New high dielectric constant materials for tailoring the B1+ distribution at high magnetic fields
Publication year: 2010Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 11 January 2010
K., Haines , N.B., Smith , A.G., Webb
The spatial distribution of electromagnetic fields within the human body can be tailored using external dielectric materials. Here, we introduce a new material with high dielectric constant, and also low background MRI signal. The material is based upon metal titanates, which can be made into a geometrically-formable suspension in deionized water. The material properties of the suspension are characterized from 100-400 MHz. Results obtained at 7 Tesla show a significant increase in image intensity in areas such as the temporal lobe and base of the brain with the new material placed around the head, and improved performance compared to purely water-based gels.
Solid–State NMR Calculations for Metal Oxides and Gallates: Shielding and Quadrupolar Parameters for Perovskites and Related Phases
Publication year: 2010Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 13 January 2010
Derek S., Middlemiss , Frédéric, Blanc , Chris J., Pickard , Clare P., Grey
The NMR parameters obtained from solid–state DFT calculations within the GIPAW approach for 17O and 69/71Ga sites in a range of predominantly oxide–based (group II monoxides, SrTiO3, BaZrO3, BaSnO3, BaTiO3, LaAlO3, LaGaO3, SrZrO3, MgSiO3 and Ba2In2O5), and gallate (a– and b–Ga2O3, LiGaO2, NaGaO2, GaPO4, LaGaO3) materials are compared with experimental values, with a view to the future application of a similar approach to doped phases of interest as candidate intermediate temperature solid oxide fuel cell (ITSOFC) electrolytes. Isotropic– and anisotropic chemical shift parameters, quadrupolar coupling constants, and associated asymmetries are presented and analysed. The unusual GaO5 site occurring in LaGaGe2O7 is also fully characterised. In general, it is found that the theoretical results closely track the experimental trends, though some deviations are identified and discussed, particularly in regard to quadrupolar ηQ–values. The high quality of the computed results suggests that this approach can be extended to study more complex and disordered phases.
1H-Detected 1H−1H Correlation Spectroscopy of a Stereo-Array Isotope Labeled Amino Acid under Fast Magic-Angle Spinning
Publication year: 2010Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 15 January 2010
Hiroki, Takahashi , Masatsune, Kainosho , Hideo, Akutsu , Toshimichi, Fujiwara
The combined use of selective deuteration, stereo-array isotope labeling (SAIL), and fast magic-angle spinning effectively suppresses the 1H−1H dipolar couplings in organic solids. This method provided the high-field 1H-NMR linewidths comparable to those achieved by combined rotation and multiple-pulse spectroscopy. This technique was applied to two-dimensional 1H-detected 1H−1H polarization transfer CHH experiments of valine. The signal sensitivity for the 1H-detected CHH experiments was greater than that for the 13C-detected 1H−1H polarization transfer experiments by a factor of 2-4. We obtained the 1H−1H distances in SAIL valine by CHH experiments with an accuracy of about 0.2 Å by using a theory developed for 1H−1H polarization transfer in 13C-labeled organic compounds.
Operation of a 500 MHz high temperature superconducting NMR: Towards an NMR spectrometer operating beyond 1 GHz
Publication year: 2010Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 18 January 2010
Y. Yanagisawaa, b, H. Nakagomeb, K. Tennmeic, M. Hamadad, M. Yoshikawae, A. Otsukae, M. Hosonof, T. Kiyoshig, M. Takahashia, c, T. Yamazakia and H. Maedaa, c,
We have begun a project to develop an NMR spectrometer that operates at frequencies beyond 1 GHz (magnetic field strength in excess of 23.5T) using a high temperature superconductor (HTS) innermost coil. As the first step, we developed a 500 MHz NMR with a Bi-2223 HTS innermost coil, which was operated in external current mode. The temporal magnetic field change of the NMR magnet after the coil charge was dominated by (i) the field fluctuation due to a DC power supply and (ii) relaxation in the screening current in the HTS tape conductor; effect (i) was stabilized by the 2H field-frequency lock system, while effect (ii) decreased with time due to relaxation of the screening current induced in the HTS coil and reached 10-8(0.01ppm)/h on the 20th day after the coil charge, which was as small as the persistent current mode of the NMR magnet. The 1D 1H NMR spectra obtained by the 500 MHz LTS/HTS magnet were nearly equivalent to those obtained by the LTS NMR magnet. The 2D-NOESY, 3D-HNCO and 3D-HNCACB spectra were achieved for ubiquitin by the 500 MHz LTS/HTS magnet; their quality was closely equivalent to that achieved by a conventional LTS NMR. Based on the results of numerical simulation, the effects of screening current-induced magnetic field changes are predicted to be harmless for the 1.03GHz NMR magnet system.
Pulse sequence editing by symbolic calculation
Publication year: 2010Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 22 January 2010
Michael P., Barnett , Istvàn, Pelczer
Our apseq software package interprets commands to alter, combine and draw NMR pulse sequences that are expressed in a simple mnemonic style. The package is coded in mathematica. It can be extended to meet specialized needs.
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