Freeze drying Health Dictionary

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Freeze Drying: From 2 Different Sources

A technique for ?xating specimens of tissue, involving a minimum of chemical and physical alteration. The histological specimen is immersed in a chemical, isopentane, which has been cooled in liquid air to a temperature just below 200 °C. This preserves the tissue instantly without large ice crystals forming – these would result in structural damage. The specimen is then dehydrated in a vacuum for three days, after which it can be examined using a MICROSCOPE.
Health Source: Medical Dictionary
Author: Health Dictionary
a method for the *fixation of histological specimens, involving a minimum of chemical and physical change. Specimens are immersed in isopentane cooled to –190°C in liquid air. This fixes the tissue instantly, without the formation of large ice crystals (which would cause structural changes). The tissue is then dehydrated in a vacuum for about 72 hours at –32.5°C.
Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Drying Herbs

Herbs should be harvested from unsprayed dust-free zones and spread out on racks or suitable fittings. Smaller batches may be hung in bunches. Rotting may set in if fresh herbs are left compressed in bags, baskets, etc. Never wash herbs before drying or place one above another. Turn or agitate daily. They should be dried in a well-ventilated room in the absence of excessive heat, sunlight or bright lights which may destroy the volatile oils of aromatic herbs. They should not be cut until thoroughly dried.

Only roots should be washed soon after lifting, and cut before drying into hardness. In a few cases drying of roots may be assisted by added heat. ... drying herbs

Freeze Etching

a technique for preparing specimens for electron microscopy. The unfixed tissue is frozen and then split with a knife and a layer of ice is sublimed from the exposed surface. The resultant image is thus not distorted by chemical fixatives.... freeze etching

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