@article {302, title = {Multiphase imaging of gas flow in a nanoporous material using remote-detection NMR}, journal = {Nature Materials}, volume = {5}, year = {2006}, note = {Nat Mater029AOTimes Cited:25Cited References Count:40}, month = {Apr}, pages = {321-327}, abstract = {

Pore structure and connectivity determine how microstructured materials perform in applications such as catalysis, fluid storage and transport, filtering or as reactors. We report a model study on silica aerogel using a time-of-flight magnetic resonance imaging technique to characterize the flow field and explain the effects of heterogeneities in the pore structure on gas flow and dispersion with Xe-129 as the gas-phase sensor. The observed chemical shift allows the separate visualization of unrestricted xenon and xenon confined in the pores of the aerogel. The asymmetrical nature of the dispersion pattern alludes to the existence of a stationary and a flow regime in the aerogel. An exchange time constant is determined to characterize the gas transfer between them. As a general methodology, this technique provides insights into the dynamics of flow in porous media where several phases or chemical species may be present.

}, keywords = {visualization}, isbn = {1476-1122}, doi = {Doi 10.1038/Nmat1598}, url = {://WOS:000236530400024}, author = {Harel, E. and Granwehr, J. and Seeley, J. A. and Pines, A.} } @article {317, title = {NMR-based biosensing with optimized delivery of polarized Xe-129 to solutions}, journal = {Analytical Chemistry}, volume = {77}, year = {2005}, note = {Anal Chem942GLTimes Cited:30Cited References Count:37}, month = {Jul 1}, pages = {4008-4012}, abstract = {

Laser-enhanced (LE) Xe-129 nuclear magnetic resonance (NMR) is an exceptional tool for sensing extremely small physical and chemical changes; however, the difficult mechanics of bringing polarized xenon and samples of interest together have limited applications, particularly to biological molecules. Here we present a method for accomplishing solution Xe-129 biosensing based on flow (bubbling) of LE Xe-129 gas through a solution in situ in the NMR probe, with pauses for data acquisition. This overcomes fundamental limitations of conventional solution-state LE Xe-129 NMR, e.g., the difficulty in transferring hydrophobic xenon into aqueous environments, and the need to handle the sample to refresh LE Xe-129 after an observation pulse depletes polarization. With this new method, we gained a factor of \> 100 in sensitivity due to improved xenon transfer to the solution and the ability to signal average by renewing the polarized xenon. Polarized xenon in biosensors was detected at very low concentrations, \<= 250 nanomolar, while retaining all the usual information from NMR. This approach can be used to simultaneously detect multiple sensors with different chemical shifts and is also capable of detecting signals from opaque, heterogeneous samples, which is a unique advantage over optical methods. This general approach is adaptable for sensing minute quantities of xenon in heterogeneous in vitro samples, in miniaturized devices and should be applicable to certain in-vivo environments.

}, keywords = {blood}, isbn = {0003-2700}, doi = {Doi 10.1021/Ac0500479}, url = {://WOS:000230270800035}, author = {Han, S. I. and Garcia, S. and Lowery, T. J. and Ruiz, E. J. and Seeley, J. A. and Chavez, L. and King, D. S. and Wemmer, D. E. and Pines, A.} } @article {327, title = {Remotely detected high-field MRI of porous samples}, journal = {Journal of Magnetic Resonance}, volume = {167}, year = {2004}, note = {J Magn Reson809KKTimes Cited:26Cited References Count:28}, month = {Apr}, pages = {282-290}, abstract = {

Remote detection of NMR is a novel technique in which an NMR-active sensor surveys an environment of interest and retains memory of that environment to be recovered at a later time in a different location. The NMR or MRI information about the sensor nucleus is encoded and stored as spin polarization at the first location and subsequently moved to a different physical location for optimized detection. A dedicated probe incorporating two separate radio frequency (RF)-circuits was built for this purpose. The encoding solenoid coil was large enough to fit around the bulky sample matrix, while the smaller detection solenoid coil had not only a higher quality factor, but also an enhanced filling factor since the coil volume comprised purely the sensor nuclei. We obtained two-dimensional (2D) void space images of two model porous samples with resolution less than 1.4 mm(2). The remotely reconstructed images demonstrate the ability to determine fine structure with image quality superior to their directly detected counterparts and show the great potential of NMR remote detection for imaging applications that suffer from low sensitivity due to low concentrations and filling factor. Published by Elsevier Inc.

}, keywords = {gas}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2003.12.018}, url = {://WOS:000220635400012}, author = {Seeley, J. A. and Han, S. I. 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 {346, title = {Laser-polarized Xe-129 NMR and MRI at ultralow magnetic fields}, journal = {Journal of Magnetic Resonance}, volume = {157}, year = {2002}, note = {J Magn Reson600EJTimes Cited:23Cited References Count:25}, month = {Aug}, pages = {235-241}, abstract = {

Laser-polarized Xe-129 and a high-T-c superconducting quantum interference device (SQUID) are used to obtain magnetic resonance images in porous materials at a magnetic field of 2.3 mT, corresponding to a Larmor frequency of 27 kHz. Image resolution of 1 mm is obtained with gradients of only 1 mT/m. The resolution of xenon chemical shifts in different physicochemical environments at ultralow fields is also demonstrated. Details of the circulating flow optical pumping apparatus and the SQUID spectrometer are presented. (C) 2002 Elsevier Science (USA).

}, keywords = {atoms}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.2002.2592}, url = {://WOS:000178377400009}, author = {Wong-Foy, A. and Saxena, S. and Moule, A. J. and Bitter, H. M. L. and Seeley, J. A. and McDermott, R. and Clarke, J. and Pines, A.} } @article {365, title = {Resolution of Xe-129 chemical shifts at ultralow magnetic field}, journal = {Journal of the American Chemical Society}, volume = {123}, year = {2001}, note = {J Am Chem Soc463TWTimes Cited:9Cited References Count:39}, month = {Aug 22}, pages = {8133-8134}, keywords = {adsorption}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja011064s}, url = {://WOS:000170494200027}, author = {Saxena, S. and Wong-Foy, A. and Moule, A. J. and Seeley, J. A. and McDermott, R. and Clarke, J. and Pines, A.} }