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Abstract:A low-concentration hydrogen peroxide solution containing titanium dioxide as a photocatalyst has attracted attention as a safe office bleaching agent. In this study, the influence of different kinds of light on the bleaching effect of this agent was examined. The bleaching agent was applied to hematoporphyrinstained paper strips that were then irradiated with a 405-nm diode laser (800 mW/cm 2 ), a halogen lamp (720 mW/cm 2 ), or an LED (835 mW/cm 2 ) for 5 minutes. The color was measured spectrophotometrically before treatment and every 30 seconds thereafter, and the effects of bleaching on the strip were assessed using the CIE 1976 L * a * b * color coordinate system. Of the three different irradiation conditions, 405-nm laser irradiation gave the strongest bleaching effect with 3.5% hydrogen peroxide containing titanium dioxide. The laser provides strong irradiance at 405 nm, which corresponds to the absorption range of the bleaching agent, and consequently the largest effect was obtained.

MaterialsAll chemicals were used without further purification. Methylmethacrylate (MMA) and ammonium peroxodisulfate (APS) were purchased from TOKYO CHEMICAL INDUSTRY Co.. Distilled and deionized water was used as a solvent. Polymerization inhibitor (6-tert-Butyl-2,4-xylenol) which is contained in the packed methylmethacrylate chemicals was removed by an alumina column chromatography. Tandem acoustic emulsification2.134 g of MMA was added to 22.7 ml of deionized water in glass beaker cell (1 : 10 volume ratio of MMA to water). Then, the 20 kHz ultrasonication to the water/MMA mixture was conducted with an ultrasonic stepped horn (13 mm diameter, titanium alloy) connected with a 20 kHz oscillator (44 W cm -2 , SONIFIER-250D, Branson Ultrasonics Co.) for 8 min. The sequential ultrasonication with 500 kHz treatment after 20 kHz was carried out using an ultrasonic transducer (4 W cm -2 , Honda Electric Co.) connected with a Pyrex glass cylindrical tube (diameter, 24 mm; length, 75 mm) for 10 min. Subsequently, the sequential ultrasonication with 1.6 MHz treatment after 20 kHz and 500 kHz was carried out using an ultrasonic transducer (16 W cm -2 , Honda Electric Co.) connected with a Pyrex glass cylindrical tube (diameter, 24 mm; length, 75 mm) for 10 min. Finally, the further sequential ultrasonication with 2.4 MHz treatment after 20 kHz, 500 kHz and 1.6 MHz was conducted by an ultrasonic transducer (7 W cm -2 , Honda Electric Co.) connected with a Pyrex glass cylindrical tube (diameter, 24 mm; length, 75 mm) for 10 min.

Demetalation kinetics of natural chlorophyll (Chl) d purified from Acaryochloris marina was first studied and compared with those of Chls a and b. The demetalation rate constant of Chl d, which possessed a formyl group at the 3-position, was five-fold smaller than that of Chl a possessing a vinyl group at the same position in aqueous acetone at the proton concentration of 1.2 x 10(-3) M at 25 degrees C. In contrast, the demetalation rate constant of Chl b possessing a formyl group at the 7-position was 26 times smaller than that of Chl a. The activation energy of demetalation reaction of Chl d was larger than that of Chl a, but smaller than that of Chl b. These indicate that the substitution effect of 3-formyl group on the acidic removal of central magnesium in Chls was smaller than that of 7-formyl group.

Using field cages, we tested the hypothesis that two phytophagous ladybird beetles, Henosepilachna niponica (Lewis) and Henosepilachna yasutomii Katakura (Coleoptera: Coccinellidae: Epilachninae), are reproductively isolated from each other by their host fidelity alone. We planted host plants of the two species [the thistle Cirsium alpicola Nakai (Asteraceae) for H. niponica and the blue cohosh, Caulophyllum robustum Maxim. (Berberidaceae), for H. yasutomii ] in 7 × 7 m cages (BT cages), and planted the two host plants and the beetles' common food plant, the Japanese nightshade, Solanum japonense Nakai (Solanaceae), in other cages (BJT cages). We then released overwintered reproducing beetles into these cages and recorded their dispersal, the distribution of egg masses, and the incidence of copulations. In BT cages, the beetles moved almost exclusively between their own host plants, and all females laid eggs exclusively on their own host plants. In BJT cages, the beetles moved between their own host plants and the Japanese nightshade, resulting in occasional interspecific mating on the same nightshade plant. Females of both species laid eggs on their own host plants as well as on the Japanese nightshade. These results indicate that host fidelity functions as a strong barrier against gene flow between H. niponica and H. yasutomii . However, this barrier can easily be broken down if a third plant species bridges the beetle populations.

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Demetalation kinetics of bacteriochlorophylls (BChls) c, d and e from green sulfur photosynthetic bacteria were studied under weakly acidic conditions. Demetalation rate constants of BChl e possessing a formyl group at the 7-position were significantly smaller than those of BChls c and d, which had a methyl group at this position. The activation energy of demetalation of 3(1)R-8,12-diethyl([E,E])-BChl e was 1.5-times larger than that of 3(1)R-[E,E]-BChl c. 15N-labeled 3(1)R-[E,E]-BChls c and e were purified from cells of green sulfur bacteria grown in a medium containing 15NH4Cl, and their 15N NMR spectra were measured. The chemical shifts of N21, N22 and N23 atoms of 3(1)R-[E,E]-BChl e were lower-field shifted than those of 3(1)R-[E,E]-BChl c, respectively, and especially the difference in chemical shifts of N22 was significantly large. These results suggest that the electron-withdrawing formyl group at the 7-position of BChl e affected an electronic state of the chlorin macrocycle and caused BChl e to be more tolerant for removal of the central magnesium compared with BChls c and d.

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