@article {3171, title = {Selective decoupling and Hamiltonian engineering in dipolar spin networks}, journal = {Physics Review Letters}, volume = {122}, year = {2019}, month = {01/2019}, abstract = {

We present a protocol to selectively decouple, recouple, and engineer effective interactions in mesoscopic dipolar spin networks. In particular, we develop a versatile protocol that relies upon magic angle spinning to perform Hamiltonian engineering. By using global control fields in conjunction with a local actuator, such as a diamond nitrogen vacancy center located in the vicinity of a nuclear spin network, both global and local control over the effective couplings can be achieved. We show that the resulting effective Hamiltonian can be well understood within a simple, intuitive geometric picture, and corroborate its validity by performing exact numerical simulations in few-body systems. Applications of our method are in the emerging fields of two-dimensional room temperature quantum simulators in diamond platforms, as well as in molecular magnet systems.

}, doi = {https://doi.org/10.1103/PhysRevLett.122.013205}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.013205}, author = {A. Ajoy and U. Bissbort and D. Poletti and P. Cappellaro} } @article {3193, title = {Zero-Field Nuclear Magnetic Resonance of Chemically Exchanging Systems}, journal = {Nature Communications}, volume = {10}, year = {2019}, month = {07/2019}, abstract = {

Zero- to ultralow-field (ZULF) nuclear magnetic resonance (NMR) is an emerging tool for precision chemical analysis. In this work, we study dynamic processes and investigate the influence of chemical exchange on ZULF NMR J-spectra. We develop a computational approach that allows quantitative calculation of J-spectra in the presence of chemical exchange and apply it to study aqueous solutions of [15N]ammonium (15N) as a model system. We show that pH-dependent chemical exchange substantially affects the J-spectra and, in some cases, can lead to degradation and complete disappearance of the spectral features. To demonstrate potential applications of ZULF NMR for chemistry and biomedicine, we show a ZULF NMR spectrum of [2-13C]pyruvic acid hyperpolarized via dissolution dynamic nuclear polarization (dDNP). We foresee applications of affordable and scalable ZULF NMR coupled with hyperpolarization to study chemical exchange phenomena in vivo and in situations where high-field NMR detection is not possible to implement.

}, doi = {https://doi.org/10.1038/s41467-019-10787-9}, url = {https://www.nature.com/articles/s41467-019-10787-9?fbclid=IwAR1MB5nAamCMGynKRk0sjD6V8rTlZ329IvrVKrCwIO8QjrEH4wD23BV5gak}, author = {Danila Barskiy and Michael Tayler and Irene Marco-Rius and John Kurhanewicz and Daniel Vigneron and Sevil Cikrikci and Ayca Aydogdu and Moritz Reh and Andrey Pravdivtsev and Jan-Bernd H{\"o}vener and John Blanchard and Teng Wu and Dmitry Budker and Alexander Pines} } @article {3196, title = {Hyperpolarized NMR Spectroscopy: d-DNP, PHIP, and SABRE Techniques}, journal = {Chemistry - An Aisan Journal}, volume = {13}, year = {2018}, month = {08/2018}, abstract = {

The intensity of NMR signals can be enhanced by several orders of magnitude by using various techniques for the hyperpolarization of different molecules. Such approaches can overcome the main sensitivity challenges facing modern NMR/magnetic resonance imaging (MRI) techniques, whilst hyperpolarized fluids can also be used in a variety of applications in material science and biomedicine. This Focus Review considers the fundamentals of the preparation of hyperpolarized liquids and gases by using dissolution dynamic nuclear polarization (d-DNP) and parahydrogen-based techniques, such as signal amplification by reversible exchange (SABRE) and parahydrogen-induced polarization (PHIP), in both heterogeneous and homogeneous processes. The various new aspects in the formation and utilization of hyperpolarized fluids, along with the possibility of observing NMR signal enhancement, are described.

}, doi = {10.1002/asia.201800551}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/asia.201800551}, author = {Kirill Kovtunov and Ekaterina Pokochueva and Oleg Salnikov and Samuel Cousin and Dennis Kurzbach and Basile Vuichoud and Sami Jannin and Eduard Chekmenev and Boyd Goodson and Danila Barskiy and Igor Koptyug} } @article {2812, title = {Distance-dependent magnetic resonance tuning as a versatile MRI sensing platform for biological targets}, journal = {Nature Materials}, volume = {16}, year = {2017}, pages = {537 - 542}, chapter = {537}, author = {Choi, J.-S. and Kim, S. and Yoo, D. and Shin, T.-H. and Kim, H. and Gomes, M.D. and Kim, S. H. and Pines, A. and Cheon, J.} } @article {245, title = {Fundamental Aspects of Parahydrogen Enhanced Low-Field Nuclear Magnetic Resonance}, journal = {Physical Review Letters}, volume = {110}, year = {2013}, note = {Phys Rev Lett113RITimes Cited:0Cited References Count:28}, month = {Mar 26}, pages = {137602}, abstract = {

We report new phenomena in low-field H-1 nuclear magnetic resonance (NMR) spectroscopy using parahydrogen induced polarization (PHIP), enabling determination of chemical shift differences, delta nu, and the scalar coupling constant J. NMR experiments performed with thermal polarization in millitesla magnetic fields do not allow the determination of scalar coupling constants for homonuclear coupled spins in the inverse weak coupling regime (delta nu \< J). We show here that low-field PHIP experiments in the inverse weak coupling regime enable the precise determination of delta nu and J. Furthermore we experimentally prove that observed splittings are related to delta nu in a nonlinear way. Naturally abundant C-13 and Si-29 isotopes lead to heteronuclear J-coupled H-1-multiplet lines with amplitudes significantly enhanced compared to the amplitudes for thermally prepolarized spins. PHIP-enhanced NMR in the millitesla regime allows us to measure characteristic NMR parameters in a single scan using samples containing rare spins in natural abundance. DOI: 10.1103/PhysRevLett.110.137602

}, keywords = {exchange}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.110.137602}, url = {://WOS:000316685100032}, author = {Colell, J. and Turschmann, P. and Gloggler, S. and Schleker, P. and Theis, T. and Ledbetter, M. and Budker, D. and Pines, A. and Blumich, B. and Appelt, S.} } @article {256, title = {Relaxivity of Gadolinium Complexes Detected by Atomic Magnetometry}, journal = {Magnetic Resonance in Medicine}, volume = {66}, year = {2011}, note = {Magn Reson Med799AVTimes Cited:1Cited References Count:23}, month = {Aug}, pages = {605-608}, abstract = {

Laser atomic magnetomeby is a portable and low-cost yet highly sensitive method for low magnetic field detection. In this work, the atomic magnetometer was used in a remote-detection geometry to measure the relaxivity of aqueous gadolinium-diethylenetriamine pentaacetic acid Gd(DTPA) at the Earth\&$\#$39;s magnetic field (40 mu T). The measured relaxivity of 9.7 +/- 2.0 s(-1) mM(-1) is consistent with field-cycling experiments measured at slightly higher magnetic fields, but no cryogens or strong and homogeneous magnetic field were required for this experiment. The field-independent sensitivity of 80 fT Hz(-1/2) allowed an in vitro detection limit of similar to 10 mu M Gd(DTPA) to be measured in aqueous buffer solution. The low detection limit and enhanced relaxivity of Gd-containing complexes at Earth\&$\#$39;s field motivate continued development of atomic magnetometry toward medical applications. Magn Reson Med 66:605-608, 2011. (C) 2011 Wiley-Liss, Inc.

}, keywords = {nmr}, isbn = {0740-3194}, doi = {Doi 10.1002/Mrm.22811}, url = {://WOS:000293256800033}, author = {Michalak, D. J. and Xu, S. J. and Lowery, T. J. and Crawford, C. W. and Ledbetter, M. and Bouchard, L. S. and Wemmer, D. E. and Budker, D. and Pines, A.} } @article {254, title = {Remotely Detected NMR for the Characterization of Flow and Fast Chromatographic Separations Using Organic Polymer Monoliths}, journal = {Analytical Chemistry}, volume = {83}, year = {2011}, note = {Anal Chem798ZVTimes Cited:4Cited References Count:35}, month = {Aug 1}, pages = {6004-6010}, abstract = {

An application of remotely detected magnetic resonance imaging is demonstrated for the characterization of flow and the detection of fast, small molecule separations within hypercrosslinked polymer monoliths. The hyper-cross-linked monoliths exhibited excellent ruggedness, with a transit time relative standard deviation of less than 2.1\%, even after more than 300 column volumes were pumped through at high pressure and flow. Magnetic resonance imaging enabled high. resolution intensity and velocity-encoded images of mobile phase flow through the monolith. The images confirm that the presence of a polymer monolith within the capillary disrupts the parabolic laminar flow profile that is characteristic of mobile phase flow within an open tube. As a result, the mobile phase and analytes are equally distributed in the radial direction throughout the monolith. Also, in-line monitoring of chromatographic separations of small molecules at high flow rates is shown. The coupling of monolithic chromatography columns and NMR provides both real-time peak detection and chemical shift information for small aromatic molecules. These experiments demonstrate the unique power of magnetic resonance, both direct and remote, in studying chromatographic processes.

}, keywords = {visualization}, isbn = {0003-2700}, doi = {Doi 10.1021/Ac2010108}, url = {://WOS:000293252500029}, author = {Teisseyre, T. Z. and Urban, J. and Halpern-Manners, N. W. and Chambers, S. D. and Bajaj, V. S. and Svec, F. and Pines, A.} } @article {269, title = {Distortion-free magnetic resonance imaging in the zero-field limit}, journal = {Journal of Magnetic Resonance}, volume = {200}, year = {2009}, note = {J Magn Reson526AWTimes Cited:6Cited References Count:29}, month = {Oct}, pages = {285-290}, abstract = {

MRI is a powerful technique for clinical diagnosis and materials characterization. Images are acquired in a homogeneous static magnetic field much higher than the fields generated across the field of view by the spatially encoding field gradients. Without such a high field, the concomitant components of the field gradient dictated by Maxwell\&$\#$39;s equations lead to severe distortions that make imaging impossible with conventional MRI encoding. In this paper, we present a distortion-free image of a phantom acquired with a fundamentally different methodology in which the applied static field approaches zero. Our technique involves encoding with pulses of uniform and gradient field, and acquiring the magnetic field signals with a SQUID. The method can be extended to weak ambient fields, potentially enabling imaging in the Earth\&$\#$39;s field without cancellation coils or shielding. Other potential applications include quantum information processing and fundamental studies of long-range ferromagnetic interactions. (C) 2009 Elsevier Inc. All rights reserved.

}, keywords = {gradients}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2009.07.016}, url = {://WOS:000272260900015}, author = {Kelso, N. and Lee, S. K. and Bouchard, L. S. and Demas, V. and M{\"u}ck, M. and Pines, A. and Clarke, J.} } @article {268, title = {Optical detection of NMR J-spectra at zero magnetic field}, journal = {Journal of Magnetic Resonance}, volume = {199}, year = {2009}, note = {J Magn Reson456YJTimes Cited:19Cited References Count:26}, month = {Jul}, pages = {25-29}, abstract = {

Scalar couplings of the form JI(1) . I(2) between nuclei impart valuable information about molecular structure to nuclear magnetic-resonance spectra. Here we demonstrate direct detection of J-spectra due to both heteronuclear and homonuclear J-coupling in a zero-field environment where the Zeeman interaction is completely absent. We show that characteristic functional groups exhibit distinct spectra with straightforward interpretation for chemical identification. Detection is performed with a microfabricated optical atomic magnetometer, providing high sensitivity to samples of microliter volumes. We obtain 0.1 Hz linewidths and measure scalar-coupling parameters with 4-mHz statistical uncertainty. We anticipate that the technique described here will provide a new modality for high-precision\" J spectroscopy\" using small samples oil microchip devices for multiplexed Screening, assaying, and sample identification in chemistry and biomedicine. (C) 2009 Elsevier Inc. All rights reserved.

}, keywords = {cells}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2009.03.008}, url = {://WOS:000266890300004}, author = {Ledbetter, M. P. and Crawford, C. W. and Pines, A. and Wemmer, D. E. and Knappe, S. and Kitching, J. and Budker, D.} } @article {272, title = {Picomolar sensitivity MRI and photoacoustic imaging of cobalt nanoparticles}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {106}, year = {2009}, note = {P Natl Acad Sci USA420HDTimes Cited:43Cited References Count:41}, month = {Mar 17}, pages = {4085-4089}, abstract = {

Multimodality imaging based on complementary detection principles has broad clinical applications and promises to improve the accuracy of medical diagnosis. This means that a tracer particle advantageously incorporates multiple functionalities into a single delivery vehicle. In the present work, we explore a unique combination of MRI and photoacoustic tomography (PAT) to detect picomolar concentrations of nanoparticles. The nanoconstruct consists of ferromagnetic (Co) particles coated with gold (Au) for biocompatibility and a unique shape that enables optical absorption over a broad range of frequencies. The end result is a dual-modality probe useful for the detection of trace amounts of nanoparticles in biological tissues, in which MRI provides volume detection, whereas PAT performs edge detection.

