• 한국자기학회:학술대회 개요집
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• 한국자기학회 2010년도 임시총회 및 하계학술연구발표회
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• pp.79-79
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• 2010

Semimetallic bismuth (Bi) has been extensively investigated over the last decade since it exhibits very intriguing transport properties due to their highly anisotropic Fermi surface, low carrier concentration, long carrier mean free path l, and small effective carrier mass $m^*$. In particular, the great interest in Bi nanowires lies in the development of nanowire fabrication methods and the opportunity for exploring novel low-dimensional phenomena as well as practical application such as thermoelectricity[1]. In this work, we introduce a self-assembled interconnection of nanostructures produced by an on-film formation of nanowires (OFF-ON) method in order to form a highly ohmic Bi nanobridge. A Bi thin film was first deposited on a thermally oxidized Si (100) substrate at a rate of $40\;{\AA}/s$ by radio frequency (RF) sputtering at 300 K. The sputter system was kept in an ultra high vacuum (UHV) of $10^{-6}$ Torr before deposition, and sputtering was performed under an Ar gas pressure of 2m Torr for 180s. For the lateral growth of Bi nanowires, we sputtered a thin Cr (or $SiO_2$) layer on top of the Bi film. The Bi thin films were subsequently put into a custom-made vacuum furnace for thermal annealing to grow Bi nanowires by the OFF-ON method. After thermal annealing, the Bi nanowires cannot be pushed out from the topside of the Bi films due to the Cr (or $SiO_2$) layer. Instead, Bi nanowires grow laterally as a mean s of releasing the compressive stress. We fabricated a self-assembled Bi nanobridge (d=192 nm) device in-situ using OFF-ON through annealing at $250^{\circ}C$ for 10hours. From I-V measurements taken on the Bi nanobridge device, contacts to the nanobridge were found highly ohmic. The quality of the Bi nanobridge was also proved by the high MR of 123% obtained from transverse MR measurements. These results manifest the possibility of self-assembled nanowire interconnection between various nanostructures for a variety of applications and provide a simple device fabrication method to investigate transport properties on nanowires without complex patterning and etching processes.

• Journal of Dairy Science and Biotechnology
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• 제33권1호
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• pp.27-34
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• 2015

본 연구에서는 dispersive-SPE를 사용하여 간편하고, 신속하며, 경제적인 우유 내 19종 잔류농약의 동시 다성분 분석법을 설정하고자 하였다. Liquid-liquid partitioning method와 low-temperature cleanup method를 적용한 추출방법과 PSA 및 PSA + C18의 sorbent가 사용된 dispersive-SPE를 사용한 정제방법을 비교 실험하였으며, GC/MS의 선택이온 검색법(selected ion monitoring, SIM)으로 정량 분석하였다. matrix-matched standards와 matrix-free standards를 사용하여 분석방법의 matrix enhancement effect를 확인하였고, 분석방법 설정을 위한 비교실험의 결과, low-temperature cleanup 방법으로 추출하여 dispersive-SPE(PSA + C18)로 정제하는 방법이 시료 추출물의 간섭물질을 제거하는데 가장 효과적이고, 첨가한 $1{\mu}g/mL$에 대한 개별 농약 성분의 회수율 또한 전체적으로 가장 높은 수준을 나타내었으며, 모든 농약 성분의 RSD(%)가 20% 이하로서 기준에 적합한 재현성을 나타내었다.

• 환경위생공학
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• 제7권2호
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• pp.95-110
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• 1992

