The evolution of the electron distribution function, when an electric field that is not too small in comparison with the critical electron runaway field is applied along the confining magnetic field of a high temperature plasma, is analysed. In the regimes considered, a finite fraction of the electron population has magnetically trapped orbits, and is not appreciably affected by the applied electric field, while the distribution of circulating electrons tends to “slide away” as a whole. Then the Spitzer-Härm model for the current-carrying electron distribution is inadequate, and the role that collective modes, in particular current-driven microinstabilities, and collisions can play in producing a stationary electron distribution is analysed. Modes at the ion plasma frequency, ωpi, that are driven by the positive slope of the current-carrying electron distribution, can be excited, when the average electron drift velocity is a finite fraction of the electron thermal velocity, and transfer transverse energy to the main body of the electron distribution. These features are consistent with the experimental observations performed on the Alcator device. Modes at the “reduced” electron plasma frequency (k‖/k)ωpe can also be excited both in connection with the modes at ωpi and independently. Modes at the electron gyrofrequency Ωe associated with the loss-cone feature that the electron distribution tends to develop are considered, among others, as a factor for the strongly enhanced electron cyclotron emission experimentally observed in regimes where non-thermal electron distributions have been realized.
E Ef ff fi ic ca ac cy y o of f a a t th hr re ee e d da ay y c co ou ur rs se e o of f a az zi it th hr ro om my yc ci in n i in n m mo od de er ra at te el ly y s se ev ve er re e c co om mm mu un ni it ty y--a ac cq qu ui ir re ed d p pn ne eu um mo on ni ia a The aetiology of pneumonia was identified in 18 patients by serology (nine Mycoplasma pneumoniae, four Chlamydia pneumoniae, five Legionella pneumophila; one patient with chlamydial infection also had Klebsiella pneumoniae bacteraemia). A presumptive aetiological diagnosis was obtained with sputum culture in three other patients (one Haemophilus influenzae, two Haemophilus parainfluenzae), all strains were sole isolates with 10 8 Colony forming units (CFU), and with Gram stain in one patient with Streptococcus pneumoniae. All patients in the azithromycin group (one after a second 3 day course), and all but two (of those available for evaluation) of the clarithromycin group were cured. Defervescence occurred after 2.6±1.6 days, and chest roentgenogram cleared after 8.9±3.3 days, with no difference between the two groups. Tolerance was good, and there were no withdrawals from therapy.Azithromycin, as well as clarithromycin, may be a good first choice approach for the treatment of low to moderately severe community-acquired pneumonia, but a 3 day course of azithromycin may increase patient compliance.
The ELTRAP device installed at the Department of Physics of the University of Milan is a Malmberg–Penning trap, with a magnetic field up to 0.2 T, equipped with charge coupled device optical diagnostics. It is intended to be a small scale facility for electron plasma and beam dynamics experiments, and in particular for the study of collective effects, equilibrium states, and the formation of coherent structures in these systems. The device features a relatively long solenoid, corrected by 4 shims and 16 dipole coils, in order to obtain a large uniform magnetic field region. The modular electrode design allows several variations of the experimental configuration. The first experiments which assess the operation of the facility are described. Plasma confinement times up to several minutes have been obtained and an electron temperature of 4–8 eV has been measured.
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