High-field dielectric properties of polypropylene films in high-temperature region

Nonpolar polymers are used widely as electrical insulation materials, and their operating conditions sometimes become high-electric field and high temperature. Under these conditions, the conduction loss is assumed to affect the dielectric properties and to make the ac dissipation factor (tan δ) increase. Therefore the high-field dielectric properties of polymeric materials in the high-temperature region become very important. This paper describes the high-field dielectric properties of polypropylene films measured at 50 and 400 Hz above room temperature with the new electrodes developed by authors. At low temperature, the high-field tan δ is independent of the frequency of the applied field. However, at high-temperature, the high-field tan δ becomes almost inversely proportional to the frequency, namely, the conductivity is independent of the frequency. The theoretical analysis shows that the high-field dielectric loss is governed by two processes: one is the loss which appears only under ac field; and the other is conduction loss which appears also under dc field. The latter loss becomes prominent under high-electric field at high temperature.     

Control strategies in pattern analysis

A survey is made on the control strategies in pattern analysis. Discussions are made on the problems of (1) combinatorial and sequential methods, (2) bottom-up and top-down processes, (3) feedback processes, (4) procedural and declarative methods, (5) use of knowledge, and (6) recursive analysis processes. Merits and demerits are pointed out contrastively in and among these methods, with the author's personal research results. The importance of the declarative method in pattern analysis, especially in the patterns of complex objects, is stressed. The importance of the feedback and recursive applications of analysis algorithms is also mentioned to obtain the accurate results.     

Enzymatic conversion of steryl esters to free sterols

Conversion of oleic acid phytosteryl esters (OASE) to free phytosterols (referred to as sterols) by an enzymatic process was attempted. Enzymatic hydrolysis of OASE reached a steady state at 55–60% hydrolysis, but addition of methanol (MeOH) significantly accelerated the conversion of OASE to sterols. Screening of commercially available enzymes indicated that Pseudomonas aeruginosa lipase was most effective for the conversion. Based on the study of several factors affecting the reaction, the optimal conditions were determined as follows: ratio of OASE to MeOH, 1∶2 (mol/mol); water content, 10 wt%; lipase amount, 20 U/g by weight of reaction mixture; temperature, 30°C. When the reaction was conducted for 48 h with stirring, the conversion reached 98%. FAME accumulated in the reaction mixture, but FFA did not, indicating that the FAME was poorly recognized as a substrate in the reverse conversion of sterols to OASE but the FFA was easily recognized as a substrate. The high conversion of OASE to sterols was therefore due to elimination of FFA from the reaction system. After the enzymatic reaction, the oil layer was fractionated at −20°C with 5 vol parts of n-hexane. Sterols were efficiently purified in the resulting precipitate (92% recovery, 99% purity).     

Development of the arbitrarily primed-representational difference analysis method and chromosomal mapping of isolated high throughput rat genetic markers

Linkage mapping of quantitative trait loci requires analysis of a large number of animals. Although genetic markers isolated by representational difference analysis (RDA) and its modifications meet the needs, the number of these markers has been limited. In the present study, we established the arbitrarily primed (AP)-RDA method to isolate virtually an unlimited number of the high throughput genetic markers. A representation of the genome, an AP-amplicon, was prepared by AP-PCR with a single primer or with a combination of primers using genomic DNA of the ACI/N (ACI) or BUF/Nac (BUF) rat as a template. By subtracting the AP-amplicon of ACI from that of BUF, a total of 40 polymorphic and independent markers were isolated in seven series of AP-RDA using a single primer. Two series of AP-RDA with primer combination yielded seven additional independent markers. All of the markers gave clear positive/negative signals by hybridization of a filter where AP-amplicons from F2 rats of ACI and BUF were dot-blotted at a high density without any concentration or purification. All of the 47 independent markers were mapped to unique chromosomal positions by linkage analysis, even though some arbitrary primers had very similar sequences. The markers were also informative between other strains of rats. Simultaneous hybridization of multiple filters made it possible to genotype a large number of rats simultaneously for multiple genetic loci. The AP-RDA method promises isolation of a large number of high throughput genetic markers in any species and is expected to facilitate linkage mapping of subtle quantitative trait loci.     

Synthesis of perovskite-type (La1−x Ca x )CoO3 at low temperature using ethylene glycol and citric acid

To synthesize perovskite-type (La_1−x Ca _x )CoO₃ with good crystallinity (regularity of ions), a gel was prepared by adding ethylene glycol and citric acid to an aqueous solution of La(NO₃)₃ · 6H₂O, CaCO₃, and Co(CH₃COO)₂ · 4H₂O. Perovskite-type (La_1−x Ca _x )CoO₃ (0.0 ≤ x ≤ 0.3) was obtained by firing the gel above 600 °C in air for 3 h. Samples were examined for oxygen content, crystallite size, specific surface area, and the catalytic activity of CH₄ oxidation. The samples were also investigated by transmission electron microscopy (TEM). Based on the variation in crystallite size and in the average particle size, the (La_1−x Ca _x )CoO₃ particle became finer as x increased. In all samples, CH₄ oxidation occurred above 300°C. The catalytic activity of (La_1−x Ca _x )CoO₃ fired at 700 °C monotonously increased as x increased.     