Much progress has been made in understanding the subcellular events of the human lung injuries after acute exposure to environmental air pollutants. Host of those events represent oxidative damages mediated by reactive oxygen species such as superoxide, hydrogen peroxide, and the hydroxy, free radical. Recently, nitric oxide (NO) was found to be endogenously produced by endothelial cells and cells of the reticulo-endothelial system as endothelialderived relaxation factor (EDRF) which is a vasoactive and neurotransmitter substance. Together with superoxide, NO can form another strong oxidant, peroxonitrite. The relative importance of exogenous sources of $N0/N0_2$ and endogenous production of NO by the EDRF producing enzymes in the oxidative stresses to the heman lung has to be elucidated. The exact events leading to chronic irreversible damage are still yet to be known. From chronic exposure to oxidant gases, progressive epithelial and interstitial damages develop. Type I epithelial cells become thicker and cover a smaller average alveolar surface area while thee II cells proliferate instead. Under acute damages, the extent of loss of the alveolar epithelial cell lining, especially type II cells appears to be a good predictor of the ensuing irreversible damage to alveolar compartment. Interstitial matrix undergo remodeling during chronic exposure with increased collagen fibers and interstitial fibroblasts. However, Inany of these changes can be reversed after cessation of exposure. Among chronic lung injuries, genetic damages and repair responses received particular attention in view of the known increased lung cancer risks from exposure to several air pollutants. Heavy metals from foundry emission, automobile traffics, and total suspended particulate, especially polycystic aromatic hydrocarbons have been positively linked with the development of lung cancer. Asbestos in another air pollutant with known risk of lung cancer and mesothelioma, but asbestos fibers are nonauthentic in most bioassays. Studies using the electron spin resonance spin trapping method show that the presence of iron in asbestos accelerates the production of the hydroxy, radical in vitro. Interactions of these reactive oxygen species with particular cellular components and disruption of cell defense mechanisms still await further studies to elucidate the carcinogenic potential of asbestos fibers of different size and chemical composition. The distribution of inhaled pollutants and the magnitude of their eventual effects on the respiratory tract are determined by pollutant-independent physical factors such as anatomy of the respiratory tract and level and pattern of breathing, as well as by pollutant-specific phyco-chemical factors such as the reactivity, solubility, and diffusivity of the foreign gas in mucus, blood and tissue. Many of these individual factors determining dose can be quantified in vitro. However, mathematical models based on these factors should be validated for its integrity by using data from intact human lungs.

• 한국식품영양학회지
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• 제10권2호
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• pp.145-150
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• 1997

본 연구는 유자과즙과 유자를 이용한 제품개발시 기초자료로서의 활용을 목적으로, 생유자를 벨트식 착즙법9)으로 착즙한 유자 과즙(Sample I)과 이를 5$^{\circ}C$에서 1년간 저장한 유자 과즙(Sample II)의 품질특성을 비교 분석한 결과, Sample II는 Sample I에 비하여 수분은 3% 정도의 증가를 보였고, soluble solid가 1$^{\circ}$brix 이상 감소되었다. pH는 2.68에서 2.84로 증가하면서 산도가 5.83에서 5.23으로 감소되었다. 비타민 C는 50% 이상 감소하였고, 총아민산 및 유리아미노산의 함량은 약 20~30% 정도의 감소를 보였으나, 그 밖의 일반성분들과 유리당, 지방산 및 총아미노산 함량의 감소는 0.1~1.0% 정도로 변화 정도가 미미하였다. 그리고, Sample I과 II의 향기성분을 gas chromatograpy로 비교 분석한 결과, 분리된 peak의 수는 70여 개인데, mass spectrometer로 확인할 수 있는 성분은 13개에 불과하였고, 주된 향기성분은 탄화수소류로 limonene, terpinene, terpineol, terpinolene 등이다. 1년간 저장함에 따라서 향기성분은 약 30~50% 정도 감소되고, 미량 함유되어 있던 성분들은 거의 소실되는 것으로 나타났으나, Sample I 및 II로 10% 희석음료로 제조하여 관능검사한 결과 당배합비 및 저장기간에 따른 유의차는 거의 나타나지 않았다.

• Asian-Australasian Journal of Animal Sciences
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• 제31권10호
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• pp.1635-1642
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• 2018

Objective: This study was conducted to evaluate the effects of Rhus succedanea extract addition on in vitro ruminal fermentation and microbial growth. Methods: Two ruminally-fistulated steers consuming 600 g/kg timothy- and 400 g/kg cracked corn-based concentrate with free access to water and mineral block were used as rumen fluid donors. In vitro batch fermentation, with timothy as a substrate, was conducted for up to 72 h, with Rhus succedanea extracts added to achieve final concentrations of 0, 10, 30, 50, 70, and 90 mg/L. Results: Effective dry matter (DM) degradability rate linearly decreased (p = 0.046) depending on extract dosing levels. Total gas production after 24 to 72 h incubation tended to decrease following extract addition, beginning with 50 mg/L starting dose (significance of quadratic effects: p = 0.006, p<0.001, and p = 0.008 for 24, 48, and 72 h, respectively). Methane production decreased depending on dosing levels following 24 h (p<0.05) and 48 h (p<0.005) incubations and was the lowest with the 50 mg/L dose. The Rhus succedanea extracts increased the abundance of Fibrobacter succinogenes (p<0.05) and Ruminococcus flavefaciens (p = 0.0597) and decreased the abundance of methanogenic archaea (p<0.05) following 24 h incubation. Conclusion: Rhus succedanea was shown to reduce methane production and increase cellulolytic bacteria without any signs of toxic effects and with a minor effect on DM degradability.

