Digital Computer Control of a Research Reactor

This report describes a feasibility experiment for a fully automatic operation of Hitachi Training Reactor, emploving an digital computer control system. The system consists of a small control computer (2K words), an input-output peripherals, 3 BF3 counters and a countrol rod mechanism driven by a pulse motor.     

GaInAs-GaInNAs-GaInAs intermediate layer structure for longwavelength lasers

Proposes two new structures, the GaInAs-GaInNAs intermediate layer (IML) and the GaInN_xAs graded wells, which show better optical properties than the commonly used GaInNAs-GaAs rectangular quantum-wells. A 1240-nm emitting IML laser has been achieved with a low-threshold current density (200 A/cm²/well) and a relatively high characteristic temperature (T_o=100 K). The IML structure is very promising for long wavelength GaAs-based laser applications     

Shear viscosity of rubber modified thermoplastics: Dynamically vulcanized thermoplastic elastomers and ABS resins at very low stress

The shear viscosity of PP-EPDM dynamically vulcanized thermoplastic elastomers and ABS resins were investigated using (a) a constant shear stress creep instrument, (b) a rotational rheometer, and (c) a capillary extrusion rheometer. It was found that stresses exist for some of these materials below which they exhibit only finite deformations. This indicates they exhibit yield values. Much attention was given to measurements of creep at low stresses especially in the neighborhood of yield values. The magnitudes of the yield stresses obtained from these low stress measurements are significantly lower than those obtained using standard extrapolation to zero shear rate of higher stresses from rotational instruments. We also observed a high shear viscosity (～10⁹ PA s) plateau in the materials of high rubber content. We contrasted our results to those found in the literature.     

GaAs/AlGaAs directional coupler switch with submillimetre device length

A GaAs/AlGaAs directional coupler switch, for the first time with a device length shorter than 1 mm, has been fabricated by utilising the good controllability of molecular beam epitaxy and reactive ion beam etching. The switching voltage is as low as 5V. The extinction ratio is 17dB for a crossover state and 14dB for a straight-through state.     

Reduced incidence of Helicobacter pylori infection in young Japanese persons between the 1970s and the 1990s

The activity of eight topoisomerase inhibitors was investigated against five clinical isolates of Pneumocystis carinii. Susceptibility tests were performed by inoculation of the organisms on to a cell monolayer and parasites were counted after 72 h incubation at 37 degrees C. Culture plates were added with Dulbecco's modified Eagle's medium containing serial dilutions of lomefloxacin, norfloxacin, ofloxacin, pefloxacin, rufloxacin, camptothecin, amsacrine and etoposide. Atovaquone, pentamide isethionate and co-trimoxazole were used as control drugs. Etoposide gave inhibition comparable to that observed with atovaquone. Poor activity was demonstrated by pefloxacin, while the other topoisomerase inhibitors had no significant effect.     

The initial step of the thermal unfolding of 3-isopropylmalate dehydrogenase detected by the temperature-jump Laue method

A temperature-jump (T-jump) time-resolved X-ray crystallographictechnique using the Laue method was developed to detect small,localized structural changes of proteins in crystals exposedto a temperature increase induced by laser irradiation. In achimeric protein between thermophilic and mesophilic 3-isopropylmalatedehydrogenases (2T2M6T), the initial structural change uponT-jump to a denaturing temperature (~90°C) was found tobe localized at a region which includes a ß-turn and aloop located between the two domains of the enzyme. A mutant,2T2M6T-E110P/S111G/S113E, having amino acid replacements inthis ß-turn region with the corresponding residues ofthe thermophilic enzyme, showed greater stability than the originalchimera (increase of T_m by ~10°C) and no T-jump-inducedstructural change in this region was detected by our method.These results indicate that thermal unfolding of the originalchimeric enzyme, 2T2M6T, is triggered in this ß-turn region.     

Novel Video Memory Reduces 45% of Bitline Power Using Majority Logic and Data-Bit Reordering

We propose a low-power two-port SRAM for real-time video processing that exploits statistical similarity in images. To minimize the discharge power on a read bitline, a majority-logic circuit decides if input data should be inverted in a write cycle, so that ldquo1rdquos are in the majority. In addition, for further power reduction, write-in data are reordered into digit groups from the most significant bit group to the least significant bit group. The measurement result of a 68-kbit video memory in a 90-nm process demonstrates that a 45% power saving is achieved on the read bitline. The speed and area overheads are 4% and 7%, respectively.     

Environmental stress cracking of poly(acrylonitrile-butadiene-styrene)

The environmental stress cracking (ESC) of acrylonitrile-butadiene-styrene (ABS) copolymer caused by a non-ionic surfactant (poly-oxyethylene alkylether) was studied by constant-load tensile creep tests and edge crack tension (ECT) tests. The fracture surfaces were investigated by a scanning electron microscope (SEM) and the morphology of the crack tip was investigated by a transmission electron microscope (TEM). It was found that the results of the creep tests performed in the non-ionic surfactant were very different from those performed in air. SEM images of the fracture surfaces showed that there were three different mechanisms of fracture and that specimens had a tendency to rupture by ESC when the stress was small. The results of the ECT tests and the TEM images showed that the change in the mechanism of the fracture was attributable to the change of morphology at the crack tip.