Low-threshold distributed reflector laser consisting of wide and narrow wirelike active regions

We demonstrate a low-threshold distributed reflector laser, consisting of a distributed feedback section with wirelike active regions and a passive distributed Bragg reflector section with narrower ones, by utilizing the lateral quantum confinement effect. A threshold current under the room-temperature continuous-wave condition as low as 3.2 mA, which corresponds to a threshold current density of 290 A/cm/sup 2/, was obtained with the stripe width of 4.3 /spl mu/m and the active region length of 260 /spl mu/m. The differential quantum efficiency of 19% from the front facet, a high output ratio of 11 from the front facet to the rear facet, and a submode suppression ratio of 47 dB at a bias current 3.75 times the threshold were also achieved.     

Reaction Kinetics of Coke and some Carbonaceous Materials with CO2 and Coke Strength after Reaction

The reaction rate per unit mass of wood char was an order of magnitude larger than that of coke and graphite and that of glassy carbon was an order of magnitude smaller than the latter. However, the reaction rate per unit surface area of wood char was smaller than that of graphite. The reaction of coke proceeded homogeneously at temperatures lower than 1373 K, while the reaction was restricted to the surface layer at higher temperatures. The tensile strength of coke after reaction decreased with the reaction degree at 1273 K, but was not changed or even increased at 1573 K. This is due to the fact that at 1573 K the core of the sample was not attacked by CO₂ but strengthened by further crystallization.     

Development of Resistive Oxygen Sensors Based on Cerium Oxide Thick Film

It is important to shorten the response time of resistive oxygen sensor in order to reduce harmful emission of automobiles. The diffusion and surface reaction theory tells us that reducing particle size leads to shortening the response time. The fine ceria powder was prepared a by new precipitation method and the oxygen sensors having ceria thick film with the particle size of 120 nm were fabricated using fine ceria (cerium oxide) powder. The thick film exhibited good adhesion to alumina substrate. The value of n in R P(O₂)^1/n at 1073 and 1173 K were 6.2 and 6.4 in the oxygen partial pressures range from 10^{– 13} to 10⁵ Pa, respectively. The response time for the sensor was 22 and 12 ms at 1073 and 1173 K, respectively. The sensor fabricated in this study showed fast response.     

Effects of R(-)-1-(benzo[b]thiophen-5-yl)-2-[2-N,N-diethylamino)ethoxy]ethan ol hydrochloride (T-588), a novel cognitive enhancer, on noradrenaline release in rat cerebral cortical slices

We investigated the effects of R(-)-1-(benzo[b]thiophen-5-yl)-2-[2-(N,N-diethylamino)ethoxy]ethan ol hydrochloride (T-588), a novel cognitive enhancer, on noradrenaline (NA) release from rat cerebral cortical slices in vitro. Addition of T-588 in an assay mixture stimulated [3H]NA release from prelabeled slices in the presence or absence of extracellular CaCl2, and in the presence of the Ca2+/calmodulin antagonists N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and trifluoperazine. T-588 stimulated NA release with a time lag of about 1 min, and the high level of release was maintained for at least 10 min, whereas maximal KCl-evoked NA release was observed within 1 min after the addition of KCl, and the effect declined subsequently. The effect of T-588 was reversible (pretreatment with T-588 showed no effect on NA release after two washes by centrifugation). We also compared the effects of T-588 and N-ethylmaleimide (NEM), a sulfhydryl alkylating agent known to stimulate neurotransmitter release in several types of cells. The addition of NEM stimulated NA release irreversibly from the slices in a Ca2+-independent manner, and the effect of NEM, but not that of T-588, was inhibited by the simultaneous addition of dithiothreitol, a sulfhydryl group reducing agent. The addition of T-588, which stimulated NA release by itself, inhibited the NA release by 0.6 mM NEM, although the effect of T-588 was additive in the presence of 0.2 mM NEM. These findings suggest that T-588 stimulates NA release from rat cerebral cortical slices in a Ca2+- and calmodulin-independent manner, possibly via an NEM-sensitive factor(s), although the mechanism of the effects of T-588 seems to be different from that of NEM.     

Human reliability and safety evaluation of man-machine systems

The security of a plant is strongly affected by human factors. Though human reliability in a man-machine system has been studied using a probabilistic approach the same as machine components, human behavior is quite different from that of a machine. We make clear some characteristics of human reliability by experiment, and suggest a mathematical model which represents the reliability of man-machine systems by using fuzzy set theory.