@article {293, title = {Application of atomic magnetometry in magnetic particle detection}, journal = {Applied Physics Letters}, volume = {89}, year = {2006}, note = {Appl Phys Lett112PJTimes Cited:9Cited References Count:18}, month = {Nov 27}, abstract = {

The authors demonstrate the detection of magnetic particles carried by water in a continuous flow using an atomic magnetic gradiometer. Studies on three types of magnetic particles are presented: a single cobalt particle (diameter similar to 150 mu m, multidomain), a suspension of superparamagnetic magnetite particles (diameter similar to 1 mu m), and ferromagnetic cobalt nanoparticles (diameter similar to 10 nm). Estimated detection limits are 20 mu m diameter for a single cobalt particle at a water flow rate of 30 ml/min, 5x10(3) magnetite particles at 160 ml/min, and 50 pl for the ferromagnetic fluid of cobalt nanoparticles at 130 ml/min. Possible applications of their method are discussed.

}, keywords = {system}, isbn = {0003-6951}, doi = {Doi 10.1063/1.2400077}, url = {://WOS:000242538500151}, author = {Xu, S. and Donaldson, M. H. and Pines, A. and Rochester, S. M. and Budker, D. and Yashchuk, V. V.} } @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 {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 {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.} }