Silica waveguides on silicon and their application to integrated-optic components

A marriage of optical fibre fabrication technology and LSI microfabrication technology gave birth to fibre-matched silica waveguides on silicon: thick glass layers of high-silica-content glass are deposited on silicon by flame hydrolysis, a method originally developed for fibre preform fabrication. Silica channel waveguides are then formed by photolithographic pattern definition processes followed by reactive ion etching. This high silica (HiS) technology offers the possibility of integrating a number of passive functions on a single silicon chip, as well as the possibility of the hybrid integration of both active and passive devices on silicon. This paper reviews the NTT HiS technology and its application to integrated-optic components such as optical beam splitters, optical switches, wavelength-division multi/demultiplexers and optical frequency-division multi/demultiplexers. The clear and simple waveguide structures produced by the HiS technology make it possible to design and fabricate these components with high precision and excellent reproducibility.  

Sonophotocatalytic decomposition of water using TiO(2) photocatalyst

Sonophotocatalytic reaction is a photocatalytic reaction with ultrasonic irradiation or the simultaneous irradiation of ultrasound and light with a photocatalyst. The possibility of the effect of hybrid of sonochemical and photocatalytic reactions was examined. Liquid water was hardly decomposed to H(2) and O(2) by photocatalysis or sonolysis, independently. In order to decompose water, powdered TiO(2) photocatalyst suspended in distilled water should be simultaneously irradiated by light and ultrasound. This sonophotocatalytic reaction was effective on the decomposition of water to H(2) and O(2).  

Materials science of Mg-Ni-based new hydrides

One of the advantageous functional properties of Mg alloys (or compounds) is to exhibit the reversible hydriding reaction. In this paper, we present our systematic studies regarding the relationship between nanometer- or atomistic-scale structures and the specific hydriding properties of the Mg-Ni binary system, such as(1) nanostructured (n)-Mg₂Ni, (2) a mixture of n-Mg₂Ni and amorphous (a)-MgNi,(3) pure a-MgNi, and(4) n-MgNi₂. Further studies on(5) an a-MgNi-based system for clarifying the effect of the short-range ordering on the structural and hydriding properties and(6) a MgNi₂-based system for synthesizing the new Laves phase structure are also presented. The materials science of Mg-Ni-based new hydrides will provide indispensable knowledge for practically developing the Mg alloys as hydrogen-storage materials. Received: 14 August 2000 / Accepted: 6 November 2000 / Published online: 9 February 2001  

Evidence against singlet oxygen formation by sonolysis of aqueous oxygen-saturated solutions of Hematoporphyrin and rose bengal. The mechanism of sonodynamic therapy

The possible role of singlet oxygen in the mechanism of sonodynamic therapy, the synergistic effect of ultrasound and certain sonosensitizers, was investigated. We used 4,4'-bis(1-p-carboxyphenyl-3- methyl-5-hydroxyl)-pyrazole (DRD 156), a sensitive new reagent which reacts specifically with singlet oxygen (1O2) but not with OH radicals, superoxide anion radicals or H2O2, to produce an EPR detectable signal. Sonolysis (48 kHz) of 90% D2O oxygen-saturated PBS solutions of Hematoporphyrin or Rose Bengal did not lead to the formation of detectable EPR signals of the semiquinone radical of DRD156. In contrast, the EPR signal of the semiquinone radical of DRD156 was observed during photoirradiation of Hematoporphyrin at 505 nm or of Rose Bengal at 544 nm. These results are inconsistent with a major role for singlet oxygen formation in the sonolysis of aqueous solutions of these compounds. An alternative mechanism for sonodynamic therapy involving peroxyl and alkoxyl radicals is discussed.  

Optical properties and highly efficient laser oscillation of Nd:YAG ceramics

Optical absorption, emission spectra have been measured for polycrystalline Nd-doped Y₃Al₅O₁₂ ceramics. Fluorescence lifetimes of 257.6 μs, 237.6 μs, 184.2 μs and 95.6 μs have been obtained for 0.6%, 1%, 2% and 4% neodymium-doped YAG ceramics, respectively. For the first time, highly efficient laser oscillation at 1064 nm has been obtained with this kind of ceramics. Slope efficiency of 53% has been achieved on a uncoated 4.8-mm thick 1% Nd:YAG ceramics sample. Optical to optical conversion efficiency is 47.6%. Laser oscillation has also been obtained with a 2% Nd:YAG ceramics. The optical properties and laser output results have been compared with that of Nd:YAG single crystal grown by the Czochralski method. Almost identical results have been achieved including laser experiments results. But fabrication of Nd:YAG ceramics is much easier compared to the single-crystal growth method. And also large size (now of about 400 mm diameter×5 mm is available) and high-concentration (>1%) Nd:YAG ceramics can be fabricated. The results show that this kind of Nd:YAG ceramics is a very good alternative to Nd:YAG single crystal. Received: 20 April 2000 / Published online: 16 August 2000  

