| 1. |
- 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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| 2. |
- Caleman, Carl, et al.
(författare)
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Nanocrystal imaging using intense and ultrashort X-ray pulses
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Annan publikation (populärvet., debatt m.m.)abstract
- Structural studies of biological macromolecules are severely limited by radiation damage. Traditional crystallography curbs the effects of damage by spreading damage over many copies of the molecule of interest in the crystal. X-ray lasers offer an additional opportunity for limiting damage by out-running damage processes with ultrashort and very intense X-ray pulses. Such pulses may allow the imaging of single molecules, clusters or nanoparticles, but coherent flash imaging will also open up new avenues for structural studies on nano- and micro-crystalline substances. This paper addresses the potentials and limitations of nanocrystallography with extremely intense coherent X-ray pulses. We use urea nanocrystals as a model for generic biological substances, and simulate the primary and secondary ionization dynamics in the crystalline sample. The results establish conditions for diffraction experiments as a function of X-ray fluence, pulse duration, and the size of nanocrystals.
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| 3. |
- 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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| 4. |
- Caleman, Carl, et al.
(författare)
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On the Feasibility of Nanocrystal Imaging Using Intense and Ultrashort X-ray Pulses
- 2011
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 5:1, s. 139-146
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Tidskriftsartikel (refereegranskat)abstract
- Structural studies of biological macromolecules are severely limited by radiation damage. Traditional crystallography curbs the effects of damage by spreading damage over many copies of the molecule of interest in the crystal. X-ray lasers offer an additional opportunity for limiting damage by out-running damage processes with ultrashort and very intense X-ray pulses Such pulses may allow the imaging of single molecules, clusters; Or nanoparticles: Coherent flash Imaging Will also open up new avenues for structural studies on nano- and microcrystalline substances. This paper addresses the theoretical potentials and limitations of nanocrystallography with extremely intense coherent X-ray pulses. We use urea nanocrystals as a model for generic biological substances and simulate the primary and secondary ionization dynamics in the crystalline sample. The results establish conditions for ultrafast single shot nanocrystallography diffraction experiments as a function of X-ray fluence, pulse duration, and the size of nanocrystals. Nanocrystallography using ultrafast X-ray pulses has the potential to open up a new route in protein crystallography to solve atomic structures of many systems that remain Inaccessible using conventional X-ray sources.
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| 5. |
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| 6. |
- Hutton, Roger, et al.
(författare)
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Spectral intensities as a function of Hg content and measurement position in fluorescent light tubes
- 2006
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Ingår i: IEEE Conference Record - Abstracts. The 33rd IEEE International Conference on Plasma Science. - 1424401240 ; , s. 242-242
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Konferensbidrag (refereegranskat)abstract
- Summary form only given. Spectra were recorded from a fluorescent light tube under a number of experimental conditions and using different spectroscopic techniques. The motivation of the work was to use spectroscopic techniques for plasma diagnostics purposes. The spectrometers used were a high resolution echelle based instrument and a Fourier transform spectrometer in Lund and a low-resolution instrument in Toulouse. The interest in the low resolution instrument is that it is attached to a temperature controlled bath. The data obtained in Lund was at much higher resolution but not temperature controlled. Spectra were also recorded at a number of positions along the tube. Some of the results can be summarized as follows: (a) spectral lines from ionized Hg decay much faster as a function of temperature than lines from Hg I. This is in some ways unexpected as: (b) the percentage of excited noble gas atoms increases as the lamp temperate, i.e. Hg atom content, goes down, which would appear to indicate that; (c) the electron energy increases as the Hg content (lamp temperature) goes down; (d) From the intensities of noble gas lines as a function of distance from the filament it would appear that the electron temperature is higher close to the filament. One would imagine that the concentration of excited Hg+ would benefit from a higher electron energy distribution or a higher content of excited noble gas atoms (Penning ionization/excitation). Hence one may expect the Hg+ excited concentration to follow that of excited Hg, but such is not the case. Some of the above mentioned conclusions, e.g. (c) and (d) are known in the literature from other experimental studies. The other points are the subject of further studies using a combination of high spectral resolution, controlled temperature and time resolved methods
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| 7. |
- 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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| 8. |
- Price, Patricia E., et al.
