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Ambipolar operation of fullerene field-effect transistors by semiconductor/metal interface modificationTransport properties of C 60 fullerene peapods and Gd@C 82 metallofullerene peapods are investigated by using the field effect in a gated structure. The results show that C 60 peapods exhibit unipolar p-type characteristics, whereas Gd@C 82 peapods show ambipolar both p-and n-type characteristics. This difference in transport behavior can be explained in terms of a bandgap narrowing of the peapods. One of the important findings is that tunable electronic properties of peapods are achieved by using the different types of encapsulated fullerene molecules.

SummaryThe presence of Plasmodium ovale has never been previously reported in Myanmar. Using blood samples obtained in many villages across the country between 1996 and 2000, molecular diagnosis of Plasmodium species was made with semi-or full-nested polymerase chain reaction (PCR) with speciesspecific primers, followed by agarose gel electrophoresis to detect amplification products. The presence of P. ovale was also confirmed with the another PCR-based diagnosis, the microtiterplate hybridization (MPH) method using species-specific probes. Both methods target the A type of the small subunit ribosomal RNA gene of the four human malaria parasites. Plasmodium ovale DNA was amplified in samples from 65 (4.9%) of 1323 PCR-positive patients, with perfect agreement between results obtained by nested PCR and MPH. Only four P. ovale-infected patients had single-species infection; all others were coinfected with P. falciparum, P. vivax and/or P. malariae. Quadruple infections were observed in six subjects. Parasites with typical P. ovale morphology were found in only 19 patients by conventional microscopy of Giemsa-stained thin smears or fluorescence microscopy of acridine orange-stained thin smears. Plasmodium ovale infections were found in villages situated in the southern, central and western regions of Myanmar, suggesting that P. ovale may be widely distributed in this country.

We have experimentally investigated the diameter dependence of Coulomb effects on the optical transition in semiconducting single-walled carbon nanotubes. The absorption band due to the lowest band-to-band transition shifts to the higher-energy side compared to the transition energy calculated by a tight-binding model. The blueshift originating from the Coulomb effect increases with decreasing tube diameter d as d Ϫ1.3. We have found that this dependence is attributed to both the increase of the band gap and the enhancement of the exciton binding energy with a decrease of the diameter.

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