Controlling the morphology of Ag nanoclusters by ion implantation to different doses and subsequent annealing

Ag ions were implanted at 200 keV into silica with nominal doses ranging from 5x10(16) to 2x10(17) ions/cm2. We find that nanovoid-containing Ag nanoclusters form in the implanted samples with doses higher than 1x10(17) ions/cm2. When the dose is increased to 2x10(17) ions/cm2, the nanovoids gradually shrink and form a sandwiched nanocluster-nanovoid-nanocluster structure. The evolution of sandwiched nanoclusters during annealing was observed by in situ transmission electron microscopy experiments. Potential mechanisms for the formation and evolution of the irradiation-induced nanovoids and the sandwiched structure nanoclusters with increasing doses are discussed. The structural optimization of the sandwiched structure nanoclusters was performed by molecular mechanics calculations.     

Basic study on apoptosis induction into cancer cells U-937 and EL-4 by ultrasound exposure

Recently, the low invasive cancer treatments with small aftereffects have been considered. We are studying on the suppression methods of cancer cell proliferation with ultrasound. Cancer cells of mouse T lymphoma (EL-4) have been used in our study. The human histitocytic lymphoma cells (U-937) was used in this time. The cancer cells were cultured in a culture medium of RPMI1640. The standing wave acoustic field was formed in a water tank of our ultrasound exposure system by a vibrating plate driven with a Langevine type transducer. The U-937 and EL-4 were exposed to ultrasound in the acoustic field with spatial average acoustic intensity of 350 mW/cm(2) at 150 kHz. The viable rate of EL-4 decreased with the lapse of culture time after ultrasound exposure. U-937 did not show the remarkable decrease tendency. The proliferation of U-937 which exposed to ultrasound with 700 mW/cm(2) was suppressed. It can be thought that apoptosis was induced in the cancer cells in this condition. We observed the morphological change on the U-937 exposed to ultrasound with this condition. The morphological changes by apoptosis like the shrink of cells, formation of apoptotic bodies etc. can be observed with an optical microscope and a phase contrast microscope.     

Atomic structure and stability of elliptical carbon onion

Elliptical carbon onions were produced from amorphous carbon by electron beam irradiation. Atomic structure and structural stability of the onion were investigated by high-resolution electron microscopy, molecular mechanics calculation and molecular orbital calculation, and a structure model of C₂₄@ C₈₄ was proposed at the center of the elliptical onion. Received 30 November 2000