Relative changes of the biomechanical properties of living rabbit brain tested under controlled physiologic conditions with stress-relaxation indentation
Bibliographic record
Abstract
Mechanical testing of living brain with control or measurement of all potential sources of variability is difficult and not often or consistently performed. The primary objective of the current work is to compare mechanical properties of the living rabbit brain across relatively high and low groupings of arterial blood partial pressure of carbon dioxide (pCO2) and mean arterial pressure (MAP), with control or measurement of all deformation, anatomical, and other physiological variables. It is hypothesized that there are significant differences in relative viscoelastic properties of the living rabbit brain under different combinations of pCO2 and blood pressure. Stress-relaxation brain indentations were performed on seven consecutive anesthetized living rabbits, with control or measurement of all possible variables.. Five indentations were performed on each animal, with 15 minute periods of rest between each indentation, with the following relative physiological parameters: Indentation 1. Low MAP and low pCO2. Indentation 2. High MAP and low pCO2. Indentation 3. Low MAP and high pCO2. Indentation 4. High MAP and high pCO2. Indentation 5. Low MAP and low pCO2. The data were fitted to a generalized Maxwell model that incorporated two viscoelastic terms and one equilibrium elastic term. The relative stress-relaxation coefficients and material properties were determined, and compared using statistical analysis. Peak stresses encountered with relative step-loading ranged from approximately 2-4 x 103 Pa, with corresponding “instantaneous” elastic moduli approximating 4-8 x 103 Pa. A short and long Time of Relaxation was determined for each viscoelastic term of the model, and ranged from 0.03 – 1.72 s and 9.92 – 32.55 s respectively. Comparison of stress-relaxation coefficients and material properties reveals statistically significant differences in the stress coefficients and their respective elastic moduli across different combinations of pCO2 and MAP, and between the last indentation group and previous indentations. There were no significant differences found in Time of Relaxation coefficients. In conclusion, mechanical properties of step-loaded living rabbit brain are relatively dependent on pCO2 and MAP, and repetitive deformations. This may be important for further understanding of the brain in different physiological states and accurate mechanical characterization of the brain. It also highlights the need to control for these parameters during the mechanical testing of brain.
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How this classification was reachedexpand
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 | 0.000 | 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 | 0.000 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".