Frequency range extension of actively mode-locked lasers integratedwith electroabsorption modulators using chirped gratings

We have fabricated actively mode-locked lasers integrated with electroabsorption modulators and chirped gratings. A chirped grating with a large chirp rate of 1.45 Å/μm can be realized by using multiphase-shifted patterns. Short pulses of 4-6 ps were generated over a wide frequency range from 18.9-19.8 GHz. We observed jumps in the wavelength during detuning. These jumps arise from multiple lobes in the reflectivity spectrum. It is found that the wavelength jumps cause increases in the intensity noise. We showed that by reducing the grating length from 150 to 100 μm the sidelobes were suppressed and the detuning frequency range of over 1% could be realized. A smaller pulsewidth was obtained for the negatively-chirped gratings when compared to the positively chirped gratings     

Narrow-beam divergence 1.3-μm multiple-quantum-well laser diodeswith monolithically integrated tapered thickness waveguide

This paper describes the optimum design, fabrication, and performance of a 1.3-μm multiple-quantum-well (MQW) laser diode monolithically integrated with a tapered thickness spot-size transformer. The dependence of the lasing characteristics on the thickness distribution of the core layer and on the current injection profile of the device were analyzed. This integrated laser with its optimized structure performed at a low threshold current of 22.2 mA, even at 85°C. The integrated spot-size transformer effectively reduced the lateral and vertical far-field FWHM's to 8° and 9°, respectively. A very long lifetime of over 1×10⁵ h was estimated at 85°C and 8 mW under CW operation     

Effect of O2 on NO removal by ammonia radical injection using one-cycle sinusoidal power source

NO reduction experiment was performed by injecting ammonia radicals, which were externally generated by flowing the NH₃ gas diluted with Ar gas through a dielectric barrier discharge with a one-cycle sinusoidal-wave power source. The discharge was intermittently formed between coaxial cylindrical electrodes with a space of 1.5 mm at an applied peak-to-peak voltage of 3-25 kV. The generated radicals were injected into simulation gas (NO/O₂/N₂). The simulation gas contained 0-5.6% O₂, and the effect of O₂ on NO_x removal was discussed. The minimum reaction temperature for NO reduction was low when simulation gas contained O₂. High O₂ concentration (O₂=5.6%) in simulation gas, high repetition rate to NH₃, and high applied power to NH₃ decreased NO removal efficiency.     

The role of sputter etching and annealing processes on the formation of β-FeSi2 thin films

For formation of β-FeSi₂ using ion beam sputter deposition (IBSD) method, sputter etching (SE) followed by thermal annealing is effective substrate treatment to obtain highly (100)-oriented β-FeSi₂ on Si(100). However, the best condition of these treatments are not yet known. In this work, the effect of SE together with annealing process on the orientation of the film is investigated. Prior to the deposition of Fe, the substrate is irradiated by Ne⁺ ions with various energy and fluence followed by thermal annealing at 1073 K for 60 min. The overall results show the most suitable SE condition using Ne⁺ ion on IBSD method is the energy of 1 keV with the fluence of 3.0×10¹⁹ ions /m².     

Development of an alpha/beta/gamma detector for radiation monitoring

For radiation monitoring at the site of nuclear power plant accidents such as Fukushima Daiichi, radiation detectors not only for gamma photons but also for alpha and beta particles are needed because some nuclear fission products emit beta particles and gamma photons and some nuclear fuels contain plutonium that emits alpha particles. We developed a radiation detector that can simultaneously monitor alpha and beta particles and gamma photons for radiation monitoring. The detector consists of three-layered scintillators optically coupled to each other and coupled to a photomultiplier tube. The first layer, which is made of a thin plastic scintillator (decay time: 2.4 ns), detects alpha particles. The second layer, which is made of a thin Gd(2)SiO(5) (GSO) scintillator with 1.5 mol.% Ce (decay time: 35 ns), detects beta particles. The third layer made of a thin GSO scintillator with 0.4 mol.% Ce (decay time: 70 ns) detects gamma photons. By using pulse shape discrimination, the count rates of these layers can be separated. With individual irradiation of alpha and beta particles and gamma photons, the count rate of the first layer represented the alpha particles, the second layer represented the beta particles, and the third layer represented the gamma photons. Even with simultaneous irradiation of the alpha and beta particles and the gamma photons, these three types of radiation can be individually monitored using correction for the gamma detection efficiency of the second and third layers. Our developed alpha, beta, and gamma detector is simple and will be useful for radiation monitoring, especially at nuclear power plant accident sites or other applications where the simultaneous measurements of alpha and beta particles and gamma photons are required.     

Measurement of IGSCC depth by SAFT-UT

In order to examine the ability of SAFT-UT of measuring the IGSCC depth, two preparatory experiments on artificial defects and one on a real IGSCC were performed.In the first, the capabilities of SAFT-UT of determining crack depth were assessed for an artificial defect in a carbon steel. It was found that crack depth could be measured by obtaining the crack tip images.In the second, influences of large grain size were investigated by testing a slot made by EDM in the weld heat affected zone of austenitic stainless steel piping. It was found that a narrow beam spread probe, i.e., a large F number probe, was better for measurement of crack depth in an austenitic stainless steel.Finally, a real IGSCC was tested as introduced in two different test blocks. The positions of tip and the opening of the IGSCC deduced by SAFT-UT were in a fairly good agreement with those revealed afterwards.     