}, keywords = {cancer}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0813019106}, url = {://WOS:000264278800008}, author = {Bouchard, L. S. and Anwar, M. S. and Liu, G. L. and Hann, B. and Xie, Z. H. and Gray, J. W. and Wang, X. D. and Pines, A. and Chen, F. F.} } @article {273, title = {Flow in Porous Metallic Materials: A Magnetic Resonance Imaging Study}, journal = {Journal of Magnetic Resonance Imaging}, volume = {28}, year = {2008}, note = {J Magn Reson Imaging367QCTimes Cited:5Cited References Count:22}, month = {Nov}, pages = {1299-1302}, abstract = {

Purpose: To visualize flow dynamics of analytes inside porous metallic materials with laser-detected magnetic resonance imaging (MRI).Materials and Methods: We examine the flow of nuclear-polarized water in a porous stainless steel cylinder. Laser-detected MRI utilizes a sensitive optical atomic magnetometer as the detector. Imaging was performed in a remote-detection mode: the encoding was conducted in the Earth\&$\#$39;s magnetic field, and detection is conducted downstream of the encoding location. Conventional MRI (7T) was also performed for comparison.Results: Laser-detected MRI clearly showed MR images of water flowing through the sample, whereas conventional MRI provided no image.Conclusion: We demonstrated the viability of laser-detected MRI at low-field for studying porous metallic materials, extending MRI techniques to a new group of systems that is normally not accessible to conventional MRI.

}, keywords = {mri}, isbn = {1053-1807}, doi = {Doi 10.1002/Jmri.21532}, url = {://WOS:000260566100033}, author = {Xu, S. J. and Harel, E. and Michalak, D. J. and Crawford, C. W. and Budker, D. and Pines, A.} } @article {281, title = {Fluid-flow characterization with nuclear spins without magnetic resonance}, journal = {Applied Physics Letters}, volume = {93}, year = {2008}, note = {Appl Phys Lett345DHTimes Cited:2Cited References Count:20}, month = {Sep 1}, abstract = {

A technique for noninvasive monitoring of flow inside metallic enclosures using laser-based atomic magnetometry is introduced. The analyte is labeled via nuclear magnetization by magnets, thereby combining the polarization and encoding steps. No radiofrequency or audiofrequency pulses are involved. We demonstrate detection of flow inside an aluminum pipe with an inner diameter of 4.9 mm that has a constriction with a diameter of 1.6 mm and a length of 6.4 mm. The results agree with a model of spin density and relaxation indicating that our technique allows for fast, quantitative, and noninvasive diagnostics of flow with potential applications discussed below. (c) 2008 American Institute of Physics.

}, keywords = {mri}, isbn = {0003-6951}, doi = {Doi 10.1063/1.2977773}, url = {://WOS:000258975800042}, author = {Crawford, C. W. and Xu, S. J. and Siegel, E. J. and Budker, D. and Pines, A.} } @article {274, title = {Submillimeter-resolution magnetic resonance imaging at the Earth{\textquoteright}s magnetic field with an atomic magnetometer}, journal = {Physical Review A}, volume = {78}, year = {2008}, note = {Phys Rev A333VGTimes Cited:18Cited References Count:24}, month = {Jul}, abstract = {

Magnetic resonance imaging in the Earth\&$\#$39;s magnetic field is achieved using a sensitive atomic magnetometer for detection. We demonstrate images with a submillimeter resolution by recording the flow of two water paths meeting at a T-shaped mixer. The high homogeneity of the Earth\&$\#$39;s field allows the use of weak gradient fields which circumvent the concomitant-field effect. To distinguish the two input channels, we employed selective polarization, which is a unique and noninvasive labeling method for low-field magnetic resonance imaging. Our technique imposes minimal physical constraints on the object under study, in contrast to conventional high-field magnetic resonance imaging. This technique is applicable for microfluidic imaging in laboratory-on-a-chip devices.

}, keywords = {nmr}, isbn = {1050-2947}, doi = {Doi 10.1103/Physreva.78.013404}, url = {://WOS:000258180300141}, author = {Xu, S. and Crawford, C. W. and Rochester, S. and Yashchuk, V. and Budker, D. and Pines, A.} } @article {277, title = {Temperature-controlled molecular depolarization gates in nuclear magnetic resonance}, journal = {Angewandte Chemie-International Edition}, volume = {47}, year = {2008}, note = {Angew Chem Int Edit308BXTimes Cited:13Cited References Count:19}, pages = {4316-4320}, keywords = {mri}, isbn = {1433-7851}, doi = {Doi 10.1002/Anie.200800382}, url = {://WOS:000256364400007}, author = {Schroder, L. and Chavez, L. and Meldrum, T. and Smith, M. and Lowery, T. J. and Wemmer, D. E. and Pines, A.} } @article {288, title = {Dispersion measurements using time-of-flight remote detection MRI}, journal = {Magnetic Resonance Imaging}, volume = {25}, year = {2007}, note = {Magn Reson Imaging167BHTimes Cited:5Cited References Count:10}, month = {May}, pages = {449-452}, abstract = {

Remote detection nuclear magnetic resonance and magnetic resonance imaging can be used to study fluid flow and dispersion in a porous medium from a purely Eulerian point of view (i.e., in a laboratory frame of reference). Information about fluid displacement is obtained on a macroscopic scale in a long-time regime, while local velocity distributions are averaged out. It is shown how these experiments can be described using the common flow propagator formalism and how experimental data can be analyzed to obtain effective porosity, flow velocity inside the porous medium, fluid dispersion and flow tracing of fluid. (C) 2007 Elsevier Inc. All rights reserved.

}, keywords = {flow}, isbn = {0730-725X}, doi = {Doi 10.1016/J.Mri.2006.11.011}, url = {://WOS:000246425100004}, author = {Granwehr, J. and Harel, E. and Hilty, C. and Garcia, S. and Chavez, L. and Pines, A. and Sen, P. N. and Song, Y. Q.} } @article {289, title = {Sensitivity enhancement by exchange mediated magnetization transfer of the xenon biosensor signal}, journal = {Journal of Magnetic Resonance}, volume = {184}, year = {2007}, note = {J Magn Reson127EUTimes Cited:7Cited References Count:18}, month = {Jan}, pages = {72-77}, abstract = {

Hyperpolarized xenon associated with ligand derivatized cryptophane-A cages has been developed as a NMR based biosensor. To optimize the detection sensitivity we describe use of xenon exchange between the caged and bulk dissolved xenon as an effective signal amplifier. This approach, somewhat analogous to \&$\#$39;remote detection\&$\#$39; described recently, uses the chemical exchange to repeatedly transfer spectroscopic information from caged to bulk xenon, effectively integrating the caged signal. After an optimized integration period, the signal is read out by observation of the bulk magnetization. The spectrum of the caged xenon is reconstructed through use of a variable evolution period before transfer and Fourier analysis of the bulk signal as a function of the evolution time. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {resonance}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2006.09.010}, url = {://WOS:000243568900009}, author = {Garcia, S. and Chavez, L. and Lowery, T. J. and Han, S. I. and Wemmer, D. E. and Pines, A.} } @article {291, title = {Spin coherence transfer in chemical transformations monitored by remote detection NMR}, journal = {Analytical Chemistry}, volume = {79}, year = {2007}, note = {Anal Chem151QATimes Cited:7Cited References Count:39}, month = {Apr 1}, pages = {2806-2811}, abstract = {

We demonstrate a nuclear magnetic resonance (NMR) experiment using continuous flow in a microfluidic channel for studying the transfer of spin coherence in nonequilibrium chemical processes. We use the principle of remote detection, which involves spatially separated NMR encoding and detection coils. As an example, we provide the map of chemical shift correlations for the amino acid alanine as it transitions from the zwitterionic to the anionic form. The presented method uniquely allows for tracking the migration of encoded spins during the course of any chemical transformation and can provide useful information about reaction mechanisms.

}, keywords = {lab}, isbn = {0003-2700}, doi = {Doi 10.1021/Ac062327+}, url = {://WOS:000245304300022}, author = {Anwar, M. S. and Hilty, C. and Chu, C. and Bouchard, L. S. and Pierce, K. L. and Pines, A.} } @article {299, title = {Optimization of xenon biosensors for detection of protein interactions}, journal = {Chembiochem}, volume = {7}, year = {2006}, note = {Chembiochem003SDTimes Cited:39Cited References Count:25}, month = {Jan}, pages = {65-73}, abstract = {

Hyperpolarized Xe-129 NMR spectroscopy can detect the presence of specific low-concentration biomolecular analytes by means of a xenon biosensor that consists of a water-soluble, targeted cryptophane-A cage that encapsulates the xenon. In this work, we use the prototypical biotinylated xenon biosensor to determine the relationship between the molecular composition of the xenon biosensor and the characteristics of protein-bound resonances. The effects of diastereomer overlap, dipole-dipole coupling, chemical-shift anisotropy, xenon exchange, and biosensor conformotional exchange on the protein-bound biosensor signal were assessed. It was found that an optimal protein-bound biosensor signal can be obtained by minimizing the number of biosensor diastereomers and using a flexible linker of appropriate length. Both the line width and sensitivity of chemical shift to protein binding of the xenon biosensor were found to be inversely proportional to linker length.

}, keywords = {complexes}, isbn = {1439-4227}, doi = {Doi 10.1002/Cbic.200500327}, url = {://WOS:000234701000012}, author = {Lowery, T. J. and Garcia, S. and Chavez, L. and Ruiz, E. J. and Wu, T. and Brotin, T. and Dutasta, J. P. and King, D. S. and Schultz, P. G. and Pines, A. and Wemmer, D. E.} } @article {298, title = {SQUID-detected microtesla MRI in the presence of metal}, journal = {Journal of Magnetic Resonance}, volume = {179}, year = {2006}, note = {J Magn Reson035CMTimes Cited:36Cited References Count:23}, month = {Mar}, pages = {146-151}, abstract = {

In magnetic resonance imaging performed at fields of I T and above, the presence of a metal insert can distort the image because of susceptibility differences within the sample and modification of the radiofrequency fields by screening currents. Furthermore, it is not feasible to perform nuclear magnetic resonance (NMR) spectroscopy or acquire a magnetic resonance image if the sample is enclosed in a metal container. Both problems can be overcome by substantially lowering the NMR frequency. Using a microtesla imaging system operating at 2.8 kHz, with a superconducting quantum interference device as the signal detector, we have obtained distortion-free images of a phantom containing a titanium bar and three-dimensional images of an object enclosed in an aluminum can; in both cases high-field images are inaccessible. (c) 2005 Elsevier Inc. All rights reserved.

}, keywords = {nmr}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2005.11.005}, url = {://WOS:000236977600019}, author = {Mossle, M. and Han, S. I. and Myers, W. R. and Lee, S. K. and Kelso, N. and Hatridge, M. and Pines, A. and Clarke, J.} } @article {308, title = {High-resolution NMR spectroscopy with a portable single-sided sensor}, journal = {Science}, volume = {308}, year = {2005}, note = {Science931JTTimes Cited:89Cited References Count:7}, month = {May 27}, pages = {1279-1279}, keywords = {fields}, isbn = {0036-8075}, doi = {Doi 10.1126/Science.1108944}, url = {://WOS:000229482300037}, author = {Perlo, J. and Demas, V. and Casanova, F. and Meriles, C. A. and Reimer, J. and Pines, A. and Blumich, B.} } @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 {309, title = {SQUID-detected in vivo MRI at microtesla magnetic fields}, journal = {Ieee Transactions on Applied Superconductivity}, volume = {15}, year = {2005}, note = {Ieee T Appl SuperconPart 1935FOTimes Cited:24Cited References Count:15}, month = {Jun}, pages = {757-760}, abstract = {

We use a low transition temperature (T(c)) Super-conducting Quantum Interference Device (SQUID) to perform in vivo magnetic resonance imaging (MRI) at magnetic fields around 100 microtesla, corresponding to proton Larmor frequencies of about 5 kHz. In such low fields, broadening of the nuclear magnetic resonance lines due to inhomogeneous magnetic fields and susceptibility variations of the sample are minimized, enabling us to obtain high quality images. To reduce environmental noise the signal is detected by a second-order gradiometer, coupled to the SQUID, and the experiment is surrounded by a 3-mm thick Al shield. To increase the signal-to-noise ratio (SNR), we prepolarize the samples in a field up to 100 mT. Three-dimensional images are acquired in less than 6 minutes with a standard spin-echo phase-encoding sequence. Using encoding gradients of similar to 100 mu T/m we obtain three-dimensional images of bell peppers with a resolution of 2 x 2 x 8 mm(3). Our system is ideally suited to acquiring images of small, peripheral parts of the human body such as hands and arms. In vivo images of an arm, acquired at 132 mu T, show 24-mm sections of the forearm with a resolution of 3 x 3 mm(2). and a SNR of 10. We discuss possible applications of MRI at these low magnetic fields.

