• 대한약학회:학술대회논문집
• /
• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.1
• /
• pp.241.2-241.2
• /
• 2003

We report the synthesis of key intermediates for the development novel flavonoid derivatives with potential antiinflammatory activity and propose a mechanism of the one-pot reaction. The various amines (1) for this work were commercially available. Secondary amines (2) were formed by nucleophilic attraction using ethyl benzoylacetate. The C-N bond formation proceeded at refluxing in toluene with catalytic amount of p-toluenesulfonic acid and a removal of water was important in this reaction. (omitted)

• 천문학회지
• /
• 제14권1호
• /
• pp.37-42
• /
• 1981

In order to know how the magnetic field increases with density in interstellar clouds, we have analyzed observations of extinction and polarization for stars in the ${\rho}$ Oph molecular cloud complex. The size of grains in dense parts of the complex is estimated to be larger than the ones in diffuse interstellar clouds by about 15 percent in radii. Employing the Davis-Greenstein mechanism for grain alignment with this estimated grain size, we have put constraints on the exponent in the field-density relation $B{\propto}n^x:1/5{\leq}x{\leq}1/3$. It is concluded that magnetic field in gravitationally contracting clouds increases less steeply than the classical expectation based on the approximation of isotropic contraction with complete frozen-in flux.

• 천문학논총
• /
• 제10권1호
• /
• pp.15-30
• /
• 1995

It has been recognized that the morphologies of the SNRs from the radio observation are "barrel shaped". To interpret the mechanism of the radiation and the physical state of the environments, we have analytically calculated the dynamical structure of the interacting region in the case where the ejectum has a steep power-law density profile($\rho{\sim}r^{-n}$) and the ambient medium has a shallow power-law density profile($\rho{\sim}r^{-s}$), assuming that the cosmic rays are isotropically accelerated in the shock wave and the magnetic fields are very weak. The calculated synchrotron radio maps show that the emission from the equator is intense and the emissions from the central and polar regions are less intense. Also the thicknesses of the shell are strongly dependent on s and weakly on n. The azimuthal intensity ratio $\alpha$ increases as the efficiency of the cosmic ray acceleration increases and s decreases. We compared the results with the morphology of the SNR A. D. 1006(type I SNR). It does agree with the case of s = 0, w = 0.3 - 0.5. This value for w is consistent with the results by Eichler(1979). It provides us the evidence of the cosmic ray acceleration in the shock wave.

• 대한화학회지
• /
• 제9권1호
• /
• pp.23-28
• /
• 1965

90% ethanol solution에서 benzyl chloride와 radioactive chloride($^{36}Cl^-$)와의 exchange를 反應速度論的으로 硏究하였으며 그 結果로 交換反應은 typical bimolecular reaction임을 알았고 그 activation parameter들은 각기 다음과 같았다. ${\Delta}H^{\neq}$= 18.50 Kcal ${\Delta}S^{\neq}$= -22.09 e.u. 특히 本實驗 缺課와 다른 實驗結果를 綜合討論함으로써 反應速度는 attacking anion의 nuclephilic ability에 크게 관계 됨을 입증할 수 있었으며 또한 exchange reaction에 있어서 halide들의 reactivity의 순서는 bond dissociation energy의 差로써 보다는 오히려 Swain의 nucleophilic parameter(n)로써 설명함이 더욱 타당함을 알았다.

• 한국식품영양과학회지
• /
• 제23권4호
• /
• pp.698-703
• /
• 1994

In spore rec-assay using B. subtillus H17(rec) and M 45(rec) , the ethanol extract of buckwheat leaves showed antimutagenicity in condition of low concentrations, but its did comutagenicity in condition of high concentrations. In Ames test, the ethanol extract of buckwheat leaves reduced the mtabenicity of N-methyl-N' -nitro-N-nitrosoguaidine (MNNG), benzo (a) pyrene(B($\alpha$)P), 2-amino-fluorene(2AF), and 3-amino -1, 4-dime-thyl-5-H-pyrido(4, 3-b) indol(Trp-P-1) in Salmonella typhimurium TA98 and TA100. The ethanol extract was fractionated by hexane, ethylacetate, butanol and water. Among Them hexane fraction showed the highest inhibition rate on the mutagenicity of B($\alpha$)P, and so did chloroform fraction on the mutagenicity of MNNG in S. typhimurium Ta98 and TA100. To elucidate the antimutagenic mechanism of the ethanol extract, it was mixed and co-incubated with various metagens, S9 mix, and the bacteria with different experimental orders and different reaction times. The ethanol extract did not affect reversion rate of pre-mutated. S.typhimurium. However, when the ethanol extract was added to the mutagens before their interaction with S.typhimurium , it reduced the mutation rate to 152$\pm$12-273$\pm$18 colonies/plates in case of MNNG, and 135$\pm$13-195$\pm$10 colonies/ plates in case of B($\alpha$)P), showing strong desmutagenic activity.

