• 대한기계학회논문집
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• 제18권10호
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• pp.2712-2723
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• 1994

Numerical simulation of an axisymmetric ethylene-air jet diffusion flame has been carried out in order to investigate flame dynamics and soot formation. The model solves the time-dependent Navier-Stokes equations and includes models for soot formation, chemical reaction, molecular diffusion, thermal conduction, and radiation. Numerically FCT(Flux Corrected Transport) and DOM(Discrete Ordinate Method) methos are used for convection and radiation trasport respectively. Simulation was conducted for a 5 cm/sec fuel jet flowing into a coflowing air stream. The maximum flame temperature was found to be approximately 2100 K, and was located at an axial position of approximately 5 cm from the base of the flame. The maximum soot volume fraction was about $7{\times}10^{-7}$, and was located within the high temperature region where the fuel mole fraction ranges from 0.01 to 0.1. The buoyancy-driven low-frequency(12~13 Hz) structures convected along the outer region of the flame were captured. In case without radiation trasport, the maximum temperature was higher by 150 K than in case with radiation. Also the maximum soot volume fraction reached about $8{\times}10^{-6}$. As the the hydrocarbon fuel forms many soot particles, the radiation transport becomes to play a more important role.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권4호
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• pp.367-371
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• 2005

About 3,000 bacterial colonies with esterase activities were isolated from soil samples by enrichment culture and halo-size on Luria broth-tributyrin (LT) plates. The colonies were assayed for esterase activity in microtiter plates using enantiomerically pure (R)- and (S)-2-phenylbutyric acid resorufin ester (2PB-O-res) as substrates. Two enantioselective strains (JH2 and JH13) were selected by the ratio of initial rate of hydrolysis of enantiomerically pure (R)- and (S)-2-PB-O-res. When cell pellets were used, both strains showed high apparent enantioselectivity ($E_{app}>100$) for (R)-2PB-O-res and were identified as Exiguobacterium acetylicum. The JH13 strain showed high esterase activity on p-nitrophenyl acetate (pNPA), but showed low lipase activity on p-nitrophenyl palmitate (pNPP). The esterase was located in the soluble fraction of the cell extract. The crude intracellular enzyme preparation was stable at a pH range from 6.0 to 11.0.

• BMB Reports
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• 제28권4호
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• pp.281-289
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• 1995

Homogeneous human deoxycytidine kinase was purified in one step from a variety of spontaneous human leukemic cells (T-ALL, B-ALL, B-CLL, AML, CML), and from cultured T-lymphoblast cells (MOLT-4) using the newly developed affinity medium, $dCp_4$-Sepharose. Starting with an ammonium sulfate fraction, purification was achieved in one step with the kinase being eluted from a column by the end product inhibitor, dCTP. The purified deoxycytidine kinase from T-ALL cells phosphorylated deoxyadenosine and deoxyguanosine, as well as deoxycytidine. The enzyme purified from T-ALL and B-CLL cells yielded one major band with a molecular weight of 52 kDa determined by SDS-polyacrylamide gel electrophoresis. AML and CML cells yielded one 52 kDa band and an extra band of 30 kDa molecular weight. On the other hand, B-ALL and MOLT-4 cells showed a low molecular weight band of 30 kDa only. However, the electrophoretic mobilities of enzymatic activity in 12% non-denaturing gels were identical for the dCyd kinase from all different kinds of leukemic cell lines, except that the B-ALL, B-CLL, and MOLT-4 cell preparations had an extra minor peak, all at the same position. dAdo and dCyd phosphorylating activities comigrated indicating that these activities are all associated with the same protein. Two new methods, a disk implantation method and a nitrocellulose powder method were used with a small amount of enzyme protein to raise polyclonal antibodies against dCyd kinase purified from T-ALL cells.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권6호
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• pp.494-499
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• 2005

The chemical, physical, and emulsifying properties of BSF-1, which is an extracellular lipopolysaccharide biosurfactant produced by Klebsiella oxytoca strain BSF-1, were studied. BSF-1 was found to be composed mainly of carbohydrate and fatty acids. The average molecular weight was $1,700{\sim}2,000 kDa$. The polysaccharide fraction contained L-rhamnose, D-galactose, D-glucose, and D-glucuronic acid at a molar ratio of 3:1: 1:1. The fatty acid content was 1.1 % (w/w) and consisted mainly of palmitic acid (C16:0), 3-hydroxylauric acid (3-OH-C12:0), and lauric acid (C12:0). In terms of thermal properties, BSF-1 was revealed to have inter- and intra-molecular hydrogen bonds. The hydrodynamic volume (intrinsic viscosity) of BSF-1 was 22.8dL/g. BSF-1 could be maintained as a stable emulsion for 48 h through a low-level reduction in surface tension. The optimal emulsification temperature was $30^{\circ}C$. Emulsification by BSF-1 was efficient at both acidic and neutral pH values.

