Varian Associates, Inc.

Varian, Inc.

Stephen H Smallcombe

Steven L Patt

Howard D Hill

Barbara L Erwine

Paul A Keifer

Radio-frequency (RF) heating is used to accelerate the thermal equilibration of dielectrically lossy nuclear magnetic resonance (NMR) samples. High-power heating RF pulses are applied to the sample before lower-power measurement RF pulses, using any of the NMR probe coils. The heating pulses are offset in frequency relative to the measurement pulses, such that the heating pulses do not magnetically affect the spins of interest. Heating pulse sequences of decreasing power can be used to prevent the sample temperature from overshooting the desired equilibrium temperature. Heating RF pulses can pre-establish the thermal effects of both measurement-independent and measurement-dependent heating. For pre-establishing the thermal effects of measurement-dependent heating, the heating pulse transients are chosen to be proportional to subsequent measurement pulse transients.

Accelerating NMR sample thermal equilibration by RF heating

Observation of transient phenomena in an oversampled regime is implemented with a time correction obtained by prepending one or more pseudo datums to the oversampled data to constitute an effective negative delay for the oversampled data set including the pseudo datums. For an oversampling factor N and oversampling rate .omega..sub.s, a digital filter furnishes downsampled data uniformly spaced in time by N/.omega..sub.s and positioned at n (N/.omega..sub.s) where n is the discrete downsampled time coordinate.

Time correction for digital filters in transient measurments

Improved solvent suppression in NMR data is achieved using pulse sequences wherein each of a series of selective excitation pulses are followed by a magnetic gradient pulse and a delay, where the magnetic gradient pulse amplitudes monotonically decrease by a selected fraction of the preceeding gradient pulse. Decoupling a second nucleus during selective excitation pulses has been shown to be efficacious for suppression of organic solvents.

Solvent suppression method for LC-NMR and high-resolution-NMR

A vortex restraining plug for an NMR spinning sample tube which floats partially submerged in the sample and which restrains vortexing.

Method and apparatus for NMR sample tube vortex plug

An analytical instrument employing ensemble averaging to improve the signal-to-noise ratio including means for determining the most efficient scaling factor and for controlling the instrument to maintain assurance of efficient averaging.

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Redwood City, CA, United States of America

Stephen H Smallcombe