Reactive Scattering of 1−5 eV O<sup>-</sup> in Films of Tetrahydrofuran
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Bibliographic record
Abstract
An understanding of all nascent events leading to radiolytic DNA damage is required to achieve a complete description of ionizing radiation effects on living cells. These early, subpicosecond events involve mainly low-energy ( E < 20 eV) secondary electrons (SE) and low-energy ( E < 5 eV) secondary ion (and neutral) fragments; the latter are created either by the primary radiation or by SE via resonant mechanisms, i.e., dissociative electron attachment (DEA). While recent work has shown that 3−15 eV SE initiate DNA strand break formation exclusively via resonances, the subsequent damage induced by the energetic DEA ion fragments in DNA or its basic components is unknown. Here, we report 0−20 eV electron impact measurements of negative ion desorption from condensed films containing O 2 and tetrahydrofuran, C 4 H 8 O (THF), a deoxyribose analogue. Our experiments show that all of the OH - and some of the H - desorption yields are the result of reactive scattering of the 1−5 eV O - fragments produced initially by DEA to O 2 . These O - reactions involve hydrogen abstraction and atom exchange from THF, and result in the formation of THF-yl radicals, as well as THF oxidation products, most likely lactones and alkoxyl radicals. O - scatters over nanometer distances comparable to DNA dimensions, and reactions involve formation of a transient (OC 4 H 8 O)* - collision complex. Our measurements support the notion that in DNA, exposed to ionizing radiation, similar localized secondary ion reactions can be initiated by the abundant secondary electrons, and may result in further clustered damage, lethal chemical transformations, and enhance DNA lesions.
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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 it