共查询到20条相似文献,搜索用时 421 毫秒
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冷冻过程中洋葱细胞胞内冰晶的生长行为研究 总被引:1,自引:0,他引:1
细胞胞内冰的形成会导致严重的细胞损伤从而导致低温贮存中的诸多问题。生物组织保存前的预冷过程对胞内冰晶的形成具有重要影响。本文分别采用-1,-5,-10,-20,-50,-80℃/min的降温速率预冷洋葱表皮细胞至-7℃接种冰晶.采用高速摄像仪观察冰晶生长过程,发现了三种模式的胞内冰晶生长行为。模式A:细胞壁结晶后继续在边缘结晶;模式B:细胞壁结晶后,向中心扩散,横贯中心位置;模式C:中心首先结晶,扩散至细胞边缘。最后对三种不同过程的冰晶生长速率及细胞变形度进行了计算分析。 相似文献
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为研究微通道内冰晶生长的微观机理以便提出相应的防结冰措施,建立了微通道内结冰过程的相场模型,模型中引入了实际边界条件的影响(取为第三类边界条件),相场计算中采用随机方法生成晶核。基于有限差分法对相场模型进行了数值求解,对不同边界条件影响强度(以努塞尔数Nu表征)下冰晶生长过程进行了系统研究。研究结果表明:边界对微通道内的冰晶生长影响显著,Nu越大,微通道内冰晶生长第一阶段(冰晶未扩展到边界时)结晶速率越大,使得充分结晶(定义为结晶百分数达到80%)所需总时间越短;同时应在结冰初始阶段对其进行及时干预才能有效防止结冰。 相似文献
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The freezing of liquid water into ice was studied inside a gap of nanometer spacing under the control of electric fields and gap distance. The interfacial water underwent a sudden, reversible phase transition to ice in electric fields of 10(6) V m(-1) at room temperature. The critical field strength for the freezing transition was much weaker than that theoretically predicted for alignment of water dipoles and crystallization into polar cubic ice (>10(9) V m(-1)). This new type of freezing mechanism, occurring in weak electric fields and at room temperature, may have immediate implications for ice formation in diverse natural environments. 相似文献
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Berger WK 《Cryo letters》2004,25(2):139-146
Ice-cell interactions especially the question whether and how ice crystals invade tissues and organs during freezing were examined in small transparent organs (salivary glands) in which many structural details remained visible despite of freeze-induced cell darkening. In most glands no invasion of ice into the lumen was observed since ice dendrites stopped growing after touching the gland. Here I report that in rare cases a so far unknown type of ice crystals developed which aggressively pushed against cell membranes before invading the gland via paracellular pathways (septate junctions). Aggressive ice crystals were also observed within a salivary gland cell which deformed and finally invaded the nucleus. In cell strands it was observed that intracellular freezing is indeed a two-step event in which ice developed in cytoplasm several seconds before invading the nucleus. 相似文献
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有限厚度冻冰相变过程的传热研究 总被引:3,自引:0,他引:3
1前言确定相界面的瞬态位置是求解冻冰相变问题的重要部分。目前对于有限区域相变问题还没有可靠的精确解[1]。冻冰过程最简单分析方法是忽略固液两相的显热变化,建立相界面移动的准稳态传热关系式,近似预测固一液相变位置[2-4]。本文将考虑液、固相中显热的变化,对有限厚平板冻冰过程,采用精确解与积分解相结合的方法,分析冰层冻结过程中的固一液相界面、边界热流密度和贮入固、液相内的冷量随冻冰时间的变化规律。2物理一数学模型分析该研究的问题是一块贮冷板的两侧面直接与一个低温蒸发器直接接触,使贮冷板内冻冰贮冷。通常蒸发器… 相似文献
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《Current Applied Physics》2015,15(5):662-668
TiO2 films with ordered porous structure were prepared by freezing. By simply freezing wet TiO2 film on a cold copper plate, ice crystals could grow from bottom of film. Removing such ice crystals then led to ordered, micro-sized pores in the films. With assistance of scanning electron microscopy and N2 adsorption–desorption isotherms, micro-structural properties of the films were studied. Coarsening behavior of ice crystals was analyzed based on evolvement of the micro-structure. It was found that, both larger film thickness and longer freezing time were beneficial for the formation of ordered porous structure, which was caused by enhanced ice crystals growth. The films were then used to fabricate photoanode of dye sensitized solar cells, of which the photo-to-electric power conversion efficiency was evaluated. It was observed that, solar cell made of ordered porous TiO2 film came out with 13% larger photo-current density comparing to that made of conventional doctor blading method, which is due to the enhanced light scattering by the ordered porous structure. 相似文献
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Abstract Pressure release freezing (PRF) of an oil-in-water emulsion is studied. The characteristics of ice crystals as a function of freezing process is studied. 相似文献
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The freezing and melting process of a small water droplet on a superhydrophobic cold surface was investigated using the Laser Induced Fluorescence (LIF) technique. The superhydrophobic surface was prepared using a sol-gel method on a red copper test plate. From the obtained fluorescence images, the phase transition characteristics during the freezing and melting process of a water droplet were clearly observed. It was found that, at the beginning of the droplet freezing process, liquid water turned into ice at a very fast rate. Such phase transition process decreased gradually with time and the volume of frozen ice approached a constant value at the end of the icing process. In addition, the freezing time was found to reduce with the decrease of the test plate temperature. Besides, when the test plate temperature is relatively high, the effect of droplet volume on the freezing time is very significant. Over all, we provide some tentative insights into the microphysical process related to the icing and melting process of water droplets. 相似文献
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Ice crystallisation in crosslinked dextran (Sephadex) gels was studied by the method of two-dimensional X-ray diffraction (XRD) in combination with the simultaneous measurement of differential scanning calorimetry (DSC). With a Sephadex G25 gel where an exotherm due to ice crystallisation is observed in the DSC rewarming trace, it was indicated by the XRD pattern that small ice crystals less than approximately 10 microns in diameter are readily formed during freezing, and that the endothermic trend prior to the exotherm is not due to the glass transition but due to the melting of the small ice crystals. Moreover, the diffraction pattern observed with frozen Sephadex gels depended on the density of crosslink indicating that ice crystals of different size and dimension are formed in the gels. 相似文献