• 한국발생생물학회:학술대회논문집
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• 한국발생생물학회 2003년도 제3회 국제심포지움 및 학술대회
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• pp.98-98
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• 2003

Recently, human embryonic stem (hES) cells have become very important resources for ES cell basic research, cell replacement therapy, and other medical applications; thus, efficient cryopreservation methods for these cells are needed. This study examined whether a newly developed minimum volume cooling (MVC) vitrification method, which was tested through cryopreservation of sensitive bovine oocytes, can be used for freezing hES cells. Feeder-free cultured hES cell (MB03) colonies were mechanically dissected into several small clumps following enzymatic treatment. We compared the freezing efficiency of a slow-cooling method using a cryo-module (0.4-0.6C/min, 20-30 clumps/vial) and MVC vitrification using a modified 0.5-ml French mini-straw designated as a MVC straw (>$20,000{\circ}C$/min, 10 clumps/straw) After thawing, in vitro survival of hES cell clumps was higher for MVC-vitrified cells (80.8%, 97/120) than for slow-cooled cells (38.2%, 39/102). Further, the proliferation rate of surviving MVC-vitrified cells was similar to that of control hES cells from 2 weeks after thawing. In addition, vitrified-thawed hES cells demonstrated a normal karyotype, were positively immunostained for surface marker antibodies (AP, SSEA-4 and TRA-1-60) and the Oct-4 antibody, and could differentiate into all three embryonic germ layer cells in vitro. This result demonstrates that hES cell clumps can be successfully cryopreserved by a newly developed MVC vitrification method without loss of human cell characteristics.

• 한국수정란이식학회지
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• 제13권2호
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• pp.191-197
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• 1998

Immature nocytes and in VitrO matured Oocytes collected from the slaughtered Korean cattle were frozen slowly with 10% ethylene glycol+5% polyvinyl pyrolidine+0.05M trehalose (l0EPT), 10% ethylene glycol+5% ficoll+0.05M sucrose (1OEFS), or 10% ethylene glycol+5% ficoll+0.05M trehalose (l0EFT) by cell freezer (experiment 1). And also,They were ultra-rapidly frozen with 30% ethylene glycol+10% polyvinyl pyrolidine+0.5M trehalose (3OEPT) or 30% ethylene glycol+18% ficoll+0.5M sucrose (3OEFS) using electron microscope grid (experiment 2). In experiment 1, the cleavage rate was 23.0% when immature oocytes were frozen slowly using various cryoprotectants descrihed above, and 5.1% of cleaved oocytes developed to over morula stage after in Vitro fertilization (IVF). There were no significant differences among these groups. When matured oocytes were frozen slowly, the total cleavage rate was 19.7%, and over morula stage was 3.2%. lOEPT (4.8%) and EFS (4.4%) were slightly more effective than l0EFT (0.0%) for development in vitro. Only in l0EFT treated group, immature oocytes have higher developmental capacity than matured ones, when they were frozen slowly and IVF after thawing. In experiment 2, oocytes were ultra-rapidly frozen using the electron microscope grid with two kind of cryoprotectants described above. In immature oocyte group, the cleavage rate was 13.9% and 5.8% of cleaved oocytes developed to over morula stage after IVF, and in matured group, 25.7 and 7.6%, respectively. There were no significant differences between two kind of cryoprotectants, but in ultra-rapid freezing using electron microscope grid, the efficiency is slightly higher in matured oocyte group.

• 한국도로학회논문집
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• 제18권3호
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• pp.59-65
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• 2016

PURPOSES : This paper aims to develop a road pavement de-icing system using carbon sheet to replace the older snow de-icing method. Carbon sheet is a light and high-strength metal. Hence, various bodies of research for its applications in many industries have progressed. METHODS : The experiment was conducted in a laboratory. The carbon sheet supplied voltage through a power supply system, and produced heat transfers to the concrete surface. Various factors, such as pavement material, carbon sheet width, penetration depth, and freezing-thawing resistance, were considered in the conducted experiments to confirm the heating transfer efficiency of the carbon sheet. RESULTS : The carbon sheet used was a conductor. Therefore, it produced heat if voltage was supplied. The exposed carbon sheet on the atmosphere did not affect the carbon sheet width when it provided constant voltage. However, the sheet showed different heating behaviors by width change when the carbon sheet penetrated into the concrete. Moreover, the freezing-thawing resistance was decreased by the carbon sheet with increasing width. CONCLUSIONS : The experiments confirmed the possibility of developing a road snow melting system using a carbon sheet. The antiicing system using the carbon sheet to replace the traditional anti-icing system has disadvantages of environmental pollution risk and electric leakage. The pavement also improved its toughness resistance. The utilization value will be very high in the future if carbon sheet heat loss can be minimized and durability is improved.

