• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.343-343
• /
• 2010

Tetra(4-carboxyphenyl)porphine(TCPP) 흡착으로부터 그래핀 표면의 기능화에 대하여 방사광을 이용한 광전자 분광법으로 연구하였다. 최근 들어 그래핀을 이용한 소자개발에 있어서 그래핀의 우수한 전기적 특성을 저해하지 않으며 그 표면의 화학적 활성도를 개선하고자 하는 필요성이 대두되고 있다. 따라서 기능성 작용기를 가지고 있는 유기반도체 물질을 이용하여 그래핀 표면의 화학적 활성화를 촉진시킴과 동시에 보호층을 형성시키고자 하는 연구가 보고되고 있다. 그러나 일반적으로 그 유기분자들이 그래핀 표면에 흡착되었을 때 전하의 이동을 유도함으로서 원래 그래핀의 물리적 특성을 변화시킬 가능성을 가지고 있다. 본 연구에서는 6H-SiC 표면 위에 두층으로 에피텍셜 성장된 그래핀에 TCPP 분자를 흡착시킴으로서 그래핀의 고유 특성을 거의 저해하지 않음과 동시에 기능성 작용기의 역할을 충실히 수행할 수 있음을 보여 주고 있다. 이는 valence band dispersion과 일함수 변화 측정으로 관찰할 수 있었다. 또한 TMA를 이용한 TCPP의 수산화 작용기의 반응 과정은 일반적인 실리콘 산화막에 적용했을 때 일어나는 화학적 반응 과정과 다른 메커니즘으로 진행됨을 관찰하였다.

• Development and Reproduction
• /
• v.2 no.1
• /
• pp.29-37
• /
• 1998

To investigate the role of oviductal environment in early mammalian development, we examined the effects of bovine oviductal fluid (bOF) on the development of mouse 2-cell embryos in vitro. All of the embryos cultured in medium containing 5% or more of bOF underwent degeneration after 48 hr, whereas only 5% of embryos cultured in the absence of bOF degenerated. When bOF was heated at 65 \circ C for 30 min and then added to the culture medium, the embryotoxic effect of bOF was not removed at all such that none of the embryos remained alive after 48 hr. However, when bOF heated at 90 \circ C for 30 min was added to the culture, nearly most (95%) of embryos was alive. Similarly, pretreatment of bOF with 0.1% chymotrypsin for 1 hr or overnight following heating at 65 \circ C resulted in the development of 95.5% of mouse 2-cell embryos to early blastula after 48 hr culture in the presence of treated bOF. Interestingly addition of an anti-oxidant removed the evbryotoxic effect of bOF so that 91.0% of 2-cell embryos developed to morulae or blastulae in the presence of both 5% bOF and 10 mM of glutathione (GSH) after 48 hr culture. Neither oxidized form of GSH (GSSG) nor other antioxidants, however, could support the embryonic development in the presence of bOF. From these results, it is suggested that bOF contains a protein-like factor(s) which becomes embryotoxic by exposing in vitro, probably via oxidation reaction.

• Korean Journal of Plant Resources
• /
• v.23 no.2
• /
• pp.145-150
• /
• 2010

To examine the antioxidative effect and melanogenesis of Nelumbo nucifera stamen (NNS) extract on hydrogen peroxide $H_2O_2$ induced cytotoxicity in cultured human skin melanoma cells (SK-MEL-3), cell adhesion activity (CAA), tyrosinase inhibitory activity and total amount of melanin synthesis were measured by colorimetric assay. In this study, $H_2O_2$ significantly decreased CAA, and $CAA_{50}$ value of $H_2O_2$ was determined at 30 uM. In the antioxidative effect, NNS extract increased cell adhesion activity which was decreased by $H_2O_2$ induced cytotoxicity, and also, tyrosinase activity and total amount of melanin were decreased by NNS extract. These results suggested that $H_2O_2$ was highly toxic on cultured human skin melanoma cells and NNS extract showed the antioxidative and inhibitory effect of melanogenesis by the increased CAA, and the decresed tyrosinase activity and total amount of melanin synthesis.

