Organisms and Ice Formation

Although it might at first seem surprising, this research on polar fish has attracted the attention of ice cream manufacturers. Premium-quality ice cream is smooth it does not have large ice crystals 

The removal of soot from smoke is another example of the coagulation of a colloid. When smoke is passed through an electrostatic precipitator (Fig. 17.24), the suspended solids are removed. The use of precipitators has produced an immense improvement in the air quality of heavily industrialized cities. 

The Cottrell precipitator installed in a smokestack. The charged plates attract the colloidal particles because of their ion layers and thus remove them from the smoke. 

These questions are designed to he considered hv groups of students in class. Often these questions work well for introducing a particular topic in class. 

Consider Fig. 17.8. According to the caption and picture, water is transferred from one beaker to another. 

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The threats posed by ice formation in the intracellular and extracellular fluids have favored selection in diverse types of organisms for mechanisms that either prevent the formation of ice or minimize the potential for enlargement of any small ice crystals that do form in the internal fluids. These mechanisms are under intense study, both because of their inherent interest to evolutionary and ecological physiol-... 

This table lists only hexagonal crystals and only the best known of these. Silver iodide in the form of smoke particles a few hundred angstroms in average diameter, for example, is commonly used to seed clouds and induce ice formation at temperatures —10 to — i5°C instead of the — 20°C more characteristic of natural nuclei. Many materials which are not hexagonal and some which bear no obvious relation to ice structure, such as certain organic materials, are also quite efficient nuclei. Extensive experimental... 

One potential solution to the dilemma is to find additives that can minimize the toxic effects of concentrated solutes, decrease the probability of internal ice formation, or decrease the injurious consequences of ice formation. A number of substances have been found that do, in fact, protect some cells from low-temperature injury p], the most effective being glycerol, dimethyl sulfoxide, polyvinylpyrrolidone, and a variety of sugars but at present we cannot say with any certainty by which of the three mechanisms they protect, or whether they protect by some entirely different mechanism. We do find, however, that their effectiveness seems to decrease with increasing size and complexity of the cell or organism. 

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