• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1463-1469
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• 2009

Eleven novel oxiranyl and thiiranyl phenolic compounds were synthesized as potential antitumor agents using epichlorohydrin and epithiohydrin in the presence of $K_2CO_3$. Cytotoxicities were found in range of I$C_{50}$ values of 2.5-14.8 $\mu$M, which was partially attributed to topoisomerase II inhibition. Bis-thiiranyl anthraquinone analog, 19 showed more cytotoxicity against MDA-MB-231 (breast cancer cell) and PC3 (prostate cancer cell) after 24 and/or 48 h and more potent topoisomerase II inhibitory activity than etoposide.

• 한국동물학회지
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• 제22권2호
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• pp.81-93
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• 1979

Progesterone은 배양중인 생쥐 초기배아의 난할을 억제하는 효과를 나타내고 있는데 이의 기작을 밝히기 위하여 이 호르몬이 배아 세포들의 각종 대사작용에 미치는 영향을 조사하여 다음과 같은 결과를 얻었다. 1. Progesterone은 배아의 아미노산 흡수능 (uptake)을 증가시키었으나 동화능 (incorporation)을 연저히 감소시켰다. 2. Progesterone은 핵산 전구물질들 (uridine과 thymidine)의 흡수능과 동화능을 모두 저하시켰다. 본 실험의 결과로 미루어 Progesterone은 배아 세포들의 단백질, RNA 그리고 DNA 등의 고분자화합물의 합성을 저해하여 배아의 난할을 억제하는 것으로 보이며 배아 세포들의 투과성의 변화와는 직접 관련이 없는 것으로 사료된다.

• 전기전자학회논문지
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• 제21권3호
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• pp.252-255
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• 2017

고온자전합성과 후열처리 공정으로 $Mo_xW_{1-x}Si_2$ 발열체를 제조하였다. $Mo_xW_{1-x}Si_2$ 발열체의 신뢰성을 검증하기 위해 가속수명시험을 수행하였으며, 수명시간을 Minitab 프로그램으로 추정하였다. 또한, 가속수명시험 후의 $Mo_xW_{1-x}Si_2$ 발열체의 고장분석을 전기적과 구조적 특성으로부터 수행하였다. 그 결과, $Mo_xW_{1-x}Si_2$ 발열체의 지배적인 고장 유형은 발열체 내부의 크랙 형성과 $SiO_2$ 보호층의 박리임을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제28권6호
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• pp.947-952
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• 2007

Mycobacterium tuberculosis is a pathogen responsible for 2-3 million deaths every year worldwide. The emergence of drug-resistant and multidrug-resistant tuberculosis has increased the need to identify new antituberculosis targets. Acetohydroxy acid synthase, (AHAS, EC 2.2.1.6), an enzyme involved in branched-chain amino acid synthesis, has recently been identified as a potential anti-tuberculosis target. To assist in the search for new inhibitors and “receptor-based” design of effective inhibitors of tubercular AHAS (TbAHAS), we constructed four different structural models of TbAHAS and used one of the models as a target for virtual screening of potential inhibitors. The quality of each model was assessed stereochemically by PROCHECK and found to be reliable. Up to 89% of the amino acid residues in the structural models were located in the most favored regions of the Ramachandran plot, which indicates that the conformation of each residue in the models is good. In the models, residues at the herbicide-binding site were highly conserved across 39 AHAS sequences. The binding mode of TbAHAS with a sulfonylurea herbicide was characterized by 32 hydrophobic interactions, the majority of which were contributed by residue Trp516. The model based on the highest resolution X-ray structure of yeast AHAS was used as the target for virtual screening of a chemical database containing 8300 molecules with a heterocyclic ring. We developed a short list of molecules that were predicted to bind with high scores to TbAHAS in a conformation similar to that of sulfonylurea derivatives. Five sulfonylurea herbicides that were calculated to efficiently bind TbAHAS were experimentally verified and found to inhibit enzyme activity at micromolar concentrations. The data suggest that this time-saving and costeffective computational approach can be used to discover new TbAHAS inhibitors. The list of chemicals studied in this work is supplied to facilitate independent experimental verification of the computational approach.

