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Cone Morphological Variation of the Picea jezoensis Complex in Eastern Asia
Park, Yeong-Dae,Chang, Kae-Sun,Jin, Guang Ze,Kim, Hui,Chang, Chin-Sung Korean Society of Forest Science 2010 한국산림과학회지 Vol.99 No.2
Picea jezoensis with several infraspecific taxa is indigenous to Eastern Asia and the Far East of Russia. Although these taxa are very common, the taxonomic confusion surrounding this complex is reflected in ambiguity of the various taxonomic treatments currently used. Patterns of intraspecific variations of cone morphology and recognition of taxa within the P. jezoensis complex were investigated from 175 individuals. Morphological variation of cone characters was determined by the univariate analysis to be insignificant in separating most previously recognized infraspecific taxa in Korea, China, Russia, and Japan. Our statistical analysis showed that cones from northern populations were larger and wider than those from southern populations. Individuals from South Korea were predominantly smaller even than those from Honshu of Japan which were previously recognized as var. hondoensis. All measured characters appeared to show some clinal variation with changes in latitude, and a distinctive trend was evident. Consequently var. hondoensis, var. koreana, and var. microsperma cannot retain their infraspecific state within the P. jezoensis complex.
Park, Young Chang,Jeong, Sung Hoon,Kim, Yong Hwan,Lee, Seung Jae,Lee, Young Ze Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.345 No.-
<P>The experimental investigation was performed to find the associated changes in characteristics of fretting wear with various water temperatures. Fretting can be defined as the oscillatory motion with very small amplitudes, which usually occur between two contacting surfaces. The fretting wear, which occurs between cladding tubes of nuclear fuel rod and grids, causes in damages the cladding tubes by flow induced vibration in a nuclear reactor. In this paper, the fretting wear tests were carried out using the zirconium alloy tubes and the grids with increasing the water temperature. The tube materials in water of 20, 50 and 80 were tested with the applied load of 20N and the relative amplitude of 200. The worn surfaces were observed by SEM, EDX and 2D surface profiler. As the water temperature increased, the wear volume was decreased. However, oxide layer was increased on the worn surface. The abrasive wear mechanism was observed at water temperature of 20 and adhesive wear mechanism occurred at water temperature of 50 and 80. As the water temperature increased, surface micro-hardness was decreased. Also, wear depth and wear width were decreased due to increasing stick phenomenon. Stick regime occurred due to the formation of oxide layer on the worn surface with increasing water temperatures.</P>
온도 상승이 개량형 핵연료 피복관과 지지격자 사이의 프레팅 마멸에 미치는 영향
박용창(Yong-Chang Park),정성훈(Sung-Hoon Jeong),김진선(Jin-Seon Kim),김용환(Yong-Hwan Kim),이영제(Young-Ze Lee) 한국트라이볼로지학회 2006 한국윤활학회지(윤활학회지) Vol.22 No.3
The experimental investigation was performed to find the associated changes in characteristics of fretting wear with various water temperatures. The fretting wear tests were carried out using the zirconium alloy tubes and the grids with increasing the water temperature. The tube materials in water of 20℃, 50℃ and 80℃ were tested with the applied load of 20 N and the relative amplitude of 200 ㎛. The worn surfaces were observed by SEM, EDX analysis and 2D surface profiler. As the water temperature increased, the wear volume was decreased, but oxide layer was increased on the worn surface. The abrasive wear mechanism was observed at water temperature of 20℃ and adhesive wear mechanism occurred at water temperature of 50℃, 80℃. As the water temperature increased, surface micro-hardness was decreased, but wear depth and wear width were decreased due to increasing stick phenomenon. Stick regime occurred due to the formation of oxide layer on the worn surface with increasing water temperatures.
Gil, Chang-Hyun,Jang, Jae-Woo,Lee, Won-Young,Park, Ze-Won,Lee, Jae-Ho,Chung, Sun-Hwa,Chae, Jung-Il,Chung, Hyung-Min The Korean Society of Animal Reproduction 2009 Reproductive & developmental biology Vol.33 No.4
Cardiovascular diseases (CVDs) are one of the most cause of death around the world and fields of interest for cardiac stem cells. Also, current use of terminally differentiated adult cardiomyocytes for CVDs has limited regenerative capacity therefore any significant cell loss may result in the development of progressive heart failure. Human embryonic stem cells (hESCs) derived from blastocyst-stage embryos spontaneously have ability to differentiate via embryo-like aggregates (endoderm, ectoderm and mesoderm) in vitro into various cell types including cardiomyocyte. However, most effective molecule or optimized condition which can induce cardiac differentiation of hESCs is rarely studied. In this study, we developed both spontaneous and inductive cardiomyocyte-like cells differentiation from hESCs by treatment of induced-factors, 5-azacytidine, BMP-4 and cardiogenol C. On the one hand, spontaneous and inductive cardiomyocyte-like cells showed that cardiac markers are expressed for further analysis by RT-PCR and immunocytochemistry. Interestingly, BMP-4 greatly improved homogeneous population of the cardiomyocyte-like cells from hESCs CHA15 and H09. In conclusion, we verified that spontaneously differentiated cells showed cardiac specific markers which characterize cardiac cells, treated extrinsic factors can manage cellular signals and found that hESCs can undergo differentiation into cardiomyocytes better than spontaneous group. This finding offers an insight into the inductive factor of differentiated cardiomyocytes and provides some helpful information that may offer the potential of cardiomyocytes derived from hESCs using extrinsic factors.