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  • Author or Editor: T. Nakanishi x
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Abstract  

To understand how nutrients are recycled in a particular soil - plant system, we have analyzed the kinetics of the elements Na, Mg, K, Ca, Mn, and Br throughout the life cycle of the plant. The plant sample was collected at 6 different stages of its growth. The effect of V (100 µM) on the element recycling system was also analyzed. The amount of the elements in each tissue of the plant, root, stem, petiole, leaf, and seed, were then determined by neutron activation analysis. The total elemental uptake rapidly increased when the plant developed from the juvenile to the adult phase. More than half of the Mg and Mn in cotyledon was transported to the younger leaves before the cotyledon was shed. From the pattern of movement of each element in plant tissue we have constructed an element recycling model in the soil-plant system. Based on the model, it was found that the amount of K to be a limiting factor for the recycling activity in the system.

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Abstract  

Polonium-210 in phosphoric acid has been recognized as a significant source of alpha contamination of processed Si-wafers for memory devices of computer. In the present work, a convenient method was developed for the determination of trace210Po in phosphoric acid of high purity. For the determination,209Po was used as a yield tracer. The present method consists of (1) addition of the tracer to 5 ml aliquot of phosphoric acid sample, (2) pH adjustment (to 2) of the sample solution to make up electrolytic solution, (3) electrodeposition for the simultaneous achievement of Po separation and preparation of counting source on stainless-steel disc, and (4) alpha-ray spectrometry. By the developed method, more than 95% of Po was separated from phosphoric acid sample onto counting disc. The minimum detectable radioactivity of210Po in 5 ml of phosphoric acid was about 0.03 mBq by counting the electrodeposited alpha-activity for 10 days under a counting efficiency of ≈30%.

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Abstract  

Transition elements, Sc, V, Cr, Mn, Fe, Co and Zn, as well as Al concentrations in all tissues of the morning-glory (Ipomoea nil L. c.v. Murasaki) with developing seed were analyzed by instrumental neutron activation analysis. Aluminum as well as most of the transition elements were found to be accumulated in the root. Only small amounts of the elements were accumulated in the upper part of the plant, except for Cr and Mn. However, when the elements at the upper part of the plant were analyzed, the highest concentration of Al, Sc, V, Fe and Zn were shown to be at the tip of the eldest leaf and cotyledon. In the case of Co, the elemental concentration was high in the lower stems, suggesting a barrier to transfer of the element to the leaf from the stem. A barrier of the element movement from leaf petiole to the leaf was not found in most of the elements investigated. In the ripening stage of the seed, highly selective elemental concentrations in seed were found.

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Summary  

A portable liquid scintillation counter was applied for the analysis of alpha-ray energy spectrum to determine the ratio of 220Rn/222Rn in fumarolic gas in the field. A surface-polished vial was developed, by which a Gaussian distribution could be approximated for the alpha-ray energy spectra and the peak areas of the nuclides could be estimated independently, because of the wide FWHM in the liquid scientillation pulse. A fumarolic gas sample was collected in Mt. Kamiyama (Hakoneyama geothermal field in Japan) having low 220Rn/222Rn ratio of 2.20±0.13.

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Abstract  

Mössbauer spectroscopy was applied to an investigation of ancient iron slags, excavated at the ancient ruins for iron manufacturing in order to deduce the raw materials and operative conditions of the furnace. From the Mössbauer spectra, it was found that the slags consisted of fayalite, wüstite, ulvöspinel and magnetite.

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Abstract  

The growing up of the fine particles in a sapphire crystal was simulated with a computer and the expected Mössbauer spectra were calculated by considering the influence of the nearest neighbors and next-nearest neighbors to the magnetic hyperfine field of the iron atoms. The simulated spectra were compared with the Mössbauer spectra observed with a Fe-implanted sapphire and the agreement between them was satisfactory on the whole. It is also revealed that an iron atom implanted into a sapphire crystal may interact, before coming to rest, with the iron fine particles situated within 2–3 nm in the crystal.

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Abstract  

For an investigation of the ancient iron manufacturing technique, a modern simulation experiment was carried out. The smelting furnaces were built with clay. Charcoal and raw materials were installed from the top of the furnace. Magnetite was used as the raw material. In the furnace, iron oxide was reduced to metallic iron. The reduction reaction was mainly controlled by temperature and oxygen fugacity in the furnace. In order to investigate the possibility for the estimation of these parameters, 57Fe Mössbauer spectra were recorded of the furnace wall at room temperature.

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Abstract  

Seven representative wood species constituting caatinger forest were chosen to analyze Sc, V, Cr, Mn, Fe and Co, as well as Na, Mg and Al, by instrumental neutron activation analysis. In most cases of the soil, the concentration of the element tended to be higher with the increase of depth. Generally, the element partition from soil to root was higher in Mg and Co, whereas V showed higher partition rate from root to bark. The correlation within the elements was higher in the order of soil, root and bark.

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Abstract  

Elemental concentration in each tissue of Japanese morning-glory (Pharbitis nil) during the growth was analyzed by INAA. Plants were grown in water culture for 4 days under 12-hour light and 12-hour dark condition. During the growth, 10 plants in the same developmental stage were periodically harvested. Then the plants were separated into 9 tissues to determine elemental concentration and water content. There was an elemental specific profile within the plant tissue, for example, Na and K concentrations were high in root whereas Mg and Ca concentrations were high at the upper part of the plants. Among the elements studied, Ca and Mg showed rhythmical change in concentration, increased during the day and decreased during the night. This tendency was especially noted at shoot apex. However, water content in all of the tissue was increased about 6 hours prior to the light period and showed maximum in the middle of the light period. About 6 hour difference of water content movement to those of Ca and Mg concentration suggested that water movement drives more dynamic change of each elemental concentration within a plant.

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