}, keywords = {nmr}, isbn = {1051-8223}, doi = {Doi 10.1109/Tasc.2005.850043}, url = {://WOS:000229765300170}, author = {Mossle, M. and Myers, W. R. and Lee, S. K. and Kelso, N. and Hatridge, M. and Pines, A. and Clarke, J.} } @article {314, title = {SQUID-detected MRI at 132 mu T with T(1)-weighted contrast established at 10 mu T-300 mT}, journal = {Magnetic Resonance in Medicine}, volume = {53}, year = {2005}, note = {Magn Reson Med888NETimes Cited:73Cited References Count:20}, month = {Jan}, pages = {9-14}, abstract = {

T(1)-weighted contrast MRI with prepolarization was detected with a superconducting quantum interference device (SQUID). A spin evolution period in a variable field between prepolarization and detection enabled the measurement of T(1) in fields between 1.7 muT and 300 mT; T, dispersion curves of agarose gel samples over five decades in frequency were obtained. SQUID detection at 5.6 kHz drastically reduces the field homogeneity requirements compared to conventional field-cycling methods using Faraday coil detection. This allows T(1) dispersion measurements to be easily combined with MRI, so that T(1) in a wide range of fields can be used for tissue contrast. Images of gel phantoms with T(1)-weighted contrast at four different fields between 10 muT and 300 mT demonstrated dramatic contrast enhancement in low fields. A modified inversion recovery technique further enhanced the contrast by selectively suppressing the signal contribution for a specific value of the low-field T(1). Published 2004 Wiley-Liss, Inc.

}, keywords = {dispersion}, isbn = {0740-3194}, doi = {Doi 10.1002/Mrm.20316}, url = {://WOS:000226380700003}, author = {Lee, S. K. and Mossle, M. and Myers, W. and Kelso, N. and Trabesinger, A. H. and Pines, A. and Clarke, J.} } @article {320, title = {Xenon NMR as a probe for microporous and mesoporous solids, polymers, liquid crystals, solutions, flames, proteins, imaging}, journal = {Actualite Chimique}, year = {2005}, note = {Actual ChimiqueSuppl. 287952GHTimes Cited:3Cited References Count:89}, month = {Jun}, pages = {16-34}, abstract = {

We present in this paper some examples of the applications of the Nuclear Magnetic Resonance (NMR) of xenon used as a probe in the study of different chemical environments: determination of the porosity of micro-and mesoporous solids, evaluation of the concentrations and sizes of amorphous domains in solid polymers, characterization of liquid crystals, study of combustion processes at high temperature, determination of the structure and dynamics of organic systems and proteins in solution, assessment of cerebral blood flow.

}, keywords = {silica-gels}, isbn = {0151-9093}, url = {://WOS:000230991500005}, author = {Bartik, K. and Choquet, P. and Constantinesco, A. and Duhamel, G. and Fraissard, J. and Hyacinthe, J. N. and Jokisaari, J. and Locci, E. and Lowery, T. J. and Luhmer, M. and Meersmann, T. and Moudrakovski, I. L. and Pavlovskaya, G. E. and Pierce, K. L. and Pines, A. and Ripmeester, J. A. and Telkki, V. V. and Veeman, W. S.} } @article {331, title = {Microtesla MRI with a superconducting quantum interference device}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {101}, year = {2004}, note = {P Natl Acad Sci USA823ZCTimes Cited:76Cited References Count:29}, month = {May 25}, pages = {7857-7861}, abstract = {

MRI scanners enable fast, noninvasive, and high-resolution imaging of organs and soft tissue. The images are reconstructed from NMR signals generated by nuclear spins that precess in a static magnetic field B(0) in the presence of magnetic field gradients. Most clinical MRI scanners operate at a magnetic field B(0) = 1.5 T, corresponding to a proton resonance frequency of 64 MHz. Because these systems rely on large superconducting magnets, they are costly and demanding of infrastructure. On the other hand, low-field imagers have the potential to be less expensive, less confining, and more mobile. The major obstacle is the intrinsically low sensitivity of the low-field NMR experiment. Here, we show that prepolarization of the nuclear spins and detection with a superconducting quantum interference device (SQUID) yield a signal that is independent of B(0), allowing acquisition of high-resolution MRIs in microtesla fields. Reduction of the strength of the measurement field eliminates inhomogeneous broadening of the NMR lines, resulting in enhanced signal-to-noise ratio and spatial resolution for a fixed strength of the magnetic field gradients used to encode the image. We present high-resolution images of phantoms and other samples and T(1)-weighted contrast images acquired in highly inhomogeneous magnetic fields of 132 muT; here, T, is the spin-lattice relaxation time. These techniques could readily be adapted to existing multichannel SQUID systems used for magnetic source imaging of brain signals. Further potential applications include low-cost systems for tumor screening and imaging peripheral regions of the body.

}, keywords = {system}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0402382101}, url = {://WOS:000221652000005}, author = {McDermott, R. and Lee, S. K. and ten Haken, B. and Trabesinger, A. H. and Pines, A. and Clarke, J.} } @article {322, title = {SQUID-detected liquid state NMR in microtesla fields}, journal = {Journal of Physical Chemistry A}, volume = {108}, year = {2004}, note = {J Phys Chem A772FTTimes Cited:32Cited References Count:36}, month = {Feb 12}, pages = {957-963}, abstract = {

Nuclear magnetic resonance (NMR) experiments performed in magnetic fields on the order of microtesla yield line widths comparable to the lifetime limit even in grossly inhomogeneous magnets. The potential loss in sensitivity is overcome by combining prepolarization in fields on the order of millitesla and signal detection with a Superconducting Quantum Interference Device (SQUID). The enhanced spectral resolution attainable in microtesla fields enables NMR studies of pure liquids and solutions without the need for strong magnets. We have investigated a variety of heteronuclear systems in both the weak and strong J-coupling regimes. Six different nuclear species have been detected with the same experimental apparatus. NMR signals of thermally polarized protons were obtained in fields as low as 554 nT.

}, keywords = {water}, isbn = {1089-5639}, doi = {Doi 10.1021/Jp035181g}, url = {://WOS:000188831500005}, author = {Trabesinger, A. H. and McDermott, R. and Lee, S. K. and M{\"u}ck, M. and Clarke, J. and Pines, A.} } @article {332, title = {SQUID-detected magnetic resonance imaging in microtesla magnetic fields}, journal = {Journal of Low Temperature Physics}, volume = {135}, year = {2004}, note = {J Low Temp Phys824TWTimes Cited:37Cited References Count:34}, month = {Jun}, pages = {793-821}, abstract = {

We describe studies of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) of liquid samples at room temperature in microtesla magnetic fields. The nuclear spins are prepolarized in a strong transient field. The magnetic signals generated by the precessing spins, which range in frequency from tens of Hz to several kHz, are detected by a low-transition temperature dc SQUID (Superconducting QUantum Interference Device) coupled to an untuned, superconducting flux transformer configured as an axial gradiometer. The combination of prepolarization and frequency-independent detector sensitivity results in a high signal-to-noise ratio and high spectral resolution (similar to 1 Hz) even in grossly inhomogeneous magnetic fields. In the NMR experiments, the high spectral resolution enables us to detect the 10-Hz splitting of the spectrum of protons due to their scalar coupling to a P-31 nucleus. Furthermore, the broadband detection scheme combined with a non-resonant field-reversal spin echo allows the simultaneous observation of signals from protons and P-31 nuclei, even though their NMR resonance frequencies differ by a factor of 2.5. We extend our methodology to MRI in microtesla fields, where the high spectral resolution translates into high spatial resolution. We demonstrate two-dimensional images of a mineral oil phantom and slices of peppers, with a spatial resolution of about 1 mm. We also image an intact pepper using slice selection, again with 1-mm, resolution. A further experiments we demonstrate T-1-contrast imaging of a water phantom, some parts of which were doped with a paramagnetic salt to reduce the longitudinal relaxation time T-1. Possible applications of this MRI technique include screening for tumors and integration with existing multichannel SQUID systems for brain imaging.

}, keywords = {mri}, isbn = {0022-2291}, doi = {Doi 10.1023/B:Jolt.0000029519.09286.C5}, url = {://WOS:000221710600023}, author = {McDermott, R. and Kelso, N. and Lee, S. K. and Mossle, M. and M{\"u}ck, M. and Myers, W. and ten Haken, B. and Seton, H. C. and Trabesinger, A. H. and Pines, A. and Clarke, J.} } @article {342, title = {Inclusion complexes oriented in thermotropic liquid-crystalline solvents studied with carbon-13 NMR}, journal = {Journal of Physical Chemistry B}, volume = {107}, year = {2003}, note = {J Phys Chem B743MATimes Cited:11Cited References Count:19}, month = {Nov 20}, pages = {12558-12561}, abstract = {

The inclusion complex of cryptophane-A and chloroform dissolved in two nonchiral liquid-crystalline environments was investigated via C-13 NMR. Stable solutions of oriented complexes were prepared using aromatic (ZLI 1132) and aliphatic (ZLI 1695) thermotropic nematic liquid crystals as solvents; ordering of the complexes was manifested by the H-1-C-13 dipolar splitting of the C-13 resonance of labeled chloroform. In both solutions, the dipolar splitting for the bound ligands was substantially larger than that obtained for the free ligands, indicating a significant increase in ligand ordering upon complexation despite the absence of direct contact with the oriented solvent molecules. A similar enhancement in ordering was observed for complexed ligands compared to that for free ligands in both liquid-crystalline solvents. Also, the application of heteronuclear decoupling to the ZLI 1695 solution resulted in a reduced line width for the bound C-13 chloroform resonance, suggesting that a significant component of the observed line broadening may originate from intermolecular couplings between host and guest molecules. These results demonstrate the potential for using restored dipolar couplings to investigate structural and dynamical aspects of inclusion complexes in solution.

}, keywords = {xe-129}, isbn = {1520-6106}, doi = {Doi 10.1021/Jp030431e}, url = {://WOS:000186574500003}, author = {Marjanska, M. and Goodson, B. M. and Castiglione, F. and Pines, A.} } @article {361, title = {Efficient triple-quantum excitation in modified RIACT MQMAS NMR for I=3/2 nuclei}, journal = {Journal of Magnetic Resonance}, volume = {154}, year = {2002}, note = {J Magn Reson527MFTimes Cited:15Cited References Count:31}, month = {Feb}, pages = {196-204}, abstract = {

A new approach involving the creation of triple-quantum (TQ) coherences from both TQ and central transitions (CT) is investigated, in order to enhance the efficiency of triple-quantum excitation for I = 3/2 nuclei. The RIACT excitation scheme, a soft pi/2 and hard spin-locking pulse, is shown to induce both adiabatic coherence transfer between CT and TQ coherences and TQ nutation. By combining the RIACT scheme with the presaturation of the satellite transitions, a significant improvement in the TQ excitation can be achieved mainly through enhanced CT polarization via the RIACT mechanism, in particular for nuclei with moderate to large quadrupole coupling constants (greater than or equal to2.0 MHz). There also exists a nontrivial contribution from the TQ transition, which depends on the size of the quadrupole interaction. (C) 2002 Elsevier Science (USA).

}, keywords = {coherence}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.2001.2471}, url = {://WOS:000174189300005}, author = {Lim, K. H. and Charpentier, T. 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 {357, title = {Liquid-state NMR and scalar couplings in microtesla magnetic fields}, journal = {Science}, volume = {295}, year = {2002}, note = {Science534ADTimes Cited:140Cited References Count:20}, month = {Mar 22}, pages = {2247-2249}, abstract = {

We obtained nuclear magnetic resonance (NMR) spectra of liquids in fields of a few microtesla, using prepolarization in fields of a few millitesta and detection with a dc superconducting quantum interference device (SQUID). Because the sensitivity of the SQUID is frequency independent, we enhanced both signal-to-noise ratio and spectral resolution by detecting the NMR signal in extremely tow magnetic fields, where the NMR tines become very narrow even for grossly inhomogeneous measurement fields. In the absence of chemical shifts, proton-phosphorous scalar (J) couplings have been detected, indicating the presence of specific covalent bonds. This observation opens the possibility for \"pure J spectroscopy\" as a diagnostic tool, for the detection of molecules in low magnetic fields.

}, keywords = {resonance}, isbn = {0036-8075}, doi = {Doi 10.1126/Science.1069280}, url = {://WOS:000174561700039}, author = {McDermott, R. and Trabesinger, A. H. and M{\"u}ck, M. and Hahn, E. L. and Pines, A. and Clarke, J.} } @article {358, title = {Measurement of dipolar couplings in partially oriented molecules by local field NMR spectroscopy with low-power decoupling}, journal = {Journal of Magnetic Resonance}, volume = {158}, year = {2002}, note = {J Magn Reson619VETimes Cited:8Cited References Count:23}, month = {Sep-Oct}, pages = {52-59}, abstract = {

Low-power phase-modulated Lee-Goldburg homonuclear decoupling was used to record PDLF spectra of fluorine-substituted benzene derivatives dissolved in nematic thermotropic liquid crystalline solvents. The low-power decoupling minimizes sample heating during RE irradiation while still achieving highly resolved PDLF spectra. The method is illustrated by recording spectra for 1,3-dichloro-4-fluoro-5-nitrobenzene, 1,3-dichloro-4-fluorobenzene, and 1, 2-difluoro benzene dissolved in different nematic solvents. (C) 2002 Elsevier Science (USA). All rights reserved.

