• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.62.1-62.1
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• 2015

Polarization of the light reflected off the Moon provides information on the size and composition of the particles in the lunar regolith. The mean particle size of the regolith can be estimated from the combination of the albedo and degree of polarization, while the color ratio of the parallel-component polarization (CP) has been suggested to be related to the amount of nanophase metallic iron (npFe^0) inside the regolith particles. Both the mean size and npFe^0 abundance of the particles have been used as maturity indicators of the regolith since sustained impacts of high energy particles and micro-meteoroids cause comminution of particles and production of npFe^0. Based on our multispectral polarimetric observations of the whole near side of the Moon in the U, B, V, R, and I bands, we compare the maps of the mean particle size, CP, and the optical maturity (OM). We find that the mean particle size map is sensitive to the most immature (~0.1 Gyr) soil, the OP map to the intermediate immaturity (a few 0.1 Gyr) soil, and the CP map to the least immature (~1 Gyr) soil.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.29.1-29.1
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• 2021

There have been many studies aiming to reveal the origins of the star-gas misalignment found in galaxies, but there still is a lack of understanding of the contribution from each formation channel candidate. We explore the properties, origins, and lifetimes of the star-gas misalignment using Horizon-AGN, a large-volume cosmological simulation. First, the misalignment fraction shows a strong anti-correlation with the kinematic morphology (V/sigma) and the cold gas fraction of the galaxy. This result is consistent with the result of integral field spectroscopy observations. Second, we have identified four main formation channels of misalignment and quantified their level of contribution: mergers (35%), interaction with nearby galaxies (23%), interaction with dense environments or their central galaxies (21%), and secular evolution including smooth accretion from neighboring filaments (21%). Third, the decay timescale of the misalignment is strongly linked with the kinematic morphology of the galaxy: early-type galaxies (2.28 Gyr) tend to have a longer misalignment lifetime than LTGs (0.49 Gyr). We also found that the morphology and cold gas fraction are both and independently anti-correlated with the misalignment lifetime.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.53.3-54
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• 2016

We combine a semi-analytic model of galaxy evolution with constraints on circumstellar habitable zones and the distribution of terrestrial planets in order to probe the suitability of galaxies of different mass and type to host habitable planets, and how it evolves with time. We find that the fraction of stars with terrestrial planets in their habitable zone (known as habitability) depends only weakly on galaxy mass, with a maximum around $4{\times}10^{10}M_{\odot}$. We estimate that 0.7% of all stars in Milky Way-type galaxies to host a terrestrial planet within their habitable zone, consistent with the value derived from Kepler observations. On the other hand, the habitability of passive galaxies is slightly but systematically higher, unless we assume an unrealistically high sensitivity of planets to supernovae. We find that the overall habitability of galaxies has not changed significantly in the last ~8 Gyr, with most of the habitable planets in local disk galaxies having formed ~1.5 Gyr before our own solar system. Finally, we expect that ${\sim}1.4{\times}10^9$ planets similar to present-day Earth have existed so far in our galaxy.

• Journal of Microbiology
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• v.45 no.2
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• pp.168-170
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• 2007

In this research 26 Shigella isolates were examined by PCR and direct nucleotide sequencing for genetic alterations in the quinolone-resistance determining regions (QRDRs). We tested for the presence of qnr genes by PCR in 91 strains, but no qnr genes were found. The results did show, however, some novel mutations at codon 83 of gyrA ($Ser{\rightarrow}Ile$) and codon 64 of parC ($Ala64{\rightarrow}Cys,\;Ala64{\rightarrow}Asp$), which were related to fluroquinolone resistance.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.4
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• pp.427-434
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• 2017

