Grain Growth During Hot Isostatic Pressing of Presintered Alumina

Grain growth during hot isostatic pressing is examined at 1373 to 1673 K at 5 to 200 MPa for 0.5 to 4 h on alumina presintered at 1723 to 1873 K. A linear relation is found between logarithms of grain size and porosity. To account for this result, the development of similar microstructures is suggested regardless of the histories of the starting powder and process. Temperature dependences of grain growth and densification must also be equal during hot isostatic pressing. Both grain growth and densification were controlled by the grain-boundary diffusion of the aluminum ions.     

Retronasal Odor of Dried Bonito Stock Induces Umami Taste and Improves the Palatability of Saltiness

A traditional Japanese umami‐rich stock, dried bonito stock, was reported to improve the palatability of a low‐salt diet due to its characteristic aroma. Two pathways are available for the presentation of odors: the orthonasal and retronasal pathways. Aroma is perceived through the orthonasal pathway. In contrast, retronasal application of odors is thought to evoke different sensations from the orthonasal pathway, which is typically perceived as taste and modifies taste. Therefore, the effect of retronasal odor on salt‐reduction might be different from that of aroma, that is, orthonasal odor. Thus, the effects of the retronasal odor of dried bonito stock on the enhancement and improvement of palatability upon salt reduction were examined using sensory evaluation. Moreover, the contributions to flavor expression and palatability of dried bonito stock were also investigated. Although the retronasal odor of dried bonito did not enhance saltiness, it improved the palatability of saltiness. In the presence of no tastants except 0.68% NaCl, a content 15% less than that of Japanese traditional soup, the retronasal odor of dried bonito generated umami, enhanced the suitability for dried bonito stock, and increased palatability. This indicates that the retronasal odor of dried bonito stock could improve the palatability of a salt‐reduced diet. These findings can be applied to the development of new seasonings for improving the palatability of salt‐reduced foods.     

Production of 8,11-cis-eicosadienoic acid by a Δ5 and Δ12 desaturase-defective mutant derived from the arachidonic acid-producing fungus Mortierella alpina 1S-4

The Δ5 and Δ12 desaturase (DS)-blocked mutants of an arachidonic acid-producing fungus, Mortierella alpina 1S-4, were obtained. These mutants accumulated 8,11-cis-eicosadienoic acid (20:2n-9). One of the mutants, M226-9, in which Δ5 and Δ12 DS are perfectly blocked, produced 1.68 mg of 20:2n-9 per mL of culture medium (101 mg/g dry mycelia) and no 5,8,11-cis-eicosatrienoic acid (20:3n-9) when grown in a medium containing 4% glucose and 1% yeast extract at 28°C for 2 d and then at 12°C for 12 d. The mycelial lipid comprised 77.4% triacylglycerol (TG) and 9.8% phosphatidylcholine (PC), among others. TG contained 69.0% of the total 20:2n-9, whose percentage in total TG fatty acids was 15.9%. The highest percentage (44.4%) of 20:2n-9 was found in PC. The addition of olive oil to the culture medium enhanced the production of 20:2n-9.     

Inhibition of Calcineurin and Glycogen Synthase Kinase-3β by Ricinoleic Acid Derived from Castor Oil

Ricinoleic acid (RA) is the main fatty acid component of castor oil and was found to inhibit Ca²⁺-signal transduction pathway-mediated cell cycle regulation in a yeast-based drug screening assay. RA is expected to have antidiabetic, antiallergy, and/or anticancer properties but its target molecule is unknown. To identify a novel pharmacological effect of RA, we investigated its target molecule in the Ca²⁺-signal transduction pathway. RA inhibition of calcineurin (CN) was examined in a yeast-based CN inhibitor screening assay using the rsp5^A401E mutant and in a phosphatase assay using recombinant human CN. RA showed growth-restoration activity at 5 μg/spot in the CN inhibitor screening assay with the rsp5^A401E yeast strain. Furthermore, it directly inhibited CN without immunophilins at K_i = 33.7 μM in a substrate-competitive manner. The effects of RA on CN in mammalian cells were further evaluated by measuring β-hexosaminidase (β-HEX) release in RBL-2H3 cells. RA at 50 μM suppressed the release of β-HEX from RBL-2H3 cells. Moreover, this compound was found to inhibit glycogen synthase kinase-3β (GSK-3β), as determined by a kinase assay using recombinant human GSK-3β. RA inhibited GSK-3β at K_i = 1.43 μM in a peptide substrate-competitive manner. The inhibition of GSK-3β by this molecule was further assessed in mammalian cells by measuring the inhibition of glucose production in H4IIE rat hepatoma cells. RA at 25 μM suppressed glucose production in these cells. These findings indicate that RA and/or castor oil could be a useful functional fatty acid to treat allergy or type 2 diabetes.     

