| 1. |
- Gaffney, K J, et al.
(författare)
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Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb
- 2005
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 95:12
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Tidskriftsartikel (refereegranskat)abstract
- The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.
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| 2. |
- Cavalieri, A L, et al.
(författare)
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Clocking femtosecond X rays.
- 2005
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Ingår i: Phys Rev Lett. - 0031-9007. ; 94:11
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Tidskriftsartikel (refereegranskat)abstract
- Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.
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| 3. |
- Fritz, D. M., et al.
(författare)
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Ultrafast bond softening in bismuth : Mapping a solid's interatomic potential with X-rays
- 2007
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 315:5812, s. 633-636
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Tidskriftsartikel (refereegranskat)abstract
- Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid.
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| 4. |
- Hillyard, P. B., et al.
(författare)
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Carrier-density-dependent lattice stability in InSb
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 98:12, s. 125501-
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Tidskriftsartikel (refereegranskat)abstract
- The ultrafast decay of the x-ray diffraction intensity following laser excitation of an InSb crystal has been utilized to observe carrier dependent changes in the potential energy surface. For the first time, an abrupt carrier dependent onset for potential energy surface softening and the appearance of accelerated atomic disordering for a very high average carrier density have been observed. Inertial dynamics dominate the early stages of crystal disordering for a wide range of carrier densities between the onset of crystal softening and the appearance of accelerated atomic disordering.
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| 5. |
- Lindenberg, AM, et al.
(författare)
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Atomic-scale visualization of inertial dynamics
- 2005
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 308:5720, s. 392-395
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Tidskriftsartikel (refereegranskat)abstract
- The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.
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| 6. |
- Lindenberg, A. M., et al.
(författare)
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X-ray diffuse scattering measurements of nucleation dynamics at femtosecond resolution.
- 2008
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:13, s. 135502-1-135502-5
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Tidskriftsartikel (refereegranskat)abstract
- Femtosecond time-resolved small and wide angle x-ray diffuse scattering techniques are applied to investigate the ultrafast nucleation processes that occur during the ablation process in semiconducting materials. Following intense optical excitation, a transient liquid state of high compressibility characterized by large-amplitude density fluctuations is observed and the buildup of these fluctuations is measured in real time. Small-angle scattering measurements reveal snapshots of the spontaneous nucleation of nanoscale voids within a metastable liquid and support theoretical predictions of the ablation process.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- van Vollenhoven, R.F., et al.
(författare)
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Addition of infliximab compared with addition of sulfasalazine and hydroxychloroquine to methotrexate in patients with early rheumatoid arthritis (Swefot trial) : 1-year results of a randomised trial
- 2009
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Ingår i: The Lancet. - 0140-6736 .- 1474-547X. ; 374:9688, s. 459-466
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Tidskriftsartikel (refereegranskat)abstract
- Background: New treatment strategies for early rheumatoid arthritis are evolving rapidly. We aimed to compare addition of conventional disease-modifying antirheumatic drugs (sulfasalazine and hydroxychloroquine) with addition of a tumour necrosis factor antagonist (infliximab) to methotrexate in patients with early rheumatoid arthritis. Methods: We undertook a randomised trial in 15 rheumatology units in Sweden. We enrolled patients with early rheumatoid arthritis (symptom duration less than1 year) and administered methotrexate (up to 20 mg per week). After 3-4 months, those who had not achieved low disease activity but who could tolerate methotrexate were randomly allocated by computer addition of either sulfasalazine and hydroxychloroquine or infliximab. Primary outcome was achievement of a good response according to European League Against Rheumatism (EULAR) criteria at 12 months. Patients were followed up to 24 months; here, we present findings at 12 months. Analysis was by intention to treat and we used non-responder imputation. The Swefot (Swedish Pharmacotherapy) study is registered in the WHO database at the Karolinska University Hospital, number CT20080004. Findings: 487 patients were initially enrolled. Of 258 who had not achieved low disease activity with methotrexate, 130 were allocated sulfasalazine and hydroxychloroquine and 128 were assigned infliximab. 32 of 130 (25%) patients allocated sulfasalazine and hydroxychloroquine achieved the primary outcome compared with 50 of 128 (39%) assigned infliximab (risk ratio 1·59 [95% CI 1·10-2·30], p=0·0160). Adverse events were balanced fairly well between the two groups and accorded with known adverse events of the drugs used. No deaths occurred in either group. Interpretation: In patients with early rheumatoid arthritis in whom methotrexate treatment failed, addition of a tumour necrosis factor antagonist to methotrexate monotherapy is clinically superior to addition of conventional disease-modifying antirheumatic drugs. Funding: Swedish Rheumatism Association, Schering-Plough.
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