• 한국자기학회:학술대회 개요집
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• 한국자기학회 2004년도 동계학술연구발표회 논문개요집
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• pp.36-37
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• 2004

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2371-2374
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• 2014

A kinetic study is reported on SNAr reaction of 1-fluoro-2,4-dinitrobenzene with a series of primary amines including hydrazine in $H_2O$ at $25.0^{\circ}C$. The plots of $k_{obsd}$ vs. [amine] are linear and pass through the origin, indicating that general-base catalysis by a second amine molecule is absent. The Br${\o}$nsted-type plot exhibits an excellent linear correlation with ${\beta}_{nuc}$ = 0.46 when hydrazine is excluded from the correlation. The reaction has been suggested to proceed through a stepwise mechanism, in which expulsion of the leaving group occurs after the rate-determining step (RDS). Hydrazine is ca. 10 times more reactive than similarly basic glycylglycine (i.e., the ${\alpha}$-effect). A five-membered cyclic intermediate has been suggested for the reaction with hydrazine, in which intramolecular H-bonding interactions would facilitate expulsion of the leaving group. However, the enhanced leaving-group ability is not responsible for the ${\alpha}$-effect shown by hydrazine because expulsion of the leaving group occurs after RDS. Destabilization of the ground-state of hydrazine through the electronic repulsion between the nonbonding electron pairs is responsible for the ${\alpha}$-effect found in the current $S_NAr$ reaction.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2443-2447
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• 2014

A kinetic study is reported on nucleophilic substitution reactions of 4-nitrophenyl nicotinate (7) and 4-nitrophenyl isonicotinate (8) with a series of cyclic secondary amines in $H_2O$ containing 20 mol % DMSO at $25.0^{\circ}C$. The Br${\o}$nsted-type plots for the reactions of 7 and 8 are linear with ${\beta}_{nuc}=0.90$ and 0.92, respectively, indicating that the reactions proceed through a stepwise mechanism with expulsion of the leaving group occurring in the rate-determining step. Comparison of the reactivity of 7 and 8 with that of 4-nitrophenyl benzoate (2a) and 4-nitrophenyl picolinate (6) has revealed that their reactivity toward the amines increases in the order 2a < 7 < 8 < 6, although the reactions of these substrates proceed through the same mechanism. Factors that control reactivity and reaction mechanism have been discussed in detail (e.g., inductive and field effects, H-bonding interaction, solvent effect, etc.).

• Food Science and Biotechnology
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• 제18권4호
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• pp.996-1000
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• 2009

Sapium japonicum was extracted by a pressurized liquid. Operating parameters such as the type and the ratio of solvent to water, temperature, pressure, and number of extractions were investigated as the main variables that influence the extraction efficiencies of total phenolics (TP). MeOH extracted the highest level of TP as 50.4 mg GAE/g compared to 48.8 and 27.2 mg GAE/g with $H_2O$ and EtOH, respectively. $EtOH:H_2O$ (40:60, v/v) was found to be the best solvent for TP extraction as 90.3 mg GAE/g compared to 85.0 and 84.3 mg GAE/g in 40:60 and 60:40 of $MeOH:H_2O$, respectively. TP were increased with the increase of the number of extraction steps. TP content was increased by 11% as the extraction temperature was increased from 40 (97.4) to $50{\circ}C$ (108.3 mg GAE/g). The optimum extraction conditions of TP were; extraction solvent, $EtOH:H_2O$ (40:60, v/v); temperature, $50{\circ}C$; pressure, 10.2 MPa; 2 extraction steps.

• E2M - 전기 전자와 첨단 소재
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• 제16권9호
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• pp.63.2-64
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• 2003

Epitaxial yttrium-stabilized HfO$_2$ thin films were deposited on p-type (100) Si substrates by pulsed laser deposition at a relatively lower substrate temperature of 550. Transmission electron microscopy observation revealed a fixed orientation relationship between the epitaxial film and Si; that is, (100)Si.(100)HfO$_2$ and [001]Si/[001]HfO$_2$. The film/Si interface is not atomically flat, suggesting possible interfacial reaction and diffusion, X-ray photoelectron spectrum analysis also revealed the interfacial reaction and diffusion evidenced by Hf silicate and Hf-Si bond formation at the interface. The epitaxial growth of the yttrium stabilized HfO$_2$ thin film on bare Si is via a direct growth mechanism without involoving the reaction between Hf atoms and SiO$_2$ layer. High-frequency capacitance-voltage measurement on an as-grown 40-A yttrium-stabilized HfO$_2$ epitaxial film yielded an dielectric constant of about 14 and equivalent oxide thickness to SiO$_2$ of 12 A. The leakage current density is 7.0${\times}$ 10e-2 A/$\textrm{cm}^2$ at 1V gate bias voltage.