• Structural Engineering and Mechanics
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• 제36권5호
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• pp.643-667
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• 2010

The classical flexibility difference method detects damage by observing the difference of conventional deflection flexibility matrices between pre- and post-damaged states of a structure. This method is not able to identify multiple damage scenarios, and its criteria to identify damage depend upon the boundary conditions of structures. The key point behind the inability and dependence is revealed in this study. A more feasible flexibility for damage detection, the Angle-between-String-and-Horizon (ASH) flexibility, is proposed. The physical meaning of the new flexibility is given, and synthesis of the new flexibility matrix by modal frequencies and translational mode shapes is formulated. The damage indicators are extracted from the difference of ASH flexibility matrices between the pre- and post-damaged structures. One feature of the ASH flexibility is that the components in the ASH flexibility matrix are associated with elements instead of Nodes or DOFs. Therefore, the damage indicators based on the ASH flexibility are mapped to structural elements directly, and thus they can pinpoint the damaged elements, which is appealing to damage detection for complex structures. In addition, the change in the ASH flexibility caused by damage is not affected by boundary conditions, which simplifies the criteria to identify damage. Moreover, the proposed method can determine relatively the damage severity. Because the proposed damage indicator of an element mainly reflects the deflection change within the element itself, which significantly reduces the influence of the damage in one element on the damage indicators of other damaged elements, the proposed method can identify multiple damage locations. The viability of the proposed approach has been demonstrated by numerical examples and experimental tests on a cantilever beam and a simply supported beam.

• Nuclear Engineering and Technology
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• 제25권1호
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• pp.148-153
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• 1993

노내계측기 신호로부터 노심평균 축방향 출력분포를 얻기위해 5차의 Fourier series 합성법이 노심감시계통 (COLSS)에 이용되고 있다. 이 방법은 단순하고 계산이 빠르기 때문에 실시간 계산에 이용된다. 이러한 합성법은 Fourier series 차수 및 축방향 경계조건에 따라 정확도가 달라진다. 노심감시계통에서는 현재 축방향으로 5개의 고정 노내계측기를 이용하고 있으므로 5차의 Fourier series 합성법을 적용하고 있다. 따라서 축방향 경계조건은 노심감시계통의 계산결과에 미치는 영향을 평가하여 적절히 결정되어야 한다. 본 논문에서는 영광 3,4호기를 대상으로 4가지의 축방향 경계조건 (axial buckling=0.75, 0.8, 0.9와 1.0)을 살펴보았다. 최적의 축방향 경계조건을 결정하기 위해 노심평균 축방향 출력분포와 운전여유도를 각 경우에 대해 비교하였다. 비교결과 최적의 축방향 경계조건은 axial buckling이 0.9인 것을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제15권11호
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• pp.990-996
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• 1994

New ferrocene-based chelate amines, $Fe[C_5H_4CH(Me)NMe_2]_2\;(3), \;Fe[C_5H-3(CH(Me)NMe_2)(PPh_2)-1,2]_2\;(4),\;(C_5H_5)Fe(C_5H_3(CH_2NMe_2)(CH(CN)NMe_2-1,2)\;(6),\;and\;(C_5H_5)Fe(C_5H_3(CH_2NMe_2)(CH(Me)NMe_2-1,2)$ (7) have been prepared. The reaction and the coordination chemistry of 4 and other related compounds (S,R)-(1-N,N-dimethylaminoethyl)-2-dicyclohexylphosphino)ferrocene (CPFA) and 1,1'-bis-(diphenylphosphino)ferrocene (BPPF) with $Rh_2(OAc)_4(MeOH)_2$ were investigated. The reaction of the chiral ligand (S,R)-CPFA forms a complex of the type (${\eta}^1$-(S,R)-CPFA-P)$_2Rh_2(OAc)_4$ (8) in which the ligand is coordinated to both rhodium centers in a monodentate fashion through phosphorus. In contrast, the bisphosphine analogues such as BPPF and 4 afford chelate complexes of the type (${\eta}^2-PP)Rh_2(OAc)_4$ (9 & 10) where both ligands act as a chelate bidentate to a single rhodium atom. All these complexes were characterized by microanalytical and spectroscopic techniques. In one case, the structure of 8 was determined by X-ray crystallography. Crystals are monoclinic, space group C2 (No. 5), with a=26.389 (3), b=12.942 (1), c=11.825 (1) A, ${\beta}$=111.22(1)$^{\circ}$, V=3964.7 (8) $A^3$, Z=4, and $D_{calc}$=1.58 g $cm^{-3}$. Two Rh(II) centers are bridged by four $AcO^-$ groups in the ${\eta}^1$ : ${\eta}^1$ mode across a Rh-Rh single bond, and octahedral coordination at Rh(1) and Rh(1') is completed by axially coordinating (S,R)-CPFA and a briding $AcO^-$, respectively.

