ABSTRACT
We describe the design and operation of a modified commercial rheometer to simultaneously perform rheological measurements and structural studies by small angle neutron scattering (SANS). The apparatus uses a Couette geometry shear cell allowing two of the three scattering planes to be observed by performing experiments in either the radial or tangential geometries. The device enables small angle neutron scattering patterns to be obtained simultaneously with a wide variety of rheological measurements such as stress/strain flow curves, oscillatory deformations, and creep, recovery and relaxation tests, from -20 °C to 150 °C, for samples with viscosities varying by several orders of magnitude. We give a brief report of recent experiments performed on a dispersion of acicular nanoparticles and biopolymer network under stress demonstrating the utility of such measurements. This device has been developed at the National Institute of Standards and Technology's Center for Neutron Research (NCNR) and made available to the complex fluids community as part of the standard sample environment equipment.
ABSTRACT
We describe a method to organize nanometer-sized hydrophilic particles into ordered arrays by templating them in the soft, micelle-crystal phases (spherical and cylindrical) of a thermoreversible block copolymer. Small-angle neutron scattering (SANS) with contrast variation is used to show that the dispersed particles (in this case, proteins or silica) form structured arrays by being constrained in the interstitial cavities between the polymer micelles in the ordered micelle crystal. Simple shear is used to macroscopically align both phases of the nanocomposites (micelles and particles) into macro-domains. The temperature-induced order-order transition between templates of spherical and cylindrical micelles is demonstrated as a reversible technique to modify the structure of the templated nanoparticle arrays.
ABSTRACT
A study of VPA based on a comparison of mean plasma levels, plasma peak latency times and plasma half-lives after rectal and oral administration was conducted in 9 children between 6 months and 10 years of age suffering from various forms of epileptic seizure, before they received chronic VPA treatment. Each child received an oral dose of 20 mg/kg and after two days a rectal dose of 20 mg/kg and the mean plasma concentrations were determined at intervals for both modes of administration. An identical plasma concentration for both after 24 h showed that the quantity of drug absorbed was the same. The mean half-life varied according to age: 11 +/- 2 h for children over 3 years of age and 9 +/- 1 h for those under 3. The results of the study, in line with the few other available published data, thus confirm the validity of rectal VPA administration.