}, keywords = {resolution}, isbn = {1090-7807}, doi = {Doi 10.1016/S1090-7807(02)00059-9}, url = {://WOS:000179497500006}, author = {Marjanska, M. and Castiglione, F. and Walls, J. D. and Pines, A.} } @article {349, title = {Selective excitation in dipole coupled systems}, journal = {Chemical Physics Letters}, volume = {357}, year = {2002}, note = {Chem Phys Lett558GVTimes Cited:5Cited References Count:22}, month = {May 10}, pages = {241-248}, abstract = {

In this Letter the possibility of selective excitation in coupled multispin systems is studied theoretically. A general method of transforming any selective pulse developed for uncoupled systems into a form that is selective in coupled systems is presented. This is accomplished by adding a small perturbation to a decoupling radiofrequency (RF) field. When viewed in an interaction frame given by the decoupling RF field, this method generates, in an averaged sense, a propagator similar to the propagator of uncoupled spins under a shaped RF pulse. Preliminary experimental results are presented for the case of selective excitation in proton nuclear magnetic resonance in liquid crystals. (C) 2002 Elsevier Science B.V. All rights reserved.

}, keywords = {spin-diffusion}, isbn = {0009-2614}, doi = {Doi 10.1016/S0009-2614(02)00493-1}, url = {://WOS:000175958700012}, author = {Walls, J. D. and Marjanska, M. and Sakellariou, D. and Castiglione, F. 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.} } @article {370, title = {Solid-state NMR studies of the secondary structure of a mutant prion protein fragment of 55 residues that induces neurodegeneration}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {98}, year = {2001}, note = {P Natl Acad Sci USA476PCTimes Cited:51Cited References Count:26}, month = {Sep 25}, pages = {11686-11690}, abstract = {

The secondary structure of a 55-residue fragment of the mouse prion protein, MoPrP(89-143), was studied in randomly aggregated (dried from water) and fibrillar (precipitated from water/ acetonitrile) forms by C-13 solid-state NMR. Recent studies have shown that the fibrillar form of the P101L mutant of MoPrP(89-143) is capable of inducing prion disease in transgenic mice, whereas unaggregated or randomly aggregated samples do not provoke disease. Through analysis of C-13 chemical shifts, we have determined that both wild-type and mutant sequence MoPrP(89-143) form a mixture of beta -sheet and alpha -helical conformations in the randomly aggregated state although the beta -sheet content in MoPrP(89-143, P101L) is significantly higher than in the wild-type peptide. In a fibrillar state, MoPrP(89-143, P101L) is completely converted into beta -sheet, suggesting that the formation of a specific beta -sheet structure may be required for the peptide to induce disease. Studies of an analogous peptide from Syrian hamster PrP verify that sequence alterations in residues 101-117 affect the conformation of aggregated forms of the peptides.

}, keywords = {diseases}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.201404298}, url = {://WOS:000171237100125}, author = {Laws, D. D. and Bitter, H. M. L. and Liu, K. and Ball, H. L. and Kaneko, K. and Wille, H. and Cohen, F. E. and Prusiner, S. B. and Pines, A. and Wemmer, D. E.} } @article {376, title = {Exploring single-file diffusion in one-dimensional nanochannels by laser-polarized Xe-129 NMR spectroscopy (Cover Article)}, journal = {Journal of Physical Chemistry A}, volume = {104}, year = {2000}, note = {J Phys Chem A383EFTimes Cited:75Cited References Count:22}, month = {Dec 21}, pages = {11665-11670}, abstract = {

Single-file diffusion behavior is expected for atoms and molecules in one-dimensional gas phases of nanochannels with transverse dimensions that do not allow for the particles to bypass each other. Although single-file diffusion may play an important role in a wide range of industrial catalytic, geologic, and biological processes, experimental evidence is scarce despite the fact that the dynamics differ substantially from ordinary diffusion. We demonstrate the application of continuous-flow laser-polarized Xe-129 NMR spectroscopy for the study of gas transport into the effectively one-dimensional channels of a microporous material. The novel methodology makes it possible to monitor diffusion over a time scale of tens of seconds, often inaccessible by conventional NMR experiments. The technique can also be applied to systems with very small mobility factors or diffusion constants that are difficult to determine by currently available methods for diffusion measurement. Experiments using xenon in nanochannel systems can distinguish between unidirectional diffusion and single-file diffusion. The experimental observations indicate that single-file behavior for xenon in an organic nanochannel is persistent even at long diffusion times of over tens of seconds. Finally;using continuous flow laser-polarized Xe-129 NMR spectroscopy, we describe an intriguing correlation between the observed NMR line shape of xenon within the nanochannels and the gas transport into these channels.

}, keywords = {model}, isbn = {1089-5639}, doi = {Doi 10.1021/Jp002322v}, url = {://WOS:000165869600001}, author = {Meersmann, T. and Logan, J. W. and Simonutti, R. and Caldarelli, S. and Comotti, A. and Sozzani, P. and Kaiser, L. G. and Pines, A.} } @article {374, title = {A porous crystalline molecular solid explored by hyperpolarized xenon}, journal = {Angewandte Chemie-International Edition}, volume = {39}, year = {2000}, note = {Angew Chem Int Edit343KUTimes Cited:116Cited References Count:38}, pages = {2695-2698}, keywords = {c-13}, isbn = {1433-7851}, doi = {Doi 10.1002/1521-3773(20000804)39:15<2695::Aid-Anie2695>3.0.Co;2-M}, url = {://WOS:000088702200008}, author = {Sozzani, P. and Comotti, A. and Simonutti, R. and Meersmann, T. and Logan, J. W. and Pines, A.} } @article {382, title = {High-T-c SQUIDs for low-field NMR and MRI of room temperature samples}, journal = {Ieee Transactions on Applied Superconductivity}, volume = {9}, year = {1999}, note = {Ieee T Appl SuperconPart 3225MCTimes Cited:5Cited References Count:18}, month = {Jun}, pages = {4424-4427}, abstract = {

We have constructed a high-T-c SQUID spectrometer to detect NMR signals from samples at room temperature in magnetic fields up to 3 mT. The multiloop SQUID magnetometer has a system noise of about 30 fT/Hz(1/2) at the relevant frequencies of 2 to 100 kHz, The magnetometer is operated in vacuum at 77 K, and is separated from the sample, which is less than 1.5 mm away, by a sapphire window, In a magnetic field of 2 mT we can detect the proton spin echo at 86 kHz without signal averaging. This sensitivity enables us to obtain one-dimensional images. In addition, we present data on hyperpolarized Xe-129, which has an optically pumped polarization of several percent.

}, keywords = {frequencies}, isbn = {1051-8223}, doi = {Doi 10.1109/77.784006}, url = {://WOS:000081964500386}, author = {Schlenga, K. and McDermott, R. F. and Clarke, J. and de Souza, R. E. and Wong-Foy, A. and Pines, A.} } @article {383, title = {Low-field magnetic resonance imaging with a high-T-c dc superconducting quantum interference device}, journal = {Applied Physics Letters}, volume = {75}, year = {1999}, note = {Appl Phys Lett259URTimes Cited:49Cited References Count:19}, month = {Dec 6}, pages = {3695-3697}, abstract = {

A spectrometer incorporating a high transition temperature dc superconducting quantum interference device (SQUID) is used to obtain nuclear magnetic resonance signals from protons in mineral oil at room temperature in fields up to 3 mT. The spatial separation between the SQUID magnetometer at 77 K and the sample at room temperature is less than 1 mm. At 2 mT, the signal is easily resolved in a single scan. Two-dimensional images of samples consisting of pieces of lucite or glass immersed in mineral oil are obtained at 2 mT. (C) 1999 American Institute of Physics. [S0003-6951(99)03649-9].

}, keywords = {mri}, isbn = {0003-6951}, doi = {Doi 10.1063/1.125432}, url = {://WOS:000083912800035}, author = {Schlenga, K. and McDermott, R. and Clarke, J. and de Souza, R. E. and Wong-Foy, A. and Pines, A.} } @article {387, title = {NMR and MRI obtained with high transition temperature DC SQUIDs}, journal = {Journal of the Brazilian Chemical Society}, volume = {10}, year = {1999}, note = {J Brazil Chem Soc259BETimes Cited:11Cited References Count:30}, month = {Jul-Aug}, pages = {307-312}, abstract = {

We have measured nuclear magnetic resonance (NMR) signals from several samples at room temperature in magnetic fields ranging from about 0.05 mT to 2 mT using a spectrometer based on a high-T-c de SQUID (high transition temperature de Superconducting QUantum Interference Device). We are able to observe proton signals from 1 mL of mineral oil in 2 mT in a single transient. The sensitivity of this system has also allowed the detection of proton NMR at magnetic fields as low as 0.059 mT, which is comparable to the Earth\&$\#$39;s field. Such results make possible a number of new experiments in magnetic resonance imaging (MRI). We present a two-dimensional image of a phantom filled with mineral oil obtained in a field of 2 mT.

}, keywords = {system}, isbn = {0103-5053}, url = {://WOS:000083873500009}, author = {de Souza, R. E. and Schlenga, K. and Wong-Foy, A. and McDermott, R. and Pines, A. and Clarke, J.} } @article {384, title = {Study of xenon binding in cryptophane-A using laser-induced NMR polarization enhancement}, journal = {Journal of the American Chemical Society}, volume = {121}, year = {1999}, note = {J Am Chem Soc189BTTimes Cited:73Cited References Count:64}, month = {Apr 14}, pages = {3502-3512}, abstract = {

In solution, spin-polarization transfer between laser-polarized xenon and the hydrogen nuclei of nearby molecules leads to signal enhancements in the resolved H-1 NMR spectrum, offering new opportunities for probing the chemical environment of xenon atoms. Following binding of laser-polarized xenon to molecules of cryptophane-A, selective enhancements of the H-1 NMR signals were observed. A theoretical framework for the interpretation of such experimental results is provided, and the spin polarization-induced nuclear Overhauser effects are shown to yield information about the molecular environment of xenon. The observed selective H-1 enhancements allowed xenon-proton internuclear distances to be estimated. These distances reveal structural characteristics of the complex, including the preferred molecular conformations adopted by cryptophane-A upon binding of xenon.

}, keywords = {SPECTROSCOPY}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja9841916}, url = {://WOS:000079884800033}, author = {Luhmer, M. and Goodson, B. M. and Song, Y. Q. and Laws, D. D. and Kaiser, L. and Cyrier, M. C. and Pines, A.} } @article {402, title = {A high-resolution(17)O NMR study of siliceous zeolite faujasite}, journal = {Journal of the American Chemical Society}, volume = {120}, year = {1998}, note = {J Am Chem SocZj097Times Cited:66Cited References Count:19}, month = {Apr 15}, pages = {3510-3511}, keywords = {workstation computers}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja9743001}, url = {://WOS:000073179200032}, author = {Bull, L. M. and Cheetham, A. K. and Anupold, T. and Reinhold, A. and Samoson, A. and Sauer, J. and Bussemer, B. and Lee, Y. and Gann, S. and Shore, J. and Pines, A. and Dupree, R.} } @article {405, title = {Low field magnetic resonance images of polarized noble gases obtained with a dc superconducting quantum interference device}, journal = {Applied Physics Letters}, volume = {72}, year = {1998}, note = {Appl Phys LettZg930Times Cited:37Cited References Count:24}, month = {Apr 13}, pages = {1908-1910}, abstract = {

Using a low transition temperature superconducting quantum interference device as a detector, we have obtained magnetic resonance images of laser-polarized He-3 gas and solid Xe-129 at 4.2 K in magnetic fields as low as 0.54 mT (He-3) and 1 mT (Xe-129), corresponding to Larmor frequencies of 17.6 and 11.8 kHz, respectively. The experimental resolution of the images is similar to 500 mu m for He-3 ill the gas phase and similar to 950 mu m for Xe-129 in the solid state. (C) 1998 American Institute of Physics.

