Examination of the dual‐band microwave wireless access system using radio on fiber technique

The Radio on Fiber (ROF) technique has great potential in wireless communication systems. In this paper, we report on a fundamental examination of microwave wireless access systems based on Radio on Fiber. First, we designed and constructed examination systems by applying dual band (2.4 and 5 GHz) multiservice transmission systems and confirmed that there was sufficient performance through a transmission experiment. Then, application of FP‐LD (Fabry Perot Laser Diode) was considered in order to reduce the system cost, and for the most part degradation of the transmission characteristics was not observed when FP‐LD was used. Finally, a BIDI (bidirectional) module which integrated LD and PD within one package was made to further reduce costs. By measuring the transmission performance, applying the BIDI module to ROF systems was shown to be effective. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 32–40, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20471     

Gene subset selection in kernel-induced feature space

This paper proposes a new filter approach to gene subset selection for kernel-based classifiers. We derive kernel forms of several well-known class separability criteria, and gene subset selection based on the kernelized criteria is applied to microarray cancer classification problems. The performance of our proposed strategy is compared in experiments with those of the conventional filter approach as well as gene ranking methods.     

Stability of Skutterudite Thermoelectric Materials

By multifilling with La, Ba, Ga, Ti, Yb, Ca, Al, and In, the dimensionless figure of merit ZT of filled skutterudites has been improved in this work. ZT reached 0.75 for p-type (La,Ba,Ga,Ti) _x (Fe,Co)₄Sb₁₂ (x = 0.8 to 1.0) and 1.0 for n-type (Yb,Ca,Al,Ga,In) _y (Co,Fe)₄Sb₁₂ (y = 0.7 to 0.9). After annealing at 873 K for 180 h, 300 h, 710 h, 1000 h, and 5000 h in vacuum, the Seebeck coefficient S and the electrical resistivity ρ of the samples increased while the thermal conductivity λ decreased with increasing annealing time. As a result, the ZT values of both p- and n-type skutterudites remained unchanged or were slightly improved, demonstrating the excellent thermal stability of these skutterudites.     

Evaluation of the possibility that free fatty acids cause false-positive result in diarrhetic shellfish poisoning mouse bioassay in actual use

Midgut glands of bivalves are used for the mouse bioassay of diarrhetic shellfish poison (DSP). A large quantity of free fatty acids (FFAs) causes a false positive outcome in the assay. To examine whether this is likely to occus under conditions of actual use, we analyzed the contents of the FFAs in the enlarged midgut glands during gametogenesis of Japanese scallops Patinopecten yessoensis that had been caught at two points in Hunka Bay on March 27, 2006, because the content of FFAs may increase with activation of lipogenesis for gametogenesis. Fatty acids (FAs) were measured with fluorometric high-performance liquid chromatography after derivatization with 9-anthryldiazomethane. The total FFAs (14 : 0, 16 : 0, 18 : 0, 16 : 1, 18 : 1, 18 : 4, 20 : 5 and 22 : 6) represented 3.3-4.2 wt% of the lipid. The toxic FFAs accounted for 40-43 wt% of the total FFAs. Content of each FFA (18 : 1, 2.7-5.0 mg/g lipid; 18 : 4, tr.-2.0 mg/g; 20 : 4, n.d.; 20 : 5, 8.0-9.1 mg/g and 22 : 6, 2.0-2.1 mg/g) was lower than the lethal dose tentatively calculated from the relative toxicity. It appears that the likelihood of FFAs causing false-positives in the mouse bioassay is low if the sample is fresh and is extracted immediately after homogenizing.     

Real-time monitoring of luciferase-tagged Cronobacter sakazakii in reconstituted infant milk formula

The aim of this study was to examine the potential of using a lux-tagged Cronobacter sakazakii strain to monitor growth of the bacterium in various liquids. C. sakazakii was transformed with plasmid p16S lux, and integration of the plasmid at the desired site on the chromosome was confirmed by PCR. The growth of the lux-tagged strain was similar to that of the non-lux-tagged strain, and the integrated plasmid was stable when cells were cultured in the absence of antibiotic. Growth of the lux-tagged strain was monitored in real time in Luria-Bertani broth, skim milk, and infant milk formula by using both the Luminoskan luminometer and the Xenogen IVIS imager. Bioluminescence could be detected when the lux-tagged strain was cocultured with other bacteria. The effect of monocaprylin and nisin on the growth of C. sakazakii in milk was monitored by measuring bioluminescence. In conclusion, growth of a lux-tagged C. sakazakii can be monitored in real time in both clear and opaque liquids by measuring bioluminescence. lux-tagged C. sakazakii strains could be potentially used in high-throughput assays to monitor the effects of various infant milk formula compositions on growth of the bacterium.     

Nano-strip grating lines self-organized by a high speed scanning CW laser

After a laser annealing experiment on Si wafer, we found an asymmetric sheet resistance on the surface of the wafer. Periodic nano-strip grating lines (nano-SGLs) were self-organized along the trace of one-time scanning of the continuous wave (CW) laser. Depending on laser power, the nano-trench formed with a period ranging from 500 to 800 nm with a flat trough between trench structures. This simple method of combining the scanning laser with high scanning speed of 300 m min(-1) promises a large area of nanostructure fabrication with a high output. As a demonstration of the versatile method, concentric circles were drawn on silicon substrate rotated by a personal computer (PC) cooling fan. Even with such a simple system, the nano-SGL showed iridescence from the concentric circles.     

PIV measurement and turbulence scale in turbulent combustion

We have investigated turbulent combustion by PIV (Particle Image Velocimetry) technique. Comparing with LDV data, the validity of PIV measurements has been confirmed. Particularly, the conditions of sampling number and spatial resolution have been shown to yield reliable data using PIV. Based on the velocity fields in cold flow and combustion, the interaction between flame and flow has been discussed. It was observed that the flow field is changed by combustion and the turbulence is reduced. In order to determine statistical quantities such as mean velocity and RMS of velocity fluctuation, a sampling number of 1000 is needed. Moreover, the velocity correlation coefficient was evaluated to obtain the integral length scale of the flow. For both cold flow and combustion, the PIV estimated scale is very close to that of LDV based on the assumption of Taylor's hypothesis. As a result, the spatial resolution in this study is about 6 times smaller than the integral length scale. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(7): 501–512, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20129