• Molecules and Cells
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• v.27 no.3
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• pp.359-363
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• 2009

Chfr, a checkpoint with FHA and RING finger domains, plays an important role in cell cycle progression and tumor suppression. Chfr possesses the E3 ubiquitin ligase activity and stimulates the formation of polyubiquitin chains by Ub-conjugating enzymes, and induces the proteasome-dependent degradation of a number of cellular proteins, including Plk1 and Aurora A. While Chfr is a nuclear protein that functions within the cell nucleus, how Chfr is localized in the nucleus has not been clearly demonstrated. Here, we show that nuclear localization of Chfr is mediated by nuclear localization signal (NLS) sequences. To reveal the signal sequences responsible for nuclear localization, a short lysine-rich stretch (KKK) at amino acid residues 257-259 was replaced with alanine, which completely abolished nuclear localization. Moreover, we show that nuclear localization of Chfr is essential for its checkpoint function but not for its stability. Thus, our results suggest that NLS-mediated nuclear localization of Chfr leads to its accumulation within the nucleus, which may be important in the regulation of Chfr activation and Chfr-mediated cellular processes, including cell cycle progression and tumor suppression.

• Journal of the Korean Society of Safety
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• v.20 no.2 s.70
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• pp.32-37
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• 2005

The purpose of this study is for the sensitivity study f9r a Steam Generator Tube Rupture (SGTR) of the System-integrated Modular Advanced ReacTor for a Pilot (SMART-P) plant. The thermal hydraulic analysis of a SGIR for the Limiting Conditions for Operation (LCO) is performed using TASS/SMR code. The TASS/SMR code can calculate the core power, pressure, flow, temperature and other values of the primary and secondary system for the various initiating conditions. The major concern of this sensitivity study is not the minimum Critical Heat Flux Ratio(CHFR) but the maximum leakage amount from the primary to secondary sides at the steam generator. Therefore the break area causing the maximum accumulated break flow is researched for this reason. In the case of a SGIR for the SMART-p, the total integrated break flow is 11,740kg in the worst case scenario, the minimum CHFR is maintained at Over 1.3 and the hottest fuel rod temperature is below 606"I during the transient. It means that the integrity of the fuel rod is guaranteed. The reactor coolant system and the secondary system pressures are maintained below 18.7MPa, which is system design pressure.

• Nuclear Engineering and Technology
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• v.29 no.6
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• pp.49-59
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• 1997

본 기술 보고는 임계 열유속(Critical Heat Flux; CHF)을 예측하기 위해 사용되고 있는 상관식의 형태와 적용 방법, 이에 따른 예측 오차와 여유도의 변화 등을 종합적으로 분석한다. CHF 현상에 대해서는 지난 반 세기 동안 발생 메커니즘, 예측 모델, 설계에의 적용 방법 등에 대한 연구가 광범위하게 수행되어 대부분의 운전 조건에 대해 신뢰할만한 예측 모델들이 확립되어 있다. 그러나 예측 모델의 이용에서 가장 중요한 기준이 되는 예측 오차의 의미가 잘못 이해되는 경우가 많으므로, 이 글에서는 예측 모델의 형태 및 적용 방법에 따라 예측 오차가 달라지는 원인을 명확하게 해석하고, 실제 계산을 통하여 예시하였다. 그리고 상관식 형태 및 이용 방법에 따라 임계 열유속비(Critical Heat Flux Ratio: CHFR)와 임계 출력비(Critical Power Ratio; CPR)가 어떠한 관계를 갖는가를 논의하였다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.379-384
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• 1996

Thermal-hydraulic performance has been analyzed for an advanced reactor core loaded with hexagonal fuel assemblies. Currently available CHF prediction models and data base for triangular lattice bundles have been thoroughly reviewed, and as a result the KfK-3 CHF correlation with limit CHFR of 1.235 has been determined to be most appropriate. The pressure drop model in COBRA-IV-I code has been modified for the analysis of triangular lattice rod bundles. In view of maximizing the thermal margin, the geometry of a hexagonal fuel assembly, such as rod diameter and rod pitch, has been optimized with a fixed fuel assembly cross sectional area The optimum value of the moderator-to-fuel volume ratio is estimated to lie between 0.65 to 1 with 9.5 mm rod diameter. The thermal margin of these hexagonal fuel assemblies in the AP600 core has been evaluated and compared with that of square lattice fuel assemblies such as VANTAGE-5H and KOFA. The analysis result shows that the performances of hexagonal fuel assemblies are more favorable than the square fuel assemblies in the aspect of steady-state overpower margin.

• Korean Journal of Food Science and Technology
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• v.37 no.1
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• pp.113-121
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• 2005

Antimicrobial effects of Camellia japonica L. were determined against Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Listeria monocytogenes using paper disc method, and minimum inhibitory concentrations (MICs) were measured. Methanol extract (MEex), water fraction (WAfr), and butanol fraction(BUfr) showed antimicrobial effects against all tested microorganisms, with MEex showing strong antimicrobial effect against S. aureus and L. monocytogenes, and WAfr, Bufr, and ethylacetate fraction (EAfr)against S. aureus. No effects were observed in n-hexane fraction (HEfr) and chloroform fraction (CHfr) against all tested microorganisms. All species grown in the medium adding fractions of Camellia Japonica L. leaves extact were inhibited from WAfr and BUfr, repectively.(meaning not clear) MEex showed over 25% inhibitory effect against all tested microorganisms. BUfr showed over 50% inhibitory effect against all microorganisms except L. monocytogenes. EAfr and WAfr showed over 30% effect against S. aureus and L. monocytogenes. MICs of MEex against S. typhimurium and BUfr against S. aureus were 625 g/mL, indicating C. japonica L. extract can exert antimicrobial activity even at low concentration.