• Corrosion Science and Technology
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• 제3권5호
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• pp.198-208
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• 2004

Although there has been no general agreement on the mechanism of primary water stress corrosion cracking (PWSCC) as one of major degradation modes of Ni-base alloys in pressurized water reactors (PWR's), common postulation derived from previous studies is that the damage to the alloy substrate can be related to mass transport characteristics and/or repair properties of overlaid oxide film. Recently, it was shown that the oxide film structure and PWSCC initiation time as well as crack growth rate were systematically varied as a function of dissolved hydrogen concentration in high temperature water, supporting the postulation. In order to understand how the oxide film composition can vary with water chemistry, this study was conducted to characterize oxide films on Alloy 600 by an in-situ Raman spectroscopy. Based on both experimental and thermodynamic prediction results, Ni/NiO thermodynamic equilibrium condition was defined as a function of electrochemical potential and temperature. The results agree well with Attanasio et al.'s data by contact electrical resistance measurements. The anomalously high PWSCC growth rate consistently observed in the vicinity of Ni/NiO equilibrium is then attributed to weak thermodynamic stability of NiO. Redox-induced phase transition between Ni metal and NiO may undermine the integrity of NiO and enhance presumably the percolation of oxidizing environment through the oxide film, especially along grain boundaries. The redox-induced grain boundary oxide degradation mechanism has been postulated and will be tested by using the in-situ Raman facility.

• 대한화학회지
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• 제29권3호
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• pp.257-264
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• 1985

메탄올 용액에서 3-메톡시살리실알데히드와 몰리브덴산암모늄으로 부터 디옥소비스메톡시살리실알데히다토 몰리브데늄(VI) 착물을 합성하고 이를 일차아민과 반응시켜 MoO$_2$(CH$_3$O-sal-N-R)$_2$, (R;일차아민)형의 시프-염기착물을 합성하였다. 이들에 대한 원소분석, 스펙트라의 해석 그리고 전기전도도의 측정으로 부터 착물의 성질과 그 구조를 추정하였다. 적외선 스펙트라에서 Mo=O 신축진동에 기인한 두 개의 흡수띠가 900cm$^{-1}$부근에서 관찰되었으며 이는 Mo(VI) 착물이 cis-MoO$_2$형으로 되어있음을 나타낸다. 또한 MoO$_2$와 배위자 사이의 결합비가 1:2임을 알 수 있었다. 이들 착물의 전자스펙트라에서 배위자로부터 금속으로 전하이동전이가 일어났다. 이들 착물은 노란색 혹은 오렌지색깔을 띠며 비극성물질로서 알코올이나 디클로로메탄, 클로로포름 및 디메틸프름 아마이드에 약간 녹인다.

• 대한화학회지
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• 제33권1호
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• pp.90-96
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• 1989

피리디니움 옥소이소치오시안네이토 몰리브테이트(V)와 아민 카르복실기를 가진 1,2-Diaminohexane-N,N,N'-tetracetic acid 유도체를 반응시켜 아민 카르복실기를 가진 디옥소-디-뉴우-옥소-디몰리브테이트(V) 착물을 합성하였다. 이들에 대한 원소분석, 스펙트라의 해석 그리고, 전기전도도의 측정으로부터 착물의 성질과 그 구조를 추정하였다. 적외선 스펙트라에서 Mo=$O_t$ 신축진동에 기인한 두 개의 흡수띠가 $900-965cm^{-1}$ 영역에서 관찰되었으며, MoO$_2$Mo의 비대칭 신축진동 및 대칭 신축진동은 $740-765 cm^{-1}$, $450-500cm^{-1}$에서 각각 나타났었고, 카르복실기와 금속 결합간의 비대칭 신축 진동이 $1600-1635 cm^{-1}$에서 흡수띠가 관찰되었다. 이들 착물은 노란색 혹은 오렌지색이며 반자성체 물질이였다.

