Fourth-order dispersion compensation for 250-fs pulse transmissionover 139-km optical fiber

Record distance transmission of 250-fs pulses over 139-km optical fiber at 6-GHz repetition is realized by compensating chromatic dispersion up to fourth-order using a novel approach. The link is designed combining 108.5-km standard single-mode fiber (SMF), 17.5-km dispersion-shifted fiber, and 13-km negative-slope dispersion-compensating fiber to achieve both zero total chromatic dispersion and slope at the 1.55-μm carrier. Fourth-order pulse dispersion caused by the fiber dispersion curvature around 1.55 μm is then suppressed by adding the quadratic phase of opposite sign from excess SMF to produce 503-fs output. However, both higher quality and shorter 390-fs output is achieved after applying 6-GHz electrooptic phase modulation (3.5 π O-peak) to prestretched pulses and adding a further 50-m SMF to the link     

Characteristics of driver and receiver circuits with a passivetransmission line in RSFQ circuits

We report simulated results of-rapid single flux quantum (SFQ) circuits having driver, receiver, and passive transmission lines for propagating SFQ pulses to investigate the design criteria. We have studied the equivalent input/output resistance of the driver/receiver in various bias conditions and found that the resistance is almost proportional to the bias current of the driver/receiver. Furthermore, we have proposed inserting a series resistor at the end of the superconducting passive transmission line (PTL) for avoiding undesirable flux trapping in the loop and for isolation in regard to the DC current. We also found that the reduction of the bias margin due to the resistance is rather small when the resistance is much smaller than the impedance of the PTL. An operating margin of more than 30% was obtained in the driver/receiver circuits including the PTL and the series resistor     

Control scheme for optimizing the interferometer phase bias in a symmetric-Mach-Zehnder-type all-optical switch

A control scheme for accurately optimizing (and also automatically stabilizing) the interferometer phase bias of symmetric-Mach-Zehnder (SMZ)-type ultrafast all-optical switches is proposed. In this control scheme, weak continuous-wave light is used as supervisory input light and its spectral power ratio at the switch output is used as a bipolar error signal. Our experimental results for 168-Gb/s 16:1 demultiplexing with a hybrid-integrated SMZ switch indicate the feasibility and the sensitivity of this control scheme.     

A 950-MHz rectifier circuit for sensor network tags with 10-m distance

This paper presents a 950-MHz wireless power transmission system and a high-sensitivity rectifier circuit for ubiquitous sensor network tags. The wireless power transmission offers a battery-life-free sensor tag by recharging the output power of a base station into a secondary battery implemented with the tag. For realizing the system, a high-sensitivity rectifier with dynamic gate-drain biasing has been developed in a 0.3-/spl mu/m CMOS process. The measurement results show that the proposed rectifier can recharge a 1.2-V secondary battery over -14-dBm input RF power at a power conversion efficiency of 1.2%. In the proposed wireless system, this sensitivity corresponds to 10-m distance communication at 4-W output power from a base station.     

Nanoimprinting using release-agent-coated resins

A fluorinated self-assembled monolayer (F-SAM) is mainly used as the antisticking layer. To prevent the F-SAM coated on the nanoimprint lithography (NIL) mold from deteriorating, we propose a new form of nanoimprinting using a release-agent-coated resin. The results from measuring the surface free energy and observations by scanning probe microscopy (SPM) confirmed that the surface free energy, frictional force, and adhesion force of the release-agent spray-coated polymethylmethacrylate (PMMA) were lower than those of PMMA. To prove the release-agent spray-coated PMMA had a releasing effect, we tried to undertake thermal nanoimprinting on it using a mold without F-SAM. The pattern was clearly imprinted on the resin without any signs of adhesion.     

Magnetization distribution of magnetic vortex of amorphous FeSiB investigated by electron holography and computer simulation

The three-dimensional spin structure of the magnetic vortex of FeSiB, an amorphous soft magnetic material, was investigated by holography observation and computer simulation. Magnetization distribution in the neighborhood of the vortex center was estimated from the phase distribution obtained by holography observation. To confirm this magnetization distribution, sample-tilting experiments were performed: when the sample was tilted with respect to the electron beam direction, the phase-image center was found to shift along the tilting axis. Finite-element computer simulation was carried out to estimate the amount of shifts of the phase-image center in the sample tilting from the experimental magnetization distributions in the no sample-tilting conditions. We found that the simulated shifts of the phase-image center were in good agreement with those in the sample-tilting experiment, thus confirming the magnetization distribution near the vortex center obtained by holography observation.     

