Search Results

You are looking at 1 - 10 of 25 items for

  • Author or Editor: S. Yoshida x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

The phase transition and nano-scale ordered structure of four types of blends prepared from four di-block copolymers, consisting of hydrophilic poly(ethylenoxide) and hydrophobic poly(methacrylate) derivative, PEOm-b-PMA(Az)n having different PEO molecular length and same degree of polymerization of PMA(Az) were investigated. All blend systems formed hexagonal packed PEO cylinder structure, which was same with the nano-scale structure of these parent block copolymers. The SAXS and AFM observation suggested that the size of hexagonal structure of blend was larger than the average size of parent block copolymers. The melting enthalpy of PEO in blends was larger than the average value of parent block copolymers. DSC, SAXS and AFM observations indicated the miscible blend systems.

Restricted access

Abstract  

In order to assess the levels and behavior of129I (half-life: 1.6×107 y) and127I (stable) in the environment, we have developed analytical procedures involving neutron activation analysis (NAA). Environmental samples collected around Tokaimura, Ibaraki Prefecture, Japan, have been analyzed using this method. Ranges of129I and127I concentrations in surface soil were 0.9–180 mBq kg–1 and 1–60 mg kg–1, respectively. Higher129I concentrations were found in soil samples collected from coniferous forests, suggesting a contribution from tree canopies in the deposition of this nuclide. Most of the129I in soil, was found to be retained in the first 10 cm. The129I/127I ratios in wheat fields were lower than those in rice paddy fields.A soil sample collected by IAEA from an area contaminated by the Chemobyl accident was also determined. The129I concentration and the129I/127I ratio were 1.6 mBq kg–1 and 1.7×10–7, respectively. The129I level in this sample was higher than the values obtained in areas far from nuclear facilities in Japan. It was suggested that the analysis of129I in soils in the Chernobyl area may be useful in evaluating the131I levels at the time of the accident.Analyses of129I and127I by ICP-MS in water samples were also made. The analytical speed of this method was very high, i.e., 3 minutes for a sample. However, there is a sensitivity limitation for129I detection due to interference from129Xe with the129I peak. The detection limits for129I and127I in water samples were about 0.5 mBq ml–1 and 0.1 ng ml–1, respectively.

Restricted access

Abstract  

A simple pre-irradiation procedure for the separation of iodine from soil has been developed. A soil sample was heated in a quartz tube for 15 min at about 900 °C. The evaporated iodine was collected in activated charcoal, which was produced from phenol resin with low impurities. The charcoal, with sorbed iodine, was irradiated by neutrons and the128I produced was measured. A successful elimination of the background radioactivity due to the matrix elements was possible with this separation procedure. The detection limit by this method for soil samples was about 0.1 mg/kg (dry). The method has been applied to analyze selected soil samples.

Restricted access

Abstract  

Monolayers of amphiphilic di-block copolymer, PEO40-b-PMA(Az)19 on water surface and solid surfaces, such as silicon wafer and quartz glass, were analyzed by surface pressure — molecular area (π-A) isotherm, UV-Vis spectroscopy, atomic force microscopy (AFM) and total X-ray reflectivity (TXR). The monolayer prepared at 22 mN m-1 consisted of H aggregated azobezene (Az) moieties, which orientated perpendicular to the solid surface. The monolayer structure, including H aggregated Az and orientation of Az, was stable after annealing at 98�C, at which temperature the hydrophilic PEO domain was the liquid phase and the hydrophobic PMA(Az) was in the smectic A phase.

Restricted access

Abstract  

A reliable method for the sampling and analysis of atmospheric iodine species was developed. The air filtering system consisted of a 0.4 m Nuclepore® filter, 47 mm in diameter, for particulate collection followed by two, 47 mm in diameter, cellulose filters for inorganic iodine collection. The latter filters had been impregnated with 1N LiOH in a 10% glycerol-water mixture. The organic iodine was collected by two beds holding 0.2 g of fibriform activated charcoal produced from phenol resin. Supplementation of the charcoal with triethylendiamine (TEDA) enhanced the sorption ability for gaseous iodine. The filters were analyzed by neutron activation analysis. The background radioactivity could be reduced by using the fibriform activated charcoal due to the low content of impurities in the phenol resin. The background count for128I (443 keV) obtained from the fibriform activated charcoal was about one order of magnitude lower than that of the conventional granular one (plant origin). Approximate detection limits for particulate, inorganic and organic iodine were 1, 0.5 and 0.5 ng/m3, respectively, when 50 m3 of air was sampled by this system. The air was sampled at two locations along the coast of Ibaraki, Japan. The concentration ranges of particulate, inorganic and organic iodine were 0.3–3.4, 1.2–3.3 and 7.8–20.4 ng/m3, respectively. Almost 90% of the atmospheric iodine was in a gaseous form in which organic iodine was dominant.

