@article {3194, title = {SABRE: Chemical kinetics and spin dynamics of the formation of hyperpolarization}, journal = {Progress in Nuclear Magnetic Resonance Spectroscopy}, year = {2019}, month = {05/2019}, doi = {10.1016/j.pnmrs.2019.05.005}, url = {https://www.sciencedirect.com/science/article/pii/S007965651930024X}, author = {Danila Barskiy and Stephan Knecht and Alexandra Yurkovskaya and Konstantin Ivanov} } @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 {3195, title = {Selective Single-Site Pd-In Hydrogenation Catalyst for Production of Enhanced Magnetic Resonance Signals using Parahydrogen}, journal = {Chemistry - A European Journal}, volume = {24}, year = {2018}, month = {01/2018}, chapter = {2547}, abstract = {

Pd\−In/Al2O3\ single-site catalyst was able to show high selectivity (up to 98\ \%) in the gas phase semihydrogenation of propyne. Formation of intermetallic Pd\−In compound was studied by XPS during reduction of the catalyst. FTIR\−CO spectroscopy confirmed single-site nature of the intermetallic Pd\−In phase reduced at high temperature. Utilization of Pd\−In/Al2O3\ in semihydrogenation of propyne with parahydrogen allowed to produce \≈3400-fold NMR signal enhancement for reaction product propene (polarization=9.3\ \%), demonstrating the large contribution of pairwise hydrogen addition route. Significant signal enhancement as well as the high catalytic activity of the Pd\−In catalyst allowed to acquire\ 1H MR images of flowing hyperpolarized propene gas selectively for protons in CH, CH2\ and CH3\ groups. This observation is unique and can be easily transferred to the development of a useful MRI technique for an in situ investigation of selective semihydrogenation in catalytic reactors.

}, doi = {10.1002/chem.201705644}, url = {https://onlinelibrary.wiley.com/doi/full/10.1002/chem.201705644}, author = {Dudari Burueva and Kirill Kovtunov and Andrey Bukhtiyarov and Danila Barskiy and Igor Prosvirin and Igor Mashkovsky and Galina Baeva and Valerii Bukhtiyarov and Aleksandr Stakheev and Igor Koptyug} } @article {1074, title = {Sensitive magnetic control of ensemble nuclear spin hyperpolarization in diamond}, journal = {Nature Communications}, volume = {4}, year = {2013}, note = {Nature communicationsWang, Hai-JingShin, Chang SAvalos, Claudia ESeltzer, Scott JBudker, DmitryPines, AlexanderBajaj, Vikram SengEngland2013/06/06 06:00Nat Commun. 2013 Jun 5;4:1940. doi: 10.1038/ncomms2930.}, month = {June 5, 2013}, pages = {1940}, chapter = {1940}, abstract = {

Dynamic nuclear polarization, which transfers the spin polarization of electrons to nuclei, is routinely applied to enhance the sensitivity of nuclear magnetic resonance. This method is particularly useful when spin hyperpolarization can be produced and controlled optically or electrically. Here we show complete polarization of nuclei located near optically polarized nitrogen-vacancy centres in diamond. Close to the ground-state level anti-crossing condition of the nitrogen-vacancy electron spins, (13)C nuclei in the first shell are polarized in a pattern that depends sensitively upon the magnetic field. Based on the anisotropy of the hyperfine coupling and of the optical polarization mechanism, we predict and observe a reversal of the nuclear spin polarization with only a few millitesla change in the magnetic field. This method of magnetic control of high nuclear polarization at room temperature can be applied in sensitivity enhanced nuclear magnetic resonance of bulk nuclei, nuclear-based spintronics, and quantum computation in diamond.

}, isbn = {2041-1723 (Linking)}, doi = {10.1038/ncomms2930}, url = {http://www.ncbi.nlm.nih.gov/pubmed/23736952}, author = {Wang, H. J. and Shin, C. S. and Avalos, C. E. and Seltzer, S. J. and Budker, D. and Pines, A. and Bajaj, V. S.} } @article {1318, title = {Suppression of electron spin decoherence of the diamond NV center by a transverse magnetic field}, journal = {Physical Review B}, volume = {88}, year = {2013}, month = {10/2013}, abstract = {

We demonstrate that the spin decoherence of nitrogen vacancy (NV) centers in diamond can be suppressed by a transverse magnetic field if the electron spin bath is the primary decoherence source. The NV spin coherence, created in \“a decoherence-free subspace,\” is protected by the transverse component of the zero-field splitting, increasing the spin-coherence time about twofold. The decoherence due to the electron spin bath is also suppressed at magnetic fields stronger than \∼25 G when applied parallel to the NV symmetry axis. Our method can be used to extend the spin-coherence time of similar spin systems for applications in quantum computing, field sensing, and other metrologies.

