Conductivity and field effect transistor of La2@C80 metallofullerene

We first demonstrate a field-effect-transistor operation of dimetallofullerene La2@C80 with the icosahedral cage symmetry. The thin-film device showed an n-type behavior with a mobility of 1.1 x 10-4 cm2/V s at room temperature under high vacuum. Taking the nature of LUMO into account, the n-type behavior indicates an occurrence of carrier conduction through encapsulated La ions. The low mobility, suggesting an intermolecular hopping mechanism, is ascribed to the intrinsic and extrinsic reasons, which are discussed in the text.     

Polarization reversal in multiferroic TbMnO3 with a rotating magnetic field direction

For the memory application of magnetoelectric multiferroics, not only bistability (i.e., ferroelectricity) but also the switching of the polarization direction with some noneverlasting stimulus is necessary. Here, we report a novel method for the electric polarization reversal in TbMnO3 without the application of an electric field or heat. The direction of the magnetic-field-induced polarization along the a axis (Pa) is memorized even in the zero field where Pa is absent. The polarization direction can be reversed by rotating the magnetic-field direction in the ab plane.     

Elucidation of sulfur mobility on Cr, Mo and W-based catalysts in hydrodesulfurization using a35S pulse tracer method

In hydrodesulfurization of radioactive³⁵S-labeled dibenzothiophene catalyzed by CrO₃/Al₂O₃, it was found that sulfur on sulfided CrO₃/Al₂O₃ was more labile than those on MoO₃/Al₂O₃ and WO₃/Al₂O₃, while the amount of sulfur was less than that on MoO₃/Al₂O₃. Dedicated to Professor Pál Tétényi on the occasion of his 70th birthday     

Suppressing chromatic dispersion fluctuation for broadband optical parametric gain in highly nonlinear tellurite microstructured optical fibers

Optical Review - We investigate the effect of chromatic dispersion fluctuation on the performance of fiber optical parametric amplification (FOPA) using tellurite hybrid microstructured optical...     

Aggregation modeling of calcium carbonate particles by Monte Carlo simulation

The mechanism on aggregation of spindle granular particles of calcite was investigated for the carbonation of calcium hydroxide in aqueous suspension for the purpose of controlling morphology of CaCO₃. The experimental carbonation process was carried out in a semi-batch bubble column reactor under different conditions. Although, fine rhombic nano-particles diameter ranged from 100 to 200 nm were obtained at 291 K, a higher temperature of 300 K provided spindle granular particles with a length of 1.0–1.5 μm and a width of 0.3–0.5 μm. The average crystallite size was 28 nm for the fine rhombic nano-particles and 43 nm for the spindle granules. Zeta potential measurement for the spindle granules indicated that the suspension tended to be aggregated during the carbonation process. The effect of the degree of particle aggregation on the shape of the obtained calcite particles was studied by Monte Carlo simulations. Our simulation results elucidated the dependence of aggregation on unit particles, i.e., primary particles, on the experiment carbonation condition where the spindle granules were formed out of the unit particles under the same condition as the experiments. In addition, the formation mechanism of the granules was investigated by applying classical nucleation theory to the present simulations.     

Unusual transannular cyclization products of sarcophytoxide, a 14-membered marine cembranoid: anomalous stereochemistry of epoxide-ketone rearrangement

[reaction: see text] Treatment of sarcophytoxide with trimethylsilyl trifluoromethanesulfonate afforded an aromatic ketone as an unusual cyclization product. The modified Mosher's method and X-ray analysis performed on the aromatic ketone revealed that it is a 4:1 mixture of 8(R)- and 8(S)-enantiomers. It also suggested that the precursor ketone has 8(R)-configuration, which is contradictory to that expected from the ordinary epoxide-ketone rearrangement.     

Hydrogen adsorption and desorption in carbon nanotube systems and its mechanisms

The hydrogen physisorption properties in single-walled carbon nanotube (SWNT) based materials were characterized. The SWNTs were highly purified and three useful pores for hydrogen physisorption were activated. Hydrogen was physisorbed in intra-tube pores at room temperature and the capacity was estimated to be about 0.3–0.4 wt.% at room temperature. The adsorption capacity can be explained by the Langmuir model. The intra-tube pores have large adsorption potential and this induces hydrogen physisorption at comparatively higher temperatures. This fact indicates the importance of fabricating sub-nanometer ordered pores for this phenomena. PACS 51.30.+i; 51.90.+r; 81.05.Tp; 81.07.De