Crystal Structures of Two Orthorhombic Zirconias

The crystal structures of orthorhombic zirconias formed by cooling magnesia-partially-stabilized zirconia (Mg-PSZ) (space group Pbc 2₁) and by quenching zirconia powder from 600°C and 6 GPa (space group Pbca ) are compared and contrasted. It is demonstrated that the two structures are easily distinguished by the neutron powder diffraction techniques used to establish them. The occurrence of two distinct phases is hence proved. Structural relationships between these two phases and also with the in situ high-pressure structure proposed from X-ray diffraction (XRD) are discussed. The three structures are virtually indistinguishable by XRD and so the structure of the high-pressure form "in situ" is considered to remain unknown.     

Premixed flame propagating into a narrow channel at a high speed, part 2: Transient behavior of the properties of the flowing gas inside the channel

The behavior of a premixed flame propagating from a chamber into a narrow channel at a high speed was examined using high speed and instantaneous schlieren photography, ion current measurement with electrostatic probes, and temperature measurement with an optical method. From detailed measurements of flames passing through the channel, flame extinguishment in the channel, no matter whether transient or not, was found to occur due to quenching of the reacting gas by rapid turbulent mixing with cold fresh mixture at the downstream of the contraction region and by heat transfer to the cold channel walls. Extinguishment must occur when these heat losses exceed the heat released by the chemical reaction of the flowing mixture.     

Analysis of Software Test Item Generation—Comparison Between High Skilled and Low Skilled Engineers

Recent software system contain many functions to provide various services. According to this tendency, it is difficult to ensure software quality and to eliminate crucial faults by conventional software testing methods. So taking the effect of test engineer's skill on test item generation into consideration, we propose a new test item generation method, which supports the generation of test items for illegal behavior of the system. The proposed method can generate test items based on use-case analysis, deviation analysis for legal behavior, and faults tree analysis for system fault situations. Prom the results of the experimental applications of our method, we confirmed that test items for illegal behavior of a system were effectively generated, and also the proposed method could effectively assist test item generation by an engineer with low-level skill.     

Characterization of the diacylglycerol acyltransferase activity in the membrane fraction from a fungus

In an attempt to clarify the mechanism of lipid accumulation inMortierella ramanniana var.angulispora, diacylglycerol acyltransferase (DGAT) in the membrane fraction from this fungus was characterized. The enzyme had an optimum pH of 7.0–7.5, and enzyme activity was blocked by SH-reagents. Metal ions were not essential for maintaining DGAT activity.n-Octyl-β-d-glucoside, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate and Tween 80 were found to preserve activity, while Triton X-100 and sucrose monolaurate inhibited it. As the inhibition of DGAT activity by Triton X-100 was overcome by the addition of diacylglycerol (DG), the dependency of DGAT activity on exogenous DG was determined in the presence of 0.1% Triton X-100. DGAT activity in the membrane fraction was traced in fungi cultured for different time periods or in media at different carbon to nitrogen (C/N) ratios. Although the increase in total lipid content with culture time was accompanied by an increase in DGAT activity, total lipid changes related to changes in C/N ratio did not correlate with DGAT activity. Factors other than DGAT activity in the membrane fraction would appear to be involved in the regulation of total lipid content in this fungus.     

Effect of Interlayer Thickness on Residual Thermal Stresses in a Ceramic-to-Metal Cylindrical Joint

It is well-known that large thermal stresses are caused in a ceramic-to-metal joint by thermal expansion mismatch. Barton's analysis for stresses in cylindrical rods (M. V. Bartoh, J. Appl. Mech. , 8, A97 (1941)) was reformulated in terms of stresses arising from thermal expansion mismatches in elastically homogeneous cylindrical joints, and qualitative agreement was shown between these results and those produced by finite element calculations. Here, we apply these results to homogeneous joints with interlayers having different thermal expansion coefficients, to examine the effect of interlayer thickness on diminishing thermal expansion mismatch stress.     

