共查询到20条相似文献,搜索用时 31 毫秒
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Nawroth F Isachenko V Dessole S Rahimi G Farina M Vargiu N Mallmann P Dattena M Capobianco G Peters D Orth I Isachenko E 《Cryo letters》2002,23(2):93-102
The aim of our study was to investigate the effects of vitrification (cooling rate approximately 10000(C/min) without cryoprotectants on swim-up prepared human spermatozoa in comparison to standard conventional freezing with cryoprotectants. Motility, morphology, rate of viability and acrosome reaction of spermatozoa were evaluated. The described method of cryopreservation of human spermatozoa by direct plunging into liquid nitrogen slush without cryoprotectants was effective and could be recommended for routine IVF. 相似文献
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Minimum volume vitrification may provide extremely high cooling and warming rates if the sample and the surrounding medium contacts directly with the respective liquid nitrogen and warming medium. However, this direct contact may result in microbial contamination. In this work, an earlier aseptic technique was applied for minimum volume vitrification. After equilibration, samples were loaded on a plastic film, immersed rapidly into factory derived, filter-sterilized liquid nitrogen, and sealed into sterile, pre-cooled straws. At warming, the straw was cut, the filmstrip was immersed into a 39 degree C warming medium, and the sample was stepwise rehydrated. Cryosurvival rates of porcine blastocysts produced by parthenogenetical activation did not differ from control, vitrified blastocysts with Cryotop. This approach can be used for minimum volume vitrification methods and may be suitable to overcome the biological dangers and legal restrictions that hamper the application of open vitrification techniques. 相似文献
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Vitrification is widely used for cryopreservation of oocytes. The present study has built the theoretical models of four vitrification systems (micro-droplet, open pulled straws, quartz micro-capillary and cryotop), and performed numerical analysis to predict the cooling rates. The numerical analysis shows that the average cooling rate of the cryotop system was higher than those of other three systems between 298K and 100K. In addition, the effects of other process parameters on the cooling rate with the cryotop system were also investigated, including the thickness of the carrier, the volume of cryoprotectant agent, the temperature of cold source as well as the heat transfer coefficient, when plunging into liquid nitrogen. 相似文献
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浆态是一种固态与液态物质共存的状态,即在液体中含有固体小颗粒。浆氢在用作火箭和航天飞机的燃料方面有很广泛的应用前景;采用浆氮作为高温超导电缆的制冷剂则会明显提高电缆的冷却性能。主要介绍了浆氢和浆氮的制备方法,密度和流量的测量技术,及其管内流动及换热特性。 相似文献
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以R600a压力式封闭系统喷雾冷却过程为研究对象,对其换热过程进行分析。对液滴撞击热面后的状态进行建模,分析了其运动状态。通过忽略液膜的对流换热,引入韦伯数来简化并修正雾滴与热源表面的对流换热系数关联式;借鉴二次成核理论,通过单位时间内,单位面积上覆盖的雾滴数量对核态沸腾换热系数关联式修正。通过上述分析,以对流换热和核态沸腾换热两种机理为中心,建立了新的换热系数关联式。通过与其他文献的关联式、实验测量值进行比较、不同工质进行比较、不同实验系统比较,发现该式预测值和实验测量值偏差在±20%以内,能够很好地预测压力式封闭系统喷雾冷却过程的换热系数。 相似文献
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Isachenko V Isachenko E Reinsberg J Montag M Weiss J Braun F van der Ven H 《Cryo letters》2008,29(3):261-268
Standard protocol of freezing of human ovarian tissue presupposes the very slow cooling (-0.3 C/min) from auto-seeding to -40 C, then slow cooling (-10 C/min) to -140 C and then direct plunging into liquid nitrogen. The aim of this investigation was to compare the -10 C/min cooling rate of human ovarian tissue from -40 C to -140 C with the -220 C/min cooling rate (direct plunging into liquid nitrogen) from -36 degree C. After post-thawing in vitro culture of tissue, hormonal activity as well as follicle viability was evaluated. After culture of fresh tissue pieces (Group 1), pieces after freezing and thawing with slow cooling (-10 C/min) from -40 C (Group 2) and pieces after freezing and thawing with direct plunging into liquid nitrogen (-220 C/min) from -36 C (Group 3), the supernatants showed estradiol 17-ss concentrations of 481, 441 and 459 pg per ml, respectively, and progesterone concentrations of 9.05, 5.06, 4.87 ng per ml, respectively. It is concluded that 94, 96, and 98 percent follicles for Groups 1, 2 and 3, respectively, were normal. Technique of human ovarian tissue cryopreservation with very slow cooling to -36 C and then direct plunging into liquid nitrogen with -220 C/min cooling rate is tolerated without apparent detriment. 相似文献
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气-液两相流设备的性能受限于临界热流密度,开展流动微液膜动力学特性及其稳定性的相关研究是深入理解沸腾危机及临界热流密度机理的关键。采用光学玻璃制成的矩形通道作为实验段,使用微流量齿轮泵驱动去离子水,使其在实验通道入口处与在其上部流动的压缩空气接触形成同向流动的分层流。利用共轭光学探测器对流动微液膜的厚度进行了测量,利用高速摄像机对气-液两相分层流波动特性进行了可视化观测。研究表明,在绝热情况下,当液速一定时,液膜的平均厚度随着气速增加而减小,当气速增加到某一阈值时会导致液膜破裂。 相似文献
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Most cryopreservation procedures are optimized using a small number of germplasm accessions. We classified the garlic (Allium sativum L.) accessions that were selected for our studies based on genotype as identified using amplified fragment length polymorphism markers. Although recovery was variable, shoots regenerated from a broad range of the accessions after cryo-exposure. Garlic shoot tips were excised from cloves, surface sterilized, and placed on media at 5 degree C for 2 days prior to cryopreservation. Shoot tips were then treated with sucrose-glycerol for 20 minutes, plant vitrification solution 2 (PVS2; 15 percent w/v ethylene glycol, 15 percent w/v DMSO, 30 percent w/v glycerol, 13.7 percent w/v sucrose) at 0 degree C, and then plunged on foils into liquid nitrogen slush. Explants were recovered in 1.2 M sucrose for 20 minutes and then plated onto Gamborgs B5 medium containing alpha-naphthaleneacetic acid (NAA) and 6-(gammagamma-dimethylallylamino purine) (2-iP). Our results demonstrate that genotypically diverse accessions of garlic can be successfully cryopreserved. 相似文献
