The control of polarization of laser diodes

The mode-competition phenomena are studied through three experiments. At first, in double-heterostructure laser diodes with thick active layers, TE and TM modes tend to coexist and the mode competition between these two modes is observed from the correlation of the light outputs of these two modes where the increase of light output of one mode tends to decrease the light output of other mode. In a laser diode operating with an external reflector, the increase of light output for the TE mode leads to the decrease of light output for the TM mode. In case the external reflector is set to deviate from the parallel plane to the cleaved surface of the laser diode, the TM-mode component tends to its magnitude, even if the inherent mode of this diode is TE. In the experiment of external light-beam irradiation onto a laser diode, the light intensity of one mode is decreased by an incidence of light beam having another mode from the other laser diode. In this experiment, the significance of a gap distance between the two laser diodes is confirmed clearly, where the two laser diodes interact with each other through the light beam.     

Role of alloying elements in phase decomposition in alnico magnet alloys

Partition of alloying elements between the Fe-rich disordered a, and NiAl-rich ordered α₂ phases in Fe-Ni-Al base systems has been studied by the diffusion couple technique. It has been revealed that Ti, Cu, Mn, and Co are distributed to the α₂ phase rather than the α₁ phase, while Si, V, Nb, Cr, and Mo are mostly distributed to the α₁ phase. Ti remarkably narrows the miscibility gap between the α₁ and α₂ phases and shifts the summit point to the Fe-rich side. Cu promotes the diffusion rate of atoms in the α₂ phase. On the basis of these experimental results, the role of alloying elements in the spinodal decomposition of Alnico magnets has been discussed.     

High-frequency high-power static induction transistor

This article demonstrates the characteristics, physical construction, and application for a newly commercialized high-frequency static induction transistor (SIT). The main features of this device are a lowering in the gate-to-source and gate-to-drain capacitances and an increase in the breakdown voltage and power rating. These enhancements were brought about as a result of the introduction of new and refined manufacturing technologies. The new high-frequency SIT device is being applied in applications such as medium wavelength radio transmitters and induction heaters     

Automated smear counting and data processing using a notebook computer in a biomedical research facility

An automated smear counting and data processing system for a life science laboratory was developed to facilitate routine surveys and eliminate human errors by using a notebook computer. This system was composed of a personal computer, a liquid scintillation counter and a well-type NaI(Tl) scintillation counter. The radioactivity of smear samples was automatically measured by these counters. The personal computer received raw signals from the counters through an interface of RS-232C. The software for the computer evaluated the surface density of each radioisotope and printed out that value along with other items as a report. The software was programmed in Pascal language. This system was successfully applied to routine surveys for contamination in our facility.     

Miscibility gap due to ordering in the BCC Fe-Ge system

Metallurgical and Materials Transactions A - Phase equilibria in the bcc Fe-Ge system have been investigated by means of electron probe microanalysis and transmission electron microscopy. Two kinds...     

Effect of glycine on 5-aminolevulinic acid biosynthesis in heterotrophic culture of Chlorella regularis YA-603

Chlorella regularis strain YA-603 was previously found to exhibit a comparatively high growth rate and improved 5-aminolevulinic acid (ALA) productivity when cultured heterotrophically. Although the universal tetrapyrrole precursor ALA is synthesized from glutamate in algae and higher plants, in this study the addition of glutamate to the medium did not enhance ALA production in the heterotrophic culture of C. regularis YA-603. On the other hand, the addition of glycine, which is a precursor of ALA biosynthesis via the Shemin pathway in animal cells and some bacteria, enhanced both the specific growth rate and ALA production. Moreover, when a second glycine addition was made during the culture, the ALA concentration increased by about 1.5 times compared to that obtained with one glycine addition. From these results, it is suggested that the Shemin pathway contributes to ALA production, and that addition of glycine in the heterotrophic culture of C. regularis YA-603 can significantly increase the amount of ALA produced.     

Fatigue crack separation and merging simulation using the smoothed particle hydrodynamics

International Journal of Fracture - The present paper proposes a new computational method for the fatigue crack propagation in a metallic structure using the smoothed particle hydrodynamics (SPH)....     

Origin and control of high-temperature ferromagnetism in semiconductors

The extensive experimental and computational search for multifunctional materials has resulted in the development of semiconductor and oxide systems, such as (Ga,Mn)N, (Zn,Cr)Te and HfO(2), which exhibit surprisingly stable ferromagnetic signatures despite having a small or nominally zero concentration of magnetic elements. Here, we show that the ferromagnetism of (Zn,Cr)Te, and the associated magnetooptical and magnetotransport functionalities, are dominated by the formation of Cr-rich (Zn,Cr)Te metallic nanocrystals embedded in the Cr-poor (Zn,Cr)Te matrix. Importantly, the formation of these nanocrystals can be controlled by manipulating the charge state of the Cr ions during the epitaxy. The findings provide insight into the origin of ferromagnetism in a broad range of semiconductors and oxides, and indicate possible functionalities of these composite systems. Furthermore, they demonstrate a bottom-up method for self-organized nanostructure fabrication that is applicable to any system in which the charge state of a constituent depends on the Fermi-level position in the host semiconductor.