Fragmentation of Bacteriogenic Iron Oxides in Response to Hydrodynamic Shear Stress
Bibliographic record
Abstract
A viscous shear stress of 1.97 Nm2 was applied to suspensions of freshwater, brackish and marine bacteriogenic iron oxides (BIOS) in shake flasks. Samples were taken at intervals over 480 minutes for scanning electron microscopy. The remains of three Fe2+-oxidizing bacteria (FeOB) genera were conspicuous biomass constituents in the BIOS samples; these included the filamentous extracellular sheaths of Leptothrix, as well as helical fibrous stalks of Gallionella and Mariprofundus. The applied hydrodynamic shear stress resulted in an exponential decrease in Leptothrix sheath and Gallionella-Mariprofundus stalk lengths; first-order breakage rate constants derived from the experimental measurements ranged from 0.009 to 0.023 min−1 and 0.014 to 0.021 min−1, respectively. Breakage half-times extended from 30 to 70 min. Shear strength values calculated from the time course data ranged from 27.8 to 29.6 Nm−2 for Leptothrix sheaths, and from 28.0 to 28.8 Nm−2 for Gallionella-Mariprofundus stalks. Computational analyses showed that breakage half-times decreased rapidly with increasing shear stress, implying that the accumulation of BIOS is constrained hydrodynamically to quiescent aqueous environments. These results imply that there is considerable potential for natural hydrodynamic fluctuations in basal shear stress levels to bring about resuspension and advective dispersal of BIOS. Immediate consequences anticipated from such events include enhanced particulate transport of BIOS-associated chemical species through aquatic systems, as well as reduced preservation potential and underrepresentation of BIOS bacteria structures as microfossils in the geological record.
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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 | 0.001 | 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) | 0.001 | 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 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".