Gigahertz-band high-gain GaAs monolithic amplifiers using parallelfeedback technique

A high-grain multistage amplifier design technique is described. As countermeasures against FET drawbacks, the drain conductance dispersion was modeled and the DC parallel feedback was applied against process variations. Based on these and further feedback techniques, a limiting amplifier and a gain-controllable amplifier for satellite communication systems were designed and fabricated utilizing an 0.8 μm gate-length ion-implanted GaAs MESFET process. Moreover, their packages were developed considering stability conditions. A 45 dB 0.1-3.5 GHz limiting amplifier and a 22-38 dB 0.1-2.5 GHz gain-controllable amplifier were developed     

Fischer–Tropsch synthesis in slurry-phase reactors over Mn- and Zr-modified Co/SiO2 catalysts

Fischer–Tropsch (F–T) synthesis was carried out in a gas-flowed slurry-phase reaction system over Mn- and Zr-modified Co/SiO₂ catalysts. A 0.5 L stirred tank slurry reactor (STSR) was used for catalyst screening and a 12.5 L slurry bubble column reactor (SBCR) was used for trial pilot operation. While using the 0.5 L reactor for catalyst screening, Co supported on the SiO₂ with an average pore size of 10 nm showed a high catalytic performance for the F–T synthesis due to the suitable Co particle size in the catalyst. Zr promoter improved the activity and Mn promoter improved the stability of Co/SiO₂ catalyst for the F–T synthesis. H₂-TPR profiles indicated that Zr and Mn promoters improved the reduction degree of Co₃O₄ particles (on SiO₂ surface) to Co⁰ active species in H₂ flow at low temperature. While using the 12.5 L reactor for trial pilot operation over Mn–Zr–Co/SiO₂ catalyst, the space-time yield (STY) of C₅₊ hydrocarbons (liquid fuel) showed almost the same values when various solvents (n-C₁₆H₃₄, n-C₁₄H₃₀, diesel from petrol station, F–T crude oil) were used. Diesel and F–T crude oil are suitable for using in a large-scaled F–T synthesis plant owing to the low prices. Mn–Zr–Co/SiO₂ catalyst achieved a STY of C₅₊ hydrocarbons larger than 1000 g-C₅₊ kg-cat^? 1 h^? 1 in the 12.5 L reactor. The production capacity of liquid fuel from the 12.5 L reactor reached to 15.6 L per day (assumed for 24 h continuous operation). The stirring was very important for the F–T synthesis both reaction in the 0.5 L reactor and reaction in the 12.5 L reactor. The shape of slurry reactor also influenced the CO conversion for the F–T synthesis: reaction in the 12.5 L SBCR gave a higher CO conversion than that of reaction in the 0.5 L STSR (at the same W/F value under the same stirring speed) because the slender column reactor (SBCR) extended the residue time of reaction gas in the slurry-phase containing catalyst.     

Structural analysis of β-form poly(p-xylyene) starting from a high-resolution image

The crystal structure of β-form poly(p-xylylene) is analysed starting from a high-resolution image of a single crystal of this polymer. The high-resolution image corresponding to the projection of molecules onto the ab-plane along the chain axis shows clearly the mutual position of each molecule in a unit cell. The molecules are aligned wavily in the direction along the a-axis and the rough positions of their centres in a unit cell can be determined from the image. The refinement of the structure is carried out by the usual least-squares method using the intensities of electron and X-ray diffractions. The space group of the β-form is trigonal, P3, and the lattice dimensions are a=2.052 nm, c=0.655 nm and γ=120°. The unit cell contains 16 molecules and one of them is considered to occupy statistically one of three equivalent orientations so as to satisfy the P3 symmetry.     

Automatic Small Motor Noise Measuring Equipment

Measuring equipment for automatically testing the noise of small fan induction motors used in domestic appliances has been developed. This equipment has taken the place of the current inspection method, which uses man's trained sense of hearing. In order to develop this equipment, the following investigations were performed. First, through acoustic and vibration analysis, we clarified that various noises have their own characteristics of sound frequency which were found to be very similar to the characteristics of vibration frequency detected by a vibration sensor, mounted on the motor frame surface. Secondly, through the consideration of the relations between the levels of noise and vibration and man's sense of hearing, we obtained a satisfactory mutual relationship between man's sense and vibration levels. By using these clarifications, we have succeeded in making automatic measuring equipment which judges the noise level and the kind of noise, using a microcomputer with programs based on the investigations. Thus two results have been produced. One is the saving of labor and time in the motor manufacturing process, the other is improved accuracy and convenient trouble-free testing in noisy surroundings.     