• 한국식품과학회지
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• 제31권5호
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• pp.1300-1307
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• 1999

최근 식생활 패턴이 서구화되면서 유지의 소비량이 증가하고 있다. 이에 따라 폐기되는 식용유지 또한 증가하고 있으며 환경오염 방지를 피해 비누 등을 만들어 재활용하려는 노력 등이 시도되고 있다. 본 연구에서는 폐식용유의 재활용을 위하여 초임계 이산화탄소 추출법을 이용하여 그 가능성을 확인하고 추출조건을 확립하기 위한 기초 실험을 수행하였다. 온도 $40{\sim}60^{\circ}C$, 압력 $15{\sim}30\;MPa$의 범위에서 초임계 이산화탄소로 폐식용유를 추출하였을 때 추출초기의 농도는 $0.3X10^{-3}{\sim}7.4X10^{-3}(g\;fat/g\;CO_2)$이었다. 초임계 추출물에서의 식용유의 농도는 이산화한소의 밀도에 대하여 지수함수적인 관계를 보였다. 초임계 추출물의 색상은 엷은 노란색으로써 신선한 식용유와 거의 유사하였다. 15 MPa, $60^{\circ}C$를 제외하고는 모든 조건의 추출물에서 중합체, triglyceride, 저분자량 물질이 혼재되어 있었다. 이산화탄소의 밀도가 비교적 높아서 용해력이 큰 30 MPa와 22.5 MPa의 경우 분획물에서의 CD 값의 증가에는 산화생성물의 polymer가 크게 기여함에 반하여 밀도가 낮은 15 MPa의 경우 용해력이 낮은 까닭에 용해도가 큰 저분자량 물질들이 주로 추출되어 이것이 CD 값의 증가에 기여함을 알 수 있었다. 본 연구에서 나타난 결과에서는, 비록 triglyceride만 존재하는 fraction은 나타나지 않았으나 분획을 더 많이 할 경우 이의 존재가능성도 예상되었다. 상대분리효율의 개념을 이용하여 TG와 저분자량 물질간의 분리효율이 좋은 실험 조건 $(22.5 MPa,\;60^{\circ}C$)을 선택하여 흡착 컬럼을 사용하여 저분자량 물질의 제거를 시도하였으나, 선택성이 떨어져 흡착제의 사용은 그다지 실효가 없는 것으로 판명되었다.

• 생명과학회지
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• 제16권5호
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• pp.834-839
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• 2006

'쓰가루' 사과의 연화동안에 일어나는 세포벽 성분의 변화와 펙틴 및 중성당류의 가용화와 분해 정도를 조사하였다. 과실의 연화단계별로 펙틴다당류들을 증류수, 0.05 M CDTA, 0.05 M $Na_2CO_3$, 8 M KOH를 이용하여 분획하였다. Uronic acid (UA) 함량은 과실의 연화가 진행되면서 증류수 가용성 분획에서는 저장 4주후에 급격히 증가하였다. 각 분획별 비섬유성 중성당의 종류를 보면 증류수, 0.05 M CDTA 및 0.05 M $Na_2CO_3$ 가용성분획에서의 주요 구성당은 galactose와 arabinose였으며, 8 M KOH 가용성분획에서는 glucose, galactose 및 xylose였다. 특히 증류수 가용성 분획에서 과실의 연화가 진행되면서 galactose의 함량이 증가되었다. 그리고 증류수 가용성인 물질을 Sepharose CL-2B를 이용하여 uronic acid polymers (UAP)와 carbohydrate polymers (CP)를 분획한 결과를 보면 고분자의 UAP 및 CP가 수확후 과실의 연화가 진행될수록 저분자화 되었다. 고분자 중합물의 양은 과실이 연화됨에 따라 감소하였다.

• Journal of Photoscience
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• 제8권3_4호
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• pp.105-112
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• 2001

Susceptibility to low temperature photoinhibition in photosynthetic apparatus was compared among three cucumber cultivars, Gahachungjang (GH), Banbaekjijeo (BB) and Gaeryangsymji (GR). By chilling in the light for 6 h, a sustained decrease in the potential quantum yield (Fv/Fm) and the oxidizable P700 contents was observed, and the decrease was less in GH than in BB and GR. Although the difference was small, some $\Phi_{PSII}$ remained in GH after light-chilling for 6 h indicating that a few electrons can flow around photosystem II(PSII). As a consequence, the primary electron acceptor of PSII, $Q_{A}$, was reduced slowly and was not fully reduced after light-chilling for 6 h in GH. Although the amplitude was small, the development of NPQ was also faster in GH, indicating a higher capacity for non-photochemical energy dissipation. The relative fraction of a fast relaxing component of NPQ (qf) was higher in GH. After light-chilling for 5 h, the values of qf in BB and GR became much smaller than that in GH, indicating BB and GR suffered more significant uncoupling of ATPase and/or irreversible damages in PSII. When fluorescence induction transients were recorded after chilling, significant differences in quenching coefficients (qQ and qN) were observed among the three cultivars.

