DIFFUSION COEFFICIENTS FOR PREDICTING ROUGH RICE RE-WETTING BEHAVIOR

ABSTRACT

Thin-layer re-wetting experiments were conducted with medium grain rough rice in the temperature range of 17.8 to 45^°C and for relative humidities between 56 and 89.3%, with initial moisture contents in the range of 10.26 to 12.71% dry-basis to determine the diffusion coefficient of rough rice. Recent efforts to characterize the re-wetting characteristics of rough rice are summarized. New equation for temperature dependent liquid diffusion coefficients for medium grain rough rice are presented. The diffusion coefficient in re-wetting was lower than the drying. The results presented here, over typically five day re-wetting, will be useful in studying the longer term moisture transfer process occurring during ventilated storage.     

Influence of activated carbon pore structure on oxygen reduction at catalyst layers supported on rotating disk electrodes

Carbon materials are often used as catalyst supports, and for catalysts in electrodes of a polymer electrolyte fuel cell, carbon black has been used. Recently, it was found, however, that activated carbon could replace carbon black and besides, significantly improve the activity of the electrode catalyst layer for oxygen reduction. In the present study, to optimize the pore structure of activated carbon for further activity improvement, the influence of the pore structure on the activity was investigated using activated carbon of various specific surface areas and mean pore diameters. A catalyst layer was formed from activated carbon loaded with platinum and a polymer electrolyte. The activity of the layer was measured in an oxygen-saturated perchloric acid solution, supporting the layer on a rotating glassy carbon disk electrode. We found that increases in the specific surface area and mean pore diameter increased the activity and that the latter was more effective than the former mainly due to the enhanced mass-transfer in the pores; the catalyst layer formed from activated carbon with the largest mean pore diameter was the most active. Unless pores excessively develop and lose connections between particles, a large pore diameter is therefore desired for the fuel cell electrodes.     

Radiophotoluminescence phenomenon in copper-doped aluminoborosilicate glass

Radiophotoluminescence phenomena have been widely investigated on various types of materials for dosimetry applications. We report that an aluminoborosilicate glass containing 0.005 mol% copper exhibits intense photoluminescence in the visible region induced by X-ray and γ-ray irradiation. The luminescence is assigned to the 3d⁹4s¹ → 3d¹⁰ transition of Cu⁺. The proportionality of the intensity of the induced photoluminescence to the irradiation dose was confirmed up to 0.5 kGy using ⁶⁰Co γ-ray irradiation. Based on the spectroscopic results, a potential mechanism was proposed for the enhancement of the photoluminescence. The exposure to the ionizing radiation generates electron-hole pairs in the glass, and the electrons are subsequently captured by the Cu²⁺ ions, which are converted to Cu⁺ and emit the luminescence. For the glass containing 0.01 mol% copper, the pronounced enhancement of the photoluminescence was not observed because the reverse reaction, ie, the capture of the holes by the Cu⁺ ions, becomes prominent. The photoluminescence induced by the irradiation was stably observed for the glasses kept at room temperature and even for the glasses heat-treated at 150°C. However, the induced photoluminescence could be eliminated by the heat treatment at a temperature at 500°C, and the glass returned to the initial pre-irradiation state. The Cu-doped aluminoborosilicate glass is a potential candidate for use in dosimetry applications.     

Effect of surface properties of silica nanoparticles on their cytotoxicity and cellular distribution in murine macrophages

In this study, complexes composed of poly-l-tyrosine (pLT) and single-walled carbon nanotubes (SWCNTs) were produced and the dispersibility of the pLT/SWCNT complexes in water by measuring the ζ potential of the complexes and the turbidity of the solution were investigated. It is found that the absolute value of the ζ potential of the pLT/SWCNT complexes is as high as that of SWCNTs modified with double-stranded DNA (dsDNA) and that the complexes remain stably dispersed in the water at least for two weeks. Thermogravimetry analysis (TGA) and visualization of the surface structures of pLT/SWCNT complexes using an atomic force microscope (AFM) were also carried out.     

Photoinduced increase in surfactant solution viscosity using azobenzene dicarboxylate for molecular switching

We provide further insight into the photochemical control of viscoelasticity through the use of azobenzene sodium dicarboxylate for molecular switching. As a photoresponsive molecule, Sodium 3,3'-azobenzene dicarboxylate (3,3'-Azo2Na) was added to a solution of cetyltrimethylammonium bromide (CTAB)/sodium salicylate (NaSal), which is known for inducing the formation of wormlike micelles. This solution maintained a wormlike micellar structure, although a reduction in zero-shear viscosity was observed. When this mixed aqueous solution of CTAB/NaSal/3,3'-Azo2Na (16.7 mM each) was irradiated by ultraviolet light, the 3,3'-Azo2Na exhibited molecular trans-cis photoisomerization. We measured the dynamic viscoelasticity of the sample in the photostationary state and found that the zero-shear viscosity increased approximately sevenfold compared to the preirradiation state. This phenomenon is the opposite of the system wherein viscosity reduced by irradiation, as reported by us. We discuss the mechanism of this viscosity change.     

