)abstract
- Star polymers consisting of poly(ε-caprolactone), PCL, attached to third generation dendrimer, hyperbranched and dendron cores have been studied by differential scanning calorimetry and wide-angle X-ray scattering. The degree of polymerisation of the PCL arms of the star polymers ranged from 14 to 81. The crystal unit cell was the same for the star polymers as for their linear PCL analogues. The star polymers showed a lower degree of crystallinity than the linear PCL, suggesting that the dendritic cores imposed restriction on PCL crystallisation. Slow heating of rapidly cooled samples led to crystal rearrangement - a gradual increase in melting point with decreasing heating rate and recrystallisation followed by additional high temperature melting. The tendency for crystal rearrangement was less pronounced in star polymers based on dendrimer or hyperbranched cores, suggesting that the dendritic cores constitute an obstacle to crystal rearrangement. The star polymers showed higher equilibrium melting points than the linear PCL analogues. It is suggested that covalent attachment of the PCL arms to the dendritic core reduced the positional freedom and the entropy of the melt with respect to that of linear PCL.
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