Species that belong to the Acinetobacter calcoaceticus-baumannii (Acb) complex are major causes of hospital-acquired infections. They are important opportunistic pathogens. These species are usually multidrug resistant (MDR), and the therapeutic options to treat the infections caused by these species are limited. In the present study, we investigated fluoroquinolone resistance mechanisms in 53 ciprofloxacin resistant Acinetobacter species isolates in Chungcheong, Korea. Antimicrobial susceptibilities were determined using the disk-diffusion method. Detections of genes and identification of mutations associated with fluoroquinolone resistance were carried out using PCR and DNA sequencing. In our study, 47 out of 53 ciprofloxacin resistant Acinetobacter isolates harbored sense mutations at the 83rd residue (serine to leucine) in the gyrA gene as well as at the 80th residue (serine to leucine) in the parC gene. Among the 47 isolates harboring sense mutations in gyrA and parC gene, 44 isolates were A. baumannii and 3 isolates were A. pittii. Plasmid-mediated quinolone resistance (PMQR) determinants were detected in isolates in our study. Among the 46 ciprofloxacin resistant A. baumannii isolates, 41 showed type A, B, or F banding patterns on their REP-PCR profiles. This result suggests that clonal relation and horizontal spreading of the bacterial isolates have been around hospitals in Chungcheong area. To prevent colonization and disseminations of fluoroquinolone resistance Acb complex isolates, continuous investigation and monitoring of antimicrobial resistant determinants of MDR isolates are needed.

• Journal of fish pathology
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• v.30 no.2
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• pp.79-88
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• 2017

At the present, fish farms are suffering a lot of economic losses due to infectious diseases caused by various pathogens including aeromonad. Aeromonad is ubiquitous bacteria that causes infectious diseases. At least 26 species in the genus Aeromonas have been reported to cause fatal infections not only in salmonid fishes, but also in other freshwater and seawater fishes. Molecular techniques based on nucleic acid sequences of 16S rDNA and housekeeping genes can be used to identify the Aeromonas species. In this study, The genus Aeromonas was isolated from salmonid fishes of sixteen fish farms in Gangwon-Do, Korea and phylogenetically identified based on the sequences of 16S rDNA and housekeeping genes for Aeromonad, i.e. RNA polymerase sigma factor ${\sigma}^{70}$ (rpoD) or DNA gyrase subunit B (gyrB). Consequently, 96 strains were collected from Atlantic salmon (Salmo salar), coho salmon (Oncorhynchus kisutch), masou salmon (Oncorhynchus masou) and rainbow trout (Oncorhynchus mykiss), and 36 isolates were identified as the genus Aeromonas by 16S rDNA analysis. Thirty six Aeromonad isolates were further analysed based on rpoD or gyrB gene sequences and found Aeromonas salmonicida (24 isolates), A. sobria (10 isolates), A. media (1 isolates) and A. popoffii (1 isolates), indicating that A. salmonicida is a main infectious bacteria in Salmonid fishes in Gangwon-Do. It was also proved that the phylogenetic identification of Aeromonas species based on the sequences of housekeeping gene is more precise than the 16S rDNA sequence.

• Journal of Animal Reproduction and Biotechnology
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• v.37 no.3
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• pp.193-201
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• 2022

Subgroups of sperm which share similar motility features documented in mammals indicate between-subject variations that might be related to fertilizing potential of the respective ejaculates. The objectives of this study were to define subpopulations of motile sperm in Gyr falcon semen using kinematic parameters driven by Computer Assisted Semen Analysis (CASA) and to investigate the subject-related variations in these subpopulations. A total of 24 fresh ejaculates from 6 falcons were used to assign each of the 20473 sperms into 3 subpopulations by a multivariate cluster analysis. The proportion of sperms in different sub-populations were compared among subjects by a generalized linear model and repeatability of sperm frequency in different subpopulations was investigated by corelation analysis. The resulting 3 categories of sperm indicated significant differences in all kinematic parameters (p < 0.05). Subpopulation 1 (15.91%) contained sperms with the highest velocity and progressiveness of movement trajectory while subpopulation 3 (6.4%) included the least progressively motile sperms. Proportion of rapid and medium progressive sperm were consistently higher in the ejaculate of three falcons compared to the two other birds which also had the highest proportion of slow non-progressive sperms (p < 0.05). Respective proportion of sperms in each subpopulations indicated significant repeatability over multiple measurements (p < 0.05). In conclusion, subpopulations of motile sperm in Gyr falcon can be identified using kinematic parameters generated by CASA. Individual differences in the proportion of these subpopulations might have potential application for identifying the males with higher fertilizing capacity.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.959-966
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• 2004

