| 1. |
- Bergkvist, Tommy, et al.
(author)
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Effects of ICRH on the dynamics of fast particle excited alfven eigenmodes
- 2007
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In: Radio Frequency Power in Plasmas. - : American Institute of Physics (AIP). - 9780735404441 - 0735404445 ; , s. 455-458
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Conference paper (peer-reviewed)abstract
- ICRH is often used in experiments to simulate destabilization of Alfvén eigenmodes by thermonuclear α-particles. Whereas the slowing down distribution of α-particles is nearly isotropic, the ICRH creates an anisotropic distribution function with non-standard orbits. The ICRH does not only build up gradients in phase space, which destabilizes the AEs, but it also provides a strong phase decorrelation mechanism between ions and AEs. Renewal of the distribution function by thermonuclear reactions and losses of α-particles to the wall lead to a continuous drive of the AEs. Simulations of the non-linear dynamics of AEs and the impact they have on the heating profile due to particle redistribution are presented.
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| 2. |
- Bergkvist, Tommy, et al.
(author)
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Non-linear Alfvén eigenmode dynamics of a burning plasma in the presence of ion cyclotron resonance heating
- 2006
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In: EPS Conf. Plasma Phys., EPS. - 9781622763337 ; , s. 1792-1795
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Conference paper (peer-reviewed)abstract
- Alfvén eigenmodes (AEs) excited by α particles in a burning plasma can degrade the heating efficiency by spatial redistribution of the resonant α particles. Changes of the orbit invariants in phase space by collisions and other waves, such as magnetosonic waves during ion cyclotron resonance heating (ICRH), lead to changes in the phase between the αs and AEs, causing a decorrelation of the interactions. ICRH lead to an increased decorrelation of the AE interactions and hence a stronger radial redistribution of the thermonuclear α particles by the AEs. Renewal of the distribution function by thermonuclear reactions and losses of α particles to the wall lead to a continuous drive of the AEs and a radial redistribution of the α particles. The redistribution results in a degradation of the heating efficiency.
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| 3. |
- Bergkvist, Tommy, et al.
(author)
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Non-linear dynamics of Alfvén eigenmodes excited by thermonulcear alpha particles in the presence of ion cyclotron resonance heating
- 2007
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In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 47:9, s. 1131-1141
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Journal article (peer-reviewed)abstract
- Alfvén eigenmodes (AEs) excited by thermonuclear α-particles can degrade the heating efficiency by spatial redistribution of the resonant α-particles. Changes of the orbit invariants in phase space by collisions and interactions with other waves, such as magnetosonic waves during ion cyclotron resonance heating (ICRH), lead to changes in the phase between the α-particles and AEs, causing a decorrelation of the interactions and stronger redistribution of the α-particles. Cyclotron interactions increase the decorrelation of the AE interactions with the high-energy ions and hence a stronger radial redistribution of the high-energy α-particles by the AEs. Renewal of the distribution function by thermonuclear reactions and losses of α-particles to the wall lead to a continuous drive of the AEs and a radial redistribution of the α-particles. The condition for excitation of AEs is shown to depend on the heating scenario where heating at the low field side creates a significant population of high-energy non-standard orbits which drive the modes. The redistribution results in a reduction in the averaged α-particle energy and a degradation of the heating efficiency. The effect on the distribution function in the presence of several unstable modes is not additive and the particle redistribution is found to saturate with an increasing number of modes.
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| 4. |
- Hellsten, Torbjörn A. K., et al.
