• Journal of Microbiology
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• 제42권2호
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• pp.99-102
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• 2004

Bacteriophage PM2 has a closed circular form of double stranded DNA as a genome. This DNA from the phage is a useful source for nick-circle endonuclease assay in the fmol range. Due to difficulties in the maintenance of viral infectivity, storage conditions of the phage should be considered for the puri-fication of PM2 DNA. The proper condition for a short-term storage of less than 2 months is to keep the PM2 phage at 4$^{\circ}C$; whereas the proper condition for a long-term storage of the PM2 phage for over 2 months is to keep it under liquid nitrogen in 7.5 ％ glycerol. The optimal conditions for a high yield of phage progeny were also considered with the goal to achieve a successful PM2 DNA preparation. A MOI(Multiplicity Of Infection) of 0.03, in which the OD$\sub$600/ of the host bacteria was between 0.3 and 0.5, turned out to be optimal for the mass production of PM2 phage with a burst size of about 214. Considerations of PM2 genome size, and the concentrations and radiospecific activities of purified PM2 DNA, are required to measure the endonuclease activity in the fmol range. This study reports the proper quantitation of radioactivity and the yield of purified DNA based on these conditions.

• 한국균학회소식:학술대회논문집
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• 한국균학회 2015년도 춘계학술대회 및 임시총회
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• pp.20-20
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• 2015

Endophytic fungi are microorganisms inhabiting living plant tissues without causing apparent harm to the host. They are drawing increasing attention due to their ability to produce various bioactive compounds as well as their effects on host growth and resistance to biotic and abiotic stresses. As a first step to assess biodiversity of plant associated fungi in Korea and the following evaluation on diverse biological activities, we are collecting endophytic fungi from plant in wild followed by systematic long-term storage in liquid nitrogen. Molecular identification using ITS sequences was also incorporated for pure culture by hyphal tip isolation. As of April 2015, about 1,400 fungal strains had been isolated from about 170 plant taxa. Fungal isolates belonging to Pleosporales, Diaporthales, Glomerellales, Hypocreales, and Xylariales were the most abundant. These collections are being used for several complementary researches, including screening of isolates with novel bioactive compounds or conferring drought stress resistance, phylogenetic and genomic study. Genome sequencing was performed for 3 isolates, one Xylaria sp. strain JS573 producing griseofulvin, an antifungal compound, and two Fusarium spp. strains JS626 and JS1030, which are assumed to be new species found in Korea. More detailed analysis on these genomes will be presented. These collections and genome informations will serve as invaluable resources for identifying novel bioactive materials in addition to expand our knowledge on fungal biodiversity.

• 한국자동차공학회논문집
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• 제22권5호
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• pp.13-19
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• 2014

Urea-SCR system is the selective catalytic reduction to reduce nitrogen oxides ($NO_x$) emitted from diesel vehicles. The objective of this study is numerical analysis of 3-dimensional unsteady melting problems of frozen urea by using an electric heater. It can be applied to determine capacity of power with respect to time and the location of the urea suction pipe in urea storage tank. The study includes the change of liquid volume fraction, temperature profiles and a influence of natural convection by using the commercial software STAR-CCM+(v7.06). The accuracy of the numerical analysis is estimated by comparisons with experimental data. After validation, a numerical analysis for freezing urea is conducted with four different heating power. From the results, it was found that relation of velocity of phase interface and amount of melting urea by increasing heating power in a container. There is also a difference in trend between velocity of phase interface and amounts of melting urea because of effect of natural convection.

• Journal of Chest Surgery
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• 제24권5호
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• pp.438-444
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• 1991

This study was designed to evaluate the viability of canine trachea after cryopreservation for two months. Eight cervical tracheal rings were resected in three dogs and both ends were anastomosed. The resected tracheal segments were cryopreserved and stored in liquid nitrogen at -196oC for two months. Two months later, the cryopreserved segments were thawed. Half of each segment was implanted into the abdomen of its donor animal and the other half was cultured in tissue media. Two weeks later, the animal was sacrificed. The native cervical trachea was removed to serve as a control and the abdominally implanted trachea was removed for study. At that time, both specimens were also cultured in tissue media. Tracheal epithelial viability was assessed histologically by using an inverted microscope. The epithelial cells were confirmed immunohistochemically using monoclonal antibodies against cytokeratin and epithelial membrane antigen. Control and cryopreserved segments showed good, viable epithelial cells, but the implanted segments showed slightly depressed viability. We conclude that canine tracheal epithelium can survive after cryopreservation for two months, but the implanted trachea will be slightly damaged by ischemia before revascularization, even if omental wrapping is used.

• Journal of Plant Biotechnology
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• 제8권1호
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• pp.43-50
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• 2006

The goal of this research was to develop an efficient cryopreservation protocol for germplasms of yam (Diosorea batatas), that were cultivated in Korea. Comparative studies with four other cryogenic techniques and subsequent experiments for shoot regrowth were conducted. in vitro-grown shoot-apices of the D. batatas were successfully cryopreserved by encapsulation-dehydration. The maximum survival of shoot-apices could be achieved when the precultured (with 0.3 M of sucrose for one day) and encapsulated (with a 3%(w/v) Na-alginate solution) apices were dehydrated for $3.5{\sim}4\;h$ prior to direct immersion in LN (liquid nitrogen). The frequency of regrowth rate of cryopreserved apices was not decreased during 3-month storage period. The thawing method markedly affected survival of the cryopreserved apices, and thawing at $40^{\circ}C$ for 3 min produced the best results. When cryopreserved apices were post-cultured on the post-culture medium (MS), supplemented with $0.2mgl^{-1}$ of BA ($N_6$-benzyladenine) and $0.2mgl^{-1}$ of kinetin, they showed direct shooting without callusing.

