• The Bulletin of The Korean Astronomical Society
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• v.19
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• pp.15.1-15.1
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• 1994

• The Plant Pathology Journal
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• v.21 no.2
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• pp.132-136
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• 2005

Two groups of phytoplasma were identified in chrysanthemum(Dendranthema grandiflorum) cv. Chunkwang showing distinct symptoms. Isolate Ph-ch1 showed symptoms of dwarf, witches'-broom, rosette and root death. The other isolate, Ph-ch2, revealed symptoms of dwarf, yellowing, leaf cupping, vein clearing and root death. The presence of phytoplasma structures in chrysanthemum leaf tissue was confirmed by transmission electron microscopy. The 16S rRNA gene was amplified from isolates Ph-ch1 and Ph-ch2 by PCR and cloned, and the nucleotide sequences were determined. In RFLP analysis, isolate Ph-ch2 showed profiles identical to Ph-ch1, except with restriction enzymes HhaI and MseI. The sequence data showed that isolate Ph-ch1 was most closely related to the aster yellows (AY) phytoplasma, and isolate Ph-ch2 was more closely related to stolbur phytoplasma than to AY phytoplasma. This is the first reported observation of stolbur phytoplasma in chrysanthemum species.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.89.1-89.1
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• 2015

Period changes found in the 10 years CCD BVR photometry data (2005 - 2014) of the Intermediate Polar MU Cam will be discussed. The timings of extrema of the data are determined and the new ephemeris for the spin period and orbital period have been calculated by using multi-periodic approximation as follows: BJD(orb)=2454085.46(19)+0.19664 $10(26){\cdot}E$ and BJD(spin)=2454085.50725(91)+0.013740942(13) ${\cdot}$ $E-1.51(10){\times}10^{-12}{\cdot}E^2$. The O-C diagram shows an increasing of the spin period as $P=-2.20(14){\cdot}10^{-12}s/s$. It is also found in MU Cam that the white dwarf's rotation seems to be switched from a state of spin-down to spin-up by the white dwarf's equilibrium spin period in 2005.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.50.1-50.1
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• 2013

Blue Compact Dwarf galaxies (BCDs) are systems which have been experiencing the bursts of star formation in their central region. As one of the origins of active star formation, tidal interaction (merger or fly-by between dwarf galaxies) has been suggested. A pair of BCDs, ESO 435-IG20 and ESO 435-IG16, are suspected to be a good example of such case. They are located at a similar redshift and separated only by ~130 kpc at their distances. In addition a bridge-like HI structure has been found between these two BCDs in the HIPASS survey. In this study, using the ATCA HI data of a much better resolution, we probe the gas morphology and kinematics of individual galaxies. We discuss how tidal interaction is responsible for the high star formation rate in this BCD pair.

• The Plant Pathology Journal
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• v.23 no.2
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• pp.106-108
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• 2007

The Symptoms of witches' broom disease caused by phytoplasma including general stunting and yellowing, were observed in leafy lespedeza (Lespedeza cyrtobotrya M.) on Doam-myeon, Pyeongchang-gun, in 2006. Based on the sequence analysis of PCR-amplified 16S ribosomal DNA and 16S-23S spacer region DNA products using universal phytoplasma primers, the phytoplasma associated with leafy lespedeza witches' broom (LLWB) disease was identified as a member of Candidatus Pytoplasma trifolii. It was most closely related to alsike clover proliferation phytoplasma (99.8% similarity, accession no. AY390261), Candidatus Pytoplasma trifolii strain. RFLP patterns generated with AluI, HpaII clearly differentiated LLWB phytoplasma from the referenced phytoplasma strains, water dropwort witches' broom, mulberry dwarf, glehni aster yellow dwarf and jujube witches' broom. This paper is the first report on Candidatus Phytoplasma trifolii in leafy lespedeza identified at a molecular level.

• Journal of Plant Biology
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• v.39 no.3
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• pp.215-221
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• 1996

Sorghum leaf tissues showing the early acute response of systemic infection with maize dwarf mosaic virus (MDMV) strain A, contained unusual virus-induced cytological modifications including cell wall thickenings and protrusions, intercellular vesicles termed as "paramural bodies", modified plasmodesmata, abnormal plastids, and cylindrical inclusion bodies. Abnormal cell wall, some of which associated with paramural bodies, was frequently contained modified plasmodesmata. Various abnormal plastids were located within infected cells of leaf tissues showing the early acute response. The most important changes in chloroplast seen in the tissues are the presence of small vesicles, deformation of membranes, reduction in granal stack height, disappearance of osmiophilic globules and degeneration of stuctures. The cytological modification was not occurred in nucleus but a group of degenerated mitochondria with abnormal membranes attached to cylindrical inclusion bodies were observed. It was hard more or less to prove the relationship clearly between virus and cellular organelles in virus replication.plication.

• Journal of Astronomy and Space Sciences
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• v.2 no.1
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• pp.7-18
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• 1985

We have constructed models of steady accretion disk with accretion rate M=$10^{16}g/sec$ or $10^{18}g/sec$. The mass of the radius of white dwarf were taken as $1M_\odot$ and $10^9cm$, respectively. The possible application of the results to Z Cha and Z Cam are discussed.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.78-78
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• 2003

Dwarf galaxies are the most common type of galaxy in the universe and believed to be basic building blocks of the large scale structures. In order to understand the formation history of these galaxies, we selected two well-observed galaxies in the Local Group and constructed the stellar population models including HB stars. We employed Y$^2$ Isochrones (Yi et al. 2001) and HB tracks (Yi et al. 1997) for stellar population synthesis. Our models show that (1) the Carina dSph has several distinct populations with age of ∼10.5, 5.8, 4.1, 2.8 and 1.0 Gyrs, and (2) stellar populations of the Sextans dSph are constructed in terms of the two populations with age of ∼ 11 and ∼2.5 Gyrs. Observational data were kindly provided by Lee et al. (2003, in preparation) and Monelli et al. (2003) for Sextans and Carina dsphs, respectively.

• Journal of Astronomy and Space Sciences
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• v.12 no.1
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• pp.1-13
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• 1995

We carried out photometric and spectroscopic observatious of the blue compact dwarf galaxy Haro 6 in the Virgo Cluster of Galaxies. The long-slit spectroscopy was employed at three position angles, $\Phi$=$0^{\circ}$, $\Phi$=$30^{\circ}$, and $\Phi$=$120^{\circ}$with CCD camera mounted on the Cassegrain Spectrograph. Based on the mean intrinsic axial ratio < $q_0$ >=0.3, we derived inclination I of the system as $44^{\circ}$using our composite V-band CCD image. Careful analysis on the velocity field of the system shows an asymptotically fiat rotation curve with the maximum rotational velocity $V(r)_{max}$ reaches about 12km/sec. The calculation of the dynamical mass of Haro 6 with a simple mass model is briefly discussed with emphasis on the mass to luminosity ratio. From the IRAS Point Source Cataloque, we derived dust-to-gas ratio which indicates relatively low dust content, thus tempting us to conjecture the youth of the system.

• Korean journal of applied entomology
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• v.16 no.2 s.31
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• pp.121-125
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• 1977

This is the first report on. rice black-streaked dwarf virus in Korea. The occurrence of this virus in Korea was confirmed by symptoms On rice Plants, Vector transmission and microscopic Observation in 1975. The smaller brown planthopper, Laodelphax striatellus FALLEN, transmits this virus which is spherical with a diameter of about 60 nm. Higher infection was observed in earlier transplanted rice with higher levels of fertilizer than in normal and standard cultivation fields.