• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.361.2-361.2
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• 2014

Transition metal dichalcogenides (MoS2, WS2, WSe2, MoSe2, NbS2, NbSe2, etc.) are layered materials that can exhibit semiconducting, metallic and even superconducting behavior. In the bulk form, the semiconducting phases (MoS2, WS2, WSe2, MoSe2) have an indirect band gap. Recently, these layered systems have attracted a great deal of attention mainly due to their complementary electronic properties when compared to other two-dimensional materials, such as graphene (a semimetal) and boron nitride (an insulator). However, these bulk properties could be significantly modified when the system becomes mono-layered; the indirect band gap becomes direct. Such changes in the band structure when reducing the thickness of a WS2 film have important implications for the development of novel applications, such as valleytronics. In this work, we report for the controlled synthesis of large-area (~cm2) single-, bi-, and few-layer WS2 using a two-step process. WOx thin films were deposited onto a Si/SiO2 substrate, and these films were then sulfurized under vacuum in a second step occurring at high temperatures ($750^{\circ}C$). Furthermore, we have developed an efficient route to transfer these WS2 films onto different substrates, using concentrated HF. WS2 films of different thicknesses have been analyzed by optical microscopy, Raman spectroscopy, and high-resolution transmission electron microscopy.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.356.1-356.1
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• 2014

The Isolation of few-layered transition metal dichalcogenides has mainly been performed by mechanical and chemical exfoliation with very low yields. in particular, the two-dimensional layer of molybdenum disulfide (MoS2) has recently attracted much interest due to its direct-gap property and potential application in optoelectronics and energy harvesting. However, the synthetic approach to obtain high-quality and large-area MoS2 atomic thin layers is still rare. In this account, a controlled thermal reduction-sulfurization method is used to synthesize large-MoOx thin films are first deposited on Si/SiO2 substrates, which are then sulfurized (under vacuum) at high temperatures. Samples with different thicknesses have been analyzed by Raman spectroscopy and TEM, and their photoluminescence properties have been evaluated. We demonstrated the presence of mono-, bi-, and few-layered MoS2 on as-grown samples. It is well known that the electronic structure of these materials is very sensitive to the number of layer, ranging from indirect band gap semiconductor in the bulk phase to direct band gap semiconductor in monolayers. This synthetic approach is simple, scalable, and applicable to other transition metal dichalcogenides. Meanwhile, the obtained MoS2 films are transferable to arbitrary substrates, providing great opportunities to make layered composites by stacking various atomically thin layers.

• 한국수산과학회지
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• 제44권2호
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• pp.104-110
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• 2011

This study was conducted to improve the food functional and sensory food quality of Hizikia fusiforme by the fermentation of lactic acid bacteria. Seven strains of lactic acid bacteria isolated from traditional Korean fermented food were inoculated and cultivated in H. fusiforme water extract. Among them, Lactobacillus brevis LB-20, isolated from Kimchi, was selected for further study by considering the results of bacterial growth, DPPH radical scavenging activity, and sensory evaluation. No significant differences in proximate compositions (moisture, crude protein, crude fat, and crude ash) were observed by the fermentation of L. brevis LB-20. The most dramatical change was the conversion from glutamate to ${\gamma}$-aminobutyric acid (GABA) in H. fusiforme water extract fermented by L. brevis LB-20. The GABA content increased approximately 60-fold after 48 hr of fermentation. The bacterial fermentation also resulted in low-molecularization of the extract. The particle size of the fermented extract became approximately 4-fold smaller than that of the law extract. In addition, the analysis of volatile flavor compounds using GC/MS revealed that the bacterial fermentation dramatically removed off-flavors such as acetaldehyde, haxanal, diallyl disulphide and 1-penten-2-ol in the H. fusiforme extract.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 1999년도 IFSCC . ASCS 학술대회 발표 논문
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• pp.1-5
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• 1999

