Dithienosiloles (DTSs) bearing conjugated aryl substituents on the thiophene rings (1 and 2) were prepared and their optical, electrochemical, and electron-transporting properties were investigated in comparison with those of simple DTSs having no conjugated substituents on the thiophene rings (4-6). UV absorption bands of 1 and 2 are red shifted from those of 4-6 by 40-80 nm, reflecting the expanded π-conjugation, whereas the first oxidation peaks in the cyclic voltammograms of 1 and 2 appear at potentials a little lower or almost the same energies relative to those of 4-6, depending on the nature of the substituents. The electron-transporting properties of 1 and 2 were evaluated by the performance of electroluminescent (EL) devices having vapor-deposited DTS, Alq, and TPD layers, as the electrontransport, emitter, and hole-transport, respectively. The results indicated that introduction of aryl substituents to DTSs led to inferior performance of the devices in most cases, while the device with 1c bearing trimethylsilylpyridyl substituents exhibited high efficiency of current-luminance energy conversion and emitted a green light with a maximum luminance of 16 000 cd/m 2 . A trap-controlled electron transporting model is proposed to explain their performance. OM0103254 (14)

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Bioassay-directed isolation of the antitumor extract of Wikstroemia indica (Thymelaeaceae) has led to the characterization of tricin, kaempferol-3-O-beta-D-glucopyranoside, and (+)-nortrachelogenin as the major antileukemic constituents. In addition, daphnoretin was identified as the potent antitumor principle in vivo against the Ehrlich ascites carcinoma growth in mice.

The energy distributions of protons emitted from the Coulomb explosion of hydrogen clusters by an intense femtosecond laser have been experimentally obtained. Ten thousand hydrogen clusters were exploded, emitting 8.1 keV protons under laser irradiation of intensity 6ϫ10 16 W/cm 2. The energy distributions are interpreted well by a spherical uniform cluster analytical model. The maximum energy of the emitted protons can be characterized by cluster size and laser intensity. The laser intensity scale for the maximum proton energy, given by a spherical cluster Coulomb-explosion model, is in fairly good agreement with the experimental results obtained at a laser intensity of 10 16-10 17 W/cm 2 and also when extrapolated with the results of threedimensional particle simulations at 10 20-10 21 W/cm 2 .