• 생명과학회지
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• 제15권5호
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• pp.772-778
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• 2005

광학활성 에폭사이드는 광학활성 의약품, 기능성 식품 제조용 광학활성 중간체로 사용될 수 있다. 바이오촉매를 이용하여 광학활성 에폭사이드를 제조하는 방법으로는, mono-oxygenase나 peroxidase 등을 이용하여 알켄 기질의 이중결합을 비대칭 에폭시화반응을 통해 제조하는 방법이 있다. Kinetic resolution을 이용하는 방법으로는 epoxide hydrolase를 이용하여 특정 이성질체만을 diol로 가수분해하여 제거시켜 광학활성 에폭사이드를 얻는 방법 등이 있다. 다양한 생물전환 기술, directed evolution 및 site-specific muta-genesis 등을 이용한 광학활성 에폭사이드 제조용 바이오촉매개량 기술 등 효율적인 광학활성 에폭사이드 제조 시스템에 대한 연구 개발도 활발히 진행되고 있어 향후에 상업화가 가능할 것으로 기대된다.

• IMMUNE NETWORK
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• 제12권5호
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• pp.176-180
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• 2012

Although the majority of research on CD137 has been directed to T cells, it is becoming clear that this molecule has distinct functions in other lineages of cells, including non-hematopoietic cells. In particular, emerging evidence suggests that the CD137-its ligand (CD137L) network involving immune cells and non-immune cells, directly or indirectly regulates inflammation in both positive and negative manners. Bidirectional signaling through both CD137 and CD137L is critical in the evolution of inflammation: 1) CD137L signaling plays an indispensible role in the activation and recruitment of neutrophils by inducing the production of proinflammatory cytokines and chemokines in hematopoietic and non-hematopoietic cells such as macrophages, endothelial cells and epithelial cells; 2) CD137 signaling in NK cells and T cells is required for their activation and can influence other cells participating in inflammation via either their production of proinflammatory cytokines or engagement of CD137L by their cell surface CD137: 3) CD137 signaling can suppress inflammation by controlling regulatory activities of dendritic cells and regulatory T cells. As recognition grows of the role of dysregulated CD137 or CD137L stimulation in inflammatory diseases, significant efforts will be needed to develop antagonists to CD137 or CD137L.

• 한국지능정보시스템학회:학술대회논문집
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• 한국지능정보시스템학회 2001년도 The Pacific Aisan Confrence On Intelligent Systems 2001
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• pp.151-155
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• 2001

Mobile agent technology has been the subject of much attention in the last few years, mainly due to the proliferation of distributed software technologies combined with the distributed AI research field. In this paper, we present a design of communication networks of agents that cooperate with each other for forwarding messages to the specific mobile agent in order to make the overall system location transparent. In order to make the material accessible to general intelligent system researchers, we present the general ideas abstractly in terms of the graph theory. In particular, a proxy network is defined as a directed acyclic graph satisfying some structural conditions. In turns out that the definition ensures some kind of reliability of the network, in the sense that as long as at most one proxy agent is abnormal, there agent exists a communication path, from every proxy agent to the target agent, without passing through the abnormal proxy. As the basis for the implementation of this scheme, an appropriate initial proxy network is specified and the dynamic nature of the network is represented by a set of graph transformation rules. It is shown that those rules are sound, in the sense that all graphs created from the initial proxy network by zero or more applications of the rules are guaranteed to be proxy networks. Finally, we will discuss some implementation issues.

• Journal of Microbiology and Biotechnology
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• 제19권12호
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• pp.1536-1541
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• 2009

The DNA shuffling technique has been used to generate libraries of evolved enzymes in thermostability. We have shuffled two thermostable cytidine deaminases (CDAs) from Bacillus caldolyticus DSM405 (T53) and B. stearothermophilus IFO12550 (T101). The shuffled CDA library (SH1067 and SH1077 from the first round and SH2426 and SH2429 from the second round) showed various patterns in thermostability. The CDAs of SH1067 and SH1077 were more thermostable than that of T53. SH2426 showed 150% increased halftime than that of T53 at $70^{\circ}C$. The CDA of SH2429 showed about 200% decreased thermostability than that of T53 at $70^{\circ}C$. A single amino acid residue replacement that presented between SH1077 and SH2429 contributed to dramatic changes in specific activity and thermostability. On SDS-PAGE, the purified CDA of SH1077 tetramerized, whereas that of SH2429 denatured and became almost monomeric at $80^{\circ}C$. A simulated three-dimensional structure for the mutant CDA was used to interpret the mutational effect.

