• 제목/요약/키워드: Lewis

검색결과 617건 처리시간 0.022초

전이금속촉매를 사용한 DFP 분해 성능 연구 (Decomposition Studies of DFP Using Transition Metal Catalysts)

  • 계영식;정근홍;정우영
    • 공업화학
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    • 제21권1호
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    • pp.1-5
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    • 2010
  • Cu(II)와 diamine, aminothiol 그리고 dithiol과의 착물을 합성하여, 동일한 조건 하에서 DFP 분해반응성을 평가하였다. 실험결과 Lewis basicity가 높은 유기물질일수록 DFP의 분해반응을 촉진시키는 것으로 나타났다. N donor인 diamine에 비해 전자를 더 잘 제공하는 S donor를 가진 aminothiol과 결합된 Cu(II) 착물이 DFP의 가수분해 반응에 약 3배 정도 효과적인 것으로 분석되었다. Lewis basicity가 더 높은 dithiol 리간드를 사용한 경우 Cu(II)(1,2-ethane dithiol)$(NO_3)_2$의 난용성으로 인해 heterogeneous 조건하에서 반응속도를 측정하였음에도 homogeneous 조건하에서 측정한 Cu(II) (ethylenediamine)$(NO_3)_2$ 반응보다 약 1.6배 효과적이었다. DFP 분해에 대한 제올라이트의 반응성 평가에서 NaY의 경우 DFP 가수분해 반응을 촉진시키지 못하였으며, RuNaY는 DFP분해 반응이 Cu(II)-organic complex의 반응성에 비해서는 효과가 떨어지는 것으로 관찰되었다.

Fluorescence Molecular Imaging

  • Choi, Heung-Kook;Ntziachristos, Vasilis;Weissleder, Ralph
    • 대한자기공명의과학회:학술대회논문집
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    • 대한자기공명의과학회 2004년도 제9차 학술대회 초록집
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    • pp.23-32
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    • 2004
  • The chemotherapy sensitive Lewis lung carcinoma (LLC) and chemotherapy resistant Lewis lung carcinoma (CR-LLC) tumors concurrently implanted in mice, and compare these findings with histological macroscopic observations against 3D reconstruction of Fluorescence Molecular Tomography (FMT) preformed in vivo on the same animals. For the 3D image reconstruction we used 32 laser source images, a flat image and 3D surface rendering that confused for 3D Fluorescence Molecular Imaging (FMI). A minimum of ten tissue sections were analyzed per tumor for quantification of the TUNEL-positive cells, cell-associated Cy5.5-Annexin and vessel-associated Alexa Fluor-Lectin. These are useful apoptosis and angiogenesis markers, and they serve as validation experiments to data obtained in vivousing a Cy5.5-Annexin V conjugate injected intravenously in chemotherapy-treated animals carrying the tumors studied histologically. We detected higher levels of apoptosis and corresponding higher levels of Cy5.5 fluorescence in the LLC vs. the CR-LLC tumors according to tissue depth and these findings confirm that in vivo staining with the Cy5.5-Annexing conjugate correlates well with in vitro TUNEL staining and is consistent with the higher apoptotic index expected from the LLC line. There appeared to be 1.38% more apoptosis for LLC than CR-LLC. Consequently there is good correlation between the histology results and in vivo fluorescence-mediated optical imaging. In conclusion the apoptotic images of 3D FMI were validated by microscopic histological image analysis. This is a significant result for the continuous progress of fluorescence 3D imaging research.

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질소 희석된 프로판 자유제트 층류부상화염에 있어서 화염 자기진동 특성에 관한 연구 (Study of Characteristics of Self-Excitation in Lifted Laminar Free-Jet Propane Flames Diluted with Nitrogen)

  • 윤성환;박정;권오붕;배대석
    • 대한기계학회논문집B
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    • 제34권4호
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    • pp.399-408
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    • 2010
  • 질소 희석된 프로판 층류 부상 화염에서 화염진동 불안정성과 화염 곡률 효과를 살펴보기 위하여 실험적 연구를 수행하였다. 화염 진동은 총 3가지 영역으로 열손실에 의한 진동, 열손실 및 부력이 혼재된 진동, 그리고 열손실 및 루이스 수에 의한 영향이 혼재된 진동으로 구분되었다. 순수 열손실에 의한 진동은 루이스 수에 의한 진동과 부력에 의한 수력학적 불안정성과 관련이 없으며 연료 루이스 수에 관계없이 모든 부상화염 조건에서 관찰되었다. 화염의 시간에 따른 부상높이 변화에 대한 FFT분석을 통해 화염진동 불안정성의 실험적 증거와 특성을 명확히 제시하였고, 부상 화염의 열손실에 의한 자기진동의 메커니즘에 대한 시나리오를 논의한다.

