10 Gbit/s, 100 km nonrepeatered fibre transmission experiment using a high-sensitivity semiconductor optical preamplifier

10 Gbit/s, 100 km nonrepeated fibre transmission has been demonstrated using a high-sensitivity receiver with two-stage cascade-connected semiconductor optical amplifiers and a pin PD front end. The sensitivity and its improvement were -23.5 dBm and 12.2 dB respectively, resulting in the allowable span-loss of 24.5 dB.<>     

ZnO/SiO2-diaphragm composite resonator on a silicon wafer

We report on a thickness-extensional-mode piezoelectric resonator consisting of a ZnO/SiO2 diaphragm supported by a silicon wafer. It is found that the temperature coefficient of frequency can be reduced to zero by adjusting the ZnO/SiO2 thickness ratio. A temperature coefficient of frequency as low as 10 ppm/°C was experimentally obtained.     

Supersolidity and Disorder in Solid Helium 4

Supersolidity is a rather controversial issue which has been revived recently by a number of torsional oscillator (ac-rotation) experiments with solid helium 4. One possibility would be that the ground state of helium 4 crystals contains a Bose-Einstein condensate of mobile vacancies. However, the supersolid signal was shown to depend on sample history. In addition, dc-flow experiments show that superfluid transport of mass does not occur in solid helium, except if it contains appropriate grain boundaries. As a consequence, we believe that supersolidity is not an intrinsic property of helium single crystals, but that it is due to quenched disorder. We report experiments on pressure relaxation in and light scattering from solid samples, that give additional evidence for the existence of disorder in helium crystals. We also describe our recent study of the wetting properties of grain boundaries.      

Formation process of Al2O3 thin film by reactive sputtering

Al and Al₂O₃ films were deposited by RF magnetron sputtering using a mixed gas of Ar and O₂. The surface of the Al target was changed from the metallic mode to the oxide mode at a critical O₂ flow ratio of 8%. The atomic ratio of sputtered Al atoms to supplied oxygen atoms was found to be approximately 2:3 at the critical O₂ flow ratio. The oxide layer thickness formed on the Al target was estimated to be 5-7 nm at an O₂ flow ratio of 100% by ellipsometry.     

Ion conducting properties of hydrogen-containing Ta2O5 thin films prepared by reactive sputtering

Hydrogen-containing Ta₂O₅ (Ta₂O₅:H) thin films are considered to be a candidate for a proton-conducting solid-oxide electrolyte. In this study, Ta₂O₅:H thin films were prepared by reactively sputtering a Ta metal target in an O₂ + H₂O mixed gas. The effects of sputtering power and post-deposition heat treatment on the ion conducting properties of the Ta₂O₅:H thin films were studied. The ionic conductivity of the films was improved by decreasing the RF power and a maximum conductivity of 2 × 10⁻⁹ S/cm was obtained at an RF power of 20 W. The ionic conductivity decreased by heat-treatment in air, and no ion-conduction was observed after treatment at 300 °C due to the decrease in hydrogen content in the films.     

Direct fabrication of nanoscale bio-adhesive patterns by electron beam surface modification of plasma polymerized poly ethylene oxide-like coatings

In this study we present a method to produce nanostructured surfaces containing bio-adhesive features inside a non bio-adhesive matrix. The strategy is based on the combination of low pressure plasma polymerization and electron beam lithography processes and allows the fabrication of the structured materials in just two steps without using any solvents. In a first step, a thin protein-and-cell-repelling coating (～10?nm) is obtained by plasma polymerization of Di-glyme. Then, in a second step, the bio-adhesive properties of the layer are tuned by monitoring the concentration of ether bonds of the film by irradiating it locally by different irradiation doses with an electron beam. Time-of-flight secondary ion mass spectroscopy and atomic force microscopy analysis have been used to characterize the produced surfaces. Experiments with a model protein (bovine serum albumin) on the patterned surfaces show preferential adhesion to the irradiated regions, indicating the potential of this simple technique for the development of highly compacted sensitive bio-sensing devices.     

Reduction of lipophilicity at the lipophilic domain of RXR agonists enables production of subtype preference: RXRalpha-preferential agonist possessing a sulfonamide moiety

Retinoid X receptor agonists (RXR agonists, rexinoids) are interesting candidates for the treatment of cancers such as tamoxifen-resistant breast cancer and taxol-resistant lung cancer. However, well-known RXR agonists possess a strong lipophilic character. In addition, although RXR has three subtypes, no subtype-selective RXR agonists are known. Thus we aimed to produce less-lipophilic and subtype-selective RXR agonists. By designing sulfonamide-type RXR agonists, 4-[N-methanesulfonyl-N-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-2-naphthyl)amino]benzoic acid (8 a) was found to prefer RXRalpha over RXRbeta and RXRgamma, although the potency is less than the potencies of well-known RXR pan-agonists. Moreover, our results suggest that the reduction of lipophilicity at the hydrophobic interaction region of RXR agonists enables production of RXR subtype preference. Our finding will be useful for the creation of more potent and less-lipophilic subtype-selective RXR agonists aimed at the reduction of undesirable side effects.     

Tribological properties of Fe7Mo6-based alloy under two ionic liquid lubrications

The tribological properties of Fe₇Mo₆-based alloy, Mo, Fe and ASTM class no. 45 cast iron disk specimens were investigated against ASTM 52100 steel balls under the lubrication of two different kinds of hydrophobic ionic liquid: N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI) and N-N-N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI). When lubricated with PP13-TFSI or TMPA-TFSI, the Fe₇Mo₆-based alloy disk specimens exhibited lower friction coefficients and lower wear rates than the Mo, Fe and ASTM class no. 45 cast iron disk specimens. The low friction coefficients and low wear rates of the Fe₇Mo₆-based alloy were considered to be caused by the formation of low friction materials such as MoO₃ and FeSO₄ on the worn surface.