}, doi = {10.1103/PhysRevB.88.161412}, url = {http://prb.aps.org/abstract/PRB/v88/i16/e161412}, author = {Shin, Chang S. and Avalos, Claudia E. and Butler, Mark C. and Wang, Hai-Jing and Seltzer, Scott J. and Liu, Ren-Bao and Pines, Alexander and Bajaj, Vikram S.} } @article {270, title = {Shimmed matching pulses: Simultaneous control of rf and static gradients for inhomogeneity correction}, journal = {Journal of Chemical Physics}, volume = {131}, year = {2009}, note = {J Chem Phys536HUTimes Cited:4Cited References Count:30}, month = {Dec 21}, abstract = {

Portable NMR systems generally suffer from poor field homogeneity and are therefore used more commonly for imaging and relaxation measurements rather than for spectroscopy. In recent years, various approaches have been proposed to increase the sample volume that is usable for spectroscopy. These include approaches based on manual shimming and those based on clever combinations of modulated radio frequency and gradient fields. However, this volume remains small and, therefore, of limited utility. We present improved pulses designed to correct for inhomogeneous dispersion across wide ranges of frequency offsets without eliminating chemical shift or spatial encoding. This method, based on the adiabatic double passage, combines the relatively larger corrections available from spatially matched rf gradients [C. Meriles , J. Magn. Reson. 164, 177 (2003)]. with the adjustable corrections available from time-modulated static field gradients [D. Topgaard , Proc. Natl. Acad. Sci. U.S.A. 101, 17576 (2004)]. We explain the origins of these corrections with a theoretical model that simplifies and expedites the design of the pulse waveforms. We also present a generalized method for evaluating and comparing pulses designed for inhomogeneity correction. Experiments validate this method and support simulations that offer new possibilities for significantly enhanced performance in portable environments.

}, keywords = {design}, isbn = {0021-9606}, doi = {Doi 10.1063/1.3243850}, url = {://WOS:000273036300030}, author = {Franck, J. M. and Demas, V. and Martin, R. W. and Bouchard, L. S. and Pines, A.} } @article {280, title = {Spectrally resolved flow imaging of fluids inside a microfluidic chip with ultrahigh time resolution}, journal = {Journal of Magnetic Resonance}, volume = {193}, year = {2008}, note = {J Magn Reson336INTimes Cited:14Cited References Count:19}, month = {Aug}, pages = {199-206}, abstract = {

Microfluidics has advanced to become a complete lab-on-a-chip platform with applications across Many disciplines of scientific research. While optical techniques are primarily used as modes of detection, magnetic resonance (MR) is emerging as a potentially powerful and complementary tool because of its non-invasive operation and analytical fidelity. Two prevailing limitations Currently inhibit MR techniques on microfluidic devices: poor sensitivity and the relatively slow time scale of dynamics that can be probed. it is commonly assumed that the time scale of observation of one variable limits the certainty with which one can measure the complementary variable. For example, short observation times imply poor spectral resolution. In this article, we demonstrate a new methodology that overcomes this fundamental limit, allowing in principle for arbitrarily high temporal resolution with a sensitivity across the entire microfluidic device several Orders of magnitude greater than is possible by direct MR measurement. The enhancement is evidenced by recording chemically resolved fluid mixing through a complex 3D microfluidic device at 500 frames per second, the highest recorded in a magnetic resonance imaging experiment. The key to this development is combining remote detection with a time \&$\#$39;slicing\&$\#$39; of its spatially encoded counterpart. Remote detection circumvents the problem of insensitive direct MR detection on a microfluidic device where the direct sensitivity is less than 10(-5) relative to traditional NMR, while the time slicing eliminates the constraints of the limited observation time by converting the time variable into a spatial variable through the use of magnetic field gradients. This method has implications for observing fast processes, Such as fluid mixing, rapid binding, and certain classes of chemical reactions with sub millisecond time resolution and as a new modality for on-chip chromatography. Published by Elsevier Inc.

