• Development and Reproduction
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• v.10 no.3
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• pp.193-196
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• 2006

The process in the formation of primordial germ cells, primitive and early gonadogenesis were investigated by histological examination for the reproductive physiological study in the scorpion fish, Sebastiscus marmoratus. The primordial germ cells about $10\;{\mu}m$ in diameter were observed in the fibrous mesenchymal tissue located between gut and mesonephric duct of the larvae within the maternal body. As the fibrous epithelium extends to the direction of peritoneum, the primordial germ cells moved. From 31 days post parturition, the fibrous epithelium gets thicker, and the primitive gonad starts to form. From 49 days post parturition, as the primitive gonad of the primitive gonad extend, it starts to form cavity, and about 60 days post parturition, the formation of the ovarian cavity is completed. From 79 days post parturition, germ cells proliferated along the inner edge of the ovarian cavity.

• Publications of The Korean Astronomical Society
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• v.6 no.1
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• pp.38-49
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• 1991

Energy density evolution of primordial black holes(PBHs) due to quantum gravitational tunneling effect in the very early Universe is calculated for the four cases of GUTs(grand unified theories) (SM, SUSY SM, SUSY SU(5), SU(5)). For the three of them (SM, SUSY SM, SUSY SU(5)), it is confirmed that there are a considerable amount of PBHs and so it may give a firm support to Lindley's paper(1981) in which he tried to solve the baryon asymmetry problem. It is shown that the formation of PBHs increases the cosmic scale factor R and decreases the total energy density $\rho_t$ faster than in the usual radiation dominated era.

• Mycobiology
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• v.35 no.4
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• pp.226-229
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• 2007

To produce fruiting bodies of Oudemansiella mucida, porcelain fungus, on the oak sawdust medium, additives suitable for the mycelial growth and fruiting body formation were screened. In general, the mycelial growth of the three strains of O. mucida used in this study have been good on oak sawdust mixed rice bran of $20{\sim}30%$. The mycelia incubated in potato dextrose broth for 7 days were inoculated on oak sawdust medium supplemented with various ratios of rice bran and incubated for 30 days at $25^{\circ}C$ in the dark condition until the mycelia of O. mucida fully colonized the media from top to bottom. Then, top surface of the media in the bottles were horizontally scratched with a spatula and filled with tap water for 3 hours. To induce the primordial formation of O. mucida, the bottles were transferred to the mushroom cultivating room under 12 hrs of light (350 lux) and dark condition with relative humidity of 95% at $17^{\circ}C$. The primordia of O. mucida were formed on the surface of oak sawdust media after 7 days of incubation. The mature fruiting bodies were observed 5 days after primordial formation. The fruiting bodies O. mucida were formed on oak sawdust medium mixed with 5 to 30% rice bran. However, abundant fruiting-bodies of O. mucida were produced in oak sawdust medium supplemented with 20% rice bran. This is the first report associated with an artificial fruiting body production of O. mucida in Korea.

• Mycobiology
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• v.34 no.4
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• pp.206-208
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• 2006

To produce an artificial fruiting body of Armillaria mellea on the oak sawdust medium, seven strains of A. mellea were used. The top surface of oak sawdust medium covered with ground raw carrot was inoculated with each of 7 strains and cultured for 30 days at $25^{\circ}C$ in the dark condition until the mycelia of A. mellea completely colonized the medium from top to bottom. Then, the mycelia which were fully covered on the top surface of the medium were scratched slightly with a spatula and filled with tap water for 3 hours. To induce the primordial formation, the 7 strains of A. mellea were transferred to the growth chamber under the illumination (350 lux) of 12 hours and relative humidity of $85{\pm}5%$ in a day and then cultured at $16{\pm}1^{\circ}C$. Only A. mellea IUM 949 could form primordia on the sawdust medium, but the other strains did not make primordia at the same condition. The primordia of A. mellea IUM 949 were formed 10 days after complete colonization of the medium and the fruiting bodies were produced 7 days after a primordial formation. The experimental results suggested that IUM 949 strain might be a good candidate for mass production of fruiting bodies of A. mellea.

• Journal of The Korean Astronomical Society
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• v.14 no.1
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• pp.13-17
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• 1981

The observed radial UBV colour variations (both B-V and U-B) of some globular clusters are examined for correlations with radial variations in the integrated spectra. The results show that the presence of a radial colour gradient is correlated with the presence of a gradient of the CN (and possibly the G-band) line strength, in the sense that the CN (and possibly the G-band) is stronger in the centre (where the cluster is redder) and becomes weaker in the outer region of the cluster (where the cluster is bluer). This may suggest that a primordial abundance, possibly nitrogen and carbon gradient was set up in the early stage of cluster formation.

