第8楼2004/12/29
请教,气体分子运动快和捕捉核磁信号有什么关系?听说武汉物理所研究过激光抽运气体核磁。
请问荔枝肉的结果发表了吗?很感兴趣。可否把几个谱拿出来大家分享。
固体实验结果多看到武汉物理所、复旦大学、大连化物所、厦门大学、华东师大、石化院的文章。不知南京王教授的文章在那里能查到?真想拜读一下。
第9楼2004/12/29
Probing porous media with noble gas NMR
We are developing noble gas nuclear magnetic resonance (NMR) as a non-destructive probe of the structure of porous media. We use pulsed-field-gradient (PFG) NMR and magnetic resonance imaging (MRI) to measure the flow and diffusion of noble gas (3He and 129Xe) imbided into the pore space of granular materials, animal lungs, and oil- or water-reservoir rocks. Diagnosing the structure of these materials is relevant to a wide range of scientific and technological problems. For example, knowledge of the fluid transport properties of reservoir rocks is important for the monitoring of contaminant percolation and for oil extraction. Similarly, knowledge of the evolution of the porous structure of materials subjected to large thermal or mechanical stress may help characterize the dynamics of cracking and material failure. Also, non-invasive mapping of lung structure could advance our understanding of normal physiology as well as disease diagnosis.
The advantages of noble gas NMR as a porous media diagnostic arise from three physical effects: (i) gas diffusion coefficients are orders of magnitude larger than those of liquids, which allows long distances to be probed; (ii) noble gas atoms interact weakly with pore surfaces, which enables long NMR lifetimes; and (iii) noble gases are chemically inert and biologically compatible. We employ both laser-polarized and thermally-polarized noble gas in our measurements.
We have shown that noble gas NMR can characterize important porous media parameters such as permeability, effective porosity, tortuosity, and the distribution of pore sizes. Permeability is a measure of the ability of a porous material to transmit fluid. Effective porosity is the volume fraction of a pore space that is fully interconnected and contributes to fluid flow through the material, excluding dead-end or isolated pores that cannot be part of a flow path. Tortuosity is a measure of the long-distance pore connectivity of the medium.