• 한국식품과학회지
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• 제42권4호
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• pp.390-397
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• 2010

Residual solvents in foods are defined as organic volatile chemicals used or produced in manufacturing of extracts or additives, or functional foods. The solvents are not completely eliminated by practical manufacturing techniques and they also may become contaminated by solvents from packing, transportation or storage in warehouses. Because residual solvents have no nutritional value but may be hazardous to human health, there is a need to remove them from the final products or reduce their amounts to below acceptable levels. The purpose of this study was to develop and evaluate an analytical method for the screening of residual solvents in health functional foods. Furthermore, the aim of this study was to constitute a reasonable management system based on the current state of the market and case studies of foreign countries. Eleven volatile solvents such as MeOH, EtOH, trichloroethylene and hexane were separated depending on their column properties, temp. and time using Gas Chromatography (GC). After determining the GC conditions, a sample preparation method using HSS (Head Space Sampling) was developed. From the results, a method for analyzing residual solvents in health functional foods was developed considering matrix effect and interference from the sample obtained from the solution of solvents-free health functional foods spiked with 11 standards solutions. Validation test using the developed GC/HSS/MS (Mass Spectrometry) method was followed by tests for precision, accuracy, recovery, linearity and adequate sensitivity. Finally, examination of 104 samples grouped in suits was performed by the developed HSS/GC/MS for screening the solvents. The 11 solvents were isolated from health functional foods based on vapor pressure difference, and followed by separation within 15 minutes in a single run. The limt of detection (LOD), limit of quantification (LOQ), recovery and coefficient of variation (C.V.) of these compounds determined by the HSS/GC/MS were found to be 0.1 pg/mL, 0.1-125 pg/g, 51.0-104.6%, and less than 15%, respectively. Using the developed HSS/GC/MS method, residual solvent from 16 out of 104 health functional products were detected as a EtOH. This method therefore seems t o be a valuable extension ofanalytical method for the identification of residual solvents in health functional food.

• Journal of the Korean Wood Science and Technology
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• 제29권3호
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• pp.47-58
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• 2001

For finding both ways of recycling the wood and plastic wastes and solving the problem of free formaldehyde gas emission through manufacturing wood particle-polypropylene fiber composite board without addition of formaldehyde-based thermosetting resin adhesive, control particleboards and nonwoven web composite boards from wood particle and polypropylene fiber formulation of 50 : 50, 60 : 40, and 70 : 30 were manufactured at density levels of 0.5, 0.6, 0.7, and 0.8 g/$cm^3$, and were tested both in the physical and mechanical properties according to ASTM D 1037-93. In the physical properties, control particleboard had significantly higher moisture content than composite board. In composite board, moisture content decreased with the increase of target density only in the board with higher content of polypropylene fiber and also appeared to increase with the increase of wood particle content at a given target density. Control particleboard showed significantly greater water absorption than composite board and its water absorption decreased with the increase of target density. In composite board, water absorption decreased with the increase of target density at a given formulation but increased with the increase of wood particle content at a given target density. After 2 and 24 hours immersion, control particleboard was significantly higher in thickness swelling than composite board and its thickness swelling increased with the increase of target density. In composite board, thickness swelling did not vary significantly with the target density at a given formulation but its thickness swelling increased as wood particle content increased at a given target density. Static bending MOR and MOE under dry and wet conditions increased with the increase of target density at a given formulation of wood particle and polypropylene fiber. Especially, the MOR and MOE under wet condition were considerably larger in composite board than in control particleboard. In general, composite board showed superior bending strength properties to control particleboard, And the composite board made from wood particle and polypropylene fiber formulation of 50 : 50 at target density of 0.8 g/$cm^3$ exhibited the greatest bending strength properties. Though problems in uniform mixing and strong binding of wood particle with polypropylene fiber are unavoidable due to their extremely different shape and polarity, wood particle-polypropylene fiber composite boards with higher performance, as a potential substitute for the commercial particleboards, could be made just by controlling processing variables.

• 공업화학
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• 제21권3호
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• pp.343-348
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• 2010

