Topotaxy of Corundum-Type Tetramagnesium Diniobate and Ditantalate Layers on Rock-Salt-Type Magnesium Oxide Substrates

In-plane alignments were found to occur in the product layers of corundum-type Mg₄Nb₂O₉ (MNO) and Mg₄Ta₂O₉ (MTO) on rock-salt-type MgO(001) substrates as a result of a topotaxial interface reaction between a Nb₂O₅ (or Ta₂O₅) precursor and MgO at 800°C and higher. Such alignments were attributed to a topotaxial formation of (114)-oriented MNO (or MTO) layers. This (114) orientation is hidden in the conventional XRD theta-2theta scans due to an overlap of the film (114) peak with the substrate peak, MgO(002). Its presence was revealed by XRD pole-figure measurements. The crystallographic relationship between MNO(114) [or MTO(114)] and MgO(001) is also discussed.     

Identification of system characteristics of a power system with time series data. Identification of frequency fluctuation characteristics of a small‐scale isolated system

Understanding actual characteristics of a power system with recorded time series data is of great importance, for example, in improving the performance of the system. Although system identification is a well‐known technique to achieve this goal, its applicability to a certain system should be examined for the particular case because its accuracy highly depends on the inherent characteristics of the system. While many papers have discussed application of a system identification technique to a power system, few papers have examined its applicability to the actual data of a power system. This paper presents a new system identification method to estimate characteristics of a power system while using output of intermittent generators or fluctuating loads as an external disturbance. The method employs cross spectra and coherence as a key factor in the identification; it estimates a transfer function of a power system, contribution of observed disturbance to total disturbance, and so on. The method is applied to time series data of two model systems: simulation results and measured data of an isolated power system with diesel generators. The study gives satisfactory results; implication on the accuracy of the method is discussed through the sample studies. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(3): 36–45, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20051     

Electrolytic aggregation treatment without coagulant dosage for retentate

An electrolytic treatment promoting aggregation compatible with the production of a dense aggregate was developed and studied in a batch test to thicken the retentate without coagulant dosage. A kaolin suspension with turbidity of about 200 NTU with a large fraction of fine particulates was used as the retentate. The aggregation of the electrochemically treated suspension increased with increasing mixing intensity in the range of 40–160 rpm for 5 min. The electrolytic treatment could also decrease the residual turbidity at the retention of about 150 h to one-fourth that of the untreated suspension, and moreover did not significantly change the sludge concentration, in contrast to the decreased sludge concentration of the acidified suspension maintained in the pH range of 4.5–5.0. A positive shift of the surface charge of particulates observed in the treated suspension suggests that the particle destabilization occurred in a pH range of 5.5–7.0, because of the hydrolysis of Al ions released electrochemically from kaolin clay.     

Antioxidation reaction mechanism studies of phenolic lignans,identification of antioxidation products of secoisolariciresinol from lipid oxidation

The chain-breaking antioxidation reaction mechanism of a phenolic lignan in a lipid oxidation system was investigated. The 2,2′-azobis(isobutyronitrile) (AIBN)-induced radical oxidation reaction in a large amount of ethyl linoleate in the presence of secoisolariciresinol, one of the potent antioxidative lignans widely distributed in edible plants, produced two types of peroxides as radical termination products, as well as a cyclic derivative. The isolation and structure determination of the peroxides revealed that they have a peroxide linkage with ethyl linoleate or isobutyronitrile at the 1-position of the benzene ring of secoisolariciresinol. The cyclic derivative was also identified as lariciresinol by spectroscopic analysis. Based on the chemical structures of these products, a reaction pathway for the antioxidation reaction of secoisolariciresinol in oxidising lipid media was proposed.     

Green leaf volatiles enhance methyl jasmonate response in Arabidopsis

Plants emit green leaf volatiles (GLVs) in response to insect or pathogen damage. GLVs consist of C6 and C9 aldehydes, alcohols, and their acetate esters, and play important roles in the plant defense response. One of the functions of GLVs in the defense response is priming. Plants pretreated by GLVs can induce a defense response more rapidly and effectively than unpretreated plants when they are damaged by pathogens or insects. In this study, we focused on the priming effects of GLVs on jasmonic acid response involved in the defense response. When Arabidopsis was pretreated with aldehyde GLVs, especially with (E)-2-hexenal, the anthocyanin content was significantly increased by a subsequent methyl jasmonate (MeJA) treatment. On the other hand, no effect of anthocyanin accumulation was observed for plants pretreated with alcohol GLVs. These results suggest that aldehyde GLVs, especially (E)-2-hexenal, could enhance sensitivity to MeJA in Arabidopsis.     

