Bibliographic record
Abstract
For many years cavity ionization chambers have been the preferred detectors for measuring absorbed dose from ionizing radiation.Cavity theory formalisms relate the detector signal to a dose in the surrounding medium.Common cavity theories are straightforward to calculate but make limiting assumptions about charged particle fluences in the chamber and the medium.The choices that make them accurate are conceptually ambiguous and unrelated to physics first principles.This prohibits their general application across a wide range of physical conditions.A novel general cavity theory is introduced which addresses some of the previous limiting assumptions of existing formalisms by explicitly determining the perturbation of charged particles in the medium due to the chamber cavity.This cavity theory removes the ambiguity and derives from first principles at the expense of increased complexity.The formalism converges to the Spencer-Attix cavity theory in the limit of Bragg-Gray conditions and to the ratio of mass-energy absorption coefficients in the large cavity limit.The EGSnrc Monte Carlo simulation software is used to determine the expected dose ratios from full chamber dose calculations and to generate the input quantities to the novel formalism with regard to the air kerma formalism under Fano conditions.For 1.25 MeV incident photons the formalism is within 0.1% of full chamber calculated dose ratios for materials with atomic numbers 4 ≤ Z ≤ 29, between 0.2-0.7% at 300 keV, and between 0.8-5.3% at 50 keV.Formalism dose ratios calculated from cobalt-60, and 120 kVp x-ray, spectra showed similar agreement with full chamber calculated dose ratios as the mono-energetic cases.This new cavity theory is shown to be five times more accurate, on average, than Spencer-Attix for cavity heights of 1.39 mm, and 2.3 times more accurate, on Dr. Daniel La Russa, for their support and guidance during my time at the Ottawa Hospital.Together they offered wisdom and expertise throughout this journey.Daniel never hesitated to lend a hand with the hard work, dive into the details of the project, and help solve the confusing parts.I am thankful and indebted to them for their efforts.Many thanks to my wife, Janet, for her love
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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 | 0.004 | 0.009 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.005 |
| Scholarly communication | 0.003 | 0.005 |
| Open science | 0.004 | 0.005 |
| Research integrity | 0.003 | 0.003 |
| Insufficient payload (model declined to judge) | 0.010 | 0.002 |
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".