}, keywords = {probes}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2008.04.037}, url = {://WOS:000258357600005}, author = {Harel, E. 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 {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 {300, title = {Solid-state NMR structural studies of the fibril form of a mutant mouse prion peptide PrP89-143(P101L)}, journal = {Solid State Nuclear Magnetic Resonance}, volume = {29}, year = {2006}, note = {Solid State Nucl Mag999VATimes Cited:22Cited References Count:34}, month = {Feb}, pages = {183-190}, abstract = {

The peptide fragment 89-143 of the prion protein (carrying a P101L mutation) is biologically active in transgenic mice when in a fibrillar form. Injection of these fibrils into transgenic mice (expressing full length PrP with the P101L mutation) induces a neurodegenerative prion disease (Kaneko et al., J. Mol. Biol. 295 (2000) 997). Here we present solid-state NMR studies of PrP89-143(P101L) fibrils, probing the conformation of residues in the hydrophobic segment 112-124 with chemical shifts. The conformations of glycine residues were analyzed using doubly C-13 = 0 labeled peptides by two-dimensional (2D) double-quantum correlation, and double-quantum filtered dephasing distance measurements. MQ-NMR experiments were carried out to probe the relative alignment of the individual peptides fibrils. These NMR studies indicate that the 112-124 segment adopts an extended beta-sheet conformation, though not in a parallel, in register alignment. There is evidence for conformational variability at Gly 113. DQ correlation experiments provide useful information in regions with conformational heterogeneity. (c) 2005 Elsevier Inc. All rights reserved.

}, keywords = {identification}, isbn = {0926-2040}, doi = {Doi 10.1016/J.Ssnmr.2005.09.017}, url = {://WOS:000234417500020}, author = {Lim, K. H. and Nguyen, T. N. and Damo, S. M. and Mazur, T. and Ball, H. L. and Prusiner, S. B. and Pines, A. and Wemmer, D. E.} } @article {301, title = {Spectrally resolved magnetic resonance imaging of a xenon biosensor}, journal = {Angewandte Chemie-International Edition}, volume = {45}, year = {2006}, note = {Angew Chem Int Edit997CZTimes Cited:48Cited References Count:14}, pages = {70-73}, keywords = {delivery}, isbn = {1433-7851}, doi = {Doi 10.1002/Anie.200502693}, url = {://WOS:000234223900007}, author = {Hilty, C. and Lowery, T. J. and Wemmer, D. E. and Pines, A.} } @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 {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 {323, title = {Self-diffusion measurements with chemical shift resolution in inhomogeneous magnetic fields}, journal = {Journal of Magnetic Resonance}, volume = {168}, year = {2004}, note = {J Magn Reson814XETimes Cited:5Cited References Count:27}, month = {May}, pages = {31-35}, abstract = {

A methodology for chemical shift resolved molecular self-diffusion measurements in time-independent static and radiofrequency field gradients is demonstrated. Diffusion encoding is provided by a stimulated echo Sequence with additional z-storage that allows for a change of diffusion time Without affecting the relaxation weighting. The signal is acquired stroboscopically between the pulses of a train of adiabatic double passages that induces a z-rotation Counteracting the phase spread resulting from precession in the inhomogeneous static field. as demonstrated in recent approaches to the goal of high-resolution \"ex situ\" NMR. Simulations of the pulse sequence show that the acquired signal results from the desired coherence pathway. Successful demonstrations of the experiment were performed on a Mixture of water and isopropanol. Published by Elsevier Inc.

}, keywords = {excitation}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2004.01.018}, url = {://WOS:000221006600004}, author = {Topgaard, D. and Pines, A.} } @article {324, title = {"Shim pulses" for NMR spectroscopy and imaging}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {101}, year = {2004}, note = {P Natl Acad Sci USA882PTTimes Cited:38Cited References Count:16}, month = {Dec 21}, pages = {17576-17581}, abstract = {

A way to use adiabatic radiofrequency pulses and modulated magnetic-field gradient pulses, together constituting a \"shim pulse,\" for NMR spectroscopy and imaging is demonstrated. These pulses capitalize on phase shifts derived from probe gradient coils to compensate for nonlinear intrinsic main magnetic field homogeneity for spectroscopy, as well as for deviations from linear gradients for imaging. This approach opens up the possibility of exploiting cheaper, less-than-perfect magnets and gradient coils for NMR applications.

