The concentrations of neutron-induced radionuclides have been measured in ground level air during the period between 1976 and 1981 at Nagoya (35° N, 137° E), Japan. Six Chinese atmospheric nuclear weapons tests were conducted by the government of China at Lop Nor (40° N, 90° E) during the period 1976–1981. The Chinese nuclear tests of November 17, 1976 (the 21st test) and October 16, 1980 (the 26th test), high-yield devices, produced54Mn,55Fe and88Y whose production reactions are54Fe(n, p),56Fe(n, 2n) and89Y(n, 2n), respectively. The tests of September 26, 1976 (the 19th test), September 17, 1977 (the 22nd test) and March 15, 1978 (the 23rd test), low-yield devices, produced54Mn,57Co and58Co whose production reactions are54Fe(n, p),58Ni(n, pn) and58Ni(n, p) respectively. No neutron activation product from the 24th test (December 14, 1978) was observed.
A simple and versatile method was developed to detect low specific-activity63Ni with a liquid scintillation counter. High counting efficiency was obtained for a sample containing up to 220 mg of nickel using a mixture of a violet solution of nickel ammine complex and an emulsifier liquid scintillator. The detection limit was 0.06 Bq g–1 Ni /1.6 pCi g–1 Ni/ assuming the counting for 1000 min and 95% confidence level.
Since the physical properties of lithium borate glasses xLi2O-(1-x)B2O3 (0<x< 0.28) vary over a wide range with the composition, this binary system is particularly suitable for studying the relationship
between vibrational anharmonicity and fragility. The density, the linear expansion coefficient, the longitudinal and transverse
ultrasonic velocities and their respective temperature coefficients of the velocities are measured, from which the vibrational
anharmonicity in lithium borate glasses is evaluated with the help of the Grneisen parameter at the Debye cut-off frequency
and the Anderson-Grneisen parameter: these two parameters plotted vs. composition have the same characteristics with minima at x≈0.08. The fragility is evaluated from the temperature width of the glass transition; the fragility also shows a minimum at
x≈0.08. The presence of minima at x≈0.08 is ascribable to the fact that the crosslinking density between six-membered rings in the glass reaches a maximum at
this composition. We show that the anharmonic parameters strongly correlate with the fragility metrics.
The calorimetric glass transition and dielectric dynamics of -relaxation in propylene glycol (PG) and its five oligomers (polypropylene glycol, PPG) have been investigated by the modulated differential scanning calorimetry (MDSC) and the broadband dielectric spectroscopy. From the temperature dependence of heat capacity of PPGs, it is clarified that the glass transition temperature (Tg) and the glass transition region are affected by the heating rate. The kinetic changes of PG and PPGs near Tg strongly depend on the underlying heating rate. With increasing the molecular mass of PPGs, the fragility derived from the relaxation time against temperature also increases. The PG monomer is stronger than its oligomers, PPGs, because of the larger number density of the —OH end group which tends to construct the intermolecular network structure. Adam-Gibbs (AG) theory could still hold for MDSC results due to the fact that the dielectric relaxation time can be related to the configurational entropy.
Authors:M. Takeda, M. Takahashi, K.-Y. Akiba, and S. Kojima
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.
Authors:Y. Matsuda, C. Matsui, Y. Ike, M. Kodama, and S. Kojima
heat capacity, Cp*=Cp'–iCp'',
of lithium borate glasses xLi2O(1–x)B2O3
(molar fraction x=0.00–0.30) has
been investigated by Modulated DSC. We have analyzed the shape of Cp*
by the Cole-Cole plot, performed fitting by the Havriliak-Negami equation,
and then determined the parameters related to the non-Debye nature of thermal
relaxation. Moreover, the concentration dependence of the thermal properties
has been investigated. Glass transition temperatures become higher with the
increase of molar fraction of Li2O and shows the board
peak around x=0.26. Temperature ranges
of glass transitions become narrower with the increase of Li2O
Authors:S. Kojima, T. Saito, J. Takada, M. Furukawa, H. Oda, T. Nakamura, and K. Yokota
Concentrations of eighteen trace elements at the sediment-water interface in Biwa Lake were determined by neutron activation analysis. Release of iron, manganese and arsenic from the sediment to the pore water was observed under anoxic conditions. The concentrations of Sb in the pore water as well as Na were nearly constant between the surface and the depth of 40 cm. The behavior of Sb differed from that of As at the sediment-water interface, since the partition coefficient of Sb differed from that of As.
Authors:T. Nakamura, S. Kojima, T. Ohta, M. Nishida, A. Rakowski, A. Ikeda, H. Oda, and E. Niu
14C variations of atmospheric CO2 as well as carbonaceous fraction of living materials, such as collagen from tooth and bone, tissue, skin, hair, nail, etc.,
of modern humans are influenced by 14C produced artificially by nuclear bomb tests in the atmosphere from late 1950s to early 1960s. By careful investigation of
14C concentration of tree rings and human body samples formed in this time intervals, we can establish a relationship of their
14C concentrations with calendar year. By applying this relation to a sample whose 14C concentration can be measured, we can estimate the formation age of the sample. In addition, sources of the chemicals that
were used in some criminal cases can be possibly identified, by their carbon isotope ratios (13C/12C and 14C/12C). This method of age determination has been applied to a forensic study, i.e., two criminal cases of murder. For each case,
by comparing the measured 14C abundances of several pieces of hair and one tooth (the third molar) from the body with the annual change on concentrations
of bomb-produced 14C, the time of death of the body and the age of the victim were estimated. The estimated values were consistent with the real
ones that were revealed by the confession of the real murderers.
Authors:T. Muroyama, A. Shinohara, T. Saito, A. Yokoyama, K. Takamiya, S. Morimoto, K. Nakanishi, H. Baba, T. Miura, Y. Hamajima, T. Kaneko, H. Muramatsu, S. Kojima, and M. Furukawa
Annihilation γ-rays of π0 and pionic X-rays were measured in the gas mixtures of H2+Z and CH4+Z systems (Z=He, Ne, Ar and Kr). Pion capture probability of hydrogen atom was obtained from the annihilation γ-ray counts
and the capture probability of Z atom was obtained from the pionic X-ray intensities. Transfer rates were determined from
the data based on a combined large mesomolecular model. The transfer rates obtained were smaller than the systematics of the
Russian group. Difference in the transfer rate between the gas and the liquid phases was found by a comparison of the present
results with our previous ones.
Authors:A. Shinohara, T. Muroyama, T. Miura, A. Yokoyama, K. Takamiya, T. Kaneko, T. Saito, J. Sanada, H. Araki, S. Kojima, Y. Hamajima, H. Muramatsu, H. Baba, and M. Furukawa
Pionic X-rays and π0 decays were measured for gas mixtures of H2/D2/CH4+SF6/Ar and the individual pure gases. Chemical effects on the pion transfer process from pionic hydrogen to other atoms were
revealed by the pionic X-ray spectrum. The changes of the intensity patterns of pionic X-rays were compared with the predictions
by a cascade calculation taking the transfer process into account. The mechanism of pion transfer process was discussed based
on the results for gas phase and the previous ones for liquid phase.