In Situ Observation of Zirconia Particles at 1200°C by High-Resolution Electron Microscopy

Zirconia (ZrO₂) particles (average diameter, 30 nm) were observed in an in situ heating experiment up to 1200°C using a 400-kV high-resolution electron microscope. Thermal vibration of atoms on a (001) surface plane was observed at 1100°C. At 1200°C, grain growth and sintering phenomena were recorded on a videotape, showing (100) lattice planes migrating on a surface of a particle. Direct observation of the sintering process on a lattice level was accomplished for the first time.     

Effects of hematocrit variations on cerebral blood flow and oxygen transport in ischemic cerebrovascular disease

The contribution of hematocrit (Ht) changes on cerebral blood flow (CBF) and brain oxygenation in ischemic cerebrovascular disease is still controversial. In the present study, effects of Ht variations of CBF and oxygen delivery were investigated in patients with ischemic cerebrovascular disease. CBF was measured by the Xe-133 intracarotid injection method in 27 patients, whose diagnoses included completed stroke, reversible ischemic neurological deficit, and transient ischemic attack. Ht values in the patients ranged from 31 to 53%. There was a significant inverse correlation between CBF and Ht in these Ht ranges. Oxygen delivery, i.e., the product of arterial oxygen content and CBF, increased with Ht elevation and reached the maximum level in the Ht range of 40-45% and then declined. The CBF-Ht and oxygen transport-Ht relations observed in our study were similar to those in the glass-tube model studies by other workers rather than to those in intact animal experiments. From these results, it is conceivable that in ischemic cerebrovascular disease, the vasomotor adjustment was impaired in such a manner that the relations among Ht, CBF, and oxygen delivery were different from those in healthy subjects. Further, an "optimal hematocrit" for brain oxygenation was also discussed.     

Effects of Aliphatic Alcohols on Formation of Cyclodextrin from Soluble Starch by Bacillus macerans Cyclodextrin Glucanotransferase

Effects of aliphatic alcohols such as ethanol, n-butanol and n-decanol on the formation of cyclodextrin (CD) from soluble starch by Bacillus macerans cyclodextrin glucanotransferase (CGTase) were experimentally studied at 50°C and pH 6.0. The addition of such aliphatic alcohols caused an increase in α-CD yield, which extent was remarkable in n-butanol. From the incubation of α-CD with CGTase, such an increase was found to be due to a restriction on further transglycosylation of α-CD into β-CD by CGTase imposed by the aliphatic alcohols.     

Magnetic resonance imaging in the diagnosis of jejunal leiomyoblastoma

We report a case of large leiomyoblastoma of the jejunum. The sagittal views in pre-operative magnetic resonance imaging (MRI) indicated that a cystic tumor with solid component was present, sequential from the small bowel. We suspected a smooth muscle tumor of the small bowel, but did not rule out the malignancy. The operative diagnosis was smooth muscle tumor of the proximal jejunum, and partial resection of the small bowel was performed. The pathological examination revealed benign leiomyoblastoma of the jejunum without metastasis. MRI contributed to the pre-operative diagnosis of the origin of this rare tumor, in a non-invasive fashion.     

Crystallographic study of the tempering of martensitic carbon steel by electron microscopy and diffraction

Structural changes taking place during the tempering proceed in four stages. At the preliminary stage taking place below 370 K, interstitial carbon atom clusters are formed below 270 K, rearrange to make a modulated structure between 270 and 360 K, and disappear at about 370 K. A long period ordered phase with respect to the interstitial carbon atoM_s or interstitial vacancies also appears between 330 and 350 K. With the disappearance of these structures, the first stage takes place between 370 and 470 K, where η-Fe₂C is formed in the matrix of low carbon martensite. The second stage o°Curs around 550 K with the retained austenite decomposing to θ-Fe₃C and α iron. At the su°Cession of the first stage, the third stage appears in a temperature range from 470 to 900 K, where θ-Fe₃C,X-Fe₅C₂ and also higher carbides θ_n-Fe_2n+1C_n intergrow microsyntactically in the particles precipitated below 720 K, but only θ-Fe₃C is formed above this temperature. Y. HIROTSU formerly Research Associate of Tokyo Institute of Technology. T. SUZUKI formerly Graduate Student of Tokyo Institute of Technology This paper is based on a presentation made at the “pcter G. Winchell Symposium on Tempering of Steel” held at the Louisville Meeting of The Metallurgical Society of AIME, October 12-13, 1981, under the sponsorship of the TMS-AIME Ferrous Metallurgy and Heat Treatment Committees.     

Liquid mixing by large gas bubbles in bubble columns

Liquid mixing by large gas bubbles of spherical cup was investigated for co- and counter-current contact of air-water system with bubble columns of 5 and 10 cm dia. The results obtained are that for the column of 5 cm dia., the longitudinal dispersion coefficient ranges from 5 to 20 cm²/sec for superficial gas velocity from 0·07 to 8 cm/sec and that for the one of 10 cm in diameter it ranges from 9 to 45 cm²/sec for that from 0·035 to 8 cm/sec. Liquid mixing under the coexistence of large and small bubbles was also investigated and it was found that the gas holdup was fairly well explained by an equation derived on the assumption that the mixture of small bubbles and liquid behaves independently of large bubbles. The expansion model was applied to the experimental results on the longitudinal dispersion coefficient and it was observed that there should be the lower limit in the holdup of small bubbles where this model can be applied.     

Effects of zinc doping in DFB lasers emitting at 1.3 and 1.55 mu m

Reports on the performance of GaInAsP/InP DFB lasers with Zn-doped active region. At both 1.3 and 1.55 mu m the authors achieved a large bandwidth owing to the increased differential gain. The carrier lifetime of the lasers decreased with doping level. The decreased carrier lifetime had the effect of reducing the pattern effect, and they could obtain a clear eye opening with 4 Gbit/s NRZ modulation.<>     

Power reduction techniques for a 1-Mb ECL-CMOS SRAM with an accesstime of 550 ps and an operating frequency of 900 MHz

This paper describes power reduction circuit techniques in an ultra-high-speed emitter-coupled logic (ECL)-CMOS SRAM. Introduction of a 0.25-μm MOS transistor allows a Y decoder and a bit-line driver to be composed of CMOS circuits, resulting in a power reduction of 34%. Moreover, a variable-impedance load has been proposed to reduce cycle time. A 1-Mb ECL-CMOS SRAM was developed by using these circuit techniques and 0.2-μm BiCMOS technology. The fabricated SRAM has an ultrafast access time of 550 ps and a high operating frequency of 900 MHz with a power dissipation of 43 W     

Qualitative change of resonant peaks in thermal emission from periodic array of microcavities

Experimental results are reported of thermal emission from tantalum surfaces having a two-dimensional periodic army of microcavities. Thermal emission from such surfaces has clear peaks caused by two different resonances of electromagnetic waves. It is found that the physical origin of the resonant peaks changes when the aperture ratio of the surface increases.