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To detect white matter abnormalities in patients with mild Alzheimer disease (AD) by diffusion tensor imaging and to determine their topographic relationship with gray matter atrophy.

The rheological properties of the aqueous mixtures of cationic-anionic surfactants, both in single-phase systems and in aqueous two-phase systems, have been studied. Bizarre rheological properties —negative thixotropy, viscoelasticity and hihg viscosity of shear rate dependent at relatively low concentration — have been observed. An unusual viscosity change, that is, viscosity lowering with increasing concentration, was obtained. The negative thixotropy might be due to the existence of lamellar or sheet-like micelles, viscoelasticity might be induced by rodlike and lamellar or sheet-like micelles, the high viscosity might be a consequence of the formation of network by long rodlike micelles and the concentration-induced viscosity lowering could be interpreted in terms of the decrease of micellar dimensions with concentration.

Equimolar mixed cationic−anionic surfactants usually form a precipitate at very low concentration. However, we found that aqueous mixtures of alkyltriethylammonium bromide (CnH2n+1N(C2H5)3Br, CnNE) and sodium alkylsulfonate (CnH2n+1SO3Na, CnSO3Na) could form homogeneous solutions even at high concentration. C8,10NE−C8,10,12SO3Na mixed systems and C12,14NE−C8SO3Na mixed systems formed homogeneous solutions at any compositions in the entire concentration range studied (up to 0.2 mol·L^-1). Hydrodynamic radius Rh and polydispersity index PI of the mixed aggregates were measured by dynamic light scattering, and the effects of time, temperature, dilution, and added salt NaBr on that were studied. The mixed aggregates were observed by freeze-fracture transmission electron microscopy. The results showed that small and narrow distributed vesicles were formed in the mixed systems, and vesicle radii did not change with time, which indicates that the homogeneous solutions are stable. Besides, these mixed systems had high surface activity, and their viscosities are low.