Synergistic Extraction of Am(III) and Eu(III) by Tris(2‐pyridylmethyl)Amine with Various Anions in 1,2‐Dichloroethane

The extraction equilibria of Am(III) and Eu(III) by using a tripodal ligand, tris(2‐pyridylmethyl)amine (tpa), with various lipophilic anions have been investigated. The extractability of both Am(III) and Eu(III) was increased by the combination of tpa and counteranions due to a synergistic effect. The separation factors between Am(III) and Eu(III) were also increased from 7.6 to 49 by the combination of counteranions and organic solvents. The extraction equilibria of Am(III) and Eu(III) with tpa in 1,2‐dichloroethane were determined by slope analysis. It was found that three anions and one molecule of the ligand coordinated to Am(III) and Eu(III) was extracted regardless of the anions.     

Efficient electrochemical decomposition of perfluorocarboxylic acids by the use of a boron-doped diamond electrode

The electrochemical decomposition of environmentally persistent perfluorooctanoic acid (PFOA) was achieved by the use of a boron-doped diamond (BDD) electrode. The PFOA decomposition follows pseudo-first-order kinetics, with an observed rate constant (k₁) of 2.4 × 10^− 2 dm³ h^− 1. Under the present reaction conditions, k₁ increased with increasing current density and saturated at values over 0.60 mA cm^− 2. Therefore, the rate-limiting step for the electrochemical decomposition of PFOA was the direct electrochemical oxidation at lower current densities. In the proposed decomposition pathway, direct electrochemical oxidation cleaves the C-C bond between the C₇F₁₅ and COOH in PFOA and generates a C₇F₁₅ radical and CO₂. The C₇F₁₅ radical forms the thermally unstable alcohol C₇F₁₅OH, which undergoes F⁻ elimination to form C₆F₁₃COF. This acid fluoride undergoes hydrolysis to yield another F⁻ and the perfluorocarboxylic acid with one less CF₂ unit, C₆F₁₃COOH. By repeating these processes, finally, PFOA was able to be totally mineralized to CO₂ and F⁻. Moreover, whereas the BDD surface was easily fluorinated by the electrochemical reaction with the PFOA solution, medium pressure ultraviolet (MPUV) lamp irradiation in water was able to easily remove fluorine from the fluorinated BDD surface.     

Peptide and protein mimetics inhibiting amyloid beta-peptide aggregation

Protein misfolding is related to some fatal diseases including Alzheimer's disease (AD). Amyloid beta-peptide (Abeta) generated from amyloid precursor protein can aggregate into amyloid fibrils, which are known to be a major component of Abeta deposits (senile plaques). The fibril formation of Abeta is typical of a nucleation-dependent process through self-recognition. Moreover, during fibrillization, several metastable intermediates such as soluble oligomers, including Abeta-derived diffusible ligands (ADDLs) and Abeta*56, are produced, which are thought to be the most toxic species to neuronal cells. Therefore, construction of molecules that decrease the Abeta aggregates, including soluble oligomers, protofibrils, and amyloid fibrils, might further our understanding of the mechanism(s) behind fibril formation and enable targeted drug discovery against AD. To this aim, various peptides and peptide derivatives have been constructed using the "Abeta binding element" based on the structural models of Abeta amyloid fibrils and the mechanisms of self-assembly. The central hydrophobic amino acid sequence, LVFF, of Abeta is a key sequence to self-assemble into amyloid fibrils. By combination of this core sequence with a hydrophobic or hydrophilic moiety, such as cholic acid or aminoethoxy ethoxy acetic acid units, respectively, good inhibitors of Abeta aggregation can be designed and synthesized. A peptide, LF, consisting of the sequence Ac-KQKLLLFLEE-NH 2, was designed based on the core sequence of Abeta but with a simplified amino acid sequence. The LF peptide can form amyloid-like fibrils that efficiently coassemble with mature Abeta1-42 fibrils. The LF peptide was also observed to immediately transform the soluble oligomers of Abeta1-42, which are thought to pose toxicity in AD, into amyloid-like fibrils. On the other hand, two Abeta-like beta-strands with a parallel orientation were embedded in green fluorescent protein (GFP), comprised of a beta-barrel structure, to make pseudo-Abeta beta-sheets on its surface. The GFP variant P13H binds to Abeta1-42 and inhibits Abeta1-42 oligomerization effectively in a substoichiometric condition. Thus, molecules capable of binding to Abeta can be designed based on structural similarities with the Abeta molecule. The peptide and protein mimetics based on the structural features of Abeta might lead to the development of drug candidates against AD.     

Oil film behavior under minute vibrating conditions in EHL point contacts

The oil film thickness was measured under conditions of minute vibrations using an elastohydrodynamic lubrication (EHL) ball-on-disk test rig. Poly-alpha-olefin (PAO) oil was used as the lubricant under conditions of pure sliding where only the ball specimen was minutely vibrated. It was found that an oil film formed when the amplitude ratio was greater than 1.6. Moreover, when conditions were changed to the maximum vibrating speed, oil viscosity, and maximum contact pressure, the critical amplitude ratio at which the oil film began to form remained at 1.6. Consequently, calculated results showed that the oil film was formed when the amplitude ratio was π/2 (nearly equal to 1.6), which closely agreed with our test results.     

