A molten salt reactor (MSR) has considerably attracted attention due to its several advantages for the safety and efficiency over the light water reactors. Because the structural material in MSR is contacted with high-temperature liquid fuel during long-term, the excellent material for corrosion resistance is required to be applied in MSR. In this study, we evaluated the corrosion resistance for alloy 600 and 617, which are the nickel-based materials, in KCl molten salt at 800ºC for 100 h under Ar atmosphere containing less than 1 ppm of moisture and oxygen. After the corrosion experiments of alloy 600 and 617, the amount of the weight loss for them caused by the KCl molten salt were determined. In addition, the variation in the crystal structure, surface morphology, and elemental distribution was examined using X-ray diffraction and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy.

Disposal facilities for radioactive waste shall be sited to provide isolation from the accessible biosphere. The features shall aim to provide this isolation for tens of thousands to a million years after closure. For the safety assessments of repository, the long-term natural evolution and possible events of the site, that can cause disturbances to the facility over the period of interest, should be considered. Geological development processes that the site have been experienced can contribute to understanding and descripting the present-day conditions. Moreover, knowledge of the past is necessary to predict the future evolution of the site. With regard to disposal site, understanding past geological evolution history allows to access the possibility of hazardous events of the site that can cause disturbances to the facility over the period of interest, and to verify the change in the geological environment is within the safe performance range even after the period of interest. In addition, certain parameters that change with the geological evolution can affect the hydrological and geochemical characteristics which are essential to disposal performance. There are various factors in the evolution of the geological environment, but not all are related to disposal safety. The objective of this research is to develop a geological reconstruction method considering factors that should be derived preferentially for the geological characteristics of the disposal site and the evaluation of the long-term safety. As a preliminary study on this, we investigated case studies related to geological reconstruction of overseas disposal research institutes, and reviewed which factors are suitable for the domestic granitoid distribution environment. It is expected that systematic and consistent results will be possible in the future through this methodology.

Elite trees of evergreen oaks (Quercus glauca, Quercus acuta, Quercus salicina, and Quercus gilva) were selected from Jeju Island and Wando Island. Elite trees were carried out by modifying the tree selection criteria. Elite trees were selected by height, DBH, clear length, crown diameter, leaf length, and leaf depth. Regarding height, Q. acuta was the highest, and the other three tree species were similar. Clear length showed the same trend as height. In the case of Q. glauca, height showed a positive correlation with DBH, crown diameter and leaf depth. In the case of Q. acuta, positive correlations were shown with all characteristics of DBH, and correlation analysis between DBH and crown diameter, and leaf length and leaf depth also showed positive correlations. In the Pearson correlation coefficient of Q. salicina, height showed a positive correlation with DBH. In the case of Q. gilva, height showed a positive correlation with DBH (0.539). As a result of analyzing the principal components for each of the six growth characteristics, the four species were divided into two principal components with an eigenvalue of 1 or higher, and the cumulative explanatory power was 57% or more. Based on the principal component results, it was possible to confirm the relationship between growth and trait characteristics by species. Still, it was not easy to understand the relationship among each selection tree, so a cluster analysis was performed using the principal component score. Based on the distance levels 5.0 and 6.0 of the selection tree of each species, they were classified into 4-5 clusters. It is judged that the above results can be used as data for the selection of elite trees of evergreen oaks.

Traf4 (Tumor necrosis factor Receptor Associated Factor 4) is a member of the tumor necrosis factor receptor (TNFR) - associated factors (TRAFs) family. TRAF4 is overexpressed in tumor cells such as breast cancer and associated with cytoskeleton and membrane fraction. Interestingly, TRAF4 was localized with tight junctions (TJs) proteins including OCLN and TJP1 in mammary epithelial cells. However, the expression patterns and biological function of Traf4 were not examined in preimplantation mouse embryos although Traf4-deficient mouse showed embryonic lethality or various dramatic malformation. In this study, we examined the temporal and spatial expression patterns of mouse Traf4 during preimplantation development by qRT-PCR and immunostaining, and its biological function by using siRNA injection. We found upregulation of Traf4 from the 8-cell stage onwards and apical region of cell – cell contact sites at morula and blastocyst embryos. Moreover, Traf4 knockdown led to defective TJs without alteration of genes associated with TJ assembly but elevated p21 expression at the KD morula. Taken together, Traf4 is required for TJs assembly and cell proliferation during morula to blastocyst transition.

Two new free-living marine nematodes of the genus Belbolla Andrássy, 1973 belonging to family Enchelidiidae are newly described based on specimens obtained from a shallow subtidal sediment of the western and southern outermost islands of Korea. Belbolla koreensis sp. nov. differs from other species of the genus by the combination of the following characteristics: longer body length (3,080-3,462 μm long), eight oesophageal bulbs in the posterior region of pharynx, well-developed two winged precloacal supplements (anterior precloacal supplement slightly longer than posterior one: 47-59 μm vs. 43-46 μm long), strongly arcuated, very thick, L - shaped spicule (122- 127 μm long, 1.7-1.9 anal body diameter (a.b.d.) long) with three separated blunt distal tips, and well-developed relatively long cylindrical shaped gubernacular apophysis with blunt teeth covering two thirds of the dorsal margin (57-58 μm long, 0.8-0.9 a.b.d. long). Belbolla hoonsooi sp. nov. is characterized by the following combination of characteristics: longer body length (3,494 μm long), eight oesophageal bulbs in the posterior region of pharynx, well-developed two winged precloacal supplements (anterior precloacal supplement slightly longer than posterior one: 43 μm vs. 36 μm long), strongly arcuated, L - shaped spicule (119 μm long, 1.5 a.b.d. long) with three separated blunt distal tip, and well-developed relatively long inverted triangle shaped gubernacular apophysis with blunt teeth covering half of the dorsal margin (45 μm long, 0.6 a.b.d. long). Detailed morphological characteristics and illustrations of two new Belbolla nematodes from the Korean seawaters were provided by differential interference contrast microscopy. Comparative tables on biogeographical and morphological characteristics of Belbolla species are also provided herein.

This study aims at investigating how the international students' attitudes towards English have changed over th last 3 years in Korea. Forty international students participated in the questionnaire survey three times in 2018, 2019 and 2020. The results were shown as follows: Overall, the mean score of attitudes towards English decreased proportionally over time. English use has also decreased over time. When analyzing these attitudes towards English by the degree of English proficiency, the group with higher English proficiency at the time of admission had a more higher score of attitude to English in three year questionnaire surveys. In addition, these attitudes towards English have changed in small in the group of higher English proficiency over time, while the big change appeared to the group of lower English proficiency. The results of this study imply that English-based international students' attitudes towards English are likely to change over time in Korea, and that groups with relatively low English proficiency are more likely to change than groups with higher English proficiency.