Non-peripheral octahexylphthalocyanine doping effects in bulk heterojunction polymer solar cells

The improvement of long-wavelength sensitivity in bulk heterojunction organic thin-film solar cells based on poly(3-hexylthiophene) (P3HT) by the addition of the soluble phthalocyanine derivative, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH₂) is reported. C6PcH₂ possesses near-infrared absorption and can be mixed with a P3HT:1-(3-methoxy-carbonyl)-propyl-1-1-phenyl-(6,6)C61 (PCBM) bulk heterojunction active layer. By doping C6PcH₂, the photosensitivity in the long-wavelength region was improved, and the energy conversion efficiency reached 3.0% at a composition ratio of P3HT:C6PcH₂:PCBM = 10:3:10. We discuss the principle of photoconversion in the bulk heterojunction solar cell based on the P3HT:C6PcH₂:PCBM active layer by taking into consideration the existence of both highly ordered P3HT domains and hexagonal columnar structures of C6PcH₂, and the microphase separation of P3HT and C6PcH₂ in the active layer.     

Deposition of atmospheric (137)Cs in Japan associated with the Asian dust event of March 2002

Considerable deposition of (137)Cs was observed in the northwestern coastal area of Japan in March 2002. Since there were no nuclear explosions or serious nuclear accidents in the early 2000s, transport of previously contaminated dust appears to be the only plausible explanation for this event. In March 2002, there was a massive sandstorm on the East Asian continent, and the dust raised by the storm was transported across the sea to Japan. This dust originated in Mongolia and northeastern China, in an area distant from the Chinese nuclear test site at Lop Nor or any other known possible sources of (137)Cs. Our radioactivity measurements showed (137)Cs enrichment in the surface layer of grassland soils in the area of the sandstorm, which we attributed to accumulation as a result of past nuclear testing. We suggest that the grassland is a potential source of (137)Cs-bearing soil particles. Since the late 1990s, this area has experienced drought conditions, resulting in a considerable reduction of vegetation cover. We attribute the prodigious release of (137)Cs-bearing soil particles into the atmosphere during the sandstorm and the subsequent deposition of (137)Cs in Japan to this change.     

Evaluation of crack nucleation site and mechanical properties for friction stir welded butt joint in 2024-T3 aluminum alloy

In this paper, metallographic observations, hardness measurement, and static and fatigue tests were conducted to investigate the discontinuity states which become crack nucleation sites in friction stir welded butt joints in 2-mm-thick 2024-T3 aluminum alloy and static and fatigue properties of the joint. Because different types of surface finish can be used depending on the application of the joint, several types of surface conditions were tested to evaluate their effect on crack nucleation sites and static and fatigue life. Indentation hardness tests revealed that typical hardness reduction is not necessarily observed on the section of the welding line. Based on fatigue test results, it was confirmed that there are several types of crack nucleation sites for friction stir welding (FSW) joints depending on the surface finish, and the features of the fracture surface also differ depending on the site. Furthermore, the type of discontinuity state affects the fatigue life of the FSW joint.     

Observation of negative differential resistance and single-electron tunneling in electromigrated break junctions

We observed a negative differential resistance (NDR) along with single-electron tunneling (SET) in the electron transport of electromigrated break junctions with metal-free tetraphenylporphyrin (H₂BSTBPP) at a temperature of 11 K. The NDR strongly depended on the applied gate voltages, and appeared only in the electron tunneling region of the Coulomb diamond. We could explain the mechanism of this new type of electron transport by a model assuming a molecular Coulomb island and local density of states of the source and the drain electrodes.     

Effective catalyst on SiO2 in ethanol CVD for growth of single-walled carbon nanotubes

We have compared catalytic activity of Co and Fe in a growth process of single-walled carbon nanotube (SWNT) by chemical vapor deposition using ethanol as a carbon source and SiO₂ as a catalyst-supporting material. Changes of the catalyst precursors (Co- and Fe acetate) in the growth process were carefully observed at three different stages: (i) after oxidation in air at 400 °C but before heating to the growth temperature (800 °C), (ii) after heating to the growth temperature in flowing Ar and H₂ but before starting the nanotube growth and (iii) after the growth process is over. During the growth of SWNT, the Co catalyst took the form of β-Co, resulting in a high yield growth. On the contrary, the Fe catalyst formed a silicate, Fe₂SiO₄, showing a poor catalytic ability. Our result shows that chemical reactions between the catalyst precursors and their supporting materials sensitively affect the catalytic ability.