• 한국미생물·생명공학회지
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• 제22권6호
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• pp.636-642
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• 1994

Essential amino acids involving in the catalytic mechanism of the $\beta$-D-xylosidase of Bacillus stearothermophilus were determined by chemical modification studies. Among various che- mical modifiers tested N-bromosuccinimide (NBS), $\rho$-hydroxymercurybenzoate (PHMB), N-ethylma- leimide, 1-[3-(di-ethylamino)-propyl]$-3-ethylcarbodi-imide (EDC), and Woodward's Reagent K(WRK)inactivated the enzyme, resulting in the residual activity of less than 20%. WRK reduced the enzyme activity by modifying carboxylic amino acids, and the inactivation reacion proceeded in the form of pseudo-first-order kinetics. The double-lagarithmic plot of the observed pseudo-first- order rate constant against the modifier concentration yielded a reaction order of 2, indicating that two carboxylic amino acids were essential for the enzyme activity. The $\beta$-D-xylosidase was also inactivated by N-ethylmaleimide which specifically modified a cysteine residue with a reaction order of 1, implying that one cysteine residue was important for the enzyme activity. Xylobiose protected the enzyme against inactivation by WRK and N-ethylmaleimide, revealing that carboxylic amino acids and a cysteine residue were present at the substrate-binding site of the enzyme molecule.

• 한국진공학회지
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• 제5권3호
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• pp.229-238
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• 1996

The electromigration phenomena and the characterizations of the conductor lifetime (Time-To-Failure, TTF) in Al-1%Si thin film interconnections under D.C. and Pulsed D.C. conditions were investigated . Meander type test patterns were fabricated with the dimensions of 21080$mu \textrm{m}$ length, 3$\mu\textrm{m}$ width, 0.7$\mu\textrm{m}$ thickness and the 0.1$\mu\textrm{m}$/0.8$\mu\textrm{m}$($SiO_2$/PSG)dielectric overlayer. The current densities of $2 \times10^6 A/\textrm{cm}^2$ and $1 \times10^7 A/\textrm{cm}^2$ were stressed in Al-1%Si thin film interconnection s under a D.C. condition. The peak current densities of $2 \times10^6 A/\textrm{cm}^2$ and $1 \times10^7 A/\textrm{cm}^2$ were also applied under a Pulsed D.C. condition at frequencies of 200KHz, 800KHz, 1MHz, and 4MHz with the duty factor of 0.5. THe time-to-failure under a Pulsed D.C.($TTF_{pulsed D.C}$) was appeared to be larger than that under a D.C. condition. It was found that the TTF under both a D.C. and a Pulsed D.C. condition. It was found that the TTF under both a D.C. and a Pulsed D.C. condition largely depends upon the appiled current densities respectively . This can be explained by a relaxation mechanism view due to a duty cycle under a Pulsed D.C. related to the wave on off. The relaxation phenomena during the pulsed off period result in the decayof excess vacancies generated in the Al-1%Si thin film interconnections because of the electrical and mechanical stress gradient . Hillocks and voids formed by an electromigration were observed by using a SEM (Scanning Electron Microscopy).

• 한국식품과학회지
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• 제39권3호
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• pp.330-335
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• 2007