• 대한화학회지
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• 제31권6호
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• pp.520-526
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• 1987

피리디니움 옥소이소치오시안네이토 몰리브데이트(V)와 아민 카르복실기를 가진 이미노디아세틱액시드 유도체를 반응시켜 아민 카르복실기를 가진 디옥소-디-뉴우-옥소-디몰리브데이트(V) 착물을 합성하였다. 이들에 대한 원소분석, 스펙트라의 해석 그리고 전기전도도의 측정으로 부터 착물의 성질과 그 구조를 추정하였다. 적외선 스펙트라에서 $Mo=O_t$ 신축진동에 기인한 두 개의 흡수띠가 900~$980cm^{-1}$ 영역에서 관찰되었으며, $MoO_2Mo$의 비대칭신축진동 및 대칭신축진동은 720~$750cm^{-1}$, 440~$485cm^{-1}$ 에서 각각 나타났었고, 카르복실기와 금속결합간의 비대칭 신축진동이 1585~$1,640cm^{-1}$에서 흡수띠가 관찰되었다. 전자흡수스펙트럼 결과 $^2B_2{\to}^2B_1$의 결정장 전이는 24,800∼$28,000cm^{-1}$, 전하이동 전이는 32,500~$33,800cm^{-1}$, 42,000~$47,500cm^{-1}$에서 각각 나타났다. 이들 착물은 노란색 혹은 오렌지색이며 반자성체 물질이였다.

• Journal of Ginseng Research
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• 제44권2호
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• pp.215-221
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• 2020

Background: Panax ginseng has been used for a variety of medical purposes in eastern countries for more than two thousand years. From the extensive experiences accumulated in its long medication use history and the substantial strong evidence in modern research studies, we know that ginseng has various pharmacological activities, such as antitumor, antidiabetic, antioxidant, and cardiovascular system-protective effects. The active chemical constituents of ginseng, ginsenosides, are rich in structural diversity and exhibit a wide range of biological activities. Methods: Ginsenoside constituents from P. ginseng flower buds were isolated and purified by various chromatographic methods, and their structures were identified by spectroscopic analysis and comparison with the reported data. The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H- tetrazolium bromide method was used to test their cytotoxic effects on three human cancer cell lines. Results: Six ginsenosides, namely 6'-malonyl formyl ginsenoside F₁ (1), 3β-acetoxyl ginsenoside F₁ (2), ginsenoside Rh₂₄ (6), ginsenoside Rh₂₅ (7), 7β-hydroxyl ginsenoside Rd (8) and ginsenoside Rh₂₆ (10) were isolated and elucidated as new compounds, together with four known compounds (3-5 and 9). In addition, the cytotoxicity of these isolated compounds was shown as half inhibitory concentration values, a tentative structure-activity relationship was also discussed based on the results of our bioassay. Conclusion: The study of chemical constituents was useful for the quality control of P. ginseng flower buds. The study on antitumor activities showed that new Compound 1 exhibited moderate cytotoxic activities against HL-60, MGC80-3 and Hep-G2 with half inhibitory concentration values of 16.74, 29.51 and 20.48 μM, respectively.

• Journal of Ginseng Research
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• 제44권1호
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• pp.145-153
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• 2020

Background: Panax ginseng Meyer (Araliaceae) is a highly valued medicinal plant in Asian regions, especially in Korea, China, and Japan. Chemical and biological studies on P. ginseng have focused primarily on its roots, whereas the seeds remain poorly understood. This study explores the phytochemical and biological properties of compounds from P. ginseng seeds. Methods: P. ginseng seeds were extracted with methanol, and 16 compounds were isolated using various chromatographic methods. The chemical structures of the isolates were determined by spectroscopic data. Antiinflammatory activities were evaluated for triterpene and steroidal saponins using lipopolysaccharide-stimulated RAW264.7 macrophages and THP-1 monocyte leukemia cells. Results: Phytochemical investigation of P. ginseng seeds led to the isolation of a novel triterpene saponin, pseudoginsenoside RT₈, along with 15 known compounds. Pseudoginsenoside RT₈ exhibited more potent antiinflammatory activity than the other saponins, attenuating lipopolysaccharide-mediated induction of proinflammatory genes such as interleukin-1β, interleukin-6, inducible nitric oxide synthase, cyclooxygenase-2, and matrix metalloproteinase-9, and suppressed reactive oxygen species and nitric oxide generation in a dose-dependent manner. Conclusion: These findings indicate that pseudoginsenoside RT₈ has a pharmaceutical potential as an antiinflammatory agent and that P. ginseng seeds are a good natural source for discovering novel bioactive molecules.

