Thermoelectric Properties of Rare Earth-Doped SrTiO3 Nanocubes

A giant Seebeck coefficient of ?890 μV/K at 500 °C has been observed in Y_0.2Sr_0.8TiO₃ prepared using nanocubes. Doping rare earth elements, RE, has revealed that small RE is effective to enhance the Seebeck coefficient. Through soft mode observations by Raman spectroscopy and structural calculations based on density functional theory, it has been found that the breakdown of inversion symmetry of the perovskite structure near the surface of nanocubes can be recovered by doping with small RE. Because the dielectric constant is strongly related to the surface structure in this compound, we suggest that RE doping modulates the potential barrier at the grain boundary, resulting in a pronounced energy filtering effect in Y doped SrTiO₃.     

Production and characterization of active soluble human beta1,4-galactosyltransferase in Escherichia coli as a useful catalyst in synthesis of the Gal beta1-->4 GlcNAc linkage

An active and soluble human beta1,4-galactosyltransferase (beta-GT) was produced in Escherichia coli using a maltose-binding protein fusion system. The purified recombinant beta-GT has a K(m) value of 0.035 mM for UDP-galactose and a V(max) of 643 x 10(3) nmol/mg/h. The enzyme catalyzes the transfer of galactose from UDP-galactose to N-linked oligosaccharides. The properties of the purified enzyme were identical to those of bovine milk beta-GT.     

Isolation and analysis of lipase-overproducing mutants of Serratia marcescens

We have isolated a lipase-overproducing mutant, GE14, from Serratia marcescens 8000 after three rounds of N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. The mutant GE14 produced 95 kU/ml of extracellular lipase in the lipase medium, which was about threefold higher than that of produced by the original strain 8000. Enzymatic characteristics including specific activity of purified lipases from culture supernatants of GE14 and 8000 were almost same. The lipase gene (lipA) of GE14 contained two base substitutions; one in the promoter region and another in the N-terminal region of the lipA gene without an amino acid substitution. Promoter analysis using lipA-lacZ fusion plasmids revealed that these substitutions were responsible for the increase in the lipA expression level, independently. In contrast, no base substitution was found in the genes encoding the lipase secretion device, the Lip system. In addition, the genes coding for metalloprotease and the cell surface layer protein which are both secreted through the Lip system and associated with extracellular lipase production, also contained no base substitution. The strain GE14 carrying a high-copy-number lipA plasmid produced a larger amount of the extracellular lipase than the recombinant strains of 8000 and other mutants also did, indicating that GE14 was not only a lipase-overproducing strain, but also an advantageous host strain for overproducing the lipase by a recombinant DNA technique. These results suggest that the lipase-overproducing mutant GE14 and its recombinant strains are promising candidates for the industrial production of the S. marcescens lipase.     

Enhancement of oxygen reduction activity of nanoshell carbons by introducing nitrogen atoms from metal phthalocyanines

Nanoshell carbon is a type of catalytically grown nanocarbon with a hollow, round, shell-like structure, with a diameter in the range of approximately 20-50 nm. It has been shown to possess the electrocatalytic activity for oxygen reduction reaction (ORR) and is also expected to be a non-Pt catalyst for polymer electrolyte fuel cells. This paper reports the synergetic enhancement of the ORR activity of nanoshell carbons caused by the coexistence of nitrogen atoms. The nanoshell carbons were prepared by the carbonization of furan resin in the presence of acetylacetonates (AAs) and of phthalocyanines (Pcs), which contained Fe, Co, and Ni. The Pc-derived nanoshells (MP-T series; M = Co or Fe, T = carbonization temperature) showed higher ORR activities than the AA-derived nanoshells (MA-T series; M = Co or Fe, T = carbonization temperature) when the same metal elements were employed. An XPS study revealed that nitrogen species were introduced to the surface of the nanoshells when Pcs were used as the nanoshell-forming catalysts, and that no metal species remained on the nanoshells. Principally, the ORR activity of the carbons was governed by the presence of the nanoshells and further enhancement could be achieved by the introduction of nitrogen atoms. 0.78 V of OCV and 0.21 W cm⁻² of the maximum power density were observed for a fuel cell whose MEA consisted of 3CoP1000 cathode and a commercial Pt/C anode, when it was operated at 80 °C under a pressurized condition of 0.35 MPa.     

