Fast-pulsing LED-enhanced NMR: A convenient and inexpensive approach to increase NMR sensitivity

Abstract Traditional nuclear magnetic resonance (NMR) is mainly applied to horizontal ground and one-dimensional electrical structures. However, calculations of the excitation fields rarely consider the three-dimensional electrical changes of the subsurface medium and undulating terrain, or the deformations caused by emission sources. Therefore, to analyse the influences of terrain fluctuations, emission source deformations and three-dimensional electrical changes on NMR, three-dimensional finite element forward modelling of undulating terrain NMR was conducted in this study. First, based on a scalar finite element method, the direct calculations of the excited magnetic fields of a three-dimensional electrical medium were realised, which improved calculation accuracy by avoiding the finite element calculations of magnetic vector potential and vector on the magnetic field. During the source loading process, the equivalent thin wire source of the pseudo δ function was used to load the source function directly into the equation for the purpose of achieving total field calculations. This was completed to enable the calculations to be applied to any shape of the transmitting loop and undulating terrain. Then, the components of the excitation magnetic fields perpendicular to the geomagnetic fields were calculated using the rotation matrix. Finally, the NMR sensitivity function and 3D responses were calculated. The calculations of the excitation magnetic fields were verified using a uniform half-space model. The overall algorithm was tested by the nuclear magnetic responses of the layered medium. Also, a typical undulating terrain model was adopted and the complex excitation source NMR was simulated using the algorithm proposed in this study. The algorithm provided a three-dimensional forward basis for the NMR inversion in the cases of determining the electrical medium for the subsequent undulating terrain.

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Compartmentation of metabolism probed by [2- ]alanine: improved NMR sensitivity using a CryoProbe detects evidence of a glial metabolon

Neurochemistry International ◽

10.1016/s0197-0186(02)00064-5 ◽

2003 ◽

Vol 42 (1) ◽

pp. 93-99 ◽

Cited By ~ 31

Author(s):

J.L Griffin ◽

H Keun ◽

C Richter ◽

D Moskau ◽

C Rae ◽

...

Keyword(s):

Nmr Sensitivity

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SEnD NMR: Sensitivity Enhanced n-Dimensional NMR

Journal of Magnetic Resonance ◽

10.1016/j.jmr.2009.11.005 ◽

2010 ◽

Vol 202 (2) ◽

pp. 250-258 ◽

Cited By ~ 2

Author(s):

John M. Gledhill ◽

A. Joshua Wand

Keyword(s):

Nmr Sensitivity

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17O relaxation time and NMR sensitivity of cerebral water and their field dependence

Magnetic Resonance in Medicine ◽

10.1002/mrm.1073 ◽

2001 ◽

Vol 45 (4) ◽

pp. 543-549 ◽

Cited By ~ 64

Author(s):

Xiao-Hong Zhu ◽

Hellmut Merkle ◽

Jae-Hwan Kwag ◽

Kamil Ugurbil ◽

Wei Chen

Keyword(s):

Relaxation Time ◽

Field Dependence ◽

Nmr Sensitivity

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NMR Relaxivities of Paramagnetic Lanthanide-Containing Polyoxometalates

Molecules ◽

10.3390/molecules26247481 ◽

2021 ◽

Vol 26 (24) ◽

pp. 7481

Author(s):

Aiswarya Chalikunnath Venu ◽

Rami Nasser Din ◽

Thomas Rudszuck ◽

Pierre Picchetti ◽

Papri Chakraborty ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Contrast Agents ◽

