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  • Author or Editor: M. Nakamura x
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Abstract  

The effect of network structure on the glass transition temperature (T g) was examined by differential scanning calorimetry, thermomechanical analysis and dynamic thermomechanometry for epoxy resins cured with mixtures of curing agents consisting of an active ester, 1,3,5-triacetoxybenzene (TAB), and a polyfunctional phenol, 1,3,5-trihydroxybenzene (THB). Free hydroxyl groups are formed from THB after curing, whereas acetyl groups are left from TAB. TheT g value of cured epoxy resins decreased with increasing TAB content in the curing agent, which is attributed to the looser network structure induced by the steric hindrance of acetyl groups from TAB in the curing reaction and also to the weaker intermolecular interaction and the internal plasticization of acetyl groups from TAB.

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Abstract  

Transport of La, Nd, Eu, Tb, Tm and Lu through a supported liquid membrane (SLM) was investigated by using di(2,4,4-trimethylpentyl)phosphinic acid (DTMPPA) as a mobile carrier. Lanthanoid elements in the feed solution were quantitatively transported and concentrated into the product solution of mild acidity. The transport rates increased with increasing atomic number of lanthanoids in the low pH region of the feed solution. Separation factors evaluated from the transport rates for lanthanoids were close to those from the distribution ratios in liquid-liquid extraction.

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Abstract  

The rate constant of radiation induced exchange reaction between thallium(I) and thallium(III) ions has been studied for elucidating the mechanisms which are responsible for (T1(II) intermediates or bridging groups (SO 4 2– ) in sulfuric acid and perchloric acid solutions. It was found that the radiation induced exchange reaction is accelerated by the sulfate ion, and the rate of the thallium(II)-thallium(I) reaction is faster than that of the thallium(II)-thallium(III) process in perchloric acid solution.

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Abstract  

Japanese iron artifacts contain a small amount of charcoal which was used in manufacturing. We developed a wet method of carbon extraction from the iron samples for AMS radiocarbon dating. The method consists of dissolution of iron with a Cu2+ solution and dissolution of deposited Cu in HCl. High extraction yields (80–90%) and low contamination by modern carbon were achieved by the wet method.

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Abstract  

The stability constants , of monochloride complex of Eu(III) in the tracer concentrations have been determined in the mixed system of dimethyl sulfoxide (DMSO) and water with 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values of decrease up to about 0.2 mole fraction of DMSO (X s) in the mixed solvent system and then increase. Calculation of Eu3+−Cl distance using a Born-type equation of the Gibbs' free energy derived from the revealed that the estimated distance between Eu3+ and Cl (d Eu−Cl) increases linearly withX s in 0≤X s<0.043 and 0.043<X s<0.172, but their slopes are different. The line in the first region means a linear enlargement of the thickness of the primary solvation sphere of Eu3+ with increasingX s. The larger slope againstX s in 0.043<X s<0.172 is attributable to lowering of , based on the increase in the solvation number of the primary solvation sphere of Eu3+. The considerably large value ofd Eu−Cl atX s=0.202 might result from lowering of by a coordination of ClO 4 into the secondary solvation sphere of Eu3+ and the extremely drop ofd Eu−Cl atX s=0.276 might reflect on a conversion of the ion-pair type, i.e., the coexistence of two kinds of a solvent-shared ion-pair and a contact one by the appearance of the contact one.

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Abstract  

Tritium concentrations were analyzed for coastal seawater and lake water collected from various places in Japan. Low tritium concentrations were observed for coastal seawater of small islands and it was attributed to a short residence time of the ground-water in such a small island. Tritium concentrations in lake water showed a significant variation. And it was revealed that the size of the lake and its drainage area were the dominant factors controlling the tritium concentrations in lakes.

