The role of water in methane adsorption and diffusion within nanoporous silica investigated by hyperpolarized 129Xe and 1H PFG NMR spectroscopy

Understanding the properties and behavior of water molecules in restricted geometries, such as the nanopores of rocks, is of interest for shale gas exploitation. We present herein ex situ and in situ nuclear magnetic resonance （NMR） studies on the effects of water on the adsorption and diffusion of methane in nanopores. Silica materials with one-dimensional pores of ZSM-22, MCM-41, and SBA-15, with pore sizes ranging from 0.5 to 6 nm, were chosen as models. Hyperpolarized （HP） 129Xe NMR results show that water adsorption does not affect the pore sizes of ZSM-22 and MCM-41 but reduces that of SBA-15. The presence of water suppresses methane adsorption; this suppression effect is stronger in smaller pores. The self-diffusion coefficients of methane within ZSM-22 and MCM-41 are not significantly influenced by the presence of water, as measured by ~H pulsed field gradient （PFG） NMR. However, within SBA-15, which has a pore size of 6 nm, the diffusion coefficient of methane increases as the amount of water adsorption increases, peaks, and then decreases to a constant value with further water adsorption. These experiments reveal the effects of the pore size and the presence of water on methane adsorption and diffusion in constrained spaces, which could have important implications for flow simulations of methane in shales.

Evaluation of injuries caused by coronavirus disease 2019 using multi-nuclei magnetic resonance imaging

The ongoing pandemic of coronavirus disease 2019(COVID-19)has been a great burden for the healthcare system in many countries because of its high transmissibility,severity,and fatality.Chest radiography and computed tomography(CT)play a vital role in the diagnosis,detection of complications,and prognostication of COVID-19.Additionally,magnetic resonance imaging(MRI),especially multi-nuclei MRI,is another important imaging technique for disease diagnosis because of its good soft tissue contrast and the ability to conduct structural and functional imaging,which has also been used to evaluate COVID-19-related organ injuries in previous studies.Herein,we briefly reviewed the recent research on multi-nuclei MRI for evaluating injuries caused by COVID-19 and the clinical 1 H MRI techniques and their applications for assessing injuries in lungs,brain,and heart.Moreover,the emerging hyperpolarized 129Xe gas MRI and its applications in the evaluation of pulmonary structures and functional abnormalities caused by COVID-19 were also reviewed.