Consideration on the Relationship Between Dielectric Breakdown Voltage and Water Content in Fatty Acid Esters

Mineral oil is commonly used as an electrical insulating oil in transformers because of its relatively high electrical insulating ability and fluidity. Considering the depletion of resources and environmental problems, however, fatty acid esters synthesized from natural plant oils are attracting attention as an environmentally friendly insulating oil. In addition, fatty acid esters such as methyl octanoate, methyl dodecanoate, 2-ethylhexyl octanoate, and 2-ethylhexyl dodecanoate have high fluidity, and also show excellent moisture tolerance against dielectric breakdown compared to mineral oil. In the present study, to clarify the reason for the superior moisture tolerance of fatty acid esters, the status of dissolved water in esters is investigated with IR spectroscopic measurements and density functional theory (DFT) calculations. It is revealed that water molecules in fatty acid esters are trapped by the ester moiety of fatty acid esters. As a result, fatty acid esters have a higher moisture tolerance against dielectric breakdown than mineral oil.     

Novel screening system for protein-protein interactions by bimolecular fluorescence complementation in Saccharomyces cerevisiae

For high-throughput screening of protein-protein interactions, we have developed a novel yeast screening system using Bimolecular fluorescence complementation (BiFC). Two yeast plasmids, in which genes of heterodimerized peptides LZA and LZB were each fused with those of non-fluorescent half fragments of Kusabira-Green mutant (mKG2), were transformed into a- and α-type yeast, respectively. Mating of them gave a library, which was screened by following green fluorescence resulted from LZA-LZB interaction. The method showed potential ability to detect the positive clones from a model library, in which green-fluorescent and non-fluorescent yeast was mixed in a ratio of 1:675.     

Effect of Microstructural Control on Thermoelectric Properties of Hot-Pressed Aluminum-Doped Zinc Oxide

The thermal conductivity of polycrystalline Al-doped ZnO was controlled through the fabrication of nanostructured polycrystalline materials, by hot-pressing nanosized Zn_{1– x} Al _x O ( x = 0.01, 0.02) particles, which were synthesized by a coprecipitation and spray-drying method. This process resulted in an improved thermoelectric power factor because of the nanosized Zn_0.99Al_0.01O particles of the polycrystalline products. The thermal conductivity also was decreased as a result of the formation of nanocrystalline Zn_0.99Al_0.01O.     

How to identify water from thickener aqueous solutions by touch

Water detection is one of the most crucial psychological processes for many animals. However, nobody knows the perception mechanism of water through our tactile sense. In the present study, we found that a characteristic frictional stimulus with large acceleration is one of the cues to differentiate water from water contaminated with thickener. When subjects applied small amounts of water to a glass plate, strong stick-slip phenomena with a friction force of 0.46 ± 0.30 N and a vertical force of 0.57 ± 0.36 N were observed at the skin surface, as shown in previous studies. Surprisingly, periodic shears with acceleration seven times greater than gravitational acceleration occurred during the application process. Finite-element analyses predicted that these strong stimuli could activate tactile receptors: Meissner''s corpuscle and Pacinians. When such stimuli were applied to the fingertips by an ultrasonic vibrator, a water-like tactile texture was perceived by some subjects, even though no liquid was present between the fingertip and the vibrator surface. These findings could potentially be applied in the following areas: materials science, information technology, medical treatment and entertainment.     

Nickel‐Catalyzed Suzuki–Miyaura Coupling of a Tertiary Iodocyclopropane with Wide Boronic Acid Substrate Scope: Coupling Reaction Outcome Depends on Radical Species Stability

We describe a nickel‐catalyzed Suzuki–Miyaura arylation of a tertiary iodocyclopropane with arylboronic acids; this is an efficient and convergent strategy for providing various enantioenriched arylcyclopropanes with a quaternary stereogenic center. This is the first metal‐catalyzed coupling between a tertiary alkyl electrophile and a wide range of aromatics, including heteroaromatics. We found that the outcome of the Ni‐catalyzed coupling with halides as electrophiles was dependent on the stability of the radical species formed during the reaction. The use of tert‐butyl alcohol (t‐BuOH) as the reaction solvent was very effective, because of its stability under the radical‐generating reaction conditions.

