@article {433, title = {NMR of laser-polarized xenon in human blood}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {93}, year = {1996}, note = {P Natl Acad Sci USAVt054Times Cited:92Cited References Count:27}, month = {Nov 12}, pages = {12932-12936}, abstract = {

By means of optical pumping with laser light it is possible to enhance the nuclear spin polarization of gaseous xenon by four to five orders of magnitude, The enhanced polarization has allowed advances in nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI), including polarization transfer to molecules and imaging of lungs and other void spaces, A critical issue for such applications is the delivery of xenon to the sample while maintaining the polarization, Described herein is an efficient method for the introduction of laser-polarized xenon into systems of biological and medical interest for the purpose of obtaining highly enhanced NMR/MRI signals. Using this method, we have made the first observation of the time-resolved process of xenon penetrating the red blood cells in fresh human blood-the xenon residence time constant in the red blood cells was measured to be 20.4+/-2 ms. The potential of certain biologically compatible solvents for delivery of laser-polarized xenon to tissues for NMR/MRI is discussed in light of their respective relaxation and partitioning properties.

}, keywords = {gas}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.93.23.12932}, url = {://WOS:A1996VT05400048}, author = {Bifone, A. and Song, Y. Q. and Seydoux, R. and Taylor, R. E. and Goodson, B. M. and Pietrass, T. and Budinger, T. F. and Navon, G. and Pines, A.} } @article {425, title = {Si-29 high resolution solid state nuclear magnetic resonance spectroscopy of porous silicon}, journal = {Journal of Non-Crystalline Solids}, volume = {202}, year = {1996}, note = {J Non-Cryst SolidsVe406Times Cited:13Cited References Count:33}, month = {Jul}, pages = {68-76}, abstract = {

Porous silicon has been characterized by Si-29 nuclear magnetic resonance spectroscopy under conditions of static samples, magic angle spinning, decoupling and cross polarization. In a free induction decay experiment, two Si-29 resonances at -80 and -111 ppm were obtained. Cross polarization resulted in a single resonance at -97 ppm. Magic angle spinning and decoupling slightly reduce the linewidth of the Si-29 cross polarized signal, The minor narrowing effect and thr relaxation behavior in the laboratory and rotating frame indicate a homogeneous contribution to the linewidth. The relaxation data suggest that the resonance observed under cross polarization conditions arises from SiH or SiH2 structural elements.

}, keywords = {dipolar}, isbn = {0022-3093}, doi = {Doi 10.1016/0022-3093(96)00144-5}, url = {://WOS:A1996VE40600008}, author = {Pietrass, T. and Bifone, A. and Roth, R. D. and Koch, V. P. and Alivisatos, A. P. and Pines, A.} } @article {443, title = {Adsorption Properties of Porous Silicon Characterized by Optically Enhanced Xe-129 Nmr-Spectroscopy}, journal = {Surface Science}, volume = {334}, year = {1995}, note = {Surf SciRk973Times Cited:31Cited References Count:33}, month = {Jul 10}, pages = {L730-L734}, abstract = {

Highly spin polarized xenon is used to study the adsorption properties of porous silicon surfaces by Xe-129 NMR spectroscopy. The sensitivity enhancement through optical pumping allows the NMR characterization of small amounts of physisorbed xenon in a pressure regime typical for adsorption isotherms. Fully hydrogen terminated porous silicon, porous silicon with an increased number of dangling bonds and porous silicon after methanol adsorption are characterized by the adsorbed Xe-129 NMR lineshape, chemical shift and relaxation behavior.

}, keywords = {field}, isbn = {0039-6028}, doi = {Doi 10.1016/0039-6028(95)80024-7}, url = {://WOS:A1995RK97300007}, author = {Pietrass, T. and Bifone, A. and Pines, A.} } @article {442, title = {Monitoring Xenon Clathrate Hydrate Formation on Ice Surfaces with Optically Enhanced Xe-129 Nmr}, journal = {Journal of the American Chemical Society}, volume = {117}, year = {1995}, note = {J Am Chem SocRk426Times Cited:60Cited References Count:41}, month = {Jul 19}, pages = {7520-7525}, abstract = {

A new technique for monitoring the formation of xenon clathrate hydrates is presented. Under controlled-temperature conditions, clathrate formation is studied with optically enhanced Xe-129 NMR spectroscopy, which allows the observation of the xenon occupation of both small and large clathrate cages. The experiments were performed in a temperature range of 170 to 258 K. Only in the range of 195 to 233 K did clathrate formation occur, with applied pressures of typically 0.3 MPa. The NMR data are analyzed with a simple kinetic model, which provides a rate coefficient for clathrate formation and a time constant which describes the decay of the NMR signal intensity. The analysis of the rate coefficients and occupancy ratios of the large to the small cages under the different experimental conditions enabled us to obtain some novel information on the hydrate phase formed on ice surfaces. The results suggest that the surface phase formed initially has many more occupied small cages than the bulk phase at equilibrium and that the composition evolves toward that of the bulk phase in a few minutes. At higher temperatures (258 K) the surface phase seems to be less stable than the bulk phase.

}, keywords = {field}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00133a025}, url = {://WOS:A1995RK42600025}, author = {Pietrass, T. and Gaede, H. C. and Bifone, A. and Pines, A. and Ripmeester, J. A.} } @article {454, title = {Surface Study of Supported Metal Particles by Xe-129 Nmr}, journal = {Physical Review Letters}, volume = {74}, year = {1995}, note = {Phys Rev LettQt449Times Cited:21Cited References Count:26}, month = {Apr 17}, pages = {3277-3280}, keywords = {states}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.74.3277}, url = {://WOS:A1995QT44900047}, author = {Bifone, A. and Pietrass, T. and Kritzenberger, J. and Pines, A. and Chmelka, B. F.} }