}, keywords = {mri}, isbn = {0003-6951}, doi = {Doi 10.1063/1.121223}, url = {://WOS:000073054300038}, author = {Augustine, M. P. and Wong-Foy, A. and Yarger, J. L. and Tomaselli, M. and Pines, A. and TonThat, D. M. and Clarke, J.} } @article {396, title = {NMR of supercritical laser-polarized xenon}, journal = {Chemical Physics Letters}, volume = {292}, year = {1998}, note = {Chem Phys Lett112EZTimes Cited:25Cited References Count:35}, month = {Aug 14}, pages = {686-690}, abstract = {

The feasibility of producing supercritical laser-polarized xenon for nuclear magnetic resonance (NMR) investigations was studied. Using a high-pressure capillary tube, a supercritical xenon sample (52 degrees C, 65 atm) was produced with a Xe-129 polarization approximately 140 times the equilibrium value. The polarization was observed to last for hundreds of seconds, in agreement with previous studies. These preliminary results suggest that supercritical laser-polarized xenon may be used as a polarizing solvent for numerous NMR applications. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

}, keywords = {gas}, isbn = {0009-2614}, doi = {Doi 10.1016/S0009-2614(98)00732-5}, url = {://WOS:000075482300049}, author = {Haake, M. and Goodson, B. M. and Laws, D. D. and Brunner, E. and Cyrier, M. C. and Havlin, R. H. and Pines, A.} } @article {420, title = {In vivo NMR and MRI using injection delivery of laser-polarized xenon}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {94}, year = {1997}, note = {P Natl Acad Sci USAYn574Times Cited:55Cited References Count:39}, month = {Dec 23}, pages = {14725-14729}, abstract = {

Because xenon NMR is highly sensitive to the local environment, laser-polarized xenon could be a unique probe of living tissues. Realization of clinical and medical science applications beyond lung airspace imaging requires methods of efficient delivery of laser-polarized xenon to tissues, because of the short spin-lattice relaxation times and relatively low concentrations of xenon attainable in the body. Preliminary results from the application of a polarized xenon injection technique for in vivo Xe-129 NMR/MRI are extrapolated along with a simple model of xenon transit to show that the peak local concentration of polarized xenon delivered to tissues by injection may exceed that delivered by respiration by severalfold.

}, keywords = {humans}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.94.26.14725}, url = {://WOS:000071182800090}, author = {Goodson, B. M. and Song, Y. Q. and Taylor, R. E. and Schepkin, V. D. and Brennan, K. M. and Chingas, G. C. and Budinger, T. F. and Navon, G. and Pines, A.} } @article {408, title = {Low magnetic field dynamic nuclear polarization using a single-coil two-channel probe}, journal = {Review of Scientific Instruments}, volume = {68}, year = {1997}, note = {Rev Sci InstrumWp247Times Cited:4Cited References Count:29}, month = {Mar}, pages = {1527-1531}, abstract = {

We describe the design and construction of a single-coil, two-channel probe for the detection of low-field magnetic resonance using dynamic nuclear polarization (DNP). The high-frequency channel of the probe, which is used to saturate the electron spins, is tuned to the electron Larmor frequency, 75 MHz at 2.7 mT, and matched to 50 Omega. Low-field, H-1 nuclear magnetic resonance (NMR) is detected through the second, low-frequency channel at frequencies \<1 MHz. The performance of the probe was tested by measuring the DNP of protons in a manganese (II) chloride solution at 2.7 mT. At the proton NMR frequency of 120 kHz, the signal amplitude was enhanced over the value without DNP by a factor of about 200. (C) 1997 American Institute of Physics.

}, keywords = {nmr}, isbn = {0034-6748}, doi = {Doi 10.1063/1.1147641}, url = {://WOS:A1997WP24700033}, author = {TonThat, D. M. and Augustine, M. P. and Pines, A. and Clarke, J.} } @article {407, title = {SQUID detected NMR of laser-polarized xenon at 4.2 K and at frequencies down to 200 Hz}, journal = {Chemical Physics Letters}, volume = {272}, year = {1997}, note = {Chem Phys LettXh440Times Cited:18Cited References Count:32}, month = {Jun 27}, pages = {245-249}, abstract = {

A spectrometer based on a dc SQUID (superconducting quantum interference device) was used to record nuclear magnetic resonance signals from laser-polarized Xe-129 at 4.2 K and at frequencies ranging from about 200 Hz to 110 kHz in magnetic fields varying from about 0.02 to 9 mT. The Xe-129 resonance linewidths were found to increase with increasing magnetic field, and, at a given field, to increase with higher Xe-129 concentration. The spin-lattice relaxation times were observed to decrease from similar to 8000 s at 5 mT to similar to 2000 s at fields below 0.05 mT. Such long relaxation times make possible a variety of spin polarization transfer experiments. (C) 1997 Published by Elsevier Science B.V.

}, keywords = {relaxation}, isbn = {0009-2614}, doi = {Doi 10.1016/S0009-2614(97)88016-5}, url = {://WOS:A1997XH44000017}, author = {TonThat, D. M. and Ziegeweid, M. and Song, Y. Q. and Munson, E. J. and Appelt, S. and Pines, A. and Clarke, J.} } @article {427, title = {Measurement and assignment of long-range C-H dipolar couplings in liquid crystals by two-dimensional NMR spectroscopy}, journal = {Journal of Physical Chemistry}, volume = {100}, year = {1996}, note = {J Phys Chem-UsVe373Times Cited:41Cited References Count:22}, month = {Aug 29}, pages = {14815-14822}, abstract = {

We describe multidimensional NMR techniques to measure and assign C-13-H-1 dipolar couplings in nematic liquid crystals with high resolution. In particular, dipolar couplings between aromatic and aliphatic sites are extracted, providing valuable information on the structural correlations between these two components of thermotropic liquid crystal molecules. The NMR techniques are demonstrated on 4-pentyl-4\&$\#$39;-biphenylcarbonitrile (5CB), a well-characterized room-temperature nematic liquid crystal. Proton-detected local-field NMR spectroscopy is employed to obtain highly resolved C-H dipolar couplings that are separated according to the chemical shifts of the carbon sites. Each C-13 cross section in the 2D spectra exhibits several doublet splittings, with the largest one resulting from the directly bonded C-H coupling, The smaller splittings originate from the long-range C-H dipolar couplings and can be assigned qualitatively by a chemical shift heteronuclear correlation (HETCOR) experiment. The HETCOR experiment incorporates a mixing period for proton spin diffusion to occur, so that maximal polarization transfer can be achieved between the unbonded C-13 and H-1 nuclei. To assign the long-range C-H couplings quantitatively, we combined these two techniques into a novel reduced-3D experiment, in which the H-1 chemical shift-displaced C-H dipolar couplings are correlated with the C-13 chemical shifts. The time domain of this experiment involves separate but synchronous incrementation of the evolution periods for the C-H dipolar couplings and the H-1 chemical shifts, with a variable ratio of the respective dwell times to optimize the resolution and facilitate resonance assignment in the spectrum.

}, keywords = {shape}, isbn = {0022-3654}, doi = {Doi 10.1021/Jp960972m}, url = {://WOS:A1996VE37300036}, author = {Hong, M. and Pines, A. and Caldarelli, S.} } @article {432, title = {Measurement of carbon-proton dipolar couplings in liquid crystals by local dipolar field NMR spectroscopy}, journal = {Journal of Physical Chemistry}, volume = {100}, year = {1996}, note = {J Phys Chem-UsVv354Times Cited:54Cited References Count:31}, month = {Nov 28}, pages = {18696-18701}, abstract = {

The performance of several different two-dimensional NMR methods for the measurement of carbon-proton dipolar couplings in liquid crystalline phases is analyzed. Proton-detected local field spectroscopy allows the measurements of short range C-H couplings, which correspond to directly bond pairs, by direct inspection of the spectra. Off magic angle (OMAS) spinning techniques can be applied to anisotropic phases that can be oriented mechanically at an angle to the magnetic field, such as nematic phases. The consequent scaling of the chemical shift anisotropy and dipolar couplings can be used to resolve otherwise overlapping resonances, Moreover, an estimate of the accuracy of the technique can be achieved by performing a series of OMAS experiments with different sample orientations.

}, keywords = {solids}, isbn = {0022-3654}, doi = {Doi 10.1021/Jp962023z}, url = {://WOS:A1996VV35400008}, author = {Caldarelli, S. and Hong, M. and Emsley, L. and Pines, A.} } @article {434, title = {Rotational diffusion measurements of suspended colloidal particles using two-dimensional exchange nuclear magnetic resonance}, journal = {Journal of Chemical Physics}, volume = {104}, year = {1996}, note = {J Chem PhysTn837Times Cited:13Cited References Count:24}, month = {Jan 8}, pages = {509-520}, abstract = {

We present here an experimental and theoretical study of the application of two-dimensional exchange nuclear magnetic resonance spectroscopy (NMR) to the investigation of the rotational diffusion of colloidal particles. The theoretical discussion includes the nature of the NMR frequency time-correlation function where the NMR interaction is represented by the chemical shift anisotropy (CSA). Time-correlation functions for the isotropic rotational diffusion of a suspension of colloidal particles containing single and multiple sites are derived in addition to time-correlation functions for the rotational diffusion of a suspension of symmetric top particles containing an isotropic distribution of a single CSA interaction. Simulations of two-dimensional exchange spectra for particles undergoing isotropic rotational diffusion are presented. We performed two-dimensional exchange NMR experiments on a colloidal suspension of spherical poly(methyl methacrylate) (PMMA) particles which were synthesized with a 20\% enrichment in C-13 at the carbonyl site. Rotational diffusion time-correlation functions determined from the experimental exchange spectra are consistent with the composition of the colloidal suspension. Detailed explanations of the syntheses of the enriched methyl C-13-(carbonyl)-methacrylate monomer and the small quantities of 20\% enriched C-13-(carbonyl)-poly(methyl methacrylate) microspheres used for this study are presented. (C) 1996 American Institute of Physics.

}, keywords = {scattering}, isbn = {0021-9606}, doi = {Doi 10.1063/1.470847}, url = {://WOS:A1996TN83700009}, author = {Barrall, G. A. and Schmidt-Rohr, K. and Lee, Y. K. and Landfester, K. and Zimmermann, H. and Chingas, G. C. and Pines, A.} } @inbook {436, title = {Synthetic Peptides Model α - Helix - β - Sheet Conformational Changes in the Prion Protien}, booktitle = {Peptides: Chemistry, Structure and Biology}, year = {1996}, pages = {468-470}, publisher = {Mayflower Scientific Ltd.}, organization = {Mayflower Scientific Ltd.}, author = {Baldwin, M.A. and Zhang, H. and Bekker, T. and Zhou, S. and Nguyen, J. and Kolbert, A.C. and Heller, J. and James, T.L. and Wemmer, D.E. and Pines, A. and Cohen, F.E. and Prusiner, S.B.}, editor = {Hidges, Pravin T.P Kaumaya and Robert S.} } @article {441, title = {Magnetic-Resonance Evidence for Metallic State in Highly Conducting Polyaniline}, journal = {Synthetic Metals}, volume = {69}, year = {1995}, note = {Synthetic MetQl601Times Cited:9Cited References Count:12}, month = {Mar 1}, pages = {243-244}, abstract = {

Polyaniline doped with camphor sulfonic acid (PANI-CSA) has been shown to yield a material which, after processing from solutions in meta-cresol, exhibit a temperature independent magnetic susceptibility down to 50K. Below 50K a Curie like contribution sets in. We also report C-13 NMR experiments which clearly show that the C-13 spin lattice relaxation rates obey the Korringa relation for relaxation via the hyperfine coupling to conduction electrons.

}, keywords = {polymers}, isbn = {0379-6779}, doi = {Doi 10.1016/0379-6779(94)02435-2}, url = {://WOS:A1995QL60100097}, author = {Sariciftci, N. S. and Kolbert, A. C. and Cao, Y. and Heeger, A. J. and Pines, A.} } @article {440, title = {Orientation and Motion of Tetrahydrofuran in Graphite-Intercalation Compounds - Proton Nmr-Studies of Cs(Thf)(1.3)C-24 and K(Thf)(2.5)C-24}, journal = {Journal of Physical Chemistry}, volume = {99}, year = {1995}, note = {J Phys Chem-UsRg562Times Cited:5Cited References Count:31}, month = {Jun 29}, pages = {10565-10572}, abstract = {

The orientation and motion of tetrahydrofuran (THF) in the ternary graphite intercalation compounds Cs-(THF)(1.3)C-24 and K(THF)(2.5)C-24 have been studied by proton NMR. Simulations of the NMR spectra indicate that the THF molecules in CS(THF)(1.3)C-24 have their mean planes oriented parallel to the layers of the host lattice, while the THF molecules in K(THF)(2.5)C-24 have their mean planes oriented at an angle between 50 degrees and 75 degrees from the graphite layers. The proton NMR spectra of both compounds show evidence that the THF molecules rotate about the normal to the graphite layers and confirm X-ray diffraction studies showing a degree of orientational disorder in the samples, corresponding to a mosaic spread in the graphite layer orientation. The conformation of the intercalated THF was studied by simulating the experimental NMR spectra using models for the conformational motion of THF. Simulations indicate that the conformation of intercalated THF is different than gas or liquid phase THF, which has been found to have a ring puckering amplitude of 0.38-0.44 Angstrom and to undergo nearly free pseudorotation through a series of conformations. Best agreement between simulated and experimental NMR spectra of Cs(THF)(1.3)C-24 was Obtained with THF interconverting between two conformations of C-s symmetry and a puckering amplitude of 0.30 Angstrom. Free or slightly hindered pseudorotation of THF (observed in liquid or gaseous THF) in this compound produces simulated spectra that differ significantly from the experimental spectra. Simulated proton NMR spectra of K(THF)(2.5)C-24 using conformations of C-s symmetry or free or slightly hindered pseudorotation of THF do not fit the experimental spectra sufficiently well to allow distinction between the conformational motions or to exclude other possible motions.