(författare)
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Dressing-related pain in patients with chronic wounds : an international patient perspective
- 2008
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Ingår i: International Wound Journal. - 1742-4801 .- 1742-481X. ; 5:2, s. 159-171
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Tidskriftsartikel (refereegranskat)abstract
- This cross-sectional international survey assessed patients' perceptions of their wound pain. A total of 2018 patients (57% female) from 15 different countries with a mean age of 68.6 years (SD = 15.4) participated. The wounds were categorised into ten different types with a mean wound duration of 19.6 months (SD = 51.8). For 2018 patients, 3361 dressings/compression systems were being used, with antimicrobials being reported most frequently (n= 605). Frequency of wound-related pain was reported as 32.2%, 'never' or 'rarely', 31.1%, 'quite often' and 36.6%, 'most' or 'all of the time', with venous and arterial ulcers associated with more frequent pain (P= 0.002). All patients reported that 'the wound itself' was the most painful location (n= 1840). When asked if they experienced dressing-related pain, 286 (14.7%) replied 'most of the time' and 334 (17.2%) reported pain 'all of the time'; venous, mixed and arterial ulcers were associated with more frequent pain at dressing change (P < 0.001). Eight hundred and twelve (40.2%) patients reported that it took <1 hour for the pain to subside after a dressing change, for 449 (22.2%) it took 1-2 hours, for 192 (9.5%) it took 3-5 hours and for 154 (7.6%) patients it took more than 5 hours. Pain intensity was measured using a visual analogue scale (VAS) (0-100) giving a mean score of 44.5 (SD = 30.5, n= 1981). Of the 1141 who reported that they generally took pain relief, 21% indicated that they did not feel it was effective. Patients were asked to rate six symptoms associated with living with a chronic wound; 'pain' was given the highest mean score of 3.1 (n= 1898). In terms of different types of daily activities, 'overdoing things' was associated with the highest mean score (mean = 2.6, n= 1916). During the stages of the dressing change procedure; 'touching/handling the wound' was given the highest mean score of 2.9, followed by cleansing and dressing removal (n= 1944). One thousand four hundred and eighty-five (80.15%) patients responded that they liked to be actively involved in their dressing changes, 1141 (58.15%) responded that they were concerned about the long-term side-effects of medication, 790 (40.3%) of patient indicated that the pain at dressing change was the worst part of living with a wound. This study adds substantially to our knowledge of how patients experience wound pain and gives us the opportunity to explore cultural differences in more detail.
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| 9. |
- Price, Patricia E., et al.
(författare)
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Dressing-related pain in patients with chronic wounds : an international patient perspective
- 2008
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Ingår i: International Wound Journal. - : Wiley-Blackwell Publishing Ltd. - 1742-4801 .- 1742-481X. ; 5:2, s. 159-171
-
Tidskriftsartikel (refereegranskat)abstract
- This cross-sectional international survey assessed patients' perceptions of their wound pain. A total of 2018 patients (57% female) from 15 different countries with a mean age of 68.6 years (SD = 15.4) participated. The wounds were categorised into ten different types with a mean wound duration of 19.6 months (SD = 51.8). For 2018 patients, 3361 dressings/compression systems were being used, with antimicrobials being reported most frequently (n= 605). Frequency of wound-related pain was reported as 32.2%, 'never' or 'rarely', 31.1%, 'quite often' and 36.6%, 'most' or 'all of the time', with venous and arterial ulcers associated with more frequent pain (P= 0.002). All patients reported that 'the wound itself' was the most painful location (n= 1840). When asked if they experienced dressing-related pain, 286 (14.7%) replied 'most of the time' and 334 (17.2%) reported pain 'all of the time'; venous, mixed and arterial ulcers were associated with more frequent pain at dressing change (P < 0.001). Eight hundred andtwelve (40.2%) patients reported that it took <1 hour for the pain to subside after a dressing change, for 449 (22.2%) it took 1-2 hours, for 192 (9.5%) it took 3-5 hours and for 154 (7.6%) patients it took more than 5 hours. Pain intensity was measured using a visual analogue scale (VAS) (0-100) giving a mean score of 44.5 (SD = 30.5, n= 1981). Of the 1141 who reported that they generally took pain relief, 21% indicated that they did not feel it was effective. Patients were asked to rate six symptoms associated with living with a chronic wound; 'pain' was given the highest mean score of 3.1 (n= 1898). In terms of different types of daily activities, 'overdoing things' was associated with the highest mean score (mean = 2.6, n= 1916). During the stages of the dressing change procedure; 'touching/handling the wound' was given the highest mean score of 2.9, followed by cleansing and dressing removal (n= 1944). One thousand four hundred and eighty-five (80.15%) patients responded that they liked to be actively involved in their dressing changes, 1141 (58.15%) responded that they were concerned about the long-term side-effects of medication, 790 (40.3%) of patient indicated that the pain at dressing change was the worst part of living with a wound. This study adds substantially to our knowledge of how patients experience wound pain and gives us the opportunity to explore cultural differences in more detail.
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| 10. |
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