ToF-SIMS and other surface spectroscopies applied to the study of ancient artifacts: Preliminary investigation of a tetradrachm of Claudius
Why this work is in the frame
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Bibliographic record
Abstract
A group of ancient coins is among the Diniacopoulos collection of Central and Eastern Mediterranean antiquities housed at Queen's University. At first glance, nine coins in the collection appear to be billon tetradrachms minted in Alexandria, Egypt, dating to the period of the Emperor Claudius (41–54 AD). On the obverse, there is a portrait of the Emperor Claudius, on the reverse his wife Messalina is holding their two children. A closer examination reveals, however, that each of these coins weighs substantially less than the majority of specimens belonging to the same issues. All of the coins appear to have silver-rich plated surfaces with copper-rich cores. Questions are raised, therefore, about their authenticity and methods of manufacture. The surfaces display a variety of corrosion products, some of which may also indicate past restoration treatments. A single coin was selected for time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and energy dispersive x-ray analysis (EDX) analyses to investigate the viability of utilizing these combined techniques in the study of ancient coins. In order to gain information on the composition and distribution of the various chemical components present at the surface and into the bulk, it is necessary to profile into the sample, which by definition is destructive. Thus, it is important to identify areas of interest for further analysis so that the amount of damage can be minimized while maximizing the information obtained. To accomplish this, large area imaging ToF-SIMS has been performed using the stage-raster option in an IonTOF ToF-SIMS V. Bi3++ primary ions were used to map the surface and the positive secondary ion distribution images were obtained. Because of the varying topography of the sample, delayed onset of the generated secondary ion had to be used. Four areas were identified for further analysis, namely: (1) a Ag rich (minimal Cu content) area; (2) an area showing the presence of both Cu and Ag; (3) an area displaying visibly different surface characteristics, and finally, (4) a Cu rich (minimal Ag content) area. Chemical composition was obtained from these areas using XPS. To obtain further (nondestructive) depth information, EDX images were obtained, which would arise from a deeper sampling depth. In this case Ag was seen to be more dominant except for region (4). This implies a Cu enrichment at the surface as observed by the ToF-SIMS except for region (1). In this paper, the results of depth profiles in the bulk of the chosen areas are presented in order to ascertain the distribution of the various chemical components. This will allow future investigation on how the coins were manufactured.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it