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Human embryonic stem (ES) cells have far-reaching applications in the areas of tissue engineering, regenerative medicine, pharmacology and basic scientific research. Although the culture conditions can maintain the human ES cells in an undifferentiated state for a transient period, spontaneous differentiation has also been observed during the routine culturing of ES cells. However, the maintenance of ES cells in the undifferentiated, pluripotent state for extended periods of time will be required in many areas of scientific research. Cryopreservation is a technology with potentially far reaching implication for the development and widespread use of such cell lines. This study was undertaken to develop and optimize a protocol for cryopreservation of human ES cells through programmed cooling. The effects of the seeding temperature, the cooling rate and the sub-zero temperature to which the samples were cooled before plunging into liquid nitrogen(the terminal temperature), all significantly affected the recovery of cryopreserved ES cells. After studying these factors, an improved protocol was obtained: the sample was cooled from 0 degree C to -35 degree C at a cooling rate of 0.5 degree per min, with seeding was set at -10 degree C, before being plunged immediately into the liquid nitrogen. Using this protocol, 9 of 11 colony fragments survived freezing and thawing and could be cultured for prolonged periods. They retained the properties of pluripotent cells, had a normal karyotype and showed histochemical staining for alkaline phosphatase. 相似文献
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Thammasiri K 《Cryo letters》2000,21(4):237-244
Seeds from selfing of a Thai orchid (Doritis pulcherrima Lindl.) were successfully cryopreserved in liquid nitrogen (LN) using the vitrification method. Seeds from 3-month-old pods were sufficiently dehydrated in 2 ml cryotubes filled with highly concentrated vitrification solution (PVS2) at 25 +/- 2 degree C for 50 min. The seeds were then rapidly plunged into LN. After rapid warming, the PVS2 solution was replaced with 0.5 ml of 1.2M sucrose in modified Vacin and Went (1949) (VW) solution and kept at 25 +/- 2 degree C for 20 min prior to transfer on VW agar medium. About 62% of cryopreserved seeds treated with PVS2 solution were able to develop into normal seedlings while without that treatment there was no survival. This vitrification protocol appears to be a promising technique for the cryopreservation of some Thai orchid germplasm 相似文献
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The droplet-vitrification protocol, a combination of droplet-freezing and solution-based vitrification was applied for cryopreserving garlic bulbil primordia. The highest survival and regeneration percentages of cryopreserved primordia (90.1 to 95.0 percent and 82.7 to 85.0 percent, respectively) were achieved after preculture for 2-4 days at 10 degree C on solid medium with 0.1 - 0.3 M sucrose, loading for 50 minutes in liquid medium with 2 M glycerol + 0.5 M sucrose, dehydration with PVS3 vitrification solution for 90-150 min, cooling primordia in 5 microl droplets of PVS3 vitrification solution placed on aluminum foil strips by dipping these strips in liquid nitrogen, warming them by plunging the foil strips into pre-heated (40 degree C) 0.8 M sucrose solution for 30 s and further incubation in the same solution for 30 minutes. The optimized droplet-vitrification protocol was successfully applied to bulbil primordia of five garlic varieties originating from various countries and to immature bulbils of two vegetatively propagated Allium species, with regeneration percentages ranging between 77.4 - 95.4 percent. 相似文献
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An experimental investigation was conducted to explore the characteristics of microscopic boiling induced by firing a microsecond pulsed laser beam on a thin platinum (Pt) film that immerged in the liquid nitrogen (LN2) cryostat. High-speed photography aided by a high-voltage lighting system was employed to visually observe the bubble formation and the dynamical boiling process of LN2. A rapid transient temperature-measuring system was designed to record the temperature evolution of the heating surface. Explosive boiling, characterized by bubble cluster, was observed within LN2 at the early stage of laser heating, and conventional boiling followed after a certain time. The transition time, therefore, was introduced for separating these two different boiling modes. The temperature of Pt film rose sharply to its maximum during laser pulse, with a very high rising rate of about 107 K/s, and then dropped rapidly after laser irradiation. A model of bubble cluster was proposed to describe the explosive boiling heat transfer, and the latent heat released by bubble collapse in explosive boiling was explored as an important mechanism considerably influencing the boiling heat transfer. 相似文献
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Wetting kinetics, kinematics, and cooling performance of a polymer–salt hybrid quenchant were investigated. The rewetting phenomenon for brine, water, polymer, and polymer–salt hybrid solutions was characterized as rapid uniform, fast non-uniform, slow uniform, and fast uniform processes, respectively. A dimensionless rewetting time was proposed to assess the nature of the wetting front. The hybrid quenchant showed higher heat transfer during vapor and transition boiling and lower heat transfer during nucleate boiling and convective cooling. The presence of salt in the hybrid solution resulted in early destabilization of the vapor film and an increase in wetting front velocity and rewetting temperature. The polymer constituent delayed the rewetting phenomenon. 相似文献