Possible Existence of Dense Ferrimagnetic Perovskite Allotropic Form of Yttrium Iron Garnet

Mixed oxides with the same chemical composition as yttrium iron garnet (YIG) were maintained at 900°C and 20 kbars for 30 min. X-ray diffraction showed that the product was single-phase. Since the diffraction pattern could be indexed as a structure similar to yttrium ortho-ferrite, YFeO₃, the product was considered to be a deformed type of perovskite. Subsequently, the lattice constants were calculated to be a = 5.27, b = 5.57, and c = 7.59 A. Both measured and calculated densities were about 6% greater than those of YIG. This material, therefore, can be called a dense allotropic form of YIG. Ferrimagnetism was observed in this phase; the Curie temperature and the magnetic moment at room temperature were estimated to be 625° C and 63 emu/g, respectively. This dense form converted to YIG on heating at 900° C for 4 hr in air. The transformation of YIG to a dense form at high pressures is inconsistent with the results reported by Marezio et al. Some possible reasons for this discrepancy are discussed.     

表面粗糙度引起的超声波厚度测量误差的修正方法

根据对未经平整的粗糙锈蚀表面分别进行超声波厚度测量和机械测量的比较试验，发现超声波测量的平均误差为0．6～2．2mm。为解决该问题，建议使用一种表面回波持续时间的误差修正法，并选用合适的2．25MHz宽带换能器进行测量。该方法也适用于喷漆的表面检查。     

Transformation of Yttria-Doped Tetragonal ZrO2 Polycrystals by Annealing in Water

Phase changes and the microstructure resulting from low-temperature annealing of yttria-doped tetragonal ZrO₂ polycrystals in water were investigated at 65° to 120°C. Tetragonal ZrO₂ on the surface of the sintered body transformed to the monoclinic phase, accompanied by microcracking. The transformation rate in water, which was much greater than that in air, was first order with respect to surface concentration of tetragonal ZrO₂. Nonaqueous solvents with a molecular structure containing a lone-pair electron orbital opposite a proton donor site also greatly enhanced the transformation.     

Lipid Changes in Sea Urchin Gonads during Storage

In lipids of salted sea urchin gonads, the changes in contents of neutral lipids (NL), glycolipids (GL) and phospholipids (PL), in peroxide and carbonyl values, in lipid class compositions of NL and PL, and in fatty acid composition were investigated as a function of storage time. NL increased while GL and PL decreased by autolysis during 180 days storage. The increase of NL resulted from free fatty acids (FFA) [plus fatty acid ethyl esters (FAEE)] generated enzymatically by hydrolysis of PL and GL. Triglycerides were stable throughout a period of storage. In heat-treated and salted gonads, NL, GL and PL remained nearly unchanged during storage, and FFA and FAEE could not be detected. The oxidation of lipids was not detected during 180 days storage, although salted gonads had high content of polyunsaturated fatty acids.     

ORAL PERCEPTION OF GRITTINESS: EFFECT OF PARTICLE SIZE AND CONCENTRATION OF THE DISPERSED PARTICLES AND THE DISPERSION MEDIUM

The perceptibility of grittiness and the threshold value of grittiness were examined in five disperse model systems: aqueous suspensions, low and high viscous suspensions, and soft and hard gels. Fourteen types of microcrystalline cellulose were used having different particle sizes (between 6–79 μm) and physical properties (shape, degree of polymerization, and state at the material stage). In each system, the proportion of people who perceived grittiness increased with increasing particle size and decreased with increasing particle concentration demonstrating that perception of grittiness depended on both particle size and concentration. The proportion of people who perceived grittiness was found by multiple regression analysis to have a high correlation with the logarithm of (particle size × concentration). Each system gave an approximate regression equation representing this relation. The value of particle size × concentration at the grittiness threshold was defined as the point where 50% of people perceived grittiness. These values were calculated to be 6.0 (aqueous suspension). 19.7 (low viscosity), 26.7 (high viscosity suspension), 30.7 (soft), and 42.1 (hard gel). The factor contributing most to grittiness was concentration, followed by dispersion medium and particle size. The proportion of people who perceived grittiness was also expressed by a multiple regression equation which included these three factors. The obtained results suggest the possibility of predicting and controlling grittiness in foods.     

Determination of Tetrodotoxin by Capillary Isotachophoresis

A method is described for the quantification of tetrodotoxin (TTX) in crude extracts of puffer fish by capillary isotachophoresis. Conditions for isotachophoresis consisted of a leading electrolyte of 5 mM potassium acetate, pH 6.0, containing 0.2% Triton X-100 and 0.5 vol of dioxane, and a terminating electrolyte of 10 mM β-alanine adjusted to pH 4.5 with acetic acid. It was possible to quantify the TTX content of crude unfractionated puffer extracts, and obtain values similar to those obtained by mouse bioassays which are time consume.     

Proteinaceous Surfactants Produced from Gelatin by Enzymatic Modification: Evaluation for Their Functionality

Proteinaceous surfactants were prepared by applying the “one-step process” which permitted covalent incorporation of amino acid esters directly into proteins during treatment with papain. Gelatin was used as a hydrophile and n-alkyl esters of L-leucine as lipophiles. Each of the hydrophile-lipophile mixtures was incubated with papain under the following conditions: medium, 1M carbonate (pH 9) or a 20:80 mixture of acetone-1M carbonate (pH 9) containing 2 mM 2-mercaptoethanol; concentration of gelatin in the medium, 33% (w/w); L-leucine ester vs gelatin ratio, 0.1 mole/100g; papain vs gelatin, 1% (w/w); incubation period, 15 min; and temperature, 37°C. The enzymatic reaction was stopped by adding 1N HCl and the product purified by dialysis followed by washing with hot acetone or dichloromethane to remove low-molecular species. Each product was found to be a mixture of peptides having a wide range of molecular weight, with an average at approximately 7,500 daltons. The amounts of the alkyl moieties covalently incorporated were in a range 1.1–1.2 moles per 7,500g of the products. Their surfactancy varied depending particularly on the carbon number of the alkyl moiety; the products resulting from the incorporation of C₄–C₆ alkyl esters of leucine showed greater whippability, whereas the incorporation of the C₁₀–C₁₂ alkyl esters gave products having a higher ability to stabilize an o/w type emulsions.     

Properties and Structure of Lithium Borate and Strontium Borate Glasses

Experimental results for some physical properties of Li₂O-B₂O₃ and SrO-B₂O₃ glasses with high modifier content showed anomalies in the composition dependence of many properties such as thermal expansion coefficient, transformation temperature, softening temperature, density, and refractive index at 30 to 33 mol% modifier oxide in these glasses. These anomalies are attributed to the formation of nonbridging oxygens near this composition.