• Reproductive and Developmental Biology
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• 제35권3호
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• pp.295-300
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• 2011

The objective of this study was to evaluate efficiency of methyl-beta-cyclodextrin (MBCD) in the sperm preservation of bull. For this study, the freezing of diluted semen were added with Triladyl containing 20% egg-yolk and/or 0, 1, 5, 10 and 20 mM MBCD before freezing process. Analysis of viability in frozen-thawed sperm was estimated by SYBR14/PI double stain, hypoosmotic swelling test(HOST) and acrosome damage with FITC-PNA, and mitochondria activation with Rhodamin123 by flow-cytometry. The sperm viability was significantly in 0 mM and 5 mM concentrations of MBCD than other groups (p<0.05). However, the HOST was significantly lower at 20 mM concentration of MBCD than other concentrations (p<0.05). In addition, acrosome damage and mitochondria activation rates were significantly lower at 20 mM concentration of MBCD than other groups (p<0.05). In conclusion, the viability of sperm was not significantly different among concentrations of MBCD 0, 5 and 10 mM, but MBCD 20 mM was significantly lower than other groups. In addition, as concentrations of MBCD was high, HOST, acrosome damage and mitochondria activation rates had a negative effect in bull sperm.

• Reproductive and Developmental Biology
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• 제34권1호
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• pp.41-46
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• 2010

The objective of this study was to evaluated the efficiency of sperm cryosurvival using each extenders Triladyl and LEY containing egg yolk to the cryopreservation of separated sperm by percoll in miniature pig. The ejaculated semen from miniature pig was separated by 65% percoll and un-separated sperm as a control before freezing. The freezing of diluted semen added with Triladyl containing egg yolk and LEY solution (solution I: 11% Lactose or Triladyl + egg yolk; solution II: solution I + glycerol + OEP). Analysis of sperm ability was estimated by viability, capacitation acrosome reaction using chlortetracycline (CIC) the morphologic abnormality and hypoosmotic swelling test(HOST). The groups were designed that as separated sperm by Percoll with Triladyl(ST) or LEY(SL) for cryopreservation. And unseparated sperm with Triladyl(UT) or LEY(UL). As a results, the viability was higher significantly(p<0.05) in ST, SL, UT than UL extender. The morphologic abnormality was measured significantly (p<0.05) lower in ST than other extenders. The AR-patterned in CTC analysis was measured significantly(p<0.05) lower in SL and UL than other extenders. In conclusion, using Triladyl extender resulted in viability and morphology of separated sperm by percoll that were effective than using LEY extender, but it resulted in capacitation acrosome reaction was lower than using LEY extender.

• Clinical and Experimental Reproductive Medicine
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• 제37권4호
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• pp.267-291
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• 2010

최근 동결기술이 발달하면서 다양한 목적에 따라 초기 발생단계, 특히 수정 전후의 난자나 수정란의 생명을 연장하는 것이 가능해졌다. 이러한 난자나 수정란의 보존기술은 인간의 수정능력을 배가시키거나 임신조절에서 응용되고 있으며, 동물에서는 우수한 유전자원의 보존과 운영, 저렴한 국제간 운송수단, 그리고 생식보조기술과 유전공학 등의 연구에 필요한 생식세포의 공급하는 데서도 중요하게 활용되고 있다. 최근 개발된 완만동결과 유리화 동결방법은 난자와 수정란을 장기간 동결하여 보존하는데 활용하는 주요 기술이다. 이러한 방법들은 각각 장점과 단점을 가지고 있지만, 상당한 수준의 효율성이 입증되어 실용화되어 있는 실정이다. 무엇보다도 유리화 방법은 완만동결 방법보다 13년이나 늦게 개발되었으나 보다 우수한 기술로 인정을 받고 있다. 비록 유리화 동결은 아직 대한 상반된 의견과 오염문제가 있지만 인간과 동물의 생식보조기술로 활용되는 빈도가 점차 많아지고 있는 실정이다. 따라서 본 원고에서는 먼저 난자와 수정란의 동결보존에 대한 기초적인 기술에 대해서 고찰한 다음, 유리화 동결에 관 한 최근의 연구동향에 대해서 종합적으로 검토하고자 한다.

