• Journal of The Korean Astronomical Society
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• v.24 no.1
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• pp.13-24
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• 1991

We construct a simple photometric evolution model of galaxies based on the evolutionary population synthesis. In our models an exponentially decreasing SFR with a power law IMF is used to compute the UBV colors of galaxies from ellipticals to late type spirals. It is shown that the integrated colors of galaxies with different Hubble type can be explained by one parameter, SFR.

• Publications of The Korean Astronomical Society
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• v.25 no.3
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• pp.83-90
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• 2010

I briefly review what has been learned from determinations of mean stellar ages and abundances from integrated light studies of early-type galaxies, and discuss some new questions posed by recent data. A short discussion of spectroscopic ages is presented, but the main focus of this review is on the abundances of Fe, Mg, Ca, N, and C, obtained from comparisons of measurements taken in integrated spectra of galaxies with predictions from stellar population synthesis models.

• The Korean Journal of Zoology
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• v.34 no.2
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• pp.148-158
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• 1991

The purpose of this research was to establish the culture condition for dissociated submandibu -lar gland (SG) cells. After trypsin digestion of SG from 3-4 weeks old mice, dissociated cells were cultured in 1OO/o fetal bovine serum-Dulbecco's modified Eagle's medium (FBS-DME) or 0.5-2% low protein serum replacement-DME (LPSR-DME) on plastic surface to form monolayer. The effects of FBS, LPSR and hormones on the growth and function of cultured SG cells were examined. SG cells dissociated by enzyme were successfully cultured and were characterized as epithelial-like cells by light and electron microscope. The maximal DNA synthesis of cultured SG cells was achieved by DME containing 5-10% FBS. The same results were obtained when the effects of LPSR on cell proliferation were examined up to a LPSR concentration of 2%. SG cells cultured in 20/o LPSR-DME expressed a population doubling time of 42.5 hrs and a saturation density of 1.2 $\times$10 5cell/cm$^2$. Dihydrotestosterone (DHT) in medium did not influence on the DNA synthesis of the cultured SG cells, but stimulated protein synthesis of the SG cells. Thyroxine (T4) stimulated protein synthesis of the SCI cells markedly in a dose-dependent fashion. EGF secretion by the cultured SG cells increased significandy by DHT and or T4 trearment. This finding indicated that secretion of EGF by the SG cells was under the control of the hormones such as androgen and thyroid hormones. It seems to be that the culture condition described here can be used as a useful tool for further research on the SCI cells.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.31.2-31.2
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• 2012

We present the Yonsei Evolutionary Population Synthesis (YEPS) models for spectroscopic and photometric evolutions of simple and composite stellar populations. The models are based on the most up-to-date Yonsei-Yale stellar evolutionary tracks and BaSel 3.1 flux libraries, and provide integrated spectroscopic quantities of Lick/IDS system including high-order Balmer absorption-lines. Special care has been taken to incorporate the systematic variation of horizontal branch (HB) morphology as functions of metallicity, age, alpha-element mixture, and helium abundance of simple stellar populations. Our models for normal-helium stellar populations indicate that the realistic modeling of HB and alpha-element brings about 5 Gyr and 0.1 dex differences in age and metallicity estimations, respectively, compared to those without these effects. The HB effect does not depend on the specific choice of stellar libraries and alpha-element enhancements, and this effect is non-negligible even in the metal sensitive absorption indices, such as Mg2 and Mg b. Comparison of the models to observations reveals that the HB and alpha-element effects are critical in understanding otherwise inexplicable phenomena found in globular cluster systems in the Milky Way and nearby galaxies, including the observed bimodality of the line strengths of globular clusters in massive galaxies. In addition, we found that helium-enhanced stellar populations, which are the major sources of extreme HB stars, bring about increased FUV, NUV fluxes, and thus the model colors of those filters become extremely blue. Age dating based on the YEPS model with normal-helium stellar populations reveals that the evidence for 'downsizing' of elliptical galaxies is found not only in the local field but also in Coma cluster, and that the mean age of elliptical galaxies in Coma cluster is about 1.4 Gyr younger than the mean age of those in the local field. We also find that our models with helium-enhanced subpopulations can naturally reproduce the strong UV-upturns observed in giant elliptical galaxies assuming an age similar to that of old GCs in the Milky Way.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1219-1224
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• 2006

This study investigates the effect of $NH_3$ gas upon the growth of carbon nanotubes (CNTs) using thermal chemical vapor deposition. It is considered that the CNT synthesis occurs mainly through two steps, clustering of catalyst particles and subsequent growth of CNTs. We thus introduced $NH_3$ during either an annealing or growth step. When $NH_3$ was fed only during annealing, CNTs grew longer and more highly crystalline with diameters unchanged. An addition of $NH_3$ during growth, however, resulted in shorter CNTs with lower crystallinity while increased their diameters. Vertically aligned, highly populated CNT samples showed poor field emission characteristics, leading us to apply post-treatments onto the CNT surface. The CNTs were treated by adhesive tapes or etched back by dc plasma of $N_2$ to reduce the population density and the radius of curvatures of CNTs. We discuss the morphological changes of CNTs and their field emission properties upon surface treatments.

