Hysteresis in Asphaltene Precipitation and Redissolution
Bibliographic record
Abstract
The precipitation and redissolution of asphaltenes from mixtures of Athabasca bitumen and n -heptane was measured over time in both air and nitrogen atmospheres at 23 °C. In air, it appears that oxidation of the bitumen increased the asphaltene yield for as long as the experiments were conducted; that is, for several months. When oxidation effects are excluded, asphaltene precipitation and redissolution both appear to reach steady state within 24 h. A hysteresis between asphaltene precipitation and redissolution was also observed in both atmospheres. The hysteresis was exaggerated in the air atmosphere due to oxidation effects. In both air and nitrogen atmospheres, complete reversibility was attained when the heptane-to-bitumen ratio was reduced to 1.5 cm 3 /g. The hysteresis is attributed to an energy barrier to asphaltene dissociation. As more heptane is added, the asphaltenes likely self-associate to higher apparent molar masses. When the heptane is removed, the asphaltenes may remain in the higher association state and hence precipitate to a greater extent than before at a given heptane-to-bitumen ratio. If the system is heated, the asphaltene yields return to their original values, indicating that the original association state can be restored.
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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 | 0.001 |
| 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) | 0.001 | 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 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".