Current Trend ◽

Image Contrast ◽

Relaxation Rates ◽

Wide Range ◽

Magnetic Resonance Imaging Mri ◽

Nmr Sensitivity ◽

Applied Fields

The current trend for ultra-high-field magnetic resonance imaging (MRI) technologies opens up new routes in clinical diagnostic imaging as well as in material imaging applications. MRI selectivity is further improved by using contrast agents (CAs), which enhance the image contrast and improve specificity by the paramagnetic relaxation enhancement (PRE) mechanism. Generally, the efficacy of a CA at a given magnetic field is measured by its longitudinal and transverse relaxivities r1 and r2, i.e., the longitudinal and transverse relaxation rates T1−1 and T2−1 normalized to CA concentration. However, even though basic NMR sensitivity and resolution become better in stronger fields, r1 of classic CA generally decreases, which often causes a reduction of the image contrast. In this regard, there is a growing interest in the development of new contrast agents that would be suitable to work at higher magnetic fields. One of the strategies to increase imaging contrast at high magnetic field is to inspect other paramagnetic ions than the commonly used Gd(III)-based CAs. For lanthanides, the magnetic moment can be higher than that of the isotropic Gd(III) ion. In addition, the symmetry of electronic ground state influences the PRE properties of a compound apart from diverse correlation times. In this work, PRE of water 1H has been investigated over a wide range of magnetic fields for aqueous solutions of the lanthanide containing polyoxometalates [DyIII(H2O)4GeW11O39]5– (Dy-W11), [ErIII(H2O)3GeW11O39]5– (Er-W11) and [{ErIII(H2O)(CH3COO)(P2W17O61)}2]16− (Er2-W34) over a wide range of frequencies from 20 MHz to 1.4 GHz. Their relaxivities r1 and r2 increase with increasing applied fields. These results indicate that the three chosen POM systems are potential candidates for contrast agents, especially at high magnetic fields.

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ChemInform Abstract: POPULATION REDISTRIBUTION TO ENHANCE NMR SENSITIVITY AND ALLOW DECOUPLING OF LOW GYROMAGNETIC RATIO NUCLEI

Chemischer Informationsdienst ◽

10.1002/chin.198021048 ◽

1980 ◽

Vol 11 (21) ◽

Author(s):

P. H. BOLTON ◽

T. L. JAMES

Keyword(s):

Gyromagnetic Ratio ◽

Population Redistribution ◽

Nmr Sensitivity

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Proton and 19F NMR Spectroscopy of Pesticide Intermolecular Interactions

Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry ◽

10.1093/oso/9780195097511.003.0008 ◽

1997 ◽

Author(s):

Sharon J. Anderson

Keyword(s):

Charge Transfer ◽

Nmr Spectroscopy ◽

Intermolecular Interactions ◽

Molecular Mechanisms ◽

Solid Phase ◽

19F Nmr ◽

Fluorine Concentration ◽

Specific Interactions ◽

Partition Theory ◽

Nmr Sensitivity

Sorption of organic pollutants by soils and sediments is one of the main chemical processes that controls pollutant migration in the environment. Information about the molecular mechanisms by which an organic pollutant interacts with other solution-phase constituents and with solid-phase sorbents would be invaluable for more accurate prediction of pollutant fate and transport and for optimal design and application of remediation procedures. Many current models and remediation strategies are based upon the “partition theory” of organic compound sorption, which predicts sorption coefficients from properties such as water solubility or octanol-water partition coefficients. Partition theory is well suited for nonpolar hydrocarbons but may not be appropriate for pesticides with electrophilic or weakly acidic or basic substituents, which may interact with soils or organic matter through specific interactions such as hydrogen bonding or charge-transfer complexes. If a pesticide can form hydrogen bonds or a charge-transfer complex with a sorbent, sorption may be greater than in the absence of specific interactions. Nuclear magnetic resonance (NMR) spectroscopy is well suited for the study of pesticide-solution or pesticide-sorbent interactions because NMR is an element-specific method that is extremely sensitive to the electron density (shielding) near the nucleus of interest. Consequently, solution-state NMR can distinguish between closely related functional groups and can provide information about intermolecular interactions. All nuclei with nonzero nuclear spin quantum number can be studied by NMR spectroscopy. Of the more than 100 NMR-active nuclei, 1H and 19F are the easiest to study because both have natural abundances near 100% and greater NMR sensitivity than any other nuclei. In addition, both 1H and 19F have zero quadrupolar moments, which means that sharp, well resolved NMR peaks can be obtained, at least in homogeneous solutions. Proton NMR is well suited for elucidating molecular interactions in solution but cannot be used to study interactions between pesticides and heterogeneous sorbents such as soils, humic acid, or even cell extracts, since protons in the sorbent generally produce broad peaks that mask the NMR peaks from the solute or sorbate of interest. In contrast, 19F NMR can be used to study interactions between fluorine-containing molecules and heterogeneous sorbents because the fluorine concentration in most natural sorbents is negligible.

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