| 1. |
- Sauter, O., et al.
(författare)
-
Control of neoclassical tearing modes by sawtooth control
- 2002
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 88:10
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Tidskriftsartikel (refereegranskat)abstract
- The onset of a neoclassical tearing mode (NTM) depends on the existence of a large enough seed island. It is shown in the Joint European Torus that NTMs can be readily destabilized by long-period sawteeth, such as obtained by sawtooth stabilization from ion-cyclotron heating or current drive. This has important implications for burning plasma scenarios, as alpha particles strongly stabilize the sawteeth. It is also shown that, by adding heating and current drive just outside the inversion radius, sawteeth are destabilized, resulting in shorter sawtooth periods and larger beta values being obtained without NTMs.
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| 2. |
- Mantsinen, M. J., et al.
(författare)
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Localized bulk electron heating with ICRF mode conversion in the JET tokamak
- 2004
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 44:1, s. 33-46
-
Tidskriftsartikel (refereegranskat)abstract
- Ion cyclotron resonance frequencies (ICRF) mode conversion has been developed for localized on-axis and off-axis bulk electron heating on the JET tokamak. The fast magnetosonic waves launched from the low-field side ICRF antennas are mode-converted to short-wavelength waves on the high-field side of the He-3 ion cyclotron resonance layer in D and He-4 plasmas and subsequently damped on the bulk electrons. The resulting electron power deposition, measured using ICRF power modulation, is narrow with a typical full-width at half-maximum of approximate to30 cm (i.e. about 30% of the minor radius) and the total deposited power to electrons comprises at least up to 80% of the applied ICRF power. The ICRF mode conversion power deposition has been kept constant using He-3 bleed throughout the ICRF phase with a typical duration of 4-6 s, i.e. 15-40 energy confinement times. Using waves propagating in the counter-current direction minimizes competing ion damping in the presence of co-injected deuterium beam ions.
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| 3. |
- Noterdaeme, J. M., et al.
(författare)
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Heating, current drive and energetic particle studies on JET in preparation of ITER operation
- 2003
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 43:3, s. 202-209
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes the recent work on JET in the three areas of heating, current drive and energetic particles. The achievements have extended the possibilities of JET, have a direct connection to ITER operation and provide new and interesting physics. Toroidal rotation profiles of plasmas heated far off axis with little or no refuelling or momentum input are hollow with only small differences on whether the power deposition is located on the low field side or on the high field side. With LH current drive the magnetic shear was varied from slightly positive to negative. The improved coupling (through the use of plasma shaping and CD4) allowed up to 3.4 MW of PLH in internal transport barrier (ITB) plasmas with more than 15 MW of combined NBI and ICRF heating. The q-profile with negative magnetic shear and the ITB could be maintained for the duration of the high heating pulse (8 s). Fast ions have been produced in JET with ICRF to simulate alpha particles: by using third harmonic He-4 heating, beam injected He-4 at 120 kV were accelerated to energies above 2 MeV taking advantage of the unique capability of JET to use NBI with 4 He and to confine MeV class ions. ICRF heating was used to replicate the dynamics of alpha heating and the control of an equivalent Q = 10 `burn' was simulated.
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| 4. |
- Noterdaeme, J. M., et al.
(författare)
-
Spatially resolved toroidal plasma rotation with ICRF on JET
- 2003
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 43:4, s. 274-289
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Tidskriftsartikel (refereegranskat)abstract
- Plasmas heated by ICRF only in the JET tokamak show distinct structures in the toroidal rotation profile, with regions where domega/dr > 0 when the minority cyclotron resonance layer is far off-axis. The rotation is dominantly co-current with a clear off-axis maximum. There is only a slight difference between a high-field side (HFS) or a low-field side position of this resonance layer: the off-axis maximum in the rotation profile is modestly higher for the HFS position. This is in contrast to the predictions of theories that rely mainly on the effects arising from ICRF-driven fast ions to account for ICRF-induced plasma rotation. The differences due to the direction of the antenna spectrum (co- or counter-) are small. A more central deposition of the ICRF power in L-mode and operation in H-mode both lead to more centrally peaked profiles, both in the co-direction. Strong MHD modes brake the rotation and lead to overall flat rotation profiles.
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| 5. |
- Westerhof, E., et al.
