Direct preparation of porous polyethylene filters by radiation polymerization of ethylene

In order to prepare porous, macroscopically homogeneous filters without a separate packing process, ethylene was polymerized by radiation in glass tubes. The bulk density of the polyethylene is approximately proportional to ρ (? M)²I^0.9t², where ρ M is average ethylene density, ? M is average ethylene fugacity, I is radiation dose rate, and t is reaction time. The effect of the bulk density on “treatment capacity” was investigated by experiments where air samples containing 0.1 wt-% iodine vapor were filtered. Treatment capacity is difined as that amount of air per gram of polyethylene which passes through a filter until the polyethylene reaches the break point. The treatment capacity is approximately constant at 9 × 10² cm³/g over the bulk density range from 0.03 to 0.07 g/cm³, and it is lower at the outside of this range. The pressure drop due to the polyethylene filters varies with the 2.7th power of the bulk density when the bulk density is more than 0.03 g/cm³; below 0.03 g/cm³ this exponent increases with decreasing bulk density. Because of both the necessity of high Treatment capacity and that of low pressure drop, the optimum bulk density of polyethylene in the filter is about 0.03 g/cm³.     

Spatial integration properties in vision with chromatic stimuli

The present study showed that (1) the critical area of spatial integration was larger for equiluminous chromatic stimuli than for luminance stimuli, and that (2) the critical area became smaller as the chromatic saturation of the adaptation field was increased. The latter suggests that the chromatic coding systems, which are assumed to posses poorer spatial resolution or larger spatial integration than the luminance system, could change their spatial integrating organization independently of the luminance system which could also change its own spatial organization. © 1993 John Wiley & Sons, Inc.     

Enhancement of sonodynamic tissue damage production bysecond-harmonic superimposition: theoretical analysis of its mechanism

Among the nonthermal effects of ultrasound, acoustic cavitation may have the highest potential for therapeutic applications if it can be somehow controlled. Recent in vitro and in vivo experiments have demonstrated that sonochemically active cavitation can be enhanced an order of magnitude by superimposing the second harmonic onto the fundamental in insonation. Moreover, they have shown that sonochemically active cavitation can be controlled with relative ease, thereby even in a progressive wave field. The effect of second-harmonic superimposition on the rectified diffusion through the gas-liquid interface of cavitated microbubbles is estimated theoretically. The theoretical rectified diffusion rate explained an asymmetric behavior of the threshold for producing sonodynamic tissue damage as a function of the fundamental and the second-harmonic amplitudes. The tissue damage was produced with a focused progressive wave in a liver lobe of a mouse administered with a sonodynamically active agent. The result suggests that the acceleration of the rectified diffusion is a primary mechanism of the enhancement of sonodynamically effective cavitation by second-harmonic superimposition     

Measurement of bubble characteristics in a molten iron bath at 1600 °C using an electroresistivity probe

A two-needle, electroresistivity probe was developed to measure bubble characteristics such as gas holdup, bubble frequency, and bubble rising velocity in a molten iron bath at 1600 °C. The probe’s electrode was made of a 0.5-mm platinum wire coated with ZrO₂ cement and an outer coat of alumina as insulator. The life of this probe at 1600 °C was 15 to 20 minutes, making it possible to systematically measure bubble characteristics. The measured values of the bubble characteristics were compared with their respective empirical correlations derived from cold model experiments. Good agreement between the measured values and the empirical correlations was seen for each bubble characteristic. This electroresistivity probe allows us to measure bubble characteristics in actual metallurgical reactors with gas injection at high bath temperatures.     