• Journal of Microbiology and Biotechnology
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• 제20권12호
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• pp.1696-1701
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• 2010

The ${\alpha}$-amylases activity was improved by random mutagenesis and screening. A region comprising residues from the position 34-281 was randomly mutated in B. licheniformis ${\alpha}$-amylase (AmyL), and the library with mutations ranging from low, medium, and high frequencies was generated. The library was screened using an effective liquid-phase screening method to isolate mutants with an altered pH profile. The sequencing of improved variants indicated 2-5 amino acid changes. Among them, mutant TP8H5 showed an altered pH profile as compared with that of wild type. The sequencing of variant TP8H5 indicated 2 amino acid changes, Ile157Ser and Trp193Arg, which were located in the solvent accessible flexible loop region in domain B.

• Genomics & Informatics
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• 제12권4호
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• pp.276-282
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• 2014

The disease tuberculosis, caused by Mycobacterium tuberculosis (MTB), remains a major cause of morbidity and mortality in developing countries. The evolution of drug-resistant tuberculosis causes a foremost threat to global health. Most drug-resistant MTB clinical strains are showing resistance to isoniazid and rifampicin (RIF), the frontline anti-tuberculosis drugs. Mutation in rpoB, the beta subunit of DNA-directed RNA polymerase of MTB, is reported to be a major cause of RIF resistance. Amongst mutations in the well-defined 81-base-pair central region of the rpoB gene, mutation at codon 450 (S450L) and 445 (H445Y) is mainly associated with RIF resistance. In this study, we modeled two resistant mutants of rpoB (S450L and H445Y) using Modeller9v10 and performed a docking analysis with RIF using AutoDock4.2 and compared the docking results of these mutants with the wild-type rpoB. The docking results revealed that RIF more effectively inhibited the wild-type rpoB with low binding energy than rpoB mutants. The rpoB mutants interacted with RIF with positive binding energy, revealing the incapableness of RIF inhibition and thus showing resistance. Subsequently, this was verified by molecular dynamics simulations. This in silico evidence may help us understand RIF resistance in rpoB mutant strains.

• 대한산업공학회지
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• 제18권1호
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• pp.105-120
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• 1992

An expert system was developed as a framework of integrating diverse and multifactored ergonomic knowledge to investigate its effectiveness in ergonomic workplace design and evolution. Although numerous computer-assisted approaches have been made to overcome the lack of integrated design principles, those models being used require very specific information of various design activities that may not be available in the design stage. On the other hand, an expert system would be an effective design aid that is capable of guiding the designer to solve a problem. However, most expert systems lack detailed evaluation capabilities due to a qualitative nature of inference mechanisms. Furthermore, those approaches were independently developed, focusing mostly on a single aspect such as biomechanics, physiology, etc. In this paper, a design framework was developed which takes advantage of expert system metholologies, a relational data base and existing ergonomic models. The pattern-directed, rule-based expert system allows the designer to gradually formulate and subsequently evaluate workplace design. A comprehensive and modularized knowledge base was built incorporating biomechanics, physiology and psychophysics, which is, in turn, capable of accessing not only qualitative knowledge but complex analytic evaluation models and massive information in the data base through an interface. A conflict resolution strategy using multiple criteria decision-making schemes was also employed to reconcile multiple design alternatives.

