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To monitor personal exposure to biologically effective solar-UV radiation, Bacillus subtilis spores on a membrane filter and UV-coloring labels were incorporated into a monitoring badge. The samples were covered with one of three types of filter sheet, dependent on the season, to reduce the amounts of exposure to measurable levels. Five fifth-or sixth-grade classes of primary schools, each consisting of 30-40 children, were chosen in northern (Sapporo), central (Tsukuba and Tokyo), and southern (Miyazaki and Naha) cities in Japan. In all four seasons, each child wore a badge on an upper arm for the entire waking hours, changing it daily, for a week. Upon collection of the badges, the survival of spores and the extent of coloration of the label were determined. The results were used to estimate the amount of daily exposure to biologically effective UV radiation, expressed as the value of spore inactivation dose. Unexpectedly, the average amounts of exposure were not directly correlated with the outdoor UV irradiance: in the two southern cities, despite high outdoor irradiance from spring to autumn, the average amounts of exposure were less than 3.1% of the average irradiance. Highly concentrated exposures occurred in two central cities on three days when extensive outdoor exercise took place. These results contradict the simple notion that childrens' exposure is in proportion to the outdoor UV irradiance, and support the view that the extent of solar-UV exposure is primarily determined by life-style rather than living location.Key words: Solar-UV radiation -Spore dosimetry -Schoolchildren Solar-UV radiation is one of the most ubiquitous genotoxic agents to which organisms on the earth are exposed. The grim possibility that this could be increased by the depletion of the stratospheric ozone layer due to anthropological release of chlorofluorocarbons has raised serious concern about medical, agricultural, and ecological consequences. The incidence of skin cancers is well correlated with the amount of UV irradiance, which in turn is primarily dependent on geography, and this dependence constitutes the basis of various models predicting the increase in skin cancer incidence as a consequence of ozone depletion.1-4) However, we have little knowledge about the extent of personal exposure to solar-UV radiation, and how it is related to environmental irradiance.A major problem in quantifying the solar-UV exposure is how to measure it. Sunlight is polychromatic, and biologically harmful effects are mainly attributable to the shortest region of UV wavelengths. Therefore, to measure it with a broad-band UV detector is problematic, since the less damaging portions of the radiation are always more abundant. This problem can be circumvented by the use of a biological dosimeter that can automatically integrate the effectiveness spectrum over the entire UV wavelength range. For this purpose, the spore dosimeter that has been established and developed during the past decade by one of us seems most suitable.5-7) We have fitted spor...

In this paper, a discrete modified Smith predictor based on optimal control design method is proposed. A plant with long dead-time is controlled by means of a predicted-state feedback technique and a modified Smith predictor composed of a plant predictor and an observer. In this method, states of a plant are obtained by an observer because the states are not measured directly in practice. The advantages of the proposed method are that a steady-state error caused by a disturbance can be eliminated and that an unstable plant can be made stable unlike conventional methods such as Smith predictor and Internal Model Control. It also achieves good robustness to modeling errors by adjusting weights of LQI-scheme. In simulation studies, it is shown that the proposed method is effective for these plants. Furthermore, by applying the proposed method to a pneumatic actuator, the effectiveness of the method is confirmed.

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