Strain rate dependency on stress–strain relations of polypropylene

True constant strain rate tensile tests of polypropylene up to 2% initial strain were performed to investigate the strain rate dependency of the initial stress–strain gradient dσ/dε with the aid of “slack grip.” The experimental results fairly agree with even the simplest mechanical model analysis with three parameters, showing the conspicuous strain rate dependency on the initial stress–strain gradient dσ/dε. The limiting cases corresponding to zero strain rate and strain rate of infinite magnitude, both predicted by the analysis, were experimentally verified.     

Basic investigation for life assessment technology of modified 9Cr–1Mo steel

In order to develop life assessment techniques for aged components made of modified 9Cr–1Mo steel, specimens were artificially deteriorated by aging, creep and fatigue tests at elevated temperatures, and associated changes in the microstructure and mechanical properties were examined. It was observed that aging resulted in formation of Laves phase causing a decrease in toughness. The creep damage in base metal could be correlated with decrease in hardness, while creep damage in weldments could be correlated with the area fraction and density of creep voids. Creep rupture in weldments occurred in the fine-grained heat affected zone by the formation and growth of creep voids. The fatigue damage in base metal correlated to the maximum length of a crack among micro-cracks initiated during fatigue cycles.     

Thermodynamic evaluation of the phase equilibria and glass-forming ability of the Fe–Si–B system

A thermodynamic study has been carried out on the Fe–Si–B ternary system, which is important in the development of transformer core materials and Ni-based filler metals. A regular solution approximation based on the sublattice model was adopted to describe the Gibbs energy for the individual phases in the binary and ternary systems. Thermodynamic parameters for each phase were evaluated by combining the experimental results from differential scanning calorimetry with literature data. The evaluated parameters enabled us to obtain reproducible calculations of the isothermal and vertical section diagrams. Furthermore, the glass-forming ability of this ternary alloy was evaluated by introducing thermodynamic quantities obtained from the phase diagram calculations into Davies–Uhlmann kinetic formulations. In this evaluation, the time–temperature-transformation (TTT) curves were obtained, which are a measure of the time required to transform to the minimum detectable mass of crystal as a function of temperature. The critical cooling rates calculated on the basis of the TTT curves enabled us to evaluate the glass-forming ability of this ternary alloy. The results show good agreement with the experimental data in the compositional amorphization range.     

Transmission electron microscope observation of organic–inorganic hybrid thin active layers of light-emitting diodes

Low-resistivity indium tin oxide [ITO] film was successfully deposited on oxygen plasma-treated polyethylene terephthalate [PET] surfaces at room temperature. X-ray diffraction [XRD] measurements demonstrated that the film deposited on the PET surface that had not been treated with oxygen plasma had an amorphous structure. In contrast, after the low-power oxygen plasma treatment of the PET surface, the ITO film deposited on the PET surface had a poly-crystalline structure due to interactions between electric dipoles on the PET surface and electric dipoles in the ITO film. The minimum resistivity of the poly-crystalline ITO was about 3.6 times lower than that of the amorphous ITO film. In addition, we found that the resistivity of ITO film is proportional to the intensity of the (400) line in the film's XRD spectra.     

Application of a novel technique for band sawing using a tip-inserted saw regarding surface profiles

One way of achieving a successful forest management leading to biodiversity conservation is to ensure that wood is processed in an efficient manner. The authors succeeded in developing a new technology for bandsawing using a tip-inserted saw. The material used for the tipped edge was High Speed Steel (HSS) of designation SHK 51 according to the Japan Industrial Standard (JIS). The efficiency of the tip-inserted saw was investigated considering its effectiveness in controlling tooth marks and washboarding patterns that sometimes occur during bandsawing. The surface profile of the workpiece generated after sawing with 700 mm and 1100 mm diameter bandmills of the laboratory and industrial type respectively were determined using a CCD laser displacement sensor of scanning length 250 mm and scanning speed of 3 mm/sec at a sampling rate of 50 Hz. Under a setup wheel rotation speed of 200 rpm and feed speed of 1 m/min, washboardings were induced during sawing with the tip-inserted saw of uniform pitch. Thereafter, a tip-inserted saw of random pitch was constructed without removing the saw from the pulley and cutting tests were performed under the same cutting conditions when washboardings were induced during sawing with the uniform pitch tipped-inserted saw. It was observed that the washboarding pattern disappeared completely. Thus the tip-inserted saw of random pitch was very effective in controlling the washboarding pattern. Comparisons of the surface profiles of the workpiece generated by sawing with uniform pitch tip-inserted and stellite-tipped saws under both laboratory and industrial conditions indicate that regardless of the type of bandmill used, the surface profile measured with the laser displacement sensor was smoother for tip-inserted saws than stellite-tipped saws.     

Local changes in blood flow within the preovulatory follicle wall and early corpus luteum in cows