}, keywords = {system}, isbn = {0022-3654}, doi = {Doi 10.1021/J100026a020}, url = {://WOS:A1995RG56200020}, author = {Schmidt, C. and Rosen, M. E. and Caplan, D. F. and Pines, A. and Quinton, M. F.} } @article {439, title = {Spin-Polarized Xe-129 Gas Imaging of Materials}, journal = {Journal of Magnetic Resonance Series A}, volume = {115}, year = {1995}, note = {J Magn Reson Ser ARl474Times Cited:49Cited References Count:23}, month = {Jul}, pages = {127-130}, keywords = {xenon}, isbn = {1064-1858}, doi = {Doi 10.1006/Jmra.1995.1157}, url = {://WOS:A1995RL47400017}, author = {Song, Y. Q. and Gaede, H. C. and Pietrass, T. and Barrall, G. A. and Chingas, G. C. and Ayers, M. R. and Pines, 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.} } @article {445, title = {Xenon Nmr-Study of a Nematic Liquid-Crystal Confined to Cylindrical Submicron Cavities}, journal = {Journal of Physical Chemistry}, volume = {99}, year = {1995}, note = {J Phys Chem-UsRm901Times Cited:17Cited References Count:37}, month = {Aug 3}, pages = {11989-11993}, abstract = {

NMR studies of xenon gas dissolved in the liquid crystal ZLI 1132 confined to submicron cylindrical cavities are reported. Spectra taken as a function of temperature yield a clear indication of the nematic to isotropic phase transition of the confined liquid crystals. In the nematic phase at 21 degrees C, the resonance line of dissolved Xe-129 exhibits a chemical shift anisotropy of 15 ppm due to a random distribution of director axes in the plane perpendicular to the long axis of the cylinder. The anisotropy and temperature dependence of the confined system are compared to control experiments that use the bulk liquid crystal. The quadrupolar splitting observed in the Xe-131 NMR spectrum of the confined liquid crystalline solution of xenon gas is slightly greater than that found in the bulk. Two-dimensional exchange NMR demonstrates that the xenon atoms probe different average liquid crystal directors within a single cavity on a 20 ms time scale and that interpore exchange occurs on a time scale of 400 ms. The exchange data indicate that changes in the orientation of the director within individual cavities occur on a length scale of about 2 mu m.

}, keywords = {mixtures}, isbn = {0022-3654}, doi = {Doi 10.1021/J100031a029}, url = {://WOS:A1995RM90100029}, author = {Long, H. W. and Luzar, M. and Gaede, H. C. and Larsen, R. G. and Kritzenberger, J. and Pines, A. and Crawford, G. P.} } @article {464, title = {2-Dimensional Xe-129 Exchange Nmr Measurements of Xenon Dynamics in Na-a Zeolite}, journal = {Zeolites and Related Microporous Materials: State of the Art 1994}, volume = {84}, year = {1994}, note = {Stud Surf Sci CatalPart a-CBd02eTimes Cited:3Cited References Count:21Studies in Surface Science and Catalysis}, pages = {519-526}, abstract = {Two-dimensional (2D) exchange NMR is a powerful tool for measuring the dynamics and energetics of adsorbed xenon atoms undergoing slow exchange between the alpha-cages of Na-A zeolite. In this proceedings, we present recently published results, as well as additional discussion and data obtained, using 2D Xe-129 NMR to determine rate coefficients for intercage xenon hopping and to correlate them with adsorption and activation energies. Variable-temperature experiments establish the activation energy for hopping between alpha-cages to be 60+/-10 kJ/mol. The dependence of these kinetic and thermodynamic quantities on xenon occupancy of the alpha-cages reflects the importance of intracage interactions on the behavior of the adsorbed guest molecules.}, keywords = {cavities}, isbn = {0167-2991}, url = {://WOS:A1994BD02E00063}, author = {Janicke, M. and Chmelka, B. F. and Larsen, R. G. and Shore, J. and Schmidt-Rohr, K. and Emsley, L. and Long, H. and Pines, A.} } @article {461, title = {3-Dimensional Variable-Angle Nuclear-Magnetic-Resonance Exchange Spectroscopy without Rotor Axis Hopping}, journal = {Journal of Chemical Physics}, volume = {101}, year = {1994}, note = {J Chem PhysNy002Times Cited:12Cited References Count:48}, month = {Aug 1}, pages = {1852-1864}, abstract = {

Slow, large-amplitude chain motions play an important role in determining the macroscopic mechanical properties of polymers. Although such motions have been studied quantitatively by two-dimensional (2D) nuclear: magnetic resonance (NMR) exchange experiments, overlapping anisotropic patterns hamper spectral analysis, and limit applications. Variable angle correlation spectroscopy (VACSY) has proven useful in resolving such problems for rapidly spinning samples by separating anisotropic spectral patterns according to isotropic chemical shifts. In a previous study [J. Am. Chem. Sec. 115, 4825 (1993)], we described a three-dimensional (3D) NMR experiment that incorporates; the VACSY method and a hop of the rotor axis to correlate the isotropic chemical shifts to 2D anisotropic exchange patterns. The hop of the rotor axis, however, presents experimental difficulties and limits the range of motional rates that may be studied. We present in this paper a new 3D VACSY exchange experiment that obtains the same correlations without the need for the rotor axis hop. A series of 2D exchange spectra are recorded with the sample spinning at different rotation axis angles.\&$\#$39; Then using the scaling of the anisotropic frequency at the different angles, we construct the data onto a 3D matrix so that a Fourier transformation directly yields the desired correlations. The technique is applied to C-13 exchange NMR to study the slow molecular motion of ordered isotactic polypropylene.

}, keywords = {distributions}, isbn = {0021-9606}, doi = {Doi 10.1063/1.467696}, url = {://WOS:A1994NY00200011}, author = {Lee, Y. K. and Emsley, L. and Larsen, R. G. and Schmidt-Rohr, K. and Hong, M. and Frydman, L. and Chingas, G. C. and Pines, A.} } @article {476, title = {Nmr-Study of Xenon Dynamics and Energetics in Na-a Zeolite}, journal = {Chemical Physics Letters}, volume = {214}, year = {1993}, note = {Chem Phys LettMd614Times Cited:56Cited References Count:22}, month = {Oct 29}, pages = {220-226}, abstract = {

For xenon atoms adsorbed in Na-A zeolite, electronic interactions cause shifts in NMR frequencies, resulting in a spectrum with discrete peaks from xenon atoms in cages with different xenon occupancies. Using two-dimensional exchange NMR, it is possible to determine the microscopic rates of intercage motion and to relate them to the adsorption and activation energies of the xenon atoms. The dependence of the adsorption energies on xenon cage occupancy reflects the importance of the intercage interactions and is directly related to the cage occupancy distribution. Variable temperature measurements yield an activation energy of about 60 kJ/mol for the transfer of a xenon from one cage to another.

}, keywords = {xe}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(93)90085-F}, url = {://WOS:A1993MD61400015}, author = {Larsen, R. G. and Shore, J. and Schmidt-Rohr, K. and Emsley, L. and Long, H. and Pines, A. and Janicke, M. and Chmelka, B. F.} } @article {480, title = {Variable-Angle 3-Dimensional Exchange Nuclear-Magnetic-Resonance Spectroscopy for the Study of Molecular-Motion in Complex Solids}, journal = {Journal of the American Chemical Society}, volume = {115}, year = {1993}, note = {J Am Chem SocLf062Times Cited:14Cited References Count:23}, month = {Jun 2}, pages = {4825-4829}, abstract = {

Although molecular motions are responsible for many of the macroscopic properties observed in solids, especially in polymers, methods for studying these processes in all but the simplest systems are scarce. In the present study we introduce a three-dimensional nuclear magnetic resonance experiment for characterizing ultraslow molecular motions in complex solid systems. The technique extracts dynamic information by resolving the two-dimensional exchange distributions that can be observed in spectra of static samples, according to the isotropic chemical shifts of individual molecular sites. These three-dimensional correlations are achieved by processing signals arising from a fast-spinning solid sample using two independent macroscopic axes of rotation as extraction parameters, an approach which becomes practical due to the simple scaling behavior of anisotropic chemical shifts with respect to the axis of sample rotation. The principles involved in this new spectroscopic technique are discussed, and the method is illustrated with an application to the analysis of motions in isotactic polypropylene.

}, keywords = {jumps}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00064a050}, url = {://WOS:A1993LF06200050}, author = {Frydman, L. and Lee, Y. K. and Emsley, L. and Chingas, G. C. and Pines, A.} } @article {494, title = {Adsorption Effects in Aluminophosphate Molecular-Sieves Studied by Al-27 Double-Rotation Nmr}, journal = {Catalysis Letters}, volume = {15}, year = {1992}, note = {Catal LettJj259Times Cited:18Cited References Count:17}, pages = {65-73}, abstract = {

Al-27 double rotation NMR (DOR) spectroscopy is used to investigate structural changes in the framework of several aluminophosphate molecular sieves upon adsorption of water. The shapes, widths, and positions of the spectral lines yield information on the aluminum environments, adsorption sites, and degree of structural disorder undergone upon water adsorption.

}, keywords = {alpo4-8}, isbn = {1011-372X}, doi = {Doi 10.1007/Bf00770899}, url = {://WOS:A1992JJ25900008}, author = {Jelinek, R. and Chmelka, B. F. and Wu, Y. and Davis, M. E. and Ulan, J. G. and Gronsky, R. and Pines, A.} } @article {496, title = {Correlation of Isotropic and Anisotropic Chemical-Shifts in Solids by 2-Dimensional Variable-Angle-Spinning Nmr}, journal = {Israel Journal of Chemistry}, volume = {32}, year = {1992}, note = {Israel J ChemKt517Times Cited:29Cited References Count:19}, pages = {161-164}, abstract = {

We describe a new solid-state nuclear magnetic resonance (NMR) technique for correlating anisotropic and isotropic chemical shifts in powdered samples. Two-dimensional (2D) NMR spectra are obtained by processing signals acquired in independent experiments for different angles between the sample spinning axis and the Zeeman magnetic field. This 2D NMR approach can therefore resolve individual static anisotropic lineshapes according to their isotropic chemical shift frequencies, without use of sudden mechanical motions or multiple-pulse irradiation schemes. Applications of the technique are illustrated with an analysis of the chemical shift anisotropy for the eight distinct C-13 sites in tyrosine.

}, keywords = {magic-angle}, isbn = {0021-2148}, url = {://WOS:A1992KT51700005}, author = {Frydman, L. and Chingas, G. C. and Lee, Y. K. and Grandinetti, P. J. and Eastman, M. A. and Barrall, G. A. and Pines, A.} } @article {491, title = {Multiple-Quantum Nmr-Study of the Distribution of Benzene in Nay Zeolite}, journal = {Journal of Physical Chemistry}, volume = {96}, year = {1992}, note = {J Phys Chem-UsJu555Times Cited:26Cited References Count:24}, month = {Oct 15}, pages = {8517-8522}, abstract = {

We have used multiple-quantum NMR to measure the apparent spin network size as a function of excitation time of NaY zeolite samples containing varying amounts of benzene. Behavior observed at low concentrations of benzene was consistent with the presence of isolated clusters of benzene molecules in the supercages, with a statistical distribution of benzene molecules between supercages. Behavior observed at high concentrations of benzene was consistent with the presence of weakly coupled clusters of benzene molecules, with a uniform distribution of benzene molecules between supercages.

}, keywords = {solids}, isbn = {0022-3654}, doi = {Doi 10.1021/J100200a057}, url = {://WOS:A1992JU55500057}, author = {Pearson, J. G. and Chmelka, B. F. and Shykind, D. N. and Pines, A.} } @article {487, title = {Nmr-Studies of the Surface-Structure and Dynamics of Semiconductor Nanocrystals}, journal = {Chemical Physics Letters}, volume = {198}, year = {1992}, note = {Chem Phys LettJt385Times Cited:77Cited References Count:27}, month = {Oct 16}, pages = {431-436}, abstract = {

H-1 NMR studies of thiophenol capping groups on cadmium sulfide nanocrystals demonstrate that the coverage of the capping molecule depends on the size of the nanocrystal. Data are presented which show that as the size of the nanocrystal increases, the coverage of thiophenol decreases. In addition, information about the overall tumbling of the nanocrystal and the motion of the capping groups relative to the surface can be obtained from linewidth studies, indicating that the rotation of the capping groups is hindered in the smaller nanocrystals (r almost-equal-to 12 angstrom) and becomes less so in larger nanocrystals (r almost-equal-to 20 angstrom). The coverage data are related to the electronic properties of this important class of compounds.