• 식물조직배양학회지
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• 제22권2호
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• pp.115-120
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• 1995

국내품종인 동진벼와 태백벼의 미숙접합자배 유래 배발생 현탁배양 세포의 초저온 보존 시스템을 개발하였다. 동결/해동 후 캘러스 재생률은 동진벼의 경우 2 M DMSO와 0.4 M sucrose를 태백벼의 경우 0.64 M DMSO와 0.4 M sucrose를 혼용처리하였을 때 캘러스 재생률이 각가 88%와 90%로 가장 높았다. 또한 고농도의 삼투용액에서 배양세포 의 전처리 과정은 필요하지 않았다. 재생된 캘러스를 1 mg/L NAA와 5 mg/L kinetin이 첨가 된 $N_{6 }$, 배지로 이식하여 명배양하였을 때 체세포배발생을 통하여 다수의 유식물체가 발달하였다. 약 100여개의 식물체가 재분화되었으며, 이중 25%는 albino이었다.다.

• 한국초전도ㆍ저온공학회논문지
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• 제15권4호
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• pp.6-9
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• 2013

Korea Superconducting Tokamak Advanced Research (KSTAR) has a helium refrigeration system (HRS) with the cooling capacity of 9 kW at 4.5 K. Main cold components are composed of 300 tons of superconducting (SC) magnets, main cryostat thermal shields, and SC current feeder system. The HRS comprises six gas storage tanks, a liquid nitrogen tank, the room temperature compression sector, the cold box (C/B), the 1st stage helium distribution box (DB#1), the PLC base local control system interconnected to central control tower and so on. Between HRS and cold components, there's another distribution box (DB#2) nearby the KSTAR device. The entire KSTAR device was constructed in 2007 and has been operated since 2008. This paper will present the maintenance result of the KSTAR HRS during the campaign and discuss the operation record and maintenance history of the KSTAR HRS.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권5호
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• pp.372-378
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• 2000

The cell culture of Angelica gigas Nakai producing decursin derivatives and immunostimulating polysaccharides was preserved in liquid nitrogen after pre-freezing in a deep freezer at -70$^{\circ}C$ for 480 min. The effects of the cryoprotectant and pretreatment before cooling were investigated to obtain the optimal procedure for cyropreservation. When compared to mannitol, sorbitol, or NaCl with a similar osmotic pressure, 0.7 M sucrose was found to be the best osmoticum for the cryopreservation of A. gigas cells. In the pre-culture medium, the cells in the exponential growth phase showed phase showed the best post-freezing survival after cryopreservation. A mixture of sucrose, glycerol, and DMSO was found to be an effective cryoprotectant and a higher concentration of the cryoprotectant provided better cell viability. When compared with the vitrification, the optimum cryopreservation method proposed in this study would seem to be more effective for the long-term storage of suspension cells. The highest relative cell viability established with the procedure was 89%.

• 한국양식학회지
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• 제21권1호
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• pp.54-59
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• 2008

The present study aimed to find the best diluent and cryoprotectant for sperm cryopreservation of filefish Thamnaconus modestus. Two kinds of artificial seminal plasma(ASP1, ASP2), 0.3 M glucose and marine fish Ringer's solution(MFRS) were employed as diluent. Dimethyl sulfoxide(DMSO) and methanol as cryoprotectant were selected for sperm cryopreservation. Sperm was diluted at the ratio of 1:3 with diluents containing cryoprotectants and adjusted for final concentration at 5%, 10%, 15% and 20%. Mixed milt was frozen at liquid nitrogen vapor after equilibration for 5 min. The highest motility($40.5{\pm}2.8%$) and swimming speed($81.5{\pm}4.1{\mu}m/s$) of frozen/thawed sperm were observed in ASP1 diluent containing 10% DMSO and in ASP2 containing 15% DMSO, respectively. Results showed that cryopreservation with ASP as diluent and DMSO as cryoprotectant could be adopted for long term storage of filefish sperm.

• 한국초전도ㆍ저온공학회논문지
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• 제25권3호
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• pp.43-48
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• 2023

Polymer composites, especially glass fiber reinforced polymer (GFRP) are finding ever-increasing applications in areas such as superconductivity, space technology, cryogenic rocket engines, and cryogenic storage vessels. Various components made of polymer composites are much lighter than their metallic counterparts but have equivalent strength for ultra-low temperature applications. In this paper, we have investigated the tensile properties of an indigenously prepared unidirectional cylindrical hollow composite tube for its use as a neck of the cryogenic vessel. XRD and SEM of the tube are completed before cryogenic conditioning to ascertain the fiber and resin distribution in the matrix. The result shows that for composites, after 15, 30, 45, and 60 minutes of cryogenic conditioning at 77K in a liquid nitrogen bath, the strength and modulus increase significantly with the increase of strain rate and reach the optimum value for 45 minutes of conditioning. The results are encouraging as they will be helpful in assessing the suitability of GFRP in the structural design of epoxy-based components for cryogenic applications.