저밀도 폴리에틸렌(low density polyethylene, LDPE) 필름의 표면을 다양한 반응 조건하에서 함산소불소화하여 hydroperoxide 관능기를 도입시켜 표면특성을 변화시켰다. 또한 생성된 hydroperoxide 관능기를 반응 개시제로 친수성 그룹을 가지는 단량체인 acryl amide (AM)와 소수성 그룹을 가지는 단량체인 methyl methacrylate (MMA)를 그라프트 중합시켜 LDPE 필름의 표면을 2차 개질하였다. 또한 LDPE, 함산소불소화 된 LDPE (OFPE), AM 및 MMA 단량체가 그라프트 된 OFPE 필름의 표면특성은 1,1-diphenyl-2-picrylhydrazyl (DPPH), 감쇠전반사 분광법, 시차주사 열량분석기 및 접촉각 측정법 등으로 분석하였다. DPPH 라디칼 분석법의 결과로부터, OFPE의 hydroperoxide 관능기의 양은 함산소불소화 총압력과 F2 가스의 부분압이 증가함에 따라 증가함을 알 수 있었다. 접촉각 및 표면 자유에너지 분석결과로부터, 함산소불소화에 의해서 생성된 hydroperoxide 관능기와 AM과 같은 친수성 그룹을 가지는 단량체의 그라프트 중합은 LDPE 필름 표면에서 물과 같은 친수성 용매의 접촉각을 감소시키고, MMA와 같은 소수성 그룹을 가지는 단량체의 경우는 LDPE 필름 표면에서 methylene diiodide와 같은 비극성 용매의 표면 접촉각을 감소시켰다. 이는 AM 및 MMA 단량체의 그라프트 중합에 의한 것으로, LDPE 필름 표면은 친수성 및 소수성 용매에 대한 젖음성이 향상되었다.

• 한국해안·해양공학회논문집
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• 제24권4호
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• pp.277-286
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• 2012

기체와 액체의 유동 및 고체의 변형을 동시에 고려할 수 있는 혼상류모델을 이용하여 파동장을 해석하는 경우, 서로 다른 비혼합의 유체 경계면의 시간변형을 고정도로 추적하는 것이 대단히 중요하다. 본 연구에서는 경계면의 추적에 있어서 VOF(Volume of Fluid)법으로 대표되는 경계면 형상의 재구축이 필요한 Geometrical-type의 경계추적법의 대신에 Algebraic-type의 경계추적법인 THINC(Tangent of Hyperbola for INterface-Capturing)법을 적용하였다. THINC법은 경계면에 대한 형상의 구축이 필요하지 않으므로 VOF법에 비해 비교적 간단한 알고리즘을 가지며, 기존의 Navier-Stokes solver에로 적용성이 용이한 장점을 갖는다. 본 연구에서는 THINC법의 기본적인 이류특성을 고찰하고, 혼상류수치모델인 TWOPM(one-field Model for immiscible TWO-Phase flows)과 결합한 수치모델을 파동장에 적용하여 비혼합 혼상류에서 경계면의 추적능을 검토하였다. 그 결과, 혼상류의 경계면 추적에 있어서 상대적으로 간단한 알고리즘의 THINC법이 기존의 VOF법과 유사한 정도를 갖는 해석법이라는 것을 확인할 수 있었고, 따라서 향후 기포의 연행을 동반하는 쇄파 및 쇄파력의 해석 등에 그의 적용성이 기대된다.

• Food Science and Biotechnology
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• 제18권1호
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• pp.95-102
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• 2009

The aerial parts of garland (Chrysanthemum coronarium L.) were extracted in 80% aqueous methanol (MeOH) and the concentrated extract was then partitioned using ethyl acetate (EtOAc), n-butanol (n-BuOH), and $H_2O$, successively. EtOAc and n-BuOH fractions resulted in 4 glycerides with the application of octadecyl silica gel and silica gel column chromatography. The chemical structures of the glycerides were determined using several spectroscopic methods, including nuclear magnetic resonance (NMR) and mass spectrometry (MS) as (2S)-1-O-palmitoyl-sn-glycerol (1), (2S)-1-O-oleoyl-2-O-oleoyl- 3-O-$\beta$-D-galactopyranosyl-sn-glycerol (2), (2S)-1-O-palmitoyl-2-O-linoleoyl-3-O-phosphorouscholine-sn-glycerol (3), and (2S)-1-O-linolenoyl-2-O-palmitoyl-3-O-[$\alpha$-D-galactopyrasyl-($1{\rightarrow}6$)-$\beta$-D-galactopyranosyl]-sn-glycerol (4). The free fatty acids of these glycerides were determined with gas chromatography (GC)-MS analysis following alkaline hydrolysis and methylation. These glycerides demonstrated an inhibitory effect on acyl-CoA: cholesterol acyltransferase (ACAT, compound 1: $45.6{\pm}0.2%$ at $100{\mu}g/mL$), diacylglycerol acyltransferase (DGAT, compound 1: $59.1{\pm}0.1%$ at $25{\mu}g/mL$), farnesyl protein transferase (FPTase, compound 2: $98.0{\pm}0.1%$; compound 3: $55.2{\pm}0.1%$ at $100{\mu}g/mL$), and $\beta$-secretase ($IC_{50}$, compound 4: $2.6{\mu}g/mL$) activity. This paper is the first report on the isolation of these glycerides from garland and their inhibitory activity on ACAT, DGAT, FPTase, and $\beta$-secretase.