• Korean Chemical Engineering Research
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• 제50권3호
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• pp.556-561
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• 2012

본 연구에서는 고분자형 연료전지(PEMFC) 내의 기체확산층(GDL)에서의 물질 거동 전산해석을 통하여 GDL 물성이 전지성능에 미치는 영향을 알아보았다. GDL 내에서 기상의 산소와 액상의 물의 거동을 계산하기 위하여 multi-phase mixture($M^2$) 모델을 사용하였다. GDL의 접촉각, 기공도, 기체투과도, 두께에 변화를 주며 계산을 실시하여 GDL 내에서의 물질 거동의 변화를 확인 하였고, GDL 물성이 전지성능에 미치는 영향을 파악하였다. 전산해석 결과, GDL의 접촉각과 기공도가 커지고, 두께가 얇아짐에 따라 물질전달 저항이 감소하여 GDL과 촉매층 사이의 계면에서의 물포화도가 낮아지고 산소농도는 증가하여 전지성능이 향상되는 것을 확인하였다.

• 한국자기학회지
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• 제18권3호
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• pp.103-108
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• 2008

비휘발성 메모리 분야에서 MRAM이 큰 주목을 받지 못하는 이유는 일반적인 비휘발성 메모리에 비해 기록용량이 작다는 문제를 안고 있기 때문이다. 이러한 문제는 MRAM의 일반적인 구조가 자기 효율이 떨어지는 구조를 가지고 있기 때문이다. MRAM이 고용량화 되기 위해선 한 셀의 구조가 작아져야 하는데 두 전류라인만을 이용하는 일반적인 구조에선 큰 기록 필드를 발생시킬 수 없기에 셀의 구조를 작게하는 것은 불가능하다. 본 논문에서는 MRAM의 기록층 양단에 큰 투자율을 가진 Pole을 추가한 형태의 새로운 MRAM을 제안하고 있다. 새로이 고안된 MRAM은 일반적인 MRAM에 비해 자기효율이 크게 향상 되기 때문에 큰 기록 필드를 발생시킬 수 있기 때문에 보자력이 큰 기록 층을 사용할 수 있고 이로 인해 한 셀의 사이즈를 줄일 수 있게 된다. 본 연구는 3차원 유한요소법을 사용하여 진행 되었다.

• Journal of Pharmaceutical Investigation
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• 제32권1호
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• pp.21-26
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• 2002

The primary culture of human nasal epithelial cell monolayer was performed on a Transwell. The effect of various factors on the tight junction formation was observed in order to develop an in vitro experimental system for nasal transport studies. Human nasal epithelial cells, collected from human normal inferior turbinates, were plated onto diverse inserts. After 4 days, media of the apical surface was removed for air-liquid interface (ALI) culture. Morphological characteristics was observed by transmission electron microscopy (TEM). A polyester membrane of $0.4\;{\mu}m$ pore size was determined as the most effective insert based on the change in the transepithelial electric resistance (TEER) value as well as the $^{14}C-mannitol$ transport study. The ALI method was effective in developing the tight junction as observed in the further increase in the TEER value and reduction in the permeability coefficient $(P_{app})$ of $^{14}C-mannitol$ transport. Results of the transport study of a model drug, budesonide, showed that the primary culture system developed in this study could be further developed and applied for in vitro nasal transport studies.

• 한국가구학회지
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• 제28권3호
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• pp.248-258
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• 2017

A study was carried out to observe the 1% aqueous safranine solution flow speed in longitudinal and radial directions of softwood Thuja orientalis L., diffuse-porous wood Gmelina arborea Roxb., and ring-porous wood Phellodendron amurense Rupr., Longitudinal flow was considered from bottom to top while the radial flow was considered from bark to pith directions. In radial direction, ray cells and in longitudinal direction tracheids, vessel and wood fiber were considered for the measurement of liquid penetration speed at less than 12% moisture contents(MC). The variation of penetration speed for different species was observed and the reasons behind for this variation were explored. The highest radial penetration depth was found in ray parenchyma of T. orientalis but the lowest one was found in ray parenchyma of P. amurense. The average liquid penetration depth in longitudinal trachied of T. orientalis was found the highest among all the other cells. The penetration depth in fiber of G. arborea was found the lowest among the other longitudinal cells. It was found that cell dimension and also meniscus angle of safranine solution with cell walls were the prime factors for the variation of liquid flow speed in wood. Vessel was found to facilitate prime role in longitudinal penetration for hardwood species. The penetration depth in vessel of G. arborea was found highest among all vessels. Anatomical features like ray parenchyma cell length and diameter, end-wall pits number were found also responsible fluid flow differences. Initially liquid penetration speed was high and the nit gradually decreased in an uneven rate. Liquid flow was captured via video and the penetration depths in those cells were measured. It was found that even in presence of abundant rays in hardwood species, penetration depth of liquid in radial direction of softwood species was found high. Herein the ray length, lumen area, end wall pit diameter determined the radial permeability. On the other hand, vessel and fiber structure affected the longitudinal flow of liquids. Following a go-stop-go cycle, the penetration speed of a liquid decreased over time.