Electroptic diffraction modulation in ZnO film on sapphire

An electrooptic Bragg diffraction modulator with high diffraction efficiency which utilizes a low-loss epitaxial ZnO optical waveguide on a sapphire substrate is discussed. An interdigital electrode with a spatial period of 20 μm and an aperture of 3 mm was fabricated directly on the film surface using a photolithographic technique. For the TE₀ mode at 6328 Å, a maximum diffraction efficiency of 98% has been obtained from DC to 100 kHz with an applied voltage of about 31 V. The unclamped electrooptic coefficient r ₃₃ is estimated to be 5.8×10^-12 m/V which is much larger than the clamped value of 2.6×10^-12 m/V in the literature     

Activities of phosphorous in liquid Ni + P alloys saturated with solid nickel

By using an electrochemical technique incorporating magnesia-stabilized zirconia electrolyte, the activities of phosphorous in liquid {Ni + P} alloys saturated with solid nickel were determined at temperatures between 1477 and 1663 K. The activities of phosphorus referred to gaseous diatomic phosphorous at 1 arm pressure,a _p, could be expressed by analytical formulas: 2 loga _p = logP _P2 = -5.6 -9700/(T/K) at temperatures between 1477 and 1612 K, and 2 loga _p = logP _P2 = -22.0 -17000/(T/K) at temperatures between 1612 and 1663 K. Formerly with Kyoto University, is retired.     

Synthesis of cationic flocculant by radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide in aqueous solution. II. Copolymerization at higher monomer concentration

The radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide was studied to prepare a polymer flocculant that can be handled as a solid. The product obtained in the presence of 5–20% water was a solid and could be ground to a powder without drying. In order to obtain a water-soluble polymer at a higher concentration, the effect of various additives on the copolymerization was investigated and found that alcohols bearing a hydrogen atom attached to the tertiary carbon atom effectively inhibit intermolecular crosslinking to give water-soluble polymer. It is suggested that the formation of water-insoluble polymer is predominantly attributable to the crosslinking of polymer chains rather than to the imidation of amide groups. Copolymerization in the presence of isopropyl alcohol as inhibitor of the crosslinking was also studied and compared with that reported previously, which was carried out at a lower monomer concentration without additives.     

Ellipsometric determination of optical properties of carbazole-containing poly(l-glutamate) thin films prepared from different solvents

In this study, the refractive indices (n) and thicknesses of carbazole-containing hole-transport materials such as poly(γ-carbazolylethyl l-glutamate) (PCELG) and poly(N-vinyl carbazole) (PVCz) films were determined by carrying out ellipsometric measurements. The thicknesses of PCELG and PVCz films determined by ellipsometric analysis were in good agreement with those determined by surface profilometry. The dependence of the refractive indices of the PCELG films on film thickness was classified into two types on the basis of the solvent from which the films were prepared: the refractive indices either increased with increasing film thickness, as in the case of PCELG films prepared from 1,2-dichloroethane (DCE) and monochlorobenzene (?-Cl), or were independent of the film thickness, as in the case of films prepared from 1,1,2,2-tetrachloroethane (TCE). A comparison of these results with the structures of the polymers, as determined by ¹H NMR, reveals that the two types of dependences of the refractive indices of the PCELG thin film on the film thickness can be attributed to the two types of aggregation structures and/or orientational characteristics corresponding to the helical conformation of the polymer. In contrast, the refractive indices of PVCz films are governed mainly by the film thickness. Finally, we would like to emphasize that the combination of ellipsometry and other techniques such as NMR and surface profilometry provide information not only on the film thickness and refractive index but also on the aggregation structure in thin films with thicknesses on the order of 50 nm.     

Development of neutron radiography facility for boiling two-phase flow experiment in Kyoto University Research Reactor

To visualize boiling two-phase flow at high heat flux by using neutron radiography, a new neutron radiography facility was developed in the B-4 beam hole of KUR. The B-4 beam hole is equipped with a supermirror neutron guide tube with a characteristic wavelength of 1.2 Å, whose geometrical parameters of the guide tube are: 11.7 m total length and 10 mm wide ×74 mm high beam cross-section. The total neutron flux obtained from the KUR supermirror guide tube is about 5×10⁷ n/cm² s with a nominal thermal output of 5 MW of KUR, which is about 100 times what is obtainable with the conventional KUR neutron radiography facility (E-2 beam hole). In this study a new imaging device, an electric power supply (1200 A, 20 V), and a thermal hydraulic loop were installed. The neutron source, the beam tube, and the radiography rooms are described in detail and the preliminary images obtained at the developed facility are shown.