• Animal Systematics, Evolution and Diversity
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• 제36권3호
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• pp.251-257
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• 2020

The genus Plectus Bastian, 1865 represents a group of free-living freshwater nematodes belonging to the family Plectidae Örley, 1880. However, only one species has been reported thus far from Korea. Plectus aquatilis Andrássy, 1985 and Plectus cirratus Bastian, 1865 are reported for the first time from Korea, from sediments collected from the Nakdong River. Plectus aquatilis is distinguished from other Plectus species by its three longitudinal alae in the lateral field, thin and directed cephalic setae, continuous lip region (head not set-off), and rectangular shaped tail. Plectus cirratus is distinguished from other Plectus species by its large body, two longitudinal alae in the lateral field, larger stoma, and longer tail. Morphological characters and measurements of the specimens generally agree with the original descriptions of Plectus species. Here, the morphological characters (detailed morphometrics) of two species in the genus Plectus are fully redescribed and illustrated using optical microscopy. DNA barcode sequence information from the 18S rDNA gene is also provided for molecular species identification and compared with sequences from other Plectus species available on GenBank.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.688-706
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• 2024

Austenitic stainless steels (ASS) are extensively employed in various sectors such as nuclear, power, petrochemical, oil and gas because of their excellent structural strength and resistance to corrosion. SS304 and SS316 are the predominant choices for piping, pressure vessels, heat exchangers, nuclear reactor core components and support structures, but they are susceptible to stress corrosion cracking (SCC) in chloride-rich environments. Over the course of several decades, extensive research efforts have been directed towards evaluating SCC using diverse methodologies and models, albeit some uncertainties persist regarding the precise progression of cracks. This review paper focuses on the application of Acoustic Emission Technique (AET) for assessing SCC damage mechanism by monitoring the dynamic acoustic emissions or inelastic stress waves generated during the initiation and propagation of cracks. AET serves as a valuable non-destructive technique (NDT) for in-service evaluation of the structural integrity within operational conditions and early detection of critical flaws. By leveraging the time domain and time-frequency domain techniques, various Acoustic Emission (AE) parameters can be characterized and correlated with the multi-stage crack damage phenomena. Further theories of the SCC mechanisms are elucidated, with a focus on both the dissolution-based and cleavage-based damage models. Through the comprehensive insights provided here, this review stands to contribute to an enhanced understanding of SCC damage in stainless steels and the potential AET application in nuclear industry.

• 한국정보과학회논문지:소프트웨어및응용
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• 제28권9호
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• pp.669-680
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• 2001

유전자 알고리즘(GA:Genetic Algorithm)은 최적화 문제를 풀기 위해 생물학적 진화(evolution) 과정을 모방한 최적화 알고리즘이다. 유전자 알고리즘은 복잡한 상태 공간에서 최적 해를 찾기 위해 전통적인 최적화 기법과는 달리 유향적 임의 탐색을 행한다. 학습에 해당하는 국부 탐색(local search)을 유전적 알고리즘은 exploration 탐색과 exploitation 탐색의 균형을 유지시켜 줄 수 있는 한 방법이다. 모집단 내의 각 개체가 진화 과정 중에 학습한 유전적 특질들은 그 다음 세대에서 되물림 되며 이러한 학습(learning) 과정을 유전자 알고리즘과 결합시킴으로써 탐색 속도의 향상을 기대할 수 있다. 이 논문에서는 함수 최적화를 위해 속도를 개선한 셀룰러 학습을 기반으로 하는 유전자 알고리즘을 제안한다. 제안하는 셀룰러 학습 전략은 셀룰러 오토마타의 주기성과 수렴성을 기반으로 하며, 유기체가 그 개체의 생명 주기의 한 세대에서 얻게되는 지식과 경험들을 자손에게 전달한다는 이론을 바탕으로 한다. 제안한 셀룰러 학습 전략의 효율을 기존의 복합 유전자 알고리즘에서의 라마키안 진화 및 볼드윈 효과와 비교하였다. 다양한 테스트 베드 함수에 대한 실험을 통하여 셀룰러 학습에 의한 개체의 국부적 향상이 전체적인 성능 향상에 기여함을 알 수 있었고 제안한 학습 전략이 기존의 방법보다 더 빨리 전역 최적 해를 찾을 수 있음을 증명하였다.