Freezing and drying methods

Clearly, if a rubber modified blend contains particles larger than the film thickness (about 1 /xm), the film cannot be representative of the bulk. For the study of craze tips and craze growth, a double tilting stage was used to obtain stereo pairs of the craze tip [396]. 

The microstructure observed for thick films shows fibrils, about 4-10 nm in diameter for polystyrene, in agreement with SAXS measurements on the crazes in the bulk polymer. Very thin films of polystyrene (100 nm) show modification in the craze structure as there is no plastic restraint normal to the film [397]. Deformation zones have also been studied in polycarbonate, polystyrene-acrylonitrile and other polymers [398]. Crazes in thermosets can be studied in thin films spun onto NaCl substrates which can be washed away when the film has been cured. Mass thickness measurements are difficult to make in radiation sensitive materials that is why most TEM work has been done on polystyrene and least on PMMA. After developing the techniques described above for TEM Donald and Kramer [398] applied similar methods in optical microscopy to study radiation sensitive materials and the kinetics and growth of deformation zones. Thin films were strained on grids in situ in a reflecting OM. Change of interference color, which depends on the film thickness, was a very sensitive method for observing film deformation. 

Generally, the methods described here involve special drying of the specimen or some kind of freezing technique. Materials as diverse as emul- 

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Tea has encountered increasing importance. The various concentration and drying methods for tea are discussed by von Bomben, Bmin, Thijssen and Merson ]25]. With black tea, it is possible to dry the pure extract. The freeze-drying process is exhaustively treated in Deicke [26]. 

Water sorption of freeze-dried and spray-dried maferials leveled off wifh various amounts of water contents, depending on RVP, and drying methods. 

Removal of water for processing/storage purposes either by conventional dehydration or freezing and drying alters the native functional properties of foods. Simple, rapid, and accurate methods for moisture determination in raw, processed, and stored food products are used to know the nutritive value of food products. A homogenous food sample should be prepared using a nmnber of electrical/mechanical... 

The resuspended and formulated Fraction II precipitate normally contains some aggregated IgG and trace substances that can cause hypotensive reactions in patients, such as the enzyme prekail ikrein activator (186). These features restrict this type of product to intramuscular adininistration. Further processing is required if products suitable for intravenous adininistration are required. Processes used for this purpose include treatment at pH 4 with the enzyme pepsin [9001-75-6] being added if necessary (131,184), or further purification by ion-exchange chromatography (44). These and other methods have been fiiUy reviewed (45,185,187,188). Intravenous immunoglobulin products are usually suppHed in the freeze-dried state but a product stable in the solution state is also available (189). 

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