}, keywords = {acquisition}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0408296102}, url = {://WOS:000225951500004}, author = {Topgaard, D. and Martin, R. W. and Sakellariou, D. and Meriles, C. A. and Pines, A.} } @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 {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 {360, title = {Sensitivity enhancement in multiple-quantum NMR experiments with CPMG detection}, journal = {Journal of Magnetic Resonance}, volume = {157}, year = {2002}, note = {J Magn Reson589DHTimes Cited:12Cited References Count:12}, month = {Jul}, pages = {160-162}, abstract = {

We present a modified multiple-quantum (MQ) experiment, which implements the Carr-Purcell-Meiboom-Gill (CPMG) detection scheme in the static MQ NMR experiment proposed by W. S. Warren et al. (1980, J. Chem. Phys. 73, 2084-2099) and exploited further by O. N. Antzutkin and R. Tycko (1999, J. Chem. Phys. 110, 2749-2752). It is demonstrated that a significant enhancement in the sensitivity can be achieved by acquiring echo trains in the MQ experiments for static powder samples. The modified scheme employing the CPMG detection was superior to the original MQ experiment, in particular for the carbonyl carbon with a very large chemical shift anisotropy. (C) 2002 Elsevier Science (USA).

}, keywords = {dynamics}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.2002.2578}, url = {://WOS:000177742400019}, author = {Lim, K. H. and Nguyen, T. and Mazur, T. and Wemmer, D. E. and Pines, A.} } @article {368, title = {"Shining Light" on NMR and MRI in porous materials}, journal = {Magnetic Resonance Imaging}, volume = {19}, year = {2001}, note = {Magn Reson Imaging455YUTimes Cited:1Cited References Count:0}, month = {Apr-May}, pages = {307-309}, isbn = {0730-725X}, doi = {Doi 10.1016/S0730-725x(01)00241-7}, url = {://WOS:000170056000005}, author = {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 {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 {391, title = {Scalar and anisotropic J interactions in undoped InP: A triple-resonance NMR study}, journal = {Physical Review B}, volume = {58}, year = {1998}, note = {Phys Rev B125HUTimes Cited:29Cited References Count:40}, month = {Oct 1}, pages = {8627-8633}, abstract = {

The heteronuclear J-coupling tensor between nearest neighbor P-31 and In-113 spins in undoped InP is investigated by means of In-113--\>P-31 polarization transfer under rapid magic angle spinning (MAS). The scalar contribution can be measured directly and is found to have the value \J(iso)(P-31-In-113,In-115)\ = (225+/-10) Hz. The principal value of the traceless anisotropic J-coupling tensor (pseudodipolar coupling) is determined to be J(aniso)(P-31-In-113,In-115)= 2/3[J(parallel to)(P-31-In-113,In-115)-J(perpendicular to)(P-31-In-113,In-115)] = (813+/-50) or (1733+/-50) Hz, assuming axial symmetry with the principal axis parallel to the In-P bond. Our values deviate from those reported previously [M. Engelsberg and R. E. Norberg, Phys. Rev. B 5, 3395 (1972)] [based on a moment analysis of the P-31 resonance \J(iso)(31P-In-113,In-115)\ = 350 Hz and J(aniso)(P-31-In-113,In-115) = 1273 Hz], but confirm the postulate that the nearest neighbor P-31-In-113,In-115 magnetic dipolar and pseudodipolar interactions are of the same order of magnitude and partially cancel each other.

}, keywords = {solids}, isbn = {0163-1829}, doi = {Doi 10.1103/Physrevb.58.8627}, url = {://WOS:000076232100075}, author = {Tomaselli, M. and deGraw, D. and Yarger, J. L. and Augustine, M. P. and Pines, A.} } @article {403, title = {Surface NMR using laser-polarized (129)Xe under magic angle spinning conditions}, journal = {Journal of Magnetic Resonance}, volume = {130}, year = {1998}, note = {J Magn ResonZc833Times Cited:46Cited References Count:21}, month = {Jan}, pages = {145-148}, abstract = {

NMR signals of surface nuclei of solids may be enhanced by the transfer of spin polarization from laser-polarized noble gases. Until now such experiments have not been feasible under conditions of magic angle spinning. In the present contribution it is shown that laser-polarized (129)Xe can be inserted into a spinning rotor under continuous-flow conditions using helium as a carrier gas. Effective adsorption of xenon on the sample occurs at temperatures of about 163-173 K making possible the observation of a spin polarization induced nuclear Overhauser effect (SPINOE) from the laser-polarized (129)Xe to surface (1)H nuclei of SiO(2) (AEROSIL300). This technique opens the way to selectively enhanced high-resolution multinuclear surface NMR experiments. (C) 1998 Academic Press.

