• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2006년도 한국우주과학회보 제15권1호
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• pp.28-28
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• 2006

• 한국해양바이오학회지
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• 제5권4호
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• pp.40-45
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• 2011

Microalgae are one of the major, sustaining components of ecosystem processes and are responsible for biogeochemical reactions that drive our climate changes. Despite this, many marine microalgae are poorly described and little is known of their abundance and distribution along the coastal areas of Sooyoung Bay, Busan, South Korea. The present study has been conducted from November, 2011 to August, 2009 with the objective to provide an overview of the taxonomy diversity and abundance of microalgae along the coastal areas of the Sooyoung Bay. Water samples were collected from different sites, which were located by using a GPS tracker. Chlorophyll fluorescence of the water samples were measured by using ToxY-PAM dual-channel yield analyzer. The chlorophyll fluorescence values were relatively higher during the spring and summer and even in the region near to the sea port. Similarly the abundance of microalgae was higher near the port but diversity index had lower values. The temperature and pH values were same at all the sites. However, only the temperature varied during the sampling period, with higher values during summer and lower in winter. From the preliminary results, the following class of microalgae were found; Bacillariophyceae, Dinophyceae, Silicoflagellate and Cryptophyceae. With a future ongoing work, microalgae are being isolated to establish single cell culture and for identification using light microscopic observations, photography and molecular approaches.

• Journal of Astronomy and Space Sciences
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• 제36권3호
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• pp.105-113
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• 2019

Spectroscopic observations of barium star ${\zeta}$ Capricornus (HD204075) obtained at the 8.2 m telescope of the European Southern Observatory, with a spectral resolving power R = 80,000 and signal to noise ratio greater than 300, were used to refine the atmospheric parameters. We found new values for effective temperature ($T_{eff}=5,300{\pm}50K$), surface gravity ($log\;g=1.82{\pm}0.15$), micro-turbulent velocity ($v_{micro}=2.52{\pm}0.10km/s$), and iron abundance ($log\;N(Fe)=7.32{\pm}0.06$). Previously published abundances of chemical elements in the atmosphere of HD204075 were analyzed and no correlations of these abundances with the second ionization potentials of these elements were found. This excludes the possible influence of accretion of hydrogen and helium atoms from the interstellar or circumstellar environment to the atmosphere of this star. The accretion of nuclear processed matter from the evolved binary companion was primary cause of the abundance anomalies. The young age of HD204075 allows an estimation of the time-scale for the creation of the abundance anomalies arising from accretion of interstellar hydrogen and helium as is the case of stars with low magnetic fields; which we estimate should exceed $10^8$ years.

• 천문학회보
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• 제28권1호
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• pp.60-60
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• 2003

• Journal of Microbiology and Biotechnology
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• 제32권10호
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• pp.1275-1283
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• 2022

Understanding soil microbial community structure in the Arctic is essential for predicting the impact of climate change on interactions between organisms living in polar environments. The hypothesis of the present study was that soil microbial communities and soil chemical characteristics would vary depending on their associated plant species and local environments in Arctic mature soils. We analyzed soil bacterial communities and soil chemical characteristics from soil without vegetation (bare soil) and rhizosphere soil of three Arctic plants (Cassiope tetragona [L.] D. Don, Dryas octopetala L. and Silene acaulis [L.] Jacq.) in different local environments (coal-mined site and seashore-adjacent site). We did not observe any clear differences in microbial community structure in samples belonging to different plant rhizospheres; however, samples from different environmental sites had distinct microbial community structure. The samples from coal-mined site had a relatively higher abundance of Bacteroidetes and Firmicutes. On the other hand, Acidobacteria was more prevalent in seashore-adjacent samples. The relative abundance of Proteobacteria and Acidobacteria decreased toward higher soil pH, whereas that of Bacteroidetes and Firmicutes was positively correlated with soil pH. Our results suggest that soil bacterial community dissimilarity can be driven by spatial heterogeneity in deglaciated mature soil. Furthermore, these results indicate that soil microbial composition and relative abundance are more affected by soil pH, an abiotic factor, than plant species, a biotic factor.

• 천문학회지
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• 제22권2호
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• pp.81-99
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• 1989

Applying five morphological parameters defined along the main sequence (MS), red giant branch (RGB) and horizontal branch (HB) in the C-M diagram (CMD), and the transition period-luminosity relation for RR Lyrae variables, some basic physical quantities such as helium abundance, age, mass and luminosity are determined for 21 well observed globular clusters with combination of evolutionary models and atmospheric models properly chosen by the numerical test. The dependences of these quantities on the age and chemical abundance are investigated.