기존의 연구에서 보고된 잎새버섯의 항당뇨 효과에 대한 메카니즘을 설명하고자 본 연구에서는 잎새버섯의 인슐린 민감성 향상 제재로서의 가능성을 확인하고자 하였다. 이를 위하여 잎새버섯 열수추출물의 분획물을 분리하여 인슐린 저항성을 가진 3T3-L1 지방세포에서의 포도당 흡수 정도를 관찰하였다. 실험결과 HW-I이 3T3-L1 지방세포의 인슐린 민감성을 향상시켜 세포 내로의 포도당 섭취를 대조군 대비 4.2배 향상시켰다. 제2형 당뇨모델인 5주령 $KK/A^{y}$ 마우스를 3주간 적응시킨 뒤 HW-I을 8주간 자유 식이 하면서 식이 섭취량, 음수 섭취량 및 체중변화를 관찰하였고 혈액중 포도당 농도, 혈장 인슐린 농도, 당화혈색소를 측정하였으며 결과는 다음과 같다. HW-I식이군은 control군과 비교하여 식이 섭취량 및 최종 체중간에는 유의적인 차이가 없었으나 음수 섭취량에 있어서는 control군에 비해 거의 2배정도 적은 섭취량을 보여 유의적인 차이를 나타내었다(p<0.001). 혈중 포도당 농도는 HW-I 식이군의 경우 control군과 비교하여 식이 1주째 $335.4{\pm}51.8$ mg/dL로 유의적으로 낮은 혈당치를 나타내기 시작하여(p<0.01) 식이 8주째 $311{\pm}96.8$ mg/dL로 유의적인 혈당 억제 효과를 나타내었다(p<0.001). 혈장 인슐린 농도는 HW-I 식이군의 경우 $84.7{\pm}18.9$ ng/mL로 control군의 $342.7{\pm}125$ ng/mL 비교하여 24.7% 수준으로 유의적인 감소 효과를 나타내었다(p<0.001). 당화혈색소 농도는 HW-I 식이군의 경우 8.99%로 control군의 9.87%보다 유의적인 감소 효과를 나타내었다(p<0.05). 이상에서 잎새버섯 열수추출물의 조다당체인 HW-I이 인슐린 민감성 효과가 있는 것으로 밝혀졌으며 제2형 당뇨모델인 $KK-A^{y}$ 마우스를 이용한 동물실험에서도 뚜렷한 혈당강하효과를 나타내어 인슐린 민감성 제재로 개발 할 수 있는 가능성을 보여 주었다.

• 과학교육연구지
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• 제38권3호
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• pp.703-717
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• 2014

물리에서 멘탈 시뮬레이션은 개념을 이해하거나 생성하기 위한 중요한 매커니즘이다. 만약 학생들이 멘탈 시뮬레이션에 어려움을 겪는다면 물리 개념의 이해 또한 어려워진다. 3차원 시뮬레이션 콘텐츠는 학생들에게 공간적 조작의 가이드를 제공함으로써 물리 개념 이해를 도울 수 있다. 이 연구에서는 빛의 직진 개념의 이해를 돕기 위한 3차원 시뮬레이션 콘텐츠를 개발하여 대학생 20명에게 적용하였다. 적용 결과, Hake gain이 0.93으로 수업에 대해 매우 높은 수준의 이해도를 보였다. 또한 학생들은 새로운 맥락에 대해서도 멘탈 시뮬레이션을 통해 현상을 잘 예측하였다. 이를 통해 3차원 시뮬레이션 콘텐츠를 통해 학생들의 개념 이해가 잘 이루어졌음을 알 수 있다.

• 한국해양공학회지
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• 제12권3호통권29호
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• pp.49-59
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• 1998

The damage mechanism of $Cr_2O_3$ plasma coated soda-lime glass and uncoated glass by steel ball particle impact was analyzed in this study. And the shape variation of the cracks was investigated by stereo-microscope according to the impact velocity and steel ball diameter. In order to improve the damage reduction effect by $Cr_2O_3$ coating layer, crack size was measured and surface erosion state was observed for both of two kinds of specimen after impact experiment. And the results were compared with each other. The 4-point bending test was performed according to ASTM D790 testing method to evaluate the effect of coating layer for bending strength variation. As a result, it was found that the crack size of $Cr_2O_3$ coated specimen was smaller than that of uncoated one, because of the impact absorption by interior pores in the coating layer and the load dispersion by the structural characteristic of the coating layer. For the specimens subjected to the steel ball impact, the bending strength of coated specimen was higher than that of uncoated specimen.