• 대한화학회지
• /
• 제60권1호
• /
• pp.16-20
• /
• 2016

이성분 혼합 용매계인 MeOH-H₂O, EtOH-H₂O, acetone-H₂O, TFE-H₂O에서 biphenyl-4-carbonyl chloride (C₆H₅C₆H₄COCl, 1)의 가용매 분해반응을 25 ℃에서 수행하였다. 이들 속도자료로부터 simple Gunwald-Winstein식을 사용하여 도시하였을 때 분산현상이 나타나는 것을 볼 수 있었다. 분산현상의 개선을 위해 친핵성도 N_T 및 방향족 고리 변수 I가 포함된 extended Gruwald-Winstein 식을 사용하여 도시하였다. 본 연구에서 구한 l, m, h 값 및 비교적 작은 양의 ΔH^‡값(15.3~16.1 kcal/mol)과 비교적 큰 음의 ΔS^‡ 값(−17.2~−20.0 cal/mol·K)의 활성화 파라메타 값으로부터 biphenyl-4-carbonyl chloride의 가용매 분해반응은 해리성 S_N2반응 메카니즘으로 진행됨이 예상되었다.

• Elastomers and Composites
• /
• 제53권4호
• /
• pp.213-219
• /
• 2018

The degradation mechanism and physical properties of an FKM O-ring were observed with thermal aging in this experiment. From X-ray photoelectron spectroscopy (XPS) analysis, we could observe carbon (285 eV), fluoro (688 eV), and oxygen (531 eV) peaks. Before thermal aging, the concentration of fluoro atoms was 51.23%, which decreased to 8.29% after thermal aging. The concentration of oxygen atoms increased from 3.16% to 20.39%. Under thermal aging, the FKM O-ring exhibited debonding of the fluoro-bond by oxidation. Analysis of the C1s, O1s, and F1s peaks revealed that the degradation reaction usually occurred at the C-F, C-F2, and C-F3 bonds, and generated a carboxyl group (-COOH) by oxidation. Due to the debonding reaction and decreasing mobility, the glass transition temperature of the FKM O-ring increased from $-15.91^{\circ}C$ to $-13.79^{\circ}C$. From the intermittent CSR test, the initial sealing force was 2,149.6 N, which decreased to 1,156.2 N after thermal aging. Thus, under thermal aging, the sealing force decreased to 46.2%, compared with its initial state. This phenomenon was caused by the debonding reaction and decreasing mobility of the FKM O-ring. The S-S curve exhibited a 50% increase in modulus, with break at a low strain and stress state. This was also attributed to the decreasing mobility due to thermal aging degradation.

• Journal of Yeungnam Medical Science
• /
• 제19권1호
• /
• pp.39-48
• /
• 2002

n-3 불포화지방산이 관절염의 발생 및 경과에 미치는 영향에 대해 알아보고자 Louvain종 흰쥐를 사용하여, 실험군을 정상군과 면역유도 (콜라겐+incomplete Freund's adjuvant)군으로 나누었고, 면역유도군은 다시 대조군 (정상식이) 및 n-3 다불포화지방산군 (식이에 5% n-3 다불포화지방산 함유) 으로 구분하여, 관절염 유도 1 주일전부터 n-3 다불포화지방산이 함유된 식이를 섭취시켰으며 관절염의 발생여부를 x-ray 소견과 광학현미경적 관찰을 통하여 확인하였다. 면역유도 5 주에 대조군의 38%에서 x-ray 소견상 족부종과 광학현미경상 염증소견이 발견되었으나 n-3 다불포화군에서는 이러한 변화가 없었다. 혈당과 혈장 인슐린은 면역유도나 n-3 다불포화지방산 투여에 의한 변화가 없었으나 혈장 중성지방과 콜레스테롤은 n-3 다불포화지방산투여에 의하여 감소하였다. n-3 다불포화지방산의 투여가 콜라젠에 의한 관절염의 발생을 예방 또는 치료할 수 있을 것으로 생각되며 이의 작용기전을 설명하기 위하여 후속 연구가 요망된다.

• 한국어류학회지
• /
• 제29권2호
• /
• pp.146-150
• /
• 2017

남극 연안에 우점하는 남극암치아목과, 암치아목속 어류 두 종 (Notothenia coriiceps와 Notothenia rossii)의 전장과 무게의 관계를 조사하였다. 어류는 2017년 1월에 남극 킹조지섬에 위치한 세종과학기지 연안에서 낚시로 채집되었다. 총 30마리가 채집된 N. coriiceps의 평균 전장은 266.0 mm였고, 7마리가 채집된 N. rossii의 평균전장은 275.4 mm이었다. 평균 무게의 경우 N. coriiceps는 283.1 g이었고, N. rossii는 290 g이었다. 전장과 무게의 관계를 조사한 결과, 두 종 모두 양의 상대성장 값(b>3)을 보였다. 본 조사에서 얻은 남극 연안에 우점하는 두 종의 크기 자료는 남극 해양생물의 환경적응 기작과 생물학적 대사과정을 이해하기 위한 관련 생리 연구를 수행하는데 있어서, 좋은 기초자료로 활용될 수 있을 것으로 기대된다.

• International Journal of Precision Engineering and Manufacturing
• /
• 제5권2호
• /
• pp.39-45
• /
• 2004

Atomic Force Microscope (AFM) has been widely used in micro/nano-scale studies and applications for the last few decades. In this work, wear characteristics of silicon-based AFM tip was investigated. AFM tip shape was observed using a high resolution SEM and the wear coefficient was approximately calculated based on Archard's wear equation. It was shown that the wear coefficient of Si and ${Si}_3$$N_4$ tips were in the range of ${10}^{-1}$~${10}^{-3}$and ${10}^{-3}$~${10}^{-4}$, respectively. Also, the effect of relative humidity and sliding distance on adhesion-induced tip wear was investigated. It was found that the tip wear has more severe for harder counter surface materials. Finally, the probable wear mechanism was analyzed from the adhesive and abrasive interaction point of view.