Electronic states of P donors in Si nanocrystals (nc-Si) embedded in insulating glass matrices have been studied by electron spin resonance. Doping of P donors into nc-Si was demonstrated by the observation of optical absorption in the infrared region due to intraconduction band transitions. P hyperfine structure (hfs) was successfully observed at low temperatures. The observed splitting of the hfs was found to be much larger than that of the bulk Si:P and depended strongly on the size of nc-Si. The observed strong size dependence indicates that the enhancement of the hyperfine splitting is caused by the quantum confinement of P donors in nc-Si.

Double roughness structure, the origin of the lotus effect of natural lotus leaf, was successfully reproduced on a diarylethene microcrystalline surface. Static superwater-repellency and dynamic water-drop-bouncing were observed on the surface, in the manner of natural lotus leaves. Double roughness structure was essential for water-drop-bouncing. This ability was not observed on a single roughness microcrystalline surface showing the lotus effect of the same diarylethene derivative. The double roughness structure was reversibly controlled by alternating irradiation with UV and visible light.

Two rice (Oryza sativa) waxy mutations of the Japonica background were shown to contain approximately 20% of the fully spliced mRNA relative to the wild type. Sequencing analysis of the entire waxy genes of the two mutants revealed the presence of premature translation termination codons in exon 2 and exon 7. These results indicated that the lower accumulation of fully spliced RNA in the mutants was caused by nonsense-mediated decay (NMD), which is an RNA surveillance system universally found in eukaryotes. It is interesting that levels of RNA retaining intron 1 were not changed by premature nonsense codons, suggesting that splicing may be linked with NMD in plants, as previously found in mammalian cells. Measurements of the half-lives of waxy RNAs in transfected rice protoplasts indicated that the half-life of waxy RNA with a premature nonsense codon was 3.3 times shorter than that without a premature nonsense codon. Because the wild-type waxy transcripts, which are derived from the Wx b gene predominantly distributed among Japonica rice, have been shown to be less efficiently spliced and their alternative splicing has been documented, we examined whether these splicing properties influenced the efficiency of NMD. However, no effects were observed. These results established that NMD occurs in rice waxy RNA containing a premature nonsense codon.

We measured real-time spectra of light transmitted through SiO2 specimens during irradiation of amplified ultrashort laser with a fluence of 540 mJ/cm2. The real-time spectra exhibit a peak at around 400 nm, which significantly depends on the irradiation time. The observation and identification of defects were performed by measurements of electron spin resonance (ESR). Both dependences of the peak at around 400 nm on irradiation time and laser power are in good agreement with those of the ESR signal intensity of positively charged oxygen vacancies (E′ center). This strong correlation shows that self-trapped excitons are created followed by the formation of the E′ center and finally that of ESR inactive centers, namely, oxygen-deficiency centers.

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Photoreduction of anthraquinone (AQ) by triethylamine (TEA) in toluene and ethanol was studied by means of steady-state photolysis and laser photolysis. In toluene, addition of TEA enhanced the quantum yield of photoreduction of AQ, and the reaction was found to originate via the formation of an exciplex between ground-state TEA and the lowest triplet state of AQ: This exciplex changed to a contact ion pair followed by proton transfer, generating anthrasemiquinone radical and triethylamine radical, and 9,10-anthracenediol was obtained as the final photoproduct. Although the mechanism of the photoreduction of AQ in ethanol/TEA was essentially the same as that in toluene/TEA and the final products in ethanol/TEA were 9,10-anthracenediol and its anion, the quantum yield of photoreduction decreased with increase in TEA concentration. It was proposed that the exciplex in ethanol was quenched by ground-state TEA via the formation of a triplex of a radical anion of AQ and a radical cation of TEA dimer bonded by the three σ-electrons on two nitrogen atoms, based on the suggestion made by Hub et al. (J. Am. Chem. Soc., 106, 701 (1984); 106, 708 (1984)).

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