• The Journal of Internal Korean Medicine
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• v.22 no.4
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• pp.537-546
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• 2001

목적: 고양이 대뇌피질 절편을 사용하여 저산소 발작을 유발한 뒤, 성향정기산이 세포의 이온 환경과 대사의 변화와 관련하여 어떤 영향을 미치는지 연구하였다. 방법: 고양이의 대뇌 피질 절편에 저산소 발작을 유발한 뒤 flame photometry scintillation, Spectrophotometry, method of Jorgensen and Skou, method of Fiske and Subbarow, oxygen monitor, luciferin-luciferase assay 등을 이용하여 세포내 이온함량과 세포대사를 측정하였다. 결과: 성향정기산은 저산소증으로 유발된 세포내의 $K^+$와 $Na^+$의 함량의 변화를 현저하게 지연시켰다. 성향정기산은 Na-K-ATPase의 억제제인 와바인 또는 대사억제제인 2.4-DNP로 유발된 세포내 $K^+$함량의 변화에 어떤 효과도 보이지 않았다. 또한, 정상 상태의 절편뿐만 아니라 저산소 상태의 절편에서 분리된 과립체의 분설에 있어서 Na-K-ATPase의 활동도에 영향을 미치지 않았다. 성향정기산은 저산소 발작하에서 산소 소비량과 세포의 ATP함량이 떨어지는 것을 현저하게 막았다. 또한 ATP를 생산하는 기능을 보호하는 저산소 조직의 사립체를 돕는데 효과적이었다. 결론: 성향정기산은 대뇌 조직의 저산소 발작하에서 세포의 이온 환경과 대사를 보호하는 유익한 효과가 있음을 알 수 있다.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.34.4-35
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• 2009

We have studied the radial g-r color gradients of early-type galaxies in the Sloan Digital Sky Survey (SDSS) DR6 in the redshift range 0.00 < z < 0.06. The color profiles of ~30 per cent of the galaxies in this sample show positive color gradients (centers being bluer). These positive gradient galaxies often show strong $H\beta$ absorption line strengths or emission line ratios that are consistent with star-forming populations. Combining the optical data with Galaxy Evolution Explorer (GALEX) UV photometry, we find that all positive gradient galaxies show blue UV-optical colors. They also exhibit a tendency of having a lower stellar velocity dispersion. Positive gradient galaxies tend to live in lower density regions than negative gradient galaxies and are likely to have a late-type companion galaxy. On the other hand, massive early-type galaxies show negative color gradients. A simplistic population analysis shows that these positive color gradients are visible only for half a billion years after a star burst. Although the effective radius decreases and mean surface brightness increases due to this centrally concentrated star formation, the positions of the positive gradient galaxies on the fundamental plane cannot be reproduced by any amount of recent star formation. Instead it required a lower velocity dispersion.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.57.2-57.2
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• 2019

The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 was successfully launched on last December and is now under the operation phase. The capability of both imaging and spectroscopy is a unique function of the NISS. It has realized the imaging spectroscopy (R~20) with a wide field of view of $2{\times}2deg$. in a wide near-infrared range from 0.95 to $2.5{\mu}m$. The major scientific mission is to study the cosmic star formation history in the local and distant universe. It also demonstrated the space technologies related to the infrared spectro-photometry in space. The NISS is performing the imaging spectroscopic survey for local star-forming galaxies, clusters of galaxies, star-forming regions, ecliptic deep fields and so on. As an extension of the NISS, the SPEHREx (Spectro-Photometer for the History of the Universe Epoch of Reionization, and Ices Explorer) was selected as the NASA MIDEX (Medium-class Explorer) mission (PI Institute: Caltech). As an international partner, KASI will participate in the development and the science for SPHEREx. It will perform the first all-sky infrared spectro-photometric survey to probe the origin of our Universe, to explore the origin and evolution of galaxies, and to explore whether planets around other stars could harbor life. Compared to the NISS, the SPHEREx is designed to have a much wider FoV of $3.5{\times}11.3deg$. as well as wider spectral range from 0.75 to $5.0{\mu}m$. Here, we introduce the status of the two space missions.

