• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.86.2-86.2
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• 2017

Blue stragglers (BSs) are the objects that are brighter and bluer than the stars at main-sequence turn-off point. In this study, we present the Ca-by and VI photometry for Galactic dwarf spheroidal galaxies using Subaru/Suprime-Cam and investigate the spatial distribution characteristics of BS stars using the hk index as a photometric metallicity indicator. We compare the cumulative radial distribution of the BS stars with those of two groups of red-giant-branch (RGB) stars divided by the hk-index strength, and find that the spatial distribution of all BS stars is closer to that of hk-weak (i.e. metal-poor) RGB stars. We also find that the hk-strong BS stars are more centrally concentrated than the hk-weak ones. We will discuss the use of hk-index as a metallicity indicator for the hot BS stars and suggest possible explanations for the results in terms of the origin of BS stars in the dwarf gal.

• Journal of Microbiology and Biotechnology
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• v.25 no.9
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• pp.1467-1475
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• 2015

The use of microbial extracts containing plant hormones is a promising technique to improve crop growth. Little is known about the effect of bacterial cell-free extracts on plant growth promotion. This study, based on phytohormonal analyses, aimed at exploring the potential mechanisms by which Enterococcus faecium LKE12 enhances plant growth in oriental melon. A bacterial strain, LKE12, was isolated from soil, and further identified as E. faecium by 16S rDNA sequencing and phylogenetic analysis. The plant growth-promoting ability of an LKE12 bacterial culture was tested in a gibberellin (GA)-deficient rice dwarf mutant (waito-C) and a normal GA biosynthesis rice cultivar (Hwayongbyeo). E. faecium LKE12 significantly improved the length and biomass of rice shoots in both normal and dwarf cultivars through the secretion of an array of gibberellins (GA₁, GA₃, GA₇, GA₈, GA₉, GA₁₂, GA₁₉, GA₂₀, GA₂₄, and GA₅₃), as well as indole-3-acetic acid (IAA). To the best of our knowledge, this is the first study indicating that E. faecium can produce GAs. Increases in shoot and root lengths, plant fresh weight, and chlorophyll content promoted by E. faecium LKE12 and its cell-free extract inoculated in oriental melon plants revealed a favorable interaction of E. faecium LKE12 with plants. Higher plant growth rates and nutrient contents of magnesium, calcium, sodium, iron, manganese, silicon, zinc, and nitrogen were found in cell-free extract-treated plants than in control plants. The results of the current study suggest that E. faecium LKE12 promotes plant growth by producing GAs and IAA; interestingly, the exogenous application of its cell-free culture extract can be a potential strategy to accelerate plant growth.

• Korean Journal of Plant Resources
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• v.28 no.2
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• pp.253-258
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• 2015

In South Korea, Pinus pumila (Pall.) Regel (dwarf stone pine) has been designated as a critically endangered species by the Korea Forest Service. We have difficulties in obtaining the seeds of P. pumila because P. pumila grows only in the Daecheongbong area (1550–1700 m above sea level) of Mt. Seorak and almost all of its cones are damaged by birds and rodents. For establishing an ex situ conservation stand of P. pumila, this study was conducted to figure out the effects of wet cold (cold stratification, prechilling) and GA₃ treatment on the germination of P. pumila seeds. After cold stratification (1, 2, 3, 4, 5 months), prechilling (1, 2, 3, 4, 5 months) and GA₃ treatment (0, 100, 500, 1,000, 2,000, 3,000 ㎎/L), seeds were placed on petri-dishes at 25℃ under light condition. The percentage of germination, mean germination time and the germination rate were investigated. The results showed that both of the cold stratification and prechilling were effective in improving germination performances. However, there were no significant differences in performances between the two cold treatments. Within each treatment, the germination performances improved with the period of treatment. However, after three months of treatment, the performances showed no significant improvement. The gibberellin treatment was also effective in improving seed germination of P. pumila. The percentage of germination reached 79.0% in the seeds treated with 100 ㎎/L of GA₃. However, the germination performances decreased at high concentration of GA₃ treatments (over 2000 ㎎/L). In conclusion, cold stratification (over 3 months) or 100 ㎎/L of GA₃ treatment was considered to be the appropriate method for seedling production of P. pumila.

• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.417-420
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• 2009

We have used the near-infrared $JHK_S$ photometric data of resolved stars in a nearby dwarf elliptical galaxy NGC 205 to determine the magnitudes of the red giant branch tip (TRGB). By applying Savitzky-Golay filter to the observed luminosity functions (LFs) in each band, we derived the second derivatives of the LFs so as to determine the magnitudes of the TRGB. Absolute magnitudes of the TRGB in $JHK_S$ bands were measured from the Yonsei-Yale isochrones. By comparing the determined apparent magnitudes and the theoretical absolute magnitudes of the TRGB, we estimated the distance moduli of NGC 205 to be (m - M) = $24.10{\pm}0.08$, $24.08{\pm}0.12$ and $24.14{\pm}0.14$ in J, H, and $K_S$ bands, respectively.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.39.4-40
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• 2016