• Tuberculosis and Respiratory Diseases
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• 제40권3호
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• pp.236-249
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• 1993

연구배경 : 정상 폐상피세포에서는 항상 생성되고 있는 활성산소(oxygen radical)에 의한 유해작용에 노출되어 있고, 이들 유해 산소들은 폐기종과 같은 폐질환의 원인 기전으로 생각되고 있다. 본 연구에서는 이 방법을 이용하여 만든 폐상피세포 단일막에서 전기생리학적인 관점에서 물질의 이동지표인 short-circuit current(Isc)와 조직저항(R)에 대한 활성산소의 하나인 $H_2O_2$(hydrogen peroxide)가 어떤 영향을 미치는지를 연구함으로서 세포생리학적 기전을 구명하고자 한다. 방법 : Tissue culture-treated polycarbonant membrane filter 에서 배양시킨 쥐 제 2 형 폐상피세포 배양 단일막에서 $H_2O_2$의 능동적 이온 이동 (Isc) 과 수동적 용질이동에 대한 조직저항(R)에 미치는 효과를 관찰하였다. 배양 제 3 일과 제 4 일째 단일막을 수정된 Ussing chamber에 설치하고 막 양측에 HEPES-buffered Ringer 용액으로 incubation 하였다. 외부에서 0~100 mM 농도의 $H_2O_2$를 apical 또는 basolateral side에 작용시켜 Isc와 R의 변화를 관찰하였다. 폐상피세포 장벽이 외부의 $H_2O_2$에 대하여 방어작용을 가지는 세포내 catalase 활성도를 측정하고, catalase 억제제인 aminotriazol(ATAZ) 20 mM의 효과도 함께 관찰하였다. 결과 : 이 단일막은 형태학적으로 보아서 in vivo 에서의 포유류 제 1 형 폐상피세포 장벽의 특성을 나타내고 세포들 사이는 tight junction을 이루며(조직저항 R: 2,000 ohm-$cm^2$ 이상) sodium ion의 능동적 이동 (Isc: 5 ${\mu}A/cm^2$)을 보였다. $H_2O_2$는 dose-dependent 양식으로 Isc와 R 모두 감소시켰다. Apical side에 작용하는 $H_2O_2$에 있어서는 60분에 50% 억제하는 농도인 $ED_{50}$는 Isc와 R은 약 4mM 이었으나 basolateral side의 경우는 약 0.04mM 로서 그 작용 강도는 apical에 비하여 약 100배 정도 더 컸다. ATAZ 존재시 apical side의 $ED_{50}$는 0.4mM로 감소하였으나 basolateral side의 경우 변화가 없었다. $H_2O_2$의 제거율은 apical 또는 basolateral side 어느 쪽에 존재하든 같았으며, 세포내 catalase 활성도는세포배양기간이 길어짐에 따라 증가함을 보였다. 결론 : 이상의 실험결과는 basolateral side에 작용하는 $H_2O_2$는 세포내 막구성성분 중 basolateral 측에 존재하는 곳에(예, $Na^+,\;K^+$-APTase) 직접 장애를 미칠 것으로 생각된다. 한편 apical side에 작용하는 $H_2O_2$는 막성분에 도달하기 전에 세포내에 존재하는 catalase에 의하여 대부분 그 작용을 잃게 된다. 결론적으로 Isc와 R로 측정된 폐상피세포 장벽의 특성은 $H_2O_2$에 의하여 손상을 받고 apical side 보다는 basolateral side 측정이 더 손상을 잘 받게 된다.

• 지구물리
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• 제7권2호
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• pp.113-120
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• 2004