(författare)
-
Control of sawteeth and triggering of NTMs with ion cyclotron resonance frequency waves in JET
- 2002
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 42:11, s. 1324-1334
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Tidskriftsartikel (refereegranskat)abstract
- A new scenario to delay or prevent neoclassical tearing mode (NTM) onset is presented. By active sawtooth destabilization, short period and low amplitude sawteeth are generated, such that the sawtooth produced NTM seed island is reduced and the threshold normalized plasma pressure for triggering of NTMs, beta(Nonset), is increased. The scenario has been explored experimentally in the Joint European Torus (JET). Ion cyclotron resonance frequency (ICRF) waves tuned to the 2nd harmonic H-minority resonance have been used for sawtooth control. Whereas ICRF waves generally induce sawtooth stabilization, favouring the triggering of NTMs and reducing beta(Nonset), the present experiments show that by toroidally directed waves, ion cyclotron current drive is produced, and that sawteeth can be destabilized by careful positioning of the 2nd harmonic H resonance layer with respect to the sawtooth inversion radius. As a result, NTM onset is delayed and beta(Nonset) is increased above its value obtained in discharges with additional heating from neutral beam injection alone.
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| 6. |
- Mantsinen, M. J., et al.
(författare)
-
Analysis of ion cyclotron heating and current drive at omega approximate to 2 omega(cH) for sawtooth control in JET plasmas
- 2002
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 44:8, s. 1521-1542
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Tidskriftsartikel (refereegranskat)abstract
- Ion cyclotron heating and current drive at omega approximate to 2omega(cH) in JET deuterium plasmas with a hydrogen concentration n(H)/(n(D)+n(H)) in the range of 5-15% are analysed, comparing results of numerical computer modelling with experiments. Second harmonic hydrogen damping is found to be maximized by placing the resonance on the, low-field side (LFS) of the torus, which minimizes competing direct electron damping and parasitic high-harmonic D damping in the presence of D beams. The shape of the calculated current perturbation and the radial localization of the heating power density for the LFS resonance are consistent with the experimentally observed evolution of the sawtooth period when the resonance layer moves near the q = 1 surface. Since the calculated driven current is dominated by a current of diamagnetic type caused by finite orbit widths of trapped resonating ions, it is not too sensitive to the ICRF phasing. Control of sawteeth with ion cyclotron current drive using the LFS omega approximate to 2omega(cH) resonance in the present experimental conditions can thus be best obtained by varying the resonance location rather than the ICRF phasing. Due to differences in fast ion orbits, collisional electron heating and fast ion pressure profiles are significantly more peaked for a LFS resonance than for a high-field side (HFS) resonance. For the HFS omega approximate to 2omega(cH) resonance, an enhanced neutron rate is observed in the presence of D beam ions, which is consistent with parasitic D damping at the omega approximate to 2omega(cD) resonance in the plasma centre.
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| 7. |
- Pfaller, M.A., et al.
(författare)
-
Twelve years of fluconazole in clinical practice : Global-trends in species distribution and fluconazole susceptibility of bloodstream isolates of Candida
- 2004
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Ingår i: Clinical Microbiology and Infection. - : Elsevier BV. - 1198-743X .- 1469-0691. ; 10:SUPPL. 1, s. 11-23
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Tidskriftsartikel (refereegranskat)abstract
- We determined the species distribution and in-vitro susceptibility of 6082 bloodstream infection (BSI) isolates of Candida spp. collected from 250 medical centres in 32 nations over a 10-year period from 1992 through 2001. The species included 3401 C. albicans, 984 C. glabrata, 796 C. parapsilosis, 585 C. tropicalis, 153 C. krusei, 67 C. lusitaniae, 48 C. guilliermondii, 10 C. famata, 10 C. kefyr, six C. pelliculosa, five C. rugosa, four C. lipolytica, three C. dubliniensis, three C. inconspicua, two C. sake and one isolate each of C. lambica, C. norvegensis and C. zeylanoides. Minimum inhibitory concentration determinations were made using the National Committee for Clinical Laboratory Standards reference broth microdilution method. Variation in the rank order and frequency of the different species of Candida was observed over time and by geographic area. The proportion of BSI due to C. albicans and C. glabrata increased and C. parapsilosis decreased over time in Canada, the USA and Europe. C. glabrata was an infrequent cause of BSI in Latin America and the Asia-Pacific region. Very little variation in fluconazole susceptibility was observed among isolates of C. albicans, C. tropicalis and C. parapsilosis. These species accounted for 78% of all BSI and remained highly susceptible (91-100% susceptible) to fluconazole from 1992 to 2001 irrespective of geographic origin. The prevalence of fluconazole resistance among C. glabrata isolates was variable both over time and among the various countries and regions. Resistance to fluconazole among C. glabrata isolates was greatest in the USA and varied by US census region (range 0-23%). These observations are generally encouraging relative to the sustained usefulness of fluconazole as a systemically active antifungal agent for the treatment of candida BSI. © 2004 Copyright by the European Society of Clinical Microbiology and Infectious Diseases.
