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  • Author: N. Takahashi x
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Abstract

Carbon-14 is one of the critical radionuclides for the dose estimation from nuclear fuel reprocessing plants and nuclear waste disposal facilities. To assess the impact on public health caused by carbon-14 released from these nuclear facilities in Japan, a reasonable estimation of internal dose from the rice ingestion is necessary because rice is a staple food. Therefore, we are developing a dynamic compartment model to predict carbon-14 behavior in atmosphere – paddy soil – rice plant system and carbon-14 concentration in rice by using a migration prediction code, MOGRA. In this model, growing curves of “leaf and stem part” and “ear part” of a rice plant were fitted to sigmoid curves. The transfer coefficients between the compartments were estimated by using sub-models and parameters which describe transfer mechanisms of carbon in a rice paddy field, such as photosynthesis, translocation and respiration in a rice plant. A validation study of the model, carried out with “Rice Scenario” presented by the IAEA EMRAS (Environmental Modelling for RAdiation Safety) project, showed that the developed model can be practically used to predict the carbon-14 concentration in rice. The model was also applied for hypothetical releases of carbon-14 from nuclear fuel reprocessing plant. In addition, parameter sensitivity analyses were carried out to select critical parameters.

Abstract

The mode of action of three types of conjugated enamine compounds was investigated by means of thermoluminescence measurement. Cyanoacrylate and 2-(l-ethoxyethylam inom ethylidene)- 4-dodecyl-5,5-dim ethyl-cyclohexane-1,3-dione (ACm12) converted the B-band (30 °C) arising from S2QB - charge recombination to a downshifted 6 °C-band. This band was proved to be identical with the DCM U-induced Q-band (6 °C) arising from S2QA - recombination, indicating that these two compounds block QA to QB electron transport. 3-(1-dodecylam inopropyridene)-6- methyl-2H-pyran-2,4-dione (APp12 ), on the other hand, induced an abnormal band peaking at 15 °C between the Q-band and B-band. From the gradual downshift of its peak temperature in titration experiments, this band was assigned to arise from a modified S2QB - charge pair, in which the properties of either QB - or S2 is altered. The 15 °C-band showed normal oscillation during the first 2 flashes, but the oscillation was interrupted thereafter. Another therm oluminescence analysis by use of post flash low temperature illumination protocol revealed that APp12 affects neither QA to QB nor QB 2- to PQ electron transport, but specifically blocks S3 to S0 transition. These results indicate that APp12 is a new-type PS II inhibitor.

Abstract

Functional analysis using RNAi was performed on eleven genes for metalloproteases of the M12A family in Caenorhabditis elegans and the interference of the C17G1.6 gene (nas-37) was found to cause incomplete molting. The RNAi of the C26C6.3 gene (nas-36) also caused a similar molting defect but not so severely as that of the nas-37 gene. Both the genes encode an astacinlike metalloprotease with an epidermal growth factor (EGF) like domain, a CUB domain, and a thrombospondin-1 domain, in this order. The promoterdriven green fluorescent protein (GFP) expression analysis suggested that they are expressed in hypodermal cells throughout the larval stages and in the vulva of adult animals. In the genetic background of rde-1(ne219), where RNAi does not work, the molting defect caused by the nas-37 interference was observed when the transgenic wildtype rde-1 gene was expressed under the control of the dpy-7 promoter, known to be active in the hypodermal cells, but not under the control of the myo-3 promoter, active in the muscular cells. Therefore these proteases are thought to be secreted by the hypodermal cells and to participate in shedding of old cuticles.

Abstract

To understand the stability of hydrous phases in mafic oceanic crust under deep subduction conditions, high-pressure and high-temperature experiments were conducted on two hydrous basalts using a Kawai-type multi-anvil apparatus at 17–26 GPa and 800–1200 °C. In contrast to previous studies on hydrous basalt that reported no hydrous phases in this pressure range, we found one or two hydrous phases in all run products at or below 1000 °C. Three hydrous phases, including Fe-Ti oxyhydroxide, Al-rich phase D and Al-rich phase H, were present at the investigated P-T conditions. At T ≤ 1000 °C, Fe-Ti oxyhydroxide is stable at 17 GPa, Al-rich phase D is stable at 18–23 GPa, and Al-rich phase H is stable at 25–26 GPa. Our results, in combination with published data on the stability of hydrous phases at lower pressures, suggest that a continuous chain of hydrous phases may exist in subducting cold oceanic crust (≤1000 °C): lawsonite (0–8 GPa), Fe-Ti oxyhydroxide (8–17 GPa), Al-rich phase D (18–23 GPa), and Al-rich phase H (>23 GPa). Therefore, in cold subduction zones, mafic oceanic crust, in addition to peridotite, may also carry a substantial amount of water into the mantle transition zone and the lower mantle.

Abstract

Trivalent actinides Am(III), Cm(III), and Cf(III) were successfully separated for the first time using capillary electrophoresis in 2-hydroxyisobutyric acid/acetic acid. It was found that the ionic radius was primarily important for separation of trivalent actinides as well as lanthanides in this condition. The stability constants of the Am(III) complexes with 2-hydroxyisobutyrate were estimated using the correlations between the molar fraction ratio of lanthanides and their ionic radii.