For combination with microscope, we developed real-time autoradiography system for micro-scale analysis with adjustment of the CsI(Ti) scintillator thickness for higher resolution and applying tapered fiber optic plate for magnification of autoradiograph image. We combined real-time autoradiography system with an inverted fluorescent microscope so that an autoradiograph image as well as fluorescent image, bright-field image can be acquired at the same time. In the case of observation of sliced soybean stalk traced 45CaCl, the fluorescent and bright-field image was acquired which magnified to 50 times, the autoradiograph image of 45Ca distribution in the tissue was acquired in almost same scale. The new microscopic system which can acquire autoradiograph image of labeled signals (low molecular weight) is expected to develop the signal transduction study and gene expression, combined with fluorescent protein techniques such as GFP etc.
We presented alanine, a kind of amino acids, uptake by a rice seedling to study the basic mechanism of the organic fertilizer effectiveness in organic farming. The rice grown in the culture solution containing alanine as a nitrogen source absorbed alanine approximately two times faster than that grown with NH4+ from analysis of 14C-alanine images by Imaging Plate method. It was suggested that the active transport ability of the rice seedling was induced in roots by existence of alanine in the rhizosphere. The alanine uptake images of the rice roots were acquired every 5 minutes successively by the real-time autoradiography system we developed. The analysis of the successive images showed that alanine uptake was not uniform throughout the root but especially active at the root tip.
The effectiveness of electron beam(EB) disinfection and sterilization technology and the changes of essential oil components in fennel were investigated. The absorbed dose was maximal at a depth of 0.9 – 1.0g/cm2, which was 130% of the surface dose of 15 kGy in packed fennel irradiated with 5 MeV EB in a downward direction, and decreased in the deepest layer. As a result, in a fennel bacterial count of 105 cfu/g, a microbial contamination level below 1.0×103 cfu/g was obtained at a packing depth of 2.3 g/cm2 and at the absorbed dose of more than 3 kGy. The bacteria in fennel were highly sensitive to EB irradiation. Furthermore, EB irradiation had no effect on the essential oil content of fennel, and no change of the essential oil components was found at the irradiation level necessary for decontamination.
The concentrations of tritium and several cations in precipitation were measured in Niigata (near the coast of the Japan Sea) during December, 2003 to November, 2006. The purpose of this work is analyzing the movement of air mass by means of clarifying the relationship between the concentrations of tritium and several cations. Monthly samples were collected by the original sampling system that can collect the precipitation similar to ground infiltration. As a result, this work leads to the following matters. (1) The concentration of tritium much relates to that of Ca2+. (2) The concentration of tritium (the concentration depends on the air mass of precipitation-origin) has seasonal dependence. (3) This tendency remarkably appears in a continental air mass. (4) The concentration of tritium in precipitation can be estimated by using the mixture ratio of continental air mass and oceanic air mass.
The Medical Internal Radiation Dosimetry (MIRD) method assumes that the beta particle energy is absorbed completely in the source organ. However, the organs of mice used in fundamental experiments for internal radiotherapy are relatively small compared to the range of high-energy 90Y beta particles. Therefore, it is well known that the high-energy beta particle can escape the source organ, resulting in large cross-organ doses. The more realistic geometric model such as a voxel-phantom based on Computed Tomography scans for a mouse has been needed for accurately estimating internal doses from administered beta particle emitters. Then it becomes important to simulate the beta particle transport precisely using the Monte Carlo code. The purpose of this study is to validate a user code to simulate the beta particle transport in a mouse in the Monte Carlo code system (EGS5) by comparing with the absorbed dose measured using a number of small fluorescent glass dosimeters and one capsule of 90YCl3 solution implanted in a small tough-water phantom simulating a mouse. It was found that the absorbed dose distribution in this phantom calculated with this user code gave rather good agreement with the measured results.
The system of management related to safety on nuclear materials, especially the internal/international situations to link to nuclear safe guard has been explained, and its history has been shown. In addition, important points to be noticed in Japanese regulation for use of small amount of nuclear materials have been discussed, and an example of effective education programs mainly for workers has been introduced.