• 한국수정란이식학회지
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• 제27권1호
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• pp.63-69
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• 2012

The objective of this study was to investigate the effectiveness of cryopreservation methods for the effect of various vitrification containers, such as EM-grid, OPS, or cryo-loop on the survival and developmental rate of vitrified mouse pronuclear embryos, and mouse cleavage embryo, at 21, 24, 27 and 30 hr after hCG injection. Post-thaw cleavage was similar among treatments, while the developmental rates of mouse blastocyst and hatched blastocyst were higher ($p$ <0.05) in 27 hr and 30 hr than 21 hr. The developmental rate of hatched blastocyst at vitrified cleavage mouse embryos in cryo-loop was significantly higher than vitrified pronuclear embryos of control group as well as EM-grid and OPS ($p$ <0.05). The developmental rate using cryo-loop was higher than EM-grid, but in case of OPS at vitrified cleavage and mouse pronuclear embryos, no significant difference was noticed. These results of our study show that the developmental rates of mouse embryos were unaffected by various vitrification containers, but in case of mouse embryos and hatched blastocysts at late vitrified pronuclear embryos the developmental rates were higher than early vitrified pronuclear embryos. Moreover, the developmental rate of hatched blastocyst at vitrified cleavage mouse embryos was significantly higher than vitrified pronuclear embryos. For better execution of this study, it will be mandatory to include improvement of vitrification containers, cryopreservation methods and conditions, higher survival rate, safe preservation, contamination and embryo loss.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.4-4
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• 2009

Paper factories use a large amount of water and same amount of wastewater is generated. It is important to recycle the wastewater because of water shortages and water pollution. The existing water treatment facilities like precipitation process need large-scale equipment and wide space to purify the wastewater of paper factory. High gradient magnetic separation (HGMS) system has the merits to purify rapidly because of large voids at filter and to occupy small space. In this paper, two types of superconducting magnets were used for HGMS systems. Cryo-cooled Bi-2223 superconducting magnet system with 70 mm room temperature bore and 200 mm of height was prepared. Cryo-cooled Nb-Ti superconducting magnet with 100 mm room temperature bore and 600 mm of height was used for magnetic separator. Magnetic filters were designed by the analysis of magnetic field distribution at superconducting magnets. The various magnetic seeding reactions were investigated to increase the reactivity of coagulation. The effects of magnetic separation of wastewater were investigated as variation of magnetic field strength and flow rate of wastewater.

• 한국재료학회지
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• 제33권2호
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• pp.63-70
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• 2023

In this study, crystallization was effectively suppressed in Al-based metallic glasses (Al-MGs) during pulverization by cryo-milling by applying an extremely low processing temperature and using a surfactant. Before Al-MGs can be used as an additive in Ag paste for solar cells, the particle sizes of the Al-MGs must be reduced by milling. However, during the ball milling process crystallization of the Al-MG is a problem. Once the Al-MG is crystallized, they no longer exhibit glass-like behavior, such as thermoplastic deformation, which is critical to decrease the electrical resistance of the Ag electrode. The main reason for crystallization during the ball milling process is the heat generated by collisions between the particles and the balls, or between the particles. Once the heat reaches the crystallization temperature of the Al-MGs, they start crystallization. Another reason for the crystallization is agglomeration of the particles. If the initially fed particles become severely agglomerated, they coalesce instead of being pulverized during the milling. The coalesced particles experience more collisions and finally crystallize. In this study, the heat generated during milling was suppressed by using cryo-milling with liquid-nitrogen, which was regularly fed into the milling jar. Also, the MG powders were dispersed using a surfactant before milling, so that the problem of agglomeration was resolved. Cryo-milling with the surfactant led to D50 = 10 um after 6 h milling, and we finally achieved a specific contact resistance of 0.22 mΩcm² and electrical resistivity of 2.81 μΩcm using the milled MG particles.

• Molecules and Cells
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• 제46권9호
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• pp.538-544
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• 2023

The formation of uniform vitreous ice is a crucial step in the preparation of samples for cryogenic electron microscopy (cryo-EM). Despite the rapid technological progress in EM, controlling the thickness of vitreous ice on sample grids with reproducibility remains a major obstacle to obtaining high-quality data in cryo-EM imaging. The commonly employed classical blotting process faces the problem of excess water that cannot be absorbed by the filter paper, resulting in the formation of thick and heterogeneous ice. In this study, we propose a novel approach that combines the recently developed nanowire self-wicking technique with the classical blotting method to effectively control the thickness and homogeneity of vitrified ice. With simple procedures, we generated a copper oxide spike (COS) grid by inducing COSs on commercially available copper grids, which can effectively remove excess water during the blotting procedure without damaging the holey carbon membrane. The ice thickness could be controlled with good reproducibility compared to non-oxidized grids. Incorporated into other EM techniques, our new modification method is an effective option for obtaining high-quality data during cryo-EM imaging.

