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Seo, Jongchul,Jang, Wonbong,Han, Haksoo Wiley Subscription Services, Inc., A Wiley Company 2009 Journal of applied polymer science Vol.113 No.2
<P>Two series of semi-interpenetrating polymer network (semi-IPN) composite films, PEI/bismaleimide (UTBM) and PEI/fluorinated BMI (UTFBM) were prepared using a thermoplastic PEI and two different crosslinkable imide moieties. The effects of chemical structure and content of crosslinkable imide moieties on thermal stability, dielectric properties, and water sorption have been investigated. Glass transition temperature and weight loss temperatures increased with increase in the content of crosslinkable imide moieties, indicating the enhanced thermal stability of the semi-IPN composite films. The refractive indices of the semi-IPN composite systems increased with increasing crosslinkable imide moieties due to the higher polarizabilities of atoms. The water sorption of the semi-IPN composite films was significantly decreased by the incorporation of crosslinkable imide moieties, which are interpreted by morphological structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009</P>
Sequence discrimination of the Zα domain of human ADAR1 during B–Z transition of DNA duplexes
Seo, Yeo-Jin,Ahn, Hee-Chul,Lee, Eun-Hae,Bang, Jongchul,Kang, Young-Min,Kim, Hee-Eun,Lee, Yeon-Mi,Kim, Kyungmin,Choi, Byong-Seok,Lee, Joon-Hwa Elsevier 2010 FEBS letters Vol.584 No.20
<P><B>Abstract</B></P><P>The Zα domain of human ADAR1 (Zα<SUB>ADAR1</SUB>) preferentially binds Z-DNA rather than B-DNA with high binding affinity. Zα<SUB>ADAR1</SUB> binds to the Z-conformation of both non-CG-repeat DNA duplexes and a d(CGCGCG)<SUB>2</SUB> duplex similarly. We performed NMR experiments on complexes between the Zα<SUB>ADAR1</SUB> and non-CG-repeat DNA duplexes, d(CACGTG)<SUB>2</SUB> or d(CGTACG)<SUB>2</SUB>, with a variety of protein-DNA molar ratios. Comparison of these results with those from the analysis of d(CGCGCG)<SUB>2</SUB> in the previous study suggests that Zα<SUB>ADAR1</SUB> exhibits the sequence preference of d(CGCGCG)<SUB>2</SUB>≫d(CACGTG)<SUB>2</SUB>>d(CGTACG)<SUB>2</SUB> through multiple sequence discrimination steps during the B–Z transition.</P>
DETECTION OF SHOCK MERGING IN THE CHROMOSPHERE OF A SOLAR PORE
Chae, Jongchul,Song, Donguk,Seo, Minju,Cho, Kyung-Suk,Park, Young-Deuk,Yurchyshyn, Vasyl IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.805 No.2
<P>It was theoretically demonstrated that a shock propagating in the solar atmosphere can overtake another and merge with it. We provide clear observational evidence that shock merging does occur quite often in the chromosphere of sunspots. Using H alpha imaging spectral data taken by the Fast Imaging Solar Spectrograph of the 1.6 m New Solar Telescope at the Big Bear Soar Observatory, we construct time-distance maps of line-of-sight velocities along two appropriately chosen cuts in a pore. The maps show a number of alternating redshift and blueshift ridges, and we identify each interface between a preceding redshift ridge and the following blueshift ridge as a shock ridge. The important finding of ours is that two successive shock ridges often merge with each other. This finding can be theoretically explained by the merging of magneto-acoustic shock waves propagating with lower speeds of about 10 km s(-1) and those propagating at higher speeds of about 16-22 km s(-1). The shock merging is an important nonlinear dynamical process of the solar chromosphere that can bridge the gap between higher-frequency chromospheric oscillations and lower-frequency dynamic phenomena such as fibrils.</P>
Improvement of the RF cavity for the SKKUCY-10 cyclotron
Lee Jongchul,Ghergherehchi Mitra,Gad Khaled M. M.,Ha Donghyup,Namgoong Ho,Lee Seunghyun,Song Ho Seung,Karatas Berat Can,Chai Jong-Seo 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.9
The SKKUCY-10 cyclotron based on 83.2 MHz, 40 kV half-wave RF cavity was developed at Sungkyunkwan University for the production of medical radioisotopes. The resonant frequency fRF of the cyclotron and the RF coupling coefficient βc of the RF cavity system were measured at various vacuum, and temperature conditions. The normalized multi-pacting intensities at four positions in the power coupler were analyzed to predict the multi-pacting power. Differences, ΔfRF and Δβc , caused by the vacuum, and temperature conditions were modified based on the coupler and tuner gap distances. During the RF conditioning, a constant 15 kW pulse mode and a variable 1 to 15 kW continuous wave mode were employed. The values of the reflection coefficient Γ and βc were 1.2% and 0.8, respectively, when the cavity dissipation power was 12.4 kW at 83.2 MHz. Good agreement between the simulation and experimental data was obtained.
Residual stress and mechanical properties of polyimide thin films
Jang, Wonbong,Seo, Jongchul,Lee, Choonkeun,Paek, Sang-Hyon,Han, Haksoo Wiley Subscription Services, Inc., A Wiley Company 2009 Journal of applied polymer science Vol.113 No.2
<P>Four different structure polyimide thin films based on 1,4-phenylene diamine (PDA) and 4,4′-oxydianiline (ODA) were synthesized by using two different dianhydrides, pyromellitic dianhydride (PMDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), and their residual stress behavior and mechanical properties were investigated by using a thin film stress analyzer and nanoindentation method. The residual stress behavior and mechanical properties were correlated to the morphological structure in polyimide films. The morphological structure of polyimide thin films was characterized by X-ray diffraction patterns and refractive indices. The residual stress was in the range of −5 to 38 MPa and increased in the following order: PMDA-PDA < BPDA-PDA < PMDA-ODA < BPDA-ODA. The hardness of the polyimide films increased in the following order: PMDA-ODA < BPDA-ODA < PMDA-PDA < BPDA-PDA. The PDA-based polyimide films showed relatively lower residual stress and higher hardness than the corresponding ODA-based polyimide films. The in-plane orientation and molecularly ordered phase were enhanced with the increasing order as follows: PMDA-ODA < BPDA-ODA < BPDA-PDA ∼ PMDA-PDA. The PDA-based polyimides, having a rigid structure, showed relatively better-developed morphological structure than the corresponding ODA-based polyimides. The residual stress behavior and mechanical properties were correlated to the morphological structure in polyimide films. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009</P>
CHARACTERISTICS AND PERFORMANCE OF A FAST CCD CAMERA: DALSTA IM30P
YOUNG-MIN SEO,KI-WOONG PARK,JONGCHUL CHAE 한국천문학회 2004 Journal of The Korean Astronomical Society Vol.37 No.5
We have been developing a solar observing system based on a fast CCD camera 1M30P made bythe DALSA company. Here we examine and present the characteristics and performance of the camera.For this we have analyzed a number of images of a at wall illuminated by a constant light source.As a result we found that in the default operating mode 1) the mean bias level is 49 ADU/pix, 2) themean dark current is about 8 ADU/s/pix, 3) the readout noise is 1.3 ADU, and 4) the gain is about 42electrons/ADU. The CCD detector is found to have a linearity with a deviation smaller than 6 %, anda uniform sensitivity better than 1%. These parameters will be used as basic inputs in the analysis ofdata to be taken by the camera.