@article {267, title = {Hyperpolarized xenon NMR and MRI signal amplification by gas extraction}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {106}, year = {2009}, note = {P Natl Acad Sci USA503MDTimes Cited:12Cited References Count:33}, month = {Oct 6}, pages = {16903-16906}, abstract = {

A method is reported for enhancing the sensitivity of NMR of dissolved xenon by detecting the signal after extraction to the gas phase. We demonstrate hyperpolarized xenon signal amplification by gas extraction (Hyper-SAGE) in both NMR spectra and magnetic resonance images with time-of-flight information. Hyper-SAGE takes advantage of a change in physical phase to increase the density of polarized gas in the detection coil. At equilibrium, the concentration of gas-phase xenon is approximate to 10 times higher than that of the dissolved-phase gas. After extraction the xenon density can be further increased by several orders of magnitude by compression and/or liquefaction. Additionally, being a remote detection technique, the Hyper-SAGE effect is further enhanced in situations where the sample of interest would occupy only a small proportion of the traditional NMR receiver. Coupled with targeted xenon biosensors, Hyper-SAGE offers another path to highly sensitive molecular imaging of specific cell markers by detection of exhaled xenon gas.

}, keywords = {field}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0909147106}, url = {://WOS:000270537500005}, author = {Zhou, X. and Graziani, D. and Pines, A.} } @article {286, title = {Multipole shimming of permanent magnets using harmonic corrector rings}, journal = {Review of Scientific Instruments}, volume = {78}, year = {2007}, note = {Rev Sci Instrum151WETimes Cited:8Cited References Count:8}, month = {Mar}, abstract = {

Shimming systems are required to provide sufficient field homogeneity for high resolution nuclear magnetic resonance (NMR). In certain specialized applications, such as rotating-field NMR and mobile ex situ NMR, permanent magnet-based shimming systems can provide considerable advantages. We present a simple two-dimensional shimming method based on harmonic corrector rings which can provide arbitrary multipole order shimming corrections. Results demonstrate, for example, that quadrupolar order shimming improves the linewidth by up to an order of magnitude. An additional order of magnitude reduction is in principle achievable by utilizing this shimming method for z-gradient correction and higher order xy gradients. (c) 2007 American Institute of Physics.

}, keywords = {field}, isbn = {0034-6748}, doi = {Doi 10.1063/1.2713438}, url = {://WOS:000245320800056}, author = {Jachmann, R. C. and Trease, D. R. and Bouchard, L. S. and Sakellariou, D. and Martin, R. W. and Schlueter, R. D. and Budinger, T. F. and Pines, A.} } @article {312, title = {High-resolution nuclear magnetic resonance spectroscopy of biological tissues using projected magic angle spinning}, journal = {Magnetic Resonance in Medicine}, volume = {54}, year = {2005}, note = {Magnet Reson Med949DSTimes Cited:2Cited References Count:28}, month = {Aug}, pages = {253-257}, abstract = {

High-resolution NMR spectra of materials subject to anisotropic broadening are usually obtained by rotating the sample about the magic angle, which is 54.7 degrees to the static magnetic field. In projected magic angle spinning (p-MAS), the sample is spun about two angles, neither of which is the magic angle. This provides a method of obtaining isotropic spectra while spinning at shallow angles. The p-MAS experiment may be used in situations where spinning the sample at the magic angle is not possible due to geometric or other constraints, allowing the choice of spinning angle to be determined by factors such as the shape of the sample, rather than by the spin physics. The application of this technique to bovine tissue samples is demonstrated as a proof of principle for future biological or medical applications.

}, keywords = {field}, isbn = {0740-3194}, doi = {Doi 10.1002/Mrm.20585}, url = {://WOS:000230765700001}, author = {Martin, R. W. and Jachmann, R. C. and Sakellariou, D. and Nielsen, U. G. and Pines, A.} } @article {340, title = {Amplification of xenon NMR and MRI by remote detection}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {100}, year = {2003}, note = {P Natl Acad Sci USA709HPTimes Cited:65Cited References Count:28}, month = {Aug 5}, pages = {9122-9127}, abstract = {

A technique is proposed in which an NMR spectrum or MRI is encoded and stored as spin polarization and is then moved to a different physical location to be detected. Remote detection allows the separate optimization of the encoding and detection steps, permitting the independent choice of experimental conditions and excitation and detection methodologies. In the initial experimental demonstration of this technique, we show that taking dilute Xe-129 from a porous sample placed inside a large encoding coil and concentrating it into a smaller detection coil can amplify NMR signal. In general, the study of NMR active molecules at low concentration that have low physical filling factor is facilitated by remote detection. In the second experimental demonstration, MRI information encoded in a very low-field magnet (4-7 mT) is transferred to a high-field magnet (4.2 T) to be detected under optimized conditions. Furthermore, remote detection allows the utilization of ultrasensitive optical or superconducting quantum interference device detection techniques, which broadens the horizon of NMR experimentation.

}, keywords = {field}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.1133497100}, url = {://WOS:000184620000007}, author = {Moule, A. J. and Spence, M. M. and Han, S. I. and Seeley, J. A. and Pierce, K. L. and Saxena, S. 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.} }