• Journal of The Korean Astronomical Society
• /
• v.29 no.spc1
• /
• pp.97-98
• /
• 1996

Variability of active galactic nuclei is now a well-known phenomenon. This remains to be fully explained by a theoretical model of the central engine. Time scales of AGN variability seem to range continuously from hours up to months. The short time scale variability must be related to the phenomena on the event horizon of the black hole, while the long one to those in the accretion disk or surrounding matter. Based on the axisymmetric, nonstationary model of the central engine, we discuss theoretical considerations on the variability of active galactic nucleus.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.1
• /
• pp.34.1-34.1
• /
• 2012

I present an analysis of the linear polarization of six active galactic nuclei (AGN). We monitored our targets from 2007 to 2011 in the observatory-frame frequency range 80-253 GHz with the Plateau de Bure Interferometer (PdBI). We find average degrees of polarization in the range 2-7%; this indicates that the polarization signals are effectively averaged out by the emitter geometries. We see indication for the presence of strong shocks and/or variability of the emitter geometries. We attempt to derive rotation measures for all sources, leading to actual measurements for two targets which find the highest rotation measures reported to date for AGN.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.2
• /
• pp.66.1-66.1
• /
• 2017

Nuclear reactions in explosive stars such as novae, X-ray bursts, and supernovae are responsible for producing many of the elements that make up our world. Exotic nuclei not normally found on earth can play an important role in these events due to the extreme conditions that occur in the explosion. A frontier area of research involves utilizing beams of radioactive nuclei to improve our understanding of these explosions and the implications on cosmic element production. At the future radioactive ion beam facility of Korea, RAON, we will measure astrophysically important reactions using exotic beams to probe the details of cosmic events. Details of RAON and possible day-1 experiments at the facility will be presented.

• The Korean Journal of Mycology
• /
• v.16 no.4
• /
• pp.210-213
• /
• 1988

Several reversion colonies were obtained after induced transfer of the isolated nuclei from P. sapidus into protoplast of P. ostreatus$({Arg}^-)$. These colonies showed three distinct cultural characteristics, type 1 produced spontaneous segregants of both parental types, type 2 showed segregants of non parental types, and type 3 gave rise to homogeneous colonies. Isozyme patterns of esterase, malate dehydrogenase and superoxide dismutase showed substantial differences between parents and nuclei transferred strains. This observation supported that the isolated nuclei of P. sapidus were transferred into protoplast of P. ostreatus and expressed in recipient cell.

• Journal of Microbiology and Biotechnology
• /
• v.4 no.3
• /
• pp.183-190
• /
• 1994

Cell-free extracts prepared from cultured insect cells, Spodoptera. frugiperda, were analyzed for activation of early gene transcription of an insect baculovirus, Autographa californica nuclear polyhedrosis virus (AcNPV). The template DNA used for in vitro transcription assays contained promoter sites for the baculovirus genes that have been classified as immediate early ($\alpha$) or early genes. These genes are located in the HindIII-K/Q region of the AcNPV genome. Nuclei isolated from the AcNPV-infected Spodoptera frugiperda cells were also used for in vitro transcription analysis by RNase-mapping the labeled RNA synthesized from in vitro run-on reaction in the isolated nuclei. The genes studied by this technique were p26 and pl0 genes which were classified as delayed early and late gene, respectively. We found that transcription of the genes from the HindIII-K region was accurately initiated and unique in the whole cell extract obtained from uninfected cells, although abundance of the in vitro transcripts was reverse to that of in vivo RNA. With isolated nuclei transcription of the p26 gene was inhibited by $\alpha$-amanitin suggesting that the p26 gene was transcribed by host RNA polymerase II. However, transcription of the pl0 gene in isolated nuclei was not inhibited by $\alpha$-amanitin, but rather stimulated by the inhibitor. We also found that the synthesis of $\alpha$-amanitin-resistant RNA polymerase was begun before 6 hr p.i., the time point at which the onset of viral DNA replication as well as the appearance of a-amanitin-resistant viral transcripts were detected. These studies give us strong evidence to support the previous data that early genes of AcNPV were transcribed by host RNA polymerease III, while transcription of late genes was mediated at least by a novel $\alpha$-amanitin-resistant RNA polymerase.

• Korean Journal of Veterinary Research
• /
• v.35 no.4
• /
• pp.671-681
• /
• 1995

This study was attempted to investigate the topographical distribution, shape and immunoreactivity of growth hormone-releasing factor(GRF)- and somatostatin(SOM)-immunoreactive neurons in the hypothalamus of the Korean squirrels(Sciurus vulgalis coreae). For the light microscopical examination of immunohistochemistry, the brains were fixed with 4% paraformaldehyde solution by means of intracardiac perfusion. And the frozen sections($40{\mu}m$ thick) were stained immunohistochemically by ABC method. Distribution of GRF immunoreactive neurons($12-17{\mu}m$) was highest in the paraventricular nucleus, moderate in the periventricular and supraoptic nuclei, and low in the arcuate nucleus and lateral hypothalamic area. Their immunoreactive fibers were found very high in the median eminence, moderately in the supraoptic, paraventricular and periventricular nuclei, and low in the arcuate nucleus and lateral hypothalamic area. SOM immunoreactive perikarya($14-18{\mu}m$) were found moderately in the periventricular nucleus near the subependymal layer of the third ventricle, and low in the arcuate and suprachiasmatic nuclei. SOM immunoreactive fibers were found high in the median eminence, and moderately or low in the arcuate and periventricular nuclei.

