• Title/Summary/Keyword: 극성 선택

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Fabrication of semi-polar nano- and micro-scale GaN structures on the vertex of hexagonal GaN pyramids by MOVPE (MOVPE에 의한 GaN 피라미드 꼭지점 위의 반극성 나노/마이크로 크기의 GaN 성장)

  • Jo, Dong-Wan;Ok, Jin-Eun;Yun, Wy-Il;Jeon, Hun-Soo;Lee, Gang-Suok;Jung, Se-Gyo;Bae, Seon-Min;Ahn, Hyung-Soo;Yang, Min;Lee, Young-Cheol
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.21 no.3
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    • pp.114-118
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    • 2011
  • We report on the growth and characterization of nano and micro scale GaN structures selectively grown on the vertex of hexagonal GaN pyramids. $SiO_2$ near the vertex of hexagonal GaN pyramids was removed by optimized photolithgraphy process and followed by a selective growth of nano and micro scale GaN structures by metal organic vapor phase epitaxy (MOVPE). The pyramidal GaN nano and micro structures which have crystal facets of semi-polar {1-101} facets were formed only on the vertex of GaN pyramids and the size of the selectively grown nano and micro GaN structures was easily controlled by growth time. As a result of TEM measurement, Reduction of threading dislocation density was conformed by transmission electron microscopy (TEM) in the selectively grown nano and micro GaN structures. However, stacking faults were newly developed near the edge of $SiO_2$ film because of the roughness and nonuniformity in thickness of the $SiO_2$ film.

Study on the Selection of Solvent for Purificatino of p-Dioxanone by Crystallization Method (결정화에 의한 파라디옥산온의 정제를 위한 용매선정에 관한 연구)

  • kim, Sung-Il;Koh, Joo-young;Kim, Chul-Ung;Koh, Jae-Cheon;Park, So-Jin;Seo, Young-Jong;Choi, Byung-Ryul
    • Applied Chemistry for Engineering
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    • v.16 no.4
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    • pp.581-587
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    • 2005
  • In order to obtain a highly purified p-dioxanone (PDX) as monomer of biodegradable polymer, suitable solvent must be selected. The selection was based on the solubility of impurities, and partial layer melt crystallization were carried out under the presence of solvent. The solubility of PDX in various solvents such as ethyl acetate, tetrahydrofuran, acetone, alcohols (methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol) were measured over the temperature range of $-10{\sim}15^{\circ}C$. As solubility parameters, the mixing and dissolution enthalpy between the PDX and the solvents was studied based on empirical equations and the regular solution theory. The solubility and the temperature dependency of the solubility with the solvents of acetone, ethylacetate, and tetrahydrofuran of PDX were shown to have relatively high values compared to the alcohol type solvents. Also, in same alcohols, the smaller molecules and higher polarity gave higher solvency. In partial layer melt crystallization, small amount of ethylacetate selectively dissolved impurities and gave highly purified p-dioxanone, over 99.9% purity.

Study on CO2/N2 Mixture Gas Permeation Behavior through Polyethersulfone Membrane Treated by Plasma (플라즈마 처리된 폴리이써설폰 막의 CO2/N2 혼합가스의 투과거동에 대한 연구)

  • Park, Hee-Jin;Noh, Sang-Ho;Bae, Seong-Youl;Moon, Sei-Ki
    • Korean Chemical Engineering Research
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    • v.40 no.6
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    • pp.687-693
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    • 2002
  • The surface of polyethersulfone(PES) membrane treated by Ar, $NH_3$ plasma, and the effects were observed before and after the treatment. The membrane treated by Ar plasma was increased the O/C ratio and measured the hydrophilic group, and the one by $NH_3$ plasma was attached the amine group and the amino group. In addition, with the wettability of polyethersulfone membrane $CO_2$ and the polar functional groups of surface interacted increasingly. Thus by comparable increase of the soluble selectivity $CO_2$ to $N_2$ both the permeability and the selectivity of $CO_2$ was improved. The optimum condition for the $CO_2$ permeation and actual separation factor of the plasma treated membrane was as follows; the measurement of Ar-10 W-2 min plasma treatment was $13.19{\times}10^{-10}cm^3(STP)cm/cm^2{\cdot}s{\cdot}cmHg$ and 20.12, and the measurement of $NH_3$-50 W-2 min plasma treatment was $15.40{\times}10^{-10}cm^3(STP)cm/cm^2{\cdot}s{\cdot}cmHg$ and 20.06.