(author)
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On ion cyclotron emission in toroidal plasmas
- 2006
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In: Nuclear Fusion. - 0029-5515 .- 1741-4326. ; 46:7, s. S442-S454
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Journal article (peer-reviewed)abstract
- A detailed study of ion cyclotron interactions in a toroidal plasma has been carried out in order to elucidate the role of toroidal effects on ion cyclotron emission. It is well known that non-relaxed distribution functions can give rise to excitation of magnetosonic waves by ion cyclotron interactions when the distribution function increases with respect to the perpendicular velocity. We have extended and clarified the conditions under which even collisionally relaxed distribution function can destabilize magnetosonic eigenmodes. In a toroidal plasma, cyclotron interactions at the plasma boundary with ions having barely co-current passing orbits and marginally trapped orbits can cause destabilisation by the strong inversion of the distribution function along the characteristics of cyclotron interaction by neo-classical effects. The unstable interactions can further be enhanced by tangential interactions, which can also prevent the interactions from reaching the stable part of the characteristics, where they interact with trapped orbits. Conditions on the localization of the magnetosonic eigenmodes for unstable excitation are analysed by studying the anti-Hermitian part of the susceptibility tensor of thermonuclear alpha-particles. The pattern of positive and negative regions of the anti-Hermitian part of the susceptibility tensor of thermonuclear alpha-particles is, in general, consistent with the excitation of edge localized magnetosonic eigenmodes, even though the eigenmodes are usually not localized in the major radius and for distribution functions that have relaxed to steady state.
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| 5. |
- Hellsten, Torbjörn, 1947-, et al.
(author)
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ICE in toroidal plasmas
- 2005
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In: IAEA Technical Meeting on Fast Particles.
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Conference paper (other academic/artistic)
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| 6. |
- Holmström, Kerstin, et al.
(author)
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On the dynamics of Alfvén eigenmode excitation
- 2006
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In: EPS Conference on Plasma Physics 2006, EPS 2006. - 9781622763337 ; , s. 1796-1799
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Conference paper (peer-reviewed)abstract
- Alfvén eigenmodes (AEs) excited by fast ions can cause losses of fast ions in thermonuclear experiments. To describe the dynamics of the AE excitation, it is necessary to include the decorrelation of the AE interactions and the renewal of the distribution function in the unstable regions on time scales that are short compared to the decorrelation time. For simulation of AE excitation for finite decorrelation times, a Monte Carlo operator describing the phase decorrelation between ions and AEs has been developed for implementation in the SELFO code.
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| 7. |
- Nederfors, Tommy, et al.
(author)
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The relation between xerostomia and hyposalivation in subjects with rheumatoid arthritis or fibromyalgia
- 2002
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In: Swedish Dental Journal. - : Swedish Dental Association. - 0347-9994. ; 26:1, s. 1-7
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Journal article (peer-reviewed)abstract
- Aim of this study was to evaluate the relation between xerostomia and hyposalivation in 100 subjects with either rheumatoid arthritis or fibromyalgia, and further, to evaluate the predictive value of xerostomia on hyposalivation. Unstimulated and chewing stimulated whole saliva was collected in the morning with the subjects in a strict fasting condition and then about 2 hours later, after intake of a standardised breakfast. All participants filled in a questionnaire, mainly dealing with xerostomia. Forty subjects demonstrated a pathological fasting unstimulated whole saliva secretion rate, the corresponding number for fasting stimulated secretion being 39. For unstimulated, but not for stimulated saliva, the fasting secretion rate was significantly lower than the non-fasting. Xerostomia was reported by 74 subjects, this group having significantly lower both unstimulated and stimulated secretion rates than the non-xerostomic group. On the individual level, the predictive value of xerostomia on hyposalivation showed high sensitivity but unsatisfactory specificity. In conclusion, this study underlines the importance of applying strictly standardised procedures when collecting saliva, and that fasting unstimulated whole saliva is the diagnostic salivary secretion of choice. Finally, xerostomia was found to predict hyposalivation on a group, but not on an individual level.
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| 8. |
- Rönnblom, Anders, et al.
(author)
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Clinical course of Crohn's disease during the first 5 years. Results from a population-based cohort in Sweden (ICURE) diagnosed 2005-2009
- 2017
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In: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 0036-5521 .- 1502-7708. ; 52:1, s. 81-86
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Journal article (peer-reviewed)abstract
- Objective: The aim of the study was to describe the medical treatment, change in phenotype, need for surgery and IBD-associated mortality during the first 5 years after diagnosis. Material and Methods: Patients diagnosed with Crohn's disease including all age groups in the Uppsala healthcare region in the middle of Sweden 2005-2009 were included in the study. Medical notes were scrutinised and patients contacted. Out of 269 patients, 260 (96.3%) could be followed for 5 full years or until death. Results: The following drugs were used: 5-ASA 66.7%, systemic steroids 76.4%, antimetabolites 56.7% and anti-TNF 20.3%. Described with the Montreal classification, the proportion with inflammatory behaviour decreased from 78.1% to 74.0% from diagnosis to end of the observation, patients with stricturing behaviour increased from 13.0% to 15.4% and patients with penetrating behaviour increased from 8.9% to 10.6%. After the first year, 12.4% had been treated with intestinal resection or colectomy, a figure that increased to 14.8 after 5 years. Two patients suffered an IBD-related death. Conclusions: Compared to similar patient cohorts, the present study demonstrates that although the course of Crohn's disease seems difficult to change during the first year after diagnosis, the following years up to 5 years shows a more benign course than has usually been described earlier.
