| Budget Amount *help |
¥3,440,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥240,000)
Fiscal Year 2007: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2006: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2005: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
Ultraviolet (UV) disinfection has been found to be effective even for chlorine-resistant pathogenic microbes such as Cryptosporidium. The efficacy of UV irradiation in inactivating microbes depends on the irradiation dose of UV irradiation. The methods usually used to measure the UV irradiation dose are the photospectrometer and the biodosimeter, in which microbes that are highly sensitive to UV irradiation, such as QB and Bacillus subtilis, are utilized. However, these methods enable us to measure only the average dose in the UV reactor. The minimum dose of UV irradiation, such as when a short circuit flow is generated, cannot be measured directly, and can only be estimated by computational fluid dynamics. In the present study, we encapsulated photochromic compounds, which are organic compounds that develop colors upon UV irradiation, in microcapsules, and prepared a microdosimeter whose diameter and specific gravity were identical with those of the microbes to be sterilized. We then measured the intensity of the color that was developed in individual capsules upon UV irradiation, and attempted to evaluate the distribution of the UV dose with which individual microbes were irradiated.
BMLB was found to be the most sensitive to UV irradiation among the 30 photochromic compounds, and its quenching speed was slow. Therefore, BMLB was the most suitable photochromic compound for preparing the UV dosimeter. Although the mechanism by which BLMB develops a color is complex, it is hypothesized that when BLMB is excited by UV irradiation, BLMB releases H radicals and COPh radicals, which are oxygenated and become cations, thereby developing a color. Although BLMB developed a color upon UV irradiation regardless of the solvent in which it was dissolved, the color was intense and the quenching speed was slow particularly when it was dissolved in 2-propanol (isopropyl alcohol), methanol, 2-butanone (methyl ethyl ketone), or toluene.
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