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A Theoretical Study of Some Bicyclic Azoalkanes
Gyusung Chung*,Duckhwan Lee 대한화학회 2006 Bulletin of the Korean Chemical Society Vol.27 No.12
The molecular structures of the ground and lowest triplet states of 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH), 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) and their fused ring derivatives are investigated with an ab initio method and the density functional theory. Unlike the singlet DBH and DBO, the azo skeletal structures of the triplet counterparts are turned out to be quite sensitive to the change of the electronic structure of the fused ring. The B3LYP C-N=N-C dihedral angles of the triplet DBH and DBO are estimated to be about 28.0 and 40.4o, respectively. The B3LYP singlet-triplet energy gaps for DBH and DBO are predicted to be 58.4 and 48.4 kcal/mol, respectively. The triplet state energy can be lowered drastically by the presence of the remote p-p interaction as in the case of 1bb'.
A Sensitivity Analysis for Three-Parameter Ellipsometry
Gyusung Chung,Duckhwan Lee,Woon-Kie Paik Korean Chemical Society 1991 Bulletin of the Korean Chemical Society Vol.12 No.5
In the three-parameter ellipsometry (TPE), also known as reflectance-ellipsometry, the ellipsometric measurements, ${\Psi} and {\Delta}$, are combined with the reflectometric measurement, R, to determine the optical parameters and the thickness of a light-absorbing thin film. The constant ${\Psi}, {\Delta}$ and R surfaces are analyzed graphically to understand the nature of the TPE solutions. A sensitivityanalysis is shown to be useful not only for identifying the film properties which affect most the TPE measurements, but also for estimating errors in film properties arising from the uncertainties in measurements.
Molecular Structures of 2,2-Bipyridine and Its Anion Radical: Multiconfiguration-SCF Calculations
Gyusung Chung,이덕환 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.12
The electronic structures and conformational behaviors of the neutral and anionic 2,2-bipyridine species are investigated with the muticonfiguration-SCF (MCSCF) method. The MCSCF calculations show that the lowest triplet states of neutral molecule and the doublet state of anionic species have the local minimum structures corresponding to the cis and trans forms. The MCQDPT2 calculation predicts that the lowest triplet state of the trans form lies 5.3 kcal/mol above the ground singlet state. The best level of theory predicts that the energy of the lowest doublet states of the anion trans and cis forms is 1.7 kcal/mol above the neutral singlet state.
권오현,Gyusung Chung 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.11
The electronic structure of bis-nitronyl nitroxide biradical has been investigated by using density functional theory (DFT) and ab initio multireference (MCSCF and MCQDPT2) methods. The broken-symmetry DFT approach has been applied to the open-shell singlet biradical at the BLYP, B3LYP, and BHandHLYP levels. DFT and MCSCF calculations show that the singlet biradical state is slightly more stable than the triplet state, which is refined at the MCQDPT2 level. The dependence of the singlet-triplet energy gap on the conformational change between two monoradicals is discussed. The results indicate that the choice of the theoretical model plays an important role in understanding the electronic nature of the organic biradicals.
Lee, Sunyoung,Chung, Gyusung,Kim, Jaedong,Oh, Han Bin John Wiley Sons, Ltd. 2006 Rapid communications in mass spectrometry Vol.20 No.21
<P>Eleven doubly protonated peptides with a residue homologous to lysine were investigated by electron capture dissociation mass spectrometry (ECD-MS). Lysine homologues provide the unique opportunity to examine the ECD fragmentation behavior by allowing us to vary the length of the lysine side chain, with minimal structural change. The lysine homologue has a primary amine side chain with a length that successively decreases by one methylene (CH<SUB>2</SUB>) unit from the &bond;CH<SUB>2</SUB>CH<SUB>2</SUB>CH<SUB>2</SUB>CH<SUB>2</SUB>NH<SUB>2</SUB> of lysine and the accompanying decrease of its proton affinities: lysine (K), 1006.5(±7.2) kJ/mol; ornithine (K<SUP>*</SUP>), 1001.1(±6.6) kJ/mol; 2,4-diaminobutanoic acid (K<SUP>**</SUP>), 975.8(±7.4) kJ/mol; 2,3-diaminopropanoic acid (K<SUP>***</SUP>), 950.2(±7.2) kJ/mol. In general, the lysine-homologous peptides exhibited overall ECD fragmentation patterns similar to that of the lysine-containing peptides in terms of the locations, abundances, and ion types of products, such as yielding c<SUP>+</SUP> and z<SUP>+.</SUP> ions as the dominant product ions. However, a close inspection of product ion mass spectra showed that ECD-MS for the alanine-rich peptides with an ornithinyl or 2,4-diaminobutanoyl residue gave rise to b ions, while the lysinyl-residue-containing peptides did not, in most cases, produce any b ions. The peptide selectivity in the generation of b<SUP>+</SUP> ions could be understood from within the framework of the mobile proton model in ECD-MS, previously proposed by Cooper (Ref. 29). The exact mass analysis of the resultant b ions reveals that these b ions are not radical species but rather the cationic species with R-CO<SUP>+</SUP> structure (or protonated oxozalone ion), that is, b<SUP>+</SUP> ions. The absence of [M+2H]<SUP>+.</SUP> species in the ECD mass spectra and the selective b<SUP>+</SUP>-ion formation are evidence that the peptides underwent H-atom loss upon electron capture, and then the resulting reduced species dissociated following typical MS/MS fragmentation pathways. This explanation was further supported by extensive b<SUP>+</SUP> ions generated in the ECD of alanine-based peptides with extended conformations. Copyright © 2006 John Wiley & Sons, Ltd.</P>
이정민(Jeong-Min Lee),박규현(Kyu-Hyun Park),정규성(Gyusung Chung) 한국산학기술학회 2014 한국산학기술학회 학술대회 Vol.2014 No.2
현 사회에 다양한 방식으로 사용되고 있는 음악, 이것의 또 다른 이용가능성에 대해 연구해 보고자 한다. 본 연구는 EGF 단백질의 고유 진동수를 측정, 사람이 들을 수 있는 주파수에 맞추어 음계를 결정하였으며, 박자와 화음을 첨가하여 하나의 음악을 완성하였다. 새로운 방식으로 음악을 창조하였다는 것에 의의가 있으며 생명특성의 발현이라는 DNA의 특성을 음악으로 전이해 음악의 논리적 필연성도 이끌어 낼 수 있었다. 다양한 방식으로 응용될 것으로 예상되는 EGF 음악의 형성 과정을 살펴보고자 한다.