Synthesis of Nanohole‐Structured Single‐Crystalline Platinum Nanosheets Using Surfactant‐Liquid‐Crystals and their Electrochemical Characterization

Nanohole‐structured single‐crystalline Pt nanosheets have been synthesized by the borohydride reduction of Na₂PtCl₆ confined to the lyotropic liquid crystals (LLCs) of polyoxyethylene (20) sorbitan monooleate (Tween 80) with or without nonaethylene‐glycol (C₁₂EO₉). The Pt nanosheets of around 4–10 nm in central thickness and up to 500 nm or above in diameter have a number of hexagonal‐shaped nanoholes ∼1.8 nm wide. High‐resolution electron microscope images of the nanosheets showed atomic fringes with a spacing of 0.22 nm indicating that the nanosheets are crystallographically continuous through the nanoholed and non‐holed areas. The inner‐angle distributions for the hexagonal nanoholes indicate that the six sides of the nanoholes are walled with each two Pt (111), Pt (1 1) and Pt (010) planes. The formation mechanism of nanoholed Pt nanosheets is discussed on the basis of structural and compositional data for the resulting solids and their precursory LLCs, with the aid of similar nanohole growth observed for a Tween 80 free but oleic acid‐incorporated system. It is also demonstrated that the nanoholed Pt nanostructures loaded on carbon exhibit fairly high electrocatalytic activity for oxygen reduction reaction and a high performance as a cathode material for polymer‐electrolyte fuel cells, along with their extremely high thermostability revealed through the effect of electron‐irradiation.     

Analysis of a coal-derived liquid using highpressure liquid chromatography and synchronous fluorescence spectrometry

Synchronous fluorescence spectra of model polycondensed aromatic hydrocarbon molecules were recorded and used to identify the number of condensed rings in the aromatic molecules. A coal-derived liquid from Yubarishinko coal was initially separated into fractions having different number of condensed aromatic rings, and each fraction was further divided into narrow fractions having different numbers of carbon atoms. These fractions were studied using synchronous fluorescence spectroscopy. Results indicate the potential usefulness of synchronous fluorescence spectroscopy as a method of analysis of complex mixtures as coal-derived liquids despite the limitation of the method that some molecules give only weak peaks. Several components in some fractions were identified by a combination of synchronous fluorescence spectra and conventional excitation and emission fluorescence spectra.     

Segmented chirped grating for coarse wavelength division demultiplexing with multimode optical fibers

A chirped grating segmented into partitions each having a constant blaze angle to use in a demultiplexer for coarse wavelength division multiplexing with multimode optical fibers is developed. Its designed configuration utilizes a resonance region to achieve high diffraction efficiency and large dispersion. The width, blaze angle, and diffraction order of each partition were optimized by vector diffraction analysis. The diffraction loss of the manufactured grating was less than 1.5 dB, and polarization-dependent loss was less than 0.6 dB within a wavelength width of at least 70 nm. It is confirmed that a demultiplexer with the developed chirped grating had a wide passband and low cross talk.     

Effects of insufficient air injection on methanogenic Archaea in landfill bioreactor

In this study, methanogenic Archaea diversity in an aerated landfill bioreactor filled with co-disposed incineration bottom ashes and shredded incombustible wastes was monitored and analyzed as a function of time using molecular techniques. Besides, the effects of insufficient air injection on the bioreactor performance and methanogenic diversity were evaluated thoroughly. Results indicated that rapid bio-stabilization of solid waste are possible with aerated landfill bioreactor at various oxygen and oxidation reduction potential levels. Slot-blot hybridization results of leachate samples collected from aerated landfill bioreactor showed that archaeal and bacterial activities increased as stabilization accelerated and bacterial populations constituted almost 95% of all microorganisms. The results of slot-blot hybridization and phylogenetic analysis based on 16S rRNA gene revealed that Methanobacteriales and Methanomicrobiales were dominant species at the beginning while substituted by Methanosarcina-related methanogens close to the end of the operation of bioreactor.     

