Philip K. Lee

Purpose To investigate a computationally efficient method for optimizing the Cramér‐Rao Lower Bound (CRLB) of quantitative sequences without using approximations or an analytical expression of the signal. Methods Automatic differentiation was applied to Bloch simulations and used to optimize several quantitative sequences without the need for approximations or an analytical expression. The results were validated with in vivo measurements and comparisons to prior art. Multi‐echo spin echo and DESPO were used as benchmarks to verify the CRLB implementation. The CRLB of the Magnetic Resonance Fingerprinting (MRF) sequence, which has a complicated analytical formulation, was also optimized using automatic differentiation. Results The sequence parameters obtained for multi‐echo spin echo and DESPO matched results obtained using conventional methods. In vivo, MRF scans demonstrate that the CRLB optimization obtained with automatic differentiation can improve performance in presence of white noise. For MRF, the CRLB optimization converges in 1.1 CPU hours for = 400 and has asymptotic runtime scaling for the calculation of the CRLB objective and gradient. Conclusions Automatic differentiation can be used to optimize the CRLB of quantitative sequences without using approximations or analytical expressions. For MRF, the runtime is computationally efficient and can be used to investigate confounding factors as well as MRF sequences with a greater number of repetitions.

Little experimental evidence exists regarding corrective television advertising as a remedy for misleading direct-to-consumer prescription drug ads. We examined how exposure to an ad for a fictitious prescription drug that appeared to offer benefits and risks superior to normative standards for asthma medication (i.e., a simulated violative ad) and a corresponding corrective ad shaped viewer perceptions, understanding, and intended behavior. Through an experiment with 1,057 participants, we found that a corrective ad counteracted viewer belief of an overstatement of efficacy claim, but was less successful in counteracting omission of risk. Corrective ad exposure also affected general viewer perceptions of, and intended behaviors toward, the drug.

Solid-state potassium-39 NMR spectra of two potassium complexes of crown-ether-based organic ligands (1·KI and 2) have been acquired at 11.75 and 21.1 T and interpreted to provide information on the 39K quadrupolar and chemical shift tensors. The analyses reveal a large potassium chemical shift tensor span of 75 ± 20 ppm for 1·KI. This appears to be the first such measurement for potassium in an organic complex, thereby suggesting the utility of potassium chemical shift tensors for characterizing organic and biomolecular K+ binding environments. Compound 2 exhibits a cation−π interaction between K+ and a phenyl group, and therefore, the 39K NMR tensors obtained for this compound must be partly representative of this interaction. Analyses of potassium-39 spin-rotation data for gaseous 39K19F and 39K35Cl available from molecular beam experiments performed by Cederberg and co-workers reveal the largest potassium CS tensor spans known to date, 84.39 and 141 ppm, respectively. Collectively, the results obtained highlight the potential of ultrahigh-field potassium-39 solid-state NMR spectroscopy and, in particular, the wide range of the anisotropy of the potassium CS tensor when organic and diatomic systems are considered.