     

Direct Formation of Crystalline Gadolinium-Doped Ceria Powder via Polymerized Precursor Solution

Synthesis of Ce_0.9Gd_0.1O_1.95 (CGO) powder from a polymeric precursor solution containing a mixture of nitrates, nitric acid, and ethylene glycol was investigated with emphasis on the effect of polymerization of the precursor solution on the crystallization and morphology of the derived solid intermediate and the final oxide powder. It is shown for the first time in this work that the solid intermediate derived from the polymerized solution is present in the form of well-crystallized cerium-gadolinium formate solid solution, Ce_{1− x} Gd _x (HCOO)₃, exhibiting anisotropic growth. Further polymerization of the precursor solution resulted in the direct formation of loosely agglomerated nanoscaled CGO oxide powder from the polymerized solution at temperatures as low as 130°C.     

Toughening of Silicon Nitride Matrix Composites by the Addition of Both Silicon Carbide Whiskers and Silicon Carbide Particles

Si₃N₄ matrix composites reinforced by SiC whiskers, SiC particles, or both were fabricated using the hot-pressing technique. The mechanical properties of the composites containing various amounts of these SiC reinforcing materials and different sizes of SiC particles were investigated. Fracture toughness of the composites was significantly improved by introducing SiC whiskers and particles together, compared with that obtained by adding SiC whiskers or SiC particles alone. On increasing the size of the added SiC particles, the fracture toughness of the composites reinforced by both whiskers and particles was increased. Their fracture toughness also showed a strong dependence on the amount of SiC particles (average size 40 μm) and was a maximum at the particle content of 10 vol%. The maximum fracture toughness of these composites was 10.5 MPa·m^1/2 and the flexural strength was 550 MPa after addition of 20 vol% of SiC whiskers and 10 vol% of SiC particles having an average particle size of 40 μm. These mechanical properties were almost constant from room temperature to temperatures around 1000°C. Fracture surface observations revealed that the reinforcing mechanisms acting in these composites were crack deflection and crack branching by SiC particles and pullout of SiC whiskers.     

High tensile strength fiber of poly[(R)‐3‐hydroxybutyrate‐co‐(R)‐3‐hydroxyhexanoate] processed by two‐step drawing with intermediate annealing

High tensile strength fibers of poly[(R)‐3‐hydroxybutyrate‐co‐(R)‐3‐hydroxyhexanoate] [P(3HB‐co‐3HH)], a type of microbial polyesters, were processed by one‐step and two‐step cold‐drawn method with intermediate annealing. Thermal degradation behaviors were characterized by differential scanning calorimeter and gel permeation chromatography measurements. Thermal analyses were revealed that molecular weights decreased drastically within melting time at a few minute. One‐step cold‐drawn fiber with drawing ratio of 10 showed tensile strength of 281 MPa, while tensile strength of as‐spun fiber was 78 MPa. When two‐step drawing was applied for P(3HB‐co‐3HH) fibers, the tensile strength was led to 420 MPa. Furthermore, the optimization of intermediate annealing condition leads to enhance the tensile strength at 552 MPa of P(3HB‐co‐3HH) fiber. Wide‐angel X‐ray diffraction measurements of these fibers suggest that the fibers with high tensile strength include much amount of the planer‐zigzag conformation (β‐form) as molecular conformation together with 2₁ helix conformation (α‐form). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41258.     

Study of crater formation and sputtering process with large gas cluster impact by molecular dynamics simulations

Molecular dynamics (MD) simulations of large argon clusters impacting on silicon solid targets were performed in order to study the transient process of crater formation and sputtering. The MD simulations demonstrate that the initial momentum of incident cluster is transferred to target surface atoms through multiple collision mechanism, where the initial momentum, which is along to the surface normal before impact, is deflected to lateral direction. This momentum transfer process was analyzed by the calculation of the velocity at the crater edge (the interface between cluster and target). In the case of Ar₁₀₀₀ cluster impact on Si(1 0 0) target at low energy per atom less than 40 eV/atom, the maximum value of lateral velocity of the crater edge increases in proportional to the velocity of incident cluster atoms. On the other hand, the crater edge velocity saturates over 40 eV/atom of incident energy per atom. In this case, the whole of constituent cluster atoms are implanted into the target and expand in both lateral and reflective directions at the subsurface region of the target. These MD simulations demonstrated that this collisional process result in the high yield sputtering of the target atoms.