• Publications of The Korean Astronomical Society
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• v.22 no.4
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• pp.151-168
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• 2007

We have analyzed the comet records in the Korean history books: Samguksagi, Goryeosa, and Joseonwangjosillok. For a comparison, the Chinese and Japanese comet records collected by Kronk (1999) have also been analyzed. Power spectrum of the time series of the comet records is used to find periodic comets. Statistically significant periodicities in the power spectrum are detected at the periods of 38-40 years, about 76 years, and 300-400 years for all Korean, Chinese, and Japanese comet records. We have also calculated the past orbits of some comets that have been recently observed, to check whether or not they were recorded in the history books. We use a multistep method to numerically integrate the comet's orbital motion backward in time to 51 B.C. The gravitational force due to the Sun and the nine planets, non-gravitational force, and the relativistic effects have been considered. Comparison of comet's perihelion passage time and the position on the sky with the historical records shows that the comet Halley were recorded at every passage in both Goryeo and Joseon periods. The orbital motion of the comet Pons-Brooks has also been compared with the Korean records. For the comet Tempel-Tuttle, Swift-Tuttle, and Ikeya-Zhang, we have compared our calculation of the orbital motions with those of the previous studies.

• Journal of The Korean Society of Grassland and Forage Science
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• v.11 no.2
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• pp.137-142
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• 1991

For the constitution of forage cropping system including the double-cropping of corn, attention has been directed towards the early and short maturing varieties of corn such as Comet 80, Comet 85 and Linda as a component forage crop of forage cropping system. Four corn varieties, Comet 80, Comet 85, Linda and Suwon 19 were planted delayedly by each of 45, 55 and 65 days from the recommended sowing date of suwon 19. Under these condition, growth characteristics and late-sowing adaptability of 4 corn varieties were investigated, and the results are summarized as follows; 1. The variety of suwon 19 did not reach the stage of silking in the occasion of late sowing by 50 days from the optimum sowing time for mono cropping of suwon 19. However early varieties such as Comet 80, Comet 85 and Linda silked under the condition of 65 days-delayed sowing from the recommended sowing time of Suwon 19 for mono-cropping. 2. Early varieties of Comet 80, Comet 85 and Linda were so grown by approximately 92% in plant height, 66% in ear height, 88% in stem diameter and 81% in leaf number respectively compared to Suwon 19 at each of three delayed sowing time that exhibited the dwarfish appearance of canopy. 3. Days from sowing to silking decreased as the sowing time was delayed and the average days from sowing to silking in the sowing treatments of 55 days-delayed of Suwon 19, Comet 80, Comet 85 and Linda were 61, 46, 47 and 51 days, respectively. 4. The size of variations of plant height and ear height influenced by delayed-sowing time was comparatively larger in the varieties of Suwon 19 and Linda than in those of Comet 80 and Comet 85. 5. As sowing time was delayed from the optimum sowing time of Suwon 19 for mono-cropping, ear content decreased from 0% of Suwon 19 at 55 day-delayed sowing treatment to 3540% of Comet 80 and Comet 85 at 65 days-delayed sowing treatment.

• Journal of Veterinary Clinics
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• v.13 no.2
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• pp.158-162
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• 1996

Comet assay 는 포유류 세포에서 DNA의 파괴를 측정하는데 있어 신속하고 단순하며 시각적이고 민감한 방법이다. Apoptosis에서는 세포핵의 광범위한 DNA의 붕괴가 일어나므로 comet assay는 종양세포에서 apoptosis가 발생되었는가를 알아내는데 유용하다. 본 연구는 apoptosis 연구의 결과가 변화되지 않도록 comet assay slides를 좀 더 오래 보관할 수 있는 방법을 개발하고자 시행되었다. 개의 종양세포를 가지고 alkali comet assay를 끝낸 뒤 slides를 진공 건조기에서 꺼내서 증류수로 점적하여 10-20분간 침수시키고 현광현미경하에서 육안적으로 관찰하였다. 건조후 3-4일, 1주, 2주, 3주, 4주 및 7주의 slides에서 apoptosis 회복율(%)은 각각 98.1, 98.3, 99.4, 80.8 및 35.2%이었다. 3주 이내의 slides에서 대조군과 비교하여 apoptosis 회복율에서 차이가 없었으나 4주 이상의 slides를 건조후 침수시키는 방법을 이용하였을 때 apoptosis 평가에서 건조 후 3주간까지는 처음의 결과와 차이가 없으며, 이 방법을 이용하여 comet slide의 좀 더 긴 기간이 보관과 보관후의 재평가에서 이용될 수 있는 좋은 방법이 된다.

• Toxicological Research
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• v.22 no.4
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• pp.423-429
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• 2006

Recent reports on the photocarcinogenicity and photogerotoxicity of many compounds led to an increasing awareness for the need of a standard approach to test for photogenotoxicity. The comet assay has been recently validated as a sensitive and specific test system for the quantification of DNA damage. Thus, the objectives of this study are to investigate the utility of photo-comet assay for detecting photo-mutagens, and to evaluate its ability to predict rodent photo-carcinogenicity. Photo-comet assays were performed using L5178Y $Tk^{+/-}$ mouse lymphoma cells on five test substances (8-methoxypsoralen, chlorpromazine, lomefloxacin, anthracene and retinoic acid) that demonstrated positive results in photocarcinogenicity tests. For the best discrimination between the test substance-mediated DNA damage and the undesirable DNA damage caused by direct UV absorption, a UV dose-response of the cells in the absence of the test substances was firstly fnalized. Out of 5 test substances, positive comet results were obtained for chlorpromazine, lomefloxacin, anthracene and retinoic acid while 8-methoxypsoralen found negative. An investigation into the predictive value of this photo-comet assay for determining the photocarcinogenicity showed that photo-comet assay has relatively high sensitivity. Therefore, the photo-comet assay with mammalian cells seems to be a good and sensitive predictor of the photocarcinogenic potential of new substances.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.102.1-102.1
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• 2012

