| 1. |
- Wendt, M., et al.
(författare)
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Current Limitation and Inertial Resistance of an Inhomogeneous Plasma Diode
- 2001
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Ingår i: Physica Scripta. - 0281-1847. ; 64, s. 372-381
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Tidskriftsartikel (refereegranskat)abstract
- Inhomogeneous, collisionfree and bounded plasmas may support large potential drops even for steady electron motion. We present an experimental investigation of the exdended potential drops and transient current pulses, which form when a voltage drop U-a is suddenly applied to a magnetized, collisionfree plasma column with an axial ion density minimum. For well magnetized electrons the resistance at the current maximum agrees with the "intertial resistance" which is approximately proportional to U-a(1/2) for U-a much larger than the electron thermal temperature. The sharp drop following the current maximum is caused by the radial redistribution of the unmagnetized ions due to the transient radial electric field. For larger times (t > 10 omega (-1)(pi)) the measured resistance becomes approximately proportional to U-a as in the strong double layer that finally forms.
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| 2. |
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| 3. |
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| 4. |
- Nygard, K, et al.
(författare)
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Emerging genotype (GGIIb) of norovirus in drinking water, Sweden
- 2003
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Ingår i: Emerging Infectious Diseases. - 1080-6040 .- 1080-6059. ; 9:12, s. 1548-1552
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Tidskriftsartikel (refereegranskat)abstract
- From May through June 2001, an outbreak of acute gastroenteritis that affected at least 200 persons occurred in a combined activity camp and conference center in Stockholm County. The source of illness was contaminated drinking water obtained from private wells. The outbreak appears to have started with sewage pipeline problems near the kitchen, which caused overflow of the sewage system and contaminated the environment. While no pathogenic bacteria were found in water or stools specimens, norovirus was detected in 8 of 11 stool specimens and 2 of 3 water samples by polymerase chain reaction. Nucleotide sequencing of amplicons from two patients and two water samples identified an emerging genotype designated GGIIb, which was circulating throughout several European countries during 2000 and 2001. This investigation documents the first waterborne outbreak of viral gastroenteritis in Sweden, where nucleotide sequencing showed a direct link between contaminated water and illness.
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| 5. |
- Torvén, Staffan, et al.
(författare)
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Experimental Investigations and Simulations of Quasi-Steady Potential Drops
- 2001
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Ingår i: Phys. Chem. of the Earth C. - 1464-1917. ; 26, s. 71-80
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic-field-aligned potential drops in the auroral zone have recently been interpreted in terms of "quasi-steady" states which are evaluated for a fixed, given ion density profile. Here we present experimental studies of such states, observed when a voltage drop is suddenly applied to an inhomogeneous plasma column with a homogeneous, axial magnetic field. The quasi-steady potential drops have a spatial extension related to the gradient length of the initial ion density and the potential profile steepens slowly to a U-shaped double layer on the ion time scale. They exist only when the applied voltage drop does not exceed a critical value which depends on the maximum difference in ion density. Higher voltage drops concentrate in a cathode sheath. Results from PIC-simulations and from a theoretical model, based on steady electron motion, are also presented. They agree excellently for times up to about an ion plasma period (omega (-1)(pi)) The theoretical current-voltage characteristic, which is determined by electron reflection at a virtual cathode formed in the plasma, agrees with the experiments up to about one omega (-1)(pi). However, already at about 4 omega (-1)(pi) the measured currents have dropped much below the theoretical values, and also the measured average potential profiles are inconsistent with steady acceleration of the electrons. The increased resistivity is associated with strong fluctuations.
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