Triazolecarbaldehyde Reagents for One-Step N-Terminal Protein Modification

Site-specific modification of peptides and proteins is a key aspect of protein engineering. We developed a method for modification of the N terminus of proteins using 1H-1,2,3-triazole-4-carbaldehyde (TA4C) derivatives, which can be prepared in one step. The N-terminal specific labeling of bioactive peptides and proteins with the TA4C derivatives proceeds under mild reaction conditions in excellent conversion (angiotensin I: 92 %, ribonuclease A: 90 %). This method enables site-specific conjugation of various functional molecules such as fluorophores, biotin, and polyethylene glycol attached to the triazole ring to the N terminus. Furthermore, a functional molecule modified with a primary amine moiety can be directly converted into a TA4C derivative through a Dimroth rearrangement reaction with 1-(4-nitrophenyl)-1H-1,2,3-triazole-4-carbaldehyde. This method can be used to obtain N-terminal-modified proteins via only two steps: 1) convenient preparation of a TA4C derivative with a functional group and 2) modification of the N terminus of the protein with the TA4C derivative.     

Kinetics of property change associated with atmospheric humidity changes in alumina powder granules with PVA binder

A microcompression testing machine was used on single Al₂O₃ powder granules to study their stress–strain behavior as a function of relative humidity. The test granules were prepared by spray-drying slurries containing 3 mass% poly(vinyl alcohol) and Al₂O₃ powder. The stress–strain curves and granule strength were determined at regular time intervals, after step changes in atmospheric humidity. When stress was applied, deformation increased rapidly with the stress. This stress corresponded to the fracture strength of the granule. In a dry atmosphere, the granules deformed linearly with increasing stress, and a rapid change in strain was noted above a certain critical value of increased stress. In a wet atmosphere, the granules deformed continuously at lower stress. The mechanical properties of the granules changed rapidly with time when the atmospheric relative humidity was changed. Within 3 min of exposure to a new atmosphere, the mechanical properties of the granules reached equilibrium values. The change in properties with humidity was controlled by moisture diffusion in the granules and was reversible.     

Impedance of vapor feed direct methanol fuel cells—polarization dependence of elementary processes at the anode

Membrane electrode assemblies of direct methanol fuel cells (DMFCs) with different catalyst and ionomer loading were prepared. Anode performance and impedance spectra were measured to clarify the characteristics of vapor feed DMFCs (VF-DMFCs). The impedance spectra were deconvolved into three semi-circles with different time constants, each showing a different dependence on the anodic polarization. The middle-frequency range arc decreased as the anodic polarization increased, indicating that this process represents the oxidation reaction of methanol. The high-frequency range arc showed little dependence on the anodic polarization, but increased with the thickness of the electrode, indicating that this process might be related to proton conduction through the electrode. The low-frequency range arc was observed only when the methanol concentration was low, in contrast to liquid feed DMFCs (LF-DMFCs), for which the removal of the product gas presents a large resistance. A simpler design can therefore be used for a VF-DMFC, giving it an advantage over an LF-DMFC. A decreasing ionomer to catalyst ratio (I/C) caused the interfacial conductivity (σ_E) to increase, but it intensively decreased when I/C was below 0.25. Thus, the connection of the catalysts is important for the anode’s performance.     

Promotion Effect of Hydrogen on Grain Refinement in Pure Fe by High-Pressure Torsion-Straining

Metallurgical and Materials Transactions A - We revealed that hydrogen (H) in pure Fe promotes grain refinement during plastic deformation, which is caused by the increase in dislocation density by...