• Fisheries and Aquatic Sciences
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• 제16권4호
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• pp.237-242
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• 2013

We investigated the antioxidant and angiotensin I converting enzyme (ACE) inhibitory activities of red snow crab Chionoecetes japonicas shell (RSCS) hydrolysate by enzymatic hydrolysis and its molecular weight cut-off fractions. The RSCS hydrolysate was fractionated through two ultrafiltration membranes of 3 and 10 kDa cut-offs. Three fractions (<3 kDa, 3-10 kDa, and >10 kDa) were evaluated for total amino acid composition, antioxidant activities using 2'-azino-bis[3-ethylbenzthiazoline-6-sulfonic acid] ($ABTS^+$) radical scavenging and superoxide dismutase (SOD)-like activities and reducing power assays, and ACE inhibitory activity using Hou's method. Although all fractions showed activity, the <3 kDa fraction of RSCS hydrolysate exhibited the greatest $ABTS^+$ radical scavenging, SOD-like and ACE inhibitory activities. However, these fractions exhibited low reducing power. These results suggest that the low-molecular-weight enzymatic hydrolysate of RSCS could be used as a functional ingredient to control oxidative stress and ACE activity.

• 대한환경공학회지
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• 제22권7호
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• pp.1253-1261
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• 2000

천연유기물질은 지표수와 지하수내 탁도를 유발하고 humic (humic acid와 fulvic acid)과 nonhumic 성분으로 구성된다. 일반적으로 NOM은 소독부산물(DBP) 전구물질로써 수처리시 관심의 대상이 된다. 원수의 특성은 정수공정의 선택과 적용에 중요한 정보를 제공한다. 수원에 따른 NOM의 상당한 차이가 다양한 원수들 사이에서 관찰되었고, 문제시되는 NOM을 제거하고 전환시키기 위한 목적으로 정수공정을 적용한다. 본 연구의 결과, 산화처리에 의해 전체 DOC 농도의 변화는 거의 없었지만, 고분자의 소수성 물질이 저분자의 친수성 물질로 전환되었고, 염소보다 오존의 경우 그 산화력의 차이 때문에 SUVA 값의 감소가 더 크게 나타났다. 응집처리에 의해 hydrophilic 성분보다 분자량이 더 큰 hydrophobic 성분이 응집 침전되어 훨씬 잘 제거되었다. THMFP는 50% 정도까지 제거되었는데, 이것은 상대적으로 THMFP를 잘 유발시킨다는 humic acid 성분의 제거가 원활하게 일어났기 때문이다.

• 한국물환경학회지
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• 제21권2호
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• pp.125-131
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• 2005

Natural organic matter(NOM) is defined as the complex matrix of organic material and abundant in natural waters. It affects the performance of unit operations for water purification. Several kinds of analytical indicators such as DOC, specific ultraviolet absorbance(SUVA), apparent molecular weight (AMW), fractionation and high performance size exclusive chromatography(HPSEC) have been used to understand characteristics and variations of NOM. This study aims to evaluate the characteristics of NOM in the Geum River system comprising with stream flows and reservoirs. It was identified that SUVA denoting the portion of humic substance in water ranged within 1.60~3.36. Using resin adsorbents, dissolved organic carbon(DOC) was fractionated into three classes: hydrophobic bases(HOB), hydrophobic acids(HOA) and hydrophilic substances(HI). HI dominates in all samples, collectively accounting for more than 62% of the DOC. HOA was the second dominated fraction and it varied considerably but accounted for about 30% of the DOC. The distribution of high molecular weight(HMW) measured by HPSEC being used to determine the molecular weight distribution of aquatic humic substances was 40.1% and 38.7% in reservoir and stream flow, respectively. The distribution of low molecular weight(LMW) in stream flow was 13.2% higher than that in reservoir. And apparent molecular weight less than 1KDa, which include the molecular weight of hydrophilic organic matter, occupied with 69.2% and 68.2% in stream flow and reservoir, respectively. While the molecular weight of 1 to 100 KDa including humic substances ranged with 18.6% and 21.6% in stream flow and reservoir, respectively. Seasonal variation of refractory dissolved organic carbon was similar to that of SUVA.