Asphaltene Nanoaggregates Studied by Centrifugation
Bibliographic record
Abstract
The colloidal structure of asphaltenes impacts various physical properties and is important to characterize. Previously, in both laboratory and oilfield studies, asphaltenes have been shown to form nanoaggregates. In addition, previous work has shown that asphaltenes exhibit a critical nanoaggregate concentration (CNAC) in toluene in the range of 50−150 mg/L. In this study, centrifugation is used to prove a major change of asphaltene aggregation at the CNAC concentration, thereby corroborating previous results. Collection of these nanoaggregates by centrifugation validates there existence. The nanoaggregate size is found to be ∼2.5 nm, which is compatible with corresponding previous determinations from gravitational gradients. Asphaltene monomers are seen to be small (<1.5 nm), confirming previous diffusion measurements and corroborating the now common view that asphaltene molecular size is rather small. A two-component, monomer and nanoaggregate, phase equilibrium model is shown to treat the primary features of the data; nevertheless, shortcomings of this model are discussed. These centrifugation experiments are simple and we believe compelling confirmation of the asphaltene CNAC in toluene.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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".