Cross polarization differential

Differential cross-polarization Dipolar suppression period Calcium hydroxyapatite Calcined HA (dehydrated)... 

To acquire better structural information, one has to resort to more advanced solid-state NMR techniques. Here, they will be reviewed by subject rather than in chronological order. First, we shall briefly look at P relaxation. Second, components of the H—> P CP signal will be discussed. Third, much attention will be given to HPO detection by differential H—> P cross-polarization (DCP). Then the P sideband pattern index and chemical shift anisotropy in the study of bone calcification will be briefly reviewed. Finally, a special ADRF-CP technique will be mentioned. 

Structural function of HPO ions in bone mineral and their content are of great biological interest. Concentration of these ions decreases as bone apatite matures with age [50,51 ]. In order to analyse scarce HPO " ions in the presence of abundant PO ions, one has to resort to a special CP technique proposed by Zumbulyadis [52] and X. Wu et al. [53], and apphed to bone mineral by Y. Wu et al. [37]. The technique is a modified version of conventional CP (Fig. 14a) and is called differential cross-polarization (DCP). The proton spin-lock is divided into two periods, f and t. During the first period, polarization is transferred, as usual, from H to P. The phase of the H spin-lock pulse is then reversed, which forces polarization to transfer backwards (depolarisation), from P to H. The DCP experiment is performed with arbitrarily chosen, constant f and constant or variable t. The variable experiment begins with CP peaks of... 

Ramanathan C, Ackerman JL (1997) ADRF differential cross polarization spectroscopy of synthetic calcium phosphates and bone mineral. J Magn Reson 127 26-35... 

Fig. 13. Polar differential cross section (CM-system) for the charge transfer reaction Na + 1 - Na+ + 1. Notice the relative shift of the zero point of both curves and the multiplication factors of different parts of the curves. At the top the angular resolution of the measurements is indicated. (Delvigne and Los, 1973.)...

Fig. 15. Polar differential cross section calculated semi-classically for the charge transfer process Na + I - Na+ + I, (a) Calculation with the complete interference structure with omission of the primary rainbow. (b) Approximate semi-classical calculation taking into account only interferences from net repulsive and net attractive scattering, (c) The full bars indicate maxima observed experimentally for net attractive scattering, the dashed bars for net repulsive scattering. H12(RC) = 0-065 eV angular coupling was neglected. (Delvigne and Los, 1973.)...

Fig. 17. Elastic polar differential cross section of K + I, multiplied by 04/3, vs. t = 0 at four different energies (eV). Two distinct rainbows can be observed. (Kaufmann et al 1974a.)...

The often observed textures for Sa are the focal-conic fan texture and the homeotropic texture. When the molecular orientation is homeotropic, the optic axis is perpendicular to the film surface so that the preparation appears black (pseudoisotropic) on a crossed polarizing microscope. As with the homeotropic nematics, the homeotropic Sa phase can be differentiated from the true isotropic phase by conoscopic observations. Further more, if the cover slip of the homeotropic Sa preparation is slightly moved, the orientation is disturbed resulting in oily streaks in form of bright bands. The homeotropic Sa phase may thus be distinguished from the homeotropic nematic phase. 

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