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1. Application of Laser Isotopic Spectroscopy of CO2 to Analysis of Carbon Cycle in a Forest


2. Development of Strontium Isotope Analysis in Bones for Research on Ancient Migration Route


3. Study on Interaction between Isotope Water and Metal in vivo


4. Development of Imaging System for 90Y Lymph Nodes Using an Imaging Plate

 


1. Application of Laser Isotopic Spectroscopy of CO2 to Analysis of Carbon Cycle in a Forest


Needs from Environmental Studies:
Isotopic ratio analysis is a useful measure for a quantitative research on behavior of environmental substances. The researchers of Environment & life sciences section adopt it to our study on carbon cycle in a forest, since carbon isotopic composition of CO2 and organic carbon in a forest varies with their transfer between carbon inventories in a forest as illustrated in Fig.1. Development of a new isotopic measurement technique with higher portability and with no requirement of complicate sample preparation must bring new horizon to environmental studies. It would enable more frequent and concentrated measurement, and consequently more accurate and more representative analysis of non-uniform, non-steady and highly complex environmental phenomena. The measurement would be undergone not only in a laboratory but also on an observation site.

carbon cycle in a forest

Fig.1 Schematic diagram of carbon cycle in a forest. The processes drawn with red arrows lead major isotopic fractionation.

Seeds by Isotopic Measurement Techniques:
The researchers of Isotope Measurement Section have developed a technique of Continuous Wave semiconductor laser Cavity Ring-Down Spectroscopy (CW-CRDS), and its high sensitivity and availability to distinguish and quantitative amounts of molecules with different isotopes has been proofed. Since the principle of CW-CRDS method, shown in Fig.2, requires simpler composition of the instrument without high vacuum system, downsized and portable system is expected to be achievable. Since the CW-CRDS measures the amounts of subject isotopic gases in mixture of other chemical spices, it is expected to need no extensive preparation and consequently to achieve rapid processing of the preparation.

Schematic diagram of CW-CRDS
Fig.2 Schematic diagram of CW-CRDS.

Progressive Cooperative Study: Needs meet Seeds
The researchers of two Sections have joined to start a Progressive Crossover Study which aims the achievement of high sensitive and highly concentrated observation by development of the technique of CW-CDRS for analysis of behavior of CO2 in a forest ecosystem. Following development has been undergone:

  • High sensitivity enough to carbon isotopic analysis of CO2 in air and soil gas of a forest
  • Downsizing and improvement of the portability of the instrument
  • Simple and rapid preparation technique to inject environmental air samples into the CW-CRDS instrument

The laser source has been changed to optimize wavelength of absorption lines. And a prototype instrument has been manufactured. We made mode matching between the laser beam and the "ring-down" optical cavity, and also redesigned a scanning device for a cavity mirror. As shown in Fig.3, 13C16O2 absorption spectra corresponding to partial pressures of CO2 in the "ring-down" cavity have been obtained, and the lower detection limit of CO2 mixing ratio has been evaluated to be 0.17 %. These progress suggests that CW-CRDS system based on 2.0 μm diode laser would be able to measure stable isotopic ratio (δ13C) of "5 % CO2 in air with 1 ‰ precision if fast data processing is achieved. This means the possibility of measurement and analysis of δ13C of CO2 in soil gas in a forest.

CO2 absorption spectra

Fig.3 Examples of 13C16O2 absorption spectra for some partial pressures of CO2 in the "ring-down" cavity.

[Published papers]

  1. H. Tomita, K. Watanabe, Y. Takiguchi, J. Kawarabayashi, T. Iguchi, "Rapid-swept CW cavity ring-down laser spectroscopy for carbon isotope analysis." J. Nucl. Sci. Technol. 43 (4) (2006) 311-315.

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2. Development of Strontium Isotope Analysis in Bones for Research on Ancient Migration Route


Strontium isotope ratios in an individual's bone and teeth directly reflect the isotopic ratios found in the plants and animals that she or he consumed, which reflect the isotope ratios found in the soil and bedrock of that geologic region. Strontium isotope analysis for archaeological fossil bones and teeth could address human residential mobility and ancient trade network.

Conceptual diagram of Sr analysis

Fig.4 Conceptual diagram of Strontium isotope analysis in bones for research on ancient migration route.

In this study, we will establish the method of precise and accurate measurement of strontium isotopic ratios for historical bone samples without decomposition using laser ablation assisted Resonance Ionization Mass Spectrometry (LA-RIMS).

Application of the 87Sr/86Sr ratio of an individual's bone to its provenance determination
To evaluate whether the 87Sr/86Sr ratio of bone reflects the isotopic ratios found in the soil and bedrock of that geologic region, two bone samples and the geological samples in their provenance area were measured for 87Sr/86Sr ratios by the Thermal Ionization Mass Spectrometry (TIMS).

Sr ratios of black bass bone

Fig.5 87Sr/86Sr ratios of a black bass bone and surface water at the southern basin in Lake Biwa, Shiga prefecture.

Sr ratios of boar bone

Fig.6 87Sr/86Sr ratios of a boar bone and a stream sediment collected at Asuke, Toyota City, Aichi prefecture.

The similar 87Sr/86Sr ratios between bone and its provenance geology indicate that the 87Sr/86Sr ratios of bones reflect the isotopic ratios of the birth and growth places.

