Japanese contribution to the DEMO-R&D program under the Broader Approach activities

Several technical R&D activities mainly related to the blanket materials are newly launched as a part of the Broader Approach (BA) activities, which was initiated by the EU and Japan. According to the common interests for these parties in DEMO, R&Ds on reduced activation ferritic/martensitic (RAFM) steels as structural material, SiC_f/SiC composites as a flow channel insert material and/or alternative structural material, advanced tritium breeders and neutron multipliers, and tritium technology are carried out through the BA DEMO R&D program, in order to establish the technical bases on the blanket materials and the tritium technology required for DEMO design. This paper describes overall schedule of those R&D activities and recent progress in Japan carried out by JAEA as the domestic implementing agency on BA, collaborating with Japanese universities and other research institutes.     

Design strategy and development of spherical silicon solar cell with semi-concentration reflector system

Structural and economical merits of a spherical silicon solar cell with semi-concentration reflector system have been discussed. The roles of the reflector system have been clarified; the reflector improves short-circuit current density and also open-circuit voltage by 4–6 times concentration to make a light irradiation area comparable to a p–n junction area. We have theoretically demonstrated that the spherical Si solar cell with semi-concentration reflector system can realize a performance comparable to that of conventional Si solar cells, with less amount of silicon material use.     

Improved methodology for the simultaneous detection of the trichothecene mycotoxins deoxynivalenol and nivalenol in cereals

A simple and sensitive method has been developed for the analysis of two trichothecene mycotoxins (deoxynivalenol and nivalenol) in cereals. These toxins were extracted with acetonitrile/water (3:1), defatted with n-hexane and purified by a two-step chromatographic procedure using Florisil and Sep-pak columns. The amounts of deoxynivalenol (DON) and nivalenol (NIV) in the column eluates were quantitated by gas chromatography with electron capture detector and gas chromatography-mass spectrometry (selected ion monitoring). The limits of detection of the method were 2.0 micrograms/kg for DON and NIV with recoveries of the toxins spiked into polished rice, wheat and corn at 300 micrograms/kg averaging 87% and 86% respectively.     

Levels of glutathione and related enzymes in yellowtail fish muscle subjected to ice storage in a modified atmosphere

We investigated the effects of ice storage in a modified atmosphere on levels of glutathione (GSH) and its related enzyme activities, the metmyoglobin to total myoglobin ratio (metMb%), and the K value (a freshness index) of yellowtail fish muscle. GSH in ordinary muscle (fast skeletal muscle) as well as in dark muscle (slow skeletal muscle) stored in air decreased. GSH in those muscles was almost unchanged during storage when packaged with an oxygen absorber or with an oxygen absorber-CO(2) generator. Glutathione disulfide in each type of packaging remained at low concentrations during storage. The GSH peroxidase activities of ordinary muscle and of dark muscle after 7 d of storage in air were lower than when packaged with the oxygen absorber or with the oxygen absorber-CO(2) generator. The GSH reductase (GR) activities of ordinary muscle at the 4th and 7th day of storage when packaged with the oxygen absorber showed a tendency to be lower than when stored in air. The GR activity of dark muscle in each type of packaging method was unchanged during storage. The packaging method did not influence the K values of either the ordinary muscle or the dark muscle during storage. The metMb% of dark muscle when packaged with the oxygen absorber was lower than in the other types of packaging during storage. Therefore, packaging with the oxygen absorber is an effective method to prevent the loss of GSH in fish meat as well as to reduce the discoloration during storage. PRACTICAL APPLICATION: This study examined whether modified atmosphere packaging preserves the level of GSH, which is unstable to oxidative stress, in fish muscle. The use of an oxygen absorber for packaging can allow us to take in a sufficient amount of the bioactive compound from fish meat after storage as well as fresh fish.     

Crystallization kinetics of polymorphic forms of a molecular compound constructed by SOS (1,3-distearoyl-2-oleoyl-sn-glycerol) and SSO (1,2-distearoyl-3-oleoyl-rac-glycerol)

Crystallization kinetics of binary mixture phases of SOS (1,3-distearoyl-2-oleoyl-sn-glycerol) and SSO (1,2-distearoyl-3-oleoyl-rac-glycerol) were examined with time-resolved X-ray diffraction (XRD) and DSC methods. Formation of three polymorphic forms, named _c, β′_c and β_c, of a molecular compound was observed at a SOS/SSO=50/50 concentration ratio. The XRD data showed that all three polymorphs were arranged in a double chain-length structure, although a triple chain-length structure is formed in and β′ forms of SSO, and β′ and β forms of SOS. The time-resolved XRD studies showed that _c and β_c forms of the molecular compound crystallized more rapidly than the corresponding polymorphic forms of SOS and SSO. The results were discussed in terms of molecular chain–chain interactions of SOS and SSO, by assuming that kinetic processes of nucleation may prefer the formation of the _c and β_c forms arranged in the double chain-length structure.     

