Dynamic NMR imaging

The previous two sections described the development of hp-xenon techniques for the investigation of gas dynamics in porous or opaque media. The usefulness of continuous flow hp-xenon as a tool for dynamic NMR imaging experiments was... 

It is interesting to note that several of the concepts for improving NMR technology, as listed by Levy and Craik, in 1988, already have been partially or fully achieved (1) two-dimensional Fourier transform (FT NMR) (2) high-resolution NMR in solids (3) new types of pulse sequences (4) chemically induced dynamic nuclear polarization (5) multiple quantum NMR and (6) NMR imaging (MRI). 

Dynamic NMR studies [7-10] have shown that two exchange processes occur in these complexes (i) Interconversion between the conformations of the ethylene bridges (66 AX). This process can be achieved by a rearrangement in the coordination polyhedron and is characterized by a AG/ value between 49 and 57 kj mol-1. It should be noted that the shuffle in the coordination polyhedra converts 1 and 4 into their mirror images (1 1 and 4 4 ), whereas 2 and 3 are converted into each others mirror images (2 3 and 3 2 ). (ii) A relatively slow racemization of the terminal N-atoms (AG/ = 65-71 kj mol-1), requiring decoordination of the terminal N-atoms and their pending arms. 

To complete this study we performed a dynamic experiment on the diffusion of DMP in the 10% coked pellet. It should be recalled that the kinetic diameter of the probe is 0.6 nm after heavy coking it is reasonable to think that the diameter of the hexagonal openings (0.78 nm) of the Y zeolite is seriously reduced, leading to a decrease in the rate of diffusion of the molecule in the pellet, it being possible then to study this diffusion by 1-D NMR imaging. 

Cellular Metabolites. - A review of methods for the measurement of ml has been produced with 95 references. It examines the quantitative measurement of ml by mass spectrometry and in vivo NMR. The NMR chemical shifts and /-coupling values of 35 metabolites which can be detected by in vivo or in vitro investigations of the mammalian brain have been published. The principles and recent applications of dynamic nuclear polarisation, which combines the sensitivity to oxygen of EPR and the tractability of NMR imaging, have been reviewed with 244 references. A review of studies of intermediary metabolism, including the use of NMR in the analysis of substrate selection under in vivo conditions, has been produced. A review has been produced, with 74 references, on the study of metabolic flux and subcellular transport of metabolites using NMR. " ... 

Flow Velocity, Rheometry. - Papers relating to the flow of hyperpolar-ized He or Xe gas are picked up in Sections 2 and 6 as well. Poiseuille flow in Xe gas phase was studied by dynamic NMR microscopy. The flow profile images are different for a short observation time than for a longer... 

NMR imaging was used to study the spatial distribution of molecules with chemically induced dynamic nuclear polarization. It is shown that heating of a system during the photolysis can cause a highly nonuniform distribution of reaction products due to a convective effect. 

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