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| 8. |
- Cano, F., et al.
(författare)
-
Partial protection to respiratory syncytial virus (RSV) elicited in mice by intranasal immunization using live staphylococci with surface-displayed RSV-peptides
- 2000
-
Ingår i: Vaccine. - 0264-410X .- 1873-2518. ; 18:24, s. 2743-2752
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Tidskriftsartikel (refereegranskat)abstract
- A live bacterial vaccine-delivery system based on the food-grade bacterium Staphylococcus carnosus was used for delivery of peptides from the G glycoprotein of human respiratory syncytial virus, subtype A (RSV-A). Three peptides, corresponding to the G protein amino acids, 144-159 (denoted G5), 190-203 (G9) and 171-188 (G4 S), the latter with four cysteine residues substituted for serines, were expressed by recombinant means as surface-exposed on three different bacteria, and their surface accessibility on the bacteria was verified by fluorescence-activated cell sorting (FACS). Intranasal immunization of mice with the live recombinant staphylococci elicited significant anti-peptide as well as anti-virus serum IgG responses of balanced IgG1/IgG2a isotype profiles, and upon viral challenge with 10(5) tissue culture infectious doses(50) (TCID50), lung protection was demonstrated for approximately half of the mice in the G9 and G4 S immunization groups. To our knowledge, this is the first study in which protective immunity to a viral pathogen has been evoked using food-grade bacteria as vaccine-delivery vehicles.
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| 9. |
- Goetsch, L., et al.
(författare)
-
Influence of administration dose and route on the immunogenicity and protective efficacy of BBG2Na, a recombinant respiratory syncytial virus subunit vaccine candidate
- 2000
-
Ingår i: Vaccine. - 0264-410X .- 1873-2518. ; 18:24, s. 2735-2742
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Tidskriftsartikel (refereegranskat)abstract
- The immunogenicity and protective efficacy of BBG2Na, a novel recombinant respiratory syncytial virus subunit vaccine candidate, was assessed in BALB/c mice under various conditions of dose, administration route and number of immunisations. A single intra-peritoneal (i.p.) dose of 2 mu g, or two doses of 0.2 mu g, were sufficient to induce elevated RSV-A serum antibodies and sterilising lung protective immunity. Serum antibody titres were significantly boosted following second immunisations, but not a third. Of three routes of immunisation, i.p. induced the highest RSV-A antibody titres, followed in efficacy by the intramuscular (i.m.) and subcutaneous (s.c.) routes. Nonetheless, all three routes induced comparable and sterilising lung protection. In contrast, upper respiratory tract protection was observed only after i.p. vaccination, although significant viral titre reductions were evident following i.m. or s.c. immunisations. Interestingly, Pepscan analyses indicated that antibody epitope usage was highest in i.p. and lowest in i.m. immunised mice, respectively. Nonetheless, all routes resulted in antibody responses to known lung protective epitopes (protectopes). Thus, the prevention of serious lower respiratory tract disease, the principle goal of a RSV vaccine, but not URT infection, is dose dependent but unlikely to be influenced by the route of BBG2Na administration.
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| 10. |
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| 11. |
- Mantsinen, M. J., et al.
(författare)
-
Alpha-tail production with ion-cyclotron-resonance heating of He-4-beam ions in JET plasmas
- 2002
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 88:10
-
Tidskriftsartikel (refereegranskat)abstract
- Third-harmonic ion-cyclotron-resonance heating of He-4-beam ions has produced for the first time on the JET tokamak high-energy populations of He-4 ions to simulate 3.5 MeV fusion-born alpha (alpha) particles. Acceleration of He-4 ions to the MeV energy range is confirmed by gamma-ray emission from the nuclear reaction Be-9(alpha, ngamma) C-12 and excitation of Alfven eigenmodes. Concomitant electron heating and sawtooth stabilization are observed. The scheme could be used in next-step tokamaks to gain information on trapped alpha particles and to test a diagnostics in the early nonactivated phase of operation.
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| 12. |
- Mayoral, M L, et al.
