Dynamic spectral width of rapidly modulated 1.58 ?m GaInAsP/InP buried-heterostructure distributed-Bragg-reflector integrated-twin-guide lasers

The dynamic spectral width of a CW GaInAsP/InP buried-heterostructure distributed-Bragg-reflector integrated-twin-guide (BH-DBR-ITG) laser operating at a wavelength of 1.58 ?m was measured under direct modulation up to 3 GHz. The maximum dynamic spectral width at a modulation depth of 100% was measured to be 0.27 nm at the resonance-like frequency of 1.8 GHz. A possibility of wideband transmission of 1.55 ?m conventional single-mode fibre at 185 Gbit km is suggested.     

Axial-mode selectivities for various types of integrated twin-guide lasers

Wavelength dependencies of the gains, namely the axial-mode selectivities, of various types of integrated twin-guide (ITG) injection lasers are given theoretically. The double-resonator type, the distributed Bragg reflector (DBR), and the two tandem-connection types of ITG lasers are considered. The axial-mode selectivities are also discussed briefly in relation to the efficiencies.     

X-ray channeling technique using anomalous transmission and its application to si micro-defects induced by heat treatment

X-ray channeling (XRC) technique using anomalous transmission is newly developed as a method of evaluating micro-defects in bulk single crystals. It is ascertained that there is a definite correlation between the decrease of the (hkl) anomalously transmitted intensity and the characteristic of the lattice defect. The present XRC technique has been tentatively applied to micro-defects (M.D.’s) induced in Si during heat treatment. As a result, it is conjectured that dislocation loops and stacking faults are preferentially induced during N₂ atmosphere annealing at 1040‡C and wet O₂ atmosphere annealing at 1100‡C, respectively, though precipitates are also generated during both annealings.     

Room-temperature CW operation of 1.60 ?m GaInAsP/InP buried-heterostructure integrated laser with butt-jointed built-in distributed-Bragg-reflection waveguide

CW operation of a 1.60 ?m GaInAsP/InP buried-heterostructure integrated laser with butt-jointed built-in distributed-Bragg-reflection waveguide (BH BJB DBR integrated laser) was achieved at room temperature. Single longitudinal-mode operation at fixed mode was obtained in a temperature range of about 60 deg C, under the CW condition, and it was also maintained under rapid direct modulation of 1.6 GHz.     

II-VI semiconductors on InP for green-yellow emitters

Novel II-VI compound materials such as MgZnCdSe, BeZnCdSe, BeZnTe, and related superlattices grown on InP substrates have been investigated for yellow-green emitters employing molecular beam epitaxy. MgZnCdSe was grown in the Mg composition range of 0/spl sim/0.6 to clarify the compositional dependency of the bandgap and refractive index. MgSe-ZnCdSe and MgSe-ZnSeTe short-period superlattices were investigated; the superlattices behaved as quasi-quaternaries (QQs), so that their bandgap energies were controlled by the layer thickness combination of superlattices. For realizing strong lattice hardness, Be-contained H-VI compounds, such as BeZnCdSe and BeZnTe bulk crystals, and MgSe-BeZnCdSe, ZnCdSe-BeZnTe, and MgSe-BeZnTe short-period superlattices were investigated. The superlattices also behaved with QQ properties, by use of which multilayered heterostructures could be grown without growth interruption. Applying the superlattices, visible LEDs were fabricated emitting at the wavelengths from 554 (yellow-green) to 644 nm (red) at room temperature. For yellow (575 nm) LEDs, a long lifetime more than 3500 h was demonstrated even for defect densities as high as 10/sup 5/ cm/sup -2/. The BeZnTe buffers were effective in suppressing the defect density to less than 7 /spl times/ 10/sup 3/ cm/sup -3/. Finally, MgZnCdSe-based II-VI LDs were successfully operated with yellow-green lasing emissions around 560 nm at 77 K.     

Interactive Computer Animation of Hand Gestures using Status Estimation with Multiple Regression Analysis

This paper presents a method of interactively generating natural hand gesture animation using reduced dimensionality from multiple captured data sequences of finger motions conducting specific tasks. This method is achieved by introducing an estimation with multiple regression analysis. Even when the skeletal structure of the user who inputs the motion is different from that of the shape model in the computer, the motion that a user imagines is generated. Experimental results obtained from the interface applied to virtual object manipulation showed that the proposed method generates animation naturally, just as users would expect. This method enables us to make input devices that require minimal user training and computer calibration, and helps to make the user interface intuitive and easy to use.     