}, keywords = {flow}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.1997.1296}, url = {://WOS:000072622700022}, author = {Brunner, E. and Seydoux, R. and Haake, M. and Pines, A. and Reimer, J. A.} } @article {395, title = {Surface selective H-1/Si-29 CP NMR by NOE enhancement from laser polarized xenon}, journal = {Journal of Magnetic Resonance}, volume = {133}, year = {1998}, note = {J Magn Reson116WNTimes Cited:27Cited References Count:20}, month = {Aug}, pages = {299-303}, abstract = {

The surface proton spin polarization created by the spin-polarization-induced nuclear Overhauser effect from optically polarized xenon can be transferred in a subsequent step by solid-state cross polarization to another nuclear spin species such as Si-29. The technique exploits the dipolar interactions of xenon nuclear spins with high gamma nuclei such as H-1, and is experimentally simpler than direct polarization transfer from Xe-129 to heteronuclei such as C-13 and Si-29. (C) 1998 Academic Press.

}, keywords = {spins}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.1998.1447}, url = {://WOS:000075748200008}, author = {Pietrass, T. and Seydoux, R. and Pines, A.} } @article {409, title = {Selective enhancement of NMR signals for alpha-cyclodextrin with laser-polarized xenon}, journal = {Angewandte Chemie-International Edition in English}, volume = {36}, year = {1997}, note = {Angew Chem Int EditYh944Times Cited:48Cited References Count:29}, month = {Nov 14}, pages = {2368-2370}, keywords = {solids}, isbn = {0570-0833}, doi = {Doi 10.1002/Anie.199723681}, url = {://WOS:A1997YH94400025}, author = {Song, Y. Q. and Goodson, B. M. and Taylor, R. E. and Laws, D. D. and Navon, G. and Pines, A.} } @article {414, title = {Spin dynamics in dipole-coupled molecular systems}, journal = {Abstracts of Papers of the American Chemical Society}, volume = {214}, year = {1997}, note = {Abstr Pap Am Chem SPart 2Xq859Times Cited:0Cited References Count:0}, month = {Sep 7}, pages = {22-PHYS}, isbn = {0065-7727}, url = {://WOS:A1997XQ85900540}, author = {Lin, Y. Y. and Pines, A.} } @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 {419, title = {Surface-enhanced NMR using continuous-flow laser-polarized xenon}, journal = {Journal of the American Chemical Society}, volume = {119}, year = {1997}, note = {J Am Chem SocYk502Times Cited:66Cited References Count:16}, month = {Dec 3}, pages = {11711-11712}, keywords = {solids}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja9713587}, url = {://WOS:A1997YK50200029}, author = {Haake, M. and Pines, A. and Reimer, J. A. and Seydoux, R.} } @article {431, title = {Second-order recoupling of chemical-shielding and dipolar-coupling tensors under spin decoupling in solid-state NMR}, journal = {Journal of Chemical Physics}, volume = {105}, year = {1996}, note = {J Chem PhysVd768Times Cited:55Cited References Count:53}, month = {Sep 1}, pages = {3387-3397}, abstract = {

The source of the residual line broadening in continuous-wave (cw) decoupled spectra under magic-angle sample spinning conditions is reexamined. It is shown that an important contribution to the line broadening comes from a second-order recoupling of the heteronuclear dipolar-coupling tensor and the chemical-shielding tensor of the irradiated spin. Such an interference between the two tensors leads to a sum of a zeroth-rank, a second-rank, and a fourth-rank tensor component in the Hamiltonian. The zeroth-rank and the fourth-rank tensor components are not averaged out under magic-angle sample spinning (MAS) conditions, requiring the use of higher-order averaging such as double rotation (DOR) for obtaining narrow lines. This broadening is distinctly different from off-resonance decoupling effects which transform as a second-rank tensor and can be averaged out by MAS. The properties of this second-order recoupling as a source of structural information are explored, and the conditions for removing the broadening in systems with weak homonuclear dipolar-coupling networks are discussed. (C) 1996 American Institute of Physics.

