B<sub>1</sub> mapping of liquid NMR transversal RF coils: Analysis of heterogeneity and nonlinearity
Bibliographic record
Abstract
Abstract B 1 fields generated by transversal RF coils in a high‐resolution NMR probe were studied using a nutation experiment combined with gradient echo 1D‐profiling. Signal amplitude, B 1 strength, and relaxation time were mapped as a function of longitudinal axial position. Numerical Bloch simulations in a rotating frame could reproduce the overall features of the experimentally observed nutation profiles. The 3D rotating frame trajectories of magnetization during pulsing are presented in spherical coordinates. Nutating magnetization (i.e., sinusoidal oscillation) was detectable even outside the RF coil, although the signal amplitude was low and the spin relaxation during pulsing was fast. As the axial position got closer to the edges of the RF coil, low frequency components began overlapping on the nutating component. At the edge regions, the low frequency magnetizations dominated and the oscillating component almost disappeared, resulting in a cycloidal 3D trajectory of magnetization. Inside the RF coil, the low frequency component increased the frequency of oscillation as the axial position got closer to the center. Only a narrow central region of the RF coil gave a near linear response against pulse width, wherein the highest B 1 field strength and very small relaxation were observed. A significant nonlinearity between pulse duration and flip angle was observed in the edge portion of the RF coil and at the outside. The heterogeneity and nonlinearity led to an inaccurate 90° pulse width when the pulse duration at null points (e.g., 180° or 360°) was simply divided by 2 or 4. © 2012 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 41B: 1–12, 2012
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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 | 0.001 |
| 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".