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DETECTION OF X-RAY EMISSION FROM GALAXIES INSIDE AND TOWARDS THE NEARBY VOIDS
KIM CHULHEE,BOLLER TH.,GHOSH KAJAL K. The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.1
We searched for X-ray emission from the 665 galaxies inside and towards the nearby voids by analyzing the ROSAT All-Sky Survey (RASS) data as well as the ROSAT pointed observations (PSPC). As a result we have detected six X-ray emitting galaxies. Two (UGC 10205 and NGC 7509) are in the high density region in the local void, three (UGC 749, MCG +11-10-073, and Mrk 464) are towards the nearby voids, and UGC 32 is located in the low density region. We carried out a timing analysis for both Mrk 464 and UGC 32, and a spectral analysis for Mrk 464. The light curve of Mrk 464 shows the possibility of periodic X-ray flux variation and UGC 32 shows weak, but rapid variation.
PULSATIONAL CHARACTERISTICS OF V1719 CYGNI WITH PECULIAR LIGHT CURVE
KIM CHULHEE,KIM SEUNG-LI,SADAKANE KOZO The Korean Astronomical Society 1993 Journal of The Korean Astronomical Society Vol.26 No.2
The light curve and radial velocity curve of multiperiodic dwarf cepheid VI719 Cyg (HD200925) with peculiar light curve have been reanalyzed in order to identify the oscillation modes to confirm the helium settling within the envelope. To do these, through the period search for the photometric and radial velocity data from the literature, two different periods were determined and the oscillation modes corresponding to the first and second periods were identified as the fundamental and first radial overtones. Hence the helium settling within the envelope was confirmed from the period ratio. The color excess, metallicity, effective temperature, and surface gravity corresponding to two different modes were determined and it was found that these parameters almost do not depend upon different oscillation mode. By utilizing the surface brightness method, we investigated the variation of angular diameter and radial displacement and it was found that the angular variation is very peculiar. Also by referring to the stellar models, mass and age were determined as $2.7M_{\bigodot}$ and 0.42 Gyr respectively which make this variable star heavier and younger than other multimode dwarf cepheids. Preliminary spectroscopic CCD observations were carried out and it was found that Mg in VI719 Cygni is nearly solar abundent according to the analysis of $5172.68{\AA}MgI$ line which is inconsistent with the photometric result. It was suggested that VI719 Cyg may be classified as a $\rho$ Pup stars according to the photometric characteristics.
Conceptual design study of the K-DEMO magnet system
Kim, Keeman,Oh, Sangjun,Park, Jong Sung,Lee, Chulhee,Im, Kihak,Kim, Hyung Chan,Lee, Gyung-Su,Neilson, George,Brown, Thomas,Kessel, Charles,Titus, Peter,Zhai, Yuhu Elsevier 2015 Fusion engineering and design Vol.96 No.-
<P><B>Abstract</B></P> <P>As the ITER is being constructed, there is a growing anticipation for an earlier realization of fusion energy. A major design philosophy for the initiated conceptual design study for a steady-state Korean fusion demonstration reactor (K-DEMO) is engineering feasibility. A two-staged development plan is envisaged. K-DEMO is designed not only to demonstrate a net electricity generation and a self-sustained tritium cycle, but also to be used, in its initial stage, as a component test facility. Then, in its second stage, a major upgrade is carried out by replacing in-vessel components in order to show a net electricity generation on the order of 500MWe. After a thorough 0-D system analysis, the major radius and minor radius are chosen to be 6.8m and 2.1m, respectively. In order to minimize wave deflection, a top-launch high frequency (>200GHz) electron cyclotron current drive (ECCD) system will be the key system for the current profile control. For matching the high frequency ECCD, a high toroidal field (TF) is required and can be achieved by using high current density Nb<SUB>3</SUB>Sn superconducting conductor. The peak magnetic field reaches to 16T with the magnetic field at the plasma center above 7T. Key features of the K-DEMO magnet system include the use of two TF coil winding packs, each of a different conductor design, to reduce the construction cost and save the space for the magnet structure material.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Perform a preliminary conceptual study for a steady-state Korean DEMO reactor. </LI> <LI> Present a preliminary design of TF (toroidal field) magnet. </LI> <LI> Present a preliminary design of CS (central solenoid) magnet. </LI> <LI> Present a preliminary design of PF (toroidal field) magnet. </LI> </UL> </P>
