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스프리 강(독일)내의 호수와 강 구획에서의 동물플랑크톤 성장의 차이
김현우,주기재,Walz, Norbert 한국육수학회 2000 생태와 환경 Vol.33 No.3
Factors most strongly related to zooplankton growth rates were studied along a lake and a river stretch in the middle part of the lowland River Spree. The study was conducted at the lake inflow (S1), the lake outflow (S2), and at the end of a 21 km stretch of the outflow (S3) from March to November of 1999. Total zooplankton biomass increased significantly at S2 and then sharply decreased at S3. The abundance of microzooplankton (rotifers and nauplii) was strongly higher than macrozooplankton (cladocerans and copepodids) at all stations. However, macrozooplankton biomass (㎍ dw 1^(-1)) was similar or much higher than microzooplankton biomass. Large-bodied cladocerans (Daphnia cucullata) dominated at S2 while small-bodied cladocerans (Bosmina longirostris) dominated at S1 and S3. Patterns in growth rates (r_t in d^(-1)) of the major zooplankton community were greatly different between S1 and S2 (lake stretch) and between S2 and S3 (river stretch). In the lake, growth rates generally were positive, while values of growth rates were negative in the river stretch. Among the environmental variables considered, partial retention time (PRT, d^(-1)) seemed to play the most important role in determining characteristics of the zooplankton community structure in the middle part of River Spree.
김현우 한국영어교육학회 2009 ENGLISH TEACHING(영어교육) Vol.64 No.3
This study aims to examine the perception change of 29 graduate students toward both teacher and peer feedbacks over one semester, while they are taking a process-oriented writing course. They are all graduate students, and major in teaching English as a foreign language. Pre- and post-surveys were conducted to see if there were any perception changes toward teacher and peer feedbacks during the semester. Along with the distribution of questionnaires, subsequent analysis was conducted as well: all descriptive writing drafts of 2 participants were closely examined along with the post-interview session. In addition, all feedback sessions 2 participants were engaged in were audiotaped and transcribed. With these data, all descriptive writing drafts of them were analyzed according to Faigley and Witte’s (1981) taxonomy. The result reveals that teacher feedback was consistently preferred over peer feedback by 29 students during the semester. However, 2 participants responded that they had difficulty in understanding oral and written feedbacks respectively. The pedagogical implication of this result is the need of training L2 writers to peer feedback into the L2 writing course in the tertiary education.
Apoptotic Effects of 6-Gingerol in LNCaP Human Prostate Cancer Cells
김현우,오덕희,정채용,권동득,임영채 순천향대학교 순천향의학연구소 2011 Journal of Soonchunhyang Medical Science Vol.17 No.2
Objective: 6-Gingerol, one component of ginger (Zingiber officinale) compound, has been known to possess anti-inflammatory, analgesic,anti-emetic, and anti-cancer effects. In this study, the apoptotic ability of 6-gingerol was investigated in human prostate cancer cells. Methods: 3-(4,5-Dimethylthiazol-2-yl)- 2,5-diphenyl-tetrazolium bromide (MTT) assay, flow cytometry, and western blot analysis were done in LNCaP human prostate cancer cell lines treated with the various doses of 6-gingerol for the different durations of drug exposure. Results: 6-Gingerol in doses ranging from 100 to 300 μM induced dose- and time-dependent inhibition of cell viability in prostate cancer cells by using MTT assay. Maximal inhibition of cell viability was observed at 300 μM of 6-gingerol for 48 hours treatment in LNCaP cells. 6-Gingerol at the dose of 100 μM did not produce any significant change in apoptotic cells in flow cytometry analysis. However, significant increase in sub-G0/G1 phase was observed in cells treated with 200 and 300 μM of 6-gingerol. Any significant cell cycle arrest was not induced by 6-gingerol. In western blotting analysis, expression of caspase-3 was not evident in cells treated with 6-gingerol for 24 hours. However, 48 hours treatment with 6-gingerol altered the expression of caspase-3 in LNCaP cells. Expression of cleaved poly showed the dose-dependent fashion in both 24 hours and 48 hours treatment of 6-gingerol. Conclusion: These observations suggest that 6-gingerol may induce apoptosis in LNCaP human prostate cancer cells.
초고강도강의 냉간 성형을 위한 고내구 금형강의피로 특성 평가
김현우,김기풍 한국기계기술학회 2020 한국기계기술학회지 Vol.22 No.6
In this study, the fatigue properties of press die steel, such as SKD11, and three high-durability die steel for the cold forming of ultra-high-strength steel sheets are evaluated. Specimens for fatigue, tensile, and hardness tests are manufactured through the heat treatment recommended by steelmakers and ultra-high precision processing. The general mechanical properties and fatigue properties are derived from hardness, tensile, and fatigue tests for four die steel. The tensile and fatigue properties of die steel derived through the tests are compared and analyzed. In particular, the correlation between the fatigue limit and the general mechanical properties such as tensile strength and elongation is analyzed, which allows relational expressions to be obtained through regression analysis. Finally, the study confirms that applying high-durability die steel is necessary for improving the die life in the manufacturing of press dies for ultra-high-strength steel sheets.
김현우,나양온,황혜림 한국영어교육학회 2020 ENGLISH TEACHING(영어교육) Vol.75 No.-
Usage-based approaches to language acquisition explain language development as a gradual process of generalizing constructions through language experience. This study investigated second language learners’ development of constructional knowledge from the perspective of usage-based language development. A total of 169 Korean EFL students at five grade levels completed a sentence-sorting and a translation task. Results of the sorting task showed stronger constructional sorting as the learners’ grade level increased. Additionally, the sorting of intermediate-level learners was influenced by verb semantics such that the sentences including light verbs were more strongly clustered according to constructions than the sentences with heavy verbs, suggesting learners’ reliance on light verbs in the early stages of constructional development. Results of the translation task demonstrated a higher translation accuracy with increasing proficiency, but with a significant amount of variation across individual constructions contingent on the constructions’ syntactic and semantic complexity. Overall, our findings confirm the usage-based development of L2 learning.