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  • Author or Editor: M. Yoshida x
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Abstract  

The nanosecond pulse radiolysis technique has been applied to study the rate constants for charge transfer and substitution reactions of radical ions. Electron transfer from biphenyl anion to styrene derivatives shows a correlation with the reduction potential of the acceptors expected from the Marcus theory. The positive charge transfer from biphenyl cation to the same acceptors shows a much larger rate constant, suggesting a considerable shift of the free energy relationship to the positive side of Go. The substitution reaction of fluorenone anion with organic halides shows an SN2 character, while that of diethyl fumarate shows electron transfer nature. The dimerization of radical anions has been proven for benzophenone and fluorenone, when their lifetime of the parent anions are prolonged by countercations.

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Summary  

We investigated the influence of ionic strength on migration behaviors of Sr and Eu in the presence of humic acid (HA). The breakthrough curve of Sr through a quartz sand column in the presence of HA was identical to that in the absence of HA. Europium migration in quartz sand was enhanced by the presence of HA at low ionic strength. At high ionic strength, Eu migration in the presence of HA was hindered compared to that in the absence of HA. Adsorption of europium on quartz sand in the absence of HA decreases with increased ionic strength.

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Abstract  

Polyurethane composites with bagasse of sugar cane (BSC) at different proportions: 5, 10 and 20 mass/mass% were prepared by melt mixing method. The thermal behavior of these composites were studied by thermogravimetry (TG/DTG). The influence of fiber concentration on the kinetic parameters of the composites was studied and a better interaction was suggested between PU/BSC with 5mass/mass% of fiber. Scanning electron microscopy was carried out to investigate surface morphology.

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Abstract  

Coordination states of Eu(III) in anion exchange resin (AG 1X8) systems with LiCl-H2O/alcohol mixed media were determined from the luminescence lifetimes and the emission spectra of Eu(III). The sorption equilibrium of Eu(III) was discussed on the basis of the correlation between the distribution coefficients and the coordination states in the solution and resin phases. The sorption of Eu(III) was mainly caused by the formation of an anionic Eu(III)-chloro complex in the resin phase, which was enhanced by the decrease of 'free' water activity due to the addition of alcohol. The effect of ethanol added was larger than that of methanol.

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Summary Thermally induced structural transformation of fibrous hydrogen-bonded molecular assemblage formed from an amphoteric pyridinecarboxylic acid of 6-[2-propyl- 4-(4-pyridylazo)phenoxy]hexanoic acid (C5PR) was studied using differential scanning calorimetry (DSC), differential thermal analysis (DTA), and thermogravimetry (TG). The organized fibrous morphology formed in an aqueous solution was stable at temperatures below 150°C. The ordered crystalline solid phase (K1) of the original fibrous material altered to a disordered crystalline solid phase (K2) at 150°C and subsequently to an isotropic phase (I) at 172°C. In the isotropic state, the C5PR molecule was slowly decomposed by decarboxylation. Once the molecular assemblage was subjected to the mesophase by heating, another ordered crystalline solid phase (K3) appeared reversibly at 17°C. The heat budget analyses by DSC indicated that a conformational entropy change such as the side-chain propyl group and the main-chain pentamethylene unit in the hydrogen-bonded molecular assemblage took place between the two ordered crystalline solid phases K1 and K3.

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Abstract  

For three heavily exposed workers in the Tokai-mura criticality accident, the levels of 24Na, 42K and 82Br were measured in blood, urine, vomit and hair. 24Na showed the highest activity and was found to have a specific activity of 8.24·104, 4.34·104 and 1.23·104 Bq 24Na per g Na in blood of the three exposed workers. Based on these data the individual neutron fluences were calculated. Radionuclides were also measured in environmental samples from the JCO campus. The fission products 131I, 133I, 140Ba-140La and 137Cs were determined in plant samples and the activation products 59Fe, 46Sc, 60Co and 152Eu were identified in soil samples. 235U/238U ratios in soil and plant samples were measured by ICP-MS.

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Abstract  

We have investigated effects of shear flow on the structure of lamellar phase in hepta(oxyethylene glycol)—n—hexadecylether—water system using small-angle neutron scattering (SANS) under shear flow at the shear rates (

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) from 10–3 s–1 to 50 s–1. In the range
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=10–2 ~1 s–1, significant changes have been observed in both intensity and position of the reflection peak. Small-angle X-ray scattering without shear has been also measured at various concentrations and temperatures. It has been suggested from these results that the shear flow causes contraction of lamellar domains and formation of a new domain composed of disrupted bilayers which grows rapidly with increasing shear rate and reconstructs original microstructures.

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Abstract  

Nanoporous alumina membrane prepared by anodic oxidation using sulfuric acid electrolyte was subjected to TG-DTA and X-ray Photoelectron Spectroscopy (XPS or ESCA) to further study the distribution of sulfur. In XPS study, Ar+ ion bombardment was performed on the sample to etch the surface at a rate of 3 nm min-1. As a result, sulfur was found to be concentrated within a depth of 3nm from the surface. The S content of the surface was found to be 2.70.5 wt%, and that at a depth of ca. 3 nm and ca. 10 nm was found to be as low as about 0.60.11 wt% (5.371.0 wt%→ 1.260.2wt% SO2). In TG-DTA, the mass loss of 7.3% was in fair agreement with that calculated on XPS results (7.11.2%).

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Abstract  

Gamma-alumina membrane was prepared from anodic (amorphous) alumina (AA) obtained in a sulphuric acid electrolyte. The transformation scheme, i.e., the crystallization to form metastable alumina polymorphs and the final transition to α-Al2O3 with heating was studied by TG-DTA and X-ray diffraction (XRD) using fixed time (FT) method. When heating at a constant rate, the crystallization occurred at 900C or higher and the final formation of α-Al2O3 occurred at 1250C or higher, which temperatures were higher than the case of using anodic (amorphous) alumina prepared from oxalic acid electrolyte. Relative content of S of the products was obtained by transmission electron microscope (TEM)-energy dispersive spectroscopy (EDS). The proposed thermal change of anodic alumina membrane prepared from sulphuric acid is as follows: 1. At temperatures lower than ca 910C: Formation of a quasi-crystalline phase or a polycrystalline phase (γ-, δ- and θ-Al2O3); 2. 910–960C: Progressive crystallization by the migration of S toward the surface within the amorphous or the quasi-crystalline phase, forming S-rich region near the surface; 3. 960C: Change of membrane morphology and the quasi-crystalline phase due to the rapid discharge of gaseous SO2; 4. 960–1240C: Crystallization of γ-Al2O3 accompanying δ-Al2O3; and 5. 1240C: Transition from γ-Al2O3 (+tr. δ-Al2O3) into the stable α-Al2O3. The amorphization which occurs by the exothermic and the subsequent endothermic reaction suggests the incorporation of SO3 groups in the quasi-crystalline structure.

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