Images frozen in time Freezing processes involving multiple phases are common, as seen in the zone refining used to remove impurities from a crystal through the heating of a narrow region. However, it is difficult to visualize the processes as they happen. Dedovets et al. studied the freezing of an oil-in-water emulsion and the interaction of the oil droplets with the leading edge of the freezing water. In situ visualization of the freezing front was achieved through confocal microscopy of samples on a moving sample holder. The authors tracked the effects of solution concentration on the droplet positions and observed premelting at the interface of the droplets by using fluorescence markers. Science, this issue p. 303 Confocal microscopy allows for the visualization of the movement of oil droplets away from a freezing interface. The interaction of objects with a moving solidification front is a common feature of many industrial and natural processes such as metal processing, the growth of single crystals, the cryopreservation of cells, or the formation of sea ice. Interaction of solidification fronts with objects leads to different outcomes, from total rejection of the objects to their complete engulfment. We imaged the freezing of emulsions in five dimensions (space, time, and solute concentration) with confocal microscopy. We showed that the solute induces long-range interactions that determine the solidification microstructure. The local increase of solute concentration enhances premelting, which controls the engulfment of droplets by the front and the evolution of grain boundaries. Freezing emulsions may be a good analog of many solidification systems where objects interact with a solidification interface.

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具有溶质效应的冷冻乳液的五维成像

及时冻结的图像 涉及多相的冻结过程很常见，如用于通过加热狭窄区域从晶体中去除杂质的区域精炼中所见。但是，很难在过程发生时对其进行可视化。德多维茨等人。研究了水包油乳液的冻结以及油滴与冻结水前缘的相互作用。冷冻前沿的原位可视化是通过移动样品架上样品的共聚焦显微镜实现的。作者跟踪了溶液浓度对液滴位置的影响，并通过使用荧光标记观察了液滴界面处的预熔化。科学，这个问题 p。303 共聚焦显微镜允许观察油滴远离冻结界面的运动。物体与移动凝固前沿的相互作用是许多工业和自然过程的共同特征，例如金属加工、单晶生长、细胞冷冻保存或海冰的形成。凝固前沿与物体的相互作用会导致不同的结果，从完全拒绝物体到完全吞没物体。我们使用共聚焦显微镜在五个维度（空间、时间和溶质浓度）对乳液的冷冻进行了成像。我们表明，溶质会引起决定凝固微观结构的长程相互作用。溶质浓度的局部增加增强了预熔，从而控制了前沿对液滴的吞没和晶界的演化。