| 1. |
- Brunsell, Per, et al.
(författare)
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Initial results from the rebuilt EXTRAP T2R RFP device
- 2001
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Ingår i: Plasma Physics and Controlled Fusion. - BRISTOL. ENGLAND : IOP PUBLISHING LTD. - 0741-3335 .- 1361-6587. ; 43:11, s. 1457-1470
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Tidskriftsartikel (refereegranskat)abstract
- The EXTRAP T2R thin shell reversed-field pinch (RFP) device has recently resumed operation after a major rebuild including the replacement of the graphite armour with molybdenum limiters, a fourfold increase of the shell time constant, and the replacement of the helical coil used for the toroidal field with a conventional solenoid-type coil. Wall-conditioning using hydrogen glow discharge cleaning was instrumental for successful RFP operation. Carbon was permanently removed from the walls during the first week of operation. The initial results from RFP operation with relatively low plasma currents in the range I-p = 70-100 kA are reported. RFP discharges are sustained for more than three shell times. Significant improvements in plasma parameters are observed, compared to operation before the rebuild. There is a substantial reduction in the carbon impurity level. The electron density behaviour is more shot-to-shot reproducible. The typical density is n(e) = 0.5-1 x 10(19) m(-3). Monitors of H-alpha line radiation indicate that the plasma wall interaction is more toroidally symmetric and that there is less transient gas release from the wall. The minimum loop voltage is in the range V-t = 28-35 V, corresponding to a reduction by a factor of two to three compared to the value before the rebuild.
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| 2. |
- Gravestijn, Robert, et al.
(författare)
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Comparison of confinement in resistive-shell reversed-field pinch devices with two different magnetic shell penetration times
- 2004
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 46:1, s. 11-22
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Tidskriftsartikel (refereegranskat)abstract
- A loop voltage is required to sustain the reversed-field pinch (RFP) equilibrium. The configuration is characterized by redistribution of magnetic helicity but with the condition that the total helicity is maintained constant. The magnetic field shell penetration time, tau(s), has a critical role in the stability and performance of the RFP Confinement in the EXTRAP device has been studied with two values of tau(s), first (EXTRAP-T2) with tau(s), of the order of the typical relaxation cycle timescale and then (EXTRAP-T2R) with tau(s), much longer than the relaxation cycle timescale, but still much shorter than the pulse length. Plasma parameters show significant improvements in confinement in EXTRAP-T2R. The typical loop voltage required to sustain comparable electron poloidal beta values is a factor of 3 lower in the EXTRAP-T2R device. The improvement is attributed to reduced magnetic turbulence.
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| 3. |
- Hedqvist, Anders, et al.
(författare)
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Contributions of thermal charge exchange excitation to the Rydberg series of Cl16
- 2000
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 33:3, s. 375-382
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Tidskriftsartikel (refereegranskat)abstract
- Spectra from the Rydberg series 1s-np for the principal quantum numbers n greater than or equal to 8 of Cl16+ are observed on the JET tokamak. Individual lines up to n = 15 are resolved. The line intensity of n = 10 is enhanced, relative to the underlying 1/n(3) scaling, due to charge exchange collisions with neutral deuterium in the ground state. The observations are compared with predictions based on available partial charge exchange cross section data. There is generally good agreement, however, some details of the predicted n-shell distribution are different from those observed in the experiment.
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| 4. |
- Wahlberg, Elisabet, et al.
(författare)
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An affibody in complex with a target protein: Structure and coupled folding.
- 2003
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 100:6, s. 3185-3190
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Tidskriftsartikel (refereegranskat)abstract
- Combinatorial protein engineering provides powerful means for functional selection of novel binding proteins. One class of engineered binding proteins, denoted affibodies, is based on the three-helix scaffold of the Z domain derived from staphylococcal protein A. The Z(SPA-1) affibody has been selected from a phage-displayed library as a binder to protein A. Z(SPA-1) also binds with micromolar affinity to its own ancestor, the Z domain. We have characterized the Z(SPA-1) affibody in its uncomplexed state and determined the solution structure of a Z:Z(SPA-1) protein-protein complex. Uncomplexed Z(SPA-1) behaves as an aggregation-prone molten globule, but folding occurs on binding, and the original (Z) three-helix bundle scaffold is fully formed in the complex. The structural basis for selection and strong binding is a large interaction interface with tight steric and polar/nonpolar complementarity that directly involves 10 of 13 mutated amino acid residues on Z(SPA-1). We also note similarities in how the surface of the Z domain responds by induced fit to binding of Z(SPA-1) and Ig Fc, respectively, suggesting that the Z(SPA-1) affibody is capable of mimicking the morphology of the natural binding partner for the Z domain.
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