Cryogenic optical measurements of 12-segment-bonded carbon-fiber-reinforced silicon carbide composite mirror with support mechanism

A 720 mm diameter 12-segment-bonded carbon-fiber-reinforced silicon carbide (C/SiC) composite mirror has been fabricated and tested at cryogenic temperatures. Interferometric measurements show significant cryogenic deformation of the C/SiC composite mirror, which is well reproduced by a model analysis with measured properties of the bonded segments. It is concluded that the deformation is due mostly to variation in coefficients of thermal expansion among segments. In parallel, a 4-degree-of-freedom ball-bearing support mechanism has been developed for cryogenic applications. The C/SiC composite mirror was mounted on an aluminum base plate with the support mechanism and tested again. Cryogenic deformation of the mirror attributed to thermal contraction of the aluminum base plate via the support mechanism is highly reduced by the support, confirming that the newly developed support mechanism is promising for its future application to large-aperture cooled space telescopes.     

Degradation evaluation of poly-Si TFTs by comparing normal and reverse characteristics and behavior analysis of hot-carrier degradation

We propose degradation evaluation of poly-Si TFTs by comparing normal and reverse characteristics. Since symmetrical normal and reverse characteristics indicate Joule-heating degradation whereas asymmetrical characteristics indicate hot-carrier degradation, they can be clearly and easily classified. Moreover, degradation occurrence is contrasted between standard and fine TFTs. Finally, behavior of the hot-carrier degradation is analyzed.     

Doping amount and temperature dependence of superplastic flow in tetragonal ZrO2 polycrystal doped with TiO2 and/or GeO2

The doping amount and temperature dependence of superplastic flow in a TiO₂- and/or GeO₂-doped tetragonal ZrO₂ polycrystal (TZP) were investigated in the doping range of 0.2–8 mol.% and in the temperature range of 1200–1550 °C. While the tensile ductility in the TZP is significantly improved by the co-doping of TiO₂ and GeO₂, there is an optimum combination of doping amount and temperature for enhancing the tensile ductility. The present study also shows that the flow stress decreases with an increase in the doping amount, but this decrease levels off with a 2–3 mol.% addition of GeO₂ or (TiO₂–GeO₂). The data for the flow behavior and thermal groove experiment indicated that TiO₂ and/or GeO₂ doping enhances the grain boundary diffusion of zirconium cations and reduces the grain boundary energy, respectively. These effects of grain boundary segregation can be regarded as the cause of the improved high-temperature ductility of (TiO₂–GeO₂)-doped TZP.     

Formation of needle‐like lepidocrocite fine particles by oxidation of an aqueous suspension of ferrous hydroxide in a bubble column

Fine particles of needle‐like lepidocrocite (γ‐FeOOH) were synthesized by the oxidation of aqueous suspensions of ferrous hydroxide using a bubble column with draft tube at a constant temperature ranging from 20°C to 30°C. The oxidation steps leading to green rust (an intermediate) and lepidocrocite (final product), termed Step I and II, respectively, could be described apparently as first order, with respect to oxygen, and zero order, with respect to total ferrous species. When the concentration of oxygen in the feed stream was varied under a constant gas velocity, the mean size based on the major axis of needle‐like particle decreased from 0.60 to 0.35 μm with increasing oxidation rate. When the gas velocity was varied under a constant oxygen concentration, the particle size was almost independent of the oxidation rate and was equal to ca. 0.6 μm. By the addition of a small amount of sodium dihydrogenphosphate (NaH₂PO₄), the major axis could be reduced to 0.2 μm with the minor axis and the oxidation rate almost unchanged.     

Application of Sagnac interferometer for measuring chromaticdispersion of installed single-mode fibres

A novel method is described which is suitable for measuring the chromatic dispersion of installed single-mode fibres by using a modified σ-type Sagnac interferometer, which contains an off-centred phase modulator. Chromatic dispersion is measured with high resolution from the output interference fringe without requiring any fast diagnostic equipment. Measurement of the chromatic dispersion of a single-mode fibre in the wavelength range 1.5-1.58 μm is demonstrated     

Degradation of polystyrene in supercritical n-Hexane

Degradation of polystyrene was carried out in supercritical n-hexane under reaction temperature ranging from 330 °C to 390 °C, pressure ranging from 30 bar to 70 bar and reaction duration of 90 min. The conversion of polystyrene increased with rising temperature and pressure. The degradation performance was influenced by the temperature rather than applied pressure. Polystyrene rapidly degraded in 30 min after reaching a prescribed temperature ranging from 350 °C to 390 °C. At a prescribed temperature of 390 °C, the degree of degradation was higher than 90%. The degradation reaction was examined experimentally at a relatively low temperature of 330 °C. The degradation of polystyrene by using supercritical n-hexane has been found to be more effective compared to general pyrolysis (thermal degradation). Among the selectivity of liquid products, that of a single aromatic ring group like styrene at 390 °C increased up to 65% in 90 min. It was found from the analysis by a gel permeation Chromatograph (GPC), that high molecular-weight compounds decreased but oligomers increased with rising temperature.     

