Artefacts analysis

The corrosion scales on the archaeological artefacts have been shown to consist primarily of siderite (FeC03) visible as large yellow-brownish crystals on the surface of some of the artefacts. Analysis of cross-sections of a few artefacts also showed that the inner corrosion layers consisted of siderite with some magnetite or maghemite. Importantly, only very low contents of sulfur were found, indicating that corrosion by sulfate-reducing bacteria is not a problem at this site. Siderite was also found on modern iron samples that had been exposed for a few years in the soil at Nydam. 

Artefact analysis is a huge topic in its own right, and no more than a very cursory glance at it is possible here. Two different forms of artefact will be considered in very broad outline, to illustrate two quite different errors that can occur. These are those arising from slice selection problems, and those due to... 

In any form of analysis it is important to determine the integrity of the system and confirm that artefacts are not produced as a by-product of the analytical procedure. This is particularly important in enantiomeric analysis, where problems such as the degradation of lactone and furanon species in transfer lines has been reported (40). As chromatography unions, injectors, splitters, etc. become more stable and greater degrees of deactivation are possible, problems of this kind will hopefully be reduced. Some species, however, such as methyl butenol generated from natural emissions, still remain a problem, undergoing dehydration to yield isoprene on some GC columns. 

Keller, H. R. and Massart, D. L., Artefacts in Evolving Factor Analysis-Based Methods for Purity Control in Liquid Chromatography with Diode-Array Detection, Ana/yt/ca Chimica Acta 263, 1992, 21-28. 

Fig. 31.15. Scree-plot, representing the residual variance V as a function of the number of factors r that has been extracted. The diagram is based on a factor analysis of Table 31.2 after log double-centering. A break point occurs after the second factor, which suggests the presence of only two structural factors, the residual factors being attributed to noise and artefacts in the data.

Cluster analysis (which is covered extensively in Chapter 30) can be performed on the factor scores of a data table using a reduced number of factors (Section 31.1.4) rather than on the data table itself. This way, one can apply cluster analysis on the structural information only, while disregarding the noise or artefacts in the data. The number of structural factors may be determined by means of internal... 

If thick samples are placed in the specimen chamber for analysis, the particles are slowed down and eventually stopped in the sample, so the calculation of the X-ray yield and their absorption is more complicated. Some objects may be too large to be placed in the specimen chamber, in which case the external beam technique is employed. The particle beam passes through a window at the end of the beam-line into the air where an object of any size (e.g. an archaeological artefact) may be analyzed. 

For the analysis of large objects which cannot be placed within the irradiation chamber it is possible take the particle beam into the ambient air through a thin window at the end of the beam line. In this way any type of object can be analysed -for example paintings and archaeological artefacts. 

Gratuze, B., J. N. Barrandon, K. A1 Isa, and M. C. Cauvin (1993), Non-destructive analysis of obsidian artefacts using nuclear techniques Investigation of provenance of Near Eastern artefacts, Archaeometry 35,11-21. 

Williams-Thorpe, O., S. E. Warren, and J. G. Nandis (1997), Characterization of obsidian sources and artefacts from central and eastern Europe, using instrumental neutron activation analysis, in Korek, J. (ed.), Proc. Int. Conf. Lithic Raw Material Characterization, Budapest and Siimeg, 1996, Budapest. 

In strongly coupled systems, it is not possible to eliminate chemical shifts by refocusing nor is it possible to describe the evolution in terms of an effective Hamiltonian.44 A 90° or a 180° pulse leads to coherence transfer between various transitions, and a multitude of new effective precession frequencies may appear in the F1 dimension. A detailed analysis shows artefacts resulting of strong coupling induced by the 180° pulse applied on the H channel can be efficiently removed by applying a LPJF before acquisition.42 Likewise, artefacts present in HMBC with a terminal LPJF are suppressed by an LPJF in the beginning of the sequence as in conventional HMBC. 

Ham M., Bartl J., Jacko V., Multispectral analysis of Cultural Heritage artefacts, Measurement Science Review, Volume 3, Section 3 (2003). 

Chapters 3 6 deal with direct mass spectrometric analysis highlighting the suitability of the various techniques in identifying organic materials using only a few micrograms of samples. Due to the intrinsic variability of artefacts produced in different places with more or less specific raw materials and technologies, complex spectra are acquired. Examples of chemometric methods such as principal components analysis (PCA) are thus discussed to extract spectral information for identifying materials. 

In this connection, it must also be borne in mind that the deoxyribonucleic acids subjected to analysis have probably not been homogeneous. Deoxyribonucleic acids have been fractionated by making use of their different solubilities in normal saline,186 by extracting thymus nucleo-his-tone with sodium chloride solutions of increasing concentration,187 by ion-exchange,187 and also by adsorption of the polynucleotide onto histone immobilized on a kieselguhr support.123 It is possible, however, that these are artefacts, since it has been shown that deoxyribonucleic acid fractions extracted from calf-thymus nucleohistone may or may not vary in composition according to the previous treatment of the material.188... 

Hughes, M.J., Northover, J.P. and Staniaszek, B.E.P. (1982). Problems in the analysis of leaded bronze alloys in ancient artefacts. Oxford Journal of Archaeology 1 359-363. 

Walker, C., Hancock, R.G.V., Aufreiter, S., Latta, M.A. and Garrad. C. (1999). Chronological markers Chemical analysis of copper-based trade metal artefacts from Petun sites in southern Ontario, Canada. In Metals in Antiquity, ed. Young, S.M.M., Pollard, A.M., Budd, P. and Ixer, R.A., BAR International Series 792, Archaeopress, Oxford, pp. 317-325. 

Glascock, M.D., Spalding, T. G., Biers, J. C., and Corman, M.F. (1984). Analysis of copper-based metallic artefacts by prompt gamma-ray neutron activation analysis. Archaeometry 26 96-103. 

---