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  • Author or Editor: K. Takeda x
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Glass transition phenomena of four binary systems composed of simple hydrocarbons were studied by means of the differential thermal analysis (DTA). For all the systems, a definite glass transition was observed and a monotonous relation between the glass transition temperature (T g) and composition (x) was obtained. The composition dependence ofT g was analyzed in terms of the entropy theory based on the regular solution model. The theoretical prediction could not reproduce our results other than (1-butene)x(1-pentene)1−x system. This disagreement is considered to be due to deviations of the present systems from the regular solution, and the accompanying excess configurational entropy Sc E was estimated as a function of composition. Extraordinarily large values of Sc E? were obtained for (propene)x(propane)1−x and (propene)inx(1-pentene)1−x systems.

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121Sb Mössbauer spectra for M3Sb (M3 = Na3, K3, Na2K, Rb3) were measured at 12 K. The values of isomer shift (d) and quadrupole coupling constant suggest that the valence state of antimony in M3Sb is –3. The d values increase in the order Rb3Sb<K3Sb<Na3Sb<Na2KSb. The differences in d values are discussed by examining M–Sb distances and bond valence for M–Sb interactions. Some covalent interactions between alkali metal atoms and antimony atom are suggested.

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Tracer experiments on the chemical transformation of technetium in paddy soil and the transfer to rice seedlings have been carried out using 95mTc as a tracer. Two common Japanese soils, Andosol and Gray lowland soil were used in the soil incubation experiments. The chemical form of soluble Tc in soil water was a mixture of Tc-organic matter complex, Tc-iron complex and pertechnetate. An uptake experiment with rice seedlings using nutrient solution showed that the Tc-organic matter complex was less available than pertechnetate or the Tc-iron complex. These chemical forms of Tc were also observed in the root bleeding sap of rice seedlings when introduced to the nutrient solution containing soluble Tc. These results suggested that the transfer of technetium from soil to rice would depend on the chemical form of Tc and they would transport from the root to the leaf without chemical transformation.

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Tracer experiments on the transfer of carbon from culture solution to Daphnia magna through phytoplankton have been carried out using 13C and infrared absorption method. The purpose of this experiment is to investigate the experimental systems for the use of 13C in aquatic system. Daphnia magna was cultured in a 100 ml of solution containing phytoplankton and 20 mg of NaH13CO3 for 24 hours in the light and dark conditions (2000 lux, 14 hour light and 10 hours dark at 25 C). The concentration of 13C in Daphnia magna under light condition was about 2.0% (atom% excess), while in the dark condition 13C tracer was not detected. The concentration of 13C in phytoplankton under light condition was around 20%. It was suggested that 13C added as carbonate in the culture solution was photosynthetically assimilated by phytoplankton and then transferred to Daphnia magna. Using this system, the effect of UV-B exposure on the 13C uptake of Daphnia magna has been examined. The UV-B intensity was 95 mW/cm2 and exposure time was 15, 30, and 60 minutes. The concentration of 13C in Daphnia magna decreased with increasing exposure time. The Daphnia magna exposed to UV-B for 15 minutes intakes phytoplankton as much as control, while 30 minutes and 60 minutes exposures were lower than control. The lower concentrations of 13C observed in Daphnia magna were due to less intake of phytoplankton caused by the UV-B exposure.

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We have compared the 127I Mössbauer spectra of eleven organoantimony compounds with hypervalent bonding, E-Sb-I (E = O, I, N, C ). The charges on iodine atoms fall between -0.54 e for the compound with Sb-I bond length of 2.83 Å and -0.82 e for the compound with 3.34 Å. The negative charges on iodine atoms have been found to increase with the increase in the Sb-I bond lengths. Regarding to the dependence of the kind of E atoms, the negative charges on iodine atoms have been found to decrease with the increase in the electronegativities of E atoms. 121Sb Mössbauer spectra have shown the decrease of the group oxygen electronegativity of hexafluorocumyl alcohol by substituting CF3 for CH3, and this was reflected through O-Sb-I bonding as the increase in the negative charges of iodine atoms in the 127I Mössbauer spectra.

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The molar excess enthalpies of 1,2- and 1,3-propanediamine+1,2- and 1,3-propanediol have been determined at 298.15 K by using a twin-microcalorimeter which requires each component liquid 1 to 1.5 cm3 for a series of runs over the whole range of mole fraction. All excess enthalpies are exothermic and large. An equilibrium constant K1 expressed in terms of mole fractions and standard enthalpy of formation of 1:1 complex have been evaluated by ideal mixtures of momomeric molecules and their associated complexes.

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Four kinds of Dy(III) hexacyanometalates (II or III), DyFe(CN)6·4H2O (1), KDyFe(CN)6·4H2O (2), DyCo(CN)6·4H2O (3), and KDyRu(CN)6·4H2O (4) have been investigated by 161Dy Mössbauer spectroscopy. 161Dy isomer shifts of four compounds fall in the range of +3 ionic compounds. Although all spectra 1-4 show an almost symmetric line, the broadening of the line-width is observed on lowering the temperature due to the paramagnetic relaxation. As a parameter of intermolecular force constant, the M 2 value obtained for 161Dy of 1 is slightly larger than that of 2.

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We have measured the 57Fe Mössbauer spectra of the Hofmann pyridine complex Fe(pyridine)2Ni(CN)4 sample before and after exposure to high pressure of gaseous xenon. The temperature dependence of the high spin molar fraction has been determined from the 57Fe Mössbauer spectra. The spin transition of the sample without the high pressure treatment occurs between 175 and 220 K with a hysteresis width of 15 K. Although the 57Fe Mössbauer spectra suggest that the spin crossover behavior of the sample before and after the high pressure treatment are almost the same, the hysteresis of the latter sample is somewhat larger.

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