We use 129Xe NMR to probe the diffusion of xenon gas in the porous network of Vycor glass, by monitoring its relaxation properties. When the mean free path of the diffusing gas is larger than the pore size (Knudsen conditions), both 129Xe chemical shifts and relaxation rates are sensitive to the confinement of xenon gas within a porous solid. The influence of both temperature and xenon pressure are recorded on the 129Xe chemical shifts and relaxation rates, in order to characterise the xenon/Vycor interactions. Monte Carlo (MC) and Molecular Dynamics (MD) simulations, using a numerical model of Vycor, are required to interpret the relaxation properties of xenon. MD simulations clearly establish the occurrence of confined diffusion of xenon within Vycor, related to the geometry of this porous media. This work shows the potentiality of NMR relaxation to obtain dynamical information on the diffusion within porous media.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1016/s0730-725x(96)00198-1 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Loss of pulmonary capillaries in idiopathic pulmonary arterial hypertension with low diffusion capacity is accompanied by early diffuse emphysema detected by Xe MRI.
Eur Radiol
December 2024
Institute for Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.
Article Synopsis
- Recent studies propose a specific phenotype of idiopathic pulmonary arterial hypertension (IPAH) in smokers characterized by low carbon monoxide diffusion capacity without major emphysema.
- The study recruited patients across four groups to investigate pulmonary capillary loss as a possible cause, utilizing advanced imaging techniques like CT and Xe MRI.
- Results revealed significant reductions in specific imaging metrics in patients with IPAH and low diffusion capacity, supporting the hypothesis of pulmonary capillary loss and potential early emphysema changes.
Reevaluation of the Suitability of Xe Nuclear Magnetic Resonance Spectroscopy for Pore Size Determination in Porous Carbon Materials.
J Am Chem Soc
December 2024
Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan.
Xenon isotope nuclear magnetic resonance (Xe-NMR) spectroscopy has been widely used to evaluate the pore structure of materials. However, determining how to apply this technique to investigate porous carbon materials is sometimes challenging, partly due to the structural disorder and heterogeneity of the surface properties of these materials, and partly due to the lack of reliable methods for controlling and assessing the density of adsorbed Xe. In this study, we designed and constructed a temperature- and pressure-controllable Xe-NMR system to evaluate the interaction between activated carbon (AC) and adsorbed Xe molecules.
View Article and Find Full Text PDFMagnetic resonance image denoising for Rician noise using a novel hybrid transformer-CNN network (HTC-net) and self-supervised pretraining.
Med Phys
December 2024
Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences-Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, China.
Background: Magnetic resonance imaging (MRI) is a crucial technique for both scientific research and clinical diagnosis. However, noise generated during MR data acquisition degrades image quality, particularly in hyperpolarized (HP) gas MRI. While deep learning (DL) methods have shown promise for MR image denoising, most of them fail to adequately utilize the long-range information which is important to improve denoising performance.
View Article and Find Full Text PDFEvaluation of an integrated variable flip angle protocol to estimate coil B for hyperpolarized MRI.
Magn Reson Med
November 2024
Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, UK.
Purpose: The purpose of this work is to validate a simple and versatile integrated variable flip angle (VFA) method for mapping B in hyperpolarized MRI, which can be used to correct signal variations due to coil inhomogeneity.
Theory And Methods: Simulations were run to assess performance of the VFA B mapping method compared to the currently used constant flip angle (CFA) approach. Simulation results were used to inform the design of VFA sequences, validated in four volunteers for hyperpolarized xenon-129 imaging of the lungs and another four volunteers for hyperpolarized carbon-13 imaging of the human brain.
Rapid lung ventilation MRI using parahydrogen-induced polarization of propane gas.
Analyst
December 2024
Department of Chemistry, Integrative Biosciences (Ibio), Wayne State University, Karmanos Cancer Institute (KCI), Detroit, Michigan 48202, USA.
Proton-hyperpolarized contrast agents are attractive because they can be imaged on virtually any clinical MRI scanner, which is typically equipped to scan only protons rather than heteronuclei (, anything besides protons, , C, N, Xe, Na, .). Even though the lifetime of the proton spin hyperpolarization is only a few seconds, it is sufficient for inhalation and scanning of proton-hyperpolarized gas media.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!