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Nuclear magnetic resonance (NMR) spectroscopy is an important tool for studying the structures of molecules and materials. Mainly due to their high costs, the NMR spectrometers are often not available for teaching experiments. Teaching NMR experiments cannot be performed routinely and effectively also because that the students are not able to understand the principles underlying the operational steps without proper and adequate training. In this work, a virtual NMR spectrometer (VMRS1.0) for teaching experiments, which is based on numerical computational simulation technology and can be operated like a real spectrometer, is presented. With the VMRS1.0, the students can perform basic NMR experiments, including tuning, shimming, field lock, power adjustment for radio frequency, selecting samples, acquiring data, fast Fourier transform and spectrum processing (i.e., phase correction, integration, chemical shift correction, auto peak finding and J-coupling constant measurement). In addition to the routine one-dimensional NMR experiments, more complicated experiments such as decoupling, DEPT and HMQC can also be performed on the VMRS1.0. With the virtual NMR spectrometer developed, the students can practice their experimental skills and gain deeper understandings of the underlying principles in a more easy and cost-efficient way.

Purpose: Diffusional kurtosis imaging (DKI) measures the deviation of the displacement probability from a normal distribution, complementing the data commonly acquired by diffusion MRI. It is important to elucidate the sources of kurtosis contrast, particularly in biological tissues where microscopic kurtosis (intrinsic kurtosis) and diffusional heterogeneity may co‐exist. Methods: We have developed a technique for microscopic kurtosis MRI, dubbed microscopic diffusional kurtosis imaging (µDKI), using a symmetrized double diffusion encoding (s‐DDE) EPI sequence. We compared this newly developed µDKI to conventional DKI methods in both a triple compartment phantom and in vivo. Results: Our results showed that whereas conventional DKI and µDKI provided similar measurements in a compartment of monosphere beads, kurtosis measured by µDKI was significantly less than that measured by conventional DKI in a compartment of mixed Gaussian pools. For in vivo brain imaging, µDKI showed small yet significantly lower kurtosis measurement in regions of the cortex, CSF, and internal capsule compared to the conventional DKI approach. Conclusions: Our study showed that µDKI is less susceptible than conventional DKI to sub‐voxel diffusional heterogeneity. Our study also provided important preliminary demonstration of our technique in vivo, warranting future studies to investigate its diagnostic use in examining neurological disorders. [ABSTRACT FROM AUTHOR]

Crude oils, which are complex mixtures of hydrocarbons, can be characterized by nuclear magnetic resonance diffusion and relaxation methods to yield physical properties and chemical compositions. In particular, the field dependence, or dispersion, of T1 relaxation can be used to investigate the presence and dynamics of asphaltenes, the large molecules primarily responsible for the high viscosity in heavy crudes. However, the T2 relaxation dispersion of crude oils, which provides additional insight when measured alongside T1, has yet to be investigated systematically. Here we present the field dependence of T1-T2 correlations of several crude oils with disparate densities. While asphaltene and resin-containing crude oils exhibit significant T1 dispersion, minimal T2 dispersion is seen in all oils. This contrasting behavior between T1 and T2 cannot result from random molecular motions, and thus, we attribute our dispersion results to highly correlated molecular dynamics in asphaltene-containing crude oils., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)