Magnetic phenomena enhanced

A complementary article by Dais (Iraklion, Crete) addresses the theoretical principles underlying the phenomenon of carbon-13 nuclear magnetic relaxation, encompassing spin-lattice (Tt) and spin-spin (T2) relaxation times, the nuclear Overhauser enhancement, and their relation to the motional behavior of carbohydrates in solution. With examples broadly selected from simple sugar derivatives, oligosaccharides, and polysaccharides, the author shows how qualitative treatments have provided useful interpretations of the gross mobility of molecules in solution, but demonstrates how a quantitative approach may be of greater ultimate value. 

The nuclear Overhauser effect (NOE), which is manifested in certain changes in the intensities of NMR lines, is a consequence of magnetic dipolar relaxation. The name comes from a phenomenon predicted by Albert Overhauser in 1953, when he showed theoretically that saturating the electron magnetic resonance in a metal would cause the nuclear resonance intensity to be enhanced by a factor of the order of 103 (the ratio of "/electron/"/nucleus)- lonel Solomon later found that a similar effect occurs between two nuclei, but with a much smaller intensity enhancement—the nuclear Overhauser effect.90 Because the NOE is of great practical im-... 

The flocculating properties of resins from barium ferrite and y-iron oxide are similar. Even diough the magnetized resin is flocculated, the floes break up readily when stirred so that the particles react more rapidly than standard-sized resin beads which are 300-1200 pm in diameter (Fig. 2). The shell configuration of whisker-type resins also enhances reaction r tes. Because of the magnetic flocculation phenomenon the magnetized beads separate out much more rapidly than the unmagnetized ones (Fig. 3). 

In addition, at altitudes near 100-105 km, thin layers (1-3 km thick) of greatly enhanced metal ion densities are found to extend over horizontal areas of a few hundred kilometers. This phenomenon is called a sporadic E layer, and arises primarily from the effects of wind shears in the presence of a magnetic field, although other mechanisms have also been... 

As noted earlier, chemical shilts arise from the secondary magnetic fields produced by the circulation of electrons in the molecule. I hese so-called local diamaf nvtic currants are induced by the fixed magnetic field and result in secondary fields that may either decrease or enhance the Held to which a given proton responds. The effects arc complex, and we consider only the major aspects of the phenomenon here. More complete ireai-inonis can be found in several reference works. ... 

---