루이스 멈퍼드의 건축비평에서 미적 상징의 문제 (Aesthetic Symbolism in Lewis Mumford's Architectural Criticism)

  • 서정일
    • 건축역사연구
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    • 제26권1호
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    • pp.7-16
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    • 2017
  • One of the essential characteristics of Lewis Mumford's architectural criticism is the coherent emphasis on symbolism. Such emphasis stems from his understanding of city and humanity in the context of civilization: first, that the architecture symbolizes institutions of urban civilization; second, that the technical aspect of human nature should be balanced with its artistic aspects. Mumford believed that each architectural type requires an appropriate symbolic expression corresponding to its purpose and that a new symbolic expression, in a new cultural context, should replace the conventional expression. He took symbolism for an intuitional expression, and read multi-layered meanings of architecture: 'practical function' by way of rational reason and 'symbolic function' by way of intuition. He pursued a balance between practicality and beauty to rectify the situation of modern civilization, in which symbolism, the expression of its intuitional aspect, is in crisis. Ultimately, for Mumford, the essential task of architectural critic is of the interpretation of symbolism, aiming at the correspondence and communication between the architect(artist)'s intuition and critic(interpreter)'s via the media of symbol. The critic can play some privileged role of interpreting even symbols unintended by the architect. The ideal architectural critic, after all, would be the one who is able to understand the city, technology and human beings in the perspective of civilization and to interpret the architect's artistic expression in its highest form through intuition. Mumford established himself as such a critic and evaluated the status of aesthetic accomplishment of his contemporary architecture and technological civilization, giving emphasis on the artistic practice in architecture as a solution.

영문학을 활용한 의상디자인 전공을 위한 영어교육: Alice's Adventures in Wonderland by Lewis Carroll 을 활용한 학습 모형 (Literature-Based Instruction for Fashion Design Class: Using Alice's Adventures in Wonderland by Lewis Carroll)

  • 김민정
    • 한국의류산업학회지
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    • 제20권3호
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    • pp.287-292
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    • 2018
  • The present study proposes a model for literature-based instruction within the context of a fashion design curriculum at a Korean university. The fashion design market continues to grow. The fashion design market now requires more cultural-bound strategies and efficient communication skills. The literature provides authentic resources and is highly relevant to the development of students' culture awareness as well as language awareness. Alice's Adventures in Wonderland written by Lewis Carroll contains various cultural contexts of the Victorian Era. The text provides explicit knowledge of the era depicted in both illustrations and satire languages. This study instructs students to analyze and interpret texts and illustrations so that they can engage critically and analytically in reading text to increase culture awareness and language awareness. The integration of literature and fashion design can provide students an opportunity to explore language choice and acquire refined knowledge of the target culture. Along with the text, illustrations in the literature provoke student's imaginative and creative thinking skills. Students can think and discuss many issues that deal with Victorian values and reinforce creative thinking skills. In the final stage, students can design fashion inspired by Victorian values and present their own designs using the acquired languages. This eventually leads students to adapt to a new notion for the fashion market and become competent communicators in the fashion world.

Ethyl Acetate Fraction of Adenophora triphylla var. japonica Inhibits Migration of Lewis Lung Carcinoma Cells by Suppressing Macrophage Polarization toward an M2 Phenotype

  • Park, Shin-Hyung
    • 대한약침학회지
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    • 제22권4호
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    • pp.253-259
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    • 2019
  • Objectives: It is reported that tumor-associated macrophages (TAMs) contribute to cancer progression by promoting tumor growth and metastasis. The purpose of this study is to investigate the effect of different fractions of Adenophora triphylla var. japonica (AT) on the polarization of macrophages into the M2 phenotype, a major phenotype of TAMs. Methods: We isolated hexane, ethyl acetate, and butanol fractions from crude ethanol extract of AT. The cytotoxicity of AT in RAW264.7 cells was examined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RAW264.7 cells were polarized into the M2 phenotype by treatment with interleukin (IL)-4 and IL-13. The expression of M2 macrophage marker genes was detected by reverse transcription polymerase chain reaction (RT-PCR). The phosphorylation level of signal transducer and activator of transcription 6 (STAT6) was investigated by western blot analysis. The migration of Lewis lung carcinoma (LLC) cells was examined by transwell migration assay using conditioned media (CM) collected from RAW264.7 cells as a chemoattractant. Results: Among various fractions of AT, the ethyl acetate fraction of AT (EAT) showed the most significant suppressive effect on the mRNA expression of M2 macrophage markers, including arginase-1, interleukin (IL)-10 and mannose receptor C type 1 (MRC-1), up-regulated by treatment of IL-4 and IL-13. In addition, EAT suppressed the phosphorylation of STAT6, a critical regulator of IL-4 and IL-13-induced M2 macrophage polarization. Finally, the increased migration of Lewis lung carcinoma (LLC) cells by CM from M2-polarized RAW264.7 cells was reduced by CM from RAW264.7 cells co-treated with EAT and M2 polarization inducers. Conclusion: We demonstrated that EAT attenuated cancer cell migration through suppression of macrophage polarization toward the M2 phenotype. Additional preclinical or clinical researches are needed to evaluate its regulatory effects on macrophage polarization and anti-cancer activities.

