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RISS 인기검색어
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- 저자 : Yu Daun (검색결과 5 건)
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The Cortical Neuroanatomy Related to Specific Neuropsychological Deficits in Alzheimer's Continuum
강성훈,Yu Hyun Park,Daun Lee,Jun Pyo Kim,진주희,Yisuh Ahn,Seong Beom Park,Hee Jin Kim,Hye Min Jang,Young Hee Jung,Jaeho Kim,Jongmin Lee,Ji-Sun Kim,Bo Kyoung Cheon,Alice Hahn,이혜주,Duk L. Na,Young Ju Kim,Sang 대한치매학회 2019 Dementia and Neurocognitive Disorders Vol.18 No.3
Background and Purpose: In Alzheimer's continuum (a comprehensive of preclinical Alzheimer's disease [AD], mild cognitive impairment [MCI] due to AD, and AD dementia), cognitive dysfunctions are often related to cortical atrophy in specific brain regions. The purpose of this study was to investigate the association between anatomical pattern of cortical atrophy and specific neuropsychological deficits. Methods: A total of 249 participants with Alzheimer's continuum (125 AD dementia, 103 MCI due to AD, and 21 preclinical AD) who were confirmed to be positive for amyloid deposits were collected from the memory disorder clinic in the department of neurology at Samsung Medical Center in Korea between September 2013 and March 2018. To analyze neuropsychological test-specific neural correlates representing the relationship between cortical atrophy measured by cortical thickness and performance in specific neuropsychological tests, a linear regression analysis was performed. Two neural correlates acquired by 2 different standardized scores in neuropsychological tests were also compared. Results: Cortical atrophy in several specific brain regions was associated with most neuropsychological deficits, including digit span backward, naming, drawing-copying, verbal and visual recall, semantic fluency, phonemic fluency, and response inhibition. There were a few differences between 2 neural correlates obtained by different z-scores. Conclusions: The poor performance of most neuropsychological tests is closely related to cortical thinning in specific brain areas in Alzheimer's continuum. Therefore, the brain atrophy pattern in patients with Alzheimer's continuum can be predict by an accurate analysis of neuropsychological tests in clinical practice.
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Spectroscopic Properties of Flavonoids in Various Aqueous-Organic Solvent Mixtures
Park, Hyoung-Ryun,Daun, Yu,Park, Jong Keun,Bark, Ki-Min Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.1
The characteristic fluorescence properties of quercetin (QCT) and apigenin (API) were studied in various $CH_3OH-H_2O$ and $CH_3CN-H_2O$ mixed solvents. The structure of QCT is completely planar. API is not planar at the ground state but becomes nearly planar at the excited state. If the molecules are excited to the $S_1$ state in organic solvents, QCT exhibits no fluorescence due to excited state intramolecular proton transfer (ESIPT) between the -OH and the carbonyl oxygen, but API shows significant fluorescence because ESIPT occurs slowly. If the molecules are excited to the $S_2$ state, both QCT and API exhibit strong $S_2{\rightarrow}S_o$ emission without any dual fluorescence. As the $H_2O$ composition of both solvents increases, the fluorescence intensity decreases rapidly due to the intermolecular hydrogen bonding interaction. The theoretical calculation further supports these results. The change in fluorescence properties as a function of the solvatochromic parameters was also studied.
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Liu, Hai-Bo,Yu, Daun,Shin, Sung Chul,Park, Hyoung-Ryun,Park, Jong Keun,Bark, Ki-Min Wiley (Blackwell Publishing) 2009 Photochemistry and photobiology Vol.85 No.4
<P>The characteristic fluorescence properties of quercetin-3-O-rhamnoside (QCRM) and quercetin-3-O-rutinoside (QCRT) were studied in CH3OH-H2O and CH3CN-H2O mixed solvents. Although QCRM and QCRT are known as nonfluorescent molecules, significant fluorescence emissions were discovered at 360 nm in CH3OH and CH3CN when they were promoted to the second excited state. The emission band is broad and structureless and the intensity decreases quickly as the H2O composition in the solvent increases. When the amount of H2O exceeds 60% in both mixed solvents, this emission disappears due to the formation of the distorted excited state. This state will be formed due to the strong intermolecular hydrogen bonding between the polar groups of solute and H2O. As the composition of CH3OH or CH3CN in solvent becomes large, the number of molecules having several intramolecular hydrogen bonding increases. Some of these molecules will be changed to a fluorescent species during the decay process, after excitation. The theoretical calculation further supports these results. The change of the lifetimes, quantum yields, and radiative and nonradiative rate constants of molecules was also examined as a function of solvatochromic parameters for CH3OH-H2O and CH3CN-H2O.</P>
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Spectroscopic Properties of Flavonoids in Various Aqueous-Organic Solvent Mixtures
Hyoung-Ryun Park,Yu Daun,박종근,박기민 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.1
The characteristic fluorescence properties of quercetin (QCT) and apigenin (API) were studied in various CH3OH-H2O and CH3CN-H2O mixed solvents. The structure of QCT is completely planar. API is not planar at the ground state but becomes nearly planar at the excited state. If the molecules are excited to the S1 state in organic solvents, QCT exhibits no fluorescence due to excited state intramolecular proton transfer (ESIPT) between the -OH and the carbonyl oxygen, but API shows significant fluorescence because ESIPT occurs slowly. If the molecules are excited to the S2 state, both QCT and API exhibit strong S2 → So emission without any dual fluorescence. As the H2O composition of both solvents increases, the fluorescence intensity decreases rapidly due to the intermolecular hydrogen bonding interaction. The theoretical calculation further supports these results. The change in fluorescence properties as a function of the solvatochromic parameters was also studied.
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Wei-hui Zhong,Zheng Tan,Li-Min Tian,Bao Meng,Yu-hui Zheng,Shi-chao Daun 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.5
To elucidate the differences in the collapse behavior between a single-story beam-column assembly and multi-story frame, two 1/3-scale two-bay composite frames, including a single-story composite beam–column assembly and a three-story composite sub-frame, were designed and quasi-statically tested. The load–displacement responses, failure modes, and internal force development of the two frames were analyzed and compared in detail. Furthermore, the resistance mechanisms of the two specimens were explored, and the respective contributions of different load-resisting mechanisms to the total resistances were quantitatively separated to gain deeper insights. The experimental tests indicated that Vierendeel action was present in the two-dimensional multi-story frames, which led to an uneven internal force distribution among the three stories. The collapse resistance of TSDWA-3S in the flexural stage was not significantly increased by the structural redundancy provided by the additional story, as compared to that of TSDWA-1S. Although the development of the load response was similar in the two specimens at flexural stage, the collapse mechanisms of the multi-story composite frame were much more complicated than those of the single-story beam–column assembly, and the combined action between stories was critical in determining the internal force redistribution and rebalancing of the remaining structure.
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