Remedy for fictive negative pressures in biphasic finite element models of the intervertebral disc during unloading
Bibliographic record
Abstract
Previous biphasic finite element studies investigated the temporal response of a spinal segment under rather simplified loading conditions with no attention to unloading and recovery phases. Employment of existing constitutive relations in porous media yields rather large suction-type pore pressures in the disc as the load suddenly disappears. Such negative pressures are absent in vivo and are hence fictive. The aim of this study was to search for remedies to avoid the computation of negative pressures upon unloading. Partial saturation for the disc or a rest load (RL) higher than 400 N totally eliminated the negative pressures. Decreasing the voids ratio (VR) also led to a reduced negative pressure. When defining a partial saturated disc or using a lower VR in combination with a boundary pressure of 0.25 MPa and a RL of 350 N, no negative pressure was calculated. It appears that the constraint of full saturation and a high mobile fluid fraction of the disc tissues along with inadequate tissue properties are the likely causes of negative pressures during unloading.
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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 | 0.003 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| 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".