Programmed APTES and OTS Patterns for the Multi-Channel FET of Single-Walled Carbon Nanotubes (SWCNT 다중채널 FET용 표면 프로그램된 APTES와 OTS 패턴을 이용한 공정에 대한 연구)

  • Kim, Byung-Cheul;Kim, Joo-Yeon;An, Ho-Myoung
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.8 no.1
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    • pp.37-44
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    • 2015
  • In this paper, we have investigated a selective assembly method of single-walled carbon nanotubes (SWCNTs) on a silicon substrate using only photolithographic process and then proposed a fabrication method of field effect transistors (FETs) using SWCNT-based patterns. The aminopropylethoxysilane (APTES) patterns, which are formed for positively charged surface molecular patterns, are utilized to assemble and align millions of SWCNTs and we can more effectively assemble on a silicon (Si) surface using this method than assembly processes using only the 1-octadecyltrichlorosilane (OTS). We investigated a selective assembly method of SWCNTs on a Si surface using surface-programmed APTES and OTS patterns and then a fabrication method of FETs. photoresist(PR) patterns were made using photolithographic process on the silicon dioxide (SiO2) grown Si substrate and the substrate was placed in the OTS solution (1:500 v/v in anhydrous hexane) to cover the bare SiO2 regions. After removing the PR, the substrate was placed in APTES solution to backfill the remaining SiO2 area. This surface-programmed substrate was placed into a SWCNT solution dispersed in dichlorobenzene. SWCNTs were attracted toward the positively charged molecular regions, and aligned along the APTES patterns. On the contrary, SWCNT were not assembled on the OTS patterns. In this process, positively charged surface molecular patterns are utilized to direct the assembly of negatively charged SWCNT on SiO2. As a result, the selectively assembled SWCNT channels can be obtained between two electrodes(source and drain electrodes). Finally, we can successfully fabricate SWCNT-based multi-channel FETs by using our self-assembled monolayer method.

Development and validation of analytical methods for pyrifluquinazon residues determination on agricultural commodities by HPLC-UVD (HPLC-UVD를 이용한 농산물 중 pyrifluquinazon 잔류시험법 개발 및 검증)

  • Do, Jung-Ah;Kwon, Ji-Eun;Kim, Mi-Ra;Lee, Eun-Mi;Kuk, Ju-Hee;Cho, Yoon-Jae;Chang, Moon-Ik;Kwon, Kisung;Oh, Jae-Ho
    • Analytical Science and Technology
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    • v.26 no.3
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    • pp.174-181
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    • 2013
  • Pyrifluquinazon is classified with a quinazoline insecticide that regulates food intake by controling the feeding behavior acting on the endocrine or nervous system of pests such as aphids and white fly. To keep safety on pyrifluquinazon residues in agricultural commodities a simple, accurate and rapid analytical method was developed and validated using high performance liquid chromatograph (HPLC-UVD). The pyrifluquinazon residues acidified with 1% formic acid in samples were extracted with acetonitrile and partitioned with hexane subsequently to dichloromethane then purified with silica solid phase extraction (SPE) cartridge. The purified samples were detected using HPLC-UVD. The method was validated using apple and pear spiked with pyrifluquinazon at 0.02, 0.05 and 0.1 mg/kg and hulled rice, pepper, soybean at 0.05 and 0.1 mg/kg. Average recoveries were 70.5~107.9% with relative standard deviation less than 10%. The result of recoveries and overall coefficient of variation of a laboratory results in Gwangju regional FDA and Daejeon regional FDA was followed with Codex guideline (CODEX CAC/GL 40). This method is appropriated at pyrifluquinazon residues determination and will be used as official method of analysis.

