Directional coupler switch with reduced voltage-length product

The phase change×interaction length product needed to switch a directional coupler is shown to be reduced by decreasing the coupling coefficient at the middle of the interaction region. To implement the structure with parallel waveguides, an additional fabrication process to produce the low index region was needed. Instead of reducing the index, enlarging the waveguide gap can be used to decrease the coupling coefficient to gain the same effect. To reduce the coupling coefficient at the middle of the interaction region, the gap between waveguides was gradually enlarged from both ends to the center. To simplify the fabrication processes, the varied waveguide gap structure was used. The single-mode waveguides were fabricated on z cut LiNbO₃ by in-diffusing 7-μm-wide ti. The design, fabrication, and measurements are discussed     

Low temperature growth of sol-gel SrBi2Ta2O9 thin films by low-pressure annealing

A new low-temperature processing method to prepare SrBi₂Ta₂O₉ thin films is proposed. These thin films were prepared on Pt/Ta/SiO₂/Si substrates by a sol-gel method, and their structural and electrical properties were investigated. Films were annealed before and after the top Pt electrode deposition. The first annealing was performed in a 760-Torr oxygen atmosphere at 600 °C for 30 min, and the second annealing was performed in a 5-Torr oxygen atmosphere at 600 °C for 30 min. The films were well crystallized and fine-grained after the second annealing. The electrical characteristics of the 200-nm-thick film obtained by this new process were as follows: remanent polarization, P_r = 8.5 μC/cm²; coercive field, E_c = 36 kV/cm; and leakage current density, I_L = 1 × 10⁻⁷ A/cm² (at 150 kV/cm). This process is very attractive for highly integrated ferroelectric nonvolatile memory applications. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 27–33, 1997     

Preparation of highly acidic hydrated niobium oxide

In order to obtain a highly acidic hydrated niobium oxide, the preparation methods and conditions such as niobium precursors, precipitating reagents, treatment of precipitates, washing of precipitates, final pH in precipitation, and calcination temperature were systematically examined. Strong acidic sites of H₀−8.2 were found to appear on hydrated niobium oxide when the oxide was prepared by boiling the precipitates, which were obtained by hydrolysis of niobium oxalate with KOH, in a diluted mild acid solution(preferably 0.1N HNO₃) followed by washing with hot water several times and heating in air at 300 °C. Final pH in the precipitation must be below 11.     

Low drive voltage Y-branch digital optical switch

A Y-branch digital optical switch with reduced drive voltage and low crosstalk is reported. The local full branch angle of separating waveguides is decreased from the branching point to the end of the branch.<>     

Three-guide directional coupler as polarisation independent optical switch

The polarisation independent directional coupler switch with three coupled waveguides is demonstrated. The device exhibits improved voltage tolerance over existing designs.<>     

Catalytic activities of niobium oxide for the liquid-phase hydrogenation of maleic anhydride and hydration of succinonitrile

Co and Pd supported on Nb₂O₅ catalyst was active for the hydrogenation of maleic anhydride to γ-butyrolactone and tetrahydrofuran in the liquid-phase. The catalyst was more active than Co and Pd supported on diatomaceous earth, SiO₂ and Al₂O₃. Co and Pd seem to be stable on Nb₂O₅.

Nb₂O₅ · nH₂O was active for the hydration of succinonitrile to β-cyanopropionamide, that is an intermediate for -pyrrolidone, in the liquid-phase. Niobium oxide showed unique catalytic activities, especially, in the presence of water.     

