Advanced resonant ultrasound spectroscopy for measuring anisotropic elastic constants of thin films

This paper presents an advanced resonant ultrasound spectroscopy (RUS) method to determine the elastic constants C_ij of thin films. Polycrystalline thin films often exhibit elastic anisotropy between the film growth direction and the in‐plane direction, and they macroscopically show five independent elastic constants. Because all of the C_ij of a deposited thin film affect the mechanical resonance frequencies of the film/substrate layer specimen, measuring resonance frequencies enables one to determine the C_ij of the film with known density, dimensions and the C_ij of the substrate. Resonance frequencies have to be measured accurately because of low sensitivity of the C_ij of films to them. We achieved this by a piezoelectric tripod. Mode identification has to be made unambiguously. We made this measuring displacement–amplitude distributions on the resonated specimen surface by laser Doppler interferometry. We applied our technique to copper thin film and diamond thin film. They show elastic anisotropy and the C_ij smaller than bulk values of C_ij. Micromechanics calculations indicate the presence of incohesive bonded regions.     

Molecular Dynamic Simulation of Eu3+ -Doped Sodium Borate Glasses and Their Fluorescence Spectra

A molecular dynamic simulation was performed for sodium borate glasses containing a small amount of Eu₂O₃ to investigate the local structures of cations in glass. A new potential V_B-B in the form -A exp[-C(r - 0.239)²] was added to the regular modified Born-Mayer-Huggins-type potentials, Φ_B-B, Φ^B-O, and ΦO-O, to account for the directional tendency of the borate network structure. With this potential added, both the radial distribution of sodium borate glasses observed by small-angle X-ray diffraction and the change in coordination number of boron with sodium content obtained by NMR agreed well with the simulation. The average coordination number of Ed³⁺ ions in the simulated glasses varied from 7.5 to 8.6, depending on the composition of the host sodium borate glasses. The inhomogeneous line width of the ⁵D₀-⁷F_z emission peak also changed, depending on the sodium content, with a maximum at 18 mol% Na_zO content; this result agrees well with experimental data obtained from laser-induced fluorescence spectra.     

Cholesterol Lowering Activity of Ropy Fermented Milk

The effect of ropy fermented milk on serum cholesterol in rats was studied. Basic diets containing slime-forming Lactococcus lactis subsp. cremoris SBT 0495, its non slime-forming variant SBT 1275, and acidified reconstituted skim milk, with 0.5% cholesterol added, were fed to F-344 rats for 7 days. Serum cholesterol level of rats fed the ropy fermented milk were the lowest among the three treatments. The serum high-density lipoprotein (HDL) cholesterol/total cholesterol ratio of rats fed ropy fermented milk was the highest. Slime materials produced by L. lactis subsp. cremoris SBT 0495 had a beneficial effect on rat cholesterol metabolism.     

Production of Hypoallergenic Rice by Enzymatic Decomposition of Constituent Proteins

A method is proposed to produce hypoallergenic rice usable for patients with rice allergy. Newly harvested rice grains were dipped in carbonate (pH 9) containing glycerin monooleate and Actinase and then the mixture was exposed to a reduced pressure for degassing. The degassed mixture was incubated at 37°C for 24 hr to hydrolyze proteins. The process produced rice grains from which the major allergenic globulin was decomposed. The product was evaluated by the radioallergosorbent test (RAST), with the result that its RAST value suggested negative allergenicity in most cases. The product was clinically administered to 7 patients with atopic dermatitis and no allergic reaction was observed in 6 of the 7.     

Dynamic Fatigue of Treated High-Silica Glass: Explanation by Crack Tip Blunting

In previous papers, it was shown that when abraded high-silica glass is soaked in hot water or annealed in air, its crack tip becomes blunt. The dynamic fatigue characteristics in various liquids of high-silica glass with different treatments were examined. The stress rate dependence of fracture strength was determined for freshly abraded samples and for abraded and soaked (in hot water) or heat-treated samples, in water, hydrazine, formamide, and acetonitrile. The stress rate susceptibility of the fracture strength was represented by the commonly used n value. Freshly abraded samples exhibited approximately the same low n values for all the liquids, which is consistent with the slope of the slow crack growth data. Treated samples, on the other hand, showed a slightly larger n value in water and extremely large n values in nonaqueous liquids. When the crack tip is sharp, only slow crack growth is involved in the fatigue. When the crack tip is blunt, crack initiation is involved in addition to the crack growth. The equation of dynamic fatigue based upon slow crack growth was modified to incorporate this effect of crack initiation and was applied to the present experimental results. The analysis showed that the crack initiation stress is stress rate dependent in water and is stress rate independent in nonaqueous liquids. This conclusion was supported by the crack initiation behavior observed using the microhardness indenter.     

Microhardness of SiO2 Glass in Various Environments

It was shown in earlier studies that the crack initiation stress of SiO₂ glass was stressing-time dependent only in water while it was time independent in nonaqueous liquids. In order to clarify the roles that various liquids play in the crack initiation of SiO₂ glass, Knoop microhardness measurements were made on SiO₂ glass in various liquids and FTIR spectroanalysis was performed on the indented SiO₂ glass. The microhardness measurements showed a similar loading-time dependence to the crack initiation stress. The microhardness was separated into two parts: the surface contribution and the volume contribution. The results showed that the volume (or bulk) component was a nearly constant value for glass measured in nonaqueous liquids and that it was lower for glass measured in water. Consistent with these results, FTIR analysis showed that water entered the glass during indentation while nonaqueous liquids did not. The surface component showed a good correlation with the crack initiation stress.     

Carp Natural Actomyosin: Thermal Denaturation Mechanism

Structural changes of actomyosin, the major protein of muscle, on heating have been estimated on ATPase activity. We investigated carp actomyosin molecule changes on heating based on biophysical and biochemical techniques. Actomyosin molecules began to unfold at ～30°C. Hydrophobic amino acid residues and SH groups, which had been inside the molecule, emerged to the surface. Because of hydrophobic interactions and disulfide bonds, actomyosin molecules formed aggregates. At > 40°C, a part of myosin molecules was dissociated from actin filaments. Thus, dissociated myosin and the myosin-lacking molecules co-existed. In addition, fragmentation of actin filaments was observed, which was associated with the dissociation of myosin molecules. At ≥ 60 °C actomyosin molecules formed larger aggregates, in which no filamentous shape was observed. This aggregation occurred mainly by formation of SS bonds.     

Kinetics of Crack Tip Blunting of Glasses

When abraded or indented glasses are annealed, a strength increase of 20% to 30% is observed. Crack tip blunting and removal of tensile residual stress near the crack tip have both been proposed to explain this phenomenon. In order to resolve which is the more likely mechanism, the kinetics of strength increase of soda-lime, borosilicate, and high-silica glasses were measured as a function of heat-treatment temperature and atmosphere. The sinusoidal profile decay of corrugated glass surfaces of the soda-lime glass was also investigated at similar temperatures and atmospheres. From these two complementary measurements, it was concluded that the observed strength increase of glasses upon annealing is caused by crack tip blunting, most likely due to viscous flow assisted by water diffused from the atmosphere.