Synthesis of anatase-type TiO2 films by reactive laser ablation of a metallic Ti target in ambient O2 gas

TiO₂ films having anatase-type crystal structures were synthesized by reactive laser ablation of a metallic Ti target in ambient O₂ gas. The anatase-type TiO₂ was obtained at O₂ pressures below 0.2 Torr and at substrate temperatures above 150 °C. The films had the (101) orientation at substrate temperatures of 200–250 °C while, at substrate temperatures of 400–450 °C, the orientation of the films was (004). Rutile-type crystal was mixed in at substrate temperatures higher than 450 °C. The synthesis characteristics were compared with the fluxes of Ti, Ti⁺, and TiO toward the substrate, which were evaluated by laser-induced fluorescence imaging spectroscopy. PACS 81.15.Fg; 61.10.-i; 52.70.Kz     

Superconducting characteristics and microstructure of polycrystalline Zn-doped In2O3 films

In order to investigate the relation among the superconducting transition T_c, carrier density n, resistivity ρ and the microstructure in the polycrystalline (In₂O₃)_1?x–(ZnO)_x films, we prepared specimen films by post annealing of amorphous films with x = 0.025 at various annealing temperature T_a and for annealing time t_a = 1 h and 4 h. As for microstructures, we have investigated the distribution of elements by scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). We have found followings: (1) The annealed films clearly show the superconductivity of which T_c depends on T_a, t_a and n. This indicates that the superconductivity is determined by the combination of crystallinity and carrier density. (2) The data on STEM–EELS spectra mapping of indium plasmon indicate that droplets of the pure indium phase exist inside a film, where the distribution of these droplets dispersed. Therefore, it seems that droplets do not form an electrical conducting path, that is, it is possible that observed superconductivity is due to intrinsic characteristic of polycrystalline (In₂O₃)_1?x–(ZnO)_x films.     

Pulse width tunable subpicosecond pulse generation from an activelymodelocked monolithic MQW laser/MQW electroabsorption modulator

Actively modelocked pulses are generated from a 1.59 μm MQW laser integrated with an MQW electroabsorption modulator driven at the monolithic cavity frequency. The pulse width is controlled from 39 ps to 0.55 ps by changing the inverse bias voltage applied to the electroabsorption modulator and by linear pulse compression using a fibre     

New fiber-optic depolarizer

A new type of single mode fiber-optic depolarizer is proposed and demonstrated. The new depolarizer consists of a Mach-Zehnder interferometer with one arm used as a delay line with respect to the other. Light having a 100-MHz spectral width, for example, can be depolarized with high coupling efficiency to single mode fibers by using a polarization-maintaining fiber-delay line of a few meters in length.     

Application of ferrous-chromate and iodometric titration for the determination of copper oxidation states in the superconductor YBa2Cu3Oy

Summary Oxidation-reduction titration methods, Fe²⁺-Cr₂C ₇ ^2– and I^–-S₂O ₃ ^2– , were applied to the determination of the oxidation state of copper in the superconductor YBa₂Cu₃O _y , and related compounds. The former method presented problems in the sample dissolution and titration steps. The dissolution of the sample in low concentrations of Fe⁺-phosphoric acid and Fe²⁺-perchloric acid takes place in two steps, the oxidation of Fe²⁺ to Fe³⁺ and the liberation of oxygen gas, when the liberation results in low analytical values for Cu⁺. In addition the coexistence of cuprous ion and acids induces the oxidation of ferrous ion by dissolved oxygen and air. The problems were resolved by dissolution in 0.1 mol/l Fe²⁺-phosphoric acid and titration in an argon atmosphere. The latter method gave good results by controlling the amounts of potassium chloride, the concentration of acetic acid, and by elimination of the dissolved oxygen in acetic acid solution. The results of the two titration methods coincided with each other.

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Anwendung der Eisen(II)-Chromat- und der iodometrischen Titration zur Bestimmung der Oxidationsstufe des Kupfers im Supraleiter YBa₂Cu₃O _y

     

In vitro interaction between gingival fibroblasts and various root surfaces

The objective of the present in vitro study was to examine the effect of various root surface treatments on the initial attachment of gingival fibroblasts. Cultured fibroblasts were well spread and attached to demineralized dentin with citric acid, superficially curetted cementum, and root surface with periodontal ligament, while those on the planed dentin showed a poorly spread appearance. The first three root surfaces exhibited rough and irregular surface appearances with a well-developed filopodia and the latter root surface exhibited a smooth appearance, suggesting the texture of the root surface is closely associated with cell attachment. Interiorized collagen fibrils and numerous cytoplasmic vesicles were seen along the cell membrane of fibroblasts facing the root surfaces of the planed dentin, demineralized dentin, and superficially curetted cementum. Thus even the artificially exposed tooth surface with citric acid may be subjected to further alteration by fibroblasts.