Concentrations of arsenic and bromine dissolved in hot spring waters have been determined by neutron activation analysis using 0.5 cm3 of sample waters without any chemical pretreatment. The samples prepared for neutron irradiation were simply pieces of filter papers which were infiltrated with samples. With the results of satisfactorily high accuracy and precision, this analytical method was found to be very convenient for the determinations of arsenic and bromine dissolved in water at ppm to sub-ppm levels.
Authors:G. Zhang, T. Kitamura, H. Yoshida, and T. Kawai
The simultaneous DSC-FTIR was used for the observation of crystallization and melting of poly(vinylidene fluoride) (PVDF)
and its blends with poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA). The isothermal crystallization was
carried out under the condition of both α-form and γ-form crystallized competitively. The crystal growth rate of α -form and
γ -form were evaluated from the absorbance changes at 795 cm-1 (α -form, CH2 rocking) and 810 cm-1 (γ -form, CH2 rocking) obtained by the DSC-FTIR. The crystal growth rate of γ -form decreased at the same crystallization temperature in
the order of PVDF/syn-PMMA, PVDF/PEMA and PVDF/at-PMMA, which was corresponding to the order of interaction parameter. The mechanism of α -g transition of PVDF in the miscible
blends with at-PMMA, syn-PMMA and PEMA was evaluated from the relationship between the decrease of α -form and the increase of γ -form. The critical
crystallization temperature, at which the transformation from α -form to γ -form proceeded only in the solid state, shifted
to higher temperature side in the order of interaction parameter.
Authors:H. Yoshida, G. Zhang, T. Kitamura, and T. Kawai
The mixing state of poly(vinylidene fluoride) (PVDF) and two amorphous polymers,poly(methyl methacrylate) (PMMA) and poly(isopropyl
methacrylate) (PiPMA) were investigated from the viewpoint of crystallization dynamics using simultaneous DSC-FTIR method.
The crystallization rate (R*) and the growth rate of trans-gauche-trans-gauche’ (TGTG’) conformation (Rc*) depended on both the blend content (ϕ) and the crystallization temperature for PVDF/PMMA. The temperature and ϕ dependency
of R* and Rc* were almost the same for PVDF/PMMA. However, R* and Rc* depended scarcely on f for PVDF/PiPMA, and the temperature dependency of R* differed from that of Rc* for PVDF/PiPMA. These results showed that PVDF and PMMA were miscible on molecular level, and that PVDF/PiPMA was immiscible
and the concentration fluctuation existed in the PVDF-rich phase.
Authors:T. Watanabe, G. Zhang, H. Yoshida, and T. Kawai
The miscibility of crystalline syndiotactic polystyrene (SPS)/non-crystalline atactic polystyrene (APS) blend was estimated
by the crystallization dynamics method, which evaluated the nucleation rate, the crystal growth rate and the surface free
energy parameter. The melting temperature depression suggested that SPS/APS blends were the miscible system but not in molecular
level. The relationship between the blend content and the chemical potential difference evaluated at a constant crystal growth
rate showed a good linear relationship. These facts suggested that SPS/APS blends contained the concentration fluctuation
with the size between few nm to less than 80 nm.
Authors:M. Akaboshi, K. Kawai, Y. Tanaka, J. Takada, and T. Sumino
The effect of hyperthermia on the cell killing efficiency of Pt atoms binding to DNA, RNA and protein molecules of HeLa cells
treated withcis-diamine(1,1-cyclobutanedicarboxylato)platinum(II) (CBDCA) was examined. HeLa S-3 cells were treated with195mPt-radiolabeled CBDCA for 60 minutes at various temperatures, and the relationship between the lethal effect and the number
of Pt atoms binding to DNA, RNA and proteins was examined. The mean lethal concentration (D0) of carboplatin for a 60 min-treatment at 0, 25, 37, 40, 42 and 44°C was 671.2, 201.5, 67.3, 33.4, 20.2 and 15.6 μM, respectively.
By using identically treated cells, the number of Pt-atoms combined with DNA, RNA and protein molecules were determined in
the subcellular fractions. Thus, the D0's given as the drug concentrations were replaced with the number of Pt-atoms combined in each fraction. Then, the cell-killing
efficiency of the Pt atom was expressed as the reciprocal of the number of Pt-atoms combined and was calculated for each molecule.
The efficiency for DNA molecules was 0.699, 1.42, 2.65, 4.84, 7.74 and 8.28·104 nucleotides, respectively, for the conditions described above. From 0 to 44°C, the cell-killing efficiency of Pt atoms increased
by a factor of 11.9.
Authors:M. Akaboshi, Y. Tanaka, T. Sumino, J. Takada, and K. Kawai
The literature indicates that the interaction of Tb3+ with DNA modified by the antitumour drug cis-diaminedichloroplatinum(II) (CDDP) results in substantial enhancement of the
fluorescence of this cation, while no enhancement is observed in the case of DNA modified by irradiation with ionizing radiation.
