This Volume, the last of the series, is devoted to water in its metastable forms, especially at sub-zero temperatures. The past few years have wit nessed an increasing interest in supercooled water and amorphous ice. If the properties of liquid water in the normal temperature range are already eccentric, then they become exceedingly so below the normal freezing point, in the metastable temperature range. Water can be supercooled to -39°C without too much effort, and most of its physical properties show a re markable temperature dependence under these conditions. Although ade quate explanations are still lacking, the time has come to review available knowledge. The study of amorphous ice, that is, the solid formed when water vapor is condensed on a very cold surface, is of longer standing. It has achieved renewed interest because it may serve as a model for the liquid state. There is currently a debate whether or not a close structural relation ship exists between amorphous ice and supercooled water. The nucleation and growth of ice in supercooled water and aqueous solutions is also still one of those grey areas of research, although these topics have received considerable attention from chemists and physicists over the past two decades. Even now, the relationships between degree of supercooling, nucleation kinetics, crystal growth kinetics, cooling rate and solute concentration are somewhat obscure. Nevertheless, at the empirical level much progress has been made, because these topics are of considerable importance to biologists, technologists, atmospheric physicists and gla ciologists.

The frozen-hydrated specimen is the principal element that unifies the subject of low temperature microscopy, and frozen-hydrated specimens are what this book is all about. Freezing the sample as quickly as possible and then further preparing the specimen for microscopy or microanalysis, whether still embedded in ice or not: there seem to be as many variations on this theme as there are creative scientists with problems of structure and composition to investigate. Yet all share a body of com mon fact and theory upon which their work must be based. Low-Temperature Micros copy and Analysis provides, for the first time, a comprehensive treatment of all the elements to which one needs access. What is the appeal behind the use of frozen-hydrated specimens for biological electron microscopy, and why is it so important that such a book should now have been written? If one cannot observe dynamic events as they are in progress, rapid specimen freezing at least offers the possibility to trap structures, organelles, macro molecules, or ions and other solutes in a form that is identical to what the native structure was like at the moment of trapping. The pursuit of this ideal becomes all the more necessary in electron microscopy because of the enormous increase in resolution that is available with electron-optical instruments, compared to light optical microscopes.

Advances in Low-Temperature Biology

Recent advances in the imaging technique electron microscopy (EM) have improved the method, making it more reliable and rewarding, particularly in its description of three-dimensional detail. Cellular Electron Microscopy will help biologists from many disciplines understand modern EM and the value it might bring to their own work. The book's five sections deal with all major issues in EM of cells: specimen preparation, imaging in 3-D, imaging and understanding frozen-hydrated samples, labeling macromolecules, and analyzing EM data. Each chapter was written by scientists who are among the best in their field, and some chapters provide multiple points of view on the issues they discuss. Each section of the book is preceded by an introduction, which should help newcomers understand the subject. The book shows why many biologists believe that modern EM will forge the link between light microscopy of live cells and atomic resolution studies of isolated macromolecules, helping us toward the goal of an atomic resolution understanding of living systems. - Updates the numerous technological innovations that have improved the capabilities of electron microscopy - Provides timely coverage of the subject given the significant rise in the number of biologists using light microscopy to answer their questions and the natural limitations of this kind of imaging - Chapters include a balance of "how to", "so what" and "where next", providing the reader with both practical information, which is necessary to use these methods, and a sense of where the field is going

Water is recognized as being an important factor in numerous pheno mena connected with the quality of food. For instance, it plays a part in the textural properties of several commodities. Moreover, water is an essential parameter determining the behaviour of food products in the course of many processing operations : on water, will depend the amount of energy necessary for freezing or dehydrating the product; water will strongly influence the evolution of physical, chemical and biochemical phenomena taking place in the product during processing operations such as heating, drying, etc. Water will also influence the same reactions, as well as the activity of microorganisms, during the storage of food products under various conditions. As a result, all aspects of quality - sensory, nutritional and hygienic properties of the food - will be affected. In all these circumstances, the water content of a product is obviously an important factor, but equally important may be the physical properties of this water, such as its thermodynamic activity and its mobility. Actual ly, the concept of water activity (a ) is now widely used by the food industry and in the legislation of sever')¥l countries. The idea of a small, international meeting devoted to a synthetic review and discussion of knowledge on these various matters, was first developed by Dr. R. B.