Structural approach to nanoscience: a case study of complex and cluster formation in ZnBr2–ZnCl2 melts

Although the melt structure of glass-forming ZnCl₂ has so far been well studied, there exists quite little information on the structural change due to anion-substitution. In the present work, the short-range structure of ZnCl₂–ZnBr₂ mixture melts was analyzed systematically by time-of-flight pulsed neutron diffraction techniques, Raman spectroscopy, molecular orbital calculations, and molecular dynamics simulations. According to radial distribution analysis, it was found that there were tetrahedral structural units of ligand-substituted [ZnCl_nBr_4–n]^2– (n=0–4) in these melts, not implying the simple mixing of [ZnCl₄]^2– and [ZnBr₄]^2– units. Further detailed estimation indicated that the ligand-substituted complex anions were linked with each other by sharing a common anion.     

Identification of Pseudozyma graminicola CBS 10092 as a producer of glycolipid biosurfactants, mannosylerythritol lipids

A basidiomycetous yeast, Pseudozyma graminicola CBS 10092, was found to accumulate a large amount of glycolipids in the cultured medium when grown on soybean oil as the sole carbon source. Based on thin layer chromatography, the extracellular glycolipids gave spots corresponding to those of mannosylerythritol lipids (MELs), which are highly functional and promising biosurfactants. From the structural characterization by 1H and 13C NMR, the main product was identified as 4-O-[(4'-mono-O-acetyl-2', 3'-di-O-alka(e)noyl)-beta-D-mannopyranosyl]-D-erythritol, which is a highly hydrophilic derivative of MELs known as MEL-C. According to high-performance liquid chromatography analysis, the main product, MEL-C, comprised approximately 85% of all the MELs, and the total amount reached approximately 10 g/L for 7 days. The fatty acids of the present MEL-C consisted of mainly C6, C8 and C14 acids, considerably different from those of MEL-C produced by other Pseudozyma strains such as P. antarctica and P. shanxiensis. The observed critical micelle concentration (CMC) and the surface-tension at CMC of the MEL-C were 4.0 x 10(-6) M and 24.2 mN/m, respectively, while those of MEL-A, the most intensively studied MEL, were 2.7 x 10(-6) M and 28.4 mN/m, respectively. This implied that the MEL-C has higher hydrophilicity than conventional MELs hitherto reported. In addition, on a water-penetration scan, the MEL-C efficiently formed the lamella phase (Lalpha) at a wide range of concentrations, indicating its excellent self-assembling properties. From these results, the newly identified MELs produced by P. graminicola are likely to have great potential for use in oil-in-water type emulsifiers and/or washing detergents, and would thus facilitate a broad range of applications for the promising yeast biosurfactants.     

Characterization of sputtered triple layer photoactive coating with a glass-like appearance

Photocatalytic activity of sputtered TiO₂ single layer was investigated. From the results on the optical constants analyses and dark- and photo-conductivity measurements, it is revealed that the photocatalytic activities of TiO₂ films depend on the defect density of the TiO₂ films; the atomic defects act as recombination sites for photo-generated carriers diffusing to the TiO₂ surface. A three-layer system with a layer construction of SnO₂/TiO₂/Si₃N₄/Glass was designed for realizing the glass-like appearance, namely almost the same transmission and reflection spectra in visible wavelength region as those of glass, and its photocatalytic activity was investigated. The experimental results indicate that the interface between TiO₂ and SnO₂ acts as a potential barrier for the carriers photo-generated in the TiO₂ and the photo-generated species pass through the SnO₂ overlayer depending on the SnO₂ film characteristics.     

Design and synthesis of zero–zero-birefringence polymers in a quaternary copolymerization system

We designed and synthesized quaternary copolymers of methyl methacrylate (MMA), 2,2,2-trifluoroethyl methacrylate (TFEMA), benzyl methacrylate (BzMA), and 3,3,5-trimethylcyclohexyl methacrylate (TMCHMA) and we investigated their birefringence, thermal properties, and other optical properties. When the copolymer composition was MMA/TFEMA/BzMA/TMCHMA = 50:38:8:4, 40:30:7:23, or 30:21:7:42 (wt%), a zero–zero-birefringence polymer that exhibited neither orientational nor photoelastic birefringence was obtained. We demonstrated that such zero–zero-birefringence polymers with a variety of compositions could be successfully prepared in the quaternary system by using the same compensation method as applied in ternary random copolymerization. We also demonstrated that the glass-transition temperature (T_g) and refractive index (n_D) of these copolymers could be controlled with high accuracy while retaining their zero–zero-birefringence property. We can therefore predict the type of birefringence, the T_g, and the n_D of a particular copolymer before polymerization. Zero–zero-birefringence polymers with the most appropriate characteristics can then be synthesized selectively by quaternary copolymerization.     