• Journal of Physiology & Pathology in Korean Medicine
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• v.23 no.5
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• pp.1012-1018
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• 2009

The purpose of this research was to investigate the pharmacological effects of preparations containing beta-carotene, $Beautycarotene^{TM}$. $Beautycarotene^{TM}$ increased the collagen synthesis in CCD-986sk cells, DPPH radical scavenging activity and tyrosinase inhibitory activity in vitro system. In addition, it enhanced the viability of murine thymocytes and the population of splenic $CD4^+$ cells. Also, it increased the phagocytic activity of murine peritoneal macrophages. These results indicate that $Beautycarotene^{TM}$ can have a protective effect of skin via the diverse action, such as the stimulatory action of collagen synthesis, antioxidative action, tyrosinase inhibitory action and immune regulatory action.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.75-75
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• 2013

Recent observations have shown that some massive globular clusters (GCs) host multiple stellar populations having different heavy element abundances enriched by supernovae. They usually accompany multiple red giant branches (RGBs) in the color-magnitude diagrams (CMDs), and are distinguished from most of the other GCs which display variations only in light element abundances. In order to investigate the star formation histories of these peculiar GCs, we have constructed synthetic CMDs based on the updated versions of Yonsei.Yale ($Y^2$) isochrones and horizontal branch evolutionary tracks which include the cases of enhancements in both helium and the total CNO abundances. To estimate ages and helium abundances of subpopulations in each GC, we have compared our models with the observations on the Hess diagram by employing a ${\chi}^2$ minimization technique. In this talk, we will present our progress in the population modeling for these GCs with multiple RGBs.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.56.2-56.2
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• 2012

We present a study of the asymptotic giant branch (AGB) contribution to the total Ks band luminosity of star clusters in the Large Magellanic Cloud (LMC) as a function of age. AGB stars, a representative intermediate-age population, are a strong source of NIR to MIR emission so that they are a critical component for understanding the near-to-mid infrared observation of galaxies. Current calibration of IR emission in evolutionary population synthesis (EPS) models for galaxies is mainly based on a small number of LMC star clusters. However, each LMC star cluster with intermediate age contains only a few AGB stars so that it suffers from a stochastic effect. Therefore a large number of them are needed for solid calibration of the EPS models. We study physical properties of a large number of LMC star clusters to estimate the Ks band luminosity fraction of AGB stars in star clusters as a function of age. We discuss the stochastic effect in calibrating models, and the importance of this calibration for studying the evolution of not only nearby galaxies but also of high-z galaxies.

• Journal of The Korean Astronomical Society
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• v.22 no.1
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• pp.1-24
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• 1989

By applying population synthesis method, stellar populations in the nuclei of M31 and M32 are studied. We obtained five and four models for M31 and M32 respectively, for different main sequence turn-offs and keeping the astrophysical constraints as loose as possible. The best models for M31 and M32 are thought to have G0-5 and F5-8 main sequence trun-offs respectively. These models show that the main sequence stars outnumber the giants, which indicates the dwarf-dominance in external galactic nuclei. Even though there are some computational difficulties because of non-uniqueness in solution, two major points can be pointed out when compared to the previous papers. First, the ultraviolet deficiency expected from the conventional metal rich population models is not detected in our models, Instead ultraviolet radiation turns out to be somewhat higher than that of observation. Second one is the minor contribution from the Super Metal Rich (SMR) K giants to the integrated light of the program galaxies. That is, in our models, the SMR contribution is at best the same level as normal giants contrary to the SMR dominance of previous models. Since the loose astrophysical constraints are the major difference of our study from the previous ones, one should re-examine carefully for their validity further.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.3
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• pp.1077-1079
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• 2012

The Kashmiri population is culturally distinct with special dietary features owing to the temperate climatic conditions of Kashmir valley. This has habituated the population to preserve food in smoked, pickled and sundried forms which include considerable amounts of $N$-nitroso compounds (NOCs). These are known to cause cytotoxicity, DNA damage, mutation, unscheduled DNA synthesis and DNA methylation. All of these changes at molecular level are known to contribute to the pathogenesis of cancer. One of the prominent NOCs found in Kashmiri food is $N$-Nitrosodimethylamine (NDMA). Here we review the occurrence of NDMA in sundried foods, dried fish, kehwa, traditional pickle, $Brassica$ $oleracia$ and $tobbaco$. We also discuss its possible role in the high prevalence of gastrointestinal cancers in Kashmir.