Induced bone by calcium ohosphate (Ca-P) ceramics after 2-years implantation

The changes of induced bone with four kinds of Ca-P ceramics after 2 years implantation in the dorsal muscles of rabbits were investigated. After 2 years implantation, mature bone (with a lamellar structure after the remodeling process) with bone marrow was observed in HA1100 (HA, micro+macro porous), HA900 (HA, micro+macro porous) and BCP (HA/TCP=7:3, micro+ macro porous), and no bone formation was observed in HA1200 (HA, macro porous) ceramics. The induced bone neither disappeared nor grew uncontrollably, and was seen inside the pores of the implants or on the outer surface under the fibrous layer after 2 years. No bone formation was observed in the soft tissues distant from the implants. These results indicate that heterotopic bone formation induced by Ca-P materials did not give rise to uncontrolled growth over time, and the induced bone is limited to the inside or around the implants. Moreover, ectopic bone formation on the outer surface of the implants was detected in rabbits after 2 years.     

Metastable Modification of Y2CeO5

A metastable modification of Y₂GeO₅ is formed from an amorphous material prepared by the simultaneous hydrolysis of yttrium and germanium alkoxides. It has an orthorhombic unit cell with a =0.6068 nm, b =1.0695 nm, and c = 1.1994 nm. The chemical structure is described by the formula Y₄(Ge₂O₆)O₄.     

Living cationic polymerization of vinyl ethers with a functional group

Summary Living polymerizations of 2-vinyloxyethyl methacrylate and 2-vinyloxyethyl cinnamate were successfully performed with a mixture of hydrogen iodide and iodine (HI/I₂) as an initiating system in toluene at –15 to –40 °C, Although the two monomers have an unsaturated ester pendant group, their living polymerizations proceeded exclusively via the vinyloxyl group without undesirable side reactions of the pendant group. The product polymers had a very narrow molecular weight distribution (Mw/Mn 1.1), and {Mn} directly proportional to monomer conversion. For both vinyloxyethyl monomers, the addition of a new feed of monomer to a polymerization mixture led to an increase in polymer molecular weight which was again proportional to the conversion.     

Cloning and expression analysis of two catalase genes from Aspergillus oryzae

Fungi contain distinct genes encoding the same class of enzyme that are differentially regulated according to conditions. We cloned two catalase genes, catA and catB, from Aspergillus oryzae. The catA gene predicts a 747-amino-acid polypeptide sharing 81% identity with Aspergillus fumigatus catalase (catA) and 77% with Aspergillus nidulans catalase (catA). The catB gene predicts a 725-amino-acid polypeptide sharing 82% identity with A. fumigatus catalase (catB) and 75% with A. nidulans catalase (catB). However, the catA and catB genes share little homology (41%) with one another, suggesting that each gene belongs to a distinct gene family. Overexpression studies demonstrated that both genes encode a functional catalase. Promoter assays indicated that the catA gene is developmentally regulated as it was preferentially expressed in solid-state cultures undergoing sporulation. However, its expression was not affected by hydrogen peroxide treatment. Conversely, the catB gene was highly expressed under all culture conditions tested, and it was induced by hydrogen peroxide treatment. These results suggest that the catB gene may be mainly used for detoxification of oxidative stress while the catA gene may have another role such as chaperoning proteins in the spore.     

Reliable indirect competitive ELISA used for a survey of ochratoxin A in green coffee from the North of Paraná State, Brazil.

The performance of an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) based on a monoclonal antibody (mAb) for ochratoxin A (OTA) detection was evaluated in a comparative study with high-performance liquid chromatography (HPLC) analysis using 68 freshly harvested coffee samples from the North of Paraná State, Brazil. The anti-OTA mAb showed high specificity and low cross-reactivity with OTA analogues (OTB and OTalpha), but cross-reacted with OTC. This ic-ELISA showed a detection limit of 3.75 ngg-1 sample, when compared to 0.80 ngg-1 by HPLC, with an ic-ELISA/HPLC correlation coefficient of 0.90. As regards OTA analysis of these coffee samples, natural contamination was detected in 10 samples (14.7%) by both methods, where the ic-ELISA values (range 3.9-7.3 ngg-1) were 1.1 to 1.6-fold higher than HPLC data (2.7-4.7 ngg-1). Five samples (7.4%) were OTA positive (range 0.84-1.30 ngg-1) only by HPLC assay, probably due to the higher detection limit reached by ic-ELISA. OTA was undetectable in 53 samples (77.9%) by both methods, while all positive samples (range 0.84-7.30 ngg-1) showed OTA levels lower than 8 ngg-1 (maximum limit recommended by the European Union). The matrix interference of green coffee was minimized by dilution of sample extracts before carrying out the ELISA assay. This mAb-based ic-ELISA can be effectively applied for OTA screening in coffee, because it is simple, sensitive and sample preparation is easy.