A non-fused fiber coupler for side-pumping of double-clad fiber lasers

A non-fused fiber coupler is demonstrated for side-pumping of the double-clad fiber (DCF) lasers by adhesive techniques. The fiber coupler is fabricated by adhering an angularly polished single-clad fiber (SCF) to the inner cladding of the DCF. The pumping light is launched from the SCF by total inner reflection. Coupling coefficient as a function of coupling angle, bend distance, and backward scattering is investigated. The field distribution in DCF is also discussed.  

Diagnosis of discoid lateral meniscus of the knee on MR imaging

To establish the quantitative MR diagnostic criteria for discoid lateral meniscus, MR imaging of 60 knees with arthroscopically confirmed discoid lateral menisci and 134 knees with semilunar lateral menisci were analyzed. Following four quantitative parameters were measured. (1) Meniscal width (MW): The minimum meniscal width on the coronal slice. (2) Ratio of the meniscus to the tibia (RMT): The ratio of minimum meniscal width to maximum tibial width on the coronal slice. (3) Percent coverage of the meniscus (PCM): The ratio of the sum of the width of the anterior and posterior horns to the meniscal diameter on the sagittal slice showing the maximum meniscal diameter. (4) Continuity of the anterior and posterior horns (CAPH): The number of consecutive sagittal slices showing continuity between the anterior and posterior horns of the meniscus on the sagittal slice. The cut-off values of each parameter to discriminate between the discoid and semilunar meniscus were calculated based on a univariate logistic regression analysis. The sensitivity and specificity were also calculated for each of 4 parameters and combinations of these parameters. The cut-off value was 15 mm for the MW, 20% for the RMT, 75% for the PCM, and 3 slices for the CAPH. The sensitivity and specificity of the four parameters ranged between 87% and 50% and between 99% and 92%, respectively. The most accurate diagnostic criterion was either the RMT > or = 20% or the PCM > or = 75%, and the sensitivity and specificity were 95% and 97%, respectively, even when torn menisci were included.  

Sonolytic degradation of hazardous organic compounds in aqueous solution

Benzene, chlorobenzene, 1,2-, 1,3-, 1,4-dichlorobenzene, biphenyl, and polychlorinated biphenyls such as 2-, 4-chlorobiphenyl and 2,2′-dichlorobiphenyl in aqueous solutions have been subjected to sonolysis with 200 kHz ultrasound at an intensity of 6 W cm⁻² under an argon atmosphere. 80–90% of initial amount of these compounds were degraded by 30–60 min of sonication when the initial concentrations were 10–100 μmol l⁻¹. The degradation rate of these compounds increased with increase in their vapor pressures. In all cases of sonolysis of chlorinated organic compounds, an appreciable amount of liberated chloride ion was observed.  

Three-dimensional microscopy with phase-shifting digital holography

We applied phase-shifting digital holography to microscopy by deriving the complex amplitude of light scattered from microscopic three-dimensional objects through a microscope objective by video camera recording, phase-shifting analysis, and computer reconstruction. This method requires no mechanical movement and provides a flexible display and quantitative evaluation of the reconstructed images. A theory of image formation and experimental verification with specimens are described.  

Molecular and functional diversity of vascular endothelial growth factors

Summary Members of the vascular endothelial growth factor (VEGF) family are crucial regulators of neovascularization and are classified as cystine knot growth factors that specifically bind cellular receptor tyrosine kinases VEGFR-1, VEGFR-2, and VEGFR-3 with high but variable affinity and selectivity. The VEGF family has recently been expanded and currently comprises seven members: VEGF-A, VEGF-B, placenta growth factor (PlGF), VEGF-C, VEGF-D, viral VEGF (also known as VEGF-E), and snake venom VEGF (also known as VEGF-F). Although all members are structurally homologous, there is molecular diversity among the subtypes, and several isoforms, such as VEGF-A, VEGF-B, and PlGF, are generated by alternative exon splicing. These splicing isoforms exhibit differing properties, particularly in binding to co-receptor neuropilins and heparin. VEGF family proteins play multiple physiological roles, such as angiogenesis and lymphangiogenesis, while exogenous members (viral and snake venom VEGFs) display activities that are unique in physiology and function. This review will highlight the molecular and functional diversity of VEGF family proteins.