• 한국전기전자재료학회논문지
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• 제28권2호
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• pp.80-84
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• 2015

We investigated the dielectric relaxation properties $0.5Ba(Zr_{0.2}Ti_{0.8})O_3-0.5(Ba_{0.7}Ca_{0.3})TiO_3$ ceramics with CuO addition. With increasing CuO addition, the lattice parameter was increased by substitution of small amount $Cu^{2+}$ ion in B-site of $0.5Ba(Zr_{0.2}Ti_{0.8})O_3-0.5(Ba_{0.7}Ca_{0.3})TiO_3$ ceramics. Also the grain size and the maximum dielectric constant of $0.5Ba(Zr_{0.2}Ti_{0.8})O_3-0.5(Ba_{0.7}Ca_{0.3})TiO_3$ ceramics was decreased with increasing amounts of CuO addition. Moreover, the diffused phase transition properties (${\gamma}$) of $0.5Ba(Zr_{0.2}Ti_{0.8})O_3-0.5(Ba_{0.7}Ca_{0.3})TiO_3$ ceramics was increased by compositional fluctuation with increasing of CuO amount, changed from 1.45 at 1 wt% CuO addition to 1.94 at 7 wt% CuO addition.

• 한국자기학회지
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• 제6권2호
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• pp.73-79
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• 1996

Y형 육방정 산화철$(Ba_{2}Me_{2}Fe_{12}O_{22}:Me=천이금속)$은 천이 금속으로 Co와 Zn가 포함된 경우 양호한 고주파 특성을 보이는 것으로 알려져 있다. 따라서, 결정 구조 내에 이들의 분포 상태를 파악하는 것이 중요하다. 본 논문에서는 엄밀한 성분 분석, X-선 회절 분석, 자기 특성 분석을 통하여 확인된 $Co_{2}Y$와 $Co_{1.6}Zn_{0.4}Y$시료에 대한 $M\"{o}ssbauer$ 분광 분석 결과로부터 다음과 같은 결론을 제시하였다. (1) Co는 주로 육방정 산화철의 S-block에 위치한 4배위 자리 $(6c_{IV})$와 S-, T-block 경계의 6배위자리(18h VI)에 들어간다. (2) Co의 일부를 Zn으로 치환하여도, Fe의 분포에는 큰 영향을 미치지 않는다.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.49-53
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• 2013

Second-order rate constants have been measured spectrophotometrically for the reactions of phenyl Y-substituted-phenyl carbonates 7a-g with butane-2,3-dione monoximate ($Ox^-$) in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. The ${\alpha}$-nucleophile $Ox^-$ is 53-95 times more reactive than the corresponding normal-nucleophile 4-$ClPhO^-$ toward 7a-g, indicating that the ${\alpha}$-effect is operative. The magnitude of the ${\alpha}$-effect (e.g., the $k_{Ox^-}/k_{4-ClPhO^-}$ ratio) is independent of the electronic nature of the substituent Y. The cause of the ${\alpha}$-effect for the reactions of 7a-g has been suggested to be ground-state (GS) effect rather than transition-state (TS) stabilization through a six-membered cyclic TS, in which $Ox^-$ behaves a general acid/base catalyst. This idea is further supported by the result that $OH^-$ exhibits negative deviation from the linear Br${\o}$nsted-type plot composed of a series of aryloxides, while $Ox^-$ deviates positively from the linearity. Differential solvation of the GS of $Ox^-$ and 4-$ClPhO^-$ has been suggested to be responsible for the ${\alpha}$-effect exerted by $Ox^-$.