In this paper, we analyzed Korean historical records of the periodic comet Halley in three periods (Three Kingdoms, the Goryeo dynasty, and the Joseon dynasty) using various sources such as Samguksagi (History of the Three Kingdoms), Goryeosa (History of the Goryeo Dynasty), and Joseonwangjosillok (Annals of the Joseon Dynasty). To determine the apparition time of the comet at each return, we referred to the works of Kronk. For the Three Kingdoms period, we could not find any record relevant to Halley's comet from Samguksagi. Instead, we examined the suggestion that the phenomenon two Suns appearing on April 1, 760 (in a luni-solar calendar), which is recorded in Samgukyusa (Renaissance of the Three Kingdoms), indicates an appearance of comet Halley during the daytime. In contrast, we found that all the returns of Halley's comet during the Goryeo dynasty are recorded, although some accounts are questioned. In addition, we found that the appearance of Halley's comet in 1145 is also mentioned in a spirit-path stele made in 1178. For the Joseon dynasty period, we found that all the returns of the comet are recorded, as with the Goryeo dynasty, except for the return of 1910, in which the former dynasty fell. In conclusion, we think that this study will be helpful for understanding Korean historical accounts of Halley's comet.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.4
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• pp.472-476
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• 2008

The possibility of DNA comet assay as a rapid method for screening the irradiated vegetables and grains was evaluated. Vegetables (spring onion, garlic, and tomato) irradiated at $0{\sim}3$ kGy and grains (rice flour and black soybean) irradiated at $0{\sim}9$ kGy were used as samples. Optimum DNA comet assay conditions, such as elution, sedimentation of suspension, and lysis time of cell, were established. The optimum conditions for vegetables were 10 min for the elution time, 0 min for the sedimentation time, and 5 min for the lysis time. The optimum conditions for grains were 15 min for the elution time, 60 min for the sedimentation time, and 30 min for the lysis time. For the food application of DNA comet assay, it was possible to screen various food samples irradiated at the following doses: spring onion at 2 kGy, garlic at 3 kGy, tomato at 1 kGy, rice flour at 9 kGy, and black soybean at 3 kGy. Each sample showed different forms and sizes in DNA comet. Therefore, further studies on various methods using comet shape, concentration, or area in DNA comet assay are necessary.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.5
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• pp.843-848
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• 2000

The single cell-gel electrophoresis assay (comet assay) was used to identify irradiated beans. Soy beans, kidney beans, and red beans were irradiated with $^{60}Co$ gamma rays at 0.1, 0.3, 0.5, 0.7, and 1.0 kGy. Beans were peeled out, crushed lightly, and treated with phosphate-buffered saline (PBS) to extract cells. The extracted cell suspension was mixed with agarose gel solution and spread on an agarose precoated slide. After lysis of the cells, they were subjected to microgel electrophoresis for 2 minutes, and then silver-stained. We found that the DNA fragments of the irradiated samples were stretched, migrated out of the cells, and formed tails towards the anode giving the appearance of comets, while the unirradiated or the undamaged cells formed very short or no tails. The tail lengths of irradiated samples were significantly increased as irradiation dose increased at the above 0.3 kGy.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• v.23 no.1
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• pp.12-17
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• 1995

Space explorations by spacecraft have detected the solar wind and the interplanetary magnetic field (IMF), whose existences had been suggested to explain the narrow comet plasma tail formation before the space age. Thereafter, a global magnetic structure seperating the opposite polarity regions of IMF in the heliosphere was discovered (Wilcox and Ness, 1965). It is called helispheric current sheet (HCS). Comets have been proved as the useful heliospheric probes. Recently, another capability of comet as a probe of HCS was suggested by Yi (1994). In the process of comet plasma tail disconnection events (EDs) showing the ray folding and main tail severance between the folding rays (Brandt, 1982), the folding rays preceding DE might be the visualization of HCS draped around comet, In order to test this new idea, the association of comet Halley 16 DEs with comet crossings of HCS confirmed by spacecraft observations at the time of comet Halley apparition 1985~1986 was investigated.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.19.2-19
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• 2003

• Korean Journal of Food Science and Technology
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• v.32 no.3
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• pp.531-537
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• 2000

The simple microgel electrophoresis of single cells, a 'comet assay', on fruit seeds enabled the rapid identification of irradiated fruits by comparing the intact non-irradiated cells and the damaged cells of irradiated fruits. Grapes and plums were irradiated with 0.1, 0.5, 0.7, 1.0 kGy and strawberries, peaches, apples, and nectarines were irradiated with only 1.0 kGy. Seeds were isolated, crushed, and the suspended cells were embedded in an agarose layer. After lysis of the cells, they were subjected to microgel electrophoresis for 2 minutes, and then stained. The DNA radiation-induced fragmentation of all the fruits stretched and migrated out of the cells forming a tail toward the anode giving the appearance of a comet, while the undamaged cells appeared as intact nuclei without tails. Grape and plum seeds irradiated at 0.5 kGy and higher showed significant increases in tail length. With increasing the irradiation doses, longer extention of the DNA from the nucleus toward the anode was observed. Strawberry, peach, apple, and nectarine seeds irradiated with 1.0 kGy also showed the longer tails than non-irradiated ones. DNA comet assay as a rapid and inexpensive screening technique could be an officially validated method for the detection of irradiated fruits.