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Search Results: 1 - 10 of 8817 matches for " Soon-Wook; Park "
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Development of cDNA-derived SSR markers and their efficiency in diversity assessment of Cymbidium accessions
Moe,Kyaw Thu; Hong,Woo-Ju; Kwon,Soon-Wook; Park,Yong-Jin;
Electronic Journal of Biotechnology , 2012,
Abstract: cymbidium spp. are popular ?owering plants. assessment of the genetic diversity in cultivated cymbidium facilitates conservation of germplasm and subsequent cultivar improvement. thus, it is important to develop more efficient polymorphic dna markers. although more motifs (403) were identified and more primers (206) were designed in the genomic library compared to the cdna library, a larger number of successful primers were obtained from the cdna library (59.9%) than from genomic dna library (51.1%). however, higher pic and gene diversity were identified in genomic ssrs. the average allele number per locus was also higher in genomic ssrs (7.3) than est-ssrs (5.2), among the 24 evaluated cymbidium accessions. at/ta was comparatively high in est-ssrs, while this motif was not as common in genomic ssrs. the ctt/aag/tct/aga/ttc/gaa and tgc/gca/gct/agc/ctg/cag motifs were the most abundant tri-nucleotide sequences in est-ssrs, while gtt/aac/tgt/aca/ttg/caa was the most frequent in genomic ssrs. the number of repeats ranged from 3 to 12 in est-ssrs. currently, 52 novel polymorphic ssr markers have been evaluated, which will be useful for germplasm assessments, core set construction, evaluation of genetic diversity, and marker assisted selection (mas) based cymbidium breeding.
Comparison of Population Genetic Structures between Asian and American Mungbean Accessions Using SSR Markers
Xiao-Qiang Wang,Soon-Wook Kwon,Yong-Jin Park
Journal of Agricultural Science , 2012, DOI: 10.5539/jas.v4n9p150
Abstract: The purpose of this study was to evaluate the genetic diversity and population structure of 65 mungbean accessions collected from East and Southeast Asia, the United States and Guatemala using 15 simple sequence repeat (SSR) markers. In total, 47 alleles were detected, the number of the alleles per locus range from two to six, with an average of 3.13. The mean major allele frequency (MAF), expected heterozygosity (HE), and polymorphic information content (PIC) of the 15 SSR loci were 0.76, 0.05, and 0.28, respectively. Of the 47 alleles, 17 (36.2%) were common, with a frequency of 0.05– 0.5; 16 (34.0%) were rare (frequency < 0.05) and 14 (29.8%) were abundant (frequency > 0.5). On the basis of the UPGMA dendrogram, most of the accessions were clustered into two main groups. The first group (Group I) included seven accessions and the second comprised 58 accessions, which were further divided into four subgroups. Four subpopulations were detected by model-based structure analysis. Fifty-five accessions (84.6%) showed a clear relation to each cluster based on their inferred ancestry value (>75%), while the remaining 10 accessions (15.4%) were categorized as admixtures. Mungbean accessions from US distributed to almost all clusters and 2 accessions shared genetic constituents showing it derived from mixed ancestry with Asean accessions. These results could be useful in identifying mungbean germplasms and facilitating their improvement programs.
Current-Induced Magnetic Domain-Wall Motion by Spin Transfer Torque: Collective Coordinate Approach with Domain-Wall Width Variation
Soon-Wook Jung,Hyun-Woo Lee
Physics , 2007,
Abstract: The spin transfer torque generated by a spin-polarized current can induce the shift of the magnetic domain-wall position. In this work, we study theoretically the current-induced domain-wall motion by using the collective coordinate approach [Gen Tatara and Hiroshi Kohno, Phys. Rev. Lett. 92, 86601 (2004)]. The approach is extended to include not only the domain-wall position and the polarization angle changes but also the domain-wall width variation. It is demonstrated that the width variation affects the critical current.