• 한국육종학회지
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• 제42권1호
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• pp.1-10
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• 2010

Five mutants were investigated at the molecular level to determine the factors responsible for mutated endosperm types. They were classified as high (HA) or low amylose (LA) phenotypes based on the amylose content in endosperm. The five were previously produced from Ilpum and Shindongjin cultivar treated with N-methyl-N-nitrosourea and gamma-ray irradiation, respectively. Analysis of the genomic structure and expression of Granule-bounded Starch Synthase I (GBSSI) genes revealed that mutants generally showed a higher incidence of nucleotide transition than transversion, and the $A:T{\rightarrow}G:C$ transition was particularly prevalent. The rates of nucleotide substitution in HA mutants were generally higher than those in the LA mutants, leading to higher substitutions of amino acid in the HA mutants. Neither nucleotide substitutions interfering with intron splicing or causing early termination of protein translation were found, nor any large-sized deletions or additions were found in all the mutants. In principle, amylose content can be regulated by three factors: internal alterations of GBSSI protein, the strength of gene expression, and other unknown external factors. Our results indicate that the endosperm mutants from Shindongjin arose from internal alterations of GBSSI proteins, which may be the result of amino acid substitutions. On the other hand, the Ilpum mutants might be principally caused by the alteration of gene expression level. Analysis of another three glutinous cultivars revealed that the major factor leading to glutinous phenotypes is the 23-bp duplicative motif (5'-ACGGGTTCCAGGGCCTCAAGCCC-3') commonly found in exon 2, which results in the premature termination of protein translation leading to the production of a non-functional GBSSI enzyme.

• Bulletin of the Korean Chemical Society
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• 제26권5호
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• pp.776-780
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• 2005

The kinetic studies of the reactions of $\alpha$-chloroacetanilides $(YC_6H_4NRC(=O)CH_2Cl;\;R=H\;(4)\;and\;CH_3$ (5)) with pyridines have been carried out in dimethyl sulfoxide at 95 ${^{\circ}C}$. The pyridinolysis rates are faster with 4 than with 5 whereas the aminolysis rates with benzylamines are faster with 5 than with 4. The Brønsted ${\beta}_X$ values are in the range from 0.30 to 0.32 and the cross-interaction constants, $\rho_{XY}$, are small negative values; $\rho_{XY}$ = -0.06 and -0.10 for 4 and 5, respectively. Based on these and other results, the pyridinolyses of $\alpha$-chloroacetanilides are proposed to proceed via a stepwise mechanism with rate-limiting addition of the nucleophile to the carbonyl group to form zwitterionic tetrahedral intermediate ($T^{\pm}$) followed by a bridged type transition state to expel the leaving group.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.1037-1041
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• 2012

The nucleophilic substitution reactions of (2R,4R,5S)-(+)-2-chloro-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholidine 2-sulfide (3) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at $5.0^{\circ}C$. The anilinolysis rate of 3 involving a cyclic five-membered ring is considerably fast because of small negative value of the entropy of activation (${\Delta}S^\neq=-2cal\;mol^{-1}\;K^{-1}$) over considerably unfavorable enthalpy of activation (${\Delta}H^\neq=18.0\;kcal\;mol^{-1}$). Great enthalpy and small negative entropy of activation are ascribed to sterically congested transition state (TS) and bulk solvent structure breaking in the TS. A concerted $S_N2$ mechanism with a backside nucleophilic attack is proposed on the basis of the secondary inverse deuterium kinetic isotope effects, $k_H/k_D$ < 1.

• The Korean Journal of Ceramics
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• 제1권1호
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• pp.21-28
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• 1995

Electrical conductivity of $TiO_2$ thin films, deposited on $Al_2O_3$ substrates by metal organic chemical vapor deposition (MOCVD), was measured by four-point probe method in a temperature range from $800^{\circ}C$ to $1025^{\circ}C$ and an oxygen partial pressure range from $2.7{\times}10^{-5}$ atm to 1 atm. In the low oxygen partial pressure region n-type conduction was dominant, but in the high oxygen partial pressure region p-type conduction behavior appeared due to substitution of Ti ions by Al ions, which were diffused from the substrate during post deposition annealing process. Electrical conductivity of the film decreases in the n-type region and increases in the p-type region as the oxygen partial pressure increases. The transition points, which show the minimum conductivity, shifted to the higher oxygen partial pressure region as the measuring temperature increased, but it shifted to lower oxygen partial pressure region with an increase in the post annealing temperature. The results were also discussed with the possible defect models.

