Search Results

You are looking at 1 - 8 of 8 items for

  • Author or Editor: K. Nishimura x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

The lanthanides (REEs) in 142 fern leaves collected from 9 sampling sites in Japan were analyzed by instrumental neutron activation analysis. Between two REEs a strong positive correlation was found in the logarithmic scattering diagram with correlation and regression coefficients close to unity, suggesting neither selective accumulation by plants nor different availability from soil between the two elements. However, between Tb and the other REEs the relationship showed two lines with the same correlation coefficient. This suggested that there must be a difference in the availability of REEs or in their absorption characteristics by plants. Further analysis revealed that the splitting was due to some difference in the environmental factors where the fern grew. However, the amount of REE in the soil collected together with the corresponding fern did not reflect the REE concentration in the fern leaves.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: M Yasuoka, Y Nishimura, T Nagaoka, and K Watari

Abstract  

The ceramic industry uses enormous amounts of energy to produce products at high temperatures. Energy-saving measures based on sintering process improvements are examined. Oxide ceramics were irradiated by two different methods during microwave sintering: intermittent use of the same high power levels (time-control method) and continuous use of lower, increasing levels of power (power-control method). We found that: 1) the power consumption and efficiency of the time-control method were lower than those of the power-control method; 2) the power-control method gave more precise control of temperature under our experimental conditions; 3) sample densification did not differ greatly between the two methods; and 4) grain growth did not differ greatly between the two methods.

Restricted access

Abstract  

The lanthanides (REE) in 142 fern leaves collected from several sampling sites in Japan have been determined by neutron activation analysis, and the correlations between any two REEs in the logarithmic scattering diagram were examined. The relationship was expressed by the general formula, Y=aX+b with a correlation coefficient R. A strong positive correlation was seen between any two REEs in the diagram with a regression coefficient and a correlation coefficient close to unity. However, between Eu or Tb and other REEs the relationship was split into two lines with the same correlation coefficient. From the intercept b, the relative abundance of the two elements was determined for each REE and compared with those in hickory and tobacco leaves. These findings indicated that the abundance pattern of fern leaves is quite different from those of hickory and tobacco leaves. Namely, the relative abundance of La and Ce was quite similar in the three plants, but the abundance of the other REEs (Nd, Sm, Gd, Dy and Lu) was considerably lower in ferns than in hickory and tobacco leaves. For Eu and Tb the higher values obtained in fern leaves coincided with those of the two plants.

Restricted access

Abstract  

We have investigated the concentrations of REEs in fern leaves collected indifferently to the fern species from 9 sampling sites in Japan using INAA. The results indicated a large variation in the values obtained between fern leaves. In the present investigation we applied the same analytical method on the samples (Blechnaceae, a kind of fern, mature and developing leaves were collected from the same plant) restrictively gathered from the University Forests in Ashiu, Kyoto University. It was demonstrated that the variations in the REE concentrations decreased by one to two order of magnitude, and that the REE contents in developing leaves were also one to two orders of magnitude lower than those in mature leaves. It can be considered that fern accumulates REEs with their growth stages.

Restricted access

Abstract  

Since the rare earth elements (REE) are most informative as isomorphic replacements of Ca2+ in organisms, we analyzed these elements in 142 fern leaves collected from several sampling sites in Japan by instrumental neutron activation analysis (INAA), and the correlation between the REE and Ca contents was examined. In most cases, between any particular REE and the Ca contents, the correlation in the logarithmic scattering diagram was expressed as a single line parallel to the vertical (Y) axis. However, the detailed analysis of the diagrams characterized with respect to the sampling site revealed that the 142 ferns could be separated into two or three groups on the basis of their different REE/Ca ratios. The sampling sites where the different REE/Ca ratios were observed completely agreed with those found in the preceding report, i.e., regarding the unusual correlation between Eu and the other REEs.

Restricted access

Abstract  

Content of 40 elements in plant leaves, soils and rocks collected from several sampling sites in Okayama Prefecture was analyzed by instrumental neutron activation analysis using the Research Reactor of Kyoto University. Of these, 16 elements were taken up, and the relationship among their amounts in plants, rocks and soils was discussed, focusing mainly on the essential elements of higher plants and related elements in the periodic table. Although most element contents in plant were different among species, the mediam values of the most non-essential elements in the leaf were lower than the contents in the soil and rock samples. However, essential elements showed significantly higher median values than those in the soil and rock samples. Most element contents in leaves showed a logarithmic normal distribution. The normal distribution was observed in most essential elements except for zinc, while non-essential elements did not show a normal distribution. The results obtained by analysis of variance, showed that the plant species studied could be divided into four major groups, namelyDicotyledoneae, Monocotyledoneae, Gymnospermae andPteridophyta. In general,Dycotyledoneae andPteridophyta had higher element contents thanMonocotyledonaeae andGymnospermae.

Restricted access

Abstract  

Boron concentration of plasma, feces, urine and body tissues from sheep fed with borated water (100 mg B/l) and tap water were determined by neutron-induced prompt gamma-ray analysis to elucidate boron metabolism. The B level in plasma and urine increased rapidly and the B content of feces increased greatly. The B concentrations in body tissues (liver, kidney, spleen, thyroid and muscle) of B dosed sheep were ten times higher than those of tap water administered sheep.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
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

Abstract  

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.

Restricted access