• Journal of The Korean Astronomical Society
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• v.50 no.3
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• pp.79-92
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• 2017

We present a BV I optical photometric study of the old open cluster Ruprecht 6 using the data obtained with the SMARTS 1.0 m telescope at the CTIO, Chile. Its color-magnitude diagrams show the clear existence of the main-sequence stars, whose turn-off point is located around $V{\approx}18.45mag$ and $B-V{\approx}0.85mag$. Three red clump (RC) stars are identified at V = 16.00 mag, I = 14.41 mag and B - V = 1.35 mag. From the mean $K_s-band$ magnitude of RC stars ($K_s=12.39{\pm}0.21mag$) in Ruprecht 6 from 2MASS photometry and the known absolute magnitudes of the RC stars ($M_{K_S}=-1.595{\pm}0.025mag$), we obtain the distance modulus to Ruprecht 6 of $(m-M)_0=13.84{\pm}0.21mag$ ($d=5.86{\pm}0.60kpc$). From the ($J-K_s$) and (B - V ) colors of the RC stars, comparison of the (B - V ) and (V - I) colors of the bright stars in Ruprecht 6 with those of the intrinsic colors of dwarf and giant stars, and the PARSEC isochrone fittings, we derive the reddening values of E(B - V ) = 0.42 mag and E(V - I) = 0.60 mag. Using the PARSEC isochrone fittings onto the color-magnitude diagrams, we estimate the age and metallicity to be: $log(t)=9.50{\pm}0.10(t=3.16{\pm}0.82Gyr)$ and $[Fe/H]=-0.42{\pm}0.04dex$. We present the Galactocentric radial metallicity gradient analysis for old (age > 1 Gyr) open clusters of the Dias et al. catalog, which likely follow a single relation of $[Fe/H]=(-0.034{\pm}0.007)R_{GC}+(0.190{\pm}0.080)$ (rms = 0.201) for the whole radial range or a dual relation of $[Fe/H]=(-0.077{\pm}0.017)R_{GC}+(0.609{\pm}0.161)$ (rms = 0.152) and constant ([Fe/H] ~ -0.3 dex) value, inside and outside of RGC ~ 12 kpc, respectively. The metallicity and Galactocentric radius ($13.28{\pm}0.54kpc$) of Ruprecht 6 obtained in this study seem to be consistent with both of the relations.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.47.1-47.1
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• 2018

The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 have successfully developed by KASI. The capability of both imaging and spectroscopy is a unique function of the NISS. At first, it have realized the low-resolution spectroscopy (R~20) with a wide field of view of $2{\times}2deg$. in a wide near-infrared range from 0.95 to $2.5{\mu}m$. The major scientific mission is to study the cosmic star formation history in local and distant universe. It will also demonstrate the space technologies related to the infrared spectro-photometry in space. Now, the NISS is ready to launch in late 2018. After the launch, the NISS will be operated during 2 years. As an extension of the NISS, the SPEHREx (Spectro-Photometer for the History of the Universe Epoch of Reionization, and Ices Explorer) is the NASA MIDEX (Medium-class Explorer) mission proposed together with KASI (PI Institute: Caltech). It will perform the first all-sky infrared spectro-photometric survey to probe the origin of our Universe, to explore the origin and evolution of galaxies, and to explore whether planets around other stars could harbor life. Compared to the NISS, the SPHEREx is designed to have much more wide FoV of $3.5{\times}11.3deg$. as well as wide spectral range from 0.75 to $5.0{\mu}m$. After passing the first selection process, the SPHEREx is under the Phase-A study. The final selection will be made in the end of 2018. Here, we report the status of the NISS and SPHEREx missions.

