The Formation of β‐Damascenone in Sweet Potato Shochu

The formation of β‐damascenone during shochu manufacture was investigated by quantifying β‐damascenone at each stage of manufacturing. Steamed sweet potato has a low level of free β‐damascenone (0.02–0.1 μg/g). During fermentation, β‐damascenone was produced in small quantities that were degraded by yeast. Thus, the second mash accumulates little free β‐damascenone (approximately 17 μg/L). The concentration profile in the fractionated distillate showed that β‐damascenone was produced during heating. Most β‐damascenone in shochu was formed during distillation, not during steam heating and fermentation. It is suggested that the level of β‐damascenone in shochu could be increased by reducing the pH of the second mash and prolonging the distillation period. Sweet potato cultivars differed in total free and hydrolyzed β‐damascenone content and there was a strong association between each cultivar and its shochu β‐damascenone content. The selection of the sweet potato cultivar is important for determining the quantity of β‐damascenone in a shochu brew.     

One-Pot Formation of a Metallosupramolecularly Assembled and Redox-Active Adlayer at the Solid–Liquid Interface

A redox-active adlayer consisting of cobalt ions and terpyridine ligands, 4′,4′′′′-(1,4-phenylene)bis(2,2′:6′,2′′-terpyridine), was prepared on a Au(111) surface by a stepwise coordination method. The obtained adlayer produced a well-defined, stable redox wave associated with cobalt ions coordinated to 4′,4′′′′-(1,4-phenylene)bis(2,2′:6′,2′′-terpyridine), as compared to a tetra-2-pyridinyl-pyrazine adlayer, for which no redox wave was observed. In situ scanning tunneling microscopy revealed a structural change in the redox-active adlayer consisting of 4′,4′′′′-(1,4-phenylene)bis(2,2′:6′,2′′-terpyridine) and cobalt ions. It was found that the ability of cobalt ions to coordinate on Au(111) was clearly dependent on the chemical structure of the ligand, suggesting that ligand coordination with metal ions on the Au surface is determined by the molecular orientation and configuration of the ligand when the ligand is adsorbed on a Au substrate.     

Effect of film thickness on electrical property of microcrystalline silicon

We report dependences of electrical properties on SiH₄/H₂ dilution rate and film thickness for microcrystalline silicon films formed by a hydrogen radical-induced chemical vapor deposition (HRCVD) method. The electrical conductivity of the films at SiH₄ 18 sccm /H₂ 120 sccm was markedly increased to 10⁻³ S/cm as film thickness increased above 100 nm. Crystalline grains with (2 2 0) orientation were formed. Theoretical analysis revealed that grain boundaries among (2 2 0) grains had a low defect density of 1×10¹² cm⁻² so that the high conductivity was achieved.     

Characterization of pulsed laser crystallization of silicon thin film

Increases in the melt duration of silicon films were achieved by electrical current heating during and after pulsed excimer laser heating. When 50 nm thick amorphous silicon films formed on glass substrate were irradiated by 28-ns-pulsed excimer by applying 1.8 μs long pulsed-voltage at 100 V to the films, the silicon films were melted for the duration of the voltage pulse. The power threshold for heat energy for this long melting by the self-heating effect of the silicon films was 3.0×10⁵ W/cm². The high electrical conductivity of the silicon film (2.9×10⁻² S/cm) was found after regrowth of the silicon using a laser energy density of 360 mJ/cm² and a pulsed voltage of 150 V. The advantages of the long melt duration for large crystalline growth are discussed.     

Evaluation of defects generation in crystalline silicon ingot grown by cast technique with seed crystal for solar cells

Although crystalline silicon is widely used as substrate material for solar cell, many defects occur during crystal growth. In this study, the generation of crystalline defects in silicon substrates was evaluated. The distributions of small-angle grain boundaries were observed in substrates sliced parallel to the growth direction. Many precipitates consisting of light elemental impurities and small-angle grain boundaries were confirmed to propagate. The precipitates mainly consisted of Si, C, and N atoms. The small-angle grain boundaries were distributed after the precipitation density increased. Then, precipitates appeared at the small-angle grain boundaries. We consider that the origin of the small-angle grain boundaries was lattice mismatch and/or strain caused by the high-density precipitation.     

Analysis of free-carrier optical absorption used for characterization of microcrystalline silicon films

The analysis of free-carrier optical absorption was applied to investigation of electrical properties for doped microcrystalline silicon films formed at 100–180°C by the RF-plasma-enhanced chemical vapor deposition method. The analysis gave in-depth characteristics of the carrier mobility and the carrier density. The electron mobility was 8 cm²/Vs (phosphorous doped) and 6 cm²/Vs (boron doped) at the surface region and it decreased to 1 cm²/Vs at bottom film/substrate interfaces. The carrier mobility and density were much higher than those obtained by Hall effect current measurements. It shows the existence of substantial non-activated and disordered regions among crystalline grains.     

Effect of the Amount of Gases on the Foaming Efficiency of Porous Aluminum Using Die Castings Fabricated by Friction Stir Processing

Porous aluminum was fabricated by friction stir processing using the gases intrinsically contained in aluminum alloy die castings without the use of a blowing agent. The effect of the amount of gases contained in the die castings on the foaming efficiency was investigated. Although the expansion efficiency of each type of gas was not clear, the total amount of gases was sufficient to obtain high porosity. A porosity of approximately 60 pct was obtained with highly spherical and fine pores.     

Analysis of Volatile Compounds in Shochu Koji,Sake Koji,and Steamed Rice by Gas Chromatography‐Mass Spectrometry

The volatile compounds in three types of koji (yellow, white, and black) and steamed rice were investigated using gas chromatography‐mass spectrometry. The objective of this study was to characterize each koji type based on its profile of volatile compounds. From the steamed rice and rice koji samples examined, a total of 29 volatile compounds were identified. Butanal, hexanal, dimethyl trisulfide and cyclohexyl isothiocyanate were detected only in steamed rice. The volatile profile of yellow koji (sake koji) was distinct from those of white and black kojis (shochu koji). On the basis of relative peak areas, alcohols and aldehydes were identified as being more abundant in yellow koji. White and black kojis had similar volatile profiles, and had a greater abundance of furans than yellow koji. We assume that the different suites of volatile compounds identified in shochu and sake kojis impart the respective characteristic flavours to shochu and sake.     

A Freestanding GaN/HfO $_{bf 2}$ Membrane Grown by Molecular Beam Epitaxy for GaN–Si Hybrid MEMS

Combination of GaN light source and Si-microelectromechanical systems (MEMSs) is a promising hybrid structure for optical MEMS. As one of GaN-Si hybrid structures, a freestanding GaN/HfO₂ membrane was fabricated on Si substrate. Unlike conventional GaN membrane on Si substrate, the fabricated membrane had a tensile stress by using the HfO₂ layer. Therefore, the GaN/HfO₂ membrane was flat enough to be useful for several MEMS. The GaN crystal was grown by molecular beam epitaxy on the HfO₂ layer deposited on Si substrate. The surface of the HfO₂ layer was nitrified before GaN crystal growth, and thus, a part of HfO₂ surface was changed to HfN, the lattice of which matched well to that of GaN. The characteristics of the GaN crystal grown on the nitrified HfO₂ layer were also investigated.