• Restorative Dentistry and Endodontics
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• 제22권2호
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• pp.739-750
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• 1997

Treatment of root perforation elicits special considerations due to its blood-contaminated circumstances. It is known that conventional dental restorative materials are all leaking. Calcium sulfate is the material which react with water to become chemically set. This study, therefore, was performed to develop a new compound containing calcium sulfate and to evaluate its physical and biological characteristics. Three materials were used, IRM, calcium sulfate, calcium sulfate-hydroxyapatite compound. The composition of the calcium sulfate-hydroxyapatite compound was basically 50 % of calcium sulfate and 50 % of hydroxyapatite mixed with guajacol. The materials were mixed in conventional way and underwent four physical test procedures, setting time, solubility test, compressive strength, and marginal leakage test. All materials were evaluated under the scanning electron microscope to examine the marginal sealing ability. Animal experiment was also performed to test the materials' tissue response. Twenty-four dog's premolars were tested with either furcation perforations or apical retro-fillings. From the results, we found that calcium sulfate possess the good marginal sealing ability. However, calcium sulfate creates many voids which is caused by crystal thrusting action when it reacts with water. It seemed that the voids caused disintegration of the material which eventually lead to tissue reaction. By compounding calcium sulfate and hydroxyapatite, we were able to obtain the better physical properties but it showed larger marginal gap between the material and the root surface. Within the six weeks observation period, both IRM and calcium sulfate-hydroxyapatite compound showed good tissue responses in animal experiment. It is concluded that calcium sulfate would be the material of choice in root perforation repair, but the physical property needs to be further improved.

• 대한화학회지
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• 제6권2호
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• pp.133-142
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• 1962

This study was carried out to investigate the lead-bismuth-sodium ternary system which a basis of the Dittmer method as a part of "the fundamental study of pyrometallurgical debismuthizing of lead". Thermodynamic properties of each liquid Pb-Bi, Pb-Na binaries as well as liquid Pb-Bi-Na ternary solution were measured by e.m.f. of these concentration cells, and those of each component were also determined. Furthermore, iso-activity lines including Pb rich side composition of Pb-Bi-Na ternary solution were determined. The relationship between those thermodynamic characteristics and tendency of intermetallic compound formation was discussed through the above experiments.

• Advances in materials Research
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• 제2권3호
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• pp.173-180
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• 2013

Lead-free complex perovskite ceramics $NaMeO_3$ ($Me{\equiv}Nb$, Ta) were synthesized using conventional solid state reaction technique and characterized by structural, FTIR and electrical (dielectric and ac conductivity) studies. The crystal symmetry, space group and unit cell dimensions were determined from the experimental results using FullProf software. XRD analysis of the compound indicated the formation of single-phase orthorhombic structure with the space group Pmmm (47). Dielectric studies showed the diffuse phase transition at $394^{\circ}C$ for $NaNbO_3$ and $430^{\circ}C$ for $NaTaO_3$. Ac conductivity in both the compounds follows Jonscher's power law.

• 한국식품영양과학회지
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• 제28권4호
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• pp.816-821
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• 1999

Cholesterol esterase(pCEH, pancreas cholesterol ester hydrolase, E.C.3.1.1.13) which is secreted from pancreas has been known as an important lipase for cholesterol uptake. cholesteryl acyl esters from a diet must be hydrolyzed to free cholesterol and fatty acid by cholesterol esterase before the absorption in small intestine. For the development of inhibitory substances from natural source, we screened many extracts of oriental herbs for the inhibition of cholesterol esterase in vitro. The ethanol extract of Ephedra herba showed strong inhibitory activity. Solvent fractionation and silica gel column chromatography with the extract lead to the purification of the inhibitory principle in Ephedra herba. Crystallized inhibitor was identified as ( ) ephedrine by using UV, FT IR, 1H NMR, 13C NMR and GC/Mass. These results suggest that ( ) ephedrine can be used as a potential lead compound for the development of inhibitor for cholesterol uptake by cholesterol esterase inhibition.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1642-1651
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• 2021

In this study, isophtalic neopentyl glycol polyester (NPG-PES) based composites with different loading ratios of pure tungsten metal (W), tungsten (VI) oxide (WO₃), tungsten boron (WB) and tungsten carbide (WC) composites were prepared as alternative shielding materials for ionizing electromagnetic radiation (IEMR) shielding. Structural characterizations of the composites were done. Gamma spectrometric analysis of composites for 80-2000 keV energy range was performed and their usability as IEMR shielding was discussed. As a result, the produced composites showed a shielding performance of 60-100% of the lead (the most widely used IEMR shielding material) depending on the reinforcement material, reinforcement loading rate and experimental conditions. Thus, it was reported that produced composites could be an alternative to lead shieldings that have several disadvantages as toxic properties, difficulty of processing and inelasticity.

