Effects of zinc doping in DFB lasers emitting at 1.3 and 1.55 mu m

Reports on the performance of GaInAsP/InP DFB lasers with Zn-doped active region. At both 1.3 and 1.55 mu m the authors achieved a large bandwidth owing to the increased differential gain. The carrier lifetime of the lasers decreased with doping level. The decreased carrier lifetime had the effect of reducing the pattern effect, and they could obtain a clear eye opening with 4 Gbit/s NRZ modulation.<>     

DyP-Type Peroxidases: Recent Advances and Perspectives

In this review, we chart the major milestones in the research progress on the DyP-type peroxidase family over the past decade. Though mainly distributed among bacteria and fungi, this family actually exhibits more widespread diversity. Advanced tertiary structural analyses have revealed common and different features among members of this family. Notably, the catalytic cycle for the peroxidase activity of DyP-type peroxidases appears to be different from that of other ubiquitous heme peroxidases. DyP-type peroxidases have also been reported to possess activities in addition to peroxidase function, including hydrolase or oxidase activity. They also show various cellular distributions, functioning not only inside cells but also outside of cells. Some are also cargo proteins of encapsulin. Unique, noteworthy functions include a key role in life-cycle switching in Streptomyces and the operation of an iron transport system in Staphylococcus aureus, Bacillus subtilis and Escherichia coli. We also present several probable physiological roles of DyP-type peroxidases that reflect the widespread distribution and function of these enzymes. Lignin degradation is the most common function attributed to DyP-type peroxidases, but their activity is not high compared with that of standard lignin-degrading enzymes. From an environmental standpoint, degradation of natural antifungal anthraquinone compounds is a specific focus of DyP-type peroxidase research. Considered in its totality, the DyP-type peroxidase family offers a rich source of diverse and attractive materials for research scientists.     

Removal of a high load of ammonia gas by a marine bacterium, Vibrio alginolyticus

A newly isolated marine bacterium, Vibrio alginolyticus was used to remove a high load of ammonia gas. By a stepwise increase in ammonia supply over the concentration range of 120-2000 ppm (v/v), complete removal of ammonia was observed from the start of the experiment in a suspended culture of the bacterium in basal medium containing 3% NaCl. When cells were inoculated onto an inorganic packing material in a biofilter, and a high load of ammonia was introduced continuously under nonsterile conditions, the average percentage of gas removed exceeded 85% for a 61-d operation. The maximum removal capacity and the complete removal capacity were 22.8 g-N/kg-dry packing material/d and 18.6 g-N/kg-dry packing material/d, respectively, which were about four times larger than those obtained in nitrifying sludge inoculated onto the same packing material. During this operation, the nonsterile air supply had no adverse effect on the removability of ammonia by V. alginolyticus.     

THERMALLY INDUCED STRESS WAVES IN FUNCTIONALLY GRADED MATERIALS WITH TEMPERATURE-DEPENDENT MATERIAL PROPERTIES

This article is concerned with the dynamic treatment of thermally induced stress waves in an infinite elastic plate subjected to impulsive electromagnetic radiation. The plate is assumed to be a functionally graded material (FGM), meaning that the material is composed of multiconstituents in ceramics and metals, the volume fractions of which distribute continuously inside the material. The mathematical problem is one of wave propagation in a typical nonhomogeneous material The radiation absorption is assumed to occur at a constant rate for the duration of the pulse and to diminish exponentially with distance from the surface of the plate, assuming negligible heat conduction. In treating problems, the nature of the stress-wave buildup in the plate is studied for the case of a temperature-dependent solid, that is, when material properties vary with temperature. The numerical procedure employs the characteristic method based on the integration of the governing equations along the characteristics. Numerical calculations are carried out for ceramic-metal FGM plates showing the influences of the temperature-dependent material properties and the volume fractions of the phases composing the FGM on the magnitude of the dynamic thermal stresses.     

Effects of coal rank and reaction conditions upon coprocessing coal with waste tyre

It is well known that the amount of waste tyre increases every year, and a numerous amount of waste tyre is landfilled or dumped all over the world, which causes environmental problems, such as destruction of natural places and the risk of fires. Coprocessing waste tyre and coal is considered as one of the effective processing methods of both materials. Upon coprocessing lower rank coal (Wyoming, C; 68%) with waste tyre, the synergistic effects to upgrading, such as the increase of oil yield and the decrease of residue yield, were appeared. However, the synergistic effects were not observed on coprocessing two kinds of higher rank coals with waste tyre. The reactions of coal with benzophenone were carried out to discuss the hydrogen donatability of coal. Conversion of benzophenone to diphenylmethane on the reaction with Wyoming coal was higher than those of higher rank coals. Accordingly, it was considered that the synergistic effects to upgrading upon coprocessing Wyoming coal with waste tyre were obtained owing to the enhancement of stabilization of radicals from tyre and Wyoming coal through the hydrogen donation from both tyre and Wyoming coal. The effects of reaction temperature and the amount of solvent upon coprocessing Wyoming coal with waste tyre were also discussed in this study.     

6-in diameter InP single crystals grown by the hot-wall LEC method and the mirror wafers

6-in diameter Fe-doped semi-insulating InP single crystals have been grown by the hot-wall liquid encapsulated Czochralski method. This method has a quartz inner vessel to stabilize the thermal convection. Temperature gradient and solid-liquid interface shape can be controlled by a multizone heater system. The weight of grown crystal was 18 kg and the full length was 250 mm. The dislocation density was about 1/spl times/10/sup 5/ cm/sup -2/. The resistivity was more than 1/spl times/10/sup 7/ /spl Omega/cm and its uniformity was the same as the smaller diameter crystal. The conditions of wafer processing were optimized to improve the wafer flatness. The rolloff and the slope of the wafer surface could be reduced especially by the improvement of the polishing conditions. The typical total thickness variation was 3.3 /spl mu/m, and it was comparable to the GaAs wafer.