• Journal of The Korean Astronomical Society
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• v.44 no.5
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• pp.195-200
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• 2011

We have revisited the ACS Virgo Cluster Survey (ACSVCS), a Hubble Space Telescope program to obtain ACS/WFC g and z bands imaging for a sample of 100 early-type galaxies in the Virgo Cluster. In this study, we examine 51 nucleated early-type galaxies in the ACSVCS in order to look into the relationship between the photometric and structural properties of stellar nuclei and their host galaxies. We morphologically dissect galaxies into five classes. We note that (1) the stellar nuclei of dwarf early-type galaxies (dS0, dE, and dE,N) are generally fainter and bluer with g > 18.95 and (g-z) < 1.40 compared to some brighter and redder counterparts of the ellipticals (E) and lenticular galaxies (S0), (2) the g-band half-light radii of stellar nuclei of all dwarf early-type galaxies (dS0, dE, and dE,N) are smaller than 20 pc and their average is about 4 pc, and (3) the colors of red stellar nuclei with (g - z) > 1.40 in bright ellipticals and lenticular galaxies are bluer than their host galaxies colors. We also show that most of the unusually "red" stellar nuclei with (g-z) > 1.54 in the ACSVCS are the central parts of bright ellipticals and lenticular galaxies. Furthermore, we present multi photometric band color - color plots that can be used to break the age-metallicity degeneracy particularly by inclusion of the thermally pulsing-asymptotic giant branch (TP-AGB) phases of stellar evolution in the stellar population models.

• ALGAE
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• v.35 no.4
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• pp.389-404
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• 2020

Red algal fertilization is unusual and offers a different model to the mechanism of intracellular transport of nuclei and polyspermy blocking. A female carpogonium (egg) undergoes plasmogamy with many spermatia (sperm) simultaneously at the receptive structure, trichogyne, which often contains numerous male nuclei. The pattern of selective transport of a male nucleus to the female nucleus, located in the cell body of the carpogonium, remain largely unknown. We tracked the movement of spermatial nuclei and cell organelles in the trichogyne after plasmogamy using time-lapse videography and fluorescent probes. The fertilization process of Bostrychia moritziana is composed of five distinctive stages: 1) gamete-gamete binding; 2) mitosis in the attached spermatia; 3) formation of a fertilization channel; 4) migration of spermatial nuclei into the trichogyne; and 5) cutting off of the trichogyne cytoplasm from the rest of the cell after karyogamy. Our results showed that actin microfilaments were involved in the above steps of fertilization, microtubules are involved only in spermatial mitosis. Time-lapse videography showed that the first ("primary") nucleus which entered to trichogyne moved quickly to the base of carpogonium and fused with the female nucleus. The transport of the primary male nucleus to the egg nucleus was complete before its second nucleus migrated into the trichogyne. Male nuclei from other spermatia stopped directional movement soon after the first one entered the carpogonial base and oscillated near where they entered trichogyne. The cytoplasm of the trichogyne was cut off at a narrow neck connecting the trichogyne and carpogonial base after gamete nuclear fusion but gamete binding and plasmogamy continued on the trichogyne. Spermatial organelles, including mitochondria, entered the trichogyne together with the nuclei but did not show any directional movement and remained close to where they entered. These results suggest that polyspermy blocking in B. moritziana is achieved by the selective and rapid transport of the first nucleus entered trichogyne and the rupture of the trichogyne after gamete karyogamy.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.59.1-59.1
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• 2011

I present an analysis of the long-term evolution of the fluxes of six active galactic nuclei (AGN) - 0923+392, 3C 111, 3C 273, 3C 345, 3C 454.3, and 3C 84 - in the frequency range 80 - 267 GHz using archival calibration data of the IRAM Plateau de Bure Interferometer. Our dataset spans a long timeline of ~14 years with 974 - 3027 flux measurements per source. We find strong (factors ~2-8) flux variability on timescales of years for all sources. The flux density distributions of five out of six sources show clear signatures of bi- or even multimodality. Our sources show mostly steep (alpha~0.5-1), variable spectral indices that indicate outflow dominated emission; the variability is most probably due to optical depth variations. The power spectra globally correspond to red-noise spectra with five sources being located between the cases of white and flicker noise and one source (3C 111) being closer to the case of random walk noise. For three sources the low-frequency ends of their power spectra appear to be upscaled in spectral power by factors ~2-3 with respect to the overall powerlaws. We conclude that the source emission cannot be described by uniform stochastic emission processes; instead, a distinction of "quiescent" and (maybe multiple) "flare" states of the source emission appears to be necessary.

