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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.
Water Activity in Foods: Fundamentals and Applications is a one-of-a-kind reference text that brings together an international group of food scientists, chemists, and engineers to present a broad but thorough coverage of an important factor known to influence the attributes of foods – water activity. A team of experienced editors designed this book for lasting value as a sound introduction to the concept of water activity for neophytes and seasoned professionals in both academe and industry. Topics have been carefully selected to provide a comprehensive understanding of the mechanisms by which water activity influences the quality, shelf life, and safety of food products. Water Activity in Foods belongs on the shelves of all food science professionals for use in product development, quality control, and food safety. Students and newcomers to these areas will appreciate the instructional approach adopted by the experienced teachers and industry specialists who have contributed chapters to this comprehensive overview.
This book was developed from the papers presented at a symposium on "Water Relationships in Foods," which was held from April 10-14, 1989 at the 197th National Meeting of the American Chemical Society in Dallas, Texas, under the auspices of the Agricultural and Food Chemistry Division of ACS. The editors of this book organized the symposium to bring tagether an es teemed group of internationally respected experts, currently active in the field of water relationships in foods, to discuss recent advances in the 1980's and future trends for the 1990's. It was the hope of all these con tributors that this ACS symposium would become a memorable keystone above the foundation underlying the field of "water in foods. " This strong foundation has been constructed in large part from earlier technical conferences and books such as the four milestone International Symposia on the Properties of Water (ISOPOW I-IV), the recent IFT BasicSymposium on "Water Activity" and Penang meeting on Food Preservation by Maisture Control, as well as the key fundamental contributions from the classic 1980 ACS Symposium Series #127 on Water in Polymers, and from Felix Franks' famous seven-volume Comprehensive Treatise on Water plus five subsequent volumes of the ongoing Water Science Reviews. The objective of the 1989 ACS symposiumwas to build on this foun dation by emphasizing the most recent and maj or advanc.
A profound secret of nature hidden in ice water in a glass cup is revealed in this book. The author teaches a simple method for understanding the complex properties of water through the concept of polyamorphism. Polyamorphism is the existence of two kinds of liquid water, leading to a discontinuous transition between them. Currently, this two-water scenario is controversial in the scientific community because definitive experimental proof is difficult. However, a growing number of researchers believe there is adequate circumstantial evidence for the scenario. This introductory book focuses experimental thermodynamic data of liquid water, supercooled water, and amorphous solid water at various pressures and temperatures, and demonstrates how the two-water scenario initially evolved experimentally. The book explains the importance of polyamorphism in comprehending liquid water.