상호작용하는 $H_2$-CO 예혼합 화염에서 $H_2$선호확산의 영향에 관한 수치적 연구 (Effects of Preferential Diffusion on Downstream Interaction in Premixed $H_2$/CO Syngas-air Flames)

  • 오상훈;박정;권오붕
    • 한국연소학회지
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    • 제17권3호
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    • pp.17-29
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    • 2012
  • The effects of strain rate and preferential diffusion of $H_2$ on flame extinction are numerically studied in interacting premixed syngas-air flames with fuel compositions of 50% $H_2$ + 50% CO and 30% $H_2$ + 70% CO. Flame stability diagrams mapping lower and upper limit fuel concentrations at flame extinction as a function of strain rate are examined. Increasing strain rate reduces the boundaries of both flammable lean and rich fuel concentrations and produces a flammable island and subsequently even a point, implying that there exists a limit strain rate over which interacting flame cannot be sustained anymore. Even if effective Lewis numbers are slightly larger than unity on extinction boundaries, the shape of the lean extinction boundary is slanted even at low strain rate, i.e. $a_g=30s^{-1}$ and is more slanted in further increase of strain rate, implying that flame interaction on lean extinction boundary is strong and thus hydrogen (as a deficient reactant) Lewis number much less than unity plays an important role of flame interaction. It is also shown that effects of preferential diffusion of $H_2$ cause flame interaction to be stronger on lean extinction boundaries and weaker on rich extinction boundaries. Detailed analyses are made through the comparison between flame structures with and without the restriction of the diffusivities of $H_2$ and H in symmetric and asymmetric fuel compositions. The reduction of flammable fuel compositions in increase of strain rate suggests that the mechanism of flame extinction is significant conductive heat loss from the stronger flame to ambience.

고체연료로켓에서 에지화염의 맥동 불안정성 (Oscillatory Instabilities of Edge Flames in Solid Rocket Combustion)

  • 김강태;박준성;박정;김정수;길상인;조한창
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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    • pp.275-278
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    • 2006
  • [ $CH_4-He/Air$ ] 대향류 확산화염의 저 화염 신장율에서 진동 불안정성에 관하여 실험적으로 연구하였다. 저 화염 신장율에서 진동 불안정은 Le가 1보다 클 때 소화한계 부근에서 발행하고 측면방향 열손실이 중요한 역할을 한다. 화염이 진동할 때 화염의 형태는 전진하거나 후퇴하는 edge flame이고 진동의 동적거동은 성장, 조화 그리고 감쇠 진동 모드 세 가지로 나타났다. 전체 화염 신장율이 감소하면 진동의 진폭은 커지게 되는데 이는 화염의 크기가 감소하게 되어 측면 열손실이 증가하였기 때문이다. 저 화염 신장율에서 edge flame의 진동 불안정성은 Le 뿐만 아니라 복사와 측면 열손실도 밀접한 관계가 있다.

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조건부 확률과 조건문의 확률 (Conditional Probabilities and Probabilities of Conditionals)

  • 최원배
    • 논리연구
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    • 제8권2호
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    • pp.59-84
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    • 2005
  • 조건문의 확률은 조건부 확률과 같을 수 없음을 보이는 루이스의 '사소함 결과'(the triviality results)는 널리 알려져 있다. 하지만 이 증명의 정확한 구조와 그 의미를 파악하기란 그다지 쉽지 않다. 이 논문에서는 먼저 루이스 증명의 한 형태가 제시되고 왜 조건문의 확률은 조건부 확률과 같을 수 없는지에 대해 한 가지 설명이 제공된다. 이와 아울러 이런 결과가 갖는 철학적 함축이 무엇인지가 논의된다. A일 경우 C일 조건부 확률은 A가 성립할 경우 C가 성립할 가능성이 어느 정도인지에 관한 것으로, 이 점은 조건부 확률의 정의인 등식 Pr(C|A)= Pr(A & C) / Pr(A)에 잘 반영되어 있다. 조건부 확률이 갖는 이런 독특한 성질과 조건부 확률과 언제나 같은 확률을 갖는 명제를 찾으려는 노력이 허사로 끝나게 마련이라는 점은 서로 밀접한 연관이 있어 보인다. 만약 이 점이 옳다면, 우리는 조건문은 그냥 주장과는 아주 다른 조건부 주장을 표현한다고 보아야 하며, 조건부 주장은 진리조건을 갖지 않는, 사이비 주장이라는 점을 받아들여야 할지도 모르겠다.

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