Semi-rational Engineering of a Promiscuous Fatty Acid Hydratase for Alteration of Regioselectivity

Fatty acid hydratases (FAHs) catalyze regio- and stereo-selective hydration of unsaturated fatty acids to produce hydroxy fatty acids. Fatty acid hydratase-1 (FA-HY1) from Lactobacillus Acidophilus is the most promiscuous and regiodiverse FAH identified so far. Here, we engineered binding site residues of FA-HY1 (S393, S395, S218 and P380) by semi-rational protein engineering to alter regioselectivity. Although it was not possible to obtain a completely new type of regioselectivity with our mutant libraries, a significant shift of regioselectivity was observed towards cis-5, cis-8, cis-11, cis-14, cis-17-eicosapentaenoic acid (EPA). We identified mutants (S393/S395 mutants) with excellent regioselectivity, generating a single hydroxy fatty acid product from EPA (15-OH product), which is advantageous from application perspective. This result is impressive given that wild-type FA-HY1 produces a mixture of 12-OH and 15-OH products at 63 : 37 ratio (12-OH : 15-OH). Moreover, our results indicate that native FA-HY1 is at its limit in terms of promiscuity and regiospecificity, thus it may not be possible to diversify its product portfolio with active site engineering. This behavior of FA-HY1 is unlike its orthologue, fatty acid hydratase-2 (FA-HY2; 58 % sequence identity to FA-HY1), which has been shown earlier to exhibit significant promiscuity and regioselectivity changes by a few active site mutations. Our reverse engineering from FA-HY1 to FA-HY2 further demonstrates this conclusion.     

Floral Scent of Osmanthus fragrans Discourages Foraging Behavior of Cabbage Butterfly, Pieris rapae

Field observations revealed that flowers of Osmanthus fragrans attract few insect species despite their strong scent and vivid coloration (yellowish orange). Floral volatiles of the plant were thus examined for suspected repellency to Pieris rapae, a potential visitor that never visits this flower. The influence of odor components on the foraging behavior of adult butterflies was assessed by two behavioral bioassays: proboscis extension reflex (PER) in response to olfactory stimuli and the frequency of visits to artificial flowers. In the PER bioassays, a binary mixture composed of a test material and 2-phenylethanol (a positive standard compound) was used, and the negative effect of test materials was appraised based on the degree of suppression caused compared with the original PER performance evoked by 2-phenylethanol alone. Isopentane extract of the flower exhibited significant deterrency in the PER test and remarkable repellency in the flower-visiting experiment, thereby suggesting the presence of a repellent(s) in the floral volatiles. Fractionation of the extract by silica gel column chromatography yielded an active fraction (based on PER performance), which, upon GC and GC-MS analyses, was found to consist of -decalactone, -ionone, and linalool oxide (LO) isomers (furanosides and pyranosides) as major components together with small amounts of linalool and -ionone. -Decalactone was strongly deterrent in the PER test, and -ionone and all LO isomers were weakly deterrent, while the other compounds exhibited no deterrency. In the flower-visiting tests, -decalactone showed notable repellency, whereas -ionone had no repellent effect. Among the LO isomers, at least furanosides (cis/trans mixture) and cis-pyranoside were found to be weakly repellent. On the other hand, the butterfly showed strong to weak EAG responses to LO furanosides, cis-LO pyranoside, -decalactone, and -ionone in decreasing order of intensity. The present results clearly indicate that the repellency of a compound is correlated with its deterrent effect on PER but not necessarily with antennal sensitivity.     

Resonant cavity-enhanced (RCE) photodetectors

The photosensitivity characteristics of resonant cavity-enhanced (RCE) photodetectors are investigated. The photodetectors were formed by integrating the active absorption region into a resonant cavity composed of top and bottom (buried) mirrors. A general expression for quantum efficiency for RCE photodetectors was derived taking the external losses into account. Drastic enhancement in quantum efficiency is demonstrated at resonant wavelengths for a high quality factor Q cavity with a very thin absorption layer. An improvement by a factor of four in the bandwidth-efficiency product for RCE p-i-n detectors is predicted. Molecular beam epitaxy grown RCE-heterojunction phototransistors (RCE-HPT) were fabricated and measured demonstrating good agreement between experiment and theory     

Coloration mechanism of the acrylonitrile solution of N-phenylmaleimide and its stabilization method

N-Phenylmaleimide (PMI) was used as an acrylonitrile (AN) solution which is convenient to handle because PMI is an irritative solid and difficult to handle. However, the PMI solution tends to color during storage upon heating and its yellow color is apt to become brownish. Impurities contained in the colored PMI solution were isolated and their structures identified. Azobenzene (AZB) and N, N′-diphenylhydradine (DPH) are the compounds which cause the color change in the solution. The extent of the coloration of the PMI solution increases with increase in the contents of AZB and DPH. It is considered that AZB and DPH are produced by the oxidation of aniline (ANL) generated by the hydrolysis of PMI in the solution. The addition of the antioxidants under a low concentration of oxygen was examined to prevent coloration of the solution based on the proposed mechanism of the coloration. These conditions proved to be sufficiently effective for stabilization of the solution. Furthermore, it was also confirmed that the extent of coloration of the polymer prepared from the stabilized solution is effectively minimized. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64:2037–2045, 1997