Comparison of the values of 87Sr/86Sr ratios measured by ICP-MS and TIMS
Comparison of the values of 87Sr/86Sr ratios measured by LA-RIMS with those of ICP-MS and TIMS with those by LA-RIMS could evaluate analysis efficiency of LA-RIMS. Prior to the comparison, accuracy of the ICP-MS and TIMS methods was examined. The values of 87Sr/86Sr ratios measured by ICP-MS were similar with those by TIMS, suggesting that accurate and precise values can be obtained by each method.

Foundational Research for Strontium Isotope Analysis of Bones by LA-RIMS
The LA-RIMS spectrum directly obtained from the bone sample collected at Asuke, Toyota City, Aichi prefecture is shown in Fig.7. The isotope ratio 87Sr/86Sr was estimated to be 0.658±0.004 (0.6 %) by accumulating peak areas of spectrums. The value of 87Sr/86Sr was not agreement with the TIMS value 0.71001, and shifts systematically. However, the precision of 0.6% obtained in this study achieved the required precision for the provenance determination. The result shows possibility to identify areas of an individual's birth and growth from strontium isotope analysis of bones using LA-RIMS.

LA-RIMS Sr isotopes spectrum
Fig.7 LA-RIMS spectrum of strontium obtained from the boar bone collected at Asuke.

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3. Study on Interaction between Isotope Water and Metal in vivo


Research of Sulfurization Reaction of Hemoglobin in Environment of Isotope Water Molecule
Figure 8 shows photographic views of the prepared samples. Left samples, enclosing with a blue square, were adjusted to D2O. Right ones, enclosing with a yellow square, were adjusted to H2O. Continuously, a bubbling by the carbon monoxide or the hydrogen sulfide was done to each left or right sample, respectively. Only the rightmost sample changes from clear red to dark brown, and the color variations are not admitted in other samples.

Sulfurization Reaction of Hemoglobin
Fig.8 Photographic views of the prepared samples.

Table1 is a result of ICP-Mass measurements for the samples of hemoglobin with D2O. Hb-CO and Hb-Sulfur mean the bubbling samples with carbon monoxide and hydrogen sulfide, respectively. We have obtained the result that the sulfur atoms are extremely increasing in Hb-Sulfur sample. This result is corresponding to the sulfur K-edge NEXAFS results.

Figure 9 shows the sulfur K-edge NEXAFS spectra of the same samples as ICP-Mass measurements. The edge-jump value, which is shown in the figure by the blue and red arrows, suggests the amount of sulfur atoms. It is found that the amount of sulfur atoms of Hb-Sulfur is about two times in comparison with Hb-CO. This result is approximately corresponding with the ICP-Mass. It seems that the observed peak at 2472 eV is assigned to the chemical bond between atomic sulfur and iron atom inside of the hemoglobin.

Table1 Result of ICP-Mass measurements for the samples of hemoglobin with D2O.
Wave length(Å) Hh-CO Hh-Sulfur Detection lim.
S 1820 536 918 1
Fe 2599 297 271 0.2
Na 5889 83.5 85.2 0.9
Zn 2138 4.50 3.90 0.03

Sulfur K-edge NEXAFS spectra
Fig.9 Sulfur K-edge NEXAFS spectra of the samples of hemoglobin with D2O.

[Published papers]
  1. Shinya Yagi, Toyokazu Nomoto, Takaki Ashida, Kazuya Miura, Kazuo Soda, Kazue Yamagishi, Noriyasu Hosoya, Ghalif Kutluk, Hirofumi Namatame and Masaki Taniguchi, "XAFS Measurement System for Nano, Bio and Catalytic Materials in Soft X-ray Energy Region", Proceedings of SRI-2006, American Institute of Physics 879 (2006) 1638-1641.
  2. Yagi, S. Matsumura, Y. Soda, K. Hashimoto, E. Taniguchi, M., "Interface Study for Liquid-Solid State Surface by means of S K-edge NEXAFS Method", Surface and Interface Analysis, 36 (2004) 1064-1067.

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4. Development of Imaging System for 90Y Lymph Nodes Using an Imaging Plate


Feasibility of 90Y Lymph Nodes Imaging Using the IP System

Y-90線源の画像化
Fig.10 Images of an 90Y point source after passing through from 1mm to 12mm acrylic plates were obtained by using the IP system.

The IP system is applicable for obtaining 90Y images in lymph nodes distributed from the body surface to 12mm in depth.

Improvement of 90Y Image

The PIXON method was applied to the 125I thyroid image obtained by the system without a collimator. The shape of the 125I thyroid was clearly displayed by distinguishing between signal and noise.

125I thyroid images
Fig.11 125I thyroid images.

We are now applying the PIXON method to 90Y point source images in order to improve 90Y lymph node images obtained with IP.

[Published papers]
  1. Shigeki Ito, Takuya Saze, Kunihide Nishizawa, Thyroid 123I imaging system using an imaging plate. Radiation Safety Management, Vol. 4, No. 1, 1-10, 2005.
  2. Shigeki Ito, Takuya Saze, Kunihide Nishizawa, High sensitive 123I thyroid uptake measurement method. Radiation Safety Management, Vol. 3, No. 1, 11-19, 2004.

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