}, keywords = {waltz-16}, isbn = {0021-9606}, doi = {Doi 10.1063/1.472224}, url = {://WOS:A1996VD76800005}, author = {Ernst, M. and Bush, S. and Kolbert, A. C. and Pines, A.} } @article {425, title = {Si-29 high resolution solid state nuclear magnetic resonance spectroscopy of porous silicon}, journal = {Journal of Non-Crystalline Solids}, volume = {202}, year = {1996}, note = {J Non-Cryst SolidsVe406Times Cited:13Cited References Count:33}, month = {Jul}, pages = {68-76}, abstract = {

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

}, keywords = {dipolar}, isbn = {0022-3093}, doi = {Doi 10.1016/0022-3093(96)00144-5}, url = {://WOS:A1996VE40600008}, author = {Pietrass, T. and Bifone, A. and Roth, R. D. and Koch, V. P. and Alivisatos, A. P. and Pines, A.} } @booklet {423, title = {Solid-State NMR: Some Personal Recollections}, journal = {Encyclopedia of Nuclear Magnetic Resonance - Historical Perspectives}, volume = {1}, year = {1996}, pages = {533-540}, publisher = {John Wiley \& Sons}, author = {Pines, A.}, editor = {Harris, D.M. Grant and R.K.} } @article {429, title = {Solid-state NMR studies of the prion protein H1 fragment}, journal = {Protein Science}, volume = {5}, year = {1996}, note = {Protein SciVa138Times Cited:74Cited References Count:53}, month = {Aug}, pages = {1655-1661}, abstract = {

Conformational changes in the prion protein (PrP) seem to be responsible for prion diseases. We have used conformation-dependent chemical-shift measurements and rotational-resonance distance measurements to analyze the conformation of solid-state peptides lacking long-range order, corresponding to a region of PrP designated H1. This region is predicted to undergo a transformation of secondary structure in generating the infectious form of the protein. Solid-state NMR spectra of specifically C-13-enrrched samples of H1, residues 109-122 (MKHMAGAAAAGAVV) of Syrian hamster PrP, have been acquired under cross-polarization and magic-angle spinning conditions. Samples lyophilized from 50\% acetonitrile/50\% water show chemical shifts characteristic of a beta-sheet conformation in the region corresponding to residues 112-121, whereas samples lyophilized from hexafluoroisopropanol display shifts indicative of alpha-helical secondary structure in the region corresponding to residues 113-117. Complete conversion to the helical conformation was not observed and conversion from alpha-helix back to beta-sheet, as inferred from the solid-state NMR spectra, occurred when samples were exposed to water. Rotational-resonance experiments were performed on seven doubly C-13-labeled H1 samples dried from water. Measured distances suggest that the peptide is in an extended, possibly beta-strand, conformation. These results are consistent with the experimental observation that PrP can exist in different conformational states and with structural predictions based on biological data and theoretical modeling that suggest that H1 may play a key role in the conformational transition involved in the development of prion diseases.

}, keywords = {alpha-helices}, isbn = {0961-8368}, url = {://WOS:A1996VA13800019}, author = {Heller, J. and Kolbert, A. C. and Larsen, R. and Ernst, M. and Bekker, T. and Baldwin, M. and Prusiner, S. B. and Pines, A. and Wemmer, D. E.} } @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 {452, title = {Solid-State O-17 Magic-Angle and Dynamic-Angle Spinning Nmr-Study of the Sio2 Polymorph Coesite}, journal = {Journal of Physical Chemistry}, volume = {99}, year = {1995}, note = {J Phys Chem-UsRn706Times Cited:95Cited References Count:41}, month = {Aug 10}, pages = {12341-12348}, abstract = {

Five distinctly resolved O-17 solid-state NMR resonances in room temperature coesite, an SiO2 polymorph, have been observed and assigned using dynamic-angle spinning (DAS) at 11.7 T along with magic-angle spinning (MAS) spectra at 9.4 and 11.7 T. The O-17 quadrupolar parameters for each of the five oxygen environments in coesite are correlated with the Si-O-Si bridging bond angles determined by diffraction experiments. The sign of e(2)qQ/h along with the orientation of the electric field gradient for oxygen in the Si-O-Si linkage were determined from a Townes-Dailey analysis of the data.