}, keywords = {relaxation}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(92)80023-5}, url = {://WOS:A1992JT38500001}, author = {Sachleben, J. R. and Wooten, E. W. and Emsley, L. and Pines, A. and Colvin, V. L. and Alivisatos, A. P.} } @article {495, title = {Pulsed Fourier-Transform Nqr of N-14 with a Dc Squid}, journal = {Physical Review Letters}, volume = {69}, year = {1992}, note = {Phys Rev LettJe754Times Cited:23Cited References Count:27}, month = {Jul 27}, pages = {684-687}, abstract = {

The zero-field free induction decay of solid ammonium perchlorate at 1.5 K has been directly detected with a dc superconducting quantum interference device. The Fourier-transform spectrum consists of three sharp lines at 17.4, 38.8, and 56.2 kHz arising from pure N-14 nucLear quadrupole resonance transitions. The absence of splittings and resonance transitions from dipolar-coupled proton spins is attributed to reorientation of the ammonium groups by quantum tunneling in combination with motional averaging in the three proton levels characterized by the irreducible representation T. The measured N-14 spin-spin relaxation time is 22+/-2 ms and the spin-lattice relaxation time is 63+/-6 ms.

}, keywords = {nh4clo4}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.69.684}, url = {://WOS:A1992JE75400034}, author = {Hurlimann, M. D. and Pennington, C. H. and Fan, N. Q. and Clarke, J. and Pines, A. and Hahn, E. L.} } @article {500, title = {Rb-87 Dynamic-Angle Spinning Nmr-Spectroscopy of Inorganic Rubidium Salts}, journal = {Journal of the American Chemical Society}, volume = {114}, year = {1992}, note = {J Am Chem SocJm979Times Cited:39Cited References Count:28}, month = {Sep 9}, pages = {7489-7493}, abstract = {

Five inorganic rubidium salts, RbCl, RbClO4, Rb2SO4, Rb2CrO4, and RbNO3, were examined using Rb-87 NMR spectroscopy. Significant line narrowing occurs under dynamic-angle spinning (DAS) compared to magic-angle spinning (MAS) or variable-angle spinning (VAS). From DAS spectra acquired at various magnetic field strengths, isotropic chemical shifts and isotropic second-order quadrupolar shifts were obtained. By simulations of single-site line shapes obtained from MAS-detected DAS experiments, complete chemical shift and quadrupolar parameters were determined for each of the three crystallographically distinct rubidium sites in RbNO3.

}, keywords = {cesium}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00045a023}, url = {://WOS:A1992JM97900023}, author = {Baltisberger, J. H. and Gann, S. L. and Wooten, E. W. and Chang, T. H. and Mueller, K. T. and Pines, A.} } @article {497, title = {Variable-Angle Correlation Spectroscopy in Solid-State Nuclear-Magnetic-Resonance}, journal = {Journal of Chemical Physics}, volume = {97}, year = {1992}, note = {J Chem PhysJr338Times Cited:90Cited References Count:28}, month = {Oct 1}, pages = {4800-4808}, abstract = {

We describe here a new solid-state nuclear-magnetic-resonance (NMR) experiment for correlating anisotropic and isotropic chemical shifts of inequivalent nuclei in powdered samples. Spectra are obtained by processing signals arising from a spinning sample, acquired in independent experiments as a function of the angle between the axis of macroscopic rotation and the external magnetic field. This is in contrast to previously proposed techniques, which were based on sudden mechanical flippings or multiple-pulse sequences. We show that the time evolution of variable-angle-spinning signals is determined by a distribution relating the isotropic frequencies of the spins with their corresponding chemical shift anisotropies. Fourier transformation of these data therefore affords a two-dimensional NMR spectrum, in which line shapes of isotropic and anisotropic interactions are correlated. Theoretical and experimental considerations involved in the extraction of this spectral information are discussed, and the technique is illustrated by an analysis of C-13 NMR anisotropy in glycine, cysteine, and p-anisic acid.

}, keywords = {axis}, isbn = {0021-9606}, doi = {Doi 10.1063/1.463860}, url = {://WOS:A1992JR33800022}, author = {Frydman, L. and Chingas, G. C. and Lee, Y. K. and Grandinetti, P. J. and Eastman, M. A. and Barrall, G. A. and Pines, A.} } @conference {509, title = {Framework ordering in aluminophosphate molecular sieves studied by (27)Al double rotation NMR}, volume = {69}, year = {1991}, month = {1991}, pages = {435-442}, publisher = {Elsevier}, organization = {Elsevier}, author = {Chmelka, B.F. and Wu, Y. and Jelinek, R. and Davis, M.E. and Pines, A.}, editor = {P.A. Jacobs, N.I. Jaeger, L. Kubelkova, and B. Wichterlov} } @article {504, title = {High-Resolution O-17 Nmr of Solid Silicates}, journal = {Journal of the American Chemical Society}, volume = {113}, year = {1991}, note = {J Am Chem SocEr082Times Cited:90Cited References Count:39}, month = {Jan 2}, pages = {32-38}, abstract = {

Several O-17-enriched silicates were studied by use of dynamic angle spinning (DAS) and double rotation (DOR) nuclear magnetic resonance spectroscopy. These methods average away second-order quadrupolar interactions by reorienting a sample about a time-dependent axis, thereby yielding high-resolution spectra of oxygen-17 nuclei. A narrow spectral line is observed for each distinct oxygen site at the sum of the isotropic chemical shift and the field-dependent isotropic second-order quadrupolar shift. Resolution is increased by up to 2 orders of magnitude compared to conventional magic angle spinning (MAS) spectra. Crystallographically inequivalent oxygens are now observable as distinct resonances in spectra of polycrystalline silicates such as diopside (CaMgSi2(17)O6), wollastonite (CaSi17O3), clinoenstatite (MgSi17O3), larnite (Ca2Si17O4),and forsterite (Mg2Si17O4).

}, keywords = {spectra}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00001a006}, url = {://WOS:A1991ER08200006}, author = {Mueller, K. T. and Wu, Y. and Chmelka, B. F. and Stebbins, J. and Pines, A.} } @article {510, title = {Measurement of Xenon Distribution Statistics in Na-a Zeolite Cavities}, journal = {Physical Review Letters}, volume = {66}, year = {1991}, note = {Phys Rev LettEv897Times Cited:78Cited References Count:21}, month = {Feb 4}, pages = {580-583}, abstract = {

Xe-129 NMR spectroscopy has been used to probe directly the distribution of xenon atoms confined in atomic-size Na-A zeolite cavities. For mean xenon occupancies less than about three Xe atoms per a-cage, the guest populations are well described by binomial statistics. At higher guest loadings the finite volumes of the xenon atoms become significant, as reflected by a fit of the experimental populations with a hypergeometric distribution, with a maximum of seven Xe atoms per cage. At the highest xenon loadings the experimental distribution is narrower than hypergeometric, as predicted by Monte Carlo simulations.

}, keywords = {fluids}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.66.580}, url = {://WOS:A1991EV89700016}, author = {Chmelka, B. F. and Raftery, D. and Mccormick, A. V. and Demenorval, L. C. and Levine, R. D. and Pines, A.} } @article {506, title = {Nmr Probe for Dynamic-Angle Spinning}, journal = {Review of Scientific Instruments}, volume = {62}, year = {1991}, note = {Rev Sci InstrumFp312Times Cited:31Cited References Count:35}, month = {Jun}, pages = {1445-1452}, abstract = {

We describe the design of a probe for dynamic-angle spinning (DAS) NMR experiments, comprised of a spinning cylindrical sample holder whose axis may be reoriented rapidly between discrete directions within the bore of a superconducting magnet. This allows the refocusing of nuclear spin magnetization that evolves under anisotropic interactions such as chemical shift anisotropy and quadrupolar coupling, providing high resolution NMR spectra for quadrupolar nuclei in solid materials. The probe includes an axial air delivery system to bearing and drive jets which support and spin a rotor containing the sample. Axis reorientation is accomplished with a pulley attached to the probehead and coupled to a stepping motor outside of the magnet. The choice of motor and gear ratio is based on an analysis of the moments of inertia of the motor and load, the desired angular resolution, and simplicity of design. Control of angular accuracy and precision are discussed, as well as the efficiency of radiofrequency irradiation and detection. High resolution DAS spectra of oxygen-17 and aluminum-27 nuclei in polycrystalline minerals illustrate the experimental capabilities.

}, keywords = {minerals}, isbn = {0034-6748}, doi = {Doi 10.1063/1.1142465}, url = {://WOS:A1991FP31200011}, author = {Mueller, K. T. and Chingas, G. C. and Pines, A.} } @article {511, title = {Nmr-Study of the Distribution of Aromatic-Molecules in Nay Zeolite}, journal = {Journal of Physical Chemistry}, volume = {95}, year = {1991}, note = {J Phys Chem-UsEr473Times Cited:70Cited References Count:64}, month = {Jan 10}, pages = {303-310}, abstract = {

Local and macroscopic distributions of adsorbed benzene, 1,3,5-trimethylbenzene, and hexamethylbenzene (HMB) molecules among the intracrystalline of NaY zeolite samples have been investigated by Xe-129 and multiple-quantum NMR. Xenon-129 NMR, a sensitive probe of macroscopic distributions of molecules in zeolites at room temperature, demonstrates the importance of sample heat treatment in distributing an adsorbate homogeneously throughout a collection of zeolite particles. NaY samples containing organic guests adsorbed a temperatures near the bulk species\&$\#$39; melting point produce multiple or broad xenon lines characteristic of macroscopic (i.e., interparticle) adsorbate concentration gradients. After thorough heat treatment of the samples at elevated temperatures, the xenon spectrum collapses to a single sharp line, consistent with a macroscopically uniform distribution. For HMB adsorbed in NaY, \"counting\" hydrogen clusters by multiple-quantum NMR reveals intraparticle HMB distributions consistent with one molecular per cavity at low loadings (average bulk loading less-than-or-equal-to 1 molecule per cavity) and two molecules per cavity at higher loadings.

}, keywords = {catalysts}, isbn = {0022-3654}, doi = {Doi 10.1021/J100154a056}, url = {://WOS:A1991ER47300056}, author = {Chmelka, B. F. and Pearson, J. G. and Liu, S. B. and Ryoo, R. and Demenorval, L. C. and Pines, A.} } @article {508, title = {Study of the Aluminophosphates Alpo4-21 and Alpo4-25 by Al-27 Double-Rotation Nmr}, journal = {Journal of the American Chemical Society}, volume = {113}, year = {1991}, note = {J Am Chem SocFn005Times Cited:53Cited References Count:16}, month = {May 22}, pages = {4097-4101}, abstract = {

Aluminum-27 double-rotation NMR in a magnetic field of 11.7 T distinguishes the extremely distorted five-coordinated aluminum sites in the molecular sieve precursor ALPO4(-21). Upon calcination, ALPO4(-21) transforms to ALPO4(-25), which has two tetrahedral aluminum sites with similar isotropic chemical shifts that cannot be resolved in an 11.7 T field. The two tetrahedral environments, however, have a different quadrupole coupling constants and are distinguished by double rotation at 4.2 T field. The quadrupole coupling constants obtained for these sites indicates that the tetrahedral aluminum environments are less distorted in the hydrated material.

