@article {393, title = {Effects of diffusion on magnetic resonance imaging of laser-polarized xenon gas}, journal = {Journal of Chemical Physics}, volume = {108}, year = {1998}, note = {J Chem PhysZh114Times Cited:30Cited References Count:24}, month = {Apr 15}, pages = {6233-6239}, abstract = {

Molecular diffusion during the application of magnetic field gradients can distort magnetic resonance images. A systematic characterization of these distortions in one dimension was performed using highly spin-polarized xenon gas. By varying the strength of the applied gradient and the geometric dimension of the sample, the evolution of these image distortions between the regimes of strong and weak diffusion was observed. These results are compared with numerical simulations. By directly measuring the displacement distribution of the polarized xenon atoms, it is shown that in the weak-diffusion regime the image distortions originate from the restricted diffusive motion near the sample boundaries, in agreement with previous theoretical work. Additionally, it is shown that the effects of diffusion can be utilized to enhance the contrast between the boundaries and bulk in the images of polarized gas samples, and thus may be exploited as a means of boundary detection in such systems. (C) 1998 American Institute of Physics. [S0021-9606(98)02915-8].

}, keywords = {xe-129}, isbn = {0021-9606}, doi = {Doi 10.1063/1.476030}, url = {://WOS:000073073700018}, author = {Song, Y. Q. and Goodson, B. M. and Sheridan, B. and de Swiet, T. M. and Pines, A.} } @article {400, title = {In situ NMR analysis of fluids contained in sedimentary rock}, journal = {Journal of Magnetic Resonance}, volume = {133}, year = {1998}, note = {J Magn Reson116WNTimes Cited:23Cited References Count:23}, month = {Aug}, pages = {385-387}, abstract = {

Limitations of resolution and absorption in standard chemical spectroscopic techniques have made it difficult to study fluids in sedimentary rocks. In this paper, we show that a chemical characterization of pore fluids may be obtained in situ by magic angle spinning (MAS) nuclear magnetic resonance (NMR), which is normally used for solid samples. H-1 MAS-NMR spectra of water and crude oil in Berea sandstone show sufficient chemical shift resolution for a straightforward determination of the oil/water ratio, (C) 1998 Academic Press.

}, keywords = {oil}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.1998.1459}, url = {://WOS:000075748200020}, author = {de Swiet, T. M. and Tomaselli, M. and Hurlimann, M. D. and Pines, A.} } @article {399, title = {NMR spectra with peaks at the principal values of the chemical shielding tensor}, journal = {Chemical Physics Letters}, volume = {285}, year = {1998}, note = {Chem Phys LettZf354Times Cited:10Cited References Count:25}, month = {Mar 13}, pages = {59-63}, abstract = {

The NMR chemical shielding in a solid powder sample produces featured, but broad, lineshapes, or powder patterns, because the shielding experienced by a nuclear spin depends on the spatial orientation of its local molecular frame with respect to the external magnetic field. The Lineshape, however, is fully determined by the three principal values of the shielding tenser. We present a simple approach that uses sample spinning NMR to extract peaks at the principal-value frequencies from chemical shielding powder patterns. Such techniques may simplify spectra with overlapping powder patterns without the information loss inherent in fast magic angle spinning. Experimental data and numerical simulations are presented for two P-31 model compounds. (C) 1998 Elsevier Science B.V.

}, keywords = {SPECTROSCOPY}, isbn = {0009-2614}, doi = {Doi 10.1016/S0009-2614(97)01478-4}, url = {://WOS:000072889100010}, author = {de Swiet, T. M. and Tomaselli, M. and Pines, A.} }