Twenty-three cultures of harmful algal bloom (HAB)-(causing dinoflagellates were isolated from the coastal waters of Korea. For each of the 14 morphospecies, the nuclearencoded small subunit (SSU) rDNA was analyzed to determine the phylogenetic relatedness of the species. Despite temporal and spatial isolation, 3-4 clonal cultures of Alexandrium catenella, Cochlodinium polykrikoides, and Gymnodinium catenatum had 100% identical SSU rDNA sequences. In contrast, heterogeneities in the SSU rDNA sequences were observed in Akashiwo sanguinea and Lingulodinium polyedrum strains. Extreme sequence polymorphism was shown within the SSU rRNA genes of an Al. tamarense clonal culture. A homology search in GenBank revealed that 11 dinoflagellate species were located in clusters corresponding to their morphological classification. The SSU rDNA sequences of C. polykrikoides, Gyrodinium instriatum, and Pheopolykrikos hartmannii, which were determined for the first time in this study, showed the following phylogenetic relationships: C. polykrikoides formed an independent branch separated from other dinoflagellates; Gyr. instriatum was placed in a monophyletic group with Gyr. dorsum and Gyr. uncatenum; and Ph. hartmanii, which forms a distinct two-celled pseudocolony, belonged to Gymnodinium sensu Hansen and Moestrup.

• Journal of the Korean earth science society
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• v.27 no.5
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• pp.557-568
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• 2006

We present CCD UBVI photometry for more than 10,000 stars in $20'.5{\times}20'.5$ field of the halo globular cluster M30. From a color-magnitude diagram, main sequence turnoff was obtained when $V_{TO},\;(B-V)_{TO},\;and\;(V-I)_{TO}\;are\;8.63{\pm}0.05,\;0.44{\pm}0.05\;and\;0.63{\pm}0.05$, respectively. From a (U-B)-(B-V) diagram, reddening parameter, E(B-V) equals $0.05{\pm}0.01$ and a UV color excess ${\delta}(U-B)\;is\;0.27{\pm}0.01$. The abundance is derived, where [Fe/H] equals $-2.05{\pm}0.09$ according to the photometric method and spectroscopic data. The observed luminosity function of M30 shows an excess in the number of red giants relative to the number of turnoff stars, when comparing with the predictions of canonical models. Using the Hipparcos parallaxes for subdwarfs, we estimate distance modulus, $(m-M)_o\;as\;14.75{\pm}0.12$. Using the R and R' method, we find helium abundances, Y(R) as $0.23{\pm}0.02$, Y(R') as $0.29{\pm}0.02$, respectively. Finally, the cluster' sage dispersion was deduced from 10.71 Gyr to 17 Gyr.

• Journal of Microbiology
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• v.44 no.6
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• pp.591-599
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• 2006

To address the diversity of cyclodextrin-producing P. graminis strains isolated from wheat roots and rhizospheres of maize and sorghum sown in Australia, Brazil, and France, restriction fragment length polymorphism analysis of part of genes encoding RNA polymerase (rpoB-RFLP) and DNA gyrase subunit B (gyrB-RFLP) was used to produce genetic fingerprints. A phylogenetic tree based on rpoB gene sequences was also constructed. The isolates originated from Brazil could be separated from those from Australia and France, when data from the rpoB-based phylogenetic tree or gyrB-RFLP were considered. These analyses also allowed the separation of all P. graminis strains studied here into four clusters; one group formed by the strains GJK201 and $RSA19^T$, second group formed by the strains MC22.02 and MC04.21, third group formed by the strains TOD61, TOD 221, TOD302, and TOD111, and forth group formed by all strains isolated from plants sown in Cerrado soil, Brazil. As this last group was formed by strains isolated from sorghum and maize sown in the same soil (Cerrado) in Brazil, our results suggest that the diversity of these P. graminis strains is more affected by the soil type than the plant from where they have been isolated.