• Archives of Pharmacal Research
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• 제29권4호
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• pp.318-322
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• 2006

Many quaternary ammonium salts are incompletely absorbed after their oral administration and may also be actively secreted into the intestine. However, the underlying mechanism(s) that control the transport of these cations across the intestinal epithelium is not well understood. In this study, the mechanism of absorption of quaternary ammonium salts was investigated using Caco-2 cell monolayers, a human colon carcinoma cell line. Tributylmethylammonium (TBuMA) was used as a model quaternary ammonium salts. When TBuMA was administrated at a dose of 13.3 imole/kg via iv and oral routes, the AUC values were $783.7{\pm}43.6\;and\;249.1{\pm}28.0{\mu}mole\;min/L$ for iv and oral administration, indicating a lower oral bioavailability of TBuMA $(35.6\%)$. The apparent permeability across Caco-2 monolayers from the basal to the apical side was 1.3 times (p<0.05) greater than that from the apical to the basal side, indicating a net secretion of TBuMA in the intestine. This secretion appeared to be responsible for the low oral bioavailability of the compound, probably mediated by p-gp (p-glycoprotein) located in the apical membrane. In addition, the uptake of TBuMA by the apical membrane showed a $Na^+$ dependency. Thus, TBuMA appears to absorbed via a $Na^+$ dependent carrier and is then secreted via p-gp related carriers.

• Korean Chemical Engineering Research
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• 제59권1호
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• pp.6-10
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• 2021

PEMFC(Proton Exchange Membrane Fuel Cell) 고분자 막의 shorting 저항(Shorting Resistance, SR)은 고분자 막의 내구성에 관한 중요한 지표다. SR이 감소하면 shorting 전류(Shorting Current, SC)가 증가하여 내구성과 성능이 감소하고, SR이 약 0.1 kΩ·㎠ 이하가 되면 shorting이 발생하여 온도가 급상승하고 MEA(Membrane Electrode Assembly)를 연소시켜 스택 구동이 종료된다. Shorting 현상을 방지하기 위해서는 SR을 제어해야 하므로 SR에 영향을 주는 조건들에 대해서 연구하였다. SR 측정방법들에서도 차이가 있어서 DOE(Department of Energy)와 NEDO(New Energy and Industrial Technology Development Organization) 방법을 개선한 SR 측정법을 제시하였다. 상대습도와 온도, 셀 체결 압이 상승하면 SR이 감소함을 확인하였다. 고분자 막의 가속내구 평가과정에서 마지막 단계에서 SR이 0.1 kΩ·㎠ 이하로 급감해 수소투과전류밀도가 15 mA/㎠ 이상이 되었고, 이 MEA를 해체 후 SEM(Scanning Electron Microscope) 분석한 결과 고분자 막 내부에 백금이 많이 분포함을 보였다.

• 대한한의학방제학회지
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• 제31권2호
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• pp.111-124
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• 2023

Objectives : Oxidative stress is an important cause of many diseases including liver injury. Therefore, adequate regulation of oxidative stress plays a pivotal role in maintaining liver function. Until recently, there has been no studies on the hepatoprotective effect of Samchulgeonbi-tang (SCGBT). Therefore, the hepatoprotective effect of SCGBT was investigated in HepG2 cells. In this study, oxidative stress was induced by arachidonic acid (AA) and iron. Methods : To analyze the hepatoprotective effects of SCGBT against oxidative stress induced by AA + iron, the cell viability, apoptosis-related proteins and intracellular ROS, glutathione (GSH), and mitochondrial membrane permeability (MMP) were measured. In addition, nuclear factor erythroid 2-related factor 2 (Nrf2) transcription activation and expressions of Nrf2 target gene were analyzed through immunoblot analysis. Results : SCGBT increased the cell viability from AA + iron - induced cell death and inhibited apoptosis by regulating apoptosis related proteins. SCGBT protected cells by inhibiting ROS production, GSH depletion, and MMP degradation against AA + iron induced oxidative stress. Furthermore, Nrf2 activation was increased by SCGBT, and the Nrf2 target genes were also activated by SCGBT. Conclusions : These results suggest that the SCGBT has a hepatocyte protection effect and antioxidant effect from AA + iron induced oxidative stress.

