Low temperature superplasticity of a fine-grained ZK60 magnesium alloy processed by equal-channel-angular extrusion

Fine-grained ZK60 magnesium alloy with the grain size of 1.4 μm was processed by equal-channel-angular extrusion. The material exhibited low temperature superplasticity. The normalized plot suggested that the present material had equilibrium grain boundaries at the superplastic temperature in contrast to typical materials processed by severe plastic deformation.     

High resolution X-ray photon-counting detector with scintillator-deposited charge-coupled device

We report on a new photon-counting detector possessing unprecedented spatial resolution and moderate spectral resolution for 0.1-100 keV X-rays. It consists of an X-ray charge-coupled device (CCD) and a scintillator. The scintillator is directly coupled to the back surface of the X-ray CCD. Low-energy X-rays below 10 keV can be directly detected by the CCD. The majority of hard X-rays above 10 keV pass through the CCD but can be absorbed by the scintillator, generating visible photons. We coupled needlelike CsI(Tl) on the front surface of the back-illuminated (BI) CCD. The high detection efficiency of BI CCDs in the visible band enables us to collect visible photons emitted from the CsI(Tl) efficiently, leading to the moderate spectral resolution of 28.4% at 22.1 keV and 25% at 59.5 keV. We also investigated the imaging capability of our device and demonstrated high resolution imaging with an accuracy of 10 /spl plusmn/3 /spl mu/m at 17.4 keV.     

Small polypoid lesions of the gallbladder: differential diagnosis and surgical indications by helical computed tomography

We report the case of a 16-year-old girl who experienced sudden cardiac arrest from ventricular fibrillation, complicating an arrhythmogenic right ventricular dysplasia, a rare heart muscle disorder, occurring typically in young adults, characterized by a fibrofatty replacement of the right ventricular myocardium. Symptomatic ventricular arrhythmias are frequent, and sudden death has been reported. In our case, diagnosis of arrhythmogenic dysplasia was based on the association of one major criterion and two minor criteria as suggested by the relevant task force. In contrast with most other reports, the chest ECG did not display the typical features. An automatic transvenous pectoral cardioverter-defibrillator was implanted. The authors emphasise that juvenile forms are more exposed to ventricular fibrillation and sudden cardiac death, and consequently require the early detection of the disease. Family cases have been described and the occurrence in one individual must lead to investigations in the relatives.     

S/N and error rate performance in AlGaAs semiconductor laser preamplifier and linear repeater systems

The applications of AlGaAs semiconductor laser preamplifier and linear repeaters in single mode optical fiber transmission systems were studied through the baseband signal-to-noise ratio and bit error rate performance measurement. Experiments were carried out with the Fabry-Perot cavity laser amplifiers whose characteristics are improved by reducing the input mirror reflectivity to 6 percent. The use of a preamplifier improves the minimum detectable power by 7.4 dB over the Si-APD direct detection level when the received signal is amplified by 30 dB before photodetection. The use of two linear repeaters increases the regenerative repeater gain by 37 dB. These experimental results are in good agreement with theoretical predictions based on the photon statistic master equation analysis.     

Implicit integration and consistent tangent modulus of a time‐dependent non‐unified constitutive model

This paper describes the implicit integration and consistent tangent modulus of an inelastic constitutive model with transient and steady strain rates, both of which are time‐ and temperature‐dependent; the transient rate is influenced by the evolution of back stress decomposed into parts, while the steady rate depends only on applied stress and temperature. Such a non‐unified model is useful for high‐temperature structural analysis and is practical owing to the ease in determining material constants. The implicit integration is shown to result in two scalar‐valued coupled equations, and the consistent tangent modulus is derived in a quite versatile form by introducing a set of fourth‐rank constitutive parameters into the discretized evolution rule of back stress. The constitutive model is, then, implemented in a finite element program and applied to a lead‐free solder joint analysis. It is demonstrated that the implicit integration is very accurate if the multilinear kinematic hardening model of Ohno and Wang is employed, and that the consistent tangent modulus certainly affords quadratic convergence to the Newton–Raphson iteration in solving nodal force equilibrium equations. Copyright © 2003 John Wiley & Sons, Ltd.     

Serum insulin-like growth factor-I, insulin-like growth factor binding protein-3, sex steroids, osteocalcin and bone mineral density in male and female rats

Although it has been reported that the rate of weight gain and linear growth increases markedly during puberty in rats, little is known about the relationship between endocrine changes and bone mineral density (BMD) changes upon sexual maturation in these animals. The aim of this study was to examine the levels of serum insulin-like growth factor-I (IGF-I), IGF binding protein (IGFBP)-3, sex steroids and osteocalcin, and the changes in BMD in normal aging male and female rats. Male rats exhibited increases in serum IGF-I and IGFBP-3 concentrations before increases in serum testosterone levels. IGF-I and testosterone peaked at 9 weeks of age, and thereafter remained in a steady state, whereas IGFBP-3 reached a peak at 7 weeks of age, and then gradually declined. A strong correlation between serum IGF-I and IGFBP-3 levels was found in subjects 3-9 weeks old. A highly significant correlation between serum IGF-I and testosterone levels was also found. In females, serum 17 beta-estradiol, IGF-I and IGFBP-3 levels increased gradually from 3 to 5 weeks old, peaked at 9 weeks, and then decreased slowly thereafter. The correlation coefficient between serum IGF-I and IGFBP-3 was highly significant. The correlation coefficient between serum IGF-I and 17 beta-estradiol levels was weak, although it was strongest when the subjects were 3-9 weeks old. Serum osteocalcin is a marker of bone formation; its level remained relatively high from 3 to 9 and from 3 to 7 weeks of age in males and females, respectively, although osteocalcin in both sexes declined gradually with age. As for bone mass, sharp increases in BMD in the tibia, femur and lumbar vertebrae appeared earlier in female than in male rats, and the BMD in females tended to be higher than in males between 5 and 9 weeks old. After 9 weeks of age, BMD in males was higher than that in females, as BMD in males continued to increase whereas females tended to remain in a steady state after this stage. The correlation coefficients between tibial BMD and serum IGF-I or IGFBP-3 levels were highly significant when the subjects were from 3 to 9 weeks old. Taken together, these results suggest that BMD development occurs earlier in female than in male rats. This sex-related difference in changes in the BMD pattern may result from the earlier onset of puberty in females, and from sex-specific differences in concentrations of IGF-I, IGFBP-3 and sex steroids during maturation.     

Density Measurement of Liquid Ni-Ta Alloys by a Modified Sessile Drop Method

The density of liquid Ni- Ta alloys was measured by using a modified sessile drop method. It is found that the density of the liquid Ni- Ta alloys decreases with the increasing temperature, but increases with the increase of tantalum concentration in the alloys. The molar volume of liquid Ni- Ta binary alloys increases with the increase of temperature ancl tantalum concentration.     

Improvement of hardness of MOS capacitors to electron-beamirradiation and hot-electron injection by ultradry oxidation of silicon

The sensitivity to electron-beam-induced damage and to hot-electron-induced damage of metal/SiO₂/Si capacitors has been improved by using ultradry oxide. The ultradry oxide was grown in a double-walled quartz furnace in which water concentration was reduced to less than 1 p.p.m. The interface trap generation in ultradry MOS capacitors due to electron beams is nearly one order of magnitude smaller than that in conventional dry MOS capacitors. Interface trap generation in ultradry MOS capacitors caused by hot electrons is half of that in dry MOS capacitors