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Abstract  

The stability constants, β1, of each monochloride complex of Am(III) have been determined in a mixed system of methanol and water at 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values of β1 of Am(III) decrease up to about 0.1 mole fraction of methanol (X s) in the bulk solutions and then increase with increasingX s when 0.1<X s≤0.4. The distance of Am3+−Cl in the mixed system was estimated using a Born-type equation. From the estimated distance of Am3+−Cl (d Am−Cl), it is concluded that AmCl2+ in the aqueous solution is present as a solvent-shared ion-pair. Further, based on the variation of dAm−Cl with increasingX s, the variations of β1 in the system are accounted for by the size-variation of the primary solvation sphere around Am(III) and by an effect due to the presence of a slight covalency in the solvation of Am(III).

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Abstract  

The stability constants, β1, of each monochloride complex of Ln(III) (Ln=Nd or Tm) have been determined in the mixed system of dimethyl sulfoxide (DMSO) and water with 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values of β1 of Ln(III) decrease to about 0.2 mole fraction of DMSO (X s) in the mixed solvent system and then increase withX s (>about 0.2). However, the variation mode of β1 of Nd(III) withX s somewhat differs from that of Tm(III). Calculation of Ln3+−Cl distance using a Born-type equation of the Gibbs' free energy derived from the β1 evealed the followings: (1) For Tm3+ with coordination number 8, the estimated distance between Tm3+ and Cl (d Tm-Cl) increases linearly withX s in 0.00≤X s≤0.17. This means an enlargement of the primary solvation sphere size of Tm3+ withX s. On the other hand, thed Tm-Cl shows a decrease withX s in 0.17<X s<0.28. (2) The estimatedd Nd-Cl increases linearly withX s in 0.00≤X s<0.06 and 0.06<X s≤0.17, but their slopes are different. The larger slope againstX s in 0.06<X s≤0.17 is attributable to a lowering of the β1 by a coordination of ClO4 into the secondary solvation sphere of Nd3+ and/or by an increase in the solvation number of the primary solvation sphere of Nd3+.

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Abstract  

The stability constants, 1, of each monochloride complex of Nd(III) and Tm(III) have been determined in the mixed system of methanol and water with 1.0 mol·dm–1 ionic strength using a solvent extraction technique. The values of 1 of Nd(III) and Tm(III) increase as the mole fraction of methanol in the mixed solvent system (X s) increases. However, the variation mode of 1 againstX s in the region of 0.00 X s 0.40 differs from each other, a concave curve for the Nd(III) and a convex curve for the Tm(III). The LnCl2+ formed is present as a solvent-shared ion-pair. Since Cl is a structure breaking ion, it was assumed that the primary solvation sphere of Ln3+ directly contacted with Cl. Calculation of Ln3+–Cl distance using Bom-type equation revealed the followings: (1) for Tm3+ with coordination number 8, the estimated distance between Tm3+ and Cl increases linearly withX s in 0.00 X s 0.40. The results mean an increase of the primary solvation sphere size of Tm3+ withX s. (2) For Nd3+, the distance between Nd3+ and Cl decreases linearly withX s in 0.00 X s<0.13, where both coordination numbers of 9 and 8 coexist, while it increases withX s in 0.13<X s 0.40. The results mean a decrease of the primary solvation-sphere size of Nd3+ withX s in 0.00 X s<0.13 and an increase of that withX s in 0.13<X s 0.40.

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Abstract  

The stability constans, 1, of each monochloride complex of Eu(III) have been determined in the methanol and water mixed system with 1.0 mol·dm–3 ionic strength using a solvent extraction technique. The values of 1 increase with an increase in the mole fraction of methanol (X S) in the mixed solvent system when 0 X S 0.40. The, distance of Eu3+–Cl in the mixed solvent system was calculated using the Born-type equation and the Gibbs' free energy derived from 1. Calculation of the Eu3+–Cl distance and the preferential solvation, of Eu3+ by water proposed the variation of the outersphere complex of EuCl2+ as follows: (1) [Eu(H2O)9]3+Cl, [Eu(H2O)8]3+Cl and [Eu(H2O)7(CH3OH)3+Cl inX S 0.014, (2) [Eu(H2O)8]3–Cl and [Eu(H2O)7(CH3OH)]3+Cl in 0.014<X S<0.25 and (3) [Eu(H2O)7(CH3OH)]3–Cl and [Eu(H2O)6(CH3OH)[2 3+Cl in 0.25<X S 0.40.

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