Differences in properties of myofibrillar proteins from bovine semitendinosus muscle after hydrostatic pressure or heat treatment

Hydrostatic pressure (HP) and heat treatments of myofibrillar proteins have both been shown to induce protein denaturation, but different gel formation properties result from these treatments. To characterise differences in the properties of proteins resulting from HP or heat treatment, Ca‐ and Mg‐ATPase activities (ATP, adenosine triphosphate) and protein solubility in 0.1 and 0.6 mol L^?1 KCl buffers (pH 7) were evaluated in this study. The inactivation rate of Ca‐ATPase of myofibrillar proteins (Mf) induced by HP was slower than that of Mg‐ATPase at each of the tested pressures. However, the inactivation rate of Ca‐ATPase induced by heating was faster than that of Mg‐ATPase at each of the tested temperatures. The level of soluble proteins in Mf suspension induced by HP in 0.1 mol L^?1 KCl buffer increased with increasing pressure up to 400 MPa and then decreased slightly at 500 MPa. However, the level of soluble proteins in Mf suspension induced by heat treatment in 0.1 mol L^?1 KCl buffer increased with increasing temperature up to 55°C. According to the results of sodium dodecyl sulfate polyacrylamide gel electrophoresis, the levels of soluble myosin heavy chain and actin in Mf suspension induced by HP in 0.6 mol L^?1 KCl buffer decreased simultaneously at pressures higher than 300 MPa. The level of soluble MHC in 0.6 mol L^?1 KCl buffer decreased gradually with increasing temperature, but there were no changes in the level of soluble actin in 0.6 mol L^?1 KCl buffer with increasing temperature up to 50°C. These results showed that the mechanism of HP‐induced protein denaturation was different from the mechanism underlying heat‐induced protein denaturation. Copyright © 2006 Society of Chemical Industry     

Release of short and proline-rich antihypertensive peptides from casein hydrolysate with an Aspergillus oryzae protease

Angiotensin-I converting enzyme inhibitory activities were measured after hydrolysis of casein by 9 different commercially available proteolytic enzymes. Among these enzymes, a protease isolated from Aspergillus oryzae showed the highest angiotensin-I converting enzyme inhibitory activity per peptide. The A. oryzae peptide also showed the highest antihypertensive effect in spontaneously hypertensive rats when the systolic blood pressure was measured 5 h after oral administration of 32 mg/kg of various enzymatic hydrolysates. Significant antihypertensive effects were observed with dosages of 9.6, 32, and 96 mg of the A. oryzae peptide/kg of body weight (BW), and the effects were dependent on these peptide dosages.Analysis of peptide length showed the A. oryzae hydrolysate was the shortest of all tested casein hydrolysates; the peptide mixture had an average value of 1.4 amino acids (AA) in the sequence. To further characterize the A. oryzae hydrolysate, we analyzed the AA sequence of the whole peptide mixture. Various AA were detected at the first AA position, however, an increased number of Pro residues were observed at the second and third position of the A. oryzae hydrolysate. No strong signals were detected after the fourth AA position of the A. oryzae hydrolysate. These results suggest that the casein hydrolysate of A. oryzae, which expressed potent antihypertensive effects in spontaneously hypertensive rats, mainly contain short peptides of X-Pro and X-Pro-Pro sequences.     

Detonation propagation in narrow gaps with various configurations

In general all detonation waves have cellular structure formed by the trajectory of the triple points.This paperaims to investigate experimentally the propagation of detonation in narrow gaps for hydrogen-oxygen-argonmixtures in terms of various gap heights and gap widths.The gap of total length 1500 mm was constructed bythree pair of stainless plates,each of them was 500 mm in length,which were inserted in a detonation tube.Thegap heights were varied from 1.2 mm to 3.0 mm while the gap widths were varied from 10 mm to 40 mm.Variousargon dilution rates were tested in the present experiments to change the size of cellular structure.Attempts havebeen made by means of reaction front velocity,shock front velocity,and smoked foil to record variations of cel-lular structure inside the gaps.A combination probe composed of a pressure and an ion probe detected the arrivalof the shock and the reaction front individually at one measurement point.Experimental results show that thenumber of the triple points contained in detonation front decreases with decrease in the gap heights and gapwidths,which lead to larger cellular structures.For mixtures with low detonability,cell size is affected by a cer-tain gap width although conversely cell size is almost independent of gap width.From the present result it wasfound that detonation propagation inside the gaps is strongly governed by the gap height and effects of gap widthis dependent on detonability of mixtures.     

Microfabrication of polytetrafluoroethylene using SR direct etching

Polytetrafluoroethylene (PTFE) is a very attractive material for various fields because of its chemical resistance, insulation properties, and hydrophobic properties. However, it is difficult to fabricate PTFE microstructures with conventional techniques such as semiconductor processes or micromachining. We have succeeded in the fabrication of high‐aspect‐ratio microfluidics parts from PTFE by direct in‐vacuum photo‐etching utilizing synchrotron radiation (SR) at energy levels from 2 to 12 keV. This paper presents an analysis of the mechanisms of the PTFE microfabrication process and describes newly discovered processing characteristics of PTFE. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(4): 49–54, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21152