Variation of cosmic ray intensity with altitude was measured at Mt. Fuji located at about 26°N on geomagnetic latitude on August 1994. The measurement was carried out with a spectrometer equipped with a 76.4 mm (3″) diameter spherical NaI (Tl) scintillator. Analysis was made for absorbed energy spectra above 3 Me V by the peeling-off method, and the cosmic ray intensity was calculated as the exposure rate from the ionizing component of the cosmic rays. The cosmic ray intensity increased with increasing altitude. The maximum (30.7×10-10C/kg/h) and minimum (8.5×10-10 C/kg/h) values were observed at summit area of Mt. Fuji (3740 m) and near the sea level (about 20 m), respectively. Above 2500 m, the rate of change of cosmic ray intensity with altitude was estimated to be about 0.99×10-12 (C/kg) /h/m. The rate from near the sea level to about 2 500 m was also estimated to be about 0.39×10-12 (C/kg) /h/m.
This note describes the characteristics and the usefulness of hexafluoroethane, C2F6as a counting gas of a position-sensitive3He proportional counter. The gas multiplication property of a gas mixture of3He and C2F6, and the usefulness of the gas mixture for improvement of the position resolution for thermal neutrons are presented. Though C2F6was not suitable as a counting gas of a proportional counter, the addition of C2F6improved the position resolution for thermal neutrons.
Bisbenzylisoquinoline alkaloids of Stephania cepharantha have been used for various clinical purposes and recently reevaluated as stimulators of interleukin secretion in tissues. We analyzed molecular structures of bisbenzylisoquinoline alkaloids by determining their molecular weights using the252Cf-plasma desorption mass spectrometry (PDMS) . The spectra were accumulated for 500000 fission events. The acceleration voltage used here was 15kV. Samples were analyzed using nitrocellulose-coated sample targets. Of the 5 alkaloids studied here, cepharanthine gave a main peak of molecular weight of 606.1 for the theoretical molecular weight of 606.7. The other minor peaks were considered to be demethylated fragment ions. 252Cf-PDMS should be quite useful in studying structure, metabolism and pharmacokinetics of various drugs with extremely low coefficients of variation.