Direct observation of hyperpolarization breaking through the spin diffusion barrier

Quentin Stern, Samuel F. Cousin, Frederic Mentink-Vigier, Arthur C. Pinon, Stuart J. Elliott, Olivier Cala & Sami Jannin
Dynamic nuclear polarization (DNP) is a widely used tool for overcoming the low intrinsic sensitivity of nuclear magnetic resonance spectroscopy and imaging. Its practical applicability is typically bounded, however, by the so-called ‘spin diffusion barrier’, which relates to the poor efficiency of polarization transfer from highly polarized nuclei close to paramagnetic centers to bulk nuclei. A quantitative assessment of this barrier has been hindered so far by the lack of general methods for studying nuclear-polarization...
8 views reported since publication in 2021.

These counts follow the COUNTER Code of Practice, meaning that Internet robots and repeats within a certain time frame are excluded.
What does this mean?