• Journal of The Korean Astronomical Society
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• v.51 no.1
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• pp.17-25
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• 2018

Detecting exoplanets around giant stars sheds light on the later-stage evolution of planetary systems. We observed the M giant HD 18438 and the K giant HD 158996 as part of a Search for Exoplanets around Northern circumpolar Stars (SENS) and obtained 38 and 24 spectra from 2010 to 2017 using the high-resolution Bohyunsan Observatory Echelle Spectrograph (BOES) at the 1.8m telescope of Bohyunsan Optical Astronomy Observatory in Korea. We obtained precise RV measurements from the spectra and found long-period radial velocity (RV) variations with period 719.0 days for HD 18438 and 820.2 days for HD 158996. We checked the chromospheric activities using Ca $\text\tiny{II}$ H and $H{\alpha}$ lines, HIPPARCOS photometry and line bisectors to identify the origin of the observed RV variations. In the case of HD 18438, we conclude that the observed RV variations with period 719.0 days are likely to be caused by the pulsations because the periods of HIPPARCOS photometric and $H{\alpha}$ EW variations for HD 18438 are similar to that of RV variations in Lomb-Scargle periodogram, and there are no correlations between bisectors and RV measurements. In the case of HD 158996, on the other hand, we did not find any similarity in the respective periodograms nor any correlation between RV variations and line bisector variations. In addition, the probability that the real rotational period can be as longer than the RV period for HD 158996 is only about 4.3%. Thus we conclude that observed RV variations with a period of 820.2 days of HD 158996 are caused by a planetary companion, which has the minimum mass of 14.0 $M_{Jup}$, the semi-major axis of 2.1 AU, and eccentricity of 0.13 assuming the stellar mass of $1.8 M_{\odot}$. HD 158996 is so far one of the brightest and largest stars to harbor an exoplanet candidate.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.71.1-71.1
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• 2013

Among quadruples or higher multiplicity stars, only a few binary systems have been discovered. They are important targets to understand the formation and evolution of multiple stellar systems because we can obtain accurate stellar parameters from photometric and spectroscopic studies. We present the observational results of this kind of rare object 1SWASP J093010.78+533859.5, for which the doubly eclipsing feature had been detected previously from the SuperWASP photometric archive. Individual PSF photometry for two objects with a separation of about 1.9 arcsec was performed for the first time in this study. Our time-series photometric data show that the brighter object A is an Algol-type detached eclipsing binary with an orbital period of 1.3 days and the fainter B is a W UMa-type contact eclipsing binary with a period of 0.23 days. Using the high-resolution optical spectra, we obtained well-defined radial velocity variations of the system A. Furthermore, stationary spectral lines were detected and should have originated from the other stellar component, which was confirmed by the third object contribution from the light curve analysis. No spectral feature of the system B was detected, probably due to its faintness. We obtained the binary parameters and the absolute dimensions from each light curve synthesis. The primary and secondary components of the system A have a spectral type of K1 and K5 main sequences, respectively. Two components of system B have nearly the same type of K3 main sequence. Light variations at out of eclipses were appeared in both systems, interpreting as the effect of stellar spots on these late spectral type stars. We estimated the distances to the systems A and B individually. They may have similar distances of about 70 pc and seem to be gravitationally bound with a separation of about 130 AU. In conclusion, we suggest that 1SWASP J093010.78+533859.5 is a quintuple stellar system with a hierarchical structure of a triple system A(ab)c and a binary system B(ab).

• Journal of Astronomy and Space Sciences
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• v.23 no.4
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• pp.319-326
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• 2006

We present light curves of a short period binary system BL Eridani. The light curves were observed with VRI filters by a 50cm wide field robotic telescope at Siding Spring Observatory (SSO), equipped with a 2K CCD camera, which was developed by Korea Astronomy and Space Science Institute (KASI), and Yonsei University Observatory(YUO). The photometric observations were made on 6 nights by automatic operation mode and remote observation mode at SSO and KASI in Korea, respectively. We obtained new VRI CCD light curves and new 5 times of minima, and analyzed the light corves with the Wilson & Deviney (1971) binary 2005 version and derived the new photometric solutions. The mass ratio q=0.48 in this study shows different value with earlier investigators. According to the model analysis, it is considered that the BL Eri system is currently undergoing contact stage of the two binary components, rather than near-contact stage.