Ash deposition behavior of upgraded brown coal in pulverized coal combustion boiler

Ash with a low melting point causes slagging and fouling problems in pulverized coal combustion boilers. Ash deposition on heat exchanger tubes reduces the overall heat transfer coefficient due to its low thermal conductivity. The purpose of this study is to evaluate the ash deposition for Upgraded Brown Coal (UBC) and bituminous coal in a 145 MW practical coal combustion boiler. The UBC stands for Upgraded Brown Coal. The melting temperature of UBC ash is relatively lower than that of bituminous coal ashes. Combustion tests were conducted on blended coal consisting 20 wt.% of UBC and 80 wt.% of bituminous coal. Before actual ash deposition tests, the molten slag fractions in those coal ashes were estimated by means of chemical equilibrium calculations. The calculation results showed the molten slag fraction for UBC ash reached approximately 90% at 1523 K. However, that for blended coal ash decreased to 50%. These calculation results mean that blending UBC with bituminous coal played a role in decreasing the molten slag fraction. This phenomenon occurred because the coal blending led to the formation of alumino-silicates compounds as a solid phase. Next, ash deposition tests were conducted using a practical pulverized coal combustion boiler. A water-cooled stainless-steel tube was inserted in locations at both 1523 K and 1273 K in the boiler to measure the amount of ash deposits. The results showed that the mass of ash deposition for blended coal did not greatly increase, compared with that for bituminous coal alone. Therefore, appropriately blending UBC with bituminous coal enabled the use of UBC without any ash deposition problems in practical boilers.     

Dietary supplementation of gamma-linolenic acid improves skin parameters in subjects with dry skin and mild atopic dermatitis

Disruption of the skin barrier function caused by epidermal hyper-proliferation, results in the skin becoming dry and showing high transepidermal water loss (TEWL). Gamma linolenic acid (GLA) is reportedly efficacious for treating TEWL and epidermal hyper-proliferation. In this study, to elucidate the effect of GLA-rich oil on skin function, GLA-containing food was given to adults with dry skin or mild atopic dermatitis and skin parameters were evaluated. In the results, we recognized beneficial effects on the TEWL index. The efficacy of GLA was also demonstrated to be statistically significant especially in subjects with pro-inflammatory features. The results suggest that the mechanism of improvement of skin barrier has been associated with possible generation of anti-inflammatory metabolites from GLA. The clinical physician also confirmed that none of the subjects showed any noteworthy side effects. GLA-enriched food appears to be safe and to improve skin barrier function in subjects with dry skin conditions and mild atopic dermatitis.     

Preparation of surfactant-free vinyl polymers by conventional emulsion polymerization using hydrolysable emulsifiers

Emulsion polymerizations of several vinyl monomers, styrene, methyl methacrylate, butyl methacrylate, butyl acrylate, and vinyl acetate, in water using alkali–hydrolysable cationic surfactants with a betaine ester group (1-alkoxycarbonylmethyl)trimethylammonium chlorides, as emulsifiers were carried out and properties of the resulting latices and the polymers recovered by hydrolysis and salting out were investigated. There were little influences of the surfactants and monomers used here on the polymerizations, forming stable and monodisperse latices with a mean diameter of ca. 70 nm and giving a high molecular weight of polymers at high yields. All polymers were precipitated and recovered by adding a small amount of sodium hydroxide into the latex solutions contained little amount of ionic species. Solvent-cast films of the polymers were found to have surfaces as hydrophobic as those for the corresponding pure polymers prepared by bulk polymerization.     

Fabrication and Pore Size Control of Large-Pore Mesoporous Silica Particles through a Solvent Evaporation Process

Large-pore mesoporous silica particles were synthesized through a solvent evaporation process using hydrophobic fumed silica particles and tetraethyl orthosilicate (TEOS) as silica sources. The solvent evaporation of an ethanol solution of fumed silica particles, TEOS, HCl and triblock copolymer (F127) resulted in mesoporous silica particles with pores with sizes of about 7 nm. In addition, the interplanar spacing of the mesoporous silica particles can be controlled by changing the solvent evaporation temperatures.