• 한국표면공학회지
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• 제34권5호
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• pp.486-493
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• 2001

Partially stabilized zirconia (PSZ) is an attractive material for thermal barrier coating. Zirconia exists in three crystallographic phases: cubic, tetragonal and monoclinic. Especially, the phase transformation of tetragonal phase to monoclinic phase accompanies significant volume expansion, so this transition generally results in cracking and contributes to the failure of the TBC system. Both the plasma sprayed ZrO$_2$-8Y$_2$O$_3$ (YSZ) coat and the ZrO$_2$,-25CeO$_2$,-2.5Y$_2$O$_3$ (CYSZ) coat are isothermally heat -treated at 130$0^{\circ}C$ and 150$0^{\circ}C$ for 100hr and cooled at different cooling rates. The monoclinic phase is not discovered in all the CYSZ annealed at 130$0^{\circ}C$ and 150$0^{\circ}C$. In the 150$0^{\circ}C$ heat-treated specimens, the YSZ contains some monoclinic phase while none exists in the 130$0^{\circ}C$ heat-treated YSZ coat. For the YSZ, the different phase transformation behaviors at the two temperatures are due to the stabilizer concentration of high temperature phases and grain growth. For the YSZ with 150$0^{\circ}C$-100hr annealing, the amount of monoclinic phase increased with the slower cooling rate. The extra oxygen vacancy, thermal stress, and c to t'phase transformation might suppress the t to m martensitic phase transformation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.224-224
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• 2012

For decades, carbon fiber has expanded their application fields from reinforced composites to energy storage and transfer technologies such as electrodes for super-capacitors and lithium ion batteries and gas diffusion layers for proton exchange membrane fuel cell. Especially in fuel cell, water repellency of gas diffusion layer has become very important property for preventing flooding which is induced by condensed water could damage the fuel cell performance. In this work, we fabricated superhydrophobic network of carbon fiber with high aspect ratio hair-like nanostructure by preferential oxygen plasma etching. Superhydrophobic carbon fiber surfaces were achieved by hydrophobic material coating with a siloxane-based hydrocarbon film, which increased the water contact angle from $147^{\circ}$ to $163^{\circ}$ and decreased the contact angle hysteresis from $71^{\circ}$ to below $5^{\circ}$, sufficient to cause droplet roll-off from the surface in millimeter scale water droplet deposition test. Also, we have explored that the condensation behavior (nucleation and growth) of water droplet on the superhydrophobic carbon fiber were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. It is implied that superhydrophobic carbon fiber can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell. Moreover, such nanostructuring of carbon-based materials can be extended to carbon fiber, carbon black or carbon films for applications as a cathode in lithium batteries or carbon fiber composites.

• The Korean Journal of Physiology and Pharmacology
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• 제18권2호
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• pp.95-101
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• 2014

Cardiovascular disease is the prime cause of morbidity and mortality and the population ages that may contribute to increase in the occurrence of cardiovascular disease. Arginase upregulation is associated with impaired endothelial function in aged vascular system and thus may contribute to cardiovascular disease. According to recent research, Korean Red Ginseng water extract (KRGE) may reduce cardiovascular disease risk by improving vascular system health. The purpose of this study was to examine mechanisms contributing to age-related vascular endothelial dysfunction and to determine whether KRGE improves these functions in aged mice. Young ($10{\pm}3$ weeks) and aged ($55{\pm}5$ weeks) male mice (C57BL/6J) were orally administered 0, 10, or 20 mg/mouse/day of KRGE for 4 weeks. Animals were sacrificed and the aortas were removed. Endothelial arginase activity, nitric oxide (NO) generation and reactive oxygen species (ROS) production, endothelial nitric oxide synthase (eNOS) coupling, vascular tension, and plasma peroxynitrite production were measured. KRGE attenuated arginase activity, restored nitric oxide (NO) generation, reduced ROS production, and enhanced eNOS coupling in aged mice. KRGE also improved vascular tension in aged vessels, as indicated by increased acetylcholine-induced vasorelaxation and improved phenylephrine-stimulated vasoconstriction. Furthermore, KRGE prevented plasma peroxynitrite formation in aged mice, indicating reduced lipid peroxidation. These results suggest KRGE exerts vasoprotective effects by inhibiting arginase activity and augmenting NO signaling and may be a useful treatment for age-dependent vascular diseases.

