High-field Magnet

Quadrupole Shifts in High-Field Magnetic Spectra... 

Fig. 4.12 Surface plots of the EFG tensor as determined from the angular dependence of the first-order quadrupole shift, Eq of high-field magnetic Mossbauer spectra. The plots visualize the value of the function (3cos 0 - 1 + rysin d cos20) for > 0 and ry = 0 (a), r] = 0.3 (b), and 77 = 1 (c)...

These measurements have been demonstrated to achieve results comparable to laboratory research grade rheometers. Unfortunately, current commercially available MRI systems are almost all built around large, superconducting, high-field magnets. The costs of these systems have precluded widespread utilization of MRI based sensors in industry. 

Bill, J.C. Green, B.N. Lewis, I.A.S. A High Field Magnet With Fast Scanning Capabihties. Int. J. Mass Spectrom. Ion Phys. 1983,46, 147-150. 

Wolfender et ah, and this coupled technique is treated more comprehensively in Chapter 1. The LC-NMR technique is by nature rather insensitive however, high-field magnets and recent improvements in solvent suppression, pulse field gradients, and probe technology have made it possible to achieve useful results on various flavonoid struc-tures. The detection limit with a 60 p.1 cell in a 500 MHz instrument for a compound with a molecular weight of around 400 amu may typically be around 20 p.g, and the information provided is hitherto mainly based on NMR spectra or correlation experiments. 

This chapter recalls the principles of the hyperfine coupling between electrons and nuclei in terms of energy and deals with its consequences on chemical shift. The equations for contact and pseudocontact shifts are derived and illustrated in a pictorial way. Their physical/chemical backgrounds are discussed as well as their limits of validity. The mechanisms of spin delocalization are illustrated. The perspectives when high field magnets are used are highlighted. 

Seaquist ER, Tkac I, Damberg G, Thomas W, Gruetter R. Brain glucose concentrations in poorly controlled diabetes mellitus as measured by high-field magnetic resonance spectroscopy. Metabolism 2005, 54, 1008-1013. 

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