Photosensitive Mechanism of Dopant-Free, Ultraviolet-Sensitive Calcium Aluminate Glasses

Calcium aluminate glasses show high sensitivity to ultraviolet radiation without the doping of optically active components. A mechanism is proposed to account for their photosensitivity on the basis of the result that the cause of UV-induced coloring is the emergence of two kinds of paramagnetic centers, an aluminum-oxygen hole center (Al-OHC) and an ozonide (O^-₃). In this model, a peroxy linkage connecting tetrahedrally coordinated Al³⁺s and a physically dissolved O₂ molecule are assumed to be present in the glasses as structural defects. On exposure to UV rays, the peroxy linkage homolvtically dissociates into a pair of A1-OHC's by absorbing UV quanta and one of the two resulting A1-OHC's combines with a nearby O₂ to form an ozonide. Experimental evidences substantiating the mechanism are also reported.     

Study on Acceleration Factor at 5000 h Multiple Stress Test and Aging Evaluation of EVA Insulator

The authors carried out an outdoor exposure test and the 5000 h multiple stress test to ethylene vinyl acetate (EVA) polymer composite insulator used for 22 kV distribution line and an attempt was made to estimate the acceleration factor of the 5000‐h multiple stress test corresponding to the climate condition of the Kyushu area. By comparing dry band arc cumulative charge of leakage current at 5000‐h multiple stress test with that in the outdoor exposure test, the authors estimated the acceleration factor of the 5000‐h multiple stress test to be about 20 times. The acceleration factor was found to almost agree with the evaluation result of the absorption of hydroxyl group by FT‐IR analysis and the surface roughness of the insulator, respectively. Finally, for the electrical property, the expected life of EVA insulator that the authors developed was confirmed to be more than 40 years.     

Reversibility of Salt Effects on the Thermal Stability of Potato Starch Granules

The reversibility of salt effects on the gelatinization of potato starch was investigated. Following the immersion of starch into sodium sulfate or sodium bromide solution, increase or decrease respectively in the structural stability of starch was noted. By washing salt-treated starch with water, the most retained salt was eliminated, and the gelatinization temperature and enthalpy resumed the values of the original control starch. Treating alternately with sodium sulfate and sodium bromide solution, the retained salt and gelatinization characteristics of starch changed reversibly depending on the kind of salt. The type of gelatinization behavior of starch in solutions containing different salts could be used to assess the magnitude of salt effects.     

Photosensitive Characteristics of Dopant-Free, Ultraviolet-Sensitive Calcium Aluminate Glasses

Calcium aluminate glasses show high sensitivity to ultraviolet radiation without the doping of optically active components. In this paper, photosensitive characteristics and the cause of UV-induced coloring were investigated for these glasses. Ultraviolet rays below 270 nm were effective for inducing the coloring. The most effective wavelength agreed with that of the apparent absorption edge. In the ternary system with SiO₂ or GeO₂, the sensitivity was monotonically reduced with the amount of the third component and almost vanished for the compositions containing 40 mol%. On the basis of the establishment of a close correlation between two optical absorption bands and two electron spin resonance signals induced by UV illumination, the UV-induced coloring was concluded to be due to the emergence of an aluminum-oxygen hole center (Al-OHC) and an ozonide (O₃^-).     

Synthesis temperature dependence of morphologies and properties of cobalt oxide and silicon nanocrystals

Cobalt and cobalt oxide nanocrystals were synthesized on Si substrates from aqueous cobalt nitrate [Co(NO₃)₂·6H₂O] powder via chemical vapor deposition method. Scanning electron microscope, field emission scanning electron microscope, and transmission electron microscope observations show different morphologies, such as continuous films, nano-bars, nano-dices, and nano-strings, depending on the synthesis temperature. The crystal structure characterization was conducted using X-ray diffraction methods. Furthermore, the properties of the samples were characterized using Raman spectroscopic analysis and vibrating sample magnetometer. The morpholo- gy change was discussed in terms of synthesis environments and chemical interactions between cobalt, oxygen, and silicon.     

Hydrolysis of Soybean Proteins by a Vortex Flow Filtration Membrane Reactor with Aspergillus oryzae Proteases

Proteases consisting of various endo- and exo-proteases were prepared by homogenizing Aspergillus oryzae mycelia using a French-press. The hydrolysis of 1% soybean proteins was carried out at 35°C and pH 7.0. The back-pressure, flux and rotational speed of the reactor affected the hydrolysis rate and productivity. The reactor system could be operated in a continuous process by replenishing the substrate solution, with the concentration adjusted to maintain 0.43% substrate in the reaction vessel. Permeate flux gave a constant product as shown by molecular weight distribution and amino acid composition.     

Accumulation of Sucrose in Gamma-Irradiated Sweet Potato Roots

The effect of storage conditions on the sucrose content of gamma-irradiated sweet potato roots was studied. The sucrose content was influenced mainly by the temperature and oxygen content of the atmosphere. The degree of sucrose accumulation decreased, as the oxygen content of the atmosphere was reduced, while it increased with increase of temperature. The best conditions for the accumulation of sucrose were an irradiation dose of 1 kGy and a storage temperature of 30°C. The sucrose content of the roots which were irradiated and stored under the above conditions exceeded 12% on a fresh weight basis.