• The Korean Journal of Cytopathology
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• v.7 no.1
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• pp.44-50
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• 1996

Small cell carcinoma of the lung is characterized by cells with finely stippled chromatin and scanty cytoplasm as well as a particularly aggressive clinical course and favorable response to the chemotherapy. Recently percutaneous fine needle aspiration (FNA) biopsy has become both widely established and highly respected for the diagnosis of lung cancer. However metastatic small cell carcinoma of lymph node should be cytologically differentiated from the small round cell tumor of particular sites, especially malignant lymphoma, because small ceil carcinoma of classic oat cell type nay simulate small cell non-Hodgkin's lymphoma. We report five cases of metastatic small cell carcinoma of in-termediate cell type diagnosed by FNA of the enlarged lymph nodes of the neck and axilla. The cytologic smears contained diffuse small neoplastic cells larger than lymphocytes with dense, pyknotic nuclei and extremely scanty cytoplasm. Apparently viable large tumor cells have vesicular nuclei with granular, sometimes very coarse chromatin. The characteristic cytologic features of small cell carcinoma as compared to malignant lymphoma were as follows.: 1) small cells with dense pyknotic nuclei are evenly distributed in the background of apparently viable larger tumor cells, admixed with mature lymphocytes and phagocytic macrophages. 2) small loose aggregates of cells with nuclear melding are indicative of small cell carcinoma rather than non-Hodgkin's lymphoma. 3) the cytoplasmic and nuclear fragments of tumor necrosis are more dominant in the smears of small cell carcinoma. 4) nuclear membrane and nucleoli are generally indistinct in small cell carcinoma due to condensation of chromatin.

• Korean Journal of Veterinary Research
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• v.39 no.6
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• pp.1057-1065
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• 1999

The study was designated to investigate the electron microscopic findings following diethylnitrosamine (DEN) treatment in rats. Forty four male (Srague Dawley) rats were continuously given water containing 0.01% DEN for 13 weeks and livers of five rats with more tumor lesions at 16 and 17 weeks after initial treatment were used as EM materials. In transmission electron microscopic findings, most small-sized hepatocytes were active cells containing large mount of organelles, but light (pale staining) hepatocytes among small-sized hepatocytes were injured cells containg disorganized organelles. Tumor cells among small-sized hepatocytes were irregularly arranged and have pleomorphic nuclei containing electron dense chromatin but the organelles in cytoplasm were swelled. Large-sized hepatocytes were active cells with condensed chromatin but the cytoplasm of these cells were pale due to be injured and dilated organelles. Dark hepatocytes were apoptotic cells with homogenous pyknotic nuclei and cytoplasm, and the cytoplasm of these cells contained dilated smooth endoplasmic reticulum (sER) but these sER were non-vesiculated. Cholangiocarninoma cells were crowded and were pale by far less number of organelles in cytoplasm and nuclei. In scanning electron microscopic findings, the lumens of portal veins, bile canaliculi, bile ductules, bile ducts and sinusoids were dilated and have irregular folded inner surface by protruded parenchyma.

• The Korean Journal of Cytopathology
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• v.12 no.2
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• pp.105-110
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• 2001

Chordoma is a rare, clinically and morphologically well characterized tumor, which arises from remnants of the notochord, The majority(60%) occurs in the sacrococcygeal region, with 25% in the clival legion, and 15% in the spine. Although most chordomas do not develop metastasis, the long term prognosis is very poor due to local progressive tumor growth and tendency to recur if incompletely excised. The chordoma has characteristic cytologic features which make a preoperative diagnosis possible. We reviewed the cytologic findings of five patients with chordoma(one oropharynx, two clivus, and two sacrum). The patients were three male and two female, aged from 29 to 77 years(mean 60). Of five chordomas, there were local recurrences in two cases and metastasis of lymph node In one case. Four were FNA smears and one was squash smear taken from intraoperative consultation. All five cases show similar cytologic features. The dominating tumor cells were large with round nuclei and pale-stained vacuolated cytoplasm. The small round uniform cells and short spindle-shaped cells were frequently noted. The cells were surrounded by myxoid or mucoid matrix. The chordoma has characteristic cytologic features which make a preoperative diagnosis possible.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.73.1-73.1
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• 2017