A Major Fungitoxin from Pachira aquatica and Its Accumulation in Outer Bark

A major fungitoxin in the root of Pachira aquatica (Bombacaceae) was isolated and identified as isohemigossypolone. Quantitative analysis of isohemigossypolone in different parts of P. aquatica revealed that the outer bark of the swollen trunk accumulated a large amount of the fungitoxin. The concentration of the substance was more than 1 mg/g fresh weight in the outer bark tissues. Pure isohemigossypolone showed clear antifungal activity against Pythium ultimum at a minimum dose of 10 g/disk, and it may function as a defensive chemical to protect storage tissues of P. aquatica.     

Effect of substituting cerium-rich mischmetal with lanthanum on high temperature properties of die-cast Mg–Zn–Al–Ca–RE alloys

Mg–Zn–Al–Ca–RE alloys have been found to be promising materials for substituting aluminum alloys used for automatic transmission case applications in the automobile industry. Particularly, Mg–0.5%Zn–6%Al–1%Ca–3%RE (ZAXE05613) alloy exhibits comparable creep resistance as ADC12 die-casting aluminum alloy that is currently used for automatic transmission case applications. Changing the rare earth (RE) content of the alloy from mischmetal to lanthanum gives a further improvement in the creep properties of the alloy. Lanthanum addition results in the crystallization of a large amount of acicular Al₁₁RE₃ (Al₁₁La₃) compound along the grain boundaries as well as across the grain boundaries and this effectively controls grain boundary sliding and dislocation motion in the vicinity of the grain boundaries. As a result, die-cast ZAXLa05613 alloy exhibits a higher creep resistance than that of ZAXE05613 alloy.     

The Effect of Ethanol on Disassembly of Amyloid-β1-42 Pentamer Revealed by Atomic Force Microscopy and Gel Electrophoresis

The most common type of dementia, Alzheimer’s disease, is associated with senile plaques formed by the filamentous aggregation of hydrophobic amyloid-β (Aβ) in the brains of patients. Small oligomeric assemblies also occur and drugs and chemical compounds that can interact with such assemblies have attracted much attention. However, these compounds need to be solubilized in appropriate solvents, such as ethanol, which may also destabilize their protein structures. As the impact of ethanol on oligomeric Aβ assembly is unknown, we investigated the effect of various concentrations of ethanol (0 to 7.2 M) on Aβ pentameric assemblies (Aβp) by combining blue native-PAGE (BN-PAGE) and ambient air atomic force microscopy (AFM). This approach was proven to be very convenient and reliable for the quantitative analysis of Aβ assembly. The Gaussian analysis of the height histogram obtained from the AFM images was correlated with band intensity on BN-PAGE for the quantitative estimation of Aβp. Our observations indicated up to 1.4 M (8.3%) of added ethanol can be used as a solvent/vehicle without quantitatively affecting Aβ pentamer stability. Higher concentration induced significant destabilization of Aβp and eventually resulted in the complete disassembly of Aβp.     

Fabrication of Fine YAG-Particulate-Dispersed Alumina Fiber

This paper involves novel fabrication processes for polycrystalline α-Al₂O₃-matrix composite fibers that contain nanosized yttrium aluminum garnet (YAG) particles. Dense α-Al₂O₃/YAG nanocomposite fibers with a fine and homogeneous microstructure can be successfully fabricated via a modified sol-gel process and α-Al₂O₃ seed-particle addition. YAG nanoparticles have been homogeneously dispersed within Al₂O₃-matrix grains as well as at grain boundaries. Effects of α-Al₂O₃ seed particles and YAG nanodispersions on crystallization and microstructure development of nanocomposite fibers are discussed.     

Poly-γ-glutamate-based Materials for Multiple Infection Prophylaxis Possessing Versatile Coating Performance

Poly-γ-glutamate (PGA) possesses a nylon-like backbone and polyacrylate-like carboxyl groups, and shows an extraordinary solubility in water. In this study, the effective synthesis and structural analysis of some water-insoluble PGA ion-complexes (PGAICs) using cationic surfactants, hexadecylpyridinium (HDP), dodecylpyridinium, benzalkonium and benzetonium, were examined. We demonstrated their spontaneous coating performance to the surfaces of different materials (i.e., plastics, metals, and ceramics) as potent anti-staphylococcal and anti-Candida agents. The tests against Staphylococcus aureus revealed that, regardless of a variety of materials, PGAICs maintained surface antimicrobial activity, even after the water-soaking treatment, whereas those against Candida albicans indicated that, among PGAICs, PGA/HDP complex is most useful as an anti-fungal agent because of its coating stability. Moreover, the log reduction values against Influenza A and B viruses of PGA/HDP-coated surfaces were estimated to be 5.4 and 3.2, respectively, suggesting that it can be dramatically suppressed the infection of influenza. This is to our knowledge the first observation of PGA-based antiviral coatings.