(författare)
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Sawtooth and neoclassical tearing mode seed island control by ICRF current drive on JET
- 2001
-
Ingår i: RADIO FREQUENCY POWER IN PLASMAS. - 0735400385 ; , s. 106-109
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Konferensbidrag (refereegranskat)abstract
- In recent experiments at JET, ICRF waves were used to either stabilise or destabilise sawteeth, and consequently control the formation of the seed island responsible for the appearance of Neoclassical Tearing Modes (NTMs) known to limit the tohamak performance. Two scenarios were studied in deuterium plasmas with a hydrogen concentration of 5 to 10 %. Firstly, using a toroidal magnetic field B-0 of 2.5T, the fundamental hydrogen cyclotron resonance layer (omega=omega(cH)) was positioned at the High Field Side (HFS) at the sawtooth inversion radius (R(inv)similar toR(q=1)). With +90degrees phased wave, monster sawteeth were obtained that triggered NTMs. Secondly, ICRF waves at the 2(nd) harmonic hydrogen cyclotron resonance (omega=2omega(cH)) positioned at the Low Field Side (LFS) with B-0 between 1.2T and 1.6T, was used to reduce the sawtooth period and increase the NTM beta(n) onset level.
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| 13. |
- Rutqvist, J., et al.
(författare)
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Coupled thermo-hydro-mechanical analysis of a heater test in fractured rock and bentonite at Kamaishi Mine - comparison of field results to predictions of four finite element codes
- 2001
-
Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 38:1, s. 129-142
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Tidskriftsartikel (refereegranskat)abstract
- Four computer codes were applied for a prediction of coupled thermo-hydro-mechanical responses during an in situ heater experiment which simulates a nuclear waste deposition hole with a waste over-pack and bentonite buffer, surrounded by fractured rock. The elevated temperature in the heater surroundings, which was maintained at 100 C for 8.5 months, generated substantial heat-driven moisture flow and swelling in the clay buffer, and thermal expansion of the surrounding fractured rock. Predicted system responses - including temperature. moisture content, fluid pressure, stress and displacement - were compared to measurements at 70 sensors located both in the clay buffer and the near-field rock. An overall good agreement between modeling and measured results indicates that most thermo-hydro-mechanical responses are fairly well represented by the coupled numerical models. Uncertainties occur for modeling of hydromechanical behavior of the swelling clay buffer at low saturation, modeling of near-field heterogeneous mechanical behavior of the low-stressed fractured reek, and modeling of the rock-buffer interface.
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| 14. |
- Rutqvist, Jonny, et al.
(författare)
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Evaluation of the Impact of Thermal-Hydrological-Mechanical Couplings in Bentonite and Near-Field Rock Barriers of a Nuclear Waste Repository in Sparsely Fractured Hard Rock
- 2004
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Ingår i: Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-Systems — Fundamentals, Modelling, Experiments and Applications. - : Elsevier. ; , s. 217-223
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Bokkapitel (refereegranskat)abstract
- As part of the international DECOVALEX III project and the European BENCHPAR project, this paper evaluates the impact of thermal-hydrological-mechanical (THM) couplings on the performance of a bentonite back-filled nuclear waste repository in sparsely fractured hard rock. The significance of THM coupling on the performance of a hypothetical repository is evaluated by several independent coupled numerical analyses. Moreover, the influence of a discrete fracture intersecting a deposition hole is discussed. The analysis shows that THM couplings have the most impact on the mechanical behaviour of bentonite-rock system, which is important for repository design considerations.
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| 15. |
- Rutqvist, J., et al.
(författare)
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Thermohydromechanics of partially saturated geological media : governing equations and formulation of four finite element models
- 2001
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 38:1, s. 105-127
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the general governing equations for coupled thermohydromechanical (THM) processes in saturated and unsaturated geologic formations and reviews four finite element codes fur modeling of such system. Three of the codes are developed for the special purpose of analyzing coupled THM processes in unsaturated porous and fractured geological media, and the fourth is a commercial code that has been used in its standard version, with a few adaptations for this specialized problem. The basic assumptions and fundamental equations for coupled THM processes in unsaturated porous fractured rock are presented. and formulations of the four finite element models are compared.
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| 16. |
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| 17. |
- Ståhl, Stefan, et al.
(författare)
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Staphylococcal surface display and its applications
- 2000
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Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1438-4221 .- 1618-0607. ; 290:7, s. 571-577
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Forskningsöversikt (refereegranskat)abstract
- Novel surface proteins can be introduced onto the bacterial cell surface by recombinant means. Here, we describe the development of such display systems for two food-grade bacteria, Staphylococcus carnosus and Staphylococcus xylosus, and present how such engineered bacteria can be used in different applications. A study will be described in which such staphylococci were employed as vaccine delivery vehicles to elicit protective antibody responses to respiratory syncytial virus (RSV). The use of surface-engineered staphylococci as novel microbial biocatalysts, as a new type of whole-cell diagnostic devices or for adsorption of metal ions with potential environmental or biosensor applications, will also be discussed.
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