Low-Thermal-Expansion Polycrystalline Zirconyl Phosphate Ceramic: Solid-Solution and Microcracking-Related Properties

The effects of the addition of Ta205 or Nb205 on the sintering and refractory properties of 2ZrO₂·P₂O₅-based ceramics have been investigated. The solid solution with Nb₂O₅ has a lower average thermal expansion coefficient than the pure phase. The strength of the polycrystalline ceramic is reduced when the grain size exceeds the transition grain size for microcracking. The thermal expansion of the ceramic is abruptly lowered when the grain size exceeds a value which should be termed the "second transition grain size" for additional wider microcracking. SiO₂ was found most effective for inhibiting grain growth to prevent microcracking and for obtaining a strong ceramic.     

Computational complexity of spline interpolation

The procedure for composing the spline function of order m that interpolates n data is roughly divided into two stages: (1) constructing the matrix A_n that transforms the fl-spline coefficient vector c into the sample value vector s; and (2) calculating the vector c. Then the effects of boundary conditions and the locations of the sampling points and the knots on the number of computations for spline interpolation are evaluated. There are no boundary condition effects of the construction of A" for equispacing. Non-periodic boundary conditions reduce the number of computations needed to calculate c from O(m²n) to O(m²n/4).

In the construction of A_n, choosing equispaced sampling points reduces the number of computations from O(m²n) to O(m²) in the case of sampling points located at a constant interval between each pair of adjacent knots. In the calculation of c, equispaced sampling points reduce the number of computations from O(m²n) to O(m²n /2) in the case where m is even and the locations of the knots are identical with those of the sampling points.     

CARCINOGENICITY TEST OF QUERCETIN AND KAEMPFEROL IN RATS BY ORAL ADMINISTRATION

Quercetin and kaempferol were tested for carcinogenicity in rats of both sexes. In Experiment I, 0.1% quercetin or control diet was given to Fischer 344 rats for 540 days. In experiment II, 0.04% kaempferol or control diet was given to ACI rats for 540 days. In both experiments, most tumors found in the experimental groups were also found in the corresponding control groups, and there were no statistical differences in the incidences of tumors in the experimental groups and the respective control groups. Quercetin and kaempferol were not shown to be carcinogenic to rats under these conditions.     

Thermal Expansion Behavior of NaZr2(PO4)3Type Compounds

The thermal expansion of the skeletal framework was essentially zero for NaZr₂(PO₄)₃-type compounds; the interstitialion, e.g., Na⁺, was primarily responsible for the total thermal expansion. The composition dependence of the thermal expansion is discussed in terms of the amounts, crystallographic sites, and ionic radii of the interstitial ions. The mechanism which results in low thermal expansion was clarified, particularly for KZr₂(PO₄)₃, in which a larger ion is substituted for Na⁺, and NbZr(PO₄)₃, which does not contain Na⁺. Polycrystalline ceramics formed from these crystals might be useful as thermal-shock-resistant materials.     

SAFETY EXAMINATION OF SOME EDIBLE OR MEDICINAL PLANTS AND PLANT CONSTITUENTS, PART 3

The carcinogenicity of vicia, galanga, lathyrus and lycium, which are plants used as human food or in folk medicine, and of caffeic acid and prunasin, which are plant constituents, was examined in an inbred strain of ACI rats. Fresh plant materials were dried, milled and mixed with the rat basal diet in the ratio of 16% and 33% of the total. The plant constituents, caffeic acid and prunasin, were mixed with the basal diet in the ratio of 0.5% and 0.03%, respectively. These diets were administered to rats for periods ranging upward from 180 days. Carcinogenic activity was not observed with any of the plants or plant constituents.     

Low-Thermal-Expansion Polycrystalline Zirconyl Phosphate Ceramic

The synthesis of thermal-shock-resistant material from zirconyl phosphate, 2ZrO₂P₂O₅, was investigated. Modifications of the compound were examined; only the a phase appears to be thermodynamically stable. Sintering of a-phase powder to a dense ceramic was promoted by adding a metal oxide. Crystalline zirconyl phosphate has a low average thermal expansion coefficient. The relation of microcracking to grain size and strength was studied using specimens sintered under varied conditions. A strong low-thermal-expansion polycrystalline ceramic was obtained by controlling grain growth.     

Algorithm by hybrid splines

Hybrid splines whose bases are constructed by multi-order B-splines are presented. B-splines of order 2 are induced for representing corners, and those of orders 3 or 4 for representing curved parts. The hybrid splines can represent not only smooth parts (class C^m?22:m≥3) but also corners (class C°): Hybrid splines of order 2 and 4 cannot be represented by conventional splines with multiple knots. Satisfactory approximation results are obtained by hybrid splines of order 2 and 4 determined by a least-squares method.