Polarization Dependence of Aragonite Calcium L-Edge XANES Spectrum Indicates<i>c</i>and<i>b</i>Axes Orientation
Bibliographic record
Abstract
Calcium carbonate minerals are frequently found in biomineral structures and are the predominant mineral in invertebrates. While there are several calcium carbonate polymorphs, aragonite and calcite are the two most commonly found in biogenic systems. Currently, calcium L-edge X-ray absorption near-edge structure (XANES) spectra are used to distinguish between different calcium carbonate polymorphs, including calcite and aragonite, while oxygen and carbon K-edge XANES spectra are often used to determine the c axis orientation of a given calcium carbonate crystal. By doing a full analysis of the calcite and aragonite calcium L-edge XANES spectrum for both geologic and biogenic systems, we were able to show that aragonite has a polarization-dependent peak while calcite does not. Analysis based on both multiplet models and density functional calculations show how the polarization dependence arises from directional bonds between the calcium and oxygen atoms within aragonite. These data not only enable an interpretation of the aragonite calcium L-edge XANES spectrum but also the ability to determine the orientation of the c and b axes of aragonite crystals within a biomineral sample.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".