Nuclear Magnetic Resonance Solvent Relaxation in Concentrated Polymer Solutions

1977 ◽  
Vol 10 (2) ◽  
pp. 375-377 ◽  
Author(s):  
J. E. Anderson ◽  
H. Sillescu ◽  
S. Subramanian
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Polymer Solutions ◽  
Solvent Relaxation ◽  
Nuclear Magnetic

Mobility of Phosphorescent Solutes in Polymethylmethacrylate

1971 ◽  
Vol 49 (3) ◽  
pp. 515-519 ◽  
Author(s):  
R. J. Woods ◽  
J. F. Manville
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Methyl Methacrylate ◽  
Room Temperature ◽  
Polymer Solutions ◽  
Significant Proportion ◽  
Nuclear Magnetic

Nuclear magnetic resonance measurements upon polymerizing methyl methacrylate solutions show that a significant proportion of the solute molecules (naphthalene, phenanthrene) remain untrapped when the material becomes solid (60–30% residual unsaturation), complete rigid trapping of the solute occurring only as the unsaturation present is reduced to near zero.Phosphorescence measurements show increasing phosphorescence from solid polymethylmethacrylate containing phenanthrene as the residual unsaturation in the polymer is reduced from about 4% to zero, which is attributed to the gradual immobilization of an increasing fraction of the solute molecules as the unsaturation is reduced. Methyl isobutyrate reduces the phosphorescence from solutions of phenanthrene in polymethylmethacrylate at room temperature, but polymer solutions containing methyl isobutyrate and those containing residual unsaturation phosphoresce strongly at 77 °K.

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

Nuclear magnetic resonance microscopy

1989 ◽  
Vol 47 ◽  
pp. 828-829
Author(s):  
Paul C. Lauterbur
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Fields ◽  
Signal To Noise ◽  
Field Gradients ◽  
Useful Signal ◽  
Magnetic Field Gradients ◽  
Observation Times ◽  
Nuclear Magnetic

Nuclear magnetic resonance imaging can reach microscopic resolution, as was noted many years ago, but the first serious attempt to explore the limits of the possibilities was made by Hedges. Resolution is ultimately limited under most circumstances by the signal-to-noise ratio, which is greater for small radio receiver coils, high magnetic fields and long observation times. The strongest signals in biological applications are obtained from water protons; for the usual magnetic fields used in NMR experiments (2-14 tesla), receiver coils of one to several millimeters in diameter, and observation times of a number of minutes, the volume resolution will be limited to a few hundred or thousand cubic micrometers. The proportions of voxels may be freely chosen within wide limits by varying the details of the imaging procedure. For isotropic resolution, therefore, objects of the order of (10μm) may be distinguished.Because the spatial coordinates are encoded by magnetic field gradients, the NMR resonance frequency differences, which determine the potential spatial resolution, may be made very large. As noted above, however, the corresponding volumes may become too small to give useful signal-to-noise ratios. In the presence of magnetic field gradients there will also be a loss of signal strength and resolution because molecular diffusion causes the coherence of the NMR signal to decay more rapidly than it otherwise would. This phenomenon is especially important in microscopic imaging.

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