Artifact preservation

Electrochemical cells play important roles in both the purification and the preservation of metallic materials. Redox reactions are used throughout the chemical industry to extract metals from their ores. However, redox reactions also corrode the artifacts that industry produces. What redox reactions achieve, redox reactions can destroy. 

FIGURE 12.20 In the cathodic protection of a buried pipeline or other large metal construction, the artifact is connected to a number of buried blocks of metal, such as magnesium or zinc. The sacrificial anodes (the magnesium block in this illustration) supply electrons to the pipeline (the cathode of the cell), thereby preserving it from oxidation. 

Although this collision rule conserves momentum and energy, in contrast to the original version of MPC dynamics, phase space volumes are not preserved. This feature arises from the fact that the collision probability depends on AV so that different system states are mapped onto the same state. Consequently, it is important to check the consistency of the results in numerical simulations to ensure that this does not lead to artifacts. 

Andreani, C., V. C. Nunziante, G. Cinque, G. Gorini, A. Granelli, and M. Martini (eds.) (2006), Atomic and nuclear techniques for the diagnostics and the preservation of archaeological artifacts,. Neutron Res. 14(1), Special Issue. 

Walker, R. (1982), Corrosion and preservation of bronze artifacts, /. Chem. Educ. 59, 943. 

The potential for the preservation of lipids is relatively high since by definition they are hydrophobic and not susceptible to hydrolysis by water, unlike most amino acids and DNA. A wide range of fatty acids, sterols, acylglycerols, and wax esters have been identified in visible surface debris on pottery fragments or as residues absorbed into the permeable ceramic matrix. Isolation of lipids from these matrices is achieved by solvent extraction of powdered samples and analysis is often by the powerful and sensitive technique of combined gas chromatography-mass spectrometry (GC-MS see Section 8.4). This approach has been successfully used for the identification of ancient lipid residues, contributing to the study of artifact... 

Edwards, R. (1996). The effects of changes in groundwater geochemistry on the survival of buried metal artifacts. In Preserving Archaeological Remains In-Situ, eds. Corfield, M., Hinton, P., Nixon, T., and Pollard, A. M., London, Museum of London Archaeology Service, pp. 86-92. 

To obtain tissue preparations whose constituents were maintained as closely as possible to their state in vivo, the material had to be fixed, i.e. the enzymes inactivated so that cell structures were instantaneously preserved, an almost unattainable ideal. Formalin was the favored fixative, but others (e.g. picric acid), were also employed. Different methods of fixation caused sections to have different appearances. Further artifacts were introduced because of the need to dehydrate the preparations so that they could be stained by dyes, many of which were lipid-soluble organic molecules. Paraffin wax was used to impregnate the fixed, dehydrated material. The block of tissue was then sectioned, originally by hand with a cut-throat razor, and later by a mechanical microtome. The sections were stained and mounted in balsam for examination. Hematoxylin (basophilic) and eosin (acidophilic) (H and E staining) were the commonest stains, giving blue nuclei and pink cytoplasm. Eosinophils in the blood were recognized in this way. 

It is helpful to know the chemistry of fixatives in order to understand their action and avoid artifacts (4). Most commonly studied antigens are either proteins or carbohydrates. Many of these molecules are soluble in aqueous solutions and need to be fixed in place in cells. Insoluble antigens also need to be structurally preserved (/). All chemical fixatives will cause chemical and conformational changes in the protein structure of cells with lesser changes noted for carbohydrate antigens (5). Secondary and tertiary structures of proteins are the most important for eliciting antigenicity and chemical fixatives usually disturb these conformations (3). 

Although supportive of a sarcoma diagnosis, lack of expression of the antibodies may be secondary to a fixation or preservation artifact as well as dedif-... 

Although platinum occurs as grains and nuggets in the alluvial sands of many rivers, there is only slight evidence of its use by ancient peoples. The pre-Columbian Indians, however, near the place now known as La Tolita, Esmeraldas, Ecuador (39), produced white alloys of gold and platinum, from which they made many little artifacts, some of which are now preserved in the University of Pennsylvania Museum in Philadelphia and the Danish National Museum in Copenhagen. Since plati-... 

While it is often stated that few textiles survive from archaeological sites in eastern North America, some examples with preserved features have been uncovered. These materials have survived burial conditions because of the peculiarities of the burial context or due to some feature of their composition that made them less susceptible to microbial degradation. These preserved materials often are very fragile handling them results in the loss of small particulate material. Rather than discarding this particulate, collection and analysis may provide some clues to the content and condition of the artifact. 

The above example shows how we use SFC to furnish accurate quantitative data. In addition, SFC is used to insure that desorption/ionization methods do not yield artifacts particularly when analyzing reactive monomers. Under K+IDS, the sample under study may be exposed to high temperatures giving rise to decomposition products or the re-association of thermal fragments. Using SFC, the sample integrity is preserved. 

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