• Archives of Pharmacal Research
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• 제19권6호
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• pp.480-485
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• 1996

Brain GABA transaminase is inactivated by preincubation with antidepressant/antipanic drug pheneizine (${\beta}$ethylphenylhydrazine) (mixing molar ratio 10:1) at pH 7.4. The reaction of enzyme with phenelzine was monitored by absorption and fluorescence spectroscopic methods. The inactive enzyme was fully reconstituted by addition of cofactor pyridoxal-5-phosphate. This result implies that the blocking of 1 mol of pyridoxal-5-phosphate per enzyme dimer is needed for inactivation of the enzyme. The time course of the reaction is significantly affected by the substrate .alpha.-ketoglutarate, which afforded complete protection against the loss of catalytic activity. The kinetic studies shows that phenelzine reacts with the cofactor of enzyme with a second-order rate constant of $2.1{\times}10^3M^{-1}s^{-1}$. It is postulated that the antidepressant/antipanic drug phenelzine is able to elevate the neurotransmitter GABA levels in central nervous system by inhibitory action on GABA degradative enzyme GABA transaminase.

• The Korean Journal of Ceramics
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• 제2권2호
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• pp.102-110
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• 1996

The Mg-PSZ/$Al_2O_3$ fibers were fabricated by the sol-gel method. The added $Al_2O_3$ amounts were varied from 5 to 20 mol%. The phase transformation studies of a drawn Mg-PSZ/$Al_2O_3$ fibers were investigated by use of X-ray diffraction, IR and Raman spectroscopy. Microstructure and tensile strength of fibers were subjected to scanning electron microscopy and tensile strength tester. When $Al_2O_3$ was added to the Mg-PSZ fibers, it was found out from the analysis of XRD patterns and Raman spectra that a small amount of crystalline spinel($MgAl_2O_4$) started to form due to the reaction between $Al_2O_3$ and MgO, at $1000^{\circ}C$, and the phase transformation temperature of $ZrO_2$ crystal phase at different sintering temperatures increased. Also, the rapid grain growth with average size of 2.0 ${\mu}m$ shown in Mg-PSZ fiber at $1500^{\circ}C$ was considerably suppressed to 0.39 ${\mu}m$ by adding $Al_2O_3$ at the same temperature. When the Mg-PSZ/$Al_2O_3$ fibers containing 5 mol% $Al_2O_3$ were sintered $800^{\circ}C$ for 1 hr, average tensile strength of fibers was 0.9 GPs at diameters of 20 to 30 ${\mu}m$, but as the sintering temperatures was increased to $1000^{\circ}C$ for 1 hr, average tensile strength of fibers increased to 1.2 GPa in the same diameter range.

• Journal of Pharmaceutical Investigation
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• 제27권2호
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• pp.119-123
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• 1997

The physicochemical and structural properties of new capsaicin derivative, DA-5018, were examined. The reference standard of this compound was obtained by the recrystallization. A method for the determination of the dissociation constant of the compound is described. pH-solubility and distribution coefficient were determined by chromatographic method. Fundamental properties on thermal behaviors were investigated by TG, DTA and DSC. Structural analysis based on spectroscopic method coincided with the chemical structure of DA-5018. Approximate dissociation constant of the compound determined by UV spectral method was 9.35. Solubilities and partition coefficients in various pH buffer solution appeared pH-dependency. No crystal transition or further transition was found in the thermal analysis. This compound showed good stability, but pH 13 buffer and acetone made some degradative products.

• 폴리머
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• 제26권5호
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• pp.634-643
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• 2002

고분자 주사슬에 벤젠과 sulfonyloxvimide moiety를 가지고 있는 polyamic acid 초박막을 LB 기법을 이용하여 제조한 다음 200 $^{\circ}C$에서 1시간 동안 열처리에 의해 감광성 폴리이미드 LB 필름을 얻었다. Polyamic acid는 THF-pyridine 공용매를 가지고 축중합에 의해 합성하였다. 모든 단량체와 고분자는 원소분석, FT-IR, $^1$H-NMR의 분광학적 측정을 통해 정량 정성분석을 행하였다. UV lithography 방법을 사용하여 금 기판 위에 제조한 감광성 폴리이미드 LB 필름의 마이크로 어레이 패턴을 제조하였다. 형성된 마이크로 어레이 패턴을 따라 두 가지의 자기조립 방법으로 단백질 cytochrome c 단분자 막을 고정화시켰다. 자기조립된 cytochrome c 단분자 막의 물리ㆍ전기 화학적 특성은 cyclic voltammetry와 AFM을 통해 조사하였으며 생물전자소자로의 응용 가능성에 대해서도 검토하였다.