}, keywords = {oxygen}, isbn = {0022-3654}, doi = {Doi 10.1021/J100032a045}, url = {://WOS:A1995RN70600045}, author = {Grandinetti, P. J. and Baltisberger, J. H. and Farnan, I. and Stebbins, J. F. and Werner, U. and Pines, A.} } @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 {455, title = {SQUID-NQR of N-14}, journal = {NQI Newsletter}, volume = {3}, year = {1994}, pages = {24-25}, author = {Ziegeweid, M. and Werner, U. and Black, B. and Pines, A.} } @article {477, title = {Side-Band Patterns in Dynamic-Angle-Spinning Nmr}, journal = {Journal of Magnetic Resonance Series A}, volume = {102}, year = {1993}, note = {J Magn Reson Ser AKz480Times Cited:19Cited References Count:26}, month = {Apr}, pages = {195-204}, keywords = {samples}, isbn = {1064-1858}, doi = {Doi 10.1006/Jmra.1993.1091}, url = {://WOS:A1993KZ48000011}, author = {Grandinetti, P. J. and Lee, Y. K. and Baltisberger, J. H. and Sun, B. Q. and Pines, A.} } @article {474, title = {Spin-Polarized Xe-129 Nmr-Study of a Polymer Surface}, journal = {Journal of Physical Chemistry}, volume = {97}, year = {1993}, note = {J Phys Chem-UsKp603Times Cited:51Cited References Count:48}, month = {Feb 25}, pages = {1649-1655}, abstract = {

A method for NMR studies of low surface area materials using optically pumped xenon gas is described. The method has been used to investigate spin-polarized xenon adsorbed onto poly(acrylic acid). The temperature dependence of the xenon-surface interaction, as measured by the xenon chemical shifts extrapolated to zero pressure, is shown to be consistent with a simple model of chemical exchange between the gas and adsorbed phases. The magnitude of the surface contribution to the Xe-129 chemical shift indicates a relatively strong interaction between xenon and poly(acrylic acid), possibly due to the polar carboxylic acid functional groups at the polymer surface. From the pressure dependence of the Xe-129 shift, the diffusion coefficient of xenon on poly(acrylic acid) is estimated to be 3.3 x 10(-5) cm2/s.

}, keywords = {temperature}, isbn = {0022-3654}, doi = {Doi 10.1021/J100110a029}, url = {://WOS:A1993KP60300029}, author = {Raftery, D. and Reven, L. and Long, H. and Pines, A. and Tang, P. and Reimer, J. A.} } @article {483, title = {Squid-Nmr Study of Methyl Quantum Tunneling in a Series of Carboxylic-Acids}, journal = {Chemical Physics Letters}, volume = {201}, year = {1993}, note = {Chem Phys LettKf754Times Cited:12Cited References Count:23}, month = {Jan 8}, pages = {550-554}, abstract = {

Quantum tunneling frequencies of methyl groups at low temperature can be measured directly by low-field nuclear magnetic resonance (NMR) using our dc-SQUID (superconducting quantum interference device) spectrometer. From NMR spectra recorded in magnetic fields below 20 mT, tunneling frequencies between 140 and 250 kHz were measured for a homologous series of carboxylic acids at 4.2 K. For solids with equivalent crystal structures, we observe an exponential correlation between the tunneling frequency and the enthalpy of fusion; from this correlation we obtain information about the contribution of intermolecular interactions to the energy barrier for methyl rotation.

}, keywords = {nuclear}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(93)85115-5}, url = {://WOS:A1993KF75400026}, author = {Black, B. and Majer, G. and Pines, A.} } @article {471, title = {Squid-Nqr of N-14 in Amino-Acids and Small Peptides}, journal = {Chemical Physics Letters}, volume = {209}, year = {1993}, note = {Chem Phys LettLh246Times Cited:7Cited References Count:13}, month = {Jun 25}, pages = {17-21}, abstract = {

We present a technique for the study of nuclear quadrupole resonance of N-14 interacting with low electric field gradients as found, for example, in amino acids. A superconducting quantum interference device (SQUID) is used to detect directly small NMR signals via cross relaxation of the N-14 polarization to adjacent proton spins, eliminating the need for field cycling. When one nitrogen quadrupolar transition matches the proton Zeeman splitting, the remaining two quadrupolar transitions can be observed by sweeping a saturating rf field through resonance. In addition, signal enhancement by simultaneous excitation of two nitro n resonances helps to identify connected transitions.