• 한국전산구조공학회논문집
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• 제35권3호
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• pp.175-182
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• 2022

부분구조화 기법은 자유도가 많고 복잡한 구조물의 유한요소 해석 모델 단순화에 효율적으로 적용될 수 있는 기법이다. 대표적으로 선형 문제에 대해서는 Craig-Bampton method 등이 있다. Craig-Bampton method는 경계 요소를 제외한 나머지 요소의 불필요한 자유도를 제거함으로써 선형 구조물의 축소를 수행한다. 최근에는 부분구조화 기법과 더불어 구조물의 최적설계를 위해 멀티레벨 최적화 기법이 많이 활용되고 있다. 시스템의 목표를 달성하기 위해 각 부구조에 새로운 목표를 할당하는 기법이다. 본 연구에서는 유전자 알고리즘을 이용하여 시스템 목표 달성을 위한 각 부구조별 내부 자유도 개수를 새로운 목표로 할당하고 최적화를 수행하였다. 최적화 절차로부터 도출된 부구조별 내부 자유도 개수를 이용하여 시스템의 축소를 수행하였다. 다양한 수치예제들을 통해 축소 모델에 대한 결과를 확인하였으며, 90% 이상의 정확도를 가지는 것을 확인하였다.

• Journal of Ginseng Research
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• 제47권3호
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• pp.385-389
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• 2023

Background: Ginseng has been used as a traditional medicine for treatment of many diseases and for general health maintenance. Previously, we showed that ginseng did not demonstrate estrogenic property in ovariectomized mouse model. However, it is still possible that disruption of steroidogenesis leading to indirect hormonal activity. Methods: The hormonal activities were examined in compliance with OECD guidelines for detecting endocrine disrupting chemicals: test guideline (TG) No. 456 (an in vitro assay method for detecting steroidogenesis property) and TG No. 440 (an in vivo short-term screening method for chemicals with uterotrophic property). Results: Korean Red Ginseng (KRG) and ginsenosides Rb1, Rg1, and Rg3 did not interfere with estrogen and testosterone hormone synthesis as examined in H295 cells according to TG 456. KRG treatment to ovariectomized mice did not show a significant change in uterine weight. In addition, serum estrogen and testosterone levels were not change by KRG intake. Conclusion: These results clearly demonstrate that there is no steroidogenic activity associated with KRG and no disruption of the hypothalamic-pituitary-gonadal axis by KRG. Additional tests will be performed in pursuit of cellular molecular targets of ginseng to manifest mode of action.

• 분석과학
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• 제21권5호
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• pp.403-411
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• 2008

방사성 액체폐기물의 용매추출 공정에서 발생되는 방사선 분해현상을 연구하기 위하여 추출제로 사용되는 dimethyldibutyltetradecylmalonamide (DMDBTDMA)를 합성하고, 합성된 DMDBTDMA를 $^{60}Co$ 감마 방사선으로 조사시킬 때 생성되는 방사선 분해산물을 정량 분석하였다. 방사선 조사된 DMDBTDMA에 대한 FT-IR 스펙트럼과 EI-질량스텍트럼 및 GC/MS-SIM 방법으로 측정한 결과를 바탕으로 n-methylbutylamine, tetradecane, 1-tetradecanol 3종의 방사선 분해산물의 존재를 확인하였다. 3종의 방사선 분해산물 농도는 이들 표준물질과 n-dodecane을 내부표준물질(ISTD)로 사용하여 GC/MS-SIM 방법으로 정량 분석하였다. 방사선 분해산물에 대한 총 이온 크로마토그램에서 나타난 머무름 거동, 분리도와 해상도 측면에서 만족스런 결과를 얻었으며, 총 이온 크로마토그램에서 n-methylbutylamine, n-dodecane, tetradecane 및 1-tetradecanol 각각의 성분에 대한 피크 검출시간은 각각 2.35분, 8.83분, 10.68분 및 12.75분 이었다. 그리고 tetradecane은 방사선 분해산물의 농도가 DMDBTDMA의 방사선 흡수선량과 비례하는 상관관계를 확인하였다.