• 천문학회지
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• 제14권2호
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• pp.55-71
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• 1981

On the basis of observational constraints, particularly the relationship between metal abundance and cumulative stellar mass, a simple two-zone disk-halo model for the chemical evolution of our Galaxy was investigated, assuming different chemical processes in the disk and halo and the infall rates of the halo gas defined by the halo evolution. The main results of the present model calculations are: (i) The halo formation requires more than 80% of the initial galactic mass and it takes a period of $2{\sim}3{\times}10^9$ yrs. (ii) The halo evolution is divided into two phases, a fast collapse phase ($t=2{\sim}3{\times}10^8$ yrs) during which period most of the halo stars $({\sim}95%)$ are formed and a later slow collapse phase which is characterized by the chemical enrichment due to the inflow of external matter to the halo. (iii) The disk evolution is also divided into two phases, an active disk formation phase with a time-dependent initial mass function (IMF) up to $t{\approx}6{\times}10^9$ yrs and a later steady slow formation phase with a constant IMF. It is found that at the very early time $t{\approx}5{\times}10^8$ yrs, the metal abundance in the disk is rapidly increased to ${\sim}1/3$ of the present value but the total stellar mass only to ${\sim}10%$ of the present value, finally reaching about 80% of the present values toward the end of the active formation phase.

• Journal of Astronomy and Space Sciences
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• 제39권4호
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• pp.169-180
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• 2022

We investigated the chemical composition of the planetary host halo star HD47536 via high-resolution spectral observations recorded using a 1.5 meter Cerro Tololo Inter-American Observatory (CTIO) telescope (Chile). Furthermore, we determined the abundances of 38 chemical elements. Both light and heavy elements were overabundant compared to the iron group elements. The abundance pattern of HD47536 was similar to that of halo-type stars, with an enrichment of heavy elements. We analyzed the relationships between the relative abundances of chemical elements and their second ionization potentials and condensation temperatures. We demonstrated that the interplay of charge-exchange reactions owing to the accretion of interstellar matter and the gas-dust separation mechanism can influence the initial abundances and can be used to qualitatively explain the abundance patterns in the atmosphere of HD47536.

• 천문학회지
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• 제13권1호
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• pp.15-26
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• 1980

The BV-photographic photometry was made for 1714 stars (V<19.5) in NGC 6752. The C-M diagram of this cluster shows an unusually extended blue horizontal branch $(V=13.5{\sim}17.8)$ with a wide gap $(V=16{\sim}16.7)$ and the well defined giant branch with gaps at V=13.85 and 16.2. The turnoff point is defined at $V=17.25{\pm}0.15$ and (B-V) = $0.46{\pm}0.02$. If we take $V_{HB}=13.85$ for NGC 6752, then ${\Delta}V=2.80,\;(B-V)_{0,g}=0.76\;and\;{\Delta}V_{TO}=3.40$ and the chemical abundance is estimated to be [Fe/H]=-1.67 or $Z=4.3{\times}10^{-4}\;and\;Y=0.26$. Some other physical parameters of this cluster are derived and compared with those for the well observed clusters M 3, M 13, M 15 and M 92.

• 환경생물
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• 제36권4호
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• pp.471-478
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• 2018

식품생산과정에서 발생하는 유기성폐기물인 골분, 유박, 굴 패화석을 토양에 투입한 결과 일부 처리구에서 토양생물과 화학성이 영향을 받았다. 골분은 토양의 질산태질소를 일시적으로 증가시켰고, 패화석은 pH를 증가시켰다. 골분은 느티나무 생장을 증진시키는 효과가 있었기 때문에 이차적으로 토양생태계에 영향을 미칠 수 있다. 미생물 PLFA는 패화석에 의해 증가하였으며 환경스트레스를 나타내는 지표도 낮은 경향이 있었다. 이것은 패화석이 양분 증가보다는 pH 증가를 통해 미생물의 서식환경을 개선하는 효과가 있다는 것을 보여준다. 토양미소동물 중에는 세균섭식성 선충만이 유박과 골분 처리구에서 증가하였다. 이들 밀도와 세균 PLFA 간에 상관관계는 없었다. 다만 식물생장과 식물섭식성선충의 유의적 상관관계는 유기물투입이 식물을 통해 이차적으로 토양생태계에 영향을 줄 수 있다는 것을 부분적으로 보여준다. 따라서 유기성폐기물 처리는 토양화학성 변화를 통해 일차적으로 미생물 군집에 영향을 주지만, 미생물을 섭식하는 생물군에게 상향식의 양적인 연쇄반응을 일으키지 않을 수 있다는 것을 시사한다.