Determination of 1,5-anhydro-D-glucitol on the basis of its inhibitory effect on trehalase activity

1,5-Anhydro-D-glucitol (1,5-AG) was found to inhibit trehalase and trehalose phosphorylase activities competitively, because of its structural similarity with D-glucose. Trehalase from Nocardia sp., one of the most 1,5-AG-sensitive enzymes, was used in the determination of 1,5-AG concentration, which is a useful marker for the diagnosis of diabetes. A good linear relationship was observed between 1,5-AG concentration in the range of 0.02 to 1.0 mM and the extent of trehalase inhibition by 1,5-AG. The 1,5-AG concentration range could be determined by estimating enzymatically the amount of the reaction product, D-glucose, produced by the trehalase.     

Optical coherent broad-band transmission for long-haul anddistribution systems using subcarrier multiplexing

Signal multiplexing techniques for coherent optical transmission are compared, and appropriate application for a coherent subcarrier multiplexing (SCM) system is discussed. Optical frequency modulation (FM) using direct modulation of a distributed-feedback laser diode (DFB-LD) and a heterodyne detection is shown to be feasible. A transmission system using a local laser in the transmitter is unaffected by polarization and is cost effective. Phase noise can be suppressed by a phase-noise-canceling circuit (PNC) in a heterodyne receiver. This circuit can also effectively compensate for the frequency of instability of light sources. A theoretical simulation of a coherent SCM system showed that 100 channels of 30-MHz FM signal or 15 channels of 155-Mb/s signal can be distributed to 10000 subscribers using single-stage or double-stage optical amplifiers     

Channel allocation and crosstalk penalty in coherent opticalfrequency division multiplexing systems

Theoretically studies the crosstalk penalty of coherent optical frequency division multiplexing systems by varying the intermediate frequency and the channel spacing. Results, applicable to ASK, PSK and CPFSK modulation formats, provide a quantitative criterion for designing a practical multichannel coherent lightwave system     

Theoretical and experimental study of self-filtering effect inconcatenated erbium-doped fiber amplifiers

This paper describes the self-filtering effect which appears in concatenated erbium-doped fiber amplifier (EDFA) systems. Employing a theoretical model we observed how the self-filtering wavelength is affected by the variation of some EDFA parameters, such as gain, fiber composition, pump wavelength and temperature. By a recirculating loop experiment which simulates a concatenated repeater transmission system, we measured the evolution of the amplified spontaneous emission (ASE) spectra with the number of circulations, and with the loss of the loop. We found a good agreement between the theoretical simulations and the experiments     

Adhesive Catalyst Immobilization of Palladium Nanoparticles on Cotton and Filter Paper: Applications to Reusable Catalysts for Sequential Catalytic Reactions

Palladium nanoparticles dispersed in ammonium salts of hyperbranched polystyrenes are adhesively immobilized on the surface of cotton or filter papers by simply heating with dicarboxylic acids or halide anions. The resulting Pd@cotton and Pd@filter paper behave as reusable catalysts; in particular, Pd@filter paper is useful as catalyst for application to sequential cross‐coupling and hydrogenation reactions to produce several different products with just one piece of the paper catalyst.

     

Power penalty analysis due to polarisation diversity on 1.2 Gbit/s optical DPSK heterodyne transmission

An optical DPSK transmission experiment was performed over 100 km at a bit rate of 1.2 Gbit/s using a dual-balanced polarisation-diversity receiver. A high receiver sensitivity of less than -42.8 dBm was achieved and the power penalty due to polarisation diversity was analysed.<>     

Optical heterodyne image-rejection receiver for high-densityoptical frequency division multiplexing system

An optical heterodyne image-rejection receiver (IRR) for high-density optical frequency division multiplexing (OFDM) systems is described. The IRR was realized using balanced receivers, which showed more than 18-dB suppression over the 1.5-3.0-GHz IF region. Measured crosstalk penalties in a two-channel 560 Mb/s differential phase-shift keyed (DPSK) heterodyne optical communication system were realized for the first time. The crosstalk penalties in an OFDM system are estimated theoretically with and without the IRR. The required channel spacing and number of channels that can be accommodated in the 10-nm tuning range of the local laser are presented. A particular configuration of the IRR, its operation, and its performance limitations are discussed. The experimental results for image-rejection reception in a two-channel 560-Mb/s DPSK system are also given. Crosstalk penalties are estimated experimentally and compared to the theoretical calculation. Since the conventional configurations of the IRR are very sensitive to the polarization fluctuation of the transmitted signals, polarization-insensitive IRRs are proposed and their features are considered     

Wideband optical image rejection receiver and its crosstalk penalty

Demonstrates an optical-frequency image rejection receiver with more than 18 dB suppression over the 1.5-3.0 GHz IF region. The measured crosstalk penalties were less than 1.4 dB in a 2-channel 560 Mbit/s DPSK heterodyne optical communication system.<>     

560 Mbit/s optical PSK heterodyne detection using carrier recovery

An optical PSK heterodyne synchronous detection experiment was performed at a bit rate of 560 Mbit/s using carrier recovery in the IF stage. A receiver sensitivity of -51.6 dBm was achieved, and the power penalty due to the phase noise of the laser diodes was suppressed to less than that of DPSK.<>     

Tuning characteristics of optical amplification in 1.5 ?m InGaAsP/InP lasers

The bias current dependence of tuning wavelength in an optical amplifier is investigated in detail. Tuning wavelength decreases below threshold at the rate of ?0.36 ?/mA, mainly due to the change of carrier density, and increases at the rate of 0.11 A/mA above threshold due to the thermal effect.