Kim, Hyehyeon,Kim, Saehee,Park, Chiyoung,Lee, Hyemi,Park, Heon Joo,Kim, Chulhee WILEY‐VCH Verlag 2010 Advanced Materials Vol.22 No.38
<P><B>Cyclodextrins</B> tethered onto a mesoporous silica nanoparticle via disulfide stalking are effective gatekeepers not only to entrap guest molecules in the pore but also to release the guest in response to glutathione (GSH). The PEGylated nanocontainers also exhibit efficient GSH‐mediated release of doxorubicin in cancer cells. Our approach offers unique applications for multifunctional delivery systems. </P>
SoxF Transcription Factors Are Positive Feedback Regulators of VEGF Signaling
Kim, Kangsan,Kim, Il-Kug,Yang, Jee Myung,Lee, Eunhyeong,Koh, Bong Ihn,Song, Sukhyun,Park, Junseong,Lee, Sungsu,Choi, Chulhee,Kim, Jin Woo,Kubota, Yoshiaki,Koh, Gou Young,Kim, Injune Grune & Stratton 2016 Circulation research Vol.119 No.7
<P>Rationale: Vascular endothelial growth factor (VEGF) signaling is a key pathway for angiogenesis and requires highly coordinated regulation. Although the Notch pathway-mediated suppression of excessive VEGF activity via negative feedback is well known, the positive feedback control for augmenting VEGF signaling remains poorly understood. Transcription factor Sox17 is indispensable for angiogenesis, but its association with VEGF signaling is largely unknown. The contribution of other Sox members to angiogenesis also remains to be determined. Objective: To reveal the genetic interaction of Sox7, another Sox member, with Sox17 in developmental angiogenesis and their functional relationship with VEGF signaling. Methods and Results: Sox7 is expressed specifically in endothelial cells and its global and endothelial-specific deletion resulted in embryonic lethality with severely impaired angiogenesis in mice, substantially overlapping with Sox17 in both expression and function. Interestingly, compound heterozygosity for Sox7 and Sox17 phenocopied vascular defects of Sox7 or Sox17 homozygous knockout, indicating that the genetic cooperation of Sox7 and Sox17 is sensitive to their combined gene dosage. VEGF signaling upregulated both Sox7 and Sox17 expression in angiogenesis via mTOR pathway. Furthermore, Sox7 and Sox17 promoted VEGFR2 (VEGF receptor 2) expression in angiogenic vessels, suggesting a positive feedback loop between VEGF signaling and SoxF. Conclusions: Our findings demonstrate that SoxF transcription factors are indispensable players in developmental angiogenesis by acting as positive feedback regulators of VEGF signaling.</P>
Self-assembly of dendron-helical polypeptide copolymers: organogels and lyotropic liquid crystals
Kim, Kyoung Taek,Park, Chiyoung,Kim, Chulhee,Winnik, Mitchell A.,Manners, Ian Royal Society of Chemistry 2006 Chemical communications Vol.2006 No.13
<P>New macromolecular self-assembling building blocks, dendron-helical polypeptide copolymers, have been synthesized; these materials possess a well-defined 3-D shape and self-assemble in solution to form nanoribbon and lyotropic liquid crystalline phases.</P> <P>Graphic Abstract</P><P>New macromolecular self-assembling building blocks, dendron-helical polypeptide copolymers, have been synthesized. These materials possess a well-defined 3-D shape and self-assemble in solution to form nanoribbon and lyotropic liquid crystalline phases. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b516625j'> </P>
Kim, Chulhee,Moon, B.-K. American Institute of Physics 2011 The Astronomical journal Vol.141 No.4
<P>A new method was developed to estimate the effective temperature, surface gravity, and metallicity of cool stars using only photometric indices in the uvby color system. In a graphical method, T<SUB>eff</SUB> and log g were determined for all of the different values of [Fe/H] using model atmosphere grids with respect to (b – y):c<SUB>1</SUB> and (b – y):m<SUB>1</SUB> pair indices. Then, a three-dimensional figure where X-, Y-, and Z-axes correspond to T<SUB>eff</SUB>, log g, and [Fe/H] was produced. By reading an intersection of two curves formed by a connection of three parameters obtained from the (b – y):c<SUB>1</SUB> and (b – y):m<SUB>1</SUB> pair indices on each of the three projected planes, T<SUB>eff</SUB>, log g, and [Fe/H] were determined simultaneously. In addition, an analytical method was devised based on the same algorithm developed for the graphical method. The new method was applied to a number of field dwarfs and giants, and the results were compared with those from a spectroscopic method and other photometric calibrations.</P>