• 대한한의학방제학회지
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• 제31권4호
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• pp.265-281
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• 2023

Objectives : Ukgan-san plus Citri Pericarpium and Pinelliae Rhizoma (UCP) is used as a traditional herbal formula in Korea and Japan for treatment of fever, fever-induced convulsions, and liver dysfunction and so on. In this study, we investigated the cytoprotective effect and underlying mechanism of UCP against oxidative stress induced by cotreatment of arachidonic acid (AA) and iron. Methods : To evaluate the hepatoprotective effects of UCP against AA + iron-induced oxidative stress in HepG2 cell, cell viability and changes on apoptosis-related proteins were assessed by MTT and immunoblot analyses. The changes in intracellular reactive oxygen species (ROS), glutathione (GSH), and mitochondrial membrane permeability (MMP) were investigated against to the oxidative stress. Furthermore, to verify underlying molecular mechanism, NF-E2-related factor 2 (Nrf2) and its downstream target genes were examined by immunoblot analysis. Results : Treatment of UCP increased the cell viability and altered the expression levels of apoptosis-related proteins such as PARP, caspase-9, caspase-3, Bcl-2. UCP also inhibited the GSH depletion, excessive ROS production and mitochondrial dysfunction induced by AA + iron. In addition, the Nrf2 and the Nrf2 target genes activation were increased by UCP. Conclusions : These results indicated that UCP has the ability to protect against oxidative stress-induced hepatocyte damage, which may be mediated with Nrf2 pathway.

• 대한화장품학회지
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• 제33권3호
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• pp.189-196
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• 2007

이온교환수지를 이용하여 말단기에 이중결합 생성이나 고리열림반응 없이 저분자 히알루론산(oligo HA)을 제조하였다. 제조된 oligo HA의 화장품소재로서의 활용 가능성 및 그 효능을 평가하기 위하여 fibroblast, keratinocyte 및 SIRC cell을 이용하여 독성을 평가하였고, Caco-2 cell과 인공피부를 이용하여 피부 투과도를 평가하였다. Oligo HA는 fibroblast와 keratinocyte cell에서 각각 300 ${\mu}g/mL$ 및 1,000 ${\mu}g/mL$까지의 농도에서 독성이 없었으며 in vitro ocular test에서도 2,000 ${\mu}g/mL$의 높은 농도에서까지 자극에 의한 세포독성이 관찰되지 않았다. Caco-2 cell을 이용한 세포 투과실험에서는 HA는 거의 투과되지 않는 것에 비해 oligo HA은 16.0 %까지 투과되었고, 인공피부를 이용한 세포투과 실험에서도 약 90 %의 상당히 높은 투과도를 보였다. 사람 피부에서 보습효과를 확인하기 위하여 oligo HA를 함유한 제형을 피부에 도포한 후 피부 수분량과 경피수분 손실량을 측정한 결과 HA와 비슷하게 우수한 보습 효과를 확인할 수 있었다. 인체 피부 누적 첩포 실험 결과, 특별한 피부 자극이 확인되지 않았다. Oligo HA는 HA의 우수한 보습력을 유지하면서 높은 피부 투과도를 갖는 보습소재로써 화장품에 유용하게 활용될 수 있음을 확인하였다.

• Tuberculosis and Respiratory Diseases
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• 제50권2호
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• pp.205-212
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• 2001

연구배경 : 비강 점막을 통한 약물의 이동이나 대사 등은 실험 동물을 이용한 약력학적인 연구가 이루어져 왔으나 사람의 비강 점막 상피세포의 투과에 대한 연구는 없는 실정이다. 따라서 저자 등은 air-liquid interface (ALI) 방법으로 세포를 배양하여 그 미세구조와 in vitro에서 비강점막 상피세포에 대한 mannitol의 투과도를 알아보고자 하였다. 방 법 : 만성 부비동염 환자의 내시경을 이용한 부비동 수술시 정상 하비갑개의 조직을 채취하여 ALI 방법을 이용하여 transwell내에 monolayer로 상피세포를 배양하였으며 blank filter, 배양 5일째 및 7일째에 transepithelial electrical resistance (TEER) 값을 측정하고 투과전자현미경을 이용하여 견고연접(tight junction)의 형성을 확인하였다. 배양된 세포의 mannitol의 투과도를 알아보기 위해 12일째에 $^{14}C$가 부착된 mannitol $4{\mu}mol$을 배양액과 함께 투여하고 1시간 동안 10분 간격으로 % leakage를 측정하였다. 결 과 : 사람의 비강 상피세포는 7일 내에 confluent monolayer로 배양되었으며 투과전자현미경상 섬모와 견고 연접의 형성이 잘 관찰되었다. TEER 값은 blank filter는 $108.5\;ohm.cm^2$, 배양 5일째는 $141\;ohm.cm^2$, 배양 7일째는 $177.5\;ohm.cm^2$로 측정되었다. Mono-layer를 통한 $^{14}C$-mannitol의 % leakage는 10분, 20분, 30분, 40분, 50분, 60분에 각각 $35.67{\pm}5.43$, $34.42{\pm}5.60$, $32.75{\pm}5.71$, $31.76{\pm}4.22$, $30.96{\pm}3.49$, $29.60{\pm}3.68%$로 나타났다. 결 론 : ALI 방법으로 배양된 사람의 정상 비강점막 상피세포는 생체와 유사하게 배양되어 세포의 투과도(transcellular permeability) 를 알아보는데 적합하며 in vitro에서 비강점막을 통한 약물의 transport에 대한 연구에 도움이 될 것으로 생각된다.