• Journal of The Korean Astronomical Society
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• v.26 no.1
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• pp.47-64
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• 1993

The photometric evolution of cluster stars are examined for six synthetic clusters in the age range from $2.4\times10^6\;yr\;to\;7.6\times10^8yr$ by using the detailed evolutionary model calculation, and their results are compared with the observed integrated absolute magnitude and colors of 47 clusters. The reasonable agreements of the observed photometric parameters with the synthetic evolutionary sequences imply that there is a general form of time-dependent IMF including the noncoeval formation of stars and its detailed function is changed slightly with various environmental conditions of each primordial cloud.

• Journal of Bio-Environment Control
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• v.18 no.3
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• pp.208-214
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• 2009

In this study, we investigated the effects of the number of air exchanges (NAE) on shape fruit body in two oyster mushrooms, Chunchu 2# and Suhan 2#. The suitable NAEs of Chunchu 2# were $1/10h^{-1}$ at primordial induction, $1/6h^{-1}$ at early stage of growth, $1/4h^{-1}$ at middle stage of growth, $1/4h^{-1}$ at late stage of growth and those of Suhan 2# were $1/6h^{-1}$ at primordial induction, $1/6h^{-1}$ at early stage of growth, $1/4h^{-1}$ at middle stage of growth, and $1/2h^{-1}$ at late stage of growth. In those conditions, the fruit bodies grew well. $CO_2$ concentration hardly affected the primordial formation of both mushrooms. However there were ventilation disturbances over 1500ppm. For instance, the end of pileus rolled up etc. As a result, Suhan 2# required higher ventilation compared with Chunchu 2# and the lower NAE was favorable for growth.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.147.1-147.1
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• 2011

We investigate the chemical differentiation in F, G, K type stars with and without planets to extend the work by Kang et al. (2011) to various spectral types. Since the primordial chemical composition has been preserved in the stellar atmosphere, stellar metallicity can provide the information on the primordial material, which is the potential building block of planets. Therefore, we can explore the favored conditions for planet formation through the comparison of chemical compositions between planet-host stars (PHSs) and stars without planets. In this work, we analyze 19 F, G, and K type stars. In each spectrum, we measure equivalent widths (EWs) of Fe, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni using TAME (Tools for Automatic Measurement of Equivalent width). The abundances of these species can be derived with the measured EWs and MOOG code (Sneden 1973). Like results by precedent studies, we find that planet-host stars have abundances higher than stars without planets. The typical difference in the abundances of Na, Mn, Co and Ni is $0.4{\pm}0.2dex$. In addition, as found in Kang et al. (2011), Mn is the most different element between PHSs and comparison stars.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.81.1-81.1
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• 2021

Stellar kinematics is a useful tool to understand the formation and evolution of young stellar systems. Here, we present a kinematic study of the HII region, NGC 821, using the Gaia Early Data Release 3. NGC 281 contains the open cluster IC 1590. This cluster has a core and a low-stellar density halo. We detect a pattern of cluster expansion from the Gaia proper motion vectors. Most stars radially escaping from the cluster are distributed in the halo. We measure the 1-dimensional velocity dispersion of stars in the core. The velocity dispersion (1 km/s) is comparable to the expected virial velocity dispersion of this cluster, and therefore the core is at a virial state. The core has an initial mass function shallower than that of the halo, which is indicative of mass segregation. However, there is no significant correlation between stellar masses and tangential velocities. This result suggests that the mass segregation has a primordial origin. On the other hand, it has been believed that the formation of young stars in NGC 281 West was triggered by feedback from massive stars in IC 1590. We investigate the ages of stars in the two regions, but the age difference between the two regions is not comparable to the timescale of the passage of an ionization front. Also, the proper motion vectors of the NGC 281 West stars relative to IC 1590 do not show any systematic receding motion from the cluster. Our results suggest that stars in NGC 281 West might have been formed spontaneously. In conclusion, the formation of NGC 281 can be understood in the context of hierarchical star formation model.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.77.2-77.2
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• 2014

Questions of how our Milky Way evolves through the interaction with its environment have been constantly raised. One particularly interesting question is how the metallicity would change as our Milky Way goes through collision with HVCs. Because of the possibility of HVCs providing fuel for star formation in the Galactic disk, we simulate the collision between HVCs and the Galactic disk. More specifically, we trace how the Galactic metallicity changes throughout the process of HVCs colliding with our Milky Way based upon a specific scenario that HVCs are primordial gas left-overs from an ancient galaxy formation. Such mixing between metal-rich gas (disk) and metal-poor HVC can be traced by running numerical simulations with the FLASH code due to its capability of tracking down the abundance change of a specific element such as carbon at each time step of the hydrodynamic evolution. As for now, we give how this mixing depends on model parameters that we choose such as collision speed, initial metallicities, temperature and so on.