Multilevel-type multilayer X-ray lens (Fresnel zone plate) by sputter deposition

We have developed a multilevel-type multilayer X-ray lens (Fresnel zone plate, FZP) using sputter deposition. Such a multilevel-type FZP can attain high diffraction efficiency which results in the reduction of radiation damage to biological specimens and the simplification of the X-ray optical system because unwanted diffraction orders are considerably suppressed. Previously, we have reported the effectiveness (i.e., realizing high diffraction efficiency) of a multilevel multilayer FZP with 4-step structure. This paper presents two experimental results on the FZP: (1) the focusing test of a multilayer FZP with 6-step structure in order to realize higher efficiency and (2) the change over time of the focusing characteristic of the FZP with 4-step structure. For (1), the diffraction efficiency of the 1st order focus and the focused beam size measured by knife-edge scanning were found to be more than 50% and 0.8 μm, respectively, at 41.3 keV, and superior to the previous results. For (2), no significant differences have been observed: it can be said that the multilevel FZP is stable at least for 9 months.     

Longitudinal-mode characteristics of weakly index-guidedburied-stripe type 980-nm laser diodes with and withoutsubstrate-mode-induced phenomena

We have carried out a systematic experimental study of the longitudinal-mode characteristics of 980-nm laser diodes with a weakly index-guided buried-stripe structure at high optical output powers. For comparison, we have prepared devices with 1.5- and 2.5-μm cladding layers. We found large differences in the longitudinal-mode characteristics and light output linearity between the two types of devices. We think that these differences result from whether or not there is coupling between the ordinary laser-mode and an unusual substrate-mode. In addition, our results show an improvement in laser diode characteristics when the substrate-mode is suppressed     

Pharmacological profiles of a novel oral antidiabetic agent, JTT-501, an isoxazolidinedione derivative

JTT-501, 4-[4-[2-(5-methyl-2-phenyl-4-oxazolyl)ethoxy]benzyl]-3,5-isoxaz olidinedione, is an isoxazolidinedione derivative which is structurally distinct from thiazolidinediones such as pioglitazone and troglitazone. We investigated the effects of JTT-501 on insulin-sensitizing activity and in rodent diabetic models. JTT-501 enhanced insulin-stimulated cell differentiation of 3T3-L1 fibroblasts with an EC50 value of 110 nM. Furthermore, JTT-501 activated peroxisome proliferator-activated (PPA) gamma and alpha receptors with the EC5-fold values of 0.28 and 5.4 microM, respectively. In the non-insulin-dependent diabetes mellitus model KK-Ay mice, JTT-501 improved hyperglycemia, hyperinsulinemia and hypertriglyceridemia, and enhanced insulin-stimulated glucose oxidation in adipose tissues. JTT-501 was also effective in the non-insulin-dependent diabetes mellitus model Zucker diabetic fatty (ZDF) rats but not in the insulin-dependent diabetes mellitus model streptozotocin-induced diabetic mice. These observations suggest that JTT-501 enhances insulin sensitivity in peripheral tissues and improves hyperglycemia, hyperinsulinemia, and hypertriglyceridemia in non-insulin dependent diabetes mellitus models. In particular, the triglyceride-lowering activity of JTT-501 is a unique characteristic compared to the thiazolidinediones. Therefore, JTT-501 may be a promising antidiabetic agent for treating non-insulin-dependent diabetes mellitus patients with insulin resistance.     

Observation of kinoform-style multilayer Fresnel zone plate by scanning ion microscopy

We investigated a kinoform-style Fresnel zone plate (FZP) that is a high-efficient optical element for hard X-ray focusing. The Cu/Al kinoform-style FZPs were fabricated with a sputtered-sliced method. The FZP was composed of 450 layers (30 layers, 15 pairs) of Al, Cu/Al composite, and Cu. The microstructure of the Cu/Al composite layer was observed by scanning ion microscopy based on a focused ion beam (FIB). In the Cu/Al composite layer, the SIM images obtained by grain orientation contrast observation indicated that the Cu grains were grown gradually with increasing Cu concentration.     

Proton conductivity of biopolymer–platinum nanoparticle composite under high humidity

A κ-carrageenan–Pt nanoparticle composite (Cg–Pt) was synthesized and its proton conductivity was examined by a complex-plane impedance method. The synthesized Cg–Pt was characterized by transmission electron microscope (TEM) observation, powder X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) absorption measurements, and thermogravimetry/mass spectrometry (TG/MS) analysis. It was revealed that the a.c. electrical conductivity of Cg–Pt strongly depends on relative humidity (RH) and exceeds the conductivity of Cg under conditions of high humidity. From the temperature dependence of the a.c. conductivity, activation energies for protonic conduction were estimated to be 0.47 and 0.34 eV for Cg–Pt and Cg, respectively. The origin of the differences in the conductivities and activation energies are discussed.