Performance characteristics of a tower fermenter with mechanical foam control

For a bubble column (BC) treating foaming liquids, the characteristics of a rotating-disk mechanical foam-breaker (MFRD) fitted to the BC were examined. The foaming behaviour of the BC and the foam-breaking behaviour of the MFRD under various operating conditions were related to the changes in liquid hold-up in the foam. The gas hold-up in a mechanical foam-control system (MFS) with the MFRD was confirmed to be greater than the gas hold-up in a non-foaming system (NS) including antifoam agent (AF). Comparison of the volumetric mass transfer coefficient between the MFS and the non-foaming system, in terms of the specific power input, also demonstrated the superiority of mechanical foam control for oxygen transfer performance.     

Performance characteristics of mechanical foam‐breakers fitted to a stirred‐tank reactor

In a stirred‐tank reactor (STR), a comparison of the performance of mechanical foam‐breakers: a six‐blade turbine (F‐B), a six‐blade vaned disk (V‐D), a two‐blade paddle (T‐P), a conical rotor (C‐R), a fluid‐impact dispersion apparatus (FIDA) and a rotating disk mechanical foam‐breaker (MFRD) was carried out using defined foaming media. The foam‐breaking ranges (relative to the gas superficial velocity, U_g) of the T‐P, C‐R and FIDA were inferior to that of the F‐B, V‐D and MFRD. The power consumption, P_kc, for foam‐breaking in the MFRD was the lowest among the F‐B, V‐D and MFRD. Operation of the F‐B and V‐D in the STR caused a considerable amount of liquid droplets from the collapsed foam to be entrained with the exhaust air. © 2002 Society of Chemical Industry     

13-week subchronic oral toxicity study of phaffia colour in F344 rats

A 13-week subchronic oral toxicity study of phaffia colour was performed in both sexes of F344 rats by feeding of CRF-1 powder diet containing 0, 0.2, 0.6, 1.7 and 5%. Rats were randomly divided into 5 groups, each consisting of 10 males and 10 females. No animals died during the administration period. There were no treatment-related changes in body weight gain, hematological and blood biochemical examination. No treatment-related histopathological changes were also observed in any dosed groups. These findings indicate that the treatment of 5% phaffia colour in diet for 13 weeks does not cause any toxicological changes in rats.     

Sclerosing peritonitis associated with luteinized thecoma of the ovary

A unique case of bilateral luteinized thecomas of the ovary associated with sclerosing peritonitis is reported and the clinical and pathological features of this and previously reported cases are reviewed. The patient, 52 years of age, presented with abdominal distension and diarrhea. Pelvic imaging studies revealed bilateral ovarian tumors with ascites. Total abdominal hysterectomy and bilateral salpingo-oophorectomy with adhesiotomy of the small bowel were performed. Histologically, the ovarian tumor was composed of closely packed spindle to round-shaped cells, and within the spindle cell population, lutein-like cells were scattered singly or in clusters. Mitotic counts of spindle cells revealed 12 mitotic figures (MF) per 10 high-power fields (HPF) in one part of the left ovarian tumor, but other areas of the tumor showed less than 3 MF/10 HPF on average. The lesion from the resected small bowel showed prominent fibrosis, confined to the serosa with no evidence of metastasis from the ovarian tumor. The patient has undergone adhesiotomy with partial resection of the small bowel seven times since the first laparotomy because of the recurrent small bowel obstruction. The patient has survived with complications due to short bowel syndrome for 7 years after the initial surgery and so far no recurrence or metastasis of the ovarian tumor has been identified. The case reported here also supports the idea that luteinized thecoma of the ovary associated with sclerosing peritonitis may be a distinct clinicopathologic entity, in terms of the unique association and of the unique features of thecoma; that is, bilateral, hormonally inactive and apparently benign in spite of its highly mitotic activity. Additional attention should be paid to the patient's quality of life, which is often degraded by peritoneal fibrosis and small bowel obstruction.