• Title/Summary/Keyword: asymmetric resolution

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Calculating Sea Surface Wind by Considering Asymmetric Typhoon Wind Field (비대칭형 태풍 특성을 고려한 해상풍 산정)

  • Hye-In Kim;Wan-Hee Cho;Jong-Yoon Mun
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.29 no.7
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    • pp.770-778
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    • 2023
  • Sea surface wind is an important variable for elucidating the atmospheric-ocean interactions and predicting the dangerous weather conditions caused by oceans. Accurate sea surface wind data are required for making correct predictions; however, there are limited observational datasets for oceans. Therefore, this study aimed to obtain long-period high-resolution sea surface wind data. First, the ERA5 reanalysis wind field, which can be used for a long period at a high resolution, was regridded and synthesized using the asymmetric typhoon wind field calculated via the Generalized Asymmetric Holland Model of the numerical model named ADvanced CIRCulation model. The accuracy of the asymmetric typhoon synthesized wind field was evaluated using data obtained from Korea Meteorological Administration and Japan Meteorological Administration. As a result of the evaluation, it was found that the asymmetric typhoon synthetic wind field reproduce observations relatively well, compared with ERA5 reanalysis wind field and symmetric typhoon synthetic wind field calculated by the Holland model. The sea surface wind data produced in this study are expected to be useful for obtaining storm surge data and conducting frequency analysis of storm surges and sea surface winds in the future.

Synthesis of Optically pure Epichlorohydrine using Dimeric Chiral Salen Catalyst Containing BF3 (BF3 함유 이분자형 키랄 살렌 촉매에 의한 고광학순도의 에피클로로히드린 합성)

  • Lee, Kwang-Yeon;Rahul, B. Kawthekar;Kim, Geon-Joong
    • Applied Chemistry for Engineering
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    • v.18 no.4
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    • pp.330-336
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    • 2007
  • In this study, new dinuclear chiral Co (salen) complexes bearing $BF_3$ have been synthesized and their properties as the asymmetric catalyst have been examined. The NMR, UV and ESCA analyses were performed to determine the structure of synthesized catalysts. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides by hydrolytic kinetic resolution technology. The easily prepared dimeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (> 99 %ee). The dimeric structured chiral salen showed remakablely enhanced reactivity and may be employed substantially lower loadings than its monomeric analogues, and in addition no racemization happened during the separation of product epoxides. The system described in this work is very efficient for the sinthesis of chiral epoxide and 1,2-diol intermediates.

Hydrolytic Kinetic Resolution of Racemic Alkyl-glycidyl Derivatives by using Dimeric Chiral Salen Catalyst Containing Ga, In and TlCl3 (염화갈륨, 인듐 및 탈륨 함유 이분자형 키랄 살렌 촉매에 의한 라세믹 알킬 글리시딜레이트 유도체의 비대칭 가수분해반응)

  • Shin, Chang-Kyo;Rahul, B. Kawthekar;Kim, Geon-Joong
    • Applied Chemistry for Engineering
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    • v.18 no.3
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    • pp.218-226
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    • 2007
  • The stereoselective synthesis of chiral terminal epoxides is of immense academic and industrial interest due to their utility as versatile starting materials as well as chiral intermediates. In this study, new dinuclear chiral Co (salen) complexes bearing gallium-, indium- and tallium-chloride have been synthesized and characterized. The mass and EXAFS spectra provided the direct evidence of formation of dinuclear complex. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides having ether or ester groups by hydrolytic kinetic resolution technology. The easily prepared dimeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (> 99% ee). The dimeric structured chiral salen showed remarkably enhanced reactivity and may be employed substantially lower loadings than its monomeric analogues. The system described in this work is very efficient for the synthesis of chiral epoxide and 1,2-diol intermediates

Enantioselective Epoxide Synthesis on the Chiral Salen Catalyst having a Transitional Metal Salt (전이금속염 함유 키랄 살렌 촉매에 의한 광학선택적 에폭사이드의 합성)

  • Guo, Xiao-Feng;Kawthekar, Rahul B.;Kim, Geon-Joong
    • Korean Chemical Engineering Research
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    • v.46 no.4
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    • pp.769-776
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    • 2008
  • The stereoselective synthesis of chiral terminal epoxide is of immense interest due to their utility as versatile starting materials as well as chiral intermediates. In this study, new chiral Co(salen) complexes bearing cobalt(II) chloride, iron(III) chloride and zinc(II) nitrate have been synthesized and characterized. The mass and EXAFS spectra provided the direct evidence of formation of complex. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of terminal epoxides such as styrene oxide and phenylglycidylether by hydrolytic kinetic resolution technology and for the synthesis of glycidyl buthylate. The easily prepared complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (>99% ee). The newly synthesized chiral salen showed remakablely enhanced reactivity with substantially low loadings. The system described in this work is very efficient for the sinthesis of chiral epoxide and 1,2-diol intermediates.

Advanced Cryo-Electron Microscopy Technology: High Resolution Structure of Macromolecules

  • Chung, Jeong Min;Jung, Hyun Suk
    • Applied Microscopy
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    • v.46 no.1
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    • pp.1-5
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    • 2016
  • Recent cryo-electron microscopy (EM) studies reported the structure of various types of proteins at high resolution which is sufficient to visualize the intermolecular interaction at near atomic level. There are two main factors that cause the advances in cryo-EM; the development of image processing techniques, such as single particle analysis, and the improved electron detection devices. Although the atomic structures of small and asymmetric proteins are not yet to be determined by cryo-EM, this striking improvement implies the bright prospect of the application in biomedical studies. This study reviews the recently published studies reported high resolution structures using improved imaging analysis techniques and electron detectors. Furthermore, we will discuss about the future aspects of cryo-EM application.