• Journal of Yeungnam Medical Science
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• v.10 no.2
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• pp.409-416
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• 1993

In the method for lithium (Li) analysis, flame emission photometry and atomic absorption spectrophotometry (AAS) have been used most frequently. In addition, lithium can be analyzed by ion-selective electrode (ISE) or fluorscence polarization immunoassay. We evaluated the comparison between AAS method based on the principle of absorption of light at 670.8 nm by Li and ISE method based on the principle of voltage difference generated by Li in contact with lithium ionophore. We compared with those obtained by AAS (AA/AE Spectrophotometer 551, Instrumentation Laboratory Co.) and ISE(CSYNCHRON EL-ISE, Beckman Co.) in the serum and urine of 6 patients and evaluated time-related changes of serum lithium concentration after dosing in both methods. The results are summarized as follows : 1. In within-run precision study for lithium concentration, coefficient variations (CVs, %) ranged from 1.34 to 2.17 for AAS and from 0.34 to 0.85 for ISE method. In between-run precision study for lithium concentration, CVs ranged from 1.23 to 1.72 for AAS and from 0.61 to 1.38 for ISE method. 2. The correlation study between AAS and ISE method resulted in Y=0.946X+0.137 (N=32, r=0.933, X=AAS, Y=ISE) for serum lithium and Y=1.092X+0.977 (N=28, r=0.943, X=AAS, Y=ISE) for urine lithium. 3. Time-related changes of serum lithium concentration in both AAS and ISE method resulted in peak serum levels about 2 hours after dosing and then rapidly decreased after the peak serum level and finally arrived at nearly initial levels about 9 hours after dosing. 4. The reference range of serum lithium was found as undetectable level for both AAS and ISE method and the reference range of urine lithium to the urine creatinine was 0-0.00014 mmol/mg(mean 0.00002 mmol/mg) for AAS method.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.54.1-54.1
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• 2016

Multi-wavelength variability is a staple of active galactic nuclei (AGN). Optical variability probes the nature of the central engine of AGN at smaller linear scales than conventional imaging and spectroscopic techniques. Previous studies have shown that optical variability is more prevalent at longer timescales and at shorter wavelengths. Intra-night variability can be explained through the damped random walk model but small samples and inhomogeneous data have made constraining this model hard. To understand the properties and physical mechanism of intra-night optical variability, we are performing the KMTNet Active Nuclei Variability Survey (KANVaS). Using KMTNet, we aim to study the intra-night variability of ~1000 AGN at a magnitude depth of ~19mag in R band over a total area of ${\sim}24deg^2$ on the sky. Test data in the COSMOS, XMM-LSS, and S82-2 fields was obtained over 4, 6, and 8 nights respectively during 2015, in B, V, R, and I bands. Each night was composed of 5-13 epoch with ~30 min cadence and 80-120 sec exposure times. As a pilot study, we analyzed data in the COSMOS field where we reach a magnitude depth of ~19.5 in R band (at S/N~100) with seeing varying between 1.5-2.0 arcsec. We used the Chandra-COSMOS catalog to identify 166 AGNs among 549 AGNs at B<23. We performed differential photometry between the selected AGN and nearby stars, achieving photometric uncertainty ~0.01mag. We employ various standard time-series analysis tools to identify variable AGN, including the chi-square test. Preliminarily results indicate that intra-night variability is found for ~17%, 17%, 8% and 7% of all X-ray selected AGN in the B, V, R, and I band, respectively. The majority of the identified variable AGN are classified as Type 1 AGN, with only a handful of Type 2 AGN showing evidence for variability. The work done so far confirms there are more variable AGN at shorter wavelengths and that intra-night variability most likely originates in the accretion disk of these objects. We will briefly discuss the quality of the data, challenges we encountered, solutions we employed for this work, and our updated future plans.