This study investigates the effect of Tb3+ on the survival of cultured mammalian cells treated with CDDP. HeLa cells were treated with a combination of195mPt-CDDP and TbCl3, and the relationship between lethal effect and the numbers of Tb and/or Pt atoms binding to DNA, RNA and proteins was examined.
The Tb content in each fraction was determined using instrumental neutron activation analysis. It was found that the cytotoxic
effect of CDDP was greatly enhanced by the presence of Tb ions (D0 of CDDP fell from 8.3 μM without Tb to 3.2 μM with 0.75 mM Tb), while no such effect was found in radiation-induced cell-killing.
The number of Tb atoms bound to DNA molecules in a cell was calculated to be about 4.5·107, namely 1 per 1.400 nucleotides, under that situation.
Authors:Y. Tanaka, T. Sumino, K. Kawai, J. Takada, K. Kawamoto, and M. Akaboshi
The enhancement of cell-killing effect induced by60Co γ-rays on the aqueous solutions of potassium hexachloroplatinum(IV) (K2PtCl6) irradiated in the presence of various concentrations of NH4Cl was examined. HeLa S-3 cells were treated with the irradiated solutions for 60 minutes at 37°C, and cell survival was measured
by colony forming efficiency. The mean lethal concentration (D0) for the cells treated with non-irradiated K2PtCl6 solution (1 mg/ml) was 34.5 μl/ml. However, it decreased, namely the cell-killing effect of the solution increased with increasing
radiation dose up to 2.64·104 Gy in the case of 0.1M NH4Cl solution (in this condition, theD0 decreased to 9.6 μl/ml). No or only a slight enhancement was observed in the case of K2PtCl6 solutions irradiated in the presence of NaCl, (NH4)2HPO4, ammonium acetate or glycine. Observations using high performance liquid chromatography (HPLC) of irradiated K2PtCl6 solutions revealed the formation of cis- and/or trans-diaminedichloroplatinum (IV) (DDPs(IV)). However, the observed cell-killing
action of the solution was too high to be explained by the amount of both the DDPs(IV) formed by γ-rays.
Authors:T. Aze, M. Fujimura, H. Matsumura, K. Masumoto, N. Nakao, H. Matsuzaki, H. Nagai, and M. Kawai
In order to estimate the total radioactivity induced in a concrete shield by thermal neutron-capture reactions at high-energy
accelerator facilities, the observed activity of 36Cl in the concrete is expected to serve as an indicator of the thermal neutron fluence. Since 36Cl can also be produced from K and Ca by spallation reactions, we measured these production rates in order to clarify the
contribution of each reaction. The Cl, K, and Ca targets were irradiated with neutrons having a maximum energy of 500 MeV.
As a result, the production rates of 36Cl from Cl were only two orders higher than those from K and Ca. It was found that the 36Cl production ratios from Cl, K, and Ca were 6.7%, 6.8%, and 86.5%, respectively, and Ca was the main source of 36Cl production.
Authors:M. Akaboshi, T. Sumino, Y. Tanaka, J. Takada, K. Kawai, and K. Kawamoto
HeLa S-3 cells were treated with several rare earth elements, Ce, La, and Sm, at 37 °C for 1 hour and the relationship between the lethal effects of these elements and the number of the atoms bound to DNA, RNA, and proteins was examined. Among the 3 element, only Ce gave an exponential dose-survival relationship from which the value of mean lethal concentration (D0) was determined to be 6.75 mM. By using identically treated cells, the number of Ce atoms combined with DNA, RNA and protein molecules in HeLa cells were determined after fractionation of the cells using neutron activation analysis. In this way, theD0 value given as the Ce concentration was replaced by the number of Ce atoms combined with each fraction, then the target volumes, viz., cell killing efficiency, expressed as the reciprocal ofD0 value was calculated for each fraction. The results suggested that DNA and RNA could stochiometrically be the primary target molecule for cell killing by Ce.
Authors:R. Suzuki, T. Ohdaira, K. Yamada, T. Yamazaki, N. Sei, T. Mikado, T. Noguchi, H. Ohgaki, S. Sugiyama, M. Chiwaki, T. Shimizu, M. Kawai, M. Yokoyama, S. Hamada, K. Saeki, N. Nishimura, and T. Tomimasu
A positron lifetime study has been done on dielectric multilayer cavity mirrors for free-electron-laser experiments by the use of a variable-energy pulsed positron beam. A long-lived ortho-positronium component has been observed at low positron energy region, corresponding to the depth of the top amorphous SiO2 layer. The intensity of the positronium component correlates with the degradation and restoration of the mirrors. We discuss the relation between the positronium intensity and degradation mechanism of the mirrors. The present studies revealed that the slow positron lifetime technique is highly sensitive to the properties of the mirrors and is useful for the evaluation of the mirrors.