Preservation, plant material

Searching a crime scene is a complex process (25), involving poHce, crime scene technicians, and forensic scientists. The procedure requires careful documentation, collection, and preservation of the evidence. Trace evidence (26) in criminal investigations typically consists of hairs (27,28) both natural and synthetic fibers (qv) (29,30), fabrics glass (qv) (31,32) plastics (33) sod plant material budding material such as cement (qv), paint (qv), stucco, wood (qv), etc (34), flammable fluid residues (35,36), eg, in arson investigations explosive residues, eg, from bombings (37,38) (see Explosives and propellents), and so on. 

Drying is an excellent way of preserving herbs many leaves and seeds keep their flavor well and, stored correctly, should last up to a year. Providing the ideal range of temperatures and ventilation for drying individual herbs is not easy in a domestic situation, and if you dry herbs at home you may find that the drying process results in some loss of flavor and color. Some herbs do not retain their flavor well when dried, and are best used fresh, or frozen. Check all the plant material carefully before you dry it and discard any parts that are diseased or damaged. 

Sulfur isotopic measurements can shed light on the origin of sulfur in coal. The 34S/32S ratio depends on the source of sulfur and the geologic processes involved during coal formation. For example, isotopic compositions are different for the two principal sources of sulfur in coal 1) the sulfur preserved from the precursor plant material, and 2) the sulfur derived from the bacterial reduction of dissolved sulfate in ambient waters. Plant assimilation of sulfur results in a slight depletion of 34S (4-4.5%c) relative to the 834S in the dissolved sulfate source (102.103). In contrast, the dissimilatory bacterial reduction of sulfate results in a large isotopic fractionation sulfide sulfur can be depleted as much as 60%o in the heavy isotope (89.104-106). 

Bauer (1999b) found that the alkamide, dodeca-2 ,4E,8Z, 1 OE/Z-tetra-enoic acid isobutylamide, level was influenced by the preparation method. Nonthermal preparations appeared to have slightly higher levels of the tested alkamide than thermally treated products. Thus, the drying process may not be the best method for preparing Echinacea products. Pressing of the plant material to obtain an expressed juice is a common preparation method however, preservation of the juice with ethanol is required. Direct ethanol extraction of the plant material can be used in place of the pressing operation. 

Figure 2.4.3 Comparison of different renewable energy pathways and carbon transfer schemes from carbohydrates, as well as their typical conditions. Here, preservation of combustion energy and the carbon efficiency (CE) of the transformation are compared. The combustion energy always concerns the complete side of the reaction equation. The sum formula of the coalified plant material is a schematic simplification.

Khat is purchased as bundles of dried and fresh leaves and buds. For transport purposes, it is usually wrapped in plastic bags or banana skins to preserve its moisture content - loss of activity is observed after 48 h if the plant material dries out. However, the drug can also be obtained as dried crushed leaves or in powdered form. These materials are either chewed or used to prepare an infusion which is drunk like tea. The major part of the pharmacological action is due to cathinone, which acts as a central nervous system (CNS) stimulant, promoting excitation, reducing the need to sleep and enhancing communication. 

After making a sample of a plant the procedures for preservation followed depend on various factors such as time, money, assistance available, etc. Them are two methods of preparing a herbarium specimen> directly drying in the field or provisionally preserving the material on alcohol and drying them later in the herbarium (wet method). 

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