The purpose of this study was to determine the effect of IPBC(3-lodo-2-propynylbutyl carbamate) on dandruff caused by the anthropophilic fungus Maiassezia furfur. The effects of IPBC on dandruff were examined by evaluating (a) the MIC value of IPBC using broth dilution method : (b) the remnant antimicrobial activity of IPBC containing shampoo on skin disc ; (c) the antidandruff efficacy of 1.0 % IPBC containing shampoo in double blind clinical trial. To investigate the remnant antimicrobial activity of IPBC against Maiassezia furfur, guinea pig-skin disc was washed with antidandruff shampoo and then the diameter of inhibition zone per disc was measured. For clinical trial, thirty healthy volunteers, aged 25-35, participated in 4 week study. At 0,2,4 weeks, examinations of scaling, itching on scalp were carried out. The MIC(Minimun Inhibition Concentration) values of IPBC range from 0.10 to 1.00$\mu$ g/ml and it seems that IPBC is more effective in the MIC values than zinc pyrithione, selenium disulphide, piroctone olamine and comparable to ketoconazole, climbazole. When the rimnant antimicrobial activity of IPBC shampoo on skin disc was determined, 0.5% IPBC shampoo and 2.0% Ketoconazole shampoo resulted in similar antimicrobial effect. In addition, 1.0%,2.0% IPBC shampoo was more effective than 2.0% ketoconazole shampoo. After two and four-weeks of 1.0% IPBC shampoo treatment, there was significant reduction of scaling, itching in test group compared to control group. On the basis of these results, it can be concluded that 1.0% IPBC is more effective than 2.0% Ketoconazole in reducing dandruff. It seems that strong capacity of drug binding to the stratum corneum plays a role in its antidandruff effect since adsorption of active ingredients on scalp is very important factor in reducing dandruff.

• 플랜트 저널
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• 제13권3호
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• pp.36-46
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• 2017

황회수 공정의 연소반응기 안에서는 평형반응 및 kinetic 반응이 동시에 일어난다. 주요 kinetic 반응에 참여하는 성분들은 수소($H_2$), 일산화탄소(CO), 카보닐황화물(COS) 그리고 이황화탄소($CS_2$) 이다. 본 연구에서는 평형반응, 상관관계식(empirical correlations) 그리고 황 회수 공정의 라이센서 자료의 비교를 통해 반응기에서 kinetic components (COS와 $CS_2$)의 생성 양을 분석한다. 또한 kinetic components ($H_2$ 와 CO)의 생성 양의 분석을 통해 반응기에서의 생성 양과 온도와의 상관관계를 분석한다. 부 반응이 전체 연소에 필요로 하는 산소의 양에 어떤 영향을 미치는지도 같이 분석을 한다. 황회수 공정의 반응기내의 부 반응에 대한 충분한 이해는 전체 황회수 공정 설계를 할 때 최적의 장치 설계를 가능하게 하고 나아가 황회수 효율을 극대화 하는데 도움이 된다.

• International Journal of Industrial Entomology and Biomaterials
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• 제9권2호
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• pp.167-171
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• 2004

We constructed an oligo-d(T) primed directional cDNA library from the Bombyx mandarina whole larvae. In an effort to isolate genes expressed in the B. mandarina, 227 expressed sequence tags (ESTs) were generated by single-pass sequencing from the cDNA library. Sequence analysis showed that 107 clones (47.1%) were classified into known genes and 120 clones (52.9%) were novel transcripts, which are unknown for their function. Of the 107 known genes, the most abundant gene was found to be actin and followed by serine protease in the expression profile. Among these clones, a serine protease homolog (BmSP) which is a class of proteolytic enzymes isolated. Full-length sequence of the BmSP cDNA clone was 922 bp in length and has an open reading frame of 276 amino acids. The conserved histidine, aspatic acid and serine residues forming the catalytic center as well as cysteine residues contributing to three disulphide bonds also were found in Bmsp gene. mRNA expression analysis revealed a high and specific expression of the gene only in midgut tissue, suggesting that BmSP gene is closely associated with the expression of digestive enzyme.