• 한국진공학회지
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• 제14권3호
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• pp.165-170
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• 2005

의료용 임플랜트의 혈액적합성 개선을 위하여 박막코팅에 대한 관심이 증대하고 있다. 특히 diamond-like carbon(DLC)과 titanium nitride(TiN) 박막은 우수한 화학, 물리적 성질은 물론 생체적합 특성까지 갖추고 있다. 따라서 이들 박막의 혈액 적합성과 물리적 특성과의 관개를 연구하기 위하여 박막표면의 모폴로지 및 젖음성과 fibrinogen흡착 특성을 비교 분석하였다. 혈액응고 원인이 되는 fibrinogen의 흡착량은 DLC보다 TiN의 경우가 적어, 보다 우수한 특성을 보였으며, 이것은 TiN박막 표면의 높은 친수성으로 인한 것으로 판단된다. 박막표면의 fibrinogen 흡착을 줄이기 위해 플라즈마 처리 및 노(爐) 열처리를 각각 수행하였다. 산소 플라즈마 및 열처리를 하였을 경우 DLC 박막은 큰 효과가 없는 반면 TiN 박막의 경우 fibrinogen 흡착량이 크게 줄어 보다 개선된 결과를 보였다.

• ETRI Journal
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• 제16권1호
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• pp.45-57
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• 1994

The effects of reactive ion etching (RIE) of $SiO_2$ layer in $CHF_3/C_2F_6$ on the underlying Si surface have been studied by X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometer, Rutherford backscattering spectroscopy, and high resolution transmission electron microscopy. We found that two distinguishable modified layers are formed by RIE : (i) a uniform residue surface layer of 4 nm thickness composed entirely of carbon, fluorine, oxygen, and hydrogen with 9 different kinds of chemical bonds and (ii) a contaminated silicon layer of about 50 nm thickness with carbon and fluorine atoms without any observable crystalline defects. To search the removal condition of the silicon surface residue, we monitored the changes of surface compositions for the etched silicon after various post treatments as rapid thermal anneal, $O_2$, $NF_3$, $SF_6$, and $Cl_2$ plasma treatments. XPS analysis revealed that $NF_3$ treatment is most effective. With 10 seconds exposure to $NF_3$ plasma, the fluorocarbon residue film decomposes. The remained fluorine completely disappears after the following wet cleaning.

• 폴리머
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• 제24권6호
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• pp.869-876
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• 2000

소수성 표면성질을 나타내고 있는 poly(L-lactide-co-glycolide) (75 : 25 by mole ratio of lactide to glycolide, PLGA) 표면의 세포적합성을 증가시키기 위하여 물리화학적 처리방법으로 표면개질 하였다. 물리적 방법으로는 코로나 방전 및 플라즈마 처리가, 화학적인 방법으로는 70% 염소산, 50% 황산 및 0.5 N 가성소다 수용액으로 처리하였다. 처리된 PLGA 표면의 물접촉각은 73$^{\circ}$에서 50~60$^{\circ}$로 감소하였고 electron spectroscopy for chemical analysis의 분석결과, 알킬탄소는 감소되는 반면, 산소를 포함하는 탄소 관능기들이 상대적으로 증가함을 보여 친수화의 주원인으로 사료되었다. 섬유아세포의 배양 결과 control에 비하여 처리된 PLGA상에 점착 및 성장거동이 우월하게 관측되어 본 처리 방법이 세포적합성을 증가시켰다고 사료된다. 결론적으로 PLGA 표면의 적심성에 있어서 친수화는 세포의 점착 및 성장에 중요한 역할을 하늘 것으로 확인되었다.