Hydrochemical characteristics of deep groundwater at Surak-ri, Nonsan-gun, Chungnam Province was explained by major ion concentration, water type, and phase stability diagram. The area is composed of meta-sedimentary rock and quartz pophyry. The 5 boreholes where deep groundwater was sampled and analyzed are located on the meta-sedimentary rocks and drilling depth range of the wells is from 554 m to 928 m. pH, TDS, Na, and SiO2 values are high in the groundwater from meta-sedimentary area intruded by quartz pophyry, while Ca is high in the groundwater from meta-sedimentary area. K and Mg concentrations are low but F concentration is high both groundwater. The content of major anions is in the order of CO3(HCO3)>Cl>SO4(F) in both geology, while that of major cations shows the order of Na>Ca>K(Mg) in meta-sedimentary area intruded by quartz porphyry and a>Na>Mg>Na in meta-sedimentary area. Based on the phase equilibrium in the systems Na2O-Al2O3-SiO2-H2O and K2O-Al2O3-SiO2-H2O, the groundwater is saturated with respect to Quartz and more evolved compared with the natural mineral water. It is concluded that chemical evolution in the groundwater from meta-sedimentary area intruded by quartz porphyry, is nearly saturated with respect to feldspar, while the groundwater from meta-sedimentary area continue to proceed with increasing pH by reaction of feldspar.

• Bulletin of the Korean Chemical Society
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• 제19권10호
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• pp.1090-1094
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• 1998

Acid-catalyzed benzidine rearrangements of new unsymmetrical diazanes 1-3, prepared from the reduction of corresponding diazenes 4-6, were carried out in ethanolic solutions. The results are as follows; rearrangement of (3-carbomethoxyphenyl)(3-methoxyphenyl)diazane 1 gave 4,4'-diamino-2-carbomethoxy-2'-methoxybiphenyl 12 (p-benzidine type) in 71% and 10-amino-3-methoxyphenanthridin-6(5H)-one 13, 8-amino-3-methoxyphenanthridin-6(5H)-one 14 in 7.1% and 3.4%, respectively. Product 13 and 14 were formed by the condensation reaction of primarily formed o-benzidine and diphenyline type product, respectively. (5-Carbomethoxy-2-chlorophenyl)(4-methoxyphenyl)diazane 2 and (5-carbomethoxy-2-methylphenyl)(4-methoxyphenyl)diazane 3 underwent mainly disproportionations to give fission amines and corresponding diazenes in about 53% and 40% yields, respectively. The results obtained from the rearrangements of diazanes 1-3 indirectly indicated the importance of disproportionations to understand the benzidine rearrangements. The structures of benzidine rearrangement products were determined by usual NMR techniques such as DEPT, 2D H-H COSY, H-C COSY, 2D NOESY, and Gaussian function multiplication.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.48-51
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• 2004

In this paper the importance of re-nitridation on a plasma-enhanced chemical-vapor deposited(PECVD) $SiO_2$ stacked on a thermally grown thin-nitrided $SiO_2$ on n-type 4H SiC have been investigated. Without the final re-nitridation process, the leakage current of metaloxidesemiconductor(MOS) was extremely large. It is believed that water and carbon, contamination from the low-thermal budget PECVD process, are the main factors that destroyed the high quality thin-buffer nitrided oxide. After re-nitridation annealing, the quality of the stacked gate oxide was improved. The reasons of this improvement are presented.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2403-2407
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• 2009

Second-order rate constants have been measured for two series of nucleophilic displacement reactions, i.e., reactions of 4-nitrophenyl benzoate with Z-substituted phenoxides and those of Y-substituted phenyl benzoates (1a-h) with 4-chlorophenoxide (4-ClPhO–) in 80 mol% $H_2O$/20 mol% DMSO at 25.0 ${\pm}\;0.1\;{^{\circ}C}$. The Br$\phi$nsted-type plot for reactions of 4-nitrophenyl benzoate with Z-substituted phenoxides exhibits an excellent linear correlation with ${\beta}_{nuc}$ = 0.72. Reactions of 1a-h with 4-chlorophenoxide result in also a linear Br$\phi$nsted-type plot with ${\beta}_{lg}$ = –0.62, a typical ${\beta}_{lg}$ value for a concerted mechanism. The Hammett plots correlated with ${\sigma}^o\;and\;{\sigma}^-$ constants show many scattered points for reactions of 1a-h with 4-chlorophenoxide. In contrast, the corresponding Yukawa-Tsuno plot exhibits an excellent linear correlation with $\rho_Y$ = 2.26 and r = 0.53, indicating that expulsion of the leaving group occurs at the rate-determining step (RDS) either in a concerted mechanism or in a stepwise pathway. However, a stepwise mechanism with leaving group departure being the RDS is excluded since the leaving Y-substituted phenoxide is less basic and a better nucleofuge than the incoming 4-ClPh$O^-$. Thus, the reactions have been concluded to proceed through a concerted mechanism, in which bond formation between the nucleophile and electrophilic center is more advanced than expulsion of the leaving group in the transition state on the basis of the magnitude of ${\beta}_{nuc}\;and\;{\beta}_{lg}$ values.