Restricted access

Abstract  

In order to obtain information on the behavior of long-lived129I in the soil-plant-atmosphere system, two different experiments, transfer factors and volatilization of iodine, have been conducted by radiotracer techniques using125I. Soil-to-plant transfer factors varied very widely. Low values were found in tomato (0.0003) and rice (0.0019). The highest value for an edible part was seen in komatsuna,Brassica rapa L. (0.016), which is comparable to the IAEA recommended value of iodine for common crops (0.02). There was a tendency for older leaves to show higher concentrations than younger ones. The values for fruit, grain and beans were significantly lower than those for their leaves. Thus translocation of iodine with photosynthate from leaves into these plant organs was very small. Iodine in soil was found to be volatilized from the soil-rice plant system into the atmosphere as an organic iodine. Volatilization markedly decreased in the late cultivation period of rice plants.

Restricted access

Abstract  

High resolution-type ICP-MS was applied to the analysis of 239Pu and 240Pu in soil samples. The detection limit of Pu was about 0.001 pg.ml-1 (ppt) in the sample solution or about 0.0005 pg in a total sample. This method was used to determine concentrations of Pu and its isotopic ratios in several soil samples collected from different areas in Japan. Concentrations of Pu in surface soils collected from forests were significantly higher than those in soils from agricultural fields. The 240Pu/239Pu atom ratios observed were usually 0.17-0.19, except for one very low ratio (0.037) found in the Nishiyama area (Nagasaki).

Restricted access

Abstract  

The concept of crystallization dynamics method evaluating the miscibility of binary blend system including crystalline component was proposed. Three characteristic rates, nucleation, crystal growth rates (N*, G*) and growth rate of conformation (G c*) were used to evaluate the miscibility of PVDF/at-PMMA and PVDF/iso-PMMA by the simultaneous DSC-FTIR. N*, G* and G c* depended remarkably on both temperature and blend fraction (ϕPMMA) for PVDF/at-PMMA system, which indicated the miscible system. PVDF/iso-PMMA showed small ϕPMMA dependency of N*, G* and G c*, was estimated the immiscible system. The ΔT/T m 0 values, corresponding to Gibbs energy required to attend the constant G* and G c*, evaluated from G* and G c* showed the good linear relationships with different slope. The experimental results suggested that the concentration fluctuation existed in PVDF/iso-PMMA system.

Restricted access

Abstract  

An online analytical system using ion chromatography (IC) followed by inductively coupled plasma mass spectrometry (ICP-MS) was developed for the separate determination of I and IO3 in aqueous solutions with a detection limit 0.1–1 μg 1/1. The total iodine concentration was also directly determined by ICP-MS. Iodine in several environmental samples (i.e., rain, river water, brine, and soil solution) was successfully determined with information on its chemical form. The release of I into soil solution with decreasing Eh was observed in an incubation experiment with flooded soil. An iodine form other than I and IO3 was observed in several environmental samples.

Restricted access

Abstract  

A rapid separation method was developed for determination of low level promethium-147 and samarium-151. The rapid method, applied to environmental samples, provided speed and efficiency for the respective separation of Pm and Sm from other lanthanides with the simplified technique of high performance liquid chromatography (HPLC) system. The separation time of Pm and Sm in HPLC separation was shortened by stepwise eluent method of -hydroxyisobutyric acid as compared with a gradient eluent method of lactic acid with HPLC despite increase in sample volume for significant determination of Pm-147 and Sm-151. This method permitted the detection limit around 0.1 Bq/kg-dry-soil for Pm-147 and Sm-151 in 200 g soil sample by counting for 500 min with a liquid scintillation counter.

Restricted access