• Clean Technology
• /
• v.12 no.2
• /
• pp.87-94
• /
• 2006

The reduction of $SO_2$ to elemental sulfur by CO over a series of iron niobate with nominal Nb/Fe atomic ratios of 1/0, 10/1, 5/1, 1/1, 1/5, 1/10 and 0/1 was studied with a flow fixed-bed reactor. Strong synergistic phenomena in catalytic activity and selectivity were observed for the iron niobate catalysts, and the best catalytic performance was observed for the catalyst with Fe/Nb atomic ratio of 1/1. The active phase of the activated iron niobate catalysts was identified to be $FeS_2$ using XRD and XPS. Selective reduction of $SO_2$ by CO was followed by the COS intermediate mechanism.

• Environmental Analysis Health and Toxicology
• /
• v.15 no.4
• /
• pp.139-145
• /
• 2000

The Flavin-containing monooxygenase (FMOs) (EC1.14.13.8) are NADPH-dependent flavoenzymes that catalyze oxidation of soft nucleophilic heteroatom centers in a range of structurally diverse compounds, including foods, drugs, pesticides, and other xenobiotics. In humans, FMO3 is quantitatively a major human liver monooxygenase. In the present study, the baculovirus expression vector system was used to overexpress human FMO3 in insect cells for catalytic studies. Six commercially available organic selenium compounds were examined for substrate activity with microsomes isolated from Spodoptera frugiperda (Sf)9 cells infected with human FMO3 recombinant baculovirus. While none of the aromatic heterocyclic selenides tested showed detectable activity, all dialkyl- and alkylaryl-selenides free from ionic groups catalyzed the NADPH- and O$_2$-dependent oxidation. Kinetic constants demonstrate that (based on Km) dialkyl-and alkylaryl- selenides are better substrates for human FMO3 than analogous nitrogen or sulfur compounds .

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.35 no.10
• /
• pp.1329-1335
• /
• 2006

LP-BM5 murine leukemia retrovirus induces the excessive oxidative stress and immune dysfunction leading to B cell leukemia and murine AIDS with cytokine dysfunction. In the present study, the immune restoratory effect of antioxidant hormone dedydroepiandrosterone sulfate (DHEAS) was investigated in the primary splenocytes from LP-BM5 retrovirus-infected C57BL/6 mice. DHEAS significantly increased T and B cell response to mitogen and normalized the unbalanced production of Th1/Th2 type cytokines. In particular, both protein and mRNA expression of IL-4, IL-6, and $TNF-\alpha$ were down-regulated by DHEAS treatment whereas IL-2 and $IFN-\gamma$ level were increased. This result suggests that DHEAS directly or indirectly regulates the gene expression of Th1/Th2 type cytokines in transcription level. In addition, DHEAS treatment decreased the hepatic lipid peroxidation and preserved vitamin E level in liver cells. These results suggested that DHEAS could effectively prevent immune dysfunction by regulating cytokine secretion and preventing the oxidative stress in murine AIDS.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.7
• /
• pp.746-752
• /
• 2005

In this study, the effect of reaction parameters including reaction temperature, time, and pressure on sludge degradation and conversion to intermediates such as organic acids were investigated at low critical wet air oxidation(LC-WAO) conditions. Degradation pathways and a modified kinetic model in LC-WAO were proposed and the kinetics model predictions were compared with experimental data under various conditions. Results in the batch experiments showed that reaction temperature directly affected the thermal hydrolysis reaction rather than oxidation reaction. The efficiencies of sludge degradation and organic acid formation increased with the increase of the reaction temperature and time. The removal of SS at $180^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$ and $240^{\circ}C$ of reaction temperatures and 10 min of reaction time were 52.6%, 68.3%, 72.6%, and 74.4%, respectively, indicating that most organic suspended solids were liquified at early stage of reaction. At $180^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$ and $240^{\circ}C$ of reaction temperatures and 40 min of reaction time, the amounts of organic acids formed from 1 g of sludge were 93.5 mg/g SS, 116.4 mg/g SS, 113.6 mg/g SS, and 123.8 mg/g SS, respectively, and the amounts of acetic acid from 1 g of sludge were 24.5 mg/g SS, 65.5 mg/g SS, 88.1 mg/g SS, and 121.5 mg/g SS, respectively. This suggested that the formation of sludge to organic acids as well as the conversion of organic acids to acetic acid increased with reaction temperature. Based on the experimental results, a modified kinetic model was suggested for the liquefaction reaction of sludge and the formation of organic acids. The kinetic model predicted an increase in kinetic parameters $k_1$ (liquefaction of organic compounds), $k_2$ (formation of organic acids to intermediate), $k_3$ (final degradation of intermediate), and $k_4$ (final degradation of organic acids) with reaction temperature. This indicated that the liquefaction of organic solid materials and the formation of organic acids increase according to reaction temperature. The calculated activation energy for reaction kinetic constants were 20.7 kJ/mol, 12.3 kJ/mol, 28.4 kJ/mol, and 54.4 kJ/mol, respectively, leading to a conclusion that not thermal hydrolysis but oxidation reaction is the rate-limiting step.