Black-Hole X-Ray Transients: The Effect of Irradiation on Time-Dependent Accretion Disk Structure
Soon-Wook Kim,J. Craig Wheeler,Shin Mineshige
Physics , 1999, DOI: 10.1093/pasj/51.3.393
Abstract: Some effects of irradiation on time-dependent accretion-disk models for black hole X-ray novae are presented. Two types of irradiation are considered: direct irradiation from the inner hot disk and indirect irradiation as might be reflected by a corona or chromosphere above the disk. The shadowing effect of the time-dependent evolution of the disk height and consequent blocking of the outer disk by the inner and middle portions of the disk from the direct irradiation is included. The direct irradiation of the disk by inner layers where the soft X-ray flux is generated is found to have only a small effect on the outer disk because of shadowing. Mild indirect irradiation that flattens, but otherwise does not affect the light curve substantially, still has interesting non-linear effects on the structure of the disk as heating and cooling waves propagate. The irradiated disks do not always make simple transitions between the hot and cold states, but can linger at intermediate temperatures or even return temporarily to the hot state, depending on the irradiation and the activity in adjacent portions of the disk.
Spin-current-induced charge current
Soon-Wook Jung,Hyun-Woo Lee
Physics , 2005, DOI: 10.1103/PhysRevB.71.125341
Abstract: We show that the injection of a pure spin current (not accompanied by charge current) into a ring can induce a circulating charge current in the ring, provided that transport coefficients of the ring are spin-dependent and inhomogeneous. As an example, we consider a hybrid ferromagnet(F)-normal metal(N) ring system and calculate the magnitude of the charge current induced by the pure spin current injection. This phenomenon may have relevance for spintronic applications.
Interferometric Monitoring of Gamma-ray Bright Active Galactic Nuclei II: Frequency Phase Transfer
Juan-Carlos Algaba,Guang-Yao Zhao,Sang-Sung Lee,Do-Young Byun,Sin-Cheol Kang,Dae-Won Kim,Jae-Young Kim,Jeong-Sook Kim,Soon-Wook Kim,Motoki Kino,Atsushi Miyazaki,Jong-Ho Park,Sascha Trippe,Kiyoaki Wajima
Physics , 2015, DOI: 10.5303/JKAS.2015.48.5.237
Abstract: The Interferometric Monitoring of Gamma-ray Bright Active galactic nuclei (iMOGABA) program provides not only simultaneous multifrequency observations of bright gamma-ray detected active galactic nuclei (AGN), but also covers the highest Very Large Baseline Interferometry (VLBI) frequencies ever being systematically monitored, up to 129 GHz. However, observation and imaging of weak sources at the highest observed frequencies is very challenging. In the second paper in this series, we evaluate the viability of the frequency phase transfer technique to iMOGABA in order to obtain larger coherence time at the higher frequencies of this program (86 and 129 GHz) and image additional sources that were not detected using standard techniques. We find that this method is applicable to the iMOGABA program even under non-optimal weather conditions.
Current-induced domain wall motion in a nanowire with perpendicular magnetic anisotropy
Soon-Wook Jung,Woojin Kim,Taek-Dong Lee,Kyung-Jin Lee,Hyun-Woo Lee
Physics , 2008, DOI: 10.1063/1.2926664
Abstract: We study theoretically the current-induced magnetic domain wall motion in a metallic nanowire with perpendicular magnetic anisotropy. The anisotropy can reduce the critical current density of the domain wall motion. We explain the reduction mechanism and identify the maximal reduction conditions. This result facilitates both fundamental studies and device applications of the current- induced domain wall motion.
