Spin interactions convention

There exists meanwhile a variety of frequency selective experiments still using the conventional CW irradiation as the ID NOE experiment, or upgraded with one or more selective pulses, as the ID TOCSY or the ID COSY experiment. These experiments and their many variants are probably the best choice in such cases as long as the response of a spin system to the perturbation of only one single spin or one single group of equivalent spins is of interest. If, however, and this is the most common situation, informations on several rather than only one spin-spin interaction is needed. 

Nuclear magnetic resonance (NMR) has been used to determine electrical properties in a conventional setup [23], but recently, applied electric fields have been incorporated for the determination of properties [24, 25]. Polar liquids and solutions of polar molecules align when a strong electric field (about 300 kV/cm) is applied. The anisotropic spin interactions essentially modify the NMR spectrum, and determinations of the lowest order dipole polarizability can be made. To low order, the interaction energy may be taken to be... 

The analysis of the solid-state NMR spectra of polymers begins with an examination of the heteronuclear dipolar coupling. The heteronuclear dipolar coupling arises from an interaction between the nuclear magnetic moments of two different nuclear spins. (By convention, nuclear spins are labeled as I for abundant spins, for example, that of the proton, and S for rare spins such as that of C or N nuclei.) In an external magnetic field, the Zeeman interaction describes the energy of the spin I based on its orientation, either parallel (spin up, t) or antiparallel (spin... 

This angular dependence is different from the first-order perturbations so that the conventional teclmique of removing linebroadening in solids, MAS (see below), caimot completely remove this interaction at the same time as removing the first-order broadening. Flence, the resolution of MAS spectra from quadnipolar nuclei is usually worse than for spin-2 nuclei and often characteristic lineshapes are observed. If this is the case, it is... 

When the length scale approaches molecular dimensions, the inner spinning" of molecules will contribute to the lubrication performance. It should be borne in mind that it is not considered in the conventional theory of lubrication. The continuum fluid theories with microstructure were studied in the early 1960s by Stokes [22]. Two concepts were introduced couple stress and microstructure. The notion of couple stress stems from the assumption that the mechanical interaction between two parts of one body is composed of a force distribution and a moment distribution. And the microstructure is a kinematic one. The velocity field is no longer sufficient to determine the kinematic parameters the spin tensor and vorticity will appear. One simplified model of polar fluids is the micropolar theory, which assumes that the fluid particles are rigid and randomly ordered in viscous media. Thus, the viscous action, the effect of couple stress, and... 

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