• 한국세라믹학회지
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• 제32권2호
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• pp.239-247
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• 1995

Chalcogenide glasses with compositions of Ge10Se90-xTex(X=0~50 at.%) were prepared in order to investigate the effects of Te substitution on the transmission characteristics of Ge-Se glasses in the 8~12 ${\mu}{\textrm}{m}$ wavelength region. Absorption coefficients were observed to decrease with Te addition, indicating the improved transmission capabilities of Ge-Se-Te glasses as compared to binary Ge-Se glasses. XRD analysis of crystallized glasses suggested the formation of weaker Se-Te and/or Te-Te bonds with addition of Te substituting for Se in stronger Se-Se bonds. Incorporation of Te in excess of 20at% resulted in the formation of hexagonal Te phases when crystallized. It is speculated that the presence of Te-Te bonds with highly metallic bond character resulted in the enhanced crystallization tendencies of glasses. Fromation of Te-rich chains through gradual replacement of Se-Se with Se-Te and/or Te-Te bonds was further supported by decreases in glass transition and crystallization temperatures.

• 복식
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• 제55권3호
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• pp.1-18
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• 2005

In this study, the transition characteristics of purple series color names appearing in the clothing of the Joseon Dynasty were examined, and the associational meaning of each name were investigated through various methods. The results are as follows; First, Such characteristics as continuity, differentiation, substitution could be observed through the investigation of color names of purple-series appeared on the clothing in the Joseon Dynasty period. Secondly, the associational meaning could be subdivided into; social position symbolic meanings, usage meanings, economic meanings, and thought meanings. The social position symbolic meanings could be observed mainly in the single names which has been used since the ancient times, usage meanings could be observed in a wide variety according to the individual color names. The economic meanings could be observed by comparing the value of colored cloths and colored threads. The thought meanings were mainly related with the Confucianism. Thirdly, the associational semantic structure were established on the basis of associational meanings of purple-series color names. Individual color name on the social position symbolic semantic structure symbolizes [government official] and [servant]. Through usage semantic structure individual color names could be understood structurally according to the social position, sex distinction, wearing situation, items of clothing, and structure of clothing. Individual names on the economic semantic structure were segmented by the semantic components of the values in [high], [medium], [low] prices, kinds and quantity of dyes. The thought semantic structure could be subdivided [Confucianism] and [The Thought of Taeil] in its semantic structure.

• Asian Pacific Journal of Cancer Prevention
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• 제13권6호
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• pp.2949-2953
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• 2012

The glutathione S transferase (GST) family is a major part of cellular defense mechanisms against endogenous and exogenous substances, many of which have carcinogenic potential. Alteration in the expression level or structure of the glutathione-S-transferase (GST) enzymes may lead to inadequate detoxification of potential carcinogens and consequently contribute to cancer development. A member of the glutathione-S-transferase (GST) family, GSTP1, is an attractive candidate for involvement in susceptibility to carcinogen-associated colorectal cancer. An $Ag{\rightarrow}G$ transition in exon 5 resulting in an Ile105Val amino acid substitution has been identified which alters catalytic efficiency. The present study investigated the possible impact of Ile105Val GSTP1 polymorphism on susceptibility to colorectal cancer. in Jordan We examined 90 tissue samples previously diagnosed with colorectal carcinoma, and 56 non-cancerous colon tissues. DNA was extracted from paraffin embedded tissues and the status of the GSTP1 polymorphism was determined using a polymerase chain reaction restriction fragment length polymorphism (RFLP) method. No statistically significant differences were found between colorectal cancer cases and controls for the GSTP1 Ile/Ile, Ile/Val and Val/Val genotypes. The glutathione S-transferase polymorphism was not associated with risk in colorectal cancer cases in Jordan stratified by age, sex, site, grade or tumor stage. In conclusion, the GSTP1 Ile105Val polymorphism is unlikely to affect the risk of colorectal cancer.