We aim to investigate formation of satellite sub-galactic structures around isolated dwarf galaxies using cosmological hydrodynamic zoom simulations. For this, we modify a cosmological hydrodynamic code, GADGET-3, in a way that includes gas cooling down to T~10K, gas heating by universal reionization when z < 8.9, UV shielding for high density regions of $n_{shield}$ > $0.014cm^{-3}$, star formation in the dense regions ($n_H$ > $100cm^{-3}$), and supernova feedback. To get good statistics, we perform three different simulations for different target galaxies of the same mass of ${\sim}10^{10}M_{sun}$. Each simulation starts in a cubic box of a side length of 1Mpc/h with 17 million particles from z = 49. The mass of dark matter (DM) and gas particle is $M_{DM}=4.1{\times}10^3M_{sun}$ and $M_{gas}=7.9{\times}10^2M_{sun}$, respectively, thus each satellite sub-galactic structure can be resolved with more than hundreds or thousands particles. We analyze total 90 sub-galactic structures that have formed outside of the main halos but infall the main halos. We found that 1) mini halos that interact more with the other mini halos tend to accrete the more mass, 2) mini halos that interact more before the reionization tend to form more stars, 3) mini halos with the more interaction tend to approach closer to the galactic center and have the lower orbital circularity, 4) survivals even in the strong tidal fields evolve baryon dominated system, such as globular clusters.

• Animal Bioscience
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• v.35 no.3
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• pp.377-384
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• 2022

Objective: This study was conducted to estimate multi-trait genetic parameters for somatic cell score (SCS), milk yield and type traits in Nigerian Dwarf (ND) goats from the United States. Methods: Data from 1,041 ND goats in the United States with kiddings in 95 herds were used to estimate multi-trait genetic parameters for SCS, milk (MILK), fat (FAT), and protein (PROT) yields, and 14 type traits. An 18-trait mixed linear animal model for lactation mean SCS (Log₂), MILK, FAT, PROT, and 14 type traits was applied. A factor analytic approach (FA1) in ASReml software was used to obtain convergence. Results: Averages for SCS were low (2.85±1.29 Log₂), and were 314±110.6, 20.9±7.4, and 14±4.9 kg, respectively, for MILK, FAT, and PROT. Heritabilities for SCS, MILK, FAT, and PROT were 0.32, 0.16, 0.16, and 0.10, respectively. The highest heritabilities for type traits were for stature (0.72), teat diameter (0.49), and rump width (0.48), and the lowest estimates were for dairyness (0.003) and medial suspensory ligament (0.03). Genetic correlations of SCS with MILK, FAT, and PROT were positive but low (0.25, 0.18, and 0.23, respectively). Genetic and phenotypic correlations between MILK, FAT, and PROT were high and positive (≥0.66). Absolute values of genetic correlations involving SCS with type traits were generally low or no different from zero. Most of the phenotypic correlations involving SCS with type traits were low. No serious unfavorable genetic correlations between milk yield traits and SCS or between milk yield traits or SCS and type traits were found. Conclusion: Genetic variation exists in the ND breed for most studied traits. The development of selection programs based on these estimates may help accelerate favorable multi-trait genetic changes in this breed.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2005.11a
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• pp.61-61
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• 2005

• Journal of Radiation Industry
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• v.5 no.3
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• pp.231-236
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• 2011

'Ggoma' is a new Hibiscus dwarf type variety developed by gamma irradiation at the Korea Atomic Energy Research Institute (KAERI). This study was conducted to determine the best optimum cultural callus formation and shoot regeneration condition. Sterilized leaf tissues were cultured on MS (Marashige and skoog's) medium containing 3% sucrose, 0.8% agar with different concentration and combination of TDZ, 2, 4-D, KT, BA, and 2iP for 4 weeks in vitro culture. MS medium containing 2,4-D $0.1mg\;l^{-1}$ and BA $0.5mg\;l^{-1}$ were most effective on callus formation and growth. After 4 weeks, callus was transferred on BA (0.5, 1, $1.5mg\;l^{-1}$) and TDZ (0.1, 0.2, $0.3mg\;l^{-1}$) for shoot formation. The best condition for inducing the shoot from callus was BA $1.5mg\;l^{-1}$ and TDZ $0.3mg\;l^{-1}$. This result will be useful for the rapid multiplication of Hibiscus syriacus L.var. Ggoma.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.49.3-50
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• 2015

Early-type dwarf galaxy (ETDG), the most abundant galaxy type in clusters, were recently shown to exhibit a wide variety in their properties. Particularly, the presence of blue cores in some ETDGs supports the scenario of late-type galaxy infall and subsequent transformation into red, quiescent ETDGs. While several transformation mechanisms for these ETDGs with blue core within cluster environment have been proposed, all these processes are able to explain only some of the observational properties of ETDGs such as stellar populations and structural parameters. In this context, internal kinematic properties of blue-cored ETDGs provide the most crucial evidence to discriminate different processes for the formation of these galaxies. We present a kinematic analysis of two blue-cored ETDGs in the Virgo cluster based on long-slit data obtained from Gemini Multi-Object Spectrographs (GMOS) observations. We find that the observed galaxies show kinematically decoupled sub-components in the velocity profile such as discontinuity or counter-rotating component. We discuss possible scenarios of formation of these transitional galaxies.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.77.1-77.1
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• 2012

We have performed cosmological hydrodynamic simulations that include the effects of radiative heating/cooling, star formation, feedback by supernova explosions, and metallicity evolution. Our simulations cover a cubic box of a side length 4 Mpc/h with 130 million particles. The mass of each particle is $3.4{\times}10^4M_{\odot}$, thus sub-galactic mini-halos can be resolved with more than hundred particles. Our simulation follows the whole formation process of the mini-halos (M< $10^7M_{\odot}$) around dwarf galaxies. We discuss various properties of the mini halos such as mass function, specific frequency, baryon-to-dark matter ratio, metallicity, spatial distribution, and orbit eccentricity distribution as functions of redshift and host galaxy mass. We also discuss how the formation and evolution of the mini halos are affected by the epoch of the reionization.