• Journal of Korean Society of Environmental Engineers
• /
• v.35 no.6
• /
• pp.415-421
• /
• 2013

To increase specific surface property of activated carbon fiber(ACF), chemical activation(CA) using alkali metals and surface treatment(ST) using oxidant was widely used. The CA and ST process developed micro-pore on the surface of ACF by chemical reaction of the alkali metals and oxidative of oxidant, respectively. To improve the efficiency of CA process for developing micro-pores on the surface of ACF, the ST process was adopted as an pre-treatment method. After treatment of ST process, ACF properties was investigated depending on the ST pre-treatment process. FT-IR, TG and elemental analysis of the ACF are carried out, and an adsorption property of ACF was also evaluated using toluene(which in typical volatile organic matter). Once the single CA process is used, the surface area and adsorption capacity of ACF were increased from 1,483 to 1,988 $m^2/g$ and from 0.22 to 0.27 $g_{-Tol.}/g_{-ACF}$, respectively. On the other hands, once the ST and CA processes are used successively, the surface area and adsorption capacity of ACF are greatly increase(where the surface area is 2,743 $m^2/g$ and the adsorption capacity is 0.37 $g_{-Tol.}/g_{-ACF}$). It indicates that the combined process of ST and CA can improve the surface process properties of ACF.

• Journal of the Microelectronics and Packaging Society
• /
• v.25 no.4
• /
• pp.75-81
• /
• 2018

The effect of $Ar-N_2$ plasma treatment on Cu surface as one of solutions to realize reliable Cu-Cu wafer bonding was investigated. Structural characteristic of $Ar-N_2$ plasma treated Cu surface were analyzed using X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscope. Ar gas was used for a plasma ignition and to activate Cu surface by ion bombardment, and $N_2$ gas was used to protect the Cu surface from contamination such as -O or -OH by forming a passivation layer. The Cu specimen under high Ar partial pressure plasma treatment showed more copper oxide due to the activation on Cu surface, while Cu surface after high $N_2$ gas partial pressure plasma treatment showed less copper oxide due to the formation of Cu-N or Cu-O-N passivation layer. It was confirmed that nitrogen plasma can prohibit Cu-O formation on Cu surface, but nitrogen partial pressure in the $Ar-N_2$ plasma should be optimized for the formation of nitrogen passivation layer on the entire surface of Cu wafer.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.34 no.2
• /
• pp.73-77
• /
• 2024

The spinel-type oxide (Ni_x, Mn_y, Co_3-x-y)O₄ (NMC) is widely utilized as a material for temperature sensors with a negative temperature coefficient (NTC), finding applications across various industries including electric vehicle battery management systems. Typically, NMC is manufactured using solid-state reaction methods employing powders of Ni, Mn, and Co compounds, with the densification process through sintering recognized as a crucial factor determining the electrical properties of the temperature sensor material. In this study, NMC pellets were synthesized via solid-state reaction and their crystallographic and microstructural characteristics were investigated. Also, the activation energy for densification behavior during the sintering process was determined. According to the analysis results, the room temperature resistance of the NMC pellets was measured at 10.03 Kohm, with the sensitivity parameter, B-value, recorded at 3601.8 K, indicating their potential applicability as temperature sensors across various industrial fields. Furthermore, the activation energy for densification was found to be 273.3 ± 0.4 kJ/mol, providing valuable insights into the thermodynamic aspects of the sintering process of the NMC.