Combination effect of phospholipids and n-3 polyunsaturated fatty acids on rat cholesterol metabolism

This study evaluated phospholipids (PLs) containing n-3 polyunsaturated fatty acids (n-3 PUFAs) for their specific inherent effects and effects due to a combination of the presence of glycerophosphate structure and n-3 PUFAs on cholesterol metabolism in rats. Rats were fed a diet of AIN-93G containing soybean oil (SO, 7%), SO (5.8%)+fish oil (1.2%), SO (5.2%)+soybean PLs (1.8%), SO (5.2%)+PLs containing n-3 PUFAs (1.8%), and SO (4.0%)+fish oil (1.2%)+soybean PLs (1.8%). Diets with PLs containing n-3 PUFAs, and soybean PLs in combination with fish oil, resulted in decreased serum and liver cholesterol levels through enhancement of fecal cholesterol excretion and suppression of liver sterol regulatory element binding protein-2 mRNA expression compared with the diet containing soybean oil alone. This study shows that soybean PLs with added triacylglycerol that included n-3 PUFAs have the same effects on cholesterol metabolism as PLs containing n-3 PUFAs, and that these could be of benefit to people.     

Fabrication of discrete polystyrene nanoparticle arrays with controllable their structural parameters

We have demonstrated the fabrication of two-dimensionally periodic non-close packed arrays of spherical polystyrene nanoparticles with controllable their structural parameters including diameter and interpartcile distance. The principle of this procedure relies on stepwise integration of spin-coat-assisted colloidal self-assembly of the single layer of close-packed polystyrene nanoparticle on a substrate, and subsequent etching of the particle under atmospheric pressure helium plasma. The plasma process converted the close-packed nanoparticle array into non-close-packed arrangement remaining with unchanged their original spherical shape and periodicity. Owing to the etching process underwent isotropically, the structural parameters could be controlled with nanometric accuracy by the treatment time. The etching rate strongly depended on the working pressure conditions, and the etching rate under 250 Torr was ca. 3 times faster than that of the 760 Torr. The effects of the working pressure indicated the neutral helium radicals and photons diffused from the plasma might be primarily responsible for the etching.     

Damage of yeast cells induced by pulsed light irradiation

DNA damage, such as formation of single strand breaks and pyrimidine dimers was induced in yeast cells after irradiation by pulsed light, which were essentially the same as observed with continuous ultraviolet (UV) light. The UV-induced DNA damage is slightly higher than seen with pulsed light. However, increased concentration of eluted protein and structural change in the irradiated yeast cells were observed only in the case of pulsed light. A difference in the inactivation effect between pulsed light and UV light was found and this suggested cell membrane damage induced by pulsed light irradiation. It is proposed that pulsed light can be used as an effective sterilizing method for the yeast Saccharomyces cerevisiae.     

A novel method to improve low‐voltage ride‐through capability of wind turbine generators

With increasing penetration of wind farms, power grids have responded by developing specific grid codes to maintain their stability. One of the main grid codes is the low‐voltage ride‐through (LVRT) capability, which requires the wind generator to remain connected when the grid voltage sags for a certain time period. A wind farm with squirrel cage induction generators suffers this LVRT problem the most because of their direct connection to the grid and reactive power consumption. In this paper, a new method is proposed to solve this problem by shunt‐connecting a motor‐driven mechanical load to the cage wind generator. For driving mechanical loads, the induction motor is most widely used in industries. This paper studies the terminal voltage holding effect of an induction machine during grid voltage sag due to the magnetic flux holding effect and the saturation characteristic. Taking advantage of this effect, the induction motor that is used for driving mechanical load is then proposed to improve the LVRT capability of wind turbine generators. Furthermore, the change of the rotating speed or slip of the induction machine is found to have a great impact on improving the LVRT. By adding some inertia to the motor‐driven mechanical load, an enhanced voltage holding effect, and therefore LVRT improvement, is expected for the wind farm. Both simulation and experimental results prove the effectiveness of the proposed method. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Study of molecular behavior in oxidation of insulating oil using terahertz spectroscopy

The stock of aged power equipment is increasing and it is important to clarify the characteristics of deteriorated insulating oil. This paper describes a basic study of molecular behavior in the oxidation of insulating oil by terahertz spectroscopy. The oxidation of insulating oil was modeled by using various compositions of dodecane and 2‐octanol. The terahertz measurements indicated that signi?cant absorption related to hydroxyl groups (‐OH) occurred between 6 and 7 THz. The absorption band was also observed in accelerated aging alkylbenzene, which is used in power equipment as insulating oil and is sensitive to hydrogen bonds. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(1): 9–15, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22335