Enhancement of melt elasticity for poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) by addition of weak gel

Rheological properties in a molten state are studied extensively for poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), PHB‐HV, with a small amount of crosslinked poly(epichlorohydrin), PECH, having low density of crosslink points. It is found that adding 2 wt % of xPECH greatly enhances the melt elasticity of PHB‐HV, one of the serious defects of microbial PHB, whereas it has no effect on the shear viscosity. As a result, viscoelastic nature, and thus processability, of PHB‐HV can be controlled by blending the crosslinked PECH. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Layer-by-layer self-assembled mutilayer films of gold nanoparticles for surface-assisted laser desorption/ionization mass spectrometry

Layer-by-layer (LBL) self-assembled multilayer films of gold nanoparticles (AuNPs) on a silicon wafer were demonstrated to be promising substrates for surface-assisted laser desorption/ionization (SALDI) mass spectrometry (MS) of peptides and environmental pollutants for the first time. LBL multilayer films, (AuNPs/PAHC)n, consisting of alternating layers of ammonium citrate capped AuNPs and poly(allylamine hydrochloride) (PAHC) were prepared on a silicon surface. Silicon plates with aggregated AuNPs were more suitable than those with dispersed AuNPs for the SALDI-MS of peptides. The number of particle layers had a significant effect on the laser desorption/ionization of angiotensin I; the peak intensity of the peptide (molecular ion amount) increased with an increase in the number of layers of AuNPs. As a result, the (AuNPs/PAHC)5 multilayer films increased the sensitivity of the angiotensin I to subfemtomoles and raised the useful analyte mass range, thus making it possible to detect small proteins (a 12 kDa cytochrome c). The signal enhancement when using (AuNPs/PAHC)5 may be due to (i) the high absorption of the UV laser light at 337 nm by the AuNP layers, (ii) the low thermal conductivity due to the AuNPs being covered with a thin monolayer of PAHC, and (iii) the increase in the surface roughness (approximately 100 nm) with the number of AuNP layers. Thus, laser-induced rapid high heating of AuNPs for effective desorption/ionization of peptides is possible. In addition, it was found that (AuNPs/PAHC)5 could be used to extract environmental pollutants (pyrene and dimethyldistearylammonium chloride) from very dilute aqueous solutions with concentrations less than 10(-10) mg/mL, and the analytes trapped in the LBL film could be identified by introducing the film directly into the SALDI mass spectrometer without needing to elute the analytes out of the film.     

Growth of InGaN self-assembled quantum dots and their applicationto lasers

We have successfully grown InGaN self assembled quantum dots (QD's) on a GaN layer, using atmospheric-pressure metalorganic chemical vapor deposition (MOCVD). The average diameter of the QD's was as small as 8.4 nm, and strong emission from the QD's was observed at room temperature. Next, we have investigated a structure in which InGaN QD's were stacked to increase the total QD density. InGaN QD's were formed even when the number of stacked layers was ten. As the number of layers increased, the photoluminescence (PL) intensity increased drastically. Moreover, we have fabricated a laser structure with InGaN QD's embedded into the active layer. A clear threshold of 6.0 mJ/cm² was observed in the dependence of the emission intensity on the excitation energy at room temperature under optical excitation. Above the threshold, the emission was strongly polarized in the transverse electric (TE) mode, and the linewidth of the emission spectra was reduced to below 0.1 nm (resolution limit). The peak wavelength was around 405 nm. These results indicate lasing action at room temperature     

Technology interaction of Electrical Engineering

The paper reviews the global activities of the Technical Committee for History of Electrical Engineering (HEE) in Institute of Electrical Engineers of Japan (IEEJ) to discuss its future activities. Introducing HEE global activities in the Maui Meeting (MM) and International Conference on Electrical Engineering (ICEE), the paper discusses the framework of the International Joint Study Programme for History of Technology Interaction (IJSP/HTI) on the basis of its current study conducted by the Investigation Committee for International Joint Study for History of Technology Interaction (IC/HTI). It concludes the discussion with the view that the study of history could serve as a foundation for us to achieve global contributions in the field of engineering as well. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Accumulation and elimination profiles of paralytic shellfish poison in the short-necked clam Tapes japonica fed with the toxic dinoflagellate Gymnodinium catenatum

The paralytic shellfish poison (PSP)-producing dinoflagellate Gymnodinium catenatum (Gc) was fed to the short-necked clam Tapes japonica, and the accumulation, transformation and elimination profiles of PSP were investigated by means of high-performance liquid chromatography with postcolumn fluorescence derivatization (HPLC-FLD). The short-necked clams ingested most of the Gc cells (4 x 10(6) cells) supplied as a bolus at the beginning of the experiment, and accumulated a maximal amount of toxin (181 nmol/10 clams) after 12 hr. The rate of toxin accumulation at that time was 16%, which rapidly decreased thereafter. During the rearing period, a variation in toxin composition, derived presumably from the transformation of toxin analogues in the clams, was observed, including a reversal of the ratio of C2 to C1, and the appearance of carbamate (gonyautoxin (GTX) 2, 3) and decarbamoyl (dc) derivatives (decarbamoylsaxitoxin (dcSTX) and dcGTX2, 3), which were undetectable in Gc cells. The total amount of toxin contained in clams and residue (remaining Gc cells and/or excrement in the rearing tank) gradually declined, and only about 1% of the supplied toxin was detected at the end of the experiment.     

Polarization dependence of optoelectronic properties in quantumdots and quantum wires-consequences of valence-band mixing

The electronic bandstructure in quantum dots and quantum wires is studied, including the valence-band mixing effects. Based on the bandstructure, results for the polarization dependence of absorption and gain (at room temperature) are examined. The related differential gain and the α-parameter is also studied. Our results show that it is extremely important to include valence-band mixing effects in predicting the laser performance of such structures     

Design of Logical Topology with Effective Waveband Usage in IP-over-WDM Networks

We deal with the problem of designing the logical topology in IP-over-WDM networks. Many conventional methods for designing the logical topology assume that a constant number of wavelengths will be available on each fiber. But it is not necessary to utilize all wavelengths on each fiber in building an effective logical topology on a WDM network. Instead, several wave-bands may be considered for introduction while deploying additional wave-bands and their corresponding optical amplifiers when additional wavelengths are actually required. In this case, the number of wavelengths available on the respective fibers depends on the number of optical fiber amplifiers deployed on each fiber. In this paper, we propose a heuristic algorithm for the design of a logical topology with as few optical fiber amplifiers as possible. Our results indicate that our algorithm reduces the number of optical fiber amplifiers with a slight increase of average packet delays.