Metformin Protects against NMDA-Induced Retinal Injury through the MEK/ERK Signaling Pathway in Rats

Metformin, an anti-hyperglycemic drug of the biguanide class, exerts positive effects in several non-diabetes-related diseases. In this study, we aimed to examine the protective effects of metformin against N-methyl-D-aspartic acid (NMDA)-induced excitotoxic retinal damage in rats and determine the mechanisms of its protective effects. Male Sprague–Dawley rats (7 to 9 weeks old) were used in this study. Following intravitreal injection of NMDA (200 nmol/eye), the number of neuronal cells in the ganglion cell layer and parvalbumin-positive amacrine cells decreased, whereas the number of CD45-positive leukocytes and Iba1-positive microglia increased. Metformin attenuated these NMDA-induced responses. The neuroprotective effect of metformin was abolished by compound C, an inhibitor of AMP-activated protein kinase (AMPK). The AMPK activator, AICAR, exerted a neuroprotective effect in NMDA-induced retinal injury. The MEK1/2 inhibitor, U0126, reduced the neuroprotective effect of metformin. These results suggest that metformin protects against NMDA-induced retinal neurotoxicity through activation of the AMPK and MEK/extracellular signal-regulated kinase (ERK) signaling pathways. This neuroprotective effect could be partially attributable to the inhibitory effects on inflammatory responses.     

Activation of propane and butanes over niobium- and tantalum-based oxide catalysts

Niobium and tantalum are important elements for the activation of alkanes in the viewpoints of acidic property and the formation of unique mixed metal oxides. And the difference of the ability of alkane activation between niobium- and tantalum-based oxide catalysts is studied. Although hydrated niobium and tantalum oxides show strong acid property, only hydrated tantalum oxide is activated to a solid superacid by the treatment with sulfuric acid, and isomerizes n-butane to isobutane at room temperature. The sulfuric acid treated tantalum oxide activates P–Mo–V heteropolyacid compounds for the selective oxidation of isobutane to methacrolein (MAL) and methacrylic acid (MAA). The difference of ability of alkanes activation between niobium and tantalum is studied by using surface science technique. Mo–V–Nb–Te mixed metal oxide catalysts are active for the ammoxidation of propane to acrylonitrile (AN). However, Mo–V–Ta–Te mixed metal oxide is less active. The effect of catalyst preparation condition is studied. Mo–V–Nb–Te mixed metal oxide catalysts are also active for the oxidation of propane to acrylic acid (AA).     

Scalability analysis of diffractive optical element-based free-space photonic circuits for interoptoelectronic chip interconnections

An interchip free-space optical interconnection module is investigated to solve the pin-input-output bottleneck at the interface of silicon integrated circuits. The scalability of the photonic circuit is theoretically analyzed by use of the minimum feature size requirement of each diffractive element used. The study showed that interconnection densities of 1000-2000 channels/cm is possible for a 40-mm interconnection length with a 3-mm-thick optical substrate. Diffraction-limited imaging capability has been demonstrated using a fabricated prototype, confirming its applicability for interchip free-space interconnections. Photonic circuit insertion losses of -23.4 dB for TE polarization and -25.9 dB for TM polarization as well as a polarization-dependent loss of 2.5 dB are found to be caused primarily by a pair of binary linear gratings used for beam deflections. Design modifications aiming at insertion loss reduction and further improvement of tolerance capabilities are also discussed.     

A study on the preparation of supported metal oxide catalysts using JRC-reference catalysts. I. Preparation of a molybdena–alumina catalyst. Part 2. Volume of an impregnation solution

Ten types of 13 wt% MoO₃/Al₂O₃ catalysts were prepared by a conventional impregnation or equilibrium adsorption method using a common extrudate support. These catalysts were subjected to a comprehensive characterization and catalytic reactions to find important preparation parameters in practical preparations. It was demonstrated in the present group study that the formation of crystalline MoO₃ was strongly correlated with the Mo segregation on the outer surface of the extrudate. When the amount of the impregnation solution was large (ca. 10 cm³ g-Al₂O₃⁻¹), a considerably homogeneous distribution and high dispersion of Mo oxide species were attained irrespective of the other preparation parameters. It is suggested that when a pore volume impregnation or incipient wetness technique is employed, drying processes strongly affect the dispersion and distribution of Mo oxide species. Drying at a reduced pressure is suggested to result in a segregation of Mo oxides on the outer surface of the extrudate, and accordingly a formation of crystalline MoO₃.