• Journal of Microbiology and Biotechnology
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• 제23권12호
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• pp.1699-1707
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• 2013

During the fermentative production of 1,3-propanediol under high substrate concentrations, accumulation of intracellular 3-hydroxypropionaldehyde will cause premature cessation of cell growth and glycerol consumption. Discovery of oxidoreductases that can convert 3-hydroxypropionaldehyde to 1,3-propanediol using NADPH as cofactor could serve as a solution to this problem. In this paper, the yqhD gene from Klebsiella pneumoniae DSM2026, which was found encoding an aldehyde reductase (KpAR), was cloned and characterized. KpAR showed broad substrate specificity under physiological direction, whereas no catalytic activity was detected in the oxidation direction, and both NADPH and NADH can be utilized as cofactors. The cofactor binding mechanism was then investigated employing homology modeling and molecular dynamics simulations. Hydrogen-bond analysis showed that the hydrogen-bond interactions between KpAR and NADPH are much stronger than that for NADH. Free-energy decomposition dedicated that residues Gly37 to Val41 contribute most to the cofactor preference through polar interactions. In conclusion, this work provides a novel aldehyde reductase that has potential applications in the development of novel genetically engineered strains in the 1,3-propanediol industry, and gives a better understanding of the mechanisms involved in cofactor binding.

• 한국정보과학회논문지:데이타베이스
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• 제32권4호
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• pp.383-393
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• 2005

멀티미디어 데이타베이스에서 이미지를 검색하기 위해 공간관계를 이용하는 것은 비주얼한 인터페이스 시스템을 통해서 효율적으로 수행할 수 있다. 시스템에서 이미지의 객체들은 2D 스트링으로 표현되고, 이것은 이미지 내의 객체를 추상화 하는 방법으로 객체의 심볼릭 프로젝션을 통해서 생성된다. 그러나 2D 스트링 표현기법을 이용한 이미지 객체간의 공간관계는 정확하지 않기 때문에 3D 이미지를 검색할 때 정확도가 떨어진다. 이러한 문제점을 해결하기위해 본 논문에서는 3D 이미지를 위한 공간 연산자를 이용한 공간관계를 제안하고, 이미지의 공간관계에서 중복되는 부분을 제거하기 위해 여러 가지 추론규칙을 이용한다. 이러한 규칙을 기반으로 하는 추론기법은 내용을 이용해 이미지를 검색할 때 질의 처리 시스템에서 사용되고, 기존의 방법보다 정확도와 융통성이 높다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.195-198
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• 2002

Demand for high precision measurement of large area is increasing in many industrial fields. White-light Scanning Interferometer(WSI) is a well-known method for 3D profile measurement. However WSI has some limitations in a measurement range because of the sensing mechanism. Therefore, in this paper we use a heterodyne laser interferometer to get over the limitations of a short measurement range in WSI, We suggest a new WSI system combined with heterodyne laser interferometer. This system is aimed at eliminating Abbe error with measuring the focus point directly. With the use of triggering functionality of WSI, we can use this system as a probe of a precision stage such as a probe of CMM. The suggested system gives a repeatability of 87 nm in the absolute distance measurement test under the laboratory environment.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.929-932
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• 2002

As 3-D solid modeling systems have been widely used in product design recently, dedicated design systems for molds of the products have been developed and introduced to mold manufacturers. These mold design systems provide solid modeling capabilites for mechanism to free undercuts. This paper describes an algorithm for slide design capability that has been developed based on a commercial CAD system, Unigraphics. Since the relationship between slide parts were investigated and predefined using parameters in the system, the dimensions and locations of the parts are modifed automatically when a part is modified.

• Molecular & Cellular Toxicology
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• 제2권3호
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• pp.216-221
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• 2006

The cholinesterase-inhibiting organophosphorous (OP) compounds known as nerve agents are highly toxic. The principal toxic mechanism of OP compounds is the inhibition of acethylcholine esterase (AChE) by phosphorylation of its catalytic site. The reversible competitive inhibition of AChE may prevent the subsequent OP intoxication. In this study, three-dimensional quantitative structure-activity relationship (3D-QSAR) was performed to investigate the relationship between the 29 compounds with structural diversity and their bioactivities against AChE. In particular, predictive models were constructed using the comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). The results indicate reasonable model for CoMFA ($q^{2}=0.453,\;r^{2}=0.697$) and CoMSIA ($q^{2}=0.518,\;r^{2}=0.696$). The presence of steric and hydophobic group at naphtyl moiety of the model may lead to the design of improved competitive inhibitors for organophosphorous intoxication.