• KEPCO Journal on Electric Power and Energy
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• 제2권2호
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• pp.307-310
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• 2016

The operational cost for maintaining the superconductivity of high-temperature superconducting (HTS) cables needs to be reduced for feasible operation. It depends on factors such as AC loss and heat transfer from the outside. Effective operation requires design optimization and suitable operational conditions. Generally, it is known that critical currents increase and AC losses decrease as the operational temperature of liquid nitrogen ($LN_2$) is lowered. However, the cryo-cooler consumes more power to lower the temperature. To determine the effective operational temperature of the HTS cable while considering the critical current and AC loss, critical currents of the HTS cable conductor were measured under various temperature conditions using sub-cooled $LN_2$ by Stirling cryo-cooler. Next, AC losses were measured under the same conditions and their variations were analyzed. We used the results to select suitable operating conditions while considering the cryo-cooler's power consumption. We then recommended the effective operating temperature for the HTS cable system installed in an actual power grid in KEPCO's 154/22.9 kV transformer substation.

• 대한원격탐사학회지
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• 제26권3호
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• pp.335-346
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• 2010

Recently, ESA (European Space Agency) has launched CryoSAT-2 for polar ice observations. CryoSAT-2 is equipped with a SIRAL (SAR/interferometric radar altimeter), which is a high spatial resolution radar altimeter. Conventional altimeters cannot measure a precise three-dimensional ground position because of the large footprint diameter, while SIRAL altimeter system accomplishes a precise three-dimensional ground positioning by means of interferometric synthetic aperture radar technique. In this study, we developed an efficient SIRAL SARIn mode processing technique to measure a precise three-dimensional ground position. We first simulated SIRAL SARIn RAW data for the ideal target by assuming the flat Earth and linear flight track, and second accessed the precision of three-dimensional geopositioning achieved by the proposed algorithm. The proposed algorithm consists of 1) azimuth processing that determines the squint angle from Doppler centroid, and 2) range processing that estimates the look angle from interferometric phase. In the ideal case, the precisions of look and squint angles achieved by the proposed algorithm were about -2.0 ${\mu}deg$ and 98.0 ${\mu}deg$, respectively, and the three-dimensional geopositioning accuracy was about 1.23 m, -0.02 m, and -0.30 m in X, Y and Z directions, respectively. This means that the SIRAL SARIn mode processing technique enables to measure the three-dimensional ground position with the precision of several meters.

• 한국가축번식학회지
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• 제25권4호
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• pp.371-379
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• 2001

본 연구는 체외에서 생산된 소 수정란의 동결을 위한 최적치 조건을 규명할 목적으로 실시하였다. 동결을 위하여 체외에서 생산된 8 세포기, 상실배기 및 비반포기 단계의 수정란을 공시하여 EC 5.5 동결온액에 20초 동안 노출시키고, 각 용기에 장착한 후, 즉시 -196$^{\circ}C$ 액체질소에 침지하는 유리화동결법을 채택하였다. 그 후 0.5 M, 0.25 M 및 0.121 M sucrose 용액에서 각 1분간씩, 연속으로 응해 한 다음, 10 % FBS가 첨가된 CR Iaa 배양액으로 옮겨 배양하였다. 그 결과 수정란의 재팽창률과 완전부화율은 EM grid, OPS 및 Cryo-loop 등과 같은 동결용기에 의해 큰 차이를 보이지 않았다. 또 Hoechst 염색에 의해 조사한 동결융해 후 체외에서 발달된 완전팽창 배반포의 총세포수에 있어서도, 대조군 (180.0 $\pm$ 5.4)과 동결군 (178.0 $\pm$ 7.5) 사이에 차이가 없었고, 동결융해 후 세포의 손상을 이중염색법으로 조사한 생존세포와 사멸세포의 비율도 대조군 (176 : 4)과 동결군 (172 : 6) 사이에 유의차가 인정되지 않았다. 이러한 결과로 보아 소 수정란은 EG 5.5 동결용액과 EM grid, OPS 또는 Cryo-loop과 같은 동결용기에 의해 성공적으로 동결보존할 수 있는 것으로 판단된다.