Development and Validation of an Analytical Method for Ametoctradin Residue Determination in Domestic Agricultural Commodities by HPLC-PDA (HPLC-PDA를 이용한 국내 유통 농산물 중 ametoctradin 잔류량 분석법 개발 및 검증)

  • Do, Jung-Ah;Kwon, Ji-Eun;Lee, Eun-Mi;Kim, Mi-Ra;Kuk, Ju-Hee;Cho, Yoon-Jae;Kang, Il-Hyun;Kim, Hyung-Su;Kwon, Kisung;Oh, Jae-Ho
    • Korean Journal of Food Science and Technology
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    • v.45 no.3
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    • pp.285-292
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    • 2013
  • This study was carried out to validate the safety of ametoctradin residues in agricultural commodities by developing an official analysis method. An analytical method was developed and validated using HPLC-PDA detectors. The samples were extracted with methanol, subsequently partitioned with dichloromethane and purified with florisil column chromatograph using acetone/hexane (30/70, v/v) as solvent. The method was validated by using grape, hulled rice, mandarin, and potato spiked with ametoctradin at 0.05 and 5.0 mg/kg, and pepper at 0.05 and 2.0 mg/kg. Average recoveries were 76-114.8% with relative standard deviation less than 10%, and the limit of detection and limit of quantification were 0.0125 and 0.05 mg/kg, respectively. The result of recoveries and overall coefficient of variation of the laboratory results from Gwangju regional Food and Drug Administration (FDA) and Daejeon regional FDA was accorded with Codex Alimentarius Commission Guideline (CAC/GL 40). Based on these results, this method was found to be appropriate for ametoctradin residue determination and can be used as the official method of analysis.

Development of an Analytical Method for Fluxapyroxad Determination in Agricultural Commodities by HPLC-UVD (HPLC-UVD를 이용한 농산물 중 Fluxapyroxad 잔류분석법 개발)

  • Kwon, Ji-Eun;Kim, HeeJung;Do, Jung-Ah;Park, Hyejin;Yoon, Ji-Young;Lee, Ji-Young;Chang, Moon-Ik;Rhee, Gyu-Seek
    • Journal of Food Hygiene and Safety
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    • v.29 no.3
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    • pp.234-240
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    • 2014
  • Fluxapyroxad is classified as carboxamide fungicide that inhibits succinate dehydrogenase in complex II of mitochondrial respiratory chain, which results in inhibition of mycelial growth within the fungus target species. This study was carried out to assure the safety of fluxapyroxad residues in agricultural products by developing an official analytical method. A new, reliable analytical method was developed and validated using High Performance liquid Chromatograph-UV/visible detector (HPLC-UVD) for the determination of fluxapyroxad residues. The fluxapyroxad residues in samples were extracted with acetonitrile, partitioned with dichloromethane, and then purified with silica solid phase extraction (SPE) cartridge. Correlation coefficient($R^2$) of fluxapyroxad standard solution was 0.9999. The method was validated using apple, pear, peanut, pepper, hulled rice, potato, and soybean spiked with fluxapyroxad at 0.05 and 0.5 mg/kg. Average recoveries were 80.6~114.0% with relative standard deviation less than 10%, and limit of detection (LOD) and limit of quantification (LOQ) were 0.01 and 0.05 mg/kg, respectively. All validation parameters were followed with Codex guideline (CAC/GL 40). LC-MS (Liquid Chromatograph-Mass Spectrometer) was also applied to confirm the analytical method. Base on these results, this method was found to be appropriate fluxapyroxad residue determination and can be used as the official method of analysis.

Antiproliferative Effect of Extracts, Fractions and Compound from Vitex rotundifolia on Human Cancer Cells (순비기 나무(Vitex rotundifolia) 추출.분획물 및 화합물의 인체 암세포 증식억제 효과)

  • Kim, You-Ah;Lee, Jung-Im;Kim, Hae-Jin;Kong, Chang-Suk;Nam, Taek-Jeong;Seo, Young-Wan
    • Journal of Applied Biological Chemistry
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    • v.52 no.4
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    • pp.180-186
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    • 2009
  • Whole plants of Vitex rotundifolia were extracted for 2 days with methylene chloride ($CH_2Cl_2$) followed by extraction of the residue for an additional 2 days. The same procedure was also applied using methanol (MeOH). The two crude extracts were combined and partitioned between $CH_2Cl_2$ and $H_2O$. The organic layer was further partitioned between n-hexane and 85% aq. MeOH, and the aqueous layer was also further fractionated with n-BuOH and $H_2O$, successively. From the 85% aq. MeOH fraction, one compound was isolated through the repeated HPLC. According to the results of physicochemical data including NMR and MS, the chemical structure of the compound was determined as artemetin (1). The antiproliferative effects of the crude extracts, fractions, and compound against HT1080, AGS, MCF-7 and HT-29 human cancer cells were compared with the control by using MTT assay. In the comparative analysis, the 85% aq. MeOH fraction exhibited the strongest antiproliferative effects on human cancer cell lines in a dose-dependent manner (p<0.05). In addition, exposure of compound 1 isolated from 85% aq. MeOH fraction led to strong antiproliferative effect in HT1080 cancer cell lines. These results suggest that the extracts and compound isolated from V. rotundifolia may be used as potential chemopreventive and chemotherapeutic agents.