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| 9. |
- Rönnblom, Anders, et al.
(author)
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Low colectomy rate five years after diagnosis of ulcerative colitis. Results from a prospective population-based cohort in Sweden (ICURE) diagnosed during 2005-2009*
- 2016
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In: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 0036-5521 .- 1502-7708. ; 51:11, s. 1339-1344
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Journal article (peer-reviewed)abstract
- Objective: The medical treatment of ulcerative colitis (UC) has seen a change towards a more active attitude during recent years, including both the use of more traditional drugs as well as new biological substances. In this epidemiological study we have evaluated the results of modern treatment of UC in a population-based cohort of patients including all age groups, with regard to relapse rate, colectomy and IBD-associated mortality.Material and methods: Patients diagnosed with UC in the Uppsala health care region in the middle of Sweden during 2005-2009 were included in the study. Out of 524 patients, 491 (93%) could be followed for five full years or until death.Results: Nineteen patients (3.9%) had died and two of these deaths could be attributed to UC (one postoperative death and one colonic carcinoma). The following drugs were used by the patients during the study period: 5-ASA (91%), systemic steroids (66%), immunomodulators (IMM), mainly thiopurines (26%) and anti-TNF (11%). During the observation period, 74% experienced at least one relapse and 5.3% were subjected to colectomy. Among patients<17 years at diagnosis, colectomy was performed in two (4.8%).Conclusions: Five years after diagnosis of ulcerative colitis, 5.3% had been subjected to colectomy and two patients (0.38%) had died because of the disease.
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| 10. |
- Sjöberg, Daniel, et al.
(author)
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Incidence and natural history of ulcerative colitis in the Uppsala Region of Sweden 2005-2009 - results from the IBD cohort of the Uppsala Region (ICURE).
- 2013
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In: Journal of Crohn's & Colitis. - : Oxford University Press (OUP). - 1873-9946 .- 1876-4479. ; 7:9, s. e351-7
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Journal article (peer-reviewed)abstract
- BACKGROUND AND AIMS: The incidence of ulcerative colitis (UC) increased during the 20th century in Western Europe and the North America, but there are conflicting reports whether the incidence has declined, stabilized or continued to increase. The aim of this study was to evaluate the incidence of UC in the Uppsala Region, Sweden.METHODS: All new UC patients in Uppsala County (305,381 inhabitants) were prospectively registered during 2005-2006 and the same for all new UC patients in the Uppsala Region (642,117 inhabitants) during 2007-2009. The extent and severity of disease according to the Montreal classification, relapse rates and surgery were assessed.RESULTS: 526 UC patients were included. The mean overall incidence for the time period was 20.0 (95% CI: 16.1-23.9) cases per 100,000 inhabitants. The incidence among children <17 years of age was 8.9 per 100,000. The extent at diagnosis was evenly distributed (E1: n=167, 32%, E2: n=161, 31%, E3: n=163, 31%). Half of the cases had moderate to severe symptoms (S1: n=269, 51%, S2: n=209, 40%, S3: n=45, 8.6%). 228 (43%) relapsed and 13 (2.5%) required colectomy during the first year. Children had a higher proportion of extensive disease vs adults (27/42 vs 136/484), but no increased risk for severe symptoms or colectomy.CONCLUSION: In this prospective population-based study we found one of the highest incidences of UC in the world. The proportion of severe cases is comparable with historical data. The conclusion is that the nature of UC has not changed, only the incidence.
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