}, keywords = {nuclei}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00011a007}, url = {://WOS:A1991FN00500007}, author = {Jelinek, R. and Chmelka, B. F. and Wu, Y. and Grandinetti, P. J. and Pines, A. and Barrie, P. J. and Klinowski, J.} } @article {524, title = {Aluminum and Boron Nuclear-Quadrupole Resonance with a Direct-Current Superconducting Quantum Interference Device}, journal = {Journal of Chemical Physics}, volume = {93}, year = {1990}, note = {J Chem PhysEl294Times Cited:12Cited References Count:49}, month = {Dec 1}, pages = {7639-7646}, isbn = {0021-9606}, doi = {Doi 10.1063/1.459395}, url = {://WOS:A1990EL29400010}, author = {Connor, C. and Chang, J. and Pines, A.} } @article {521, title = {Dynamic-Angle Spinning of Quadrupolar Nuclei}, journal = {Journal of Magnetic Resonance}, volume = {86}, year = {1990}, note = {J Magn ResonCu525Times Cited:288Cited References Count:32}, month = {Feb 15}, pages = {470-487}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(90)90025-5}, url = {://WOS:A1990CU52500003}, author = {Mueller, K. T. and Sun, B. Q. and Chingas, G. C. and Zwanziger, J. W. and Terao, T. and Pines, A.} } @article {517, title = {A Fast, Stable Quadrature Phase Generator for Multiple-Pulse Nmr}, journal = {Review of Scientific Instruments}, volume = {61}, year = {1990}, note = {Rev Sci InstrumDc425Times Cited:8Cited References Count:14}, month = {May}, pages = {1474-1479}, isbn = {0034-6748}, doi = {Doi 10.1063/1.1141155}, url = {://WOS:A1990DC42500016}, author = {Shykind, D. N. and Chingas, G. C. and Pines, A. and Shaka, A. J.} } @article {515, title = {High-Resolution Al-27 Nmr-Spectroscopy of the Aluminophosphate Molecular-Sieve Vpi-5}, journal = {Nature}, volume = {346}, year = {1990}, note = {NatureDt679Times Cited:97Cited References Count:12}, month = {Aug 9}, pages = {550-552}, isbn = {0028-0836}, doi = {Doi 10.1038/346550a0}, url = {://WOS:A1990DT67900067}, author = {Wu, Y. and Chmelka, B. F. and Pines, A. and Davis, M. E. and Grobet, P. J. and Jacobs, P. A.} } @article {525, title = {Magnetic-Resonance Spectrometer with a Dc Squid Detector}, journal = {Review of Scientific Instruments}, volume = {61}, year = {1990}, note = {Rev Sci InstrumCu216Times Cited:30Cited References Count:19}, month = {Mar}, pages = {1059-1063}, isbn = {0034-6748}, doi = {Doi 10.1063/1.1141476}, url = {://WOS:A1990CU21600021}, author = {Connor, C. and Chang, J. and Pines, A.} } @inbook {555, title = {Calcination-dependence ofplatinum cluster formation in NaY zeolite: A xenon-129 NMR study}, booktitle = {Structure and Reactivity of Surfaces}, year = {1989}, pages = {269-278}, publisher = {Elsevier Science Publishers}, organization = {Elsevier Science Publishers}, address = {Amsterdam}, author = {Chmelka, B.F. and de Menorval, L.C. and Csencsits, R. and Ryoo, R. and Liu, S.B. and Radke, C.J. and Petersen, E.E. and Pines, A.}, editor = {C. Morterra, A. Zecchina, and G. Costa} } @article {556, title = {Direct Detection of Al-27 Resonance with a Squid Spectrometer}, journal = {Journal of Magnetic Resonance}, volume = {82}, year = {1989}, note = {J Magn ResonU1146Times Cited:16Cited References Count:13}, month = {Apr}, pages = {387-391}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(89)90044-9}, url = {://WOS:A1989U114600019}, author = {Chang, J. and Connor, C. and Hahn, E. L. and Huber, H. and Pines, A.} } @article {552, title = {Frequency Selective Nmr Pulse Sequences Generated by Iterative Schemes with Multiple Fixed-Points}, journal = {Molecular Physics}, volume = {67}, year = {1989}, note = {Mol PhysAf151Times Cited:3Cited References Count:24}, month = {Jun 20}, pages = {505-516}, isbn = {0026-8976}, doi = {Doi 10.1080/00268978900101251}, url = {://WOS:A1989AF15100003}, author = {Cho, H. and Mueller, K. T. and Shaka, A. J. and Pines, A.} } @article {551, title = {Nuclear Magnetic-Resonance with Dc Squid Preamplifiers}, journal = {Ieee Transactions on Magnetics}, volume = {25}, year = {1989}, note = {Ieee T MagnT6706Times Cited:21Cited References Count:23}, month = {Mar}, pages = {1193-1199}, isbn = {0018-9464}, doi = {Doi 10.1109/20.92510}, url = {://WOS:A1989T670600113}, author = {Fan, N. Q. and Heaney, M. B. and Clarke, J. and Newitt, D. and Wald, L. L. and Hahn, E. L. and Bielecki, A. and Pines, A.} } @article {554, title = {O-17 Nmr in Solids by Dynamic-Angle Spinning and Double Rotation}, journal = {Nature}, volume = {339}, year = {1989}, note = {NatureU4451Times Cited:177Cited References Count:15}, month = {May 4}, pages = {42-43}, isbn = {0028-0836}, doi = {Doi 10.1038/339042a0}, url = {://WOS:A1989U445100054}, author = {Chmelka, B. F. and Mueller, K. T. and Pines, A. and Stebbins, J. and Wu, Y. and Zwanziger, J. W.} } @article {553, title = {Some Developments in Nuclear Magnetic-Resonance of Solids}, journal = {Science}, volume = {246}, year = {1989}, note = {ScienceAt607Times Cited:33Cited References Count:91}, month = {Oct 6}, pages = {71-77}, isbn = {0036-8075}, doi = {Doi 10.1126/Science.246.4926.71}, url = {://WOS:A1989AT60700032}, author = {Chmelka, B. F. and Pines, A.} } @article {562, title = {Multiple-Pulse Sequences for Precise Transmitter Phase Alignment}, journal = {Journal of Magnetic Resonance}, volume = {80}, year = {1988}, note = {J Magn ResonQ6187Times Cited:10Cited References Count:33}, month = {Oct 15}, pages = {96-111}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(88)90060-1}, url = {://WOS:A1988Q618700008}, author = {Shaka, A. J. and Shykind, D. N. and Chingas, G. C. and Pines, A.} } @article {569, title = {Probing Metal Cluster Formation in Nay Zeolite by Xe-129 Nmr}, journal = {Journal of the American Chemical Society}, volume = {110}, year = {1988}, note = {J Am Chem SocP0739Times Cited:33Cited References Count:18}, month = {Jun 22}, pages = {4465-4467}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00221a086}, url = {://WOS:A1988P073900086}, author = {Chmelka, B. F. and Ryoo, R. and Liu, S. B. and Demenorval, L. C. and Radke, C. J. and Petersen, E. E. and Pines, A.} } @article {567, title = {A Si-29 Nuclear Magnetic-Resonance Study of Silicon-Aluminum Ordering in Leucite and Analcite}, journal = {Physics and Chemistry of Minerals}, volume = {15}, year = {1988}, note = {Phys Chem MinerM6832Times Cited:44Cited References Count:39}, pages = {370-382}, isbn = {0342-1791}, doi = {Doi 10.1007/Bf00311042}, url = {://WOS:A1988M683200009}, author = {Murdoch, J. B. and Stebbins, J. F. and Carmichael, I. S. E. and Pines, A.} } @article {579, title = {Berry Phase in Magnetic-Resonance}, journal = {Molecular Physics}, volume = {61}, year = {1987}, note = {Mol PhysK2154Times Cited:90Cited References Count:47}, month = {Aug 20}, pages = {1327-1340}, isbn = {0026-8976}, doi = {Doi 10.1080/00268978700101831}, url = {://WOS:A1987K215400001}, author = {Suter, D. and Chingas, G. C. and Harris, R. A. and Pines, A.} } @article {583, title = {Distribution of Hexamethylbenzene in a Zeolite Studied by Xe-129 and Multiple-Quantum Nmr}, journal = {Journal of Physical Chemistry}, volume = {91}, year = {1987}, note = {J Phys Chem-UsL6632Times Cited:63Cited References Count:16}, month = {Dec 31}, pages = {6575-6577}, isbn = {0022-3654}, doi = {Doi 10.1021/J100311a003}, url = {://WOS:A1987L663200003}, author = {Ryoo, R. and Liu, S. B. and Demenorval, L. C. and Takegoshi, K. and Chmelka, B. and Trecoske, M. and Pines, A.} } @article {594, title = {Iterative Maps for Broad-Band Excitation of Transverse Coherence in 2 Level Systems}, journal = {Journal of Chemical Physics}, volume = {86}, year = {1987}, note = {J Chem PhysH7665Times Cited:6Cited References Count:38}, month = {Jun 15}, pages = {6591-6601}, isbn = {0021-9606}, doi = {Doi 10.1063/1.452405}, url = {://WOS:A1987H766500003}, author = {Cho, H. and Pines, A.} } @article {595, title = {Iterative Maps with Multiple Fixed-Points for Excitation of 2 Level Systems}, journal = {Journal of Chemical Physics}, volume = {86}, year = {1987}, note = {J Chem PhysG4424Times Cited:12Cited References Count:68}, month = {Mar 15}, pages = {3089-3106}, isbn = {0021-9606}, doi = {Doi 10.1063/1.452020}, url = {://WOS:A1987G442400004}, author = {Cho, H. and Baum, J. and Pines, A.} } @article {603, title = {Defects and Short-Range Order in Nepheline Group Minerals - a Si-29 Nuclear-Magnetic-Resonance Study}, journal = {Physics and Chemistry of Minerals}, volume = {13}, year = {1986}, note = {Phys Chem MinerE6311Times Cited:40Cited References Count:61}, pages = {371-381}, isbn = {0342-1791}, url = {://WOS:A1986E631100003}, author = {Stebbins, J. F. and Murdoch, J. B. and Carmichael, I. S. E. and Pines, A.} } @article {611, title = {Iterative Maps for Bistable Excitation of 2-Level Systems}, journal = {Physical Review Letters}, volume = {56}, year = {1986}, note = {Phys Rev LettC1114Times Cited:23Cited References Count:21}, month = {May 5}, pages = {1905-1908}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.56.1905}, url = {://WOS:A1986C111400006}, author = {Cho, H. M. and Tycko, R. and Pines, A. and Guckenheimer, J.} } @article {602, title = {New Probe for High-Temperature Nmr-Spectroscopy with Ppm Resolution}, journal = {Review of Scientific Instruments}, volume = {57}, year = {1986}, note = {Rev Sci InstrumAxa20Times Cited:15Cited References Count:19}, month = {Jan}, pages = {39-42}, isbn = {0034-6748}, doi = {Doi 10.1063/1.1139115}, url = {://WOS:A1986AXA2000010}, author = {Stebbins, J. F. and Schneider, E. and Murdoch, J. B. and Pines, A. and Carmichael, I. S. E.} } @article {619, title = {Composite Pulses without Phase-Distortion}, journal = {Journal of Magnetic Resonance}, volume = {61}, year = {1985}, note = {J Magn ResonAbv11Times Cited:124Cited References Count:37}, pages = {90-101}, isbn = {1090-7807}, doi = {Doi 10.1016/0022-2364(85)90270-7}, url = {://WOS:A1985ABV1100009}, author = {Tycko, R. and Cho, H. M. and Schneider, E. and Pines, A.} } @article {620, title = {A High-Temperature High-Resolution Nmr-Study of Na-23, Al-27 and Si-29 in Molten Silicates}, journal = {Nature}, volume = {314}, year = {1985}, note = {NatureAdt99Times Cited:58Cited References Count:13}, pages = {250-252}, isbn = {0028-0836}, doi = {Doi 10.1038/314250a0}, url = {://WOS:A1985ADT9900039}, author = {Stebbins, J. F. and Murdoch, J. B. and Schneider, E. and Carmichael, I. S. E. and Pines, A.} } @article {691, title = {C-13 Chemical Shielding Tensors in Ammonium Hydrogen Malonate}, journal = {Journal of Chemical Physics}, volume = {62}, year = {1975}, note = {J Chem PhysAf060Times Cited:23Cited References Count:14}, pages = {4923-4926}, isbn = {0021-9606}, doi = {Doi 10.1063/1.430406}, url = {://WOS:A1975AF06000046}, author = {Chang, J. J. and Griffin, R. G. and Pines, A.} } @article {690, title = {Qualitative Analysis of Chemisorbed Molecular Species Via C-13 Nmr}, journal = {Surface Science}, volume = {47}, year = {1975}, note = {Surf SciV7219Times Cited:36Cited References Count:22}, pages = {661-665}, isbn = {0039-6028}, doi = {Doi 10.1016/0039-6028(75)90211-3}, url = {://WOS:A1975V721900023}, author = {Chang, J. J. and Pines, A. and Fripiat, J. J. and Resing, H. A.} } @article {697, title = {C-13 Nuclear Magnetic-Resonance in Solid Ammonium-Tartrate}, journal = {Journal of Chemical Physics}, volume = {61}, year = {1974}, note = {J Chem PhysT7994Times Cited:76Cited References Count:35}, pages = {1021-1030}, isbn = {0021-9606}, doi = {Doi 10.1063/1.1681970}, url = {://WOS:A1974T799400040}, author = {Pines, A. and Chang, J. J. and Griffin, R. G.} } @article {705, title = {Chemical Shielding Tensor of C-13 in a Carboxyl Group}, journal = {Journal of Chemical Physics}, volume = {60}, year = {1974}, note = {J Chem PhysS6878Times Cited:22Cited References Count:10}, pages = {2561-2562}, isbn = {0021-9606}, doi = {Doi 10.1063/1.1681401}, url = {://WOS:A1974S687800054}, author = {Chang, J. J. and Griffin, R. G. and Pines, A.} } @article {698, title = {Effect of Phase-Transitions on C-13 Nuclear Magnetic-Resonance Spectra in Para-Azoxydianisole, a Nematic Liquid-Crystal}, journal = {Journal of the American Chemical Society}, volume = {96}, year = {1974}, note = {J Am Chem SocT8383Times Cited:28Cited References Count:14}, pages = {5590-5591}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00824a057}, url = {://WOS:A1974T838300057}, author = {Pines, A. and Chang, J. J.} } @article {696, title = {High-Resolution C-13 Nmr in Solid Ammonium-Tartrate}, journal = {Bulletin of the American Physical Society}, volume = {19}, year = {1974}, note = {B Am Phys SocS1647Times Cited:0Cited References Count:0}, pages = {349-349}, isbn = {0003-0503}, url = {://WOS:A1974S164701005}, author = {Pines, A. and Chang, J. J. and Griffin, R. G.} } @article {699, title = {Study of Isotropic-Nematic-Solid Transitions in a Liquid-Crystal by Carbon-13-Proton Double-Resonance}, journal = {Physical Review A}, volume = {10}, year = {1974}, note = {Phys Rev AU0398Times Cited:73Cited References Count:18}, pages = {946-949}, isbn = {1050-2947}, doi = {Doi 10.1103/Physreva.10.946}, url = {://WOS:A1974U039800024}, author = {Pines, A. and Chang, J. J.} }