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Hot electrons as well as hot ions are a desirable feature of any fusion device. By particle simulations (in slab geometry) and simple theory, investigations are made on two variants of the Toroidal Cusp Experiment (TCX) with an eye to achieving hot electrons, while retaining its large direct ion heating feature. A toroidal field added to the TCX configuration, with cusp magnets arranged poloidally to partly cancel cusp trapping of the electrons, ensures electron flow across the cusps and electron heating. Helical winding of the cusp magnets around the torus with pitch ? (m/M)1/2allows trapped electron flow on average helical paths; however, ions can still flow across the cusps, and the ·heating of ions and electrons can be varied at will.

Three-dimensional fluid and kinetic models are being used to simulate the turbulent confinement of energy and plasma in the core of tokamaks. These simulations represent a qualitative improvement in the realism with which they model large tokamak experiments, because they use realistic plasma parameters and incorporate important geometrical effects. The combination of algorithm improvements and the application of high-performance computing methodology including the use of massively parallel computers has enabled dramatic improvements in simulation capability. A consortium of research groups from universities and national laboratories are collaborating in this effort which is entitled the Numerical Tokamak Project and is supported in part by the High Performance Computing and Communications Initiative.

Objective: Estradiol levels in girls with premature thelarche have not previously been well defined because of the lack of adequate sensitivity of previously available estradiol assays. The ultrasensitive recombinant cell bioassay for estradiol has made the study of estradiol levels in premature thelarche possible. We hypothesized that girls with premature thelarche have higher estradiol levels than normal prepubertal girls. Study design: We used an ultrasensitive recombinant cell bioassay to study estradiol levels in 20 girls with premature thelarche and 15 normal prepubertal girls less than 3 years of age. The 2 groups were compared by Student t test. Results: Estradiol levels were significantly greater in the girls with premature thelarche (8.4 +/- 4.5 pmol/L estradiol equivalents) than in the normal prepubertal girls (3.3 +/- 3.5 pmol/L estradiol equivalents; P < .01). The estradiol level was not significantly correlated with age, height, weight, body mass index, age at onset of thelarche, or the presence or absence of ovarian cysts. Conclusion: Girls with premature thelarche have significantly higher estradiol levels than normal prepubertal girls. This is consistent with the hypothesis that the mechanism of premature thelarche involves increased estradiol levels rather than increased sensitivity of breast tissue to normal estradiol levels. (J Pediatr 1999;134:190-2)