• 대한미생물학회지
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• 제12권1호
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• pp.19-32
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• 1977

계난백(鷄卵白) Lysozyme N-와 C 말단(末端) 항원결정기(抗原決定基)($P_{17}$: sequence $Lys^1-{cys-}^6-Asn^{27},\;{Trp^{12}}_2-Cys^{127}-Leu^{129}$)의 특이성(特異性)에 대(對)하여 연구(硏究)했다. $^{14}C-acetyl$ Lysozyme 과 정제(精製)한 guinea pig 항(抗)-$P_{17}$ 항체(抗體)와의 결합(結合)을 Scatchard plot 상(上)에서 나타낸 결과(結果) 그 실험치(實驗値)가 거의 r=1였다. 이것은 Lysozyme에 대(對)하여 각각(各各) 다른 친화성(親和性)을 가진 2개(個)의 항체군(抗體群)의 존재(存在)나 그렇잖으면 제(第)1의 항체결합부위(抗體結合部位)에 최초(最初)의 Lysozyme 분자(分子)가 결합(結合)함으로 인(因)하여 항체분자(抗體分子)의 제(第)2의 결합부위(結合部位)에 다른 Lysozyme 분자(分子)의 결합(結合)을 방해하는 즉 steric hindrance에 의한 가능성(可能性)을 시사(示唆)한다. 여러가지 peptides의 항원활성(抗原活性)을 $^{14}C-acetyl-P_{17}$과 항(抗)-$P_{17}$ 항체(抗體)와의 결합저해(結合沮害)시험에서 측정(測定)했다. 그 결과(結果) 단지 $P_{17}$과 $P_{17}t$(sequence $Lys^1-cys^5-Homoser^{12},\;Trp^{123}-cys^{127}-Leu^{128})$)만이 억제되었고 그 $K_1$치(値)가 각각(各各) $2.0{\times}10^4$과 $8.1{\times}10^3$이였다. 이들 결과(結果)를 종합(綜合)하면 $P_{17}$의 항(抗)-$P_{17}$ 항체(抗體)와의 직접적 결합부위(結合部位)는 $P_{17}$의 말단부위(末端部位)에 국재(局在)해 있는 것을 암시해 준다. 한편 $P_{17}$의 나머지 부분(部分)은 이 항원결정기(抗原決定基) 구조(構造)를 유지(維持)하는데 중요(重要)한 역할(役割)을 할 것으로 생각되며 또한 이 결정기내(決定基內)의 한 개의 disulphide 결합(結合)은 면역학적(免疫學的) 활성(活性)을 나타내는데 필수적(必須的)인 것으로 믿어진다.

• 한국생물정보학회:학술대회논문집
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• 한국생물정보시스템생물학회 2005년도 BIOINFO 2005
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• pp.325-330
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• 2005