Successful management of primary left ventricular aneurysm (of the apex) in a child

A technique has been worked out for determining amino alkyl phosphonic acids in ruminal fluid by using methods of hydrolysis, partition of the phosphonic acid on a cation exchange column and ashing of the eluate. After evaporation to total dryness the phosphonic acids were determined as phosphates. The amounts of acid found in the ruminal fluid of goats varied between 0.4 and 1.1 muMol/ml. In view of the fact that these acids are microbial compounds it will appear that any change in the amount of compounds produced in the rumen would indicate changes in the concentration of the microbial mass in the rumen.     

Direct imaging of molecular chains in a poly(p-xylylene) single crystal

Individual chains comprising a β-form poly(p-xylylene) (PPX) single crystal were resolved with a high resolution electron microscope (JEM-500). In a polymer crystal the important limiting factor for resolution is radiation damage. The total end point dose of a PPX crystal is about 0.5 coulomb cm^?2 for 500 kV electron irradiation which is more than 20 times greater than that for a polyethylene crystal. The high resolution image obtained was processed by optical filtering to reduce noise due to the granularity of film. The processed image, which corresponds to the ab-plane projection of polymer chains, shows clearly the mutual arrangement of each molecule in the crystal. This high resolution image is sufficient to provide a starting point for determining the unknown crystal structure of the β-modification of PPX.     

Hydrodynamic studies of dilute pitch solutions: The shape and size of pitch molecules

The shape and size of pitch molecules were discussed through the measurements of the intrinsic viscosity [η] and the diffusion coefficient D of molecular weight fractionated petroleum pitches in dilute chloroform solutions, where [η] was measured by an Ubbelohde viscometer, and D by Northrup-McBain diaphragm cells. Hydrodynamical considerations on the [η] vs D relationship lead to a conclusion that pitch molecules examined are of 3-dimensional structure, the axial ratio being 1–3 under the oblate ellipsoid assumption, and their sizes being about 10 ~ 20 Å in equatorial diameter.     

Use of liposome encapsulated hemoglobin as an oxygen carrier for fetal and adult rat liver cell culture

Engineering liver tissue constructs with sufficient cell mass for transplantation implies culturing large numbers of hepatocytes in a reduced volume; however, providing sufficient oxygen to dense cell cultures is still not feasible using only conventional culture medium. Liposome-encapsulated hemoglobin (LEH), an oxygen-carrying blood substitute originally designed for short-term perfusion, may be a good candidate as an oxygen carrier to cultured liver cells. In this study, we investigated the feasibility of maintaining long term hepatocyte cultures using LEH. Primary fetal and adult rat liver cells were directly exposed to LEH for 6 to 14 days in static culture or in a perfused flat plate bioreactor. The functions and viability of adult rat hepatocytes exposed to LEH were not adversely affected in static monolayer culture and were even improved in the bioreactor. However, some cytotoxicity of LEH was observed with fetal rat liver cells after 4 days of culture. LEH, though a suitable oxygen carrier for long-term culture of mature hepatocytes, is not suitable in its present form for perfusing fetal hepatocyte cultures in direct contact with the liposomes; either the LEH will have to be made less toxic or a more sophisticated bioreactor that prevents the direct contact between hepatocytes and perfusates will have to be designed if fetal cells are to be used for liver tissue engineering.     

Nitrosamine formation from vegetables produced in Japan

Many vegetables produced in Japan contain large amounts of nitrate that may be converted into nitrite in the oral cavity and afford carcinogenic nitrosamines in the stomach. On the other hand, vegetables contain ascorbate and other components that may affect the formation of nitrosamines. In this study, nitrosamine formation from vegetables with high nitrate content produced in Japan was examined under simulated oral cavity and stomach conditions. Extracts of chingensai, komatsuna and itomitsuba were digested with nitrate reductase and subsequently treated with an excess of morpholine at pH 3.0. The amount of N-nitrosomorpholine produced from each of the vegetable extracts was not affected by the vegetable components in the extracts. Addition of a large amount of ascorbate was required to decrease nitrosamine formation from the extract. The results indicated that nitrosamine formation from these vegetables could not be prevented by other components in the vegetables.