A nuclear magnetic resonance study of molecular motion in solid tris (n-propylammonium) enneachlorodiantimonate (III) (n-C3H7NH3)3Sb2Cl9

Application of LCModel for quality control and quantitative in vivo 1H MR spectroscopy by short echo time STEAM sequence

The linear combination of model spectra (LCModel) calculation of a parameter for long-term quality control, kT, was introduced, representing the ratio of the temporal and nominal intensities of CH3 groups of lactate and acetate in a quality control phantom. This procedure is a part of the quality assurance of the scanner using fully automatic measurement and calculation of kT parameters, and utilizing Shewhart regulation control charts for continuous evaluation of the magnetic resonance (MR) scanner setting. The application of the kT parameter for the correction of in vivo data increases the precision of molar concentration determination by about 4%. This was tested by the quantitative in vivo MR determination of the molar concentrations of 13 prominent metabolites (N-acetylaspartate (NAA), N-acetylaspartylglutamate, creatine and phosphocreatine (Cr), choline-containing compounds (Cho), myo-inositol, scyllo-inositol, gamma-aminobutyric acid, glutamine, glutamate, glucose, lactate, alanine, taurine) in the white matter and hippocampus of the brain in groups of volunteers, using a short echo time stimulated echo acquisition mode sequence (echo time = 10 ms) and the LCModel technique. The repeatability of the measurement of prominent metabolites such as NAA, Cr and Cho was found to be around 10% (relative standard deviation, n = 6); precision in a group of volunteers (n = 20 and 28, respectively) was in the range of approximately 13-20%. For other metabolites, which are measured with a lower signal-to-noise ratio, the precision can be much lower.

Calculation of the NMR second moment for materials with different types of internal rotation

The measurements of the NMR second moment can reveal information about structural and dynamical details of the sample providing that analysis of the experimental results on the basis of the Van Vleck's formula can be performed. In this paper the method of calculating the Van Vleck's second moment for solids with complex internal motions is presented. The method is based on simulating any desired motion of atoms within a block of unit cells large enough to reflect the property of the macroscopic sample and calculating the second moment value averaged by this motion. The detailed description of this method is given for the case of rotation of molecules or groups of atoms. The algorithm of the computer program which performs calculation based on the described method is also presented. Examples of application of the described method are listed.