}, keywords = {resonance}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(93)87194-8}, url = {://WOS:A1993LH24600003}, author = {Werner, U. and Black, B. and Ziegeweid, M. and Pines, A.} } @article {485, title = {Sidebands in dynamic angle spinning (DAS) and double rotation (DOR) NMR}, journal = {Solid State Nuclear Magnetic Resonance}, volume = {1}, year = {1992}, note = {Solid State Nucl MagV26htTimes Cited:63Cited References Count:29}, month = {Dec}, pages = {267-295}, abstract = {

A theory of dynamic angle spinning (DAS) and double rotation (DOR) NMR is described using average Hamiltonian and irreducible tensor methods. Sideband intensities in DAS and DOR spectra are analyzed by both the moment and Bessel function methods, and general formulae are derived. Results show that the DAS moments depend on the relative rotor phase between the first and the second evolution periods, whereas the second and third DOR moments are independent of the relative phase between the inner and outer rotors. Sideband intensities in DAS spectra also depend on the relative rotor phases between evolution at the first and second angles, as well as on the ratio of time spent at each angle. Sideband intensities and phases in DOR spectra are related to the relative rotor phases between the inner and outer rotors, and the sideband pattern is determined by the ratio of the inner and outer rotor spinning speeds. An inversion symmetry of the odd numbered DOR sidebands at the relative rotor phase gamma(r) = 0 degrees. 180 degrees permits the elimination of these sidebands. Finally, numerical simulations are implemented and shown to agree with experimental results. Quadrupolar parameters can therefore be recovered either by calculating the second and third moments or by simulating the sideband intensities and phases.

}, keywords = {central transition}, isbn = {0926-2040}, doi = {Doi 10.1016/0926-2040(92)90047-D}, url = {://WOS:000208537400006}, author = {Sun, B. Q. and Baltisberger, J. H. and Wu, Y. and Samoson, A. and Pines, A.} } @article {488, title = {Solid-state Al-27 NMR studies of aluminophosphate molecular sieves}, journal = {Solid State Nuclear Magnetic Resonance}, volume = {1}, year = {1992}, note = {Solid State Nucl MagV26hsTimes Cited:12Cited References Count:33}, month = {Nov}, pages = {217-225}, abstract = {Solid-state Al-27 NMR spectra of several aluminophosphate molecular sieves have been recorded with conventional magic-angle spinning (MAS), double-rotation (DOR) and quadrupole nutation with fast MAS. Enhanced resolution was obtained in the quadrupole nutation experiment at certain radiofrequency pulse strengths. This extra resolution can be comparable to that attainable using DOR, and does not introduce spinning sidebands.}, keywords = {double-rotation}, isbn = {0926-2040}, url = {://WOS:000208537300007}, author = {Rocha, J. and Klinowski, J. and Barrie, P. J. and Jelinek, R. and Pines, A.} } @article {490, title = {Solid-State Nmr - Some Personal Recollections}, journal = {Israel Journal of Chemistry}, volume = {32}, year = {1992}, note = {Israel J ChemKt517Times Cited:1Cited References Count:0}, pages = {137-144}, isbn = {0021-2148}, url = {://WOS:A1992KT51700003}, author = {Pines, A.} } @article {493, title = {A study of nanostructure assemblies and guest-host interactions in sodium zeolite-Y using Na-23 double rotation NMR}, journal = {Nanotechnology}, year = {1992}, pages = {182-186}, author = {Jelinek, R. and Pines, A. and Ozkar, S. and Ozin, G.A.} } @article {507, title = {Scaling and Time-Reversal of Spin Couplings in Zero-Field Nmr}, journal = {Physical Review Letters}, volume = {67}, year = {1991}, note = {Phys Rev LettGj319Times Cited:13Cited References Count:25}, month = {Oct 7}, pages = {1989-1992}, abstract = {

We report the observation of spin echoes resulting from the time reversal of isotropic many-body spin couplings in zero-field NMR. The coherent-averaging pulse sequences responsible for the scaling and the time reversal of isotropic interactions of first and second rank are based on cubic and icosahedral symmetry.

}, keywords = {nqr}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.67.1989}, url = {://WOS:A1991GJ31900014}, author = {Llor, A. and Olejniczak, Z. and Sachleben, J. 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 {516, title = {A suggestion for detecting rotational tunnelling of CD3: Groups by mulitple quantum spectroscopy}, journal = {Bulletin of Magnetic Resonance}, volume = {12}, year = {1990}, pages = {9-14}, author = {Werner, U. and Muller-Warmuth, W. and Pines, A.} } @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 {550, title = {Suppression of the Zero Frequency Peak in Zero-Field Nmr}, journal = {Chemical Physics Letters}, volume = {158}, year = {1989}, note = {Chem Phys LettAb503Times Cited:1Cited References Count:22}, month = {Jun 9}, pages = {325-328}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(89)87345-2}, url = {://WOS:A1989AB50300029}, author = {Jarvie, T. P. and Takegoshi, K. and Suter, D. and Pines, A. and Zax, D. B.} } @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. 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