• 한국응용곤충학회지
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• 제23권2호
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• pp.126-131
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• 1984

1. 영남작물시험장, 호남작물시험장 및 충남농촌진흥원에서 분양받은 18개의 벼종자시료와 충남지역 일반농가에서 수확한 8개의 벼종자시료 등 모두 26개의 종자시료를 공시하여 표준습지법으로 조사하였던 바 21종의 균류가 검출되었으며, 벼 갈샐잎마름병균(Gerlachia oryzae)은 22개의 벼 종자시료에서 $1.0\~45.0\%$의 범위로 검출되었다. 2. 종자전염성 G. oryzae의 효과적인 검출방법을 찾기 위하여 표준습지법, 냉동습지법, 물한천법 등으로 비교 조사한 결과, 냉동습지법에서 검출율이 가장 높았다. 3. 벼종자의 각 부위를 무균적으로 분리하여 부위별로 G. oryzae의 감염여부를 표준습지법으로 조사한 결과, 벼 종자의 껍질에서 가장 많이 검출되었으며, 심하게 이병된 종자는 배유 및 종피 뿐 만 아니라 배에 까지 감염되어 있었다. 4. G. oryzae에 감염된 벼 종자를 파종하여 심하게 이병된 종자는 종자부패 및 묘입고를 일으켰으며, 약하게 이병된 종자는 초엽, 1엽, 2엽에 갈색의 병징감염을 초래하였다.

• 한국건축시공학회지
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• 제3권2호
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• pp.129-134
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• 2003

In this research, we used fly-ash and blast-furnace slag as substitute material of cement and fine aggregate, and we, through experiments, researched and analyzed the features of high-flowable concrete added high efficiency AE water reduction agent. The results are below. 1. Liquefaction generally presented high-slump flow value; on the other hand, partial segregation was observed in case of mixing proportion with 65 cm slump flow and above. This segregation was partially improved in accordance with mixing admixture. 2. Compressive strength according to mixing admixture and increasing mixing ratio of fly-ash were subject to be declined when it was initially cast-in, but its gap was improved when time was fully passed. 3. After mixing blast-furnace slag and fly-ash as substitute material, the result showed that the modulus of elasticity against freezing & melting was improved according to mixing blast-furnace slag and also increased in accordance with increasing pulverulent-body volume. 4. According to increasing the mixing volume of fly-ash, the durability factor was deteriorated because compressive strength became lower as well as air content was decreased when it was initially case-in. 5. The minimum air content to secure durability was 3.7%, for that reason, we had better secure admixture such as air entraining agent when cast-in high-flowable concrete.

• 한국지반신소재학회논문집
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• 제17권4호
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• pp.81-92
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• 2018

최근 천연가스에 대한 수요가 높아지면서 이를 저장하기 위한 LNG 탱크의 건설이 증가하고 있다. LNG는 효율적인 저장을 위해 극저온의 유체로 액화되므로, LNG 탱크의 결함으로 인한 LNG 유출은 막대한 피해를 야기할 수 있다. 많은 연구자들이 다양한 LNG 유출 상황에 대하여 발생가능 한 피해 영향을 평가하였으나, 극저온의 LNG 유체가 유출될 경우 LNG 탱크를 지지하고 있는 지반에 미치는 영향에 대한 연구는 제한적이다. 따라서 본 논문에서는 LNG 탱크 및 지반의 다양한 조건을 고려하여 LNG 유출에 따른 동결 지반의 역학적, 열적 거동 변화에 대한 연구를 수행하였다. 유출 시나리오의 구현을 위해 수치해석을 수행하였으며, 상재하중, 온도 경계조건, 흙의 동결 민감성 변화에 따른 지반과 기초구조물 거동을 조사하고자 하였다. 이를 통해 LNG 유출 이후 지반의 단기 및 장기 온도변화를 평가하였으며, 지반 동결에 따른 간극 및 연직변위 변화를 분석하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제24권3호
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• pp.62-67
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• 2022

Liquid hydrogen (LH₂) has a higher density than gaseous hydrogen, so it has high transport efficiency and can be stored at relatively low pressure. In order to use efficient bulk hydrogen in the industry, research for the LH₂ supply system is needed. In the high-pressure hydrogen station based on LH₂ currently being developed in Korea, a heat exchanger is used to heat up supercritical hydrogen at 700 bar and 60 K, which is pressurized by a cryogenic high-pressure pump, to gas hydrogen at 700 bar and 300 K. Accordingly, the heat exchanger used in the hydrogen station should consider the design of high-pressure tubes, miniaturization, and freezing prevention. A helical heat exchanger generates secondary flow due to the curvature characteristics of a curved tube and can be miniaturized compared to a straight one on the same heat transfer length. This paper evaluates the heat transfer performance through parametric study on the distance between coils, guide effect, and anti-icing design of helical heat exchanger. The helical heat exchanger has better heat transfer performance than the straight tube exchanger due to the influence of the secondary flow. When the distance between the coils is uniform, the heat transfer is enhanced. The guide between coils increases the heat transfer performance by increasing the heat transfer length of the shell side fluid. The freezing is observed around the inlet of distribution tube wall, and to solve this problem, an anti-icing structure and a modified operating condition are suggested.