INDEX spin relaxation times

In several previous papers, the possible existence of thermal anomalies was suggested on the basis of such properties as the density of water, specific heat, viscosity, dielectric constant, transverse proton spin relaxation time, index of refraction, infrared absorption, and others. Furthermore, based on other published data, we have suggested the existence of kinks in the properties of many aqueous solutions of both electrolytes and nonelectrolytes. Thus, solubility anomalies have been demonstrated repeatedly as have anomalies in such diverse properties as partial molal volumes of the alkali halides, in specific optical rotation for a number of reducing sugars, and in some kinetic data. Anomalies have also been demonstrated in a surface and interfacial properties of aqueous systems ranging from the surface tension of pure water to interfacial tensions (such as between n-hexane or n-decane and water) and in the surface tension and surface potentials of aqueous solutions. Further, anomalies have been observed in solid-water interface properties, such as the zeta potential and other interfacial parameters. 

Chief among the interfacial properties of aqueous systems that suggest the occurrence of thermal anomalies are the following index of refraction, density, activation energy for ionic conductance, rates of surface reactions, surface tension, surface potentials, membrane potentials, heats of immersion, zeta potentials, rate of nucleation, viscous flow, ion activities, proton spin lattice relaxation times, optical rotation, ultrasonic velocity and absorption, sedimentation rates, coagulation rates, and dielectric properties. 

A chromia-alumina catalyst may contain protons both as surface hydroxyl groups and as adsorbed water, and therefore it exhibits a proton NMR spectrum. Alumina itself has been extensively studied by proton NMR, but this experimental technique has not been widely applied to the chromia-alumina system. Until recently, the nearest approach to this application was by Selwood and his co-workers 165, 166) who found that the spin-lattice relaxation time of the protons in water was modified by contacting the water with a chromia-alumina catalyst. By comparing this effect with that of Cr + ions in aqueous solution, the authors obtained a rough index of the accessibility of the ohromia, which in effect could be regarded as an approximate measure of the number of surface chromium ions. Ibers et al. 167) studied the proton NMR of HCr02. 

This phenomenon has been observed in both Newtonian and power law fluids (non-Newtonian) and is experimentally found to be closely related to polymer properties (molecular stmcrnre, molecular weight distribution, shear viscosity, relaxation time, power law index) as well as to the spinning variables, such as draw ratio, cooling rate, melt temperature, and die geometry, and so on. 

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