• 한국수정란이식학회지
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• 제29권3호
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• pp.249-255
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• 2014

Programmed cell death or apoptosis is associated with changes in $K^+$ concentration in many cell types. Recent studies have demonstrated that two-pore domain $K^+$ ($K_{2P}$) channels are involved in mouse embryonic development and apoptotic volume decrease of mammalian cells. In cerebellar granule neurons that normally undergo apoptosis during the early developmental stage, TASK-1 and TASK-3, members of $K_{2P}$ channels, were found to be critical for cell death. This study was performed to identify the role of $K^+$ channels in the $H_2O_2$-induced or cryo-induced cell death of mouse and bovine embryos. Mouse and bovine two-cell stage embryos (2-cells) exposed to $H_2O_2$ for 4 h suffered from apoptosis. The 2-cells showed positive TUNEL staining. Treatment with high concentration of KCl (25mM) inhibited $H_2O_2$-induced apoptosis of 2-cells by 19%. Cryo-induced death in bovine blastocysts showed positive TUNEL staining only in the cells near the plasma membrane. Cryoprotectant supplemented with 25 mM KCl reduced apoptosis slightly compared to cryoprotectant supplemented with 5 mM KCl. However, the combination of antioxidants (${\beta}$-mercaptoethanol) with 25 mM KCl significantly decreased the rate of $H_2O_2$-induced and cryo-induced apoptosis compared to treatments with only antioxidants or 25 mM KCl. These results show that blockage of $K^+$ channel efflux for a short-time reduces $H_2O_2$- and cryo-induced apoptosis in mouse and bovine embryos. Our findings suggest that apoptosis in mouse and bovine embryos might be controlled by modulation of $K^+$ channels which are highly expressed in a given cell type.

• Restorative Dentistry and Endodontics
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• 제34권4호
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• pp.356-363
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• 2009

본 연구의 목적은 흰 쥐의 상악 대구치를 발거한 후 치주인대세포를 압력을 이용한 저속 냉동 보관법으로 냉동 보관시 치주인대세포의 활성도를 저속 냉동법, 냉장 보관법과 비교하여 평가하고자 하였다. 생후 4주된 암컷 Sprague-Dawley계 흰쥐의 상악 좌우 제 1,2 대구치를 발거하여 각 군 당 18개의 쥐 치아를 MTT, WST-1 검색에 이용하였다. 실험군은 4개군으로 대조군은 즉시 발치군이며, $4^{\circ}C$냉장고에 일주일간 보관한 냉장군, 발치 후 동해방지제 처리과정을 거쳐 $4^{\circ}C$에서 $-35^{\circ}C$까지 $-0.5^{\circ}C$/min 속도로 서서히 냉동시킨 뒤 $-196^{\circ}C$에 냉동한 저속 냉동군, 3MPa의 압력을 가하고 $-0.5^{\circ}C$/min 속도로 $4^{\circ}C$에서 $-35^{\circ}C$까지 서서히 냉동시킨 뒤 $-196^{\circ}C$에 냉동한 압력 저속 냉동군으로 나누었다. 보존액은 F medium을 사용했으며 동해방지제로 10% dimethylsulfoxide(DMSO)를 사용하였다. 일주일 후 해동하여 MTT, WST-1검색을 시행한 뒤 치근면을 단위면적으로 표준화하기 위해 MTT, WST-1 측정값을 Eosin 염색 후 530nm에서 측정한 흡광도 값으로 나누었다. 통계 분석을 위해 one way ANOVA를 시행하였으며 사후 검정으로는 Tukey 방법을 사용하였고 결과는 다음과 같다. 1. MTT 검색에 의한 흡광도를 Eosin 염색 후 측정한 흡광도로 나눈 값에서는 압력 저속 냉동군은 즉시 발치군보다 유의성 있게 세포 활성도가 낮았으나(p<0.05), 저속 냉동군이나 냉장군과 비교할 때는 높은 세포 활성도를 보이며 통계적 유의성이 있었다(p<0.05). 2. WST-1 검색에 의한 흡광도를 Eosin 염색 후 측정한 흡광도로 나눈 값에서도 MTT 검색과 마찬가지로 압력 저속 냉동군에서는 즉시 발치군보다 유의성 있게 세포 활성도가 낮았으나(p<0.05), 저속 냉동군이나 냉장군과 비교할때는 높은 세포 활성도를 보이며 통계적 유의성이 있었다(p<0.05). 위의 결과를 통해, 3MPa(30기압) 압력을 이용한 저속 냉동 보관법은 $4^{\circ}C$냉장법이나 압력을 사용하지 않은 다른 냉동 보관법에 비해 우수한 쥐 치아의 치주인대세포의 활성도를 보여 차후 치아의 재식/이식을 위한 중-장기 치아보관을 위한 방법으로의 가능성을 제시하였다.

• Applied Microscopy
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• 제47권3호
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• pp.171-175
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• 2017

Negative staining has been traditionally used for exosome imaging; however, the technique is limited to surface topology only and can cause staining artifacts. Therefore, to analyze the internal structure of exosomes, we employed a method of block preparation, thin sectioning, and electron tomography. In addition, an automatic serial sectioning technique with 15-nm thickness through focused ion beam was employed to observe the three-dimensional structure of exosomes of various sizes. Cryo-transmission electron microscopy revealed the near-to-native structure of exosomes.