VLBI Observation of Microquasar Cyg X-3 during an X-ray State Transition from Soft to Hard in the 2007 May-June Flare
Jeong-Sook Kim,Soon-Wook Kim,Tomoharu Kurayama,Mareki Honma,Tetsuo Sasao,Sang Joon Kim
Physics , 2013, DOI: 10.1088/0004-637X/772/1/41
Abstract: We present a radio observation of microquasar Cyg X-3 during an X-ray state transition from ultrasoft to hard state in the 2007 May$-$June flare using the VLBI Exploration of Radio Astrometry (VERA) at 22 GHz. During the transition, a short-lived mini-flare of ${\lesssim}3$ hr was detected prior to the major flare. In such a transition, a jet ejection is believed to occur, but there have been no direct observations to support it. An analysis of Gaussian fits to the observed visibility amplitudes shows a time variation of the source axis, or a structural change, during the mini-flare. Our model fits, together with other multiwavelength observations in the radio, soft, and hard X-rays, and the shock-in-jet models for other flaring activities at GHz wavebands, suggest a high possibility of synchrotron flares during the mini-flare, indicative of a predominant contribution from jet activity. Therefore, the mini-flare with an associated structural change is indicative of a jet ejection event in the state transition from ultrasoft to hard state.
Evolution of the Water Maser Expanding Shell in W75N VLA 2
Jeong-Sook Kim,Soon-Wook Kim,Tomoharu Kurayama,Mareki Honma,Tesuo Sasao,Gabriele Surcis,Jorge Canto,Jose M. Torrelles,Sang Joon Kim
Physics , 2013, DOI: 10.1088/0004-637X/767/1/86
Abstract: We present Very Long Baseline Interferometry (VLBI) observations of 22 GHz H$_2$O masers in the high-mass star-forming region of \objectname{W75N}, carried out with VLBI Exploration of Radio Astrometry (VERA) for three-epochs in 2007 with an angular resolution of $\sim$ 1 mas. We detected H$_2$O maser emission toward the radio jet in VLA 1 and the expanding shell-like structure in VLA 2. We have made elliptical fits to the VLA 2 H$_2$O maser shell-like structure observed in the different epochs (1999, 2005, and 2007), and found that the shell is still expanding eight years after its discovery. From the difference in the size of the semi-major axes of the fitted ellipses in the epochs 1999 ($\simeq$ 71$\pm$1 mas), 2005 ($\simeq$ 97$\pm$3 mas), and 2007 ($\simeq$ 111$\pm$1 mas), we estimate an average expanding velocity of $\sim$ 5 mas yr$^{-1}$, similar to the proper motions measured in the individual H$_2$O maser features. A kinematic age of $\sim$ 20 yr is derived for this structure. In addition, our VERA observations indicate an increase in the ellipticity of the expanding shell around VLA 2 from epochs 1999 to 2007. In fact, the elliptical fit of the VERA data shows a ratio between the minor and major axes of $\sim$ 0.6, in contrast with a most circular shape for the shell detected in 1999 and 2005 (b/a $\sim$ 0.9). This suggests that we are probably observing the formation of a jet-driven H$_2$O maser structure in VLA2, evolving from a non-collimated pulsed-outflow event during the first stages of evolution of a massive young stellar object (YSO). This may support predictions made earlier by other authors on this issue, consistent with recent magnetohydrodynamical simulations. We discuss possible implications of our results in the study of the first stages of evolution of massive YSOs.
Monitoring of multi-frequency polarization of gamma-ray bright AGNs
Sang-Sung Lee,Myounghee Han,Sincheol Kang,Jungmin Seen,Do-Young Byun,Jun-Hyun Baek,Soon-Wook Kim,Jeong-Sook Kim
Physics , 2013, DOI: 10.1051/epjconf/20136107007
Abstract: We started two observing programs with the Korean VLBI Network (KVN) monitoring changes in the flux density and polarization of relativistic jets in gamma-ray bright AGNs simultaneously at 22, 43, 86, 129 GHz. One is a single-dish weekly-observing program in dual polarization with KVN 21-m diameter radio telescopes beginning in 2011 May. The other is a VLBI monthly-observing program with the three-element VLBI network at an angular resolution range of 1.0--9.2 mas beginning in 2012 December. The monitoring observations aim to study correlation of variability in gamma-ray with that in radio flux density and polarization of relativistic jets when they flare up. These observations enable us to study the origin of the gamma-ray flares of AGNs.
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