• BMB Reports
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• 제31권3호
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• pp.227-232
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• 1998

The leukocyte NADPH oxidase of neutrophils is a membrane-bound enzyme that catalyzes the production of $O_2^-$ from oxygen using NADPH as an electron donor. Dormant in resting neutrophils, the enzyme acquires catalytic activity when the cells are exposed to appropriate stimuli. During activation, the cytosolic oxidase components $p47^{phox}$ and $p67^{phox}$ migrate to the plasma membrane, where they associate with cytochrome $b_{558}$, a membrane-bound flavohemoprotein, to assemble the active oxidase. The oxidase can be activated in a cell-free system; the activating agent usually employed is an anionic amphiphile such as sodium dodecyl sulfate (SDS). Because $p47^{phox}$ can translocate by itself during activation, the conformational change in $p47^{phox}$ may be responsible for the activation of NADPH oxidase. We show here that the treatment of $p47^{phox}$ with SDS leads to an increase in the reactivity of the sutbydryl group of cysteines toward N-ethylmaleimide, indicating that the conformational change occurs when $p47^{phox}$ is exposed to SDS. We propose that this change in conformation results in the appearance of a binding site through which $p47^{phox}$ interacts with cytochrome $b_{558}$during the activation process.

• Parasites, Hosts and Diseases
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• 제39권2호
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• pp.133-141
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• 2001

A cDNA of 1.1 kb comprising the gene encoding the peroxiredoxin of Toxo-plasma gondii(TgPrx) has been cloned. The open reading frame of 591 Up was translated into a protein of 196 amino acids with a molecular mass of 25 kDa. Conserved 2 cysteine domains of Phe-Val-Cys-Pro and Glu-Val-Cys-Pro indicated TgPrx belonged to 2-Cys Prx families. TgPrx showed the highest homology with that of Arabidopsis thaliana by 53.9% followed by Entamoeba histolytica with 39.5% by the amino acid sequence alignment. Polyclonal antibody against recombinant TgPrx detected 25 kDa band in T. gondii without binding to host cell proteins TgPrx was located in the cytoplasm of T. gondii extracellularly or intracellularly by immunofluorescence assay. The expression of TgPrx was increased as early as 30 min after the treatment with artemisinin in the intracellular stage, while no changes in those of host Prx I and TgSOD. This result implies that TgPrx may function as an antioxidant protecting the cell from the attack of reactive oxygen intermediates. It is also suggested that TgPrx is a possible target of chemotherapy.

• 대한한방내과학회지
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• 제19권1호
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• pp.247-270
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• 1998

The more society has complicated, the more we have met stressful circumstance. And it is found that many physical and mental symptoms induced by stress. Soyosan(SYS) is one of the well-known oriental medicine for the treatment of general syndrome induced by emotional stress. This study was taken to know effects of SYS water extract on immune-depressed mice induced by stress. The results obtained in this study were as follows : 1. SYS inhibited murine weight-loss induced by stress 2. In vivo& in vitro, SYS increased phagocytic activity. 3. SYS enhanced the production of such reactive oxygen intermediates as superoxide and hydrogen peroxide from macrophages. 4. In vitro, SYS little influenced the production of reactive nitrogen intermediates. 5. SYS increased the number of the rosette forming cells of spleen. 6. SYS changed the ratio of helper and suppressor T cells by increasing $CD4^+$ T cells and decreasing $CD8^+$ T cells. 7. SYS increased cytotoxic activity on human lymphoma cell line(K562). 8. SYS increased the plasma level of GH and DHEA. whereas it decreased that of ACTH and cortisol. According to the above results, it might be considered that SYS would be used for immune-depressive disease induced by stress.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1476-1477
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• 2008

This paper reports on a flexible flap valve actuated by electromagnetic force under a constant pressure source. The flexible flap valve consists of the three main components: a flexible flap with a steel disk embedded in PDMS, an electromagnetic actuator and two glass plates with inlet and outlet. Sealing lip structures for improving the valve characteristics are added on the outlet of the bottom glass substrate. The flap valve is fabricated by the spin-coating process, the EDM process, SU-8 mold process and oxygen plasma treatment. The dimension of an assembled flap valve is $12mm{\times}20mm{\times}28mm$. The stroke volume of the flap valve is measured for various pressures and open times. When the input voltage of 30 V is applied for 0.33 s, the minimum stroke volume of the flap valve is 70 ${\mu}L$ at 50 kPa.