RESUMO
We report the identification of a localized current structure inside the JET plasma. It is a field-aligned closed helical ribbon, carrying current in the same direction as the background current profile (cocurrent), rotating toroidally with the ion velocity (corotating). It appears to be located at a flat spot in the plasma pressure profile, at the top of the pedestal. The structure appears spontaneously in low density, high rotation plasmas, and can last up to 1.4 s, a time comparable to a local resistive time. It considerably delays the appearance of the first edge localized mode.
RESUMO
The first results of the Dynamic Ergodic Divertor in TEXTOR, when operating in the m/n=3/1 mode configuration, are presented. The deeply penetrating external magnetic field perturbation of this configuration increases the toroidal plasma rotation. Staying below the excitation threshold for the m/n=2/1 tearing mode, this toroidal rotation is always in the direction of the plasma current, even if the toroidal projection of the rotating magnetic field perturbation is in the opposite direction. The observed toroidal rotation direction is consistent with a radial electric field, generated by an enhanced electron transport in the ergodic layers near the resonances of the perturbation. This is an effect different from theoretical predictions, which assume a direct coupling between rotating perturbation and plasma to be the dominant effect of momentum transfer.
RESUMO
An outbreak of acute infectious nonbacterial gastroenteritis (AING) occurred in a high school in Maryland in 1984. Thirty-six percent of students surveyed met the case definition of gastroenteritis, as did 24 percent of school employees. Eating lunch in the cafeteria on January 30 was significantly associated with illness. After controlling for other food items consumed during the January 30 lunch, only the sandwiches were significantly associated with illness, but the source of the contamination was not identified. Four of 17 serum pairs from sick students and none of the 8 serum pairs from exposed controls (a nonsignificant difference) showed at least a 4-fold rise in antibody titre to Norwalk virus between acute- and convalescent-phase specimens. This outbreak of AING is believed to be the first to implicate epidemiologically sandwiches as vehicles of transmission. The outbreak highlights the need for investigators to look for a viral etiology in gastroenteritis outbreaks.