• Journal of Welding and Joining
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• 제18권3호
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• pp.89-96
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• 2000

As solder becomes small and fine, the reliability and solderability of solder joint are the critical issue in present electronic packaging industry. Besides the use of lead(Pb) containing solders for the interconnections of microelectronic subsystem assembly and packaging has enviromental problem. In this study, using Sn/Pb and Sn/Ag eutectic solder paste, in order to obtain decrease of solder joint strength with increasing aging time, initial solder joint strength and aging strength after 1000 hour aging at $100^{\circ}C$ were measured by peel test. And in order to obtain the growth of intermetallic compound(IMC) layer thickness, IMC layer thickness was measured by scanning electron microscope(SEM). As a result, solder joint strength was decreased with increasing aging time. The mean IMC layer thickness was increased linearly with the square root of aging time. The diffusion coefficient(D) of IMC layer was found to $1.29{\times}10^{-13}{\;}cm^2/s$ at using Sn/Pb solder paste, 7.56{\times}10^{-14}{\textrm}{cm}^2/s$ at using Sn/Ag solder paste.

• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.561-566
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• 2007

Adenosine kinase (AK) is a ubiquitous intracellular enzyme, which catalyzes the phosphorylation of adenosine (ADO) to adenosine monophosphate (AMP). AK inhibitors have therapeutic potential as analgesic and antiinflammatory agents. A chemical feature based pharmacophore model has been generated from known AK inhibitors (26 training set compounds) by HypoGen module implemented in CATALYST software. The top ranked hypothesis (Hypo1) contained four features of two hydrogen-bond acceptors (HBA) and two hydrophobic aromatics (Z). Hypo1 was validated by 124 test set molecules with a correlation coefficient of 0.905 between experimental and estimated activity. It was also validated by CatScramble method. Thus, the Hypo1 was exploited for searching new lead compounds over 238,819 chemical compounds in NCI database and then the selected compounds were screened based on restriction estimated activity and Lipinski's rules to evaluate their drug-like properties. Finally we could obtain 72 new lead candidates and the two best compound structures from them were posted.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1994년도 춘계학술대회 and 제3회 신약개발 연구발표회
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• pp.324-324
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• 1994

5, 8-Quinolinedione모핵은 항진균, 항균, 항암제등의 pharmacophore 이다. 그리고 신약 창제의 lead compound로 생체내 전자전달계에 작용하여 환원을 받으면 quinone semiradical과 superoxide를 생성하여 진균, 세균등을 공격하여 항진균, 항균작용이 예상된다. 새로운 항진균제를 개발하기 위해 6-chloro-7-(halo-phenyl)-5,8-quinolindione유도체 (RCK1-12)을 합성하여 이들 화합물에 대하여 항균작용 및 항진균작용을 검색했다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(3)
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• pp.305-310
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• 1996

This paper concerns the cladding residual stresses in a reactor vessel induced during cooling from the manufacturing temperature down to room temperature Finite element results show that very large stress gradients are present at the interface corner and such stress singularity might lead to local yielding or cladding-base metal debonding.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1993년도 제2회 신약개발 연구발표회 초록집
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• pp.43-43
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• 1993

Robinson annotation과 입체선택적 alkylation으로 새로운 pimarane diterpene 의 A,B-ring system을 합성한 후 cyclohexane의 allylation과 Claisen 전위를 이용하여 4급탄소 unit를 얻고 Mcurry coupling 반응으로 C-ring을 도입함으로써 새로운 pimarane diterpene을 전합성하였다. 전합성 중에 개발된 방법들을 이용하여 기본 골격들을 합성한 후 효능 검색하여 구조-활성관계를 확립하고 lead compound를 유도해 내었다.