Impulse rise and fall times of biplanar vacuum photodiodes

The impulse rise and fall times of biplanar vacuum photodiodes are experimentally investigated by the use of a single ultrashort laser pulse from a train of mode-locked pulses. It was confirmed that the impulse rise time is a function of the photoelectrons' transit time from photocathode to anode, and that the impulse fall time is 2.2 times the capacitance of the photodiode and the resistive component of the load.

Chromosome aberrations and culture time

Leukocytes from 17 A-bomb-exposed survivors and 10 control persons of the same age group were cultured for two and three days. Among the controls, aberrations other than single or isochromatid lesions were seen in 0.6 % of cells at two days of culture and in 0.8% of cells at three days of culture. Among the exposed, 7.0% of cells cultured for two days had these aberrations, which were seen in 8.7% of cells cultured for three days. Six cytogenetically aberrant clones were found in 5 of the 17 exposed survivors. Four of these were detectable on the basis of the two-day culture results alone. Since our previous studies of 171 heavily exposed survivors, using the 66 to 70 h culture time, had enabled us to detect only four clone-formers, it appears that the shorter culture time enhances clone detection.