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- Ericson, Marica, 1974, et al.
(författare)
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Photodynamic therapy of actinic keratosis at varying fluence rates : Assessment of photobleaching, pain and primary clinical outcome
- 2004
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Ingår i: British Journal of Dermatology. - : Oxford University Press (OUP). - 0007-0963 .- 1365-2133. ; 151, s. 1204-1212
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Tidskriftsartikel (refereegranskat)abstract
- Background: Although photodynamic therapy (PDT) is becoming an important treatment method for skin lesions such as actinic keratosis (AK) and superficial basal cell carcinoma, there are still discussions about which fluence rate and light dose are preferable. Recent studies in rodents have shown that a low fluence rate is preferable due to depletion of oxygen at high fluence rates. However, these results have not yet been verified in humans. Objectives: The objective was to investigate the impact of fluence rate and spectral range on primary treatment outcome and bleaching rate in AK using aminolaevulinic acid PDT. In addition, the pain experienced by the patients has been monitored during treatment. Patients/methods Thirty-seven patients (mean age 71 years) with AK located on the head, neck and upper chest were treated with PDT, randomly allocated to four groups: two groups with narrow filter (580-650 nm) and fluence rates of 30 or 45 mW cm-2, and two groups with broad filter (580-690 nm) and fluence rates of 50 or 75 mW cm-2. The total cumulative light dose was 100 J cm-2 in all treatments. Photobleaching was monitored by fluorescence imaging, and pain experienced by the patients was registered by using a visual analogue scale graded from 0 (no pain) to 10 (unbearable pain). The primary treatment outcome was evaluated at a follow-up visit after 7 weeks. Results: Our data showed a significant correlation between fluence rate and initial treatment outcome, where lower fluence rate resulted in favourable treatment response. Moreover, the photo-bleaching dose (1/e) was found to be related to fluence rate, ranging from 4.5 ± 1.0 J cm -2 at 30 mW cm-2, to 7.3 ± 0.7 J cm-2 at 75 mW cm-2, indicating higher oxygen levels in tissue at lower fluence rates. After a cumulative light dose of 40 J cm-2 no further photobleaching took place, implying that higher doses are excessive. No significant difference in pain experienced by the patients during PDT was observed in varying the fluence rate from 30 to 75 mW cm-2. However, the pain was found to be most intense up to a cumulative light dose of 20 J cm-2. Conclusions: Our results imply that the photobleaching rate and primary treatment outcome are dependent on fluence rate, and that a low fluence rate (30 mW cm-2) seems preferable when performing PDT of AK using noncoherent light sources.
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- Westergren, J., et al.
(författare)
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Cooling efficiency in collisions between Pd 13 and He, Ne, Ar and Kr
- 2003
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Ingår i: European Journal phys.. - : Springer Science and Business Media LLC. ; 22:1, s. 81-97
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Tidskriftsartikel (refereegranskat)abstract
- The cooling of the metal cluster Pd13 in an atmosphere of rare gas has been studied by means of computer simulation. By simulation, the average energy transfer in collisions between one cluster and one gas atom has been obtained. Emphasis has been placed on conditions when the temperatures of the colliding species are almost equal. All modes of motion, inclusive the translation, must be considered in order to obtain vanishing energy transfer at equilibrium. A simulation scheme is presented by which the energy transfer is zero to the cluster when the gas and the cluster temperatures are equal. At equilibrium the energy transfer does however not vanish for all impact parameters. In the collisions with Pd13, the cluster is heated by collisions with a small impact parameter but equally cooled by collisions with a large impact parameter. Argon and krypton are found to cool Pd13 equally efficiently while neon and helium are less efficient cooling agents.
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- Westergren, J., et al.
(författare)
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Melting of palladium clusters—Canonical and microcanonical Monte Carlo simulation
- 2003
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Ingår i: Phys.Chem.Chem.Phys(PCCP). - : Royal Society of Chemistry (RSC). ; 5, s. 136-150
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Tidskriftsartikel (refereegranskat)abstract
- We present Monte Carlo simulations of single palladium clusters of 13, 34, 54, 55, 147 and 309 atoms. The clusters are modeled by a many-body potential and they have been simulated at constant temperature or constant total energy. The caloric curves of the clusters, with the exception of Pd34, exhibit an S-bend at melting which is typical for a finite system. We have also observed the typical coexistence region of solid and molten clusters both in the canonical and the microcanonical ensembles. Pd34, in contrast, melts without an accompanying peak in heat capacity and at melting the atoms become mobile without any significant change in geometric structure. For the larger clusters a free energy barrier inhibits phase switching. In some cases of phase change from molten to solid structure the barrier is of purely entropic character. By a conversion of the results in the microcanonical simulations into temperature-dependent data, the simulations at fixed temperature and fixed total energy have been compared. The agreement is in most cases good. The results are furthermore compared to earlier molecular dynamics simulations with the Nosé–Hoover thermostat. These results are in good agreement with the Monte Carlo simulations as well.
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