Material-binding peptide application--ZnO crystal structure control by means of a ZnO-binding peptide

Recently, a zinc oxide (ZnO)-binding peptide (ZnOBP) has been identified and has been used to assist the synthesis of unique crystalline ZnO particles. We analyzed the influence of ZnOBP on the crystal growth of ZnO structures formed from zinc hydroxide. The addition of ZnOBP in the hydrothermal synthesis of ZnO suppressed [0001] crystal growth in the ZnO particles, indicating that the specificity of the material-binding peptide for specific inorganic crystal faces controlled the crystal growth. Furthermore, the dipeptides with a partial sequence of ZnO-binding "hot spot" in ZnOBP were used to synthesize ZnO particles, and we found that the presence of these dipeptides more strictly suppressed (0001) growth in ZnO crystals than did the complete ZnOBP sequence. These results demonstrate the applicability of dipeptides selected from material-binding peptides to control inorganic crystal growth.     

Damage of yeast cells induced by pulsed light irradiation

DNA damage, such as formation of single strand breaks and pyrimidine dimers was induced in yeast cells after irradiation by pulsed light, which were essentially the same as observed with continuous ultraviolet (UV) light. The UV-induced DNA damage is slightly higher than seen with pulsed light. However, increased concentration of eluted protein and structural change in the irradiated yeast cells were observed only in the case of pulsed light. A difference in the inactivation effect between pulsed light and UV light was found and this suggested cell membrane damage induced by pulsed light irradiation. It is proposed that pulsed light can be used as an effective sterilizing method for the yeast Saccharomyces cerevisiae.     

Effect of direct ovarian injection of vascular endothelial growth factor gene fragments on follicular development in immature female rats

Vascular endothelial growth factor (VEGF) expression in granulosa cells is associated with the thecal vasculature growth during ovarian follicular development. We hypothesized that injection of VEGF gene fragments directly into the rat ovary would induce production of a large number of ovulatory follicles and that these follicles would ovulate. To test this hypothesis, we treated immature female rats with combinations of hormones and VEGF gene fragments. The animals were divided into two groups: one group received solution containing transfection reagents as a control (n = 5), while the other group received direct ovarian injection of VEGF gene fragments at 19 (n = 5), 21 (n = 5), 23 (n = 5), or 25 (n = 5) days after birth followed by i.p. administration of 20 IU equine chorionic gonadotropin (eCG) at the age of 26 days. Forty-eight hours after eCG injection, animals were given 20 IU human chorionic gonadotropin (hCG) i.p. and then the oocytes in both groups were counted. The maximum number of ovulated oocytes was obtained when the VEGF gene fragments were injected into the rat ovary at 21 days after birth. Histological examination revealed that the injection of VEGF gene fragments markedly increased the vascular density around the preovulatory follicles and also the number of these follicles. Our data provide the first reported evidence that most ovulatory follicles generated by injection of VEGF gene fragments are able to ovulate upon hCG treatment. These results demonstrate that injection of VEGF gene fragments directly into the ovary stimulates the development of antral follicles by inducing the formation of thecal vasculature in immature female rats.     

Effects of cubic BN addition and phase transformation on hardness of Al2O3-cubic BN composites

The Vickers hardness of dense Al₂O₃-cubic BN (cBN) composites prepared by spark plasma sintering under a moderate pressure of 100 MPa at 1200-1600 °C was investigated at indentation loads of 0.098-19.6 N. The BN grains in the Al₂O₃-BN composite prepared at 1300 °C showed no transformation from the cBN to hBN phase, and the hardness was 59 GPa at 0.098 N. The hardness of the Al₂O₃ matrix in the Al₂O₃-BN composites containing 10-30 vol% cBN prepared at 1300-1400 °C was around 25 GPa at 0.098 N, which was higher than monolithic Al₂O₃ bodies prepared at the same temperatures. The hardness of the Al₂O₃ matrix in the Al₂O₃-BN composites decreased with increasing sintering temperature. The increase in the hardness of the Al₂O₃ matrix may be due to the decrease in the size of Al₂O₃ grains in the Al₂O₃-BN composites owing to the addition of cBN particles and the decrease in sintering temperature. The Meyer exponents of the monolithic Al₂O₃ bodies and Al₂O₃-BN composites were 1.90-1.94 independent of cBN content.