Haemodynamic changes are involved in the cyclic remodelling of ovarian tissue that occurs during final follicular growth, ovulation and new corpus luteum development. The aim of this study was to characterize the real-time changes in the blood flow within the follicle wall associated with the LH surge, ovulation and corpus luteum development in cows. Normally cyclic cows with a spontaneous ovulation (n = 5) or a GnRH-induced ovulation (n = 5) were examined by transrectal colour and pulsed Doppler ultrasonography to determine the area and the time-averaged maximum velocity (TAMXV) of the blood flow within the preovulatory follicle wall and the early corpus luteum. Ultrasonographic examinations began 48 h after a luteolytic injection of PGF(2alpha) analogue was given at the mid-luteal phase of the oestrous cycle. Cows with spontaneous ovulation were scanned at 6 h intervals until ovulation occurred. Cows with GnRH-induced ovulation were scanned just before GnRH injection (0 h), thereafter at 0.5, 1, 2, 6, 12, 24 h and at 24 h intervals up to day 5. Blood samples were collected at the same time points for oestradiol, LH and progesterone determinations. Cows with both spontaneous and GnRH-induced ovulation showed a clear increase in the plasma concentration of LH (LH surge) followed by ovulation 26-34 h later. In the colour Doppler image of the preovulatory follicle, the blood flow before the LH surge was detectable only in a small area in the base of the follicle. An acute increase in the blood flow velocity (TAMXV) was detected at 0.5 h after GnRH injection, synchronously with the initiation of the LH surge. At 12 h after the LH surge, the plasma concentrations of oestradiol decreased to basal concentrations. The TAMXV remained unchanged after the initial increase until ovulation, but decreased on day 2 (12-24 h after ovulation). In the early corpus luteum, the blood flow (area and TAMXV) gradually increased in parallel with the increase in corpus luteum volume and plasma progesterone concentration from day 2 to day 5, indicating active angiogenesis and normal luteal development. Collectively, the complex structural, secretory and functional changes that take place in the ovary before ovulation are closely associated with a local increase in the blood flow within the preovulatory follicle wall. The result of the present study provides the first visual information on vascular and blood flow changes associated with ovulation and early corpus luteum development in cows. This information may be essential for future studies involving pharmacological control of blood flow and alteration of ovarian function.     

PZT capacitor with Ir/IrO2/Ir electrode fabricated by RTA

Abstract

PZT capacitor with direct contact between Si substrate and bottom electrode of the capacitor was obtained with Ir/IrO₂/Ir/Ti electrode, by crystallizing sol-gel PZT thin film using RTA (650°CC 30 sec.). Contact resistance for hole diameter of 0.72 μm was 19 Ω. It was observed by cross-sectional TEM that Ti silicide was formed at the interface, but there was not oxygen diffusion from PZT thin film. Fatigue property of the PZT thin film was improved by RTA compared with furnace annealed film (600°CC 60 min.). The absolute value of the remnant polarization was 13 μC/cm² for both films, but it did not degrade until 10⁸ cycles of switching for the film by RTA, while it degraded before 10⁵ cycles for furnace annealed film.     

Clarification of strain limits considering the ratcheting fatigue strength of 316FR steel

The effect of ratcheting on fatigue strength was investigated in order to rationalize the strain limit as a design criterion of commercialized fast reactor systems. Ratcheting fatigue tests were conducted at 550 °C. Duration of the ratchet straining was set for a certain number of strain cycles taking the loading condition of fast reactors into account, and the number of cycles for strain accumulation was defined as the ratchet-expired cycle. Fatigue lives decrease as the accumulated strain by ratcheting increases. Mean stress increased during the ratcheting cycle and its maximum value depended on the accumulated strain and the ratchet-expired cycle. Fatigue life reduction was negligible when the maximum mean stress was less than 25 MPa, corresponding to an accumulated strain of 2.2%. Accumulated strain is limited to 2% in the present design guidelines and this strain limit is considered effective to avoid reducing fatigue life by ratcheting. Microcrack growth behaviors were also investigated in these tests in order to discuss the life reduction mechanisms in ratcheting conditions.     

Heat labile ribonuclease HI from a psychrotrophic bacterium: gene cloning, characterization and site-directed mutagenesis

The rnhA gene encoding RNase HI from a psychrotrophic bacterium,Shewanella sp. SIB1, was cloned, sequenced and overexpressedin an rnh mutant strain of Escherichia coli. SIB1 RNase HI iscomposed of 157 amino acid residues and shows 63% amino acidsequence identity to E.coli RNase HI. Upon induction, the recombinantprotein accumulated in the cells in an insoluble form. Thisprotein was solubilized and purified in the presence of 7 Murea and refolded by removing urea. Determination of the enzymaticactivity using M13 DNA–RNA hybrid as a substrate revealedthat the enzymatic properties of SIB1 RNase HI, such as divalentcation requirement, pH optimum and cleavage mode of a substrate,are similar to those of E.coli RNase HI. However, SIB1 RNaseHI was much less stable than E.coli RNase HI and the temperature(T_1/2) at which the enzyme loses half of its activity upon incubationfor 10 min was ~25°C for SIB1 RNase HI and ~60°C forE.coli RNase HI. The optimum temperature for the SIB1 RNaseHI activity was also shifted downward by 20°C compared withthat of E.coli RNase HI. Nevertheless, SIB1 RNase HI was lessactive than E.coli RNase HI even at low temperatures. The specificactivity determined at 10°C was 0.29 units/mg for SIB1 RNaseHI and 1.3 units/mg for E.coli RNase HI. Site-directed mutagenesisstudies suggest that the amino acid substitution in the middleof the     

Electrical resistivity and thermopower of (La1−xSrx)MnO3 and (La1−xSrx)CoO3 at elevated temperatures

Electrical resistivity and Seebeck (S) measurements were performed on (La_1−xSr_x)MnO₃ (0.02x0.50) and (La_1−xSr_x)CoO₃ (0x0.15) in air up to 1073 K. (La_1−xSr_x)MnO₃ (x0.35) showed a metal-to-semiconductor transition; the transition temperature almost linearly increased from 250 to 390 K with increasing Sr content. The semiconductor phase above the transition temperature showed negative values of S. (La_1−xSr_x)CoO₃ (0x0.10) showed a semiconductor-to-metal transition at 500 K. Dominant carriers were holes for the samples of x0.02 above room temperature. LaCoO₃ showed large negative values of S below ca. 400 K, indicative of the electron conduction in the semiconductor phase.