Reverberation mapping is one of the best way to investigate structure and kinematics of broad-line regions around central supermassive black holes of active galactic nuclei (AGN). It is usually used to estimate masses of supermassive black holes. So far, reverberation mapping studies have achieved good results for dozens of AGN by spectroscopic monitoring. However, spectroscopic monitoring is time consuming and high cost. Here, we present result of photometric reverberation mapping with medium-band observation. We monitored five nearby AGN which are already studied, have short time-lag, and show bright H-alpha emission lines. Observation has been performed for ~3 months with ~3 days cadence using three medium-band filters installed in LSGT (Lee Sang Gak Telescope). We found 0.01-0.06 magnitude variations by differential photometry. Also time-lags between continuum light-curves and H-alpha emission line light-curves are calculated using Javelin software. The result shows that our study and previous studies are consistent within uncertainty range. From verification of availability in this study, photometric reverberation mapping could be used as a powerful tool to measure central supermassive black holes for large samples and high-redshift AGN in the future.

• Journal of The Korean Astronomical Society
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• v.22 no.1
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• pp.1-24
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• 1989

By applying population synthesis method, stellar populations in the nuclei of M31 and M32 are studied. We obtained five and four models for M31 and M32 respectively, for different main sequence turn-offs and keeping the astrophysical constraints as loose as possible. The best models for M31 and M32 are thought to have G0-5 and F5-8 main sequence trun-offs respectively. These models show that the main sequence stars outnumber the giants, which indicates the dwarf-dominance in external galactic nuclei. Even though there are some computational difficulties because of non-uniqueness in solution, two major points can be pointed out when compared to the previous papers. First, the ultraviolet deficiency expected from the conventional metal rich population models is not detected in our models, Instead ultraviolet radiation turns out to be somewhat higher than that of observation. Second one is the minor contribution from the Super Metal Rich (SMR) K giants to the integrated light of the program galaxies. That is, in our models, the SMR contribution is at best the same level as normal giants contrary to the SMR dominance of previous models. Since the loose astrophysical constraints are the major difference of our study from the previous ones, one should re-examine carefully for their validity further.

• The Korean Journal of Cytopathology
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• v.2 no.1
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• pp.1-7
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• 1991

Cytologic findings from five cases with variable types of Hodgkln's disease were reviewed with special emphasis on the Reed-Sternberg (R-S) cells and their variants. Typical R-S and Hodgkin's cells were mono- or binucleated, and nuclei had rounded smooth contour, Acidophilic prominent nucleoli with perinucleolar halo were conspicuous in comparison to typical Reed-Sternberg cells, L & H (lymphocytic and histiocytic) cells in the lymphocyte predominant type tended to show pop-corn like irregular nuclear contour and to lack the prominent nucleoli. Lacunar cells in the nodular sclerosis type had multilobated nuclei with prominent acidophilic nucleoli. There was no prominent perinucleolar halo in L & H and lacunar cells. In conjuction with the number of Reed-Sternberg cells and back ground findings observed on the smears, the characteristic features of R-S cells and their variants allowed to make typing of Hodgkin's disease.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.35 no.6
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• pp.402-407
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• 2013

Schwannomas originate from the Schwann cells in the neural sheath of the peripheral nerves. Ancient schwannoma is one of five variants, and its characteristics include histopathological degeneration and diffuse hypocellular areas. Histopathological features show degenerative changes and atypical nuclei can easily be confused with malignant neoplasms. These cellular atypisms are caused solely by degenerative changes. Ancient schwannomas have been reported 17 cases of in the oral cavity and five cases in the ventral tongue, including the floor of the mouth. We report a new case of an ancient schwannoma, misdiagnosed as a hemangioma with a 10-year evolution, located in the ventral tongue of a 29-year-old female.