Development of a Cyclogyro-Based Flying Robot With Variable Attack Angle Mechanisms

This paper presents an experimental study on the development of a cyclogyro-based flying robot with a new variable angle of attack mechanism. A cyclogyro is a flying machine supported in the air by power-driven rotors that rotate about a horizontal axis, like the paddle-wheels of a steamboat. Machines of this type have been designed by some companies but there has been no record of any successful flights. Our design starts with a new variable angle of attack mechanism with an eccentric (rotational) point in addition to a rotational point connecting to a motor. The main feature of the mechanism with the eccentric rotational point is the ability to change attack of angles in accordance with the wing positions (as determined by the rotational angles of the cyclogyro) without actuators. The design parameters (wing span, the number of wings, and eccentric distance) of the flying robot are determined through a series of experiments. Experimental results show that the cyclogyro-based flying robot with the new variable angle of attack mechanism is capable of generating sufficient lift force for flying.     

Effects of high pressure treatments on intramuscular connective tissue

The changes in the morphological structure and proteoglycan (PGs) extractability of the intramuscular connective tissues from bovine skeletal muscle exposed to high pressure (100～400 MPa) were investigated and compared to those in muscle during ageing. SDS-PAGE profiles of the PGs were also studied. During ageing, structural changes in the endomysium and perimysium occured, and disruption of the honeycomb-like structure of endomysium was observed. In the pressurized muscle, deformation of the honeycomb-like structure of endomysium was accelerated with increase of pressure applied to the muscle, and disruption of endomysium was observed in several places in the muscle pressurized at 400 MPa. Changes in the extractability of PGs were not observed in the pressurized muscle, whereas the extractability of PGs decreased with ageing. Changes in the density of the main component in the PGs with molecular mass of more than 3000 kDa on the SDS-PAGE were not observed in the PGs from the pressurized muscle, whereas the density of this band gradually decreased during the ageing. The decrease in the amounts of PGs extracted from the aged muscle seems to be due to degradation of the PGs into small dialysable molecules. From the results, it seems that high pressure treatment has some different effects on intramuscular connective tissue to ageing. ?     

Ytterbium-decreasing Streptomyces sp. and its naphthoquinone-pigment production in the presence of rare-earth elements

We screened for oligotrophic microorganisms capable of decreasing the concentration of ytterbium (Yb), a representative of the heavy rare-earth elements, in a culture medium. From 476 strains of oligotrophic microorganisms (grown on 1/100 diluted nutrient agar) isolated from soil and river water samples, 5 strains capable of reducing the concentration of Yb in diluted nutrient broth containing 5 ppm Yb were selected. Among them, a strain capable of reducing the concentration of all rare-earth elements to a great extent was identified as Streptomyces sp. (strain YB-1). This strain produced redish-purple pigment(s) only in the presence of rare earths, but not in that of other metals. The pigment was extracted with ethyl acetate and purified by a series of column chromatography steps. From the results of structural analysis using ultraviolet or infrared absorption spectrometry and 13C-NMR, the pigment was determined to be a kind of naphthoquinone similar to nanaomycin produced by a Streptomyces sp. These results suggested that rare earths might affect the physiological activity of this strain.     

Growth energetics of Lactococcus lactis subsp. lactis biovar diacetylactis in cometabolism of citrate and glucose

Certain strains of lactic acid bacteria present in commercial cheese starters, characterized by faint transparent colonies on an agar plate containing 1 mg kg ⁻¹ crystal violet (CVT), were identified as Lactococcus lactis subsp. (ssp) lactis biovar diacetylactis. The effect of citrate on the growth of these strains (CVT strains) in the presence of glucose was studied, in comparison with L. lactis strains. Molar growth yield from glucose (Y_G, g dry weight/mole of glucose consumed) for CVT strains grown on glucose plus citrate was significantly higher than the control (i.e. without citrate), but not for other L. lactis strains tested. Enhanced Y_G was also observed at a pH-controlled experiment, indicating that enhanced Y_G did not result from a buffering effect of citrate. CVT strains, in contrast to other strains of the same species, were shown to obtain enough energy to enhance Y_G on glucose–citrate mixtures.