• Korean Journal of Veterinary Pathology
• /
• v.2 no.2
• /
• pp.73-84
• /
• 1998

This study was carried out to investigate on the serum chemistry and the DNA ploidy changes in carcinogenesis of the rat liver and kidney. Sixty male Sprague-Dawley rats were divided into two groups. Group I was non-treated control. Group II was given initiators (2,2'-dihydroxy- di-N-propylnitrosamine, 0.1% in drinking water(d.w.) for 1 week and N-ethyl-N-hydroxy-ethylnitrosamine; 0.15% in d.w. for 1 week) and promoters (3'methyl-cholanthrene; 3'MC, l0mg/kg, intraperitoneally(i.p.) twice a week and DL-serine; 0.05% in d.w. for 5 weeks, from 3 to 8 weeks). All examinations were performed at 12 and 20 weeks RBC, HGBCp＜0.05) and PCVCp＜0.01) significantly decreased in Group II at 20 weeks. Activities of ALT, AST(p＜0.05) and GGT(p＜0.01) were significantly increased in Group II at 20 weeks. Flow cytometric analysis showed hepatocyte nuclei from normal livers were predominantly tetraploid(66~67%) and then diploid(28~30%). Most of hepatocyte nuclei from carcinogen-treated rats were diploid (52~68%) and less were tetraploid(28~42%). Neoplastic liver nodules and hepatocellular carcinoma contained almost exclusively diploid nuclei. Renal cell nuclei from normal kidney were predominantly diploid(88~93%), those from carcinogen-treated rats had an abnormal DNA-content peak(aneuploidy, 6-7%), near the tetraploidy area. These results suggest that diploidy may be an effective screening marker of the liver carcinogenesis. Aneuploidy may be an useful marker in assessment of the experimental renal carcinogenesis.

• Journal of Life Science
• /
• v.8 no.4
• /
• pp.400-409
• /
• 1998

Formation of adduct was studied in benzo(a)pyrene(BP)- and doxorubicin(Dx)-treated human NC-37 cells and isolated nuclei. Major adducts formed were determined by fluorescence absorption spectrophotometery and DNA-lin-ked protein assay. When isolated nuclei were exposed to carcinogens BP and DMBA, and anticancer drugs m-AMSA, ellipticine and Dx, varying degrees of adduct formation occured between DNA-protein complex and these drugs. When the mixture was centrifuged 1.7 M sucrose solution, binding BP and DMBA appeared to be similar between the sediment and the supernatant. When the sediment was centrifuged again with 0.35% polymin-P, the amount of BP bound was 2-fold greater in the protein(1077$\pm$55cpm) than in DNA fraction (470$\pm$20cpm), whereas that of DMBA was 1.6-fold greater in the DNA than in protein fraction. In the case of m-AMSA, ellipticine and Dx, the amount of binding was slightly greater in supernatant than in sediment in centrifugation with 1.7 M sucrose, and more than 3 times greater in the DNA- than in protein- fraction in centrifugation with 0.35% polymin P. DNA fractions which associated with a subset of nonhistone chromosomal protein were isolated from NC-37 cells exposed to $^{3}$H-BP and $^{14}$C-Dx. They were separated into two distince components DNA-S and DNA-P by centrifugation with 2M Nacl chromatin extraction. The results indicated that the amount of $^{3}$H-BP bound was 6.0-fold greater in DNA-P as compared with DNA-S, while that of $^{14}$C-Dx binding appreaed to be 6.2-fold greater in DNA-S than in DNA-P fraction. When $^{3}$H-BP binding wasdetermined in the presence of cold Dx, the amount of binding was reduced only in the DNA-P fraction, indicating that the interaction between DNA and protein is decreased. Gene expression by these drugs, BP treated cells were increased to compare with nomal cells but reduced by treatment with BP-Dx. These results suggest that the protein moiety which tightly bound to DNA-P fraction may play an important role in the regulation of gene expression.

• The Korean Journal of Mycology
• /
• v.15 no.4
• /
• pp.250-253
• /
• 1987

The transfer of the isolated nuclei from P. florida into protoplasts of P. ostreatus was induced with polyethylene glycol and $CaCl_2$. Three types of transfer products of nuclei were obtained when transferred to MMM. Type 1 colonies were more vigrously growing mycelium and stable on MCM. One of the type 1 colonies, appeared segregation on MCM plus benomyl. The mycelium did not form clamp connection. These results suggest that type 1 colonies were nuclear hybrids or allodiploids. Type 2 was main products of nuclear transfer. The mycelium formed clamp connection and fertile on sawdust media. Type 3 was very slow growing or non-viable colonies after debris of nuclei or chromosomes transfer into recipient protoplasts. Isozyme pattern of esterase in type 1 produced a new band. Type 2 and type 3 could be characterized by parental bands.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.42 no.6
• /
• pp.49-56
• /
• 2005

An electron microbeam system has been developed to investigate the biological effect of cells by irradiating cell-nuclei with low-energy and low-flux electrons. It is essential to discern the cell nucleus from its cytoplasm and the culture medium and to locateit exactly onto the beam exit. The irradiation speed at more than 10,000 cells per hour is another requisite for the observations on cellular response to have good statistics. Long-time labor with patience and high concentration is needed since the frames of $320{\times}240{\mu}m^2$ should be moved more than 500 times for irradiating more than 10,000 cells per an hour. This paper describes the electron microbeam system with a focus on the user interfaces concerning the process of automatically recognizing the cell nuclei and injecting electron beam into the target cell nuclei at the irradiation speed of more than 10,000 cell nuclei per hour.