Effect of axial reflector on radial uniformity in neutron transmutation doping of silicon

Significant axial variation of radial uniformity is observed in Si-ingot neutron transmutation doping in the flux screening method, and leads to non-uniform resistivity distribution for a certain part of Si-ingot. This axial variation of radial uniformity is caused by the installation of a partial neutron screen which decreases the reaction rates differently in the center and surface at the region not surrounded by the partial neutron screen. For the improvement of the specific distribution of radial uniformity in the axial direction, a new concept of axial reflector is introduced to partly change the reaction rate at a certain region of Si-ingot, and neutron irradiation experiments are carried out at the heavy water neutron irradiation facility in the Kyoto University Research Reactor. Based on the experimental and numerical results, the new axial reflector is proved to be effective for improving the axial variation of radial uniformity.     

Cloning and characterization of a β-N-acetylglucosaminidase (BmFDL) from silkworm Bombyx mori

In insects, β-N-acetylglucosaminidase (GlcNAcase) participates in critical physiological processes such as fertilization, metamorphosis, and glycoconjugate degradation. Insects produce glycoproteins carrying paucimannosidic-type N-glycans, the terminal GlcNAc residue of which is cleaved by a GlcNAc-linkage specific GlcNAcase, also known as the fused lobes (FDL) protein. To obtain information on the structure of GlcNAcases and insight into their contribution to physiological processes, we cloned Bombyx mori FDL (BmFDL) from silkworm larvae. The full-length cDNA (1.9 kb) encoded a protein of 633 amino acids with 42% amino acid sequence identity to Drosophila melanogaster FDL (DmFDL). Recombinant BmFDL cleaved only β-1,2-linked GlcNAc residues from the α-1,3 branch of biantennary N-glycan. This substrate specificity was similar to that of DmFDL. Microsomal FDL activity was inhibited by anti-BmFDL antibodies. Taken together, our results suggest that BmFDL is a N-glycan-processing GlcNAcase in B. mori.     

A Novel Approach to the Polaronic Metallic State of Cuprate Superconductors and the d-Wave Pairing Mechanism

The present novel approach consists of two stages: in the first stage the many-electron states of a CuO₆ octahedron or a CuO₅ pyramid are calculated by the first-principles variational method, by taking into account the local distortions of a CuO₆ octahedron or a CuO₅ pyramid. In the second stage a metallic state is constructed in the presence of the local AF ordering constructed by the localized spins. In this metallic state the local distortions are treated in the mean field approximation, so that a pseudopolaronic effect is taken into account. Based on this approach, the hole-concentration dependence of T _c and the isotope effect are calculated for LSCO, and compared with experimental results. This approach leads to d-wave pairing mechanism.     

Uniform carbon‐nanotube emitter for field‐emission displays

Abstract— The synthesis of carbon‐nanotube (CNT) field emitters for FEDs by thermal chemical vapor deposition (CVD) and their structural and emission characterization are described. Multi‐walled nanotubes (MWNTs) were grown on patterned metal‐base electrodes by thermal CVD, and the grown CNTs formed a network structured layer covering the surfaces of the metal electrode uniformly, which realized uniform distribution of electron emission. A technique for growing narrow MWNTs was also developed in order to reduce the driving voltage. The diameter of MWNT depends on the growth temperature, and it has changed from 40 nm at the low temperature (675°C) to 10–15 nm at the high temperature (900–1000°C). Moreover, narrower MWNTs were grown by using the metal‐base electrode covered with a thin alumina layer and a metal catalyst layer. Double‐walled nanotubes (DWNTs) were also observed among narrow MWNTs. The emission from the narrow CNTs showed a low turn‐on electric field of 1.5 V/μm at the as‐grown layer.     

Application of a novel polypropylene to the insulation of an electric power cable

Cross‐linked polyethylene (XLPE) has been widely adopted as insulating material for high‐voltage power cables up to 500 kV. Further improvement of electrical and thermal properties on insulating material is required in order to increase cable operation efficiency. Therefore, the development of novel insulating material possessing high thermal properties will be necessary. Recent progress of catalysis technology contributes to obtain new polymeric materials which may be applied to electrical insulation. The authors investigated the basic properties of newly developed stereoregular syndiotactic polypropylene (s‐PP) which is synthesized with homogeneous metallocene catalyst. Though recycling of cross‐linked polymers such as conventionally used XLPE may be difficult because of their poor heat deformation, the s‐PP which is not cross‐linked must be suitable for recycling. A series of experiments on its physical and electrical properties gave the following results.

• (1) s‐PP has sufficient flexibility compared with isotactic polypropylene (i‐PP ).
• (2) Both AC and lightning impulse breakdown strength of s‐PP in spite of no cross‐linking are superior to those of XLPE in the temperature range from 25 to 90 °C.
• (3) Degradation by copper of s‐PP is less than that of i‐PP.
• (4) s‐PP/VLDPE blend shows sufficient brittleness temperature for use.

These results suggested that s‐PP should serve as insulating material for power cables at higher‐temperature operation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 18–26, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002//eej.10210