We are generally interested in the analysis, detection and prediction of structural motifs in proteins, in order to infer compatibility of amino acid sequence to structure in proteins of known three-dimensional structure available in the Protein Data Bank. In this context, we are analyzing some of the well-characterized structural motifs in proteins. We have analyzed simple structural motifs, such as, ${\beta}$-turns and ${\gamma}$-turns by evaluating the statistically significant type-dependent amino acid positional preferences in enlarged representative protein datasets and revised the amino acid preferences. In doing so, we identified a number of ‘unexpected’ isolated ${\beta}$-turns with a proline amino acid residue at the (i+2) position. We extended our study to the identification of multiple turns, continuous turns and to peptides that correspond to the combinations of individual ${\beta}$ and ${\gamma}$-turns in proteins and examined the hydrogen-bond interactions likely to stabilize these peptides. This led us to develop a database of structural motifs in proteins (DSMP) that would primarily allow us to make queries based on the various fields in the database for some well-characterized structural motifs, such as, helices, ${\beta}$-strands, turns, ${\beta}$-hairpins, ${\beta}$-${\alpha}$-${\beta}$, ${\psi}$-loops, ${\beta}$-sheets, disulphide bridges. We have recently implemented this information for all entries in the current PDB in a relational database called ODSMP using Oracle9i that is easy to update and maintain and added few additional structural motifs. We have also developed another relational database corresponding to amino acid sequences and their associated secondary structure for representative proteins in the PDB called PSSARD. This database allows flexible queries to be made on the compatibility of amino acid sequences in the PDB to ‘user-defined’ super-secondary structure conformation and vice-versa. Currently, we have extended this database to include nearly 23,000 protein crystal structures available in the PDB. Further, we have analyzed the ‘structural plasticity’ associated with the ${\beta}$-propeller structural motif We have developed a method to automatically detect ${\beta}$-propellers from the PDB codes. We evaluated the accuracy and consistency of predicting ${\beta}$ and ${\gamma}$-turns in proteins using the residue-coupled model. I will discuss results of our work and describe databases and software applications that have been developed.

• BMB Reports
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• 제37권3호
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• pp.304-313
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• 2004

Three-dimensional (3D) models for the 65-kDa activated Cry4A and Cry4B $\delta$-endotoxins from Bacillus thuringiensis subsp. israelensis that are specifically toxic to mosquito-larvae were constructed by homology modeling, based on atomic coordinates of the Cry1Aa and Cry3Aa crystal structures. They were structurally similar to the known structures, both derived 3D models displayed a three-domain organization: the N-terminal domain (I) is a seven-helix bundle, while the middle and C-terminal domains are primarily comprise of anti-parallel $\beta$-sheets. Circular dichroism spectroscopy confirmed the secondary structural contents of the two homology-based Cry4 structures. A structural analysis of both Cry4 models revealed the following: (a) Residues Arg-235 and Arg-203 are located in the interhelical 5/6 loop within the domain I of Cry4A and Cry4B, respectively. Both are solvent exposed. This suggests that they are susceptible to tryptic cleavage. (b) The unique disulphide bond, together with a proline-rich region within the long loop connecting ${\alpha}4$ and ${\alpha}5$ of Cry4A, were identified. This implies their functional significance for membrane insertion. (c) Significant structural differences between both models were found within domain II that may reflect their different activity spectra. Structural insights from this molecular modeling study would therefore increase our understanding of the mechanic aspects of these two closely related mosquito-larvicidal proteins.

• 한국재료학회지
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• 제27권12호
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• pp.705-709
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• 2017

The electronic and optical characteristics of molybdenum disulphide ($MoS_2$) film significantly vary with its thickness, and thus a rapid and accurate estimation of the number of $MoS_2$ layers is critical in practical applications as well as in basic researches. Various existing methods are currently available for the thickness measurement, but each has drawbacks. Transmission electron microscopy allows actual counting of the $MoS_2$ layers, but is very complicated and requires destructive processing of the sample to the point where it will no longer be useable after characterization. Atomic force microscopy, particularly when operated in the tapping mode, is likewise time-consuming and suffers from certain anomalies caused by an improperly chosen set point, that is, free amplitude in air for the cantilever. Raman spectroscopy is a quick characterization method for identifying one to a few layers, but the laser irradiation causes structural degradation of the $MoS_2$. Optical microscopy works only when $MoS_2$ is on a silicon substrate covered with $SiO_2$ of 100~300 nm thickness. The last two optical methods are commonly limited in resolution to the micrometer range due to the diffraction limits of light. We report here a method of measuring the distribution of the number of $MoS_2$ layers using a low voltage field emission electron microscope with acceleration voltages no greater than 1 kV. We found a linear relationship between the FESEM contrast and the number of $MoS_2$ layers. This method can be used to characterize $MoS_2$ samples at nanometer-level spatial resolution, which is below the limits of other methods.