Ab initio calculations are performed to elucidate the mechanism of the photoisomerization of azobenzene. We obtain the excitation energies of the S1(n→π*), S2(π→π*), and S3(n2→π*2) states by complete active space self-consistent field (CASSCF) and multireference single double configuration interaction (MRSDCI) calculations. Two-dimensional potential surfaces of the ground- and excited states are obtained at the CASSCF level in order to investigate the isomerization pathways. A conical intersection between the ground state and the S1 state is found near the midpoint of the rotation pathway, and causes a radiationless transition. On the other hand, the S2 state has local minima at the cis and trans structures, so that the isomerization proceeds at the S2 surface following the deexcitation.

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Photoisomerization mechanism of azobenzene in the lowest excited state S 1 ͑n ‫ء‬ ͒ is investigated by ab initio molecular dynamics ͑AIMD͒ simulation with the RATTLE algorithm, based on the state-averaged complete active space self-consistent field method. AIMD simulations show that cis to trans isomerization occurs via two-step rotation mechanism, accompanying rotations of the central NN part and two phenyl rings, and this process can be classified into two types, namely, clockwise and counterclockwise rotation pathways. On the other hand, trans to cis isomerization occurs via conventional rotation pathway where two phenyl rings rotate around the NN bond. The quantum yields are calculated to be 0.45 and 0.28Ϯ 0.14 for cis to trans and trans to cis photoisomerizations, respectively, which are in very good agreement with the corresponding experimental results.

An unknown cytotoxin was identified in the culture supernatant of Clostridium perfringens type C. The cytotoxin, named TpeL, which was purified using mAb-based affinity chromatography, had a lethal activity of 62 minimum lethal dose (MLD) mg "1 in mice and a cytotoxic activity of 6.2610 5 cytotoxic units (CU) mg "1 in Vero cells. The nucleotide sequence of TpeL was determined. The entire ORF had a length of 4953 bases, and the same nucleotide sequence was not recorded in the GenBank/EMBL/DDBJ databases. The molecular mass calculated from the deduced amino acid sequence was 191 kDa, and a signal peptide region was not found within the ORF. The deduced amino acid sequence exhibited 30-39 % homology to Clostridium difficile toxins A (TcdA) and B (TcdB), Clostridium sordellii lethal toxin (TcsL) and Clostridium novyi alpha-toxin (TcnA). The amino acid sequence of TpeL is shorter than these toxins, and the homologous region was located at the N-terminal site. Eighteen strains of C. perfringens types A, B and C were surveyed for the presence of the tpeL gene by PCR. The tpeL gene was detected in all type B (one strain) and C strains (five strains), but not in any type A strains (12 strains). TpeL was detected in culture filtrates of the five type C strains by dot-blot analysis, but not in the type B strain. It was concluded that TpeL is a novel toxin similar to the known large clostridial cytotoxins. Furthermore, the data indicated that TpeL is produced by many C. perfringens type C strains.

Early-warning systems for natural disasters are important tools for disaster risk reduction and for achieving sustainable development and livelihoods. In 2005, the Japanese government initiated a new nationwide early-warning system for landslides disasters. The main methodology of the system is to set a criterion for occurrences of debris flows and slope failures based on several rainfall indices (60-min cumulative rainfall and soil-water index) in each 5-km grid mesh covering all of Japan. Because many of the records of mass movements are lacking in scientific precision on timing and location, the system applies Radial Basis Function Network methods to set the criterion based primarily on rainfall data recorded as not triggering disasters. Since the end of March 2007, under torrential rainfall conditions, early-warning information has been disseminated as part of weather news using TV, radio, and the Internet. Because of the increasing worldwide recognition of the importance of early-warning systems for natural disaster reduction, the aim of this article is to introduce the new Japanese early-warning system to the international landslide community. In this article, the method, the system, and the result of its application to landslide disasters in 2009 are presented.