New Whitening Agent From Pimpinella brachycarpa (참나물추출물의 멜라닌 생성저해 효과)

  • Kim, Jin-Hwa;Sim, Gwan-Sub;Lee, Dong-Hwan;Lee, Geun-Soo;Lee, Bum-Chun;Pyo, Hyeong-Bae
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.33 no.3
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    • pp.203-208
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    • 2007
  • To develop a new whitening agent for cosmetics from natural products, Pimpinella brachcarpa was selected for its inhibitory effect on melanogenesis in B16 melanoma cells. Crude ethanolic extract of P. brachycarpa and its four fractions-hexane, ethyl acetate(EtOAc), butanol and aqueous were evaluated for antioxidative effects and tyrosinase inhibitory activity. To elucidate the mechanism of active compounds of P. brachycarpa, we investigated the changes in protein level of tyrosinase, TRP-1 and TRP-2 using Western blotting and the changes in mRNA level of tyrosinase using RT-PCR technique. Following UV irradiation, expression of ET-1 in HaCaT keratinocytes was measured by quantitative enzyme immunoassay(EIA) using human ET-1 antibody. Crude ethanolic extract of P. brachycarpa and its four fractions-hexane, EtOAc, butanol and aqueous had free radical scavenging effect by 87.2, 2.5, 97.2, 80.5, 49.8% at 100 ${\mu}g/mL$ and tyrosinase inhibitory effect by 18.3, 15.1, 55.4, 13.1, 0 % at 100 ${\mu}g/mL$. P. brachycarpa EtOAc fraction significantly inhibited melanin production in B16 melanoma cells. Treatment with P. brachycarpa extract for 72 h suppressed the biosynthesis of melanin up to 58 % at 100 ${\mu}g/mL$. Especially, the EtOAc fraction of P. brachycarpa reduced the tyrosinase activity and tyrosinase expression in B16 melanoma cells in a dose-dependent manner. mRNA levels of tyrosinase and TRP-1 were markedly reduced by the EtOAc fraction of P. brachycarpa. Moreover, at the concentrations of $12.5{\sim}50{\mu}g/mL$ of the fraction, the production of UV-induced ET-1 in HaCaT keratinocytes(24 h after 8 $mJ/cm^2$ UVB irradiation) was reduced about 40%(p<0.05). P. brachycarpa could be used as a new natural skin-whitening agent due to the inhibitory effect of on melanin biosynthesis and endothelin-1 expression.

A Morphological Analysis Method of Predicting Place-Event Performance by Online News Titles (온라인 뉴스 제목 분석을 통한 특정 장소 이벤트 성과 예측을 위한 형태소 분석 방법)

  • Choi, Sukjae;Lee, Jaewoong;Kwon, Ohbyung
    • The Journal of Society for e-Business Studies
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    • v.21 no.1
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    • pp.15-32
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    • 2016
  • Online news on the Internet, as published open data, contain facts or opinions about a specific affair and hence influences considerably on the decisions of the general publics who are interested in a particular issue. Therefore, we can predict the people's choices related with the issue by analyzing a large number of related internet news. This study aims to propose a text analysis methodto predict the outcomes of events that take place in a specific place. We used topics of the news articles because the topics contains more essential text than the news articles. Moreover, when it comes to mobile environment, people tend to rely more on the news topics before clicking into the news articles. We collected the titles of news articles and divided them into the learning and evaluation data set. Morphemes are extracted and their polarity values are identified with the learning data. Then we analyzed the sensitivity of the entire articles. As a result, the prediction success rate was 70.6% and it showed a clear difference with other analytical methods to compare. Derived prediction information will be helpful in determining the expected demand of goods when preparing the event.