Large eddy simulation of swirling jet in a bluff-body burner

The large eddy simulation (LES) is applied to an unconfined swirling flow of an air surrounding a bluff-body having a central jet of air, and the complicated flowfield that involves the recirculation and vortex breakdown is investigated. The Smagorinsky model is used as the sub-grid scale model. The results of the present numerical simulation are compared with the experimental data of the mean and stochastic root mean square (RMS) variations of two velocity components. Although the inflow conditions are specified in a simple manner, the obtained numerical results are in reasonable agreement with the experiments, except for a part of RMS variation values near downstream of the bluff body. The present numerical calculations can successfully reproduce the two characteristics of the flow, i.e., an upstream recirculation zone established just downstream of the burner plane and the additional recirculation zone established at the more downstream location.     

Aberration properties in a chirped grating for coarse wavelength division demultiplexing

We studied the imaging performance of a chirped grating for a demultiplexer designed for coarse wavelength division multiplexing using a wavefront aberration analysis and the ray tracing simulation. The demultiplexer was composed of a chirped grating, cylindrical lenses, and a waveguide. The best image point and the spot shape focused by the chirped grating were effectively calculated with the wavefront aberration. We applied the aberration analysis to design a waveguide to connect branched beams to photodetectors, and we confirmed the demultiplexing performance experimentally.     

Recovery of population inversion in an erbium-doped fiber amplifier observed by temporally resolving amplified spontaneous emissions

We report on the recovery of population inversion in a CW-pumped erbium-doped fiber amplifier. Spontaneous emissions after the input of signal pulses were temporally resolved. The recovery time for population inversion was estimated to be a few hundred microseconds. The pump power and signal width dependences of the recovery were measured. We discuss the dependences by applying an analytical formula derived for the temporal evolution of population inversion.     

Simultaneous visualization of oxygen distribution and water blockages in an operating triple-serpentine polymer electrolyte fuel cell

Visualization inside polymer electrolyte fuel cells (PEFCs) is important for elucidating reaction distributions to improve the performance and durability of the cells. An O₂-sensitive porphyrin luminescent dye film was used to visualize oxygen partial pressures and water blockages simultaneously in triple-serpentine gas flow channels in an operating PEFC. Water droplets formed near the exit of a gas-flow channel lowered the oxygen partial pressure noticeably over the channel by blocking air flow near the entrance. Meanwhile, air was continuously supplied from the other channels through the gas diffusion layer, thus allowing power to be generated in the blocked channel. With water blockages, however, the catalyst layer under the channel became flooded by the water produced during the reaction, and the flooded state continued to exist in the catalyst and/or porous layers, even after blowing the water droplet out, so that the power generation was lowered along the channel.     

Acrylamide elution from roasted barley grains into mugicha and its formation during roasting

This paper investigated acrylamide elution from roasted barley grain into mugicha and its formation during roasting of the grain. Mugicha is an infusion of roasted barley grains. Highly water-soluble acrylamide was easily extracted to mugicha from milled roasted barley grains in teabags. On the other hand, the acrylamide concentration in mugicha prepared from loose grain increased with longer simmering and steeping times. During roasting in a drum roaster, the acrylamide concentration of the grain increased as the surface temperature rose, reaching a maximum at 180–240°C. Above this temperature, the acrylamide concentration decreased with continued roasting, exhibiting an inverted ‘U’-shaped curve. For most of the samples, the acrylamide concentration showed good correlation with the value of the colour space parameter L*. The dark-coloured roasted barley grains with lower L* values contained lower amounts of acrylamide as a result of deep roasting. The level of asparagine in barley grains was found to be a significant factor related to acrylamide formation in roasted barley products. The data are an important contribution to the mitigation of acrylamide intake from mugicha.     

Gain saturation of a CW-pumped erbium-doped fiber amplifier for nanosecond pulses

We report on the gain saturation property of an erbium-doped fiber amplifier for high peak 100 ns pulses. Under CW pumping conditions, the 980 nm pump power dependence of the gain saturation is precisely measured. Pump power dependence is discussed by assuming that the pulse width is much shorter than the recovery time of the erbium population inversion.