Coins analysis

The work of Ambrosino and colleagues has already been mentioned. The early volumes of the journal Archaeometry (first published in 1958) also contain some exploratory research on the application of NAA to the problem of coin analysis. Kraay and Emeleus at Oxford realized that NAA was a very practical solution to one of the requirements of ancient coin analysis, and that was, for the rare and most valuable specimens at least, that it be totally non-destructive. They also quickly discovered another benefit because neutrons activated the whole coin, they provided a bulk analysis as opposed to x-ray fluorescence, which gave only the surface composition. They found that a Corinthian coin, thought to be silver, was in fact silver-plated over a copper core. For precise NAA studies, the self absorption of neutrons in solid gold coins requires a substantial correction to the flux. Self absorption in silver, less serious has also been investigated (see below). 

As a consequence of this observation, the essential dynamics of the molecular process could as well be modelled by probabilities describing mean durations of stay within different conformations of the system. This idea is not new, cf. [10]. Even the phrase essential dynamics has already been coined in [2] it has been chosen for the reformulation of molecular motion in terms of its almost invariant degrees of freedom. But unlike the former approaches, which aim in the same direction, we herein advocate a different line of method we suggest to directly attack the computation of the conformations and their stability time spans, which means some global approach clearly differing from any kind of statistical analysis based on long term trajectories. 

Thermal neutron activation analysis has been used for archeological samples, such as amber, coins, ceramics, and glass biological samples and forensic samples (see Forensic chemistry) as weU as human tissues, including bile, blood, bone, teeth, and urine laboratory animals geological samples, such as meteorites and ores and a variety of industrial products (166). 

The concept of property space, which was coined to quanhtahvely describe the phenomena in social sciences [11, 12], has found many appUcahons in computational chemistry to characterize chemical space, i.e. the range in structure and properhes covered by a large collechon of different compounds [13]. The usual methods to approach a quantitahve descriphon of chemical space is first to calculate a number of molecular descriptors for each compound and then to use multivariate analyses such as principal component analysis (PCA) to build a multidimensional hyperspace where each compound is characterized by a single set of coordinates. 

The reluctance of museum curators and collectors to allow permanent damage to antiquities was, until not long ago, the main reason for the small amount of analytical work done on ancient coins. This was understandable since performing chemical analysis required removing a sample from the coin or damaging its surface, which meant either the destruction or defacement of, at least, a portion of a coin. More recently, however, a number of nondestructive methods of analysis such as neutron activation, X-ray fluorescence, and some techniques of surface analysis have been successfully applied to obtain information about ancient coins and the people and societies involved in their production (Carter 1993 Barrandon et al. 1977). 

Barrandon, J. N., J. P. Callu, and C. Brenot (1977), The analysis of Constantinian coins by non-destructive californium analysis, Archaeometry 19,173-186. 

Beck, L., S. Bosonnet, S. Reveillon, D. Eliot, and F. Pilon (2004), Silver surface enrichment of silver-copper alloys A limitation for the analysis of ancient silver coins by surface techniques, Nuclear Instrum. Meth. (B) 226(1-2), 153-162. 

A definition of Chemometrics is a little trickier of come by. The term was originally coined by Kowalski, but nowadays many Chemometricians use the definition by Massart [4], On the other hand, one compilation presents nine different definitions for Chemometrics [5, 6] (including What Chemometricians do , a definition that apparently was suggested only HALF humorously ). But our goal here is not to get into the argument over the definition of the term, so for our current purposes, it is convenient to consider a perhaps somewhat simplified definition of Chemometrics as meaning multivariate methods of data analysis applied to data of chemical interest . 

In Britain, the term archaeometry was coined in the early 1950s by Christopher Hawkes in Oxford to describe the increased emphasis on dating, quantification and physicochemical analysis of archaeological materials. A journal with the same name was launched in 1958 and textbooks by Martin Aitken (1961) and Mike Tite (1972) illustrated the full potential of emerging applications. In 1974, the first volume of another periodical dedicated to scientific work in archaeology (Journal of Archaeological Science) was published. 

Emeleus, V.M. (1958). The technique of neutron activation analysis as applied to trace element determination in pottery and coins. Archaeometry 1 6-15. 

Although quantification of the elements present in the y spectrum can in theory be achieved from first principles using the equation given above, in practice uncertainties in the neutron capture cross-section and variations in the neutron flux within the reactor mean that it is better to use standards. These standards must be included in each batch of samples irradiated in order to account for variations in neutron flux inside the reactor. For analysis of minor and trace elements calibration is easier than with other analytical methods provided that the major element composition remains reasonably constant, as the y ray intensity is proportional to concentration over a very wide range of concentrations. However, for analysis of major elements, e.g., silver in silver coins, the relationship between intensity and concentration is more complex, due to progressive absorption of neutrons as they pass through the specimen. In such cases y ray intensity will also depend on the thickness of the sample and therefore specialized calibration methods are required (Tite 1972 277). 

Gordus, A. A. (1967). Quantitative non-destructive neutron activation analysis of silver in coins. Archaeometry 10 78-86. 

Linke, R. and Schreiner, M. (2000). Energy dispersive X-ray fluorescence analysis and X-ray microanalysis of medieval silver coins - an analytical approach for non-destructive investigation of corroded metallic artifacts. Mikrochimica Acta 133 165-170. 

Three dimensional X-ray diffraction analysis has been employed to elucidate the molecular and crystal structure of Copper Phthalocyanine Blue ((3-modifica-tion). In all modifications, the planar and almost square phthalocyanine molecules are arranged like rolls of coins, i.e., in one dimensional stacks. The modifications vary only in terms of how these stacks are arranged relative to each other. One important aspect is the angle between staple axis and molecular plane. The a-phase features an angle of 24.7°, while the stacks in the -modification deviate by as much as 45.8° [13]. 

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