Hidehiko Arai

Invited Lecture. Complexities in the structure of ferroelectric liquid crystal cells The chevron structure and twisted states

Abstract To demonstrate the generality of the chevron structure in ferroelectric liquid crystal (FLC) cells, an optical micrograph is presented, which shows a series of defect lines clearly indicating this structure. The generality is understood as a direct manifestation of the smectic layer undulation playing an important role in the SASC (S*C) phase transition. By establishing the relation between chevrons and asymmetric focal conics, both of which have two senses, ±z, the boundaries between them with opposite senses, i.e. so-called zig-zag defects, have been characterized; the type boundary does not exist as a line but shrinks into a point. The interplay between the chevron structure and the director alignment has been described in detail; in particular, the appearance of unwinding lines in the middle of thick cells, the characterization of internal disclination loops in SSFLC cells, and the law regulating the emission and absorption of internal disclinations by zig-zag defects. With a view to removing...

Decoloration and degradation of azo dye in aqueous solution supersaturated with oxygen by irradiation of high-energy electron beams

Abstract The electron beam-induced decoloration and degradation of an azo dye (Acid Red 265) in aqueous solution supersaturated with oxygen were studied. The solution, in which the dissolved oxygen concentration (DO) was increased by pressurizing with oxygen gas up to O.3 MPa, was fed through a nozzle to a water channel under atmospheric pressure and irradiated with high-energy electron beams. It was confirmed that with high DO concentration, cleavage of aromatic rings of the dye molecules and reduction of total organic carbon were induced effectively by irradiation. The DO concentration by pressurizing under 0.3 MPa of oxygen was found to be adequate for the electron beam-induced oxidation of organic substances in water in the range of 5–14 kGy.

Dechlorination of chlorobenzene in air with electron beam

Abstract To get qualitative and quantitative data for the decomposition of chlorinated hydrocarbons, gaseous chlorobenzene of 10–40 ppm concentrations was irradiated under air condition with electron beam in the dose range of 0–10 kGy. The irradiation decomposed chlorobenzene, and formed gaseous products and aerosols. An irradiation dose of 10 kGy decomposed 80% of chlorobenzene at 10 ppm. Good mass balances on chorine (mgCl) and carbon (mgC) were obtained at doses of 4, 8 and 4 kGy with the addition of NH 3 . About 65% of chlorine in reacted chlorobenzene was dechlorinated by the irradiation at 4 and 8 kGy. The addition of NH 3 enhanced the dechlorination to about 80%. At least about 40% of the gaseous products was found to be aliphatic oxygenates like formate, acetate and α -ketoglutarate at doses of 4 and 8 kGy on the basis of carbon unit (mgC). These aliphatic oxygenates accounted for only 3% in the case of the aerosols. The FTIR analyses revealed that the aerosols consisted of low-vapor-pressured products that had nitrate groups and/or retained the aromatic ring.

Exhaustive degradation of humic acid in water by simultaneous application of radiation and ozone

Abstract The combination effect of ionizing radiation and ozone to degrade humic acid in water was superior to ozone and radiation alone. The humic acid treated by this combination method, followed by chlorination, produced only little trihalomethane and total organic halogen. A chain reaction mechanism was suggested for the oxidation of humic acid.

Electron-beam decomposition of vaporized VOCs in air

Abstract A study on electron-beam treatment was carried out to find out the effective decomposition conditions of vaporized volatile organic compounds. Air streams containing aromatic and aliphatic compounds were irradiated with electron beams in batch and flow systems. The research showed that chloroethene was readily decomposed through a chain reaction with one of the fragmentation products, Cl radical. A thermal electron and negative oxygen ion were important active species for decomposing carbon tetrachloride. The formation of particles was observed only from the irradiation of aromatics, like benzene, xylene, and chlorobenzene. Dechlorination of chlorobenzene was enhanced in the presence of ammonia.

Effect of irradiation temperature on the radiolysis of methane

Abstract The G-values of most products increase with temperature in the radiolysis of methane in a flow-type experiment over the temperature range 50–280°C at atmospheric pressure. The apparent activation energies of most products are higher at higher temperature region above 150°C than those obtained below about 100°C. Irradiation at higher temperature favors the formation of olefins. The results are qualitatively understood on the basis of known nature and reactivity of free radicals.

Radiation-induced decoloration and sedimentation of colloidal disperse dyes in water

Abstract The aqueous solutions of disperse dyes can not be easily decolored and sedimented by γ radiation. The change of pH after irradiation into acidic conditions made sedimentation occur effectively. In oxygen-saturated solutions, absorption band, change of pH and total organic carbon decreased markedly, while in nitrogen-saturated solutions a smooth decrease was seen. Sedimentation was also induced by addition of various electrolytes. The mechanism of the sedimentation was also discussed.

Radiolysis of methane containing small amounts of carbon monoxide—formation of organic acids

Electron beam irradiation of methane containing small amounts of carbon monoxide in a flow system at atmospheric pressure produced acetic and propionic acids in considerable yields. Propionic acid was formed in preference to acetic acid, especially at small molar ratios, [CO]/[CH4]. These acids were though to be formed via Koch-Haaf reactions CH3++CO→CH3CO+→H2OCH3COOH2+C2H5++CO→C2H5CO+→H2OC2H5COOH2+ The decrease in G(H2) observed by the addition of CO to methane was interpreted on the basis of the following reaction H+CO→k2HCO The estimated values of k2 were close to the reported value.

Radiation effects on COH2 gas mixture in the presence of silica gel

Abstract Electron beam irradiation of gas mixture of CO and H2 (1:6) in the presence of silica gel exclusively produces carbon dioxide and hydrocarbons in high yields. At the reaction temperature of 140°C, CO2 is preferentially produced, most of which are formed independently of hydrocarbons. The yields of hydrocarbons consisting predominantly of low molecular weight paraffins, obtained at 295°C, were higher by more than an order of magnitude than those by the homogeneous radiolysis and comparable to those by catalytic reactions over Fischer-Tropsch catalyst. Results obtained by irradiation of H2 over silica gel pre-irradiated under COHe gas stream indicate that secondary reactions between H2 and solid deposits produced from CO are responsible for the formation of hydrocarbons in the radiolysis of the COH2 mixture over silica gel.

The dependence of self-focusing of a high-intensity pulsed electron beam on gaseous media as studied by depth-dose distributions. III. Hydrocarbons and halogenomethanes.

The self-focusing of a pulsed electron beam in organic gaseous media was investigated as a function of pressure. The relative total ionization cross section of gases, obtained from the present study, is correlated with molar static electron polarization. Below 1 Torr the pinch initially enhances and then declines with increasing pressure. At pressures greater than 10 Torr, the beam exhibits the self-focusing again. The self-focusing between 10 and 40 Torr is successively stronger in gases interacting more strongly with secondary electrons, i.e.,