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Sökning: WFRF:(Wahlström Claes Göran)

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  • Genoud, Guillaume, et al. (författare)
  • XUV digital in-line holography using high-order harmonics
  • 2008
  • Ingår i: Applied Physics B. - Springer. - 0946-2171. ; 90:3-4, s. 533-538
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract in Undetermined A step towards a successful implementation of time-resolved digital in-line holography with extreme ultraviolet (XUV) radiation is presented. Ultra-short XUV pulses are produced as high-order harmonics of a femtosecond laser and a Schwarzschild objective is used to focus harmonic radiation at 38 nm and to produce a strongly divergent reference beam for holographic recording. Experimental holograms of thin wires are recorded and the objects reconstructed. Descriptions of the simulation and reconstruction theory and algorithms are also given. Spatial resolution of a few hundreds of nanometers is potentially achievable, and the micrometer resolution range is demonstrated.
  • Svanberg, Sune, et al. (författare)
  • Applications of terawatt lasers
  • 1994
  • Ingår i: LASER SPECTROSCOPY - XITH INTERNATIONAL CONFERENCE. - 0094-243X .- 1551-7616. - 1-56396-262-4 ; :290, s. 264-269
  • Konferensbidrag (refereegranskat)
  • Abdulhadi, Nadia, et al. (författare)
  • Patient-provider interaction from the perspectives of type 2 diabetes patients in Muscat, Oman : a qualitative study
  • 2007
  • Ingår i: BMC Health Services Research. - 1472-6963 .- 1472-6963. ; 7, s. 162
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Patients' expectations and perceptions of the medical encounter and interactions are important tools in diabetes management. Some problems regarding the interaction during encounters may be related to a lack of communication skills on the part of either the physician or the patient. This study aimed at exploring the perceptions of type 2 diabetes patients regarding the medical encounters and quality of interactions with their primary health-care providers. Methods: Four focus group discussions ( two women and two men groups) were conducted among 27 purposively selected patients ( 13 men and 14 women) from six primary health-care centres in Muscat, Oman. Qualitative content analysis was applied. Results: The patients identified some weaknesses regarding the patient-provider communication like: unfriendly welcoming; interrupted consultation privacy; poor attention and eye contact; lack of encouraging the patients to ask questions on the providers' side; and inability to participate in medical dialogue or express concerns on the patients' side. Other barriers and difficulties related to issues of patient-centeredness, organization of diabetes clinics, health education and professional competency regarding diabetes care were also identified. Conclusion: The diabetes patients' experiences with the primary health-care providers showed dissatisfaction with the services. We suggest appropriate training for health-care providers with regard to diabetes care and developing of communication skills with emphasis on a patient-centred approach. An efficient use of available resources in diabetes clinics and distributing responsibilities between team members in close collaboration with patients and their families seems necessary. Further exploration of the providers' work situation and barriers to good interaction is needed. Our findings can help the policy makers in Oman, and countries with similar health systems, to improve the quality and organizational efficiency of diabetes care services.
  • Albert, F, et al. (författare)
  • Laser produced X-ray source in the 10-60 keV range at 1 kHz. Modified irradiation schemes in order to reach medical imaging quality
  • 2001
  • Ingår i: Journal de Physique IV: Proceedings. - EDP Sciences. - 1764-7177. ; 11:PR2, s. 429-432
  • Tidskriftsartikel (refereegranskat)abstract
    • By tightly focusing ultra-short pulses from a Ti:sapphire terawatt laser onto a high-Z metallic target, hard x-ray pulses of short duration are produced. In most of our previous work concerning x-rays, a 150 mJ laser pulse with a 110 A duration has been used. Using mostly tin and tantalum targets, hard x-rays in the 10-60 keV range have been produced and used in differential absorption imaging around the K-alpha absorption edge of a contrast agent and also in imaging employing gated viewing for suppression of scattered radiation. In order to increase the x-ray yield (shortening the acquisition time) an increase in the laser repetition rate is desirable while still staying in the K-alpha energy regime. We have used a I kHz repetition-rate laser delivering 35 fs pulses in order to work towards these goals. We have clear evidence of hard x-ray generation above 30 keV, even for low laser pulse energies. We also studied the effect of a fs prepulse. The medical imaging capability of the source was explored. The use of a prepulse has been optimized in order to improve the image quality as well as the overall x-ray generation yield.
  • Altucci, C, et al. (författare)
  • Frequency-resolved time-gated high-order harmonics
  • 1998
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - American Physical Society. - 1050-2947. ; 58:5, s. 3934-3941
  • Tidskriftsartikel (refereegranskat)abstract
    • We report measurements of high-order harmonic spectra obtained with a 800-nm 150-fs loser pulse with a time-varying degree of ellipticity. The modulation of the polarization in time is achieved by using birefringent optics and self-phase modulation in a glass plate. We can create one or two temporal gates of a few femtoseconds width, during which the polarization is linear and harmonic emission is efficient. The harmonic spectra observed experimentally demonstrate that harmonics generated with linear polarization are frequency chirped. The values measured experimentally are consistent with theoretical predictions based on the strong field approximation. [S1050-2947(98)05511-5].
  • Altucci, C, et al. (författare)
  • Influence of atomic density in high-order harmonic generation
  • 1996
  • Ingår i: Optical Society of America. Journal B: Optical Physics. - Optical Society of America. - 0740-3224. ; 13:1, s. 148-156
  • Tidskriftsartikel (refereegranskat)abstract
    • We have investigated how high-order harmonics generated in rare gases depend on the atomic density. The peak and the profile of the atomic density in the interaction region were measured as a function of the backing pressure and the distance from the nozzle by a differential interferometry technique, The conversion efficiency for the harmonics in the plateau was found to increase approximately quadratically over the entire range of peak pressures investigated (3-80 mbar). The intensity of the harmonics in the cutoff region, in contrast, increased only until an optimum peak pressure was reached, beyond which it decreased. This optimum peak pressure was found to be dependent on both the laser intensity and the process order. To understand this effect, we have performed extensive propagation calculations of both the fundamental and the harmonic fields, using ionization rates and dipole moments from a tunnel ionization model. We obtained good agreement with the experimental results. The observed effect is attributed to ionization-induced defocusing of the fundamental laser beam, which reduces the peak intensity obtained in the medium and shortens the extent of the plateau. (C) 1996 Optical Society of America
  • An, W. W., et al. (författare)
  • Synthesis and surface characteristics of CeTbO3+delta induced by femtosecond laser irradiation
  • 2007
  • Ingår i: Applied Surface Science. - Elsevier. - 1873-5584. ; 253:8, s. 3884-3887
  • Tidskriftsartikel (refereegranskat)abstract
    • This work describes the use of focused, high-intensity light from a Ti: sapphire laser that generates femtosecond pulses to irradiate mixture of CeO2 and Tb4O7 under ambient conditions. The prepared samples were investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). XRD and XPS measurement results demonstrated that solid solution CeTbO3+delta with cubic fluorite structure has been synthesized on the irradiated target surface. SEM micrographs showed that the ultra-short laser irradiation resulted in the formation